JBL w10gti & w15gtimk2

[npdang]

A very beefy looking sub, needless to say. Features JBL's unique differential drive motor. Read more about it at http://www.jblpro.com/pub/technote/JBL_TN%201-33%20rev3.pdf Definitely interesting stuff, and I highly recommend browsing through the white paper.

http://diymobileaudio.com/pics/jblw10gti/jbl1.JPG
http://diymobileaudio.com/pics/jblw10gti/jbl2.JPG
http://diymobileaudio.com/pics/jblw10gti/jbl3.JPG

This driver's pretty deep and sits at about 22cm deep. I like the cooling fins, the rugged chassis, and the venting around the driver is adequate to prevent mechanical noises. The foam gasket around the driver seems a bit cheap though on such a high end design Imho. I did like the heavy duty binding posts.

http://diymobileaudio.com/pics/jblw10gti/bl.JPG
http://diymobileaudio.com/pics/jblw10gti/cms.JPG
http://diymobileaudio.com/pics/jblw10gti/le.JPG
http://diymobileaudio.com/pics/jblw10gti/dist.JPG
http://diymobileaudio.com/pics/jblw10gti/ts.JPG

Good performance overall. Shorting rings are evident, given the very low inductance and the shape of the LE curve. This driver would be an affordable ultra low inductance alternative to the Aura drivers, as the differential drive motor is also inherently shielded. There is a rather strong offset in the CMS curve, and the BL curve while good appears to be rather unremarkable given the unique design of the motor.

Efficiency is fair for a ten, although I think the Q is a tad bit high for sealed or ported box use. These would be great drivers for those seeking strong low end sensitivity, or even for IB use. Surprisingly, peak to peak throw is a bit limited compared to the impression you are given when seeing the depth of the driver and large surround.

Here's a look at the w15gtimk2 in comparison to the 10". Sure to impress those who equate size with performance :)

http://diymobileaudio.com/pics/jbl15gti/w151.jpg
http://diymobileaudio.com/pics/jbl15gti/w152.jpg

http://diymobileaudio.com/pics/jbl15gti/w15gtibl.jpg
http://diymobileaudio.com/pics/jbl15gti/w15gticms.jpg
http://diymobileaudio.com/pics/jbl15gti/w15gtile.jpg
http://diymobileaudio.com/pics/jbl15gti/jblts.JPG

Similar performance to the 10" as well, albeit with higher inductance, better powerhandling, and a bit more throw.

[kappa546]

hmmm... i expected better. considerably

[Rbsarve]

JBL obviously knows how to build subs, but I find all these ultra-deep subs a bit stupid really. On the above woofer, how do you intergrate it into a normal car? There simply is no good way exept IB in a sedan.

Can't wait until the JL's thin subs comes to it's third generation.
(My general rule of product development: First generation stuff usually have a major design flaw, second generation usually have fixed the design flaw on the expence of performance and on the third they get it right) (Note that i haven't even seen the JL w5 except on pictures)

[300Z]

I wonder how much different the 10" is from the 12 and 15"... a while back I remember Andy said something about the VC being slightly different... and the BL curve was also different on the 12" Dumax test. :confused:
I also expected a bit better.

[bdubs767]

hmmm the newer GTI is different I have...

Rubber gasket, rubber surrond. Makes me wonder if they did anyhting else to it...

[npdang]

Hmm I thought you were gonna send it :)

[bdubs767]

Hmm I thought you were gonna send it :)

well thought you didn't want it since you got this 10"...kinda like with the 12" and 15" aura.


If you want I can send it in 2 wks....will work out perfectly this way I can ship it back to my house and I wont have the shove it into my car along with everything else, for moving back home from college. So you still want to try it??? Despite getting this 10"? LMK....Care if I sneak the PG RSd12d in with it too?

[npdang]

Yeah sendem both. I forgot about that ;)

[legend94]

I wonder how much different the 10" is from the 12 and 15"... a while back I remember Andy said something about the VC being slightly different... and the BL curve was also different on the 12" Dumax test. :confused:
I also expected a bit better.

not sure about the new series, but i owned the older gti in the 10,12, and 15 version. the 12 and 15 seemed to be in a different league :confused:

[bdubs767]

not sure about the new series, but i owned the older gti in the 10,12, and 15 version. the 12 and 15 seemed to be in a different league :confused:


Guess well find out....

[DS-21]

It's interesting that the excursion claims for both of the true super-woofers tested thus far seem to be at best highly exaggerated. In this case, all that depth for the throw of a Peerless XLS10 does not seem worth it, even considering the potential (I think realized in the W15GTi) of the Hyperdynamics motor. I don't know what to make of that, as I would expect much better from both Aura and JBL.

I wish Peerless made an XLS15 or better yet XLS18 that I could compare with the W15GTi and Oaudio TC2+ 15!

[bassfromspace]

It's interesting that the excursion claims for both of the true super-woofers tested thus far seem to be at best highly exaggerated. In this case, all that depth for the throw of a Peerless XLS10 does not seem worth it, even considering the potential (I think realized in the W15GTi) of the Hyperdynamics motor. I don't know what to make of that, as I would expect much better from both Aura and JBL.

I wish Peerless made an XLS15 or better yet XLS18 that I could compare with the W15GTi and Oaudio TC2+ 15!

JL Audio FTW!!!!!!!:p

Once I get out of closing for my house, I'll have funds available to ship a driver that actually meets and/or exceeds it's excursion claims.:D

[kappa546]

the depth is definitely way bigger than most other subs and it turned me off when i got them 12 bc i didnt want to build another box. i was convinced it wouldnt fit, but it turns out it did. i usually build my boxes in a compromise of wide and shallow to make my cargo space more useful but the jbl fit just nice. i wouldnt be surprise if many more of you found the same thing after actually measuring your box or just trying it. it's just super deep on paper and in comparison but 10" aint that bad

[300Z]

not sure about the new series, but i owned the older gti in the 10,12, and 15 version. the 12 and 15 seemed to be in a different league :confused:

They're different indeed, the 8 and 10" uses a different motor and VC than the larger siblings.

[300Z]

After a second look and comparing the JBL published specs vs the test results I now think it's actually not that bad. With the only exception being the BL curve, this driver tested pretty close to the published specs. So I guess that would be a bonus and not really a fault huh?:confused:
Published specs PDF (https://www.hci-services.com//tech_doc/documents/JBL/Car/Speakers/W/W10%20GTi/Service%20Tips/W10GTi_rev_f.pdf).

