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Old 04-04-2013   #1
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Default Alpine Type R 12D2

Those who know me know that I'm always on the lookout for good, cheap 12" drivers for Car audio and other duty. 12" drivers seem to hit the sweet spot of size and performance, and because of the high costs of shipping and duties, it's important to me that the cost be kept as low as possible.

My 12" drivers I'm currently using in my Car for car audio duty are Infinity 122.7Ws, which offered the best value back when I purchased them for about US$100 each . Even better, they are neo-magnet drivers, so the weight (and therefore any associated shipping costs) of each 122.7W was pretty low when compared to similar drivers. Unfortunately, the surrounds started separating from the cones a few weeks ago, and with my birthday coming up, I thought it was good time to replace them (SWMBO - "new subs, AGAIN?" Me - "but it's my birthday!").

After perusing the technical specs of several brands, I eventually decided on the Alpine Type R 12D2s. They were in third position on my "displacement/$" list (the top rung on the list is occupied by another Alpine driver, btw), but offered the most linear displacement (Sd*Xmax) of the group. I would have preferred to go with a neo-magnet driver again (for the reasons previously stated - one of these 12D2s weighs twice as much as a 122.7W, with some change left over), but it seems no-one really has a suitable one on the market these days, likely due to the current high costs of manufacturing these magnets. I also chose the 12D2 rather than the 12D4 because two of them will provide a 2-ohm load to my subwoofer amplifier, an Alpine PDX-M12.

I received the 12D2s two days ago, and ran them through a few tests. Measured t/s parameters are quite close to the published specs (close enough so you can use the published specs in any computer-based box design program). Well, except for Le, which my WT3 put at 3.1 mH, quite a bit higher than the quoted 2.23 mH for this driver. It's a bit high for a driver that has a shorting ring, so I'm a bit curious as to why that's the case.

Concerning physical attributes, the 12D2 is pretty solidly built, with a very, very stiff cone structure and a suspension, while it appears to consist of a just a single spider and the "HAMR" surround, appears to me to be firm enough for the driver's intended purpose. Motor noise was also pretty low during the low-frequency "break-in" I did before performing the t/s parameter tests, another good sign (for the record, I'm not a believer in having to "break-in" a subwoofer, but doing so costs nothing and avoids getting into any arguments afterwards with the believers about proper break-in before testing, LOL). Other physical attributes worth mentioning are the basket structure, which appears to be very sturdy but unfortunately does not offer any visibility of what's going on below the spider, and the rubber trim ring, which is made of two parts, both of which are removable.

In my next post, I'll include some comparison measurements (impedance, frequency response, distortion) with the 12D2s mounted in my existing car audio subwoofer enclosure and then finally some listening tests.
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Old 04-04-2013   #2
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Default Re: Alpine Type R 12D2

Ok, measurement time. First is a comparison of the measured parameters of the new drivers in my subwoofer box.

Here are the measured parameters with the Infinity 122.7W drivers installed:

R=2.2 Ohms
Fs = 34.3 Hz
Qb = 0.99
Le = 1.97 mH


...and here are the parameters with the Alpine Type R 12D2 drivers installed:

Re = 1.90 Ohms
Fs = 37 Hz
Qb = 0.67
Le = 1.521 mH

The resonance frequency has increased, but the Qb has gone down significantly. Theoretically this should result in a tighter bass sound, but bear in mind we are talking about pretty low frequencies here.

