DiyMobileAudio.com Car Stereo Forum banner
1 - 20 of 49 Posts

·
DIYMA Founder
Joined
·
4,757 Posts
Discussion Starter · #1 ·
What a beautiful, and surprisingly heavy 12" driver. The cone is a true anodized black aluminum, and not painted. The rubber gasket also runs only along the top of the driver, similar to the old style cork gaskets, and while it looks great it doesn't help to provide a seal with the baffle.

Looking at the heavy cast frame, you can see alot of attention to detail in this woofer. Notice there are venting holes not only under the spider and through the pole, but in the gap where the voice coil sits as well! And upon closer inspection, you can see the thick copper ring on the outside of the gap. I'm assuming from Partsexpress literature, that there's also another copper ring above and below the magnetic gap. Wow :)

Breaking this driver in with pink noise, I also noticed very little rub/buzz and mechanical noise. However, the cone breakup was very clearly audible giving a noticeable metallic coloration to the sound. I only mention this to discourage anyone from using it as anything but a subwoofer, even though inductance is astonishingly low. Looks like a great candidate for IB use.





Very nice... Le actually measured half of what was spec'd. Efficiency right on spec as well. Ripple at ~1.6khz ... sign of the first breakup mode. Vas of 87L will probably mean a large size sealed box.



Free-air, unbaffled nearfield frequency response @ 2.83Vrms.



Very nice curves. Bl is indicative of a well designed underhung driver with a smooth flat plateau and gently sloping ends. Centering is a tiny bit off, but not a big deal. Kms curve is almost perfectly symmetrical and centered. Excellent design.

The inductance variation is also one of the best that I've measured in any driver, with only about + 8%/ - 15% variation through it's entire operating range. Looks like the triple copper rings have done their job.

I'd put 1 way xmax right at 14mm, exactly as rated... although the driver has quite a bit of mechanical throw that's not being used.




I really like this driver. It's very well designed and executed. Although 14mm of 1 way xmax isn't anything special these days, within it's limits the driver performs admirably and in my experience so far without peer. Especially when you factor in the price of $119 per unit.
 
G

·
Another excellent review. You guys already know this, but man Dayton must now be recognized as a true frontrunner in the world-class driver market, and the absolute tops for value :)
 

·
DIYMA Founder
Joined
·
4,757 Posts
Discussion Starter · #5 ·
I'll be posting the Peerless 830845 xxls 12" results in a minute. It's pretty much just as good as this one, if not perhaps a slightly better Le vs. x curve and better centering on the bl.
 

·
Registered
Joined
·
5 Posts
npdang said:
I'll be posting the Peerless 830845 xxls 12" results in a minute. It's pretty much just as good as this one, if not perhaps a slightly better Le vs. x curve and better centering on the bl.
I would hope so considering it's roughly $155 dollars for one.

Noidster
 

·
Registered
Joined
·
25 Posts
I was hoping these did as good as they looked like they would.

Definately a XLS/TC2+ contendor.

I do believe one of these will make its way into my car.
 

·
Registered
Joined
·
17 Posts
couple of comments:

- malcentering of Bxl is about 2.5 mm - not really a trifle! considering that compliance is well-centered, the coil needs to go into a different production (edit: meant to write position), something that can be fixed in manufacturing quite easily - have you contacted Darren on this?

- are you sure the motor is underhung? the top plate doesn't look like it is 20 mm thick - maybe it is middlehung, i.e. thinnish top plate but very long cylindrical pole piece?

- negative displacement means cone goes in? so inductance goes down as the cone moves towards the magnet? this is a case of too much Faraday shielding below the top plate and too little above - this driver could use a more massive ring on the top side of the pole piece!

- what frequency is used in the inductance vs. displacement measurement? for a sub, inductance vs. displacment is not that important, surpressing magnetization modulation is more important (whích is probably why there is more shielding below than above the top plate) -- is there a way to measure this with the Klippel system?
 

·
DIYMA Founder
Joined
·
4,757 Posts
Discussion Starter · #13 ·
Some good comments there.

For a sub, I generally do not consider a few mm off centering much of a big deal due to the long coils and our insensitivity to second order distortion at those frequencies.

As far as the motor, I did not want to give the impression that it was an underhung motor... only that the bl curve has the "appearance" of being one.

