# JBL w10gti & w15gtimk2



## npdang (Jul 29, 2005)

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 1-33 rev3.pdf Definitely interesting stuff, and I highly recommend browsing through the white paper.


























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.










































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 



















































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


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## kappa546 (Apr 11, 2005)

*Re: JBL w10gti*

hmmm... i expected better. considerably


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## Rbsarve (Aug 26, 2005)

*Re: JBL w10gti*

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)


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## 300Z (Mar 20, 2005)

*Re: JBL w10gti*

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. 
I also expected a bit better.


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## bdubs767 (Apr 4, 2006)

*Re: JBL w10gti*

hmmm the newer GTI is different I have...

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


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## npdang (Jul 29, 2005)

*Re: JBL w10gti*

Hmm I thought you were gonna send it


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## bdubs767 (Apr 4, 2006)

*Re: JBL w10gti*



npdang said:


> 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?


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## npdang (Jul 29, 2005)

*Re: JBL w10gti*

Yeah sendem both. I forgot about that


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## legend94 (Mar 15, 2006)

*Re: JBL w10gti*



300Z said:


> 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.
> 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


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## bdubs767 (Apr 4, 2006)

*Re: JBL w10gti*



legend94 said:


> 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



Guess well find out....


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## DS-21 (Apr 16, 2005)

*Re: JBL w10gti*

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!


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## bassfromspace (Jun 28, 2016)

*Re: JBL w10gti*



DS-21 said:


> 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!!!!!!! 

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.


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## kappa546 (Apr 11, 2005)

*Re: JBL w10gti*

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


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## 300Z (Mar 20, 2005)

*Re: JBL w10gti*



legend94 said:


> 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


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


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## 300Z (Mar 20, 2005)

*Re: JBL w10gti*

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? 
Published specs PDF .


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## DS-21 (Apr 16, 2005)

*Re: JBL w10gti*



300Z said:


> 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.


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## npdang (Jul 29, 2005)

*Re: JBL w10gti*

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


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## 300Z (Mar 20, 2005)

*Re: JBL w10gti*

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


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## npdang (Jul 29, 2005)

*Re: JBL w10gti*

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.


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## chad (Jun 30, 2005)

*Re: JBL w10gti*



legend94 said:


> 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


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


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## Guest (Apr 25, 2007)

*Re: JBL w10gti*

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.


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## thehatedguy (May 4, 2007)

*Re: JBL w10gti*

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.




legend94 said:


> 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


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## Neil (Dec 9, 2005)

*Re: JBL w10gti*



werewolf said:


> 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.


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## Guest (May 10, 2007)

*Re: JBL w10gti*



Punk0Rama said:


> 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.


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## npdang (Jul 29, 2005)

*Re: JBL w10gti*

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


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## Neil (Dec 9, 2005)

*Re: JBL w10gti*



werewolf said:


> "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.


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## kappa546 (Apr 11, 2005)

*Re: JBL w10gti*



npdang said:


> 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?


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## npdang (Jul 29, 2005)

*Re: JBL w10gti*

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.


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## Guest (May 11, 2007)

*Re: JBL w10gti*



Punk0Rama said:


> 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


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## JAG (May 6, 2006)

*Re: JBL w10gti*

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 .... 
Once again I'll say : What does a spec sound like ?


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## Guest (May 20, 2007)

*Re: JBL w10gti*



AVI said:


> 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 ....
> 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?


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## JAG (May 6, 2006)

*Re: JBL w10gti*



werewolf said:


> 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.
> 
> ...


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.


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## Guest (May 20, 2007)

*Re: JBL w10gti*

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


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## Guest (May 20, 2007)

*Re: JBL w10gti*



AVI said:


> 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.


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## DS-21 (Apr 16, 2005)

*Re: JBL w10gti*

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.


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## npdang (Jul 29, 2005)

*Re: JBL w10gti*

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.


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## Neil (Dec 9, 2005)

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.


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## DS-21 (Apr 16, 2005)

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)


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## Neil (Dec 9, 2005)

DS-21 said:


> *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?


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## JAG (May 6, 2006)

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 ****.
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 ...


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## DS-21 (Apr 16, 2005)

AVI said:


> 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 ****.


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.


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## DS-21 (Apr 16, 2005)

Punk0Rama said:


> 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.


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## Neil (Dec 9, 2005)

DS-21 said:


> 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.)
> ...