The more significant differences showed up in the FR/distortion plots (see attached). For this test, I basically opened all of the doors and the trunk (to reduce the effect of the Car audio transfer function), set the volume to my casual listening level, then used HolmImpulse and an ECM8000 mike suspended about a foot from the subwoofer to measure the FR and distortion. The FR/distortion curves for the 122.7Ws are displayed in blue, and the FR/distortion curves for the 12D2s are displayed in red. The graph shows that the output of the two drivers remains the same between 50 and 70 Hz. Below 50 Hz the 122.7Ws have a bit more output for the same input voltage, while above 70 Hz the 12D2s have a bit more output. Nothing that can't be addressed (if it actually needs to be) by a bit of EQ and perhaps a slight gain adjustment on the subwoofer amp. However, look at the distortion plots. Apart from a bump around 40 Hz (which is close to the resonance frequency of the 12D2s mounted in the enclosure), the measured THD for the 12D2s is 5 to 7dB lower than the 122.7Ws. And I expect this difference will only increase at higher volumes, as the 12D2s were nowhere near their rated Xmax during this test. Theoretically, this should amount to a cleaner-sounding sub, particularly at lower frequencies and higher volumes. Of course, whether or not that difference is actually audible depends however on how sensitive you are to distortion, and how much of that distortion is masked by road noise and everything else that contributes to what you actually hear when listening to your Car audio system.

Subjective listening results next.
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Old 04-04-2013   #3
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Default Re: Alpine Type R 12D2

Good job with your testing! I look forward to reading more.

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Old 04-04-2013   #4
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Default Re: Alpine Type R 12D2

Ok, I may have to split the results of my subjective listening tests into two or three posts, for reasons that I will shortly make clear.

To start off, I'm not going to wax on eloquently about how with this new subwoofer the bass sounds so much clearer for this tune or I can now hear what pick the bass guitarist is using in that tune and so on and so forth. I believe that a lot of those types of "reviews" are mostly bullcrap IMO. Furthermore, you can't just swap one subwoofer in your system for another and just expect the best results - you also need to check to see if the filter, time alignment and gain settings need to be adjusted accordingly to match the new subwoofer's characteristics.

Having said all of that, I'll give you my first impressions of the 12D2's performance at normal listening levels: very, very good. I still have to make a few adjustments to some of the settings as indicated above, but the impression I was left with is a very good one. I expect that it will only get better after I've used HolmImpulse and a mic to ensure the best blend I can get between the midbass output from my main speakers and the low frequency output from my upgraded subwoofer system.

So, having done a few preliminary tests at normal listening levels, I decided to crank up the volume a bit to see how it performed at "weekend exhibition" levels. Basically I put on Da Mavrik's "When Da Bass Goes Boom (Original Mix)", upped the sub level from -6 to 0 and engaged the "Loudness" option on the deck (a Premier 980BT) and then cranked the volume from 30 to 50. And HOOOLLLEEE-E-SH*T, the bass certainly did go BOOM! Unfortunately it went BLAAAAT! shortly afterwards. Nope, I don't think anything went wrong with the 12D2s. Results of a quick preliminary diagnosis suggests that perhaps replacing two drivers with a total of about 24mm of linear throw with ones that provide a total of 40mm and then tossing 1200W at them was a little too much for the fiberglass enclosure to bear. From the sound of it, it appears that either one of the internal reinforcement bars I built into the enclosure has broken loose or perhaps the enclosure itself is cracked. Hmm. I'll have to pull it out this weekend to see what the damage actually looks like. Until then, any further listening tests will just have to wait.

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Old 04-05-2013   #5
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Default Re: Alpine Type R 12D2

You felt the terror of the VBA!!!! LOL!!!! Sorry to hear that your enclosure didn't hold up Brian. No bueno!

The low level listening results were interesting to read though. I've always wondered how these subs would do in a critical listening environment. I'll also be curious to hear exactly what happened with the sub enclosure. Do keep us informed please.

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Old 04-05-2013   #6
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Default Re: Alpine Type R 12D2

Quote:
Originally Posted by Boostedrex View Post
You felt the terror of the VBA!!!! LOL!!!! Sorry to hear that your enclosure didn't hold up Brian. No bueno!

The low level listening results were interesting to read though. I've always wondered how these subs would do in a critical listening environment. I'll also be curious to hear exactly what happened with the sub enclosure. Do keep us informed please.

Cheers,

Zach
I removed the drivers and hauled out the box this morning. There are some what seems to be stress cracks at the bottom and I think one of the braces to the rear may have come loose from the baffle (difficult to tell because of where it is). I suspect what I was hearing was the bottom of the box slapping against the sheet metal in the spare tire well because the brace came loose and that section was vibrating more than normal. I'm going to secure the brace with a screw or two for the moment and hope that makes it usable for now. I suspect though that for the best results I will have to Build a more sturdy enclosure.