[DS-21]

After a second look and comparing the JBL published specs vs the test results I now think it's actually not that bad. With the only exception being the BL curve, this driver tested pretty close to the published specs.

I don't know, ~12mm xmax vs. a published 17.75mm sounds like a huge difference to me. Hopefully the 12 and 15 aren't as far off, though regardless the W15GTi is one of the finest sounding woofers I've yet heard.

[npdang]

Probably the low inductance.... lower than most midbasses.

[300Z]

Any1 wanna contact JBL and see what they have to say about it? Maybe Andy over at CarSound? :)

[npdang]

JBL rates their xmax by voice coil overhang, so that may explain the discrepancy. Or I miscalculated BL, which would affect the displacement axis. Klippel is also a bit different than DUMAX, as it uses real power to drive the speaker and not pneumatic air pressure. That's why you can rarely reach xsus with Klippel as the driver usually needs to be under tremendous power and heat to reach it... providing the driver has sufficient motor force as well.

[chad]

not sure about the new series, but i owned the older gti in the 10,12, and 15 version. the 12 and 15 seemed to be in a different league :confused:

The 12, 15, and 18 were diffeerent beasts..... JBL Pro did not make a VGC smaller than 12" ;)

[werewolf]

i find it rather disappointing myself :(

But remember, the Harman patent on the "differential drive" technology spends lots more time claiming an improvement in heat dissipation, rather than an improvement in distortion. Not a bad thing, as we have recently seen ;)

As far as i can tell the differential drive is really nothing more than a standard overhung design split into two parts and separated longitudinally.

[thehatedguy]

The 12s, 15s, and 18s were 4 ohm coiled proaudio drivers. If you look around at the JBL Pro site, you could probably figure out which ones were which drivers.


not sure about the new series, but i owned the older gti in the 10,12, and 15 version. the 12 and 15 seemed to be in a different league :confused:

[Neil]

i find it rather disappointing myself :(

But remember, the Harman patent on the "differential drive" technology spends lots more time claiming an improvement in heat dissipation, rather than an improvement in distortion. Not a bad thing, as we have recently seen ;)

As far as i can tell the differential drive is really nothing more than a standard overhung design split into two parts and separated longitudinally.

DD is supposed to improve BL linearity as well by widening the flux field a little bit. Though the BL curve is pretty symmetrical, the off-center positioning is a fine example of the manufacturing challenges that a complicated gap technology like DD presents.

[werewolf]

DD is supposed to improve BL linearity as well by widening the flux field a little bit. Though the BL curve is pretty symmetrical, the off-center positioning is a fine example of the manufacturing challenges that a complicated gap technology like DD presents.
"the proof is in the pudding" ...

Klippel shows that the BL curve certainly does NOT indicate improved BL linearity. And, no real reason to expect otherwise.

[npdang]

Unfortunately, the 15gtimk2 that Bdubs sent me measure the same as the 10".

[Neil]

"the proof is in the pudding" ...

Klippel shows that the BL curve certainly does NOT indicate improved BL linearity. And, no real reason to expect otherwise.

Which may, simply put, be an example of a different implementation of the technology. Slight adjustments in coil length or distance between the two respective fields in the gap can easily result in more linear BL product over a given stroke.

I certainly do not disagree with any Klippel results; it is simply impossible to do so. However, I politely disagree with you on the topic of DD's ability to linearize BL as I have experienced FEA and FEM simulations that clearly demonstrate potential.

[kappa546]

Unfortunately, the 15gtimk2 that Bdubs sent me measure the same as the 10".

damn that really sucks. i wonder if the ultra low inductance is really THAT important then if many of us agree it sounds fantastic. when are you posting those measurements?

[npdang]

It's probably more important than distortion performance, especially for those that are not driving their sub to the limits. You're going to notice a +3db hump more readily than you are a few % thd.

[werewolf]

Which may, simply put, be an example of a different implementation of the technology. Slight adjustments in coil length or distance between the two respective fields in the gap can easily result in more linear BL product over a given stroke.

I certainly do not disagree with any Klippel results; it is simply impossible to do so. However, I politely disagree with you on the topic of DD's ability to linearize BL as I have experienced FEA and FEM simulations that clearly demonstrate potential.
no problem good sir :)

I read the patent expecting to learn more about BL linearization through DD, only to find a complete absence of such a discussion (thermal advantages were the fundamental claims ... very important themselves, of course). Then it occured to me that DD really looks like a standard overhung design, split into two and separated ... so i wasn't expecting much along the lines of an improved BL curve. And the Klippel tests seem consistent with such.

However, i'd love to hear more about the potential of the technology to linearize BL ... i can appreciate that splitting and separating the coil can give an extra "degree of freedom" to flatten, or otherwise manipulate, BL :)

[AVI]

Wow .... This is weird. The 12wGTi I used in my customer's car in Boston , was nothing short of breath taking. EASILY one of the best sounding subs I have ever listened to. It was so good , I purchased one for my own car , put it in a a tweaked ported enclosure , and LOVE the drive to and from work everyday !! I'll be doing a full review soon enough of said sub .... :confused:
Once again I'll say : What does a spec sound like ?

[werewolf]

Wow .... This is weird. The 12wGTi I used in my customer's car in Boston , was nothing short of breath taking. EASILY one of the best sounding subs I have ever listened to. It was so good , I purchased one for my own car , put it in a a tweaked ported enclosure , and LOVE the drive to and from work everyday !! I'll be doing a full review soon enough of said sub .... :confused:
Once again I'll say : What does a spec sound like ?
simple : depends on the spec.

ANY spec can be almost directly correlated to what we hear. And audio specifications provide an objective framework to compare, design, and test audio equipment.

All audio equipment is designed, measured, and tested-in-production against a set of objective specifications. This is possible, in large part, due to the decades of work provided by the pioneers of audio engineering ... who devoted complete careers to correlating what we hear, against what we can measure.

Without this info, i would ask the question : whose ears are used to design audio equipment? Whose ears are used to measure the prototypes? Whose ears are used in the production line?

[AVI]

simple : depends on the spec.

ANY spec can be almost directly correlated to what we hear. And audio specifications provide an objective framework to compare, design, and test audio equipment.