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


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## npdang (Jul 29, 2005)

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...


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## JAG (May 6, 2006)

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 ****. Literally everything EVER made by Krell sounds like pure **** , 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 **** to me , yet measure just fine ....
Rockford Fosgate amps sound like **** 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 !


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## DS-21 (Apr 16, 2005)

AVI said:


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


********. 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 ****. Literally everything EVER made by Krell sounds like pure **** , 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 !


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


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## JAG (May 6, 2006)

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


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## Guest (Jun 20, 2007)

*Re: JBL w10gti*



werewolf said:


> 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  

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 (Apr 11, 2005)

*Re: JBL w10gti*

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?


----------



## Guest (Jun 20, 2007)

*Re: JBL w10gti*



kappa546 said:


> 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 (Apr 11, 2005)

*Re: JBL w10gti*

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 (Apr 11, 2005)

*Re: JBL w10gti*

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 (Jul 24, 2006)

DS-21 said:


> ********. 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 (Apr 16, 2005)

kappa546 said:


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


I'd hit that!



Luke352 said:


> 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 ****s 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 ****! 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 (Dec 9, 2005)

*Re: JBL w10gti*



kappa546 said:


> 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 (Apr 11, 2005)

*Re: JBL w10gti*



Punk0Rama said:


> 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 (Dec 3, 2007)

*JBL w15gtimk2 and JL 13W7*

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 (Jun 28, 2016)

*Re: JBL w15gtimk2 and JL 13W7*



chrismercurio said:


> 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 (Dec 3, 2007)

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 (May 1, 2007)

*Re: JBL w10gti*

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 (Mar 2, 2007)

*Re: JBL w10gti*



johnson said:


> 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 (Apr 11, 2005)

*Re: JBL w10gti*



gbraen said:


> 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 (Mar 20, 2005)

*Re: JBL w10gti*



kappa546 said:


> 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 (Jun 30, 2005)

*Re: JBL w10gti*



300Z said:


> altho two different beasts.
> 
> Leo


Egg-Zachary


----------



## gbraen (Mar 2, 2007)

*Re: JBL w10gti*



kappa546 said:


> 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 (Jul 24, 2006)

*Re: JBL w10gti*



gbraen said:


> .
> 
> 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 (Mar 2, 2007)

*Re: JBL w10gti*



Luke352 said:


> 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 (Apr 11, 2005)

*Re: JBL w10gti*

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 (May 4, 2007)

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 (Jun 30, 2005)

thehatedguy said:


> 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 (Jul 24, 2006)

chad said:


> 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 (Mar 2, 2007)

Luke352 said:


> 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 (Feb 8, 2007)

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 (Feb 27, 2008)

innsanes said:


> 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 (Mar 2, 2007)

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 (Apr 11, 2005)

from "sucks" to "absolutely fantastic"


----------



## gbraen (Mar 2, 2007)

kappa546 said:


> from "sucks" to "absolutely fantastic"


Sucks in sealed, excellent in ported enclosure, yes!


----------



## chad (Jun 30, 2005)

gbraen said:


> Sucks in sealed, excellent in ported enclosure, yes!


It's a JBL


----------



## trunks9_us (Oct 25, 2007)

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.



gbraen said:


> Sucks in sealed, excellent in ported enclosure, yes!


----------



## DS-21 (Apr 16, 2005)

chad said:


> It's a JBL


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


----------



## chad (Jun 30, 2005)

DS-21 said:


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


It'll blow up 

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


----------



## backwoods (Feb 22, 2006)

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 (Jun 30, 2005)

backwoods said:


> 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


----------



## chrismercurio (Dec 3, 2007)

*Re: JBL w10gti & w15gtimk2 - Bump*

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 (Mar 5, 2008)

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


----------



## tommyd (Nov 7, 2007)

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


----------



## 14642 (May 19, 2008)

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 (May 27, 2008)

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 (Oct 25, 2007)

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 (Oct 25, 2007)

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 (Oct 29, 2007)

trunks9_us said:


> 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 (Oct 25, 2007)

tcguy85 said:


> 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 (Jul 29, 2005)

They are 4 ohm subs, for your purposes.


----------



## trunks9_us (Oct 25, 2007)

npdang said:


> They are 4 ohm subs, for your purposes.


ygpm


----------



## trunks9_us (Oct 25, 2007)

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 (Jul 29, 2005)

Andy Wehmeyer said:


> 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 (Apr 6, 2006)

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 (Dec 9, 2005)

Andy Wehmeyer said:


> 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.