This is the only info I could find in the manual with regards to Klippel measurement:

"An electro-mechanic equivalent circuit with lumped elements can model electrodynamic transducers at low frequencies successfully"

"The Loudspeaker is measured in a normal operating mode while reproducing noise. Optimal parameters are estimated by nonlinear system identification based on adaptive inverse control. Using back EMF detection the information is derived from the voltage and current available at the loudspeaker terminals..."

Not too useful... if anyone has any links that maybe more informative I'd love to see them. About the only thing I could gather from that was "noise, low frequency stimulus", "measured current/voltage at the speaker's terminals", and extrapolated parameters based on an electro-mechanical model.
 
G

·
I'll give it a shot, and provide some good references :)

We want to determine some standard parameters for a loudspeaker under-test. The first thing we need is a good "model" for the speaker. It has been shown, largely through the groundbreaking work of Beranek and later Small, that a loudspeaker working in it's piston range is accurately modelled by an electrical equivalent circuit, where the various circuit elements represent the electrical, mechanical & acoustical elements of the actual speaker. So we know the "form" of the electrical model for the driver ... we just need to figure out the values of the various elements to represent the exact driver being tested. That's what's meant by an "electro-mechanical equivalent circuit with lumped elements can model electrodynamic transducers at low frequencies successfully."

OK so we have the circuit form, how do we assign each element in the model the correct value, to accurately represent the speaker under-test? A great way to do it, at least conceptually, is to drive the actual loudspeaker with a test signal ... perhaps noise ... and measure it's real output. You may measure the output with a microphone, a laser, or just the voltage/current at the speaker leads ... depending on what info you need. Now here's the real trick .... what you need to do, probably through computer simulation, is to drive the electrical model of the speaker with the same stimulus. Then, you adjust the value of the circuit elements in the model until you null the difference between the real speaker output and the output of the simulated model. When a null is achieved, you have assigned the correct value to the elements in the model. This is a simplified explanation of "adaptive inverse control" used for system (loudspeaker) identification & modelling.

What you'll see in the following links is several pictures of a real speaker driven by a certain stimulus, in parallel with a circuit model of the speaker driven by the same stimulus. When the difference between the two is driven to zero (or very small), the model accurately represents the speaker and you have the element values you were looking for. Of course there's complications, mostly due to large-signal nonlinearities ... which basically means that the circuit element values (that represent the speaker) change as the stimulus amplitude increases.

http://www.klippel.de/pubs/default.asp

In particular, check out :

The Power of Loudspeaker Models
Fast and Accurate Measurement of Linear Transducer Parameters
 

·
Registered
Joined
·
9 Posts
The tests show that both this and the XXLS will perform excellently with a 4th order crossover at 250Hz. Consider the 10" versions of the driver too. It will make the crossover easier. The 10" will give you more breathing room before the first breakup node and also before the driver becomes less omni-directional.
 

·
Registered
Joined
·
17 Posts
I saw a Klippel system once at an audio fair, and it was equipped with a laser displacement sensor, possibly also with a calibrated mechanical actuator.

After going back to the spec, I now realize the Klippel system can be operated without either (i.e. with just the distortion analyzer box & software), and will still calculate Bxl and suspension compliance curves. Is this how these curves were generated?


Knowing how many nonlinear parameters there are in a loudspeaker, I would tend to suspect that a rest position calculated just from impedance data and acoustic measurement can easily be off by a couple of mm. Then of course, there are mechanical hysteresis effects such as suspension creep, and this in combination with a non-symetrical inductance vs. displacement curve may result in the "zero" position being different from DC at various frequencies. Maybe the Klippel calculates an AC rest position, but at what frequency and drive voltage?
 

·
Registered
Joined
·
9 Posts
npdang, capslock,

Can you explain to me what causes the "inductive hump" in bass drivers? I see the Dayton has a bit of one and the XXLS doesn't. But the Dayton's Le is less than half?
 

·
Registered
Joined
·
9 Posts
I'm refering to the bump around 70Hz followed by the dip around 200Hz. I see this frequently on the FR of high excursion subwoofers. It seems to be more pronounced on drivers with higher Le. On the Peerless thread you make note of the absence of it on that driver.

Thanks.
 
1 - 20 of 49 Posts
Top