JBL W15gti in home install

[DoctahGonzo]

So I am helping a friend build his own JBL cabinets for his house, and he doesn't speak a lick of english. So here I am helping him get some advice.

The system setup, so far is as this: Unknown receiver to active crossover (dbx 234s most likely) two JBL W15GTI subwoofers, two JBL 2370a horns with JBL 2425H drivers, and two tweeters (unknown what kind just yet) I've put together a few systems before, but this one i am in a bit over my head.

First and foremost, the JBL W15GTI are car subwoofers. Do I need to wire these any differently as opposed to normal subwoofers? Also, they are 6 ohms, and I'm not so sure how to wire these, or which amplifier to get with them. I was planning on wiring these parallel with a final impedance of 3 ohms. I was assuming a 4 ohm stable amp would be good enough. Good idea? Or should i wire them differently? And any suggestions on which amplifier to use?

Lastly, Is the combo of the 2370a horns with 2425H drivers used as mids for the system a good idea. The JBL specification sheet shows that there is a drop-off at around 16 Khz with this combination, so I figured I would get some tweeters by harman or JBL to top off the system. Has anyone else here done or heard anything like this before?

Any input or advice for a newcomer would be greatly appreciated. Thanks guys!!!

[grumpy]

I suspect getting those woofers to sound nice up to 1KHz (or so) and blend well with
the horn will be the bigger challenge.

[Lee in Montreal]

The W15GTi woofs can be used up to maybe 80 Hz I think. Those are infrabass drivers. ;-) They will be a great driver to give you a very physical presence and lotsa thump. Use them in mono crossed at 60/70Hz with a 12db/octave slope. Each coil is 6 Ohm if I am not mistaken. Your choice of 3 Ohms (parallel) or 12 Ohms (serie). Not many home amps will be stable at 3 Ohms, so you may want to go into 12 Ohms. You will need a big ass amp for those.

The comp driver and horn will start at 1KHz like was mentionned earlier

Therefore there's a gap in between. I suggest a 12" driver for the kick. Maybe a 2206. A 15" 2226 will not go to 1000Hz cleanly. Most likely to 650/700Hz at best.

So, with a set of W15GTi, you'll end up with a 3.5 way system. If you want to keep it a 3 way (or rather a 2.5) and keep the W15GTi, then you will need to replace the 2425 comp, 2370 horn and tweeter by a much larger horn that can cover the whole spectrum, from 800Hz to 18Khz. Think 2360 horn and 2441 comp w/ Be diaphragm.

[DoctahGonzo]

I was afraid that the subwoofers wouldn't match up to the horns. The frequency response on the JBL spec sheet says that it is up to 1khz, I guess i will have to start looking for a 12" woofer for this system.

And as for Amplifiers for the system, I am having trouble finding a 4 ohm stable amp. =/ Guess I will wire it in series

[DoctahGonzo]

I'm just going through the crossover points for these speakers. Anyone else have any input on matching up the subwoofers to these horns / another 12" woofer?

[toddalin]

The W15GTi uses two 6 ohm voice coils. They can be wired for 3 ohms or 12 ohms. I use them at 12 ohms.

This is not "just a subwoofer" and is actually as smooth or smoother than a 2235 all the way up past 1 kHz, and extends much lower. Yes, I've done the testing and the results were reported here years ago and should be in archive.

I use four of the W10GTis with 2425 on butt cheeks for my surrounds and they work great. BUT, the efficiency is low and requires a lot of "padding" (attenuation) on the horn. The crossovers for the two way system were also put online at the time with an 800 Hz turnover point. You can use the same crossover for the 15s (they use the same motor assemblies) and there is even a high frequency extension circuit included in the schematic. I even did the testing on both butt cheeks and the 2370a horn you will be using, and there are different resistor values in the crossover when used with the different horns.

[DoctahGonzo]

Okay, I will look around the archives for the testing you speak of, Thanks!

I am really betting the whole lot on these subwoofers covering up to at least 1 Khz, or else the 2370a horns are kinda useless for me.

Anyone have any experience with them and the 2425H?

These horns, as i've been told, don't cover the whole frequency range above the subwoofers. I didn't know that they did not cover the lower end (around 1 Khz.) Am i to assume that i was incorrect in assuming that they would? Like i said, when i looked at the specification sheet, I knew they had a drop off around 16Khz, which was fine if i had to use them as part of a 3 way system with some selenium tweeters.