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## trunks9_us (Oct 25, 2007)

npdang said:


> They are 4 ohm subs, for your purposes.


so if there 4 ohm subs then... how would this work if I want to use a 2 chan amp and wire it in stereo on each voice coil. what ohm loads would each voice coils be at? The idea is to run the amp at a 4 ohm load for best sq wise. I am looking a damping factor here in this case.


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## npdang (Jul 29, 2005)

It's been my experience that the more complicated the design, the more production variance you tend to see.


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## Ricci (Sep 30, 2008)

Like Npdang has said whenever you complicate the design or production of something, the easier it is to have variance in the final product. I don't see anything that would point to the Klippel system being somehow unable to correctly measure a DD based woofer, or split coil, or LMS, or XBL2. They may have differences in the design but the goals and basic operation are the same for any woofer regardless of the differences. It is still a cone, surround, spiders, magnets and wire on a tube having current run through it. The inductance is still very low on these and they should have a flat and extended upper bass fr. The thermal power handling is pretty good as well due to all of the heat sinking, venting and coil mass. I don't personally have one of these but I've heard that the dynamic braking action of the coils prevents the sub from damaging itself through overexcursion quite well. Minor variation in the winding of the vc's has a very large affect on the performance.


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## 14642 (May 19, 2008)

Hey Guys,
Sorry I forgot about this thread. I've spent Christmas trying to recover from a big hard drive crash and in rescuing a bunch of files, I came across an old folder of documentation from theoriginal development of GTi Subs. Later in January, I'll talk to Jerry, the engineer who designed these subs about this Klippel thing. I recall he remarked about the difference in results from measuring with Klippel and other measurement methods. I'm sure he has a file of stuff somewhere. 

In the mean time, here's a distortion plot of the driver, measured in half-space in the recommended sealed box mounted in the floor of one of the anechoic chambers. Note that the measurement was made at 35V. It's worth noting that coil out of the gap conditions typically produce a rise in odd-order distortion. However, coil out of the gap in the W15 is a little different. Because the coils are offst toward the center of the former, it's an asymetrical condition, which raises 2nd order distortion. Even the second order distortion is quite a bit lower than many conventional designs. In any case, we made similar measurements for other speakers which were popular at the time, and I'll see if I can dig those up soon. 















Also, Here's a photo of the two coils on the former. They're single-layer copper-clad aluminum edge wound and the wire is milled specifically for this driver. There isn't a lot of mass here, but the top plates include an additional steel lip for heat sinking. Also, the holes in the former have been removed in production to add additional airflow over the coils.


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## Ricci (Sep 30, 2008)

Thanks for the photo Andy. Can you elaborate on the process that JBL, or Harmon as a whole uses to develop drivers and arrive at the production specs? Is the xmax still determined by the overhang calculation? Is a different method used for the DD drivers?


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## 14642 (May 19, 2008)

For JBL car products, "Xmax" is linear, one-way and determined strictly by measuring overhang. We don't include any +10% fudge factor like some other companies do. 

We have many different methods for driver development, depending on the brand, the application, the cost and the performance reauirements. The W-series GTi speakers--well...all the GTi speakers have been designed by a specific transducer engineer. The GTi woofers are a car-audio adaptation of the DD found in JBL Pro speakers, but because of the popularity of sealed boxes for cars the design was dramatically changed to provide greater Xmax.

Some of the principles and procedures we use are explained in the owner's manual/brochures for the GTi speakers, which can be found on www.JBL.com


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## 14642 (May 19, 2008)

Yes, you can run a separate amplifier oneach coil, but the voltage and drive ought to be precisely matched to avoid introducing distortion. 

When the woofer moves in, the air in the box is compressed. When the woofer moves out, the air in the box is rarefied. The result is force of the same magnitude in either direction. 

The coils and gaps are identical but opposite. That reduces nonlinearity by canceling. 

Finally, the wire is milled so we can have precisely the right number of turns in the gap and maintain a single layer of wire.


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## trunks9_us (Oct 25, 2007)

Andy Wehmeyer said:


> Yes, you can run a separate amplifier oneach coil, but the voltage and drive ought to be precisely matched to avoid introducing distortion.
> 
> When the woofer moves in, the air in the box is compressed. When the woofer moves out, the air in the box is rarefied. The result is force of the same magnitude in either direction.
> 
> ...