All audio equipment is designed, measured, and tested-in-production against a set of objective specifications. This is possible, in large part, due to the decades of work provided by the pioneers of audio engineering ... who devoted complete careers to correlating what we hear, against what we can measure.

Without this info, i would ask the question : whose ears are used to design audio equipment? Whose ears are used to measure the prototypes? Whose ears are used in the production line?

It's not just the ears Bro .... We also hear with our emotions. I've listened to equipment with near perfect measurements and specs , that sound like pure crap. The simple bottom line is : Does it sound like the original performance , given all of the original's parameters ? ;)
Regardless of what Nguyen measured , the 12" sounds simply amazing , with some of the lowest distortion I've never heard. Get's REAL loud for a single 12 , and is musical beyond belief in the 60 to 80 hz range for such a heavy cone design.

[werewolf]

If the equipment is accurate, it will sound like the original performance. And objective testing is a fine tool for determining accuracy.

Subjective taste is, of course, another matter. Some prefer distortion, and a variety of colorations from the equipment ;)

But I save my emotional pleasure for the artist's performance, not the equipment through which it's reproduced :)

[werewolf]

It's not just the ears Bro .... We also hear with our emotions. I've listened to equipment with near perfect measurements and specs , that sound like pure crap. The simple bottom line is : Does it sound like the original performance , given all of the original's parameters ? ;)
Regardless of what Nguyen measured , the 12" sounds simply amazing , with some of the lowest distortion I've never heard. Get's REAL loud for a single 12 , and is musical beyond belief in the 60 to 80 hz range for such a heavy cone design.
alternatively, i could re-phrase my questions. If we don't "trust the specs" ...

Whose ears & heart are used to design audio equipment? Whose ears & heart are used to evaluate the prototypes? Whose ears & heart do we trust for testing on the production line?
:)
The bottom line, for me, is simply this : The creation and enjoyment of a musical experience is an EMOTIONAL endeavor ... no doubt about it. However, the accurate reproduction of a musical experience is a SCIENTIFIC endeavor. No emotional involvement required, for example, to determine if an amplifier is capable of accurately reproducing an electronic signal. But of course, the enjoyment of a musical experience ... captured electronically in that very signal ... through that amplifier is very emotional indeed :)

It's this "separation", if you will, of the content from the channel-of-reproduction that allows for the economical & efficient design and mass production of audio equipment.

[DS-21]

Ironically, AVI, we're somewhat in the same boat. Despite the disappointing Klippel results, I recently bought a W15GTi to replace the Peerless XLS12+PR in my home office sub. (That woofer and PR will be incorporated into my new main system sub, along with two other XLS12's and XLS12-PR's.) I don't have it in my possession yet, but hopefully it will get to me unscathed. However, werewolf is indisputably right. To pirate the signature of an old audio newsgroup poster, music is art, audio is engineering.

So why did I end up buying the W15GTi? On the basis of listening tests. In theory, if the W15GTi has ~13mm of xmax and the Oaudio TC2+ 15 that was the other woofer in contention has another 5mm on top of that along with the confirmed excellent measured distortion performance of the TC2+ motor, the TC2+ in my closet should be a better-sounding sub. (It's still tentatively for sale, though I'm probably going to use it in an LT'ed sealed enclosure to smooth out room modes in my main system. So after reading the W10GTi and W15GTi tests, I was honestly surprised. But then shortly after reading our gracious host's test resultsI went to visit my friend, who's running the W15GTi we tested together in an ~2.5 cubic foot cabinet LT'ed sub EQ'ed with a Velodyne SMS-1 and powered by the Dayton Class G rack amp. I paid close attention to the cone motion, and realized in his large room how little it needed to move. In my home office, which is a small room with the subwoofer less than a meter from the base of my task chair, even less excursion is required. Now, the BL linearity issue...I don't have a good answer for. It's certainly possible that I'm so accustomed to that kind of nonlinearity that superior performance "sounds worse."

Inductance is IMO a hugely important thing for subjective bass quality. Yes, the upper bass FR anomalies caused by high inductance can (and should be) easily EQ'ed out, but there are plenty of reasons why inductance is bad in and of itself. Subjectively, in my own experience the relationship between perceived quality of bass and Le is pretty linear. To the point where I won't even consider a driver with an inductance of more than ~0.6mH per ohm of voicecoil resistance. I assume there's probably a woofer with an Le below that range with reasonable throw that sucks rocks through a straw, but I've not yet experienced such a beast.

[npdang]

Good point... you're also looking at a 15" driver with an inductance similar to that of a 7" driver, and a much larger cone to boot. You're probably still well below the audible threshold for most reasonable listening conditions and output levels.

[Neil]

I picked up a tube amp for my headphones the other day and it sounds great. Of course, I'd be foolish to think it's a dead-on accurate reproduction of the original recordings.

[DS-21]

One thing I learned about the W15GTi today while making sure my new one's voicecoils were round and measuring its T/S parameters*: JBL overstates the magnetic shielding of the Differential Drive motor system a bit in their whitepaper on it. With the woofer in my lap, my second monitor (a 24" Sun widescreen CRT) started going crazy as soon as I turned it on. (No permanent damage was done.) I experimented with it ~normal to the screen front of the CRT (propped up by my feet) and while it did shift the screen's display over by a few mm it did not seem to affect the color much in that orientation.

I had thought I could place it under my center channel, but it looks like it's going in the back corner where the XLS12 sub was instead.

Not necessarily that relevant to most car installs or most modern audio/HT systems that may use this woofer, as the CRT is a relic, but noteworthy nonetheless.

*Speaking of which, mine measured considerably considerably closer to stock (especially Qts) than the one our gracious host tested. Wonder if there was a change made to the Mk. II not reflected in the spec sheet. (Mine's a Mk. I)

[Neil]

*Speaking of which, mine measured considerably considerably closer to stock (especially Qts) than the one our gracious host tested. Wonder if there was a change made to the Mk. II not reflected in the spec sheet. (Mine's a Mk. I)

What type of variance are we talking about here? DD can be very hard to manufacture with tight tolerances. Is the largest difference manifested in Qes or Qms, or are you aware of which primary parameter (Re, BL, Mms, Cms, Sd) has caused the change?