The 12D2s should be fine for lower level listening IMO. The response curves I posted earlier suggest smooth response and very low distortion. Just get the transition between sub and midbass right and they should disappear and not call attention to themselves - unless you crank them up, of course . I've used EQ to add a dB or two at 30 Hz and below to flatten the measured in-car response. I suspect that a vented alignment with these drivers might be a better match for my Car and might just Build my next box with that in mind.

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Old 04-06-2013   #7
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Default Re: Alpine Type R 12D2

Some pictures (just because...)

The first picture shows the Infinity 122.7W (left) vs the Alpine Type R 12D2 (right). Most of the 122.7's "motor" is a heatsink for the neo magnet structure. The Type R's motor is totally enclosed by its aluminium basket. It's quite a bit deeper than the 122.7W, but that doesn't matter for my needs.

The second picture was taken partway through the installation process. The top part of the trim ring is missing from the 12D2 on the right. The enclosure is a fiberglass and wood box that fits into the spare tire well of my Tucson.
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Old 04-07-2013   #8
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Default Re: Alpine Type R 12D2

Russian avtozvuk.com tested the SWR-12D4. There were two important findings. Claimed T/S parameters are very close to measured. Second, THD is very low, with subwoofer reaching 5% THD at much lower frequencies than other subwoofers from the same test (given some fixed voltage I assume).


They got 30.9Hz resonance frequency for the D4 model. The test of 10 inch model also will be online soon.

12 . Alpine SWR-12D4 - avtozvuk.com
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Old 04-08-2013   #9
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Default Re: Alpine Type R 12D2

Quote:
Originally Posted by ZAKOH View Post
Russian avtozvuk.com tested the SWR-12D4. There were two important findings. Claimed T/S parameters are very close to measured. Second, THD is very low, with subwoofer reaching 5% THD at much lower frequencies than other subwoofers from the same test (given some fixed voltage I assume).


They got 30.9Hz resonance frequency for the D4 model. The test of 10 inch model also will be online soon.

12 . Alpine SWR-12D4 - avtozvuk.com
Nice. Those findings mirror my experiences with my 12D2s. The lower distortion is quite interesting, particularly as I think the lower distortion should help with system integration, allowing greater bass output without it audibly sounding like it's coming from the rear. A lot of attention needs to be paid to the enclosure (and damping any panels prone to vibration) to take advantage of this though. I'm seriously considering taking replacing my fiberglass enclosure with a properly-reinforced MDF one for this reason.

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Old 04-09-2013   #10
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Default Re: Alpine Type R 12D2

That confuses me a bit Brian. Fiberglass will be stronger than MDF while remaining thinner and lighter. Just lay it up where it doesn't have any large flat areas and you'll be good to go. Though I'm sure you're no rookie at laying glass. I avoid MDF as much as possible because fiberglass is so much stronger and easy to mold to specialized shapes.

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Old 04-09-2013   #11
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Default Re: Alpine Type R 12D2

Quote:
Originally Posted by Boostedrex View Post
That confuses me a bit Brian. Fiberglass will be stronger than MDF while remaining thinner and lighter. Just lay it up where it doesn't have any large flat areas and you'll be good to go. Though I'm sure you're no rookie at laying glass. I avoid MDF as much as possible because fiberglass is so much stronger and easy to mold to specialized shapes.
In that case my glassing skills suck, LOL. I just seem to get better results with your basic heavily braced wooden box...

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Old 04-10-2013   #12
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Default Re: Alpine Type R 12D2

Fair enough.