Andy do you have any idea what the ohms would be on each coil by itself? I am guessing 3 ohms which is more close to 4 ohm given dc resistance, but would like to know for sure? The goal would be to run a zapco 4.0 bridge at 4 ohms which makes 2x300rms at 4 ohms on the gti. That would give me a total of 600 rms using a IB setup which should be enough to take it to the mechanical limits. Of course I could be wrong. My only other choice is to run a 6.0 or 9.0 at 2 ohms on 2 gti's to make enough power for the subs. Then I am losing half my damping factor as well as T.H.D. + Noise. Its not a huge deal for me but would like to know what my options are.


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## Oliver (Jun 25, 2007)

I believe it is 6 ohms per coil , thus allowing a 12 ohm series connection and a 3 ohm parallel connection.


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## SteveH! (Nov 7, 2005)

andy, is ther any benefit to doing dual 6 ohm voicecoils instead of the more common dual 2 or dual4 ohm voicecoils. i'm concerned how my amps will the 3ohm load.


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## trunks9_us (Oct 25, 2007)

Autiophile said:


> You don't need to guess, just read the spec sheets.
> 
> The Re in parallel is 2.95 ohms in parallel for the w15gti, so that should mean 5.9 ohms per coil. Pretty spot on with the nominal rating of 6 ohms.
> 
> Don't worry so much about THD and Damping factor. THD is not the most meaningful specification and at low frequencies becomes even less important because we are less sensitive to small amounts of distortion in that frequency range.


So correct me if I am wrong then. If I was to get 2 of these w15gti's and Was running the 1.5 ohm load I would want max power at a 2 ohm stable amp b/c the dc resistance will go up and not lower then 2.95. I am planning on getting the 2 ohm version then of the 9.0 unless I can manage to put 3 w15gtis for my IB setup might have to go down to 3 12's who knows.


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## 14642 (May 19, 2008)

Just apply as much power as possible and as Autophile wrote, do't may much attention to THD and Damping Factor--especially damping factor. Amps don't control damping.


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## ashlar (Dec 4, 2008)

If Damping Factor and THD are not important specs then why did JBL market it heavily in their 2003 press release of the A6000GTI. It seemed important enough back then in 2003. 

My takeaways:-

"combined with damping nearly 40 times higher and distortion significantly lower than that of conventional Class D subwoofer amplifiers."

"the A6000GTi boasts an industry-leading damping factor of >1000, more than an order of magnitude lower than many Class D subwoofer amplifiers currently available, and THD of .05% @ 4 ohms. The dramatically reduced distortion, compared to that of conventional Class D switching amplifiers, is the product of Crown’s proprietary and patented Balanced Current Amplification circuit (BCA), which also provides efficiency superior to that of Class D."

http://manuals.harman.com/JBL/CAR/Press Releases/JBL A6000GTi Amplifier Press Release.pdf

This was a JBL/Crown approved press release.


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## 14642 (May 19, 2008)

Hundreds of years ago, the best science in existence indicated that the world was flat. We all get to learn, right? There is a benefit in low output impedance, but it isn't in driver control.

My point to trunks9 is that the benefits of low distortion in a sub amp and low output impedance aren't a good trade off for less power. 

Here's a link to a well written explanation of why damping factor isn't a usefu spec, no matter what marketing departments write in press releases. This will save me from spending yet another hour typing this information, which I've already typed twice on this forum. 
Damping Factor: Effects On System Response — Reviews and News from Audioholics

Additionally, the GTi amplifiers include a feedback circuit that connects to the output terminals of the amplifier to negate the effects of the amp's output impedance. This circuit and the BCA circuit are also included in the A3000GTi (out of production), whic was a full range amplifier--low distortion is a benefit at higher frequencies.