[AVI]

Ya know , I truly am not sure just how to reply here .... I guess what I often try and point out , is my 24+ years of audio expereinces has taught me something VERY , VERY well .... and that is MANY things that have world class reputations and measurements/specs , sound like pure shit.
And MANY " lesser " things that are not water walkers , often blow me away with fabulous sound quality.
Take the 12" JBL for example ..... Regardless of ANY measurements , literally everyone who has heard it in my car , has commented VERY positively on the sub .... including everyone at Shinjohn's recent meet.
While I respect fully the brains that know and understand all of the numbers which baffle my mind .... numbers mean absolutely NOTHING to me personally .... ONLY what sounds right to my own ears ;)
Hope that makes sense , and for the MANY who have posted on this forum about one of the JBL subs being as good as ANY sub they have ever heard in a car , I would say " yes , it is easily understandable why you would feel that way ..... they truly are AMAZING subs , with their only real drawback being the terribly deep mounting depth ...

[DS-21]

Ya know , I truly am not sure just how to reply here .... I guess what I often try and point out , is my 24+ years of audio expereinces has taught me something VERY , VERY well .... and that is MANY things that have world class reputations and measurements/specs , sound like pure shit.

Example, please. In general, if something audio has stellar specs and sound bad, one of three things is in play.
1) It doesn't meet spec.
2) It is used incompetently (e.g. sticking an excellent woofer in a high-Qtc enclosure or a bad vented alignment, expecting an amp to put out more than it can on a regular basis, installing good drive units in wretched places)
3) The wrong things were measured, and/or the specs left out important details. (A good sign of an inferior drive unit not worth your time is if Le is not spec'ed, for instance.)

Audio isn't art. It isn't magic. It's engineering. The music is the art and the magic that the engineering of audio serves.

Take the 12" JBL for example ..... Regardless of ANY measurements , literally everyone who has heard it in my car , has commented VERY positively on the sub .... including everyone at Shinjohn's recent meet.

The excellent sound quality of the WGTi series is well explained by the measurements, so what's your point? The only disappointment is that its real-world excursion seems overrated. That is more an indictment of the race to ever longer throws damn the potential sonic cost than anything else.

[DS-21]

What type of variance are we talking about here? DD can be very hard to manufacture with tight tolerances. Is the largest difference manifested in Qes or Qms,

Qms was a little different (higher), while Qes was substantially lower. (I meant to type "Qes" in my post above, not "Qts.")

or are you aware of which primary parameter (Re, BL, Mms, Cms, Sd) has caused the change?

Well, looking at our gracious host's measurements, I see that our Sd's don't match up. I plugged in JBL's figure from the datasheet (780 cm^2) whereas he used 855.2 cm^2. Everything else that FuzzMeasure could give me was what I'd consider in the ballpark.

[Neil]

Example, please. In general, if something audio has stellar specs and sound bad, one of three things is in play.
1) It doesn't meet spec.
2) It is used incompetently (e.g. sticking an excellent woofer in a high-Qtc enclosure or a bad vented alignment, expecting an amp to put out more than it can on a regular basis, installing good drive units in wretched places)
3) The wrong things were measured, and/or the specs left out important details. (A good sign of an inferior drive unit not worth your time is if Le is not spec'ed, for instance.)

Audio isn't art. It isn't magic. It's engineering. The music is the art and the magic that the engineering of audio serves.



The excellent sound quality of the WGTi series is well explained by the measurements, so what's your point? The only disappointment is that its real-world excursion seems overrated. That is more an indictment of the race to ever longer throws damn the potential sonic cost than anything else.

Couldn't agree more. In my experience, there have been very, very few pieces of audio equipment (not just talking speakers here) that measured well but sounded poor. It is also worth noting that the work of people like Klippel and GedLee are slowly filling in the gaps between measurement and perception.

When an engineer makes a product, how do they design it? I suppose they sprinkle just enough dust on it to make it sound good ;)

[npdang]

Motor linearity is very important for a number of reasons which I'm sure we all know. However, as DS-21 has pointed out, it hardly matters if you're using the driver within a region that's already below the audible threshold distortion wise. That doesn't mean it's useless. It's honestly just one of many factors that may or may not be very important depending on the application. However, when you're making bold claims about your motor linearity...

[AVI]

Ok DS-21 , I will explain myself , but we will NEVER agree ..... EVER ;)

Here is why : I have proven NUMEROUS times over in double blind listening tests , that I can easily hear differences in different amplifiers for example .... and THIS alone means we will never agree.
So , you want an example : Krell equipment .... Sounds like PURE SHIT. Literally everything EVER made by Krell sounds like pure shit , and yet it measures great. I wouldn't let you give me Krell gear even ...
Vampire Wire is just wire , yet it makes EVERY system I have ever plugged it into sound harsh.
MTX car amps sound like crap to me ... yet measure just fine.
JL Audio amps sound like shit to me , yet measure just fine ....
Rockford Fosgate amps sound like shit to me , yet measure just fine ...
But please DS-21 .... let's both face it : You will NEVER convince me , and I will NEVER convince you ........... EVER ! :D

[DS-21]

Here is why : I have proven NUMEROUS times over in double blind listening tests

Bullshit. If that were actually true, you'd be written up in the JAES, JASA and other relevant peer-reviewed scientific journals, and your brain would be extensively studied to see why you demonstrate such greater hearing acuity than the rest of us. The Army and Marines would probably be interested in knowing as well, given that such superhuman hearing ability would possibly save American lives on the battlefield.

The other alternatives are that you're either lying or the tests may have been double blind, but they were not (and I note your omission of the next two words) level matched.

So , you want an example : Krell equipment .... Sounds like PURE SHIT. Literally everything EVER made by Krell sounds like pure shit , and yet it measures great. I wouldn't let you give me Krell gear even ...

If someone ever makes you that offer, let me know and I'll be happy to relieve you of the burden.

But please DS-21 .... let's both face it : You will NEVER convince me , and I will NEVER convince you ........... EVER ! :D

The gulf between faith-based extremist ideology and empirically-rooted knowledge is quite large, I agree.