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Old 05-17-2013   #13
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Default Re: Alpine Type R 12D2

My apologies if I missed it but how many cubes is your enclosure? A friend of mine is getting a 12" type R and wants to know what's the ideal sized sealed enclosure. Thanks
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Old 05-19-2013   #14
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Default Re: Alpine Type R 12D2

Quote:
Originally Posted by Boostedrex View Post
That confuses me a bit Brian. Fiberglass will be stronger than MDF while remaining thinner and lighter. Just lay it up where it doesn't have any large flat areas and you'll be good to go. Though I'm sure you're no rookie at laying glass. I avoid MDF as much as possible because fiberglass is so much stronger and easy to mold to specialized shapes.
I don't mean to hijack this thread, but there's some good reasons to use MDF *and* fiberglass. Here's why:

When you make a loudspeaker enclosure, you basically have two ways to make it work properly. The first way is to make the walls strong enough that they don't flex. For instance, you could use 1.5" MDF, and it will flex less than 3/4" MDF.

But there's another approach that works too, which is to have a stiff layer, then a soft layer, and then a stiff layer. What happens is that the stiff layer flexes, and the soft layer absorbs the energy.

This is constrained layer damping, and with this approach you can create a material that is better damped than lead.(!)

I've been following this approach for a few years now, and it seems to work well. I stole this idea from Geddes, who used this construction on the Summas that he built for me. (My Summas are carbon fiber - MDF - carbon fiber.)

I use this on my bikes too. Very time consuming, but effective.

One of these days I'm going to try replacing the MDF with cardboard. Basically make a poor man's version of Nomex. (The wheels on my bicycle are carbon fiber - cardboard - carbon fiber.)

It might seem a bit silly to use foam or cardboard in a loudspeaker enclosure, but it's really effective. By themselves, they're not ideal, but sandwich them together and they're greater than the sum of their parts.

The Airbus A380 is also built with the same construction. (fiberglass-aluminum-fiberglass-aluminum-fiberglass-aluminum-fiberglass)

In principle it would be quite simple to waste the surplus labour of the world by building temples and pyramids, by digging holes and filling them up again, or even by producing vast quantities of goods and then setting fire to them. (Orwell)
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Old 07-30-2013   #15
 
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Default Re: Alpine Type R 12D2

Quote:
Originally Posted by Golden Ear View Post
My apologies if I missed it but how many cubes is your enclosure? A friend of mine is getting a 12" type R and wants to know what's the ideal sized sealed enclosure. Thanks
bumping for this.

Quote:
Originally Posted by Patrick Bateman View Post


I don't mean to hijack this thread, but there's some good reasons to use MDF *and* fiberglass. Here's why:

When you make a loudspeaker enclosure, you basically have two ways to make it work properly. The first way is to make the walls strong enough that they don't flex. For instance, you could use 1.5" MDF, and it will flex less than 3/4" MDF.

But there's another approach that works too, which is to have a stiff layer, then a soft layer, and then a stiff layer. What happens is that the stiff layer flexes, and the soft layer absorbs the energy.

This is constrained layer damping, and with this approach you can create a material that is better damped than lead.(!)

I've been following this approach for a few years now, and it seems to work well. I stole this idea from Geddes, who used this construction on the Summas that he built for me. (My Summas are carbon fiber - MDF - carbon fiber.)

I use this on my bikes too. Very time consuming, but effective.

One of these days I'm going to try replacing the MDF with cardboard. Basically make a poor man's version of Nomex. (The wheels on my bicycle are carbon fiber - cardboard - carbon fiber.)

It might seem a bit silly to use foam or cardboard in a loudspeaker enclosure, but it's really effective. By themselves, they're not ideal, but sandwich them together and they're greater than the sum of their parts.

The Airbus A380 is also built with the same construction. (fiberglass-aluminum-fiberglass-aluminum-fiberglass-aluminum-fiberglass)
very interesting. how about using a material like Vibraflex as soft (well, kind of) layer?. easier to mold following the (usually) curved surfaces of a car's trunk, just like fiberglass does.

Last edited by mosca; 07-30-2013 at 11:31 AM..
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Old 07-30-2013   #16
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Default Re: Alpine Type R 12D2

Quote:
Originally Posted by mosca View Post
bumping for this.
The 12D2s probably see around 1.3~1.5 cu.ft. each in my enclosure. I've modded it a few times over the years since I built it.