I'm kinda stuck at the moment just trying to plan this out. Considering selling the 2370a horns on ebay for a slight loss, and trying to buy the 2360.

[Dr.db]

I once tried a 4-way setup with W15gti, E-110, 2445 and 2405...

The GTi run in an 4cubic feet sealed enclosure and was crossed over to the 10" E-110 at 300hz.... I didn´t like it at all. The bass was very blury and boring, no punch at all. It was plenty of lowbass, but no energy and dynamic in the upper bass....

I matched the GTi with an E-130 a bit later with 60hz crossover and it was much more pleasent to me. It blended in a lot better, but it was still a rather brutal sounding woofer without any real precision...

[DoctahGonzo]

So I changed the setup a bit. I am now shooting for a two Selenium 12pw5's to bridge the gap between the subwoofers and the horns.

My main trouble now is the one which i began with. How exactly to wire the subwoofers. Toddalin stated that he wired them for 12 ohms, and that i could also wire them for 3 ohms.

Wouldn't they be more powerful at 3 ohms?

And most importantly, Where exactly do i find an amplifier that would work with that? I'm assuming a 4 ohm amplifier would work for 3 ohms? But what about running them at 12 ohms, what impedance should the amplifier be stable at then?

Just some quick browsing online, I was unable to many amplifiers that are rated past 8 ohms.

Thanks again guys

[toddalin]

So I changed the setup a bit. I am now shooting for a two Selenium 12pw5's to bridge the gap between the subwoofers and the horns.

My main trouble now is the one which i began with. How exactly to wire the subwoofers. Toddalin stated that he wired them for 12 ohms, and that i could also wire them for 3 ohms.

Wouldn't they be more powerful at 3 ohms?

And most importantly, Where exactly do i find an amplifier that would work with that? I'm assuming a 4 ohm amplifier would work for 3 ohms?

Thanks again guys


Bad assumption. That's why I run them at 12 ohms. The power is reduced, but the load is easy on any amp on the market.

[DoctahGonzo]

I was thinking the load on the amplifier might be the reason why you would run them at 12 ohms.

So i've never had to wire anything for 12 ohms, usually just 2 4 or 8. Most amplifiers i've seen online do not have listings for 12 ohms. Where would i look for a 12 ohm amp? Toddalin, what are you using to power these?

Would i go for an amp that's 4 or 8 ohms, and just do the math for 12 ohms?

Thanks a bunch for the advice man, it's great to have somebody who has been there!

I really just don't know where to find a 12 ohm stable amplifier

[Hans Bleeker]

I experimented a lot with those units, till 100-150Hz they do a good job but no way you will ever get to make them sound nice or even be a match to anything if you run them to 800Hz or higher. Use a 2206 to from 100-150Hz till 1000Hz if you want a connection to the 2370, 800Hz works litte better on the 2206 but I would say use a 2" horn then instead of the 2370.
Curently I use sort of this config, 2235, 2206 2352 2403. The W15 I use sometims too in this config, when I do 100-500-10K crossing, for 250-1K-10K the W15 is no match for the 2235, says a lot about the workable range of the W15. I tried the W15 in 225L ported and 170L ported, my room is to small to notice much difference, in both cases that thing hits the wall with brute force :) (although no physical contact) And just paralel the voicecoils, I use a QSC EX4000 on them, they love a bit of juice. And if you dont go full power on them a 4 Ohm amp thats is stable should have no problem with 3 Ohm.

[Lee in Montreal]

I was thinking the load on the amplifier might be the reason why you would run them at 12 ohms.

So i've never had to wire anything for 12 ohms, usually just 2 4 or 8. Most amplifiers i've seen online do not have listings for 12 ohms. Where would i look for a 12 ohm amp? Toddalin, what are you using to power these?

Would i go for an amp that's 4 or 8 ohms, and just do the math for 12 ohms?

Thanks a bunch for the advice man, it's great to have somebody who has been there!

I really just don't know where to find a 12 ohm stable amplifier

Any amp will do 12 Ohm. Amps are usually rated for 8 Ohm and 4 Ohm, but nothing keeps you from using 12 Ohm drivers. You will have a bit less power, that's it. If you have an amp rated at 200w under 8 Ohm, you