[AVI]

DS-21 ..... Did someone shit in your Wheaties today ?
I'll not waste any more of my time with you.
Cheers :rolleyes:

[werewolf]

i find it rather disappointing myself :(

But remember, the Harman patent on the "differential drive" technology spends lots more time claiming an improvement in heat dissipation, rather than an improvement in distortion. Not a bad thing, as we have recently seen ;)

As far as i can tell the differential-drive is really nothing more than a standard overhung design split into two parts and separated longitudinally.
i've underestimated the technology in this subwoofer :(

My above statement misses a very key element of JBL's differential drive technology, something that separates it ... in a very clever, fundamental way ... from my simplified description above. Simply put : the current flows in opposite directions in the two coils :) But the magnetic elements are arranged in such a way that, even though current flows in opposite directions in the coils, they still exert a force in the same direction on the cone (under normal excursion). Very clever boys ... these JBL engineers :cool:

So what? What are the advantages of two longitudinally separated coils, with current flowing in opposite directions? At least two :

1. MAGNETIC BRAKING. Under extreme excursions, as coil #1 approaches the magnetic gap of coil #2, the opposite current flow creates a limiting force (from approaching the "wrong" gap, if you will) ... this is called magnetic braking. And it's a beautiful, built-in mechanism to physically limit over-excursion.

2. LOWER INDUCTANCE. This is a thing of beauty. By comparison, "shorting" or Faraday rings in drivers reduce inductance by : current in the moving coil creates a magnetic field, which induces a current in the shorting ring. The current in the shorting ring creates a secondary magnetic field, which "opposes" the primary magnetic field ... thereby lowering the net inductance of the motor. What's so clever about the JBL technique, is that the opposite current flow in the second coil creates a magnetic field that opposes the field of the first coil ... thereby lowering inductance, even in the absence of any additional shorting rings! A much more elegant solution, actually :) The JBL patents for differential drive actually do include shorting rings as well ... not sure what's in the drivers npdang measured, but we sure know that the inductance is frighteningly low.

Just in case anyone is wondering ... NO, you can't achieve these advantages with a typical dual-voicecoil sub. The magnetic elements are not aligned properly to support it ... so if you wire the second coil so that current flows in opposition from the first, you won't get any output from the sub :(

One final note : the importance of low inductance continues to impress upon me. I've written lots about transient response of subs, hopefully shedding some light on some bad info that floats around the web. But low inductance really is a very desirable parameter ... think of inductance (in concert with coil resistance) as a built-in low-pass filter ... with attendant magnitude and phase shifts ... which will limit the high-frequency extension of the sub, and can make for difficult times integrating with midbass drivers.

T/S parameters, which control the high-pass regime of the sub's response, can be equalized. Not so easy, to EQ out a sub's inductance ;)

Even large signal linearity tends to be a bit over-emphasized, i think, given "normal" listening levels for critical listening (especially in small-volume listening spaces, like the car).

This really is a very interesting driver.

[kappa546]

for some reason this mechanism seems very familiar. perhaps thats how i naively (albeit correctly ;) ) guessed the dual gap worked... like the poles on a magnet. pretty cool though. how exactly do they arrange the coils to achieve this and how is it different from a normal dvc driver wolfie?

[werewolf]

for some reason this mechanism seems very familiar. perhaps thats how i naively (albeit correctly ;) ) guessed the dual gap worked... like the poles on a magnet. pretty cool though. how exactly do they arrange the coils to achieve this and how is it different from a normal dvc driver wolfie?
The driver is DEEP ... with good reason :)

The two coils are not ... in fact, can not be ... coincident. They must be longitudinally separated, actually working within two separate magnetic gaps. In a DVC motor, both coils operate within the same gap (i'm thinking this is true, i'm sure if there are exceptions they will be pointed out to me :) ). Remember, in most DVC subs the coil is "split" (electrically, more than physically) simply to allow a couple impedance options for optimal performance with any given amplifier.

The JBL differential drive really is fundamentally different. Check the references already posted in this thread, for more info and a few cutaway drawings ...

[kappa546]

i'm reading the pdf now. the coil to each gap really explains it, pretty ingenious.

edit: after looking at the diagrams in the pdf i remember where i saw it before... the jbl product literature that comes with the wgti's lol. it also explains the inverted polarity coils and the magnetic braking.

[kappa546]

i wish there was a nrt/ddd mutant... large diameter, single layer DDD configured vc's/motor, limited to <18mm xmax to help keep mms low and efficiency high (target = >90db/1w/1m) and 4-600wrms power handling. i might as well go all out and add a tiny Vas and moderate fs/qts for some manageable enclosures. i blame the average consumer for beleiving that they're sub that "puts out ( LOL!) 2000W" is better for something like this never being widely implemented. i can dream though...

[Luke352]

Bullshit. If that were actually true, you'd be written up in the JAES, JASA and other relevant peer-reviewed scientific journals, and your brain would be extensively studied to see why you demonstrate such greater hearing acuity than the rest of us. The Army and Marines would probably be interested in knowing as well, given that such superhuman hearing ability would possibly save American lives on the battlefield.

.

Your wrong on this one DS-21, most pure amplification circuits will measure and sound the same, but once you put the rest of the stuff that a amplifier consists of such as pre-amp, gain circuit etc.. they will and do sound different, do you understand the difference here. Richard Clark's imfamous amp test cannot be beaten because they either bypass the gain and pre amp circuits of the amps or eq them so that the pre-amp and gain induce the same sound and response etc...

When you read RC's amp he isnt argueing that amps in there entirety won't sound different, only that there amplification circuit by itself won't sound any different.

Luke

[DS-21]

i wish there was a nrt/ddd mutant../

I'd hit that!

Your wrong on this one DS-21, most pure amplification circuits will measure and sound the same, but once you put the rest of the stuff that a amplifier consists of such as pre-amp, gain circuit etc.. they will and do sound different, do you understand the difference here.

The difference is entirely in your poor little head. (And dammit, it's you're.)

What, exactly, is the difference between "amplification circuits" and "gain circuit," again?

Richard Clark's imfamous amp test cannot be beaten because they either bypass the gain and pre amp circuits of the amps or eq them so that the pre-amp and gain induce the same sound and response etc...

I couldn't give two shits about "Richard Clark's infamous amp test." The reality is that entire electronics chains from the digital source to the end of the speaker leads including all switching and cabling in between, if designed competently, sound exactly the same up to the output limits of the less capable one. There are a bevy of serious peer reviewed scientific papers supporting that fact, beginning at the very latest with David Clark's paper "High Resolution Subjective Testing Using a Double Blind Comparator" in JAES Volume 30 Number 5 pp. 330-338; May 1982. If you haven't read and at least attempted to understand that paper at the very least, you have no business talking about this subject at all.

When you read RC's amp he isnt argueing that amps in there entirety won't sound different, only that there amplification circuit by itself won't sound any different.