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## Ricci (Sep 30, 2008)

Andy,

This is a bit off of topic, but I figured since you are an insider at a respected audio company you'd be a good person to ask. I was talking to a guy about driver design a few days ago and we are wondering why there isn't an emphasis on light weight drivers like there is in the pro audio field? These days Pro audio 15 and 18" drivers routinely weigh less than 30 or even 20lbs sometimes mainly through the use of a neo magnet based motor. Some of the subwoofers these days are up over 80lbs. Why aren't there more neo based motor designs for mobile audio? Granted the apps are somewhat different and neo is more expensive but they are not that different. There are virtually only a handful of lightweight neo based sub drivers designed with mobile audio in mind. Take JBL as an example the W15Gti weighs what, 42lbs( that ain't too bad these days)? The 2269H 18" weighs well under 30lbs and it is a bigger driver with a 4" vc and is better in nearly every respect. Of course it is also more expensive and designed for a different app, but you see my point. A 2268 is also much lighter than a W15Gti. Is neo so expensive, difficult to manufacture a motor with, or unreliable due to thermal demagnetization, or atmospheric conditions? I find this hard to believe since the pro audio woofers are also subjected to very harsh use involving extended high power use and greatly changing temperature and humidity. It's not like all of the woofers using neo based motors are hideously expensive either. Some of them are under $200. Plus I would expect the Pro audio field to have the highest standards of reliability among JBL's target market segments. Comments?


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## kenk (Feb 27, 2008)

I was thinking the same thing Ricci. As far as I know the wgti design hasn't changed for almost a decade (except new paint scheme and dust cap). Sound quality and power handling is awesome but the weight and length can be improved. I hope they come out with updated neo magnets with dual 4 ohm coils. Only then it could be "the ultimate sub"...


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## OldBloke (Dec 23, 2008)

cajunner said:


> there is no other speaker with the exact same topology, i.e. Orion and CV and SS Davinci


Not in car audio but Velodyne uses a very similar design in their top of the line home subs.


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## cbrunhaver (Jun 28, 2006)

While I have only skimmed all of the replies in this thread, I didn't see mention of the DUMAX report that was done on the previous generation W12gti.

Interestingly, it agrees well with JBL's Xmax figure and you can distinctly see the contribtution of each gap from the biased coils.

http://www.adireaudio.com/Files/JBL W12GTi.pdf

Its cool to have Andy posting here, especially getting a glimpse into the data on products like this (or vehicle transfer fucntions etc.).

Though it is an expensive approach and leads to deep motors structures, I think that this is an ingenious design where you basically get to reuse the same flux twice and have a counter coil dramatically reducing flux modulation and increasing power handling. Though it limits the excursion, the magnetic braking is another benefit (build in limiting). 

I guess my question is, though it would make the driver a lot deeper (and the former really long), why wouldn't you bias the coils away form each other (instead towards each other) to allow more mechanical travel?

In that configuration and using more coil layers (4-8 instead of two), I would image that a driver like this would do a lot better in SPL competition because of the very favorable high power behavior with respect to dynamic offset / flux modulation at very high current levels and high power handling. I know that this wasn't the main application but it would be an interesting twist on the concept.

-Chris


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## Ricci (Sep 30, 2008)

What is interesting is that the Dumax report also shows a forward offset to the BL curve just like the Klippel tests on the GTi's.


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## OldBloke (Dec 23, 2008)

cbrunhaver said:


> In that configuration and using more coil layers (4-8 instead of two), I would image that a driver like this would do a lot better in SPL competition because of the very favorable high power behavior with respect to dynamic offset / flux modulation at very high current levels and high power handling.


I would much rather leave it the way it is and keep the Inductance low with just the 2 layers on the coil, + keeping the power requirements reasonable. There is plenty of high power/SPL drivers out there and not enough SQ minded drivers.


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## 14642 (May 19, 2008)

Klippel this, Dumax that...those two machines are helpful in determining the causes of distortion. The large signal 2nd and 3rd order harmonic distortion graph I posted indicaes that this is STILL one of the lowest-distortion car-audio subwoofers available, if not the one with the LEAST distortion.


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## npdang (Jul 29, 2005)

With very few exceptions, I don't believe that it's necessary to resort to non-quantifiable statements with respect to subwoofer performance... such as we "design our speakers to sound good with music." That maybe true, but is no more useful to someone without firsthand experience than saying we design our cars for the "ultimate driving experience."

One thing I do agree on, is that while Klippel is an indicator of distortion performance, LSI does not however measure distortion performance directly and should not be taken as such. 

However, what is unclear to me is Andy's explanation of why LSI cannot properly measure the DD motor. If one coil has left the gap, hasn't the other entered it? If it hasn't, and BL has in fact dropped off doesn't that signal an increase in distortion? Why would it "defy" traditional metrics of constant BL as a predictor of distortion performance?