I'm resisting the temptation to see how they'd perform in a vented alignment...

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Old 07-30-2013   #17
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Default Re: Alpine Type R 12D2

Quote:
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In that case my glassing skills suck, LOL. I just seem to get better results with your basic heavily braced wooden box...
Me too. And I overbuild my fiberglass boxes, but compared to MDF boxes, they almost always seem to "ring" a bit. Deadening helps some, but seems like an unecessary step vs. MDF.

If I don't HAVE to use 'glass, I prefer not to.

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Default Re: Alpine Type R 12D2

Quote:
Originally Posted by Brian Steele View Post
The 12D2s probably see around 1.3~1.5 cu.ft. each in my enclosure. I've modded it a few times over the years since I built it.

I'm resisting the temptation to see how they'd perform in a vented alignment...
thanks. that is more than I expected, as Alpine recommends 0.75 cu.ft. net (I haven't modeled it yet).


PS: I love your site!
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Old 08-01-2013   #19
 
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Exclamation Re: Alpine Type R 12D2

Quote:
Originally Posted by Patrick Bateman View Post
It might seem a bit silly to use foam or cardboard in a loudspeaker enclosure, but it's really effective. By themselves, they're not ideal, but sandwich them together and they're greater than the sum of their parts.
http://www.diyaudio.com/forums/full-...nclosures.html

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Default Re: Alpine Type R 12D2

I ditched MDF for baltic birch years ago and never looked back. Not the Home Depot crap, but the kind you get from a real lumber yard or a cabinet shop. Lighter, easier to work with and won't turn to shit if you spill something in your trunk and it soaks in.
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Old 08-11-2013   #21
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Default Re: Alpine Type R 12D2

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Originally Posted by Patrick Bateman View Post
[font=verdana]

But there's another approach that works too, which is to have a stiff layer, then a soft layer, and then a stiff layer. What happens is that the stiff layer flexes, and the soft layer absorbs the energy.

This is constrained layer damping, and with this approach you can create a material that is better damped than lead.(!)
Does anyone here remember Dynaboard? It was two layers of wood with a layer of deadener in between. It seems as tho it might come under this heading (constrained layer damping), and might be quite effective. I've never used it, and it seems to be no longer available, but I was wondering if anyone else had used it and what were the results?

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Old 08-11-2013   #22
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I remember it. Dynamic Control made it. I've never heard of it being used, but I imagine it would be pretty good.

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Old 09-21-2014   #23
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Default Re: Alpine Type R 12D2

I thought I'd provide an 18-month update on these drivers.

So far they continue to perform as well as they did when I originally installed them back in April 2013. Just lots of nice clean bass, and when I crank it up, the Car and the enclosure are giving up before the subwoofers do.

If there is any cone-sag (I have them mounted facing up), it's not noticeable. My previous drivers (Infinity 122.7Ws) weren't too bad in this regard either. However my JBL 1200Gtis sagged noticeably, to the point I had to flip them over so they could start to sag in the other direction.

Any changes have been basically cosmetic in nature. The two-piece rubber trim ring's faded and a bit discoloured (and it is not exposed to direct light), but that's nothing a bit of protectant like Armor-All can bring back to life (see attached image). The trim ring, in particular the upper part, is probably the only thing I'm not too fond of about this sub - it tends to pop out a bit too easily. It would be nice if it was made out of a hard plastic or metal instead. The drivers themselves continue to function well, and yes, they have been subject to occasional "abuse"
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Old 09-22-2014   #24
 
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Default Re: Alpine Type R 12D2

Nice clean install!

2001 Ford F150 XLT SuperCrew 5.4L 2wd, Jensen VX7020, Boston Acoustic GT-42, Kicker KS68's, Power Acoustik BAMF 5500/1D, 2 Polk Audio MM1540DVC's in 3.25ft Sealed.
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Old 09-22-2014   #25
 
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Thumbs up Re: Alpine Type R 12D2

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Originally Posted by Brian Steele View Post
I'm resisting the temptation to see how they'd perform in a vented alignment...
I vote for a tapped horn!

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