Differences in level, FR, and distortion above known audible thresholds cause sonic differences? No shit! Competent gear - most of the stuff out there, with the bulk of exceptions being found in the extreme low and high ends - doesn't have differences above audible thresholds in the latter two, and if level is thought of as a cause of audible differences, then twirling a volume knob will give you entirely different components!

[Neil]

i wish there was a nrt/ddd mutant... large diameter, single layer DDD configured vc's/motor, limited to <18mm xmax to help keep mms low and efficiency high (target = >90db/1w/1m) and 4-600wrms power handling. i might as well go all out and add a tiny Vas and moderate fs/qts for some manageable enclosures. i blame the average consumer for beleiving that they're sub that "puts out ( LOL!) 2000W" is better for something like this never being widely implemented. i can dream though...

Not to be a wiener, but you are pretty much dreaming there. A lot of the requests you are asking for a mutually exclusive; if you're willing to meet halfway on a lot of them, then you'll get what you're looking for, but then you've got something that's just like 90% of the product already available.

[kappa546]

Not to be a wiener, but you are pretty much dreaming there. A lot of the requests you are asking for a mutually exclusive; if you're willing to meet halfway on a lot of them, then you'll get what you're looking for, but then you've got something that's just like 90% of the product already available.

i don't see a problem with it, the specific goals are flexible (sensitivity) and subject to change. want to elaborate though? all i'm saying is i wish someone made a driver like this, not that i'm actually going out to contract aura for some oem products and lisencing DDD (or viceversa)

[chrismercurio]

I searched the forum and couldn't find a test of the 13w7 from JL. Does anyone have any experience with both of these woofers or opinions on how they compare? Subjectivity as well as tests are very welcome.

Thanks,

C

[bassfromspace]

I searched the forum and couldn't find a test of the 13w7 from JL. Does anyone have any experience with both of these woofers or opinions on how they compare? Subjectivity as well as tests are very welcome.

Thanks,

C

Carsound.com should have a test of the 13w7 on it's website ( i think). Richard Clark also tested the 13w7 personally and that should be in the archives at Carsound.com as well.

[chrismercurio]

I looked for it and couldn't find it. Richard Clark did say some nice things about it, but there are no formal "reviews" that I could find. I'm looking for Klippel or Praxis tests, or any SPL/THD tests of the 13w7 woofer. My application would be for a home woofer so if anyone wants to chime in with an opinion on these two woofers I'm all ears.

Thanks,

C

[johnson]

So the 10" isnt as good as the 12"? I might downgrade to a 10 since I have a hatch and wouldnt need something too big.

[gbraen]

So the 10" isnt as good as the 12"? I might downgrade to a 10 since I have a hatch and wouldnt need something too big.

I don't know about the 12", but the 10" sucks. I have one and then the old 1200GTI, the old one is muck nicer!! Much more detailed bass and attack, new one is just slappy at its best.

[kappa546]

I don't know about the 12", but the 10" sucks. I have one and then the old 1200GTI, the old one is muck nicer!! Much more detailed bass and attack, new one is just slappy at its best.

i find that REALLY hard to believe. want to to tell us more about the setup?

[300Z]

i find that REALLY hard to believe. want to to tell us more about the setup?

I agree. While I'm big fan of the old school GTi the new WGTi is awesome as well altho two different beasts. :)

Leo

[chad]

altho two different beasts. :)

Leo

Egg-Zachary

[gbraen]

i find that REALLY hard to believe. want to to tell us more about the setup?

Yes I can.

I have a small Toyota Corolla which I have use my equipment in. Currently setup is Alpine IDA-X001-RUX-C701/PXA-H701, both iPod Classic and cd-changer with optical output directly into the PXA.

For amplifiers i use three Genesis Serie3; Dual Mono, 4 channel and a Monoblock for the sub(s)

Front speakers are JBL TC25 and JBL 600GTI.

My subwoofer enclosure for the W10GTI (Mk1) i've both tried 21 liter and 32 liter, sealed box. In such a small car i thought the output would be more powerful? And any punch at all? The sub fires backwards.

[Luke352]

.

My subwoofer enclosure for the W10GTI (Mk1) i've both tried 21 liter and 32 liter, sealed box. In such a small car i thought the output would be more powerful? And any punch at all? The sub fires backwards.

It's still a 10" Sq orientated sub in a sealed enclosure in a medium sized car, it's gonna struggle if your after lots of output unless you try it ported, or step up to the 12 or 15 or get a more SPL based sub. They have respectable output but I wouldnt call them a very high output sub.

I had a IDQ15 v1 before my W15GTi and I will agree that the gti doesnt have the same punch as the IDQ, but the GTi goes a good 10-15 hz lower IMO. I find the tone of the GTi to be quite smooth in the higher subbass area and it will play flat (with eq'ing down around 50Hz in my car) to about 25hz and down a 2-3db at 20 hz, but it's main attraction is how cleanly it plays those lower notes and it stays extremely tight while doing it, something the IDQ failed miserably at, if it could even reach those notes with any kind of respectable output.

[gbraen]

It's still a 10" Sq orientated sub in a sealed enclosure in a medium sized car, it's gonna struggle if your after lots of output unless you try it ported, or step up to the 12 or 15 or get a more SPL based sub. They have respectable output but I wouldnt call them a very high output sub.

I had a IDQ15 v1 before my W15GTi and I will agree that the gti doesnt have the same punch as the IDQ, but the GTi goes a good 10-15 hz lower IMO. I find the tone of the GTi to be quite smooth in the higher subbass area and it will play flat (with eq'ing down around 50Hz in my car) to about 25hz and down a 2-3db at 20 hz, but it's main attraction is how cleanly it plays those lower notes and it stays extremely tight while doing it, something the IDQ failed miserably at, if it could even reach those notes with any kind of respectable output.

Maybe i should try the new MK2 version? Is it much better? I was planning to buy to W12GTI, and use the Genesis Monoblock on them, that should output around 800-900 watt from it. With 70 litre sealed sealed box on 2 i will get some SQ bass with decent output i guess.

[kappa546]

the mk2 are the exact same aside from some cosmetic changes. i agree with luke, if output was your main problem remember it's still just a 10". ime with the 10 and 12 they play 80hz down very smooth and accurately, the punchiness you're after is probably some peakiness you experienced with another sub.