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## HCCA (Apr 6, 2007)

Question for npdang, I was wondering if you were able to determin through your testing, what the dynamic power handling of this sub is in a sealed configuration? I'm planning on running a pair of the 12's and have two power options. 350W/ch, or 700W/ch.


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## mbrooky (Feb 22, 2009)

This wouldn't happened to be you selling the w10gti would it:

WTT JBL W15GTI MK2 check it out. - Car Audio Forum - CarAudio.com

JBL W15GTI MK2 for trade! - Car Audio Forum - CarAudio.com


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## Cruzer (Jul 16, 2010)

Bl curves are ugly yet these subs get a Lot of attention


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## cvjoint (Mar 10, 2006)

Cruzer said:


> Bl curves are ugly yet these subs get a Lot of attention


What do you think, the subjective reviewers are unreliable? Miss-testing? Other factors not tested for? Other than the LE this driver is mediocre on the test bench.


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## Cruzer (Jul 16, 2010)

cvjoint said:


> What do you think, the subjective reviewers are unreliable? Miss-testing? Other factors not tested for? Other than the LE this driver is mediocre on the test bench.


Exactly, u said its mediocre, but some people on here say its one of the BEST drivers, that it has the BEST sq, etc.


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## cvjoint (Mar 10, 2006)

I wonder how they reconcile their findings with the data. I wouldn't buy these guys.


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## Oscar (Jun 20, 2010)

I have a W10GTi MkI in a 1.7 ft^3 box (after driver/bracing displacements) tuned to 33Hz. While the measured parameters are off in the "Q" department, the inductance actually comes in lower than what the manual states. Never the less, I went against my gut instinct and ported it when the parameters are typically that of a woofer that excels in a sealed or 4th order bandpass, and I was quite surprised how clean it sounded. For reference, before I used this sub, I started out with Cerwin-Vega Vega124's, then moved on to a RE XXX 12 (the old one). While it cannot compare to the sheer output that the XXX had, it sounds just as good if not better in the SQ dept. And while I have not tested billions of different subwoofers, I do have to agree with Andy (besides seeing the emperical evidence) that this is truly one very low-distortion driver. In fact, I even picked up a second one.


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## Oscar (Jun 20, 2010)

Pic I found and "modified" in Microsoft paint to illustrate how the longitudinally separated windings work with the seperate magnetic field gaps.


The green arrows I added can be thought of the lines of magnetic flux. I don't know if they are in the correct orientation, but none the less, you can see how to complete the circuit, they have to flow in reverse directions across the gaps (arrows pointing Left & Right), and this is why one coil is wound in the opposite orientation than the other, so they can both push up/down, and not cancel each other out.


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## cvjoint (Mar 10, 2006)

I'm pretty sure this differential has more cooling fins than my limited slip  I can see how it would work great in a ported design, power compression becomes more important.


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## adrenalinejunkie (Oct 17, 2010)

Can't believe I went through this whole thread. Now for a simple question.
Is it worth purchasing a JBL W12GTIMK2 and throwing it in a 2.3 cu ft *Net @ 33hz with my amp that does 500 w rms @ 4 ohm(Kicker ZX1000.1D benched at 1225 w rms @ 14.5v 2 ohm stable)?
This is my only concern about this woofer, but the fact that it has a high sensativity makes me think i'll be fine. Feedback would be great. This will be going in my '01 Blazer 4 door (SUV) TIA


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## DAT (Oct 8, 2006)

adrenalinejunkie said:


> Can't believe I went through this whole thread. Now for a simple question.
> Is it worth purchasing a JBL W12GTIMK2 and throwing it in a 2.3 cu ft *Net @ 33hz with my amp that does 500 w rms @ 4 ohm(Kicker ZX1000.1D benched at 1225 w rms @ 14.5v 2 ohm stable)?
> This is my only concern about this woofer, but the fact that it has a high sensativity makes me think i'll be fine. Feedback would be great. This will be going in my '01 Blazer 4 door (SUV) TIA



It can handle lots of power, I had a friend that use 4 in his car with a JBL A3000 amp on them and they didn't break a sweat. Never killed a sub.


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## optimaprime (Aug 16, 2007)

so i have read this and some of it is over my head, with all the graphs aside how does it sound ? compared to w10w7 or id12v3, or some of the other high end subs? i see it beening used alot and it is interesting sub.


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## DAT (Oct 8, 2006)

optimaprime said:


> so i have read this and some of it is over my head, with all the graphs aside how does it sound ? compared to w10w7 or id12v3, or some of the other high end subs? i see it beening used alot and it is interesting sub.