[thehatedguy]

You guys have to remember the original GTi speakers were prosound woofers...and the new ones are designed as subwoofers. I wouldn't doubt the older ones had more punch to them since they would have better midbass ability- some people in the prosound world used them as midbasses.

But the new ones are pretty impressive too.

[chad]

You guys have to remember the original GTi speakers were prosound woofers...and the new ones are designed as subwoofers. I wouldn't doubt the older ones had more punch to them since they would have better midbass ability- some people in the prosound world used them as midbasses.

But the new ones are pretty impressive too.

If it's a 12 it was probably ONLY used as a midrange/midbass from around 100Hz up to 1.6K

the 15's were only used in one sub cab that was consumer level, the SR4715 which was a dual 15 that I was never really impressed with. That motor was also used in the SR4725 and SR4735 full range cabs and was good from around 50Hz to 1.6K the 38 added a cone midrange that loved to blow up. The cone in the GTi series is stiffer and heavier giving it a lower FS and a bit better low end response than the 2226G/2206G at the expense of mechanical power handling and a few other tidbits. They were damn good drivers, just quick as hell, but wanted a large vented enclosure, but it was worth it.

[Luke352]

but wanted a large vented enclosure, but it was worth it.


The new GTi seems to model much the same, they want big enclosures way bigger then most people would consider acceptable for in car use.

Since if you put the specs in the normal beta version to achieve a Q of .707 you need a 4cube sealed box yet JBL recommends around 1.6cubes (i believe) which gives you a Q of .97, which seems really high, high enough for it to sound really odd and to have poor low end extension yet this is definitely something the JBL doesnt struggle with, it sounds great and goes lower then any sub I've heard, and definitely goes a hell of a lot lower in car then the plots show, and that was measured to confirm. Then of course you have the ported enclosure's, JBL recommends 4 cubes tuned to 30hz (i think) I'd like to try this but i can't fit it, yet WinIsd comes up with 8.2cubes tuned to 21hz. Yet the people who run GTi's in the recommended ported enclosures absolutely rave about them...

[gbraen]

The new GTi seems to model much the same, they want big enclosures way bigger then most people would consider acceptable for in car use.

Since if you put the specs in the normal beta version to achieve a Q of .707 you need a 4cube sealed box yet JBL recommends around 1.6cubes (i believe) which gives you a Q of .97, which seems really high, high enough for it to sound really odd and to have poor low end extension yet this is definitely something the JBL doesnt struggle with, it sounds great and goes lower then any sub I've heard, and definitely goes a hell of a lot lower in car then the plots show, and that was measured to confirm. Then of course you have the ported enclosure's, JBL recommends 4 cubes tuned to 30hz (i think) I'd like to try this but i can't fit it, yet WinIsd comes up with 8.2cubes tuned to 21hz. Yet the people who run GTi's in the recommended ported enclosures absolutely rave about them...

The W10GTI should have sealed enclosure 0,74 cubes, but i didnt think it goes low enough. I tried 1,24, and liked that much better, but think about 1 cube should be good.

BTW, SRP for a W12GTIMK2 in Norway is $1115, it have to be really good at that price!

[innsanes]

I've been trying to try a new set up. The JBL from reading on this page sounds like a good driver to try out. I wonder how it stacks up against the Diamond d9/TDX im currently running? The basket looks similar in the venting fins.

[kenk]

I've been trying to try a new set up. The JBL from reading on this page sounds like a good driver to try out. I wonder how it stacks up against the Diamond d9/TDX im currently running? The basket looks similar in the venting fins.
they look similar but I doubt they sound the same. The GTI uses DDD technology and 100x sexier

[gbraen]

I finally got my W10GTI in a ported enclosure, and WOW!!!

Its absolute fantastic. The box is 1,75 cube, and is ported to 25 hz just as suggested from JBL.

It is by far the sub with the lowest extension i ever heard. Very pleased now.

[kappa546]

from "sucks" to "absolutely fantastic" :D

[gbraen]

from "sucks" to "absolutely fantastic" :D

Sucks in sealed, excellent in ported enclosure, yes!

[chad]

Sucks in sealed, excellent in ported enclosure, yes!

It's a JBL ;)

[trunks9_us]

yes i agree i have not liked it in my sealed enclosure but i do plan on doing a ported box soon. I will give this thread my opinion when i get it done as well.

Sucks in sealed, excellent in ported enclosure, yes!

[DS-21]

It's a JBL ;)

But the W15GTi is perfectly happy in a sealed box. One's rocking my nearfield system as we type. :)

[chad]

But the W15GTi is perfectly happy in a sealed box. One's rocking my nearfield system as we type. :)

It'll blow up :p

Just teasing. But you are making James roll in his grave by doing that :D

[backwoods]

I's got a quad of those w15gti's beltin it out from the attic in an IB config at the house. They sure can dig low!

Also got some old school gti 15s in the car rocking it out. Not near the low end extension, but I'd play those suckers up to 500hz and they still sound fantastic. ;)

[chad]

I's got a quad of those w15gti's beltin it out from the attic in an IB config at the house. They sure can dig low!

Also got some old school gti 15s in the car rocking it out. Not near the low end extension, but I'd play those suckers up to 500hz and they still sound fantastic. ;)

I used the 1500GTi's IB in a caddy with good results :D

[chrismercurio]

My application would be for a home woofer so if anyone wants to chime in with an opinion on the JL Audio 13W7 and the JBL w15GTI mk2 I'm all ears. My emphasis is on SQ not ultimate SPL, but shaking the house is cool too.

Thanks,

C

[snaimpally]

LOL! The mounting depth of the 10" is 9"+! Massive is an understatement.

[tommyd]

I know it the 12 is 10.25 BARELY fit in my box. It's pretty tight in there what can I say.:cool:

[Andy Wehmeyer]

This is a really old thread, but I have something to add about the Klippel test and the determination of Xmax.

The motor uses two coils and two gaps. When excusrion is low, both coils operate in the gaps for reduced distortion (gaps and coils are in opposing polarity). At high excursion, one cil drives the woofer forward and the other drives the woofer rearward. as soon as one coil leaves its gap, the BL falls, but the other coil is in its gap. This is one speaker for which the XMAX can't be accurately determined by measuriing BL.