I use 10" JBL GTI's in my setup... Incredible..


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## optimaprime (Aug 16, 2007)

wow that must rattle teeth filllings !!1


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## chad (Jun 30, 2005)

Irrelevant... but.. I liked the black dust domes soooo much better.


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## danno14 (Sep 1, 2009)

DAT said:


> I use 10 JBL GTI's in my setup... Incredible..


Wow! Which model and in what enclosure?


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## DAT (Oct 8, 2006)

danno14 said:


> Wow! Which model and in what enclosure?


Sorry I mean to say I have 10" Gti's , not 10 GTi's

hahaha

and I use them in a Sealed box


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## optimaprime (Aug 16, 2007)

what you think of them dat?


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## subwoofery (Nov 9, 2008)

optimaprime said:


> what you think of them dat?





DAT said:


> I use 10" JBL GTI's in my setup... *Incredible*..


Kelvin


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## BigRed (Aug 12, 2007)

cvjoint said:


> What do you think, the subjective reviewers are unreliable? Miss-testing? Other factors not tested for? Other than the LE this driver is mediocre on the test bench.


this driver was tested by George and came out as one of the lowest distortion subs he ever tested. check out his socal test bin thread


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## danno14 (Sep 1, 2009)

Anyone know if a 12" was ever tested.... Along the same lines?


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## cvjoint (Mar 10, 2006)

BigRed said:


> this driver was tested by George and came out as one of the lowest distortion subs he ever tested. check out his socal test bin thread


Box design + transfer function + subwoofer.


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## subwoofery (Nov 9, 2008)

BigRed said:


> this driver was tested by George and came out as one of the lowest distortion subs he ever tested. check out his socal test bin thread


Wish they made a W8Gti, I would be all over that  

Kelvin


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## BigRed (Aug 12, 2007)

cvjoint said:


> Box design + transfer function + subwoofer.


agreed, although I'm not so sure about the transfer function relating to HD


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## GS3 (Feb 19, 2006)

subwoofery said:


> Wish they made a W8Gti, I would be all over that
> 
> Kelvin


^x2

this would help solved alot of headachs for me and probably alot of the sq oriented applications for many others also.


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## thehatedguy (May 4, 2007)

Well, there is a "W8GTi" just that it isn't a sub. JBL has Differential Drive 8" midbasses for the prosond market.

The 218F is one such woofer...2 ohms used in the LSR6328P monitor. That is a ferrite model.

Then you have the 2168H used the the VRX928 array. That is a neo 8 ohm driver.


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## cvjoint (Mar 10, 2006)

BigRed said:


> agreed, although I'm not so sure about the transfer function relating to HD


Well, it's cabin gain, not cabin loss. The transfer function of a car allows you to get higher output for lower excursions than you would get in an open parking lot. It's going to help. 

There is one guy running 2 Pyle 15s. I wonder how those would compare. Enough surface area can place a low enough requirement on the motor for the sub to matter very little.


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## chad (Jun 30, 2005)

thehatedguy said:


> Then you have the 2168H used the the VRX928 array. That is a neo 8 ohm driver.


Well that's 8 ohm, it won't "bang" or "knock my trunk" 

Because my ****'s gotta be balla yo.


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## bassfromspace (Jun 28, 2016)

chad said:


> Well that's 8 ohm, it won't "bang" or "knock my trunk"
> 
> Because my ****'s gotta be balla yo.


Only while hanging with the homies.


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## BigRed (Aug 12, 2007)

tttt


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## smkocheran (Jun 2, 2011)

I currently run a W10GTI MK2 and its a VERY great subwoofer. I only have it in about 1.3ft^3 and it pounds. I got it for around $200 and am extremely impressed


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## Oscar (Jun 20, 2010)

just saw this on the JBL website











Funny, because I thought the MKII WGTi series, like the one I have here, were still ferrite-based. Unless they just recently changed this.


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## eviling (Apr 14, 2010)

Oscar said:


> just saw this on the JBL website
> 
> 
> 
> ...


I never knew that either and the gti's are one of my faverate subs of all times


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## Oscar (Jun 20, 2010)

I think it's a type-o error. With the prices of neodymium having gone through the roof in recent years, I doubt JBL would start using even more of it. I know mine has a ferrite motor for sure, and its a MKII


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