[Audio.Genius]

Well after receiving numerous requests for my response to this hotly contested subject, I have opted to respond.
My simple answer at first is to respond to the last thread presented by my old buddy Andy. While it can be stated that the Klippel does, by design have some intrinsic limitations with regard to it's determination of Xmag values, one must be careful not to categorically dismiss the efficacy of the Klippel completely as this device has successfully measured two different drivers with very similar motor topologies to the GTI.
Of course I am referring to the Orion H2 and the Cerwin-Vega Stroker Pro units. Now I am aware of the subtle differences in the design of these three drivers, and I wish not to have a rebuttal thrown in my face. I am only mentioning these drivers to establish the fact that the Klippel device has indeed proven valuable in assessing excursion data as well as flux field behavior on drivers that are also built on a different platform.
I welcome your responses.

[trunks9_us]

Quick question about these subs.

VOICE COIL DC RESISTANCE: REVC (OHMS)* . . . . . 3.20

I was told since there 3.20 ohms there really like 4 ohm subs vs 6 ohm subs. What i need to know is what are they really because i am running 2 of them right now on a sundown 1500d which is 1.5 ohm load according to jbls wiring and spec sheet. I just want to make sure its getting 1.5 ohms and not really 2 ohms because my amp gets 800 rms at 2 ohms and 1500 rms at 1 ohm. Is there any way someone could tell me if these subs are actual 6 ohm subs or are really 4 ohm subs? The guy told me that the DC RESISTANCE goes up as bass is being played but i am not sure of this which is why i am asking the experts.

[trunks9_us]

Quick question about these subs.

VOICE COIL DC RESISTANCE: REVC (OHMS)* . . . . . 3.20

I was told since there 3.20 ohms there really like 4 ohm subs vs 6 ohm subs. What i need to know is what are they really because i am running 2 of them right now on a sundown 1500d which is 1.5 ohm load according to jbls wiring and spec sheet. I just want to make sure its getting 1.5 ohms and not really 2 ohms because my amp gets 800 rms at 2 ohms and 1500 rms at 1 ohm. Is there any way someone could tell me if these subs are actual 6 ohm subs or are really 4 ohm subs? The guy told me that the DC RESISTANCE goes up as bass is being played but i am not sure of this which is why i am asking the experts.

[tcguy85]

Quick question about these subs.

VOICE COIL DC RESISTANCE: REVC (OHMS)* . . . . . 3.20

I was told since there 3.20 ohms there really like 4 ohm subs vs 6 ohm subs. What i need to know is what are they really because i am running 2 of them right now on a sundown 1500d which is 1.5 ohm load according to jbls wiring and spec sheet. I just want to make sure its getting 1.5 ohms and not really 2 ohms because my amp gets 800 rms at 2 ohms and 1500 rms at 1 ohm. Is there any way someone could tell me if these subs are actual 6 ohm subs or are really 4 ohm subs? The guy told me that the DC RESISTANCE goes up as bass is being played but i am not sure of this which is why i am asking the experts.

just whip out the DMM and see what your final impedance is.

[trunks9_us]

just whip out the DMM and see what your final impedance is.

Actually i have a cheap multimeter from harbor freight think i paid 7 bux for it will it work?
Its a cen-tech.

How would i do this?

[npdang]

They are 4 ohm subs, for your purposes.

[trunks9_us]

They are 4 ohm subs, for your purposes.

ygpm

[trunks9_us]

hey so you said 4ohm subs for my purpose what does that mean my purpose? I took the speaker wire off my amp to measure the subs final ohm load it shos 1.7 so its closer to 2 ohms but why is it dual 6 ohm then?

[npdang]

This is a really old thread, but I have something to add about the Klippel test and the determination of Xmax.

The motor uses two coils and two gaps. When excusrion is low, both coils operate in the gaps for reduced distortion (gaps and coils are in opposing polarity). At high excursion, one cil drives the woofer forward and the other drives the woofer rearward. as soon as one coil leaves its gap, the BL falls, but the other coil is in its gap. This is one speaker for which the XMAX can't be accurately determined by measuriing BL.
Lacking an intimate understanding of how the Klippel arrives at an xmag value, I can however say that this test was conducted without the use of the laser. In those cases, it is necessary to import BL to determine the absolute x scale. Does the measured BL seem right to you? Out of convenience, I've been using the woofer tester 2, which I've been told tends to give erroneous results more often than not. Simply increasing or decreasing imported BL will have a huge effect on xmag.

Other than that, I'm not sure why the relative shape of the curves (which are arguably just as important as absolute xmag), wouldn't be considered meaningful.

[Tommythecat]

If you read Klippel's Application Notes, it will be come clear that he is defining all excursion limits (from various parts of the system) on a performance basis. The performance criteria is based on an acceptable maximal level of distortion.

He suggests a BL minimum of 82% of rest will approx. 10% IMD. The other limits also follow this scheme of 10% distortion product due to change of the parameter over stroke (doppler, suspension, etc.).

I find this method consistant no matter the driver design. Andy's contention that JBL's dual drive is any different does not make sense. The flux field across the magnet will fall at some point - so there will be a drop in Bl and an introduction of distortion. Nevermind, as he said, one of the coils will leave a gap under high excursion = drop in Bl.

This stuff is Klippel 101 - I hope that anyone who touches the Distortion Analyzer has either: bothered to read the AN's, or attended a seminar of Klippel's. These are essential if one wants to interperate any of the DA's modules.


PS I forgot to say that the aforementioned Application Notes are available to all on Klippel's webpage.

[Neil]

This is a really old thread, but I have something to add about the Klippel test and the determination of Xmax.

The motor uses two coils and two gaps. When excusrion is low, both coils operate in the gaps for reduced distortion (gaps and coils are in opposing polarity). At high excursion, one cil drives the woofer forward and the other drives the woofer rearward. as soon as one coil leaves its gap, the BL falls, but the other coil is in its gap. This is one speaker for which the XMAX can't be accurately determined by measuriing BL.

Sorry Andy, but can you expand on this a bit? A decrease in the number of windings that cut the flux or a decrease in the density of the flux (or both) that is significant enough to drop BL to the prescribed 82% mark is the Klippel defined mark for Xmax, as this correlates with a 10% distortion level (exactly as Tommy described). I don't see why the Differential Drive topology differs in this respect.

Perhaps you're citing the nature of the Klippel "measurements", ie. perhaps there is difficulty in statistically fitting the curves to fit with Klippel's model, but again...I'm not sure I understand why only drivers of this topology would suffer that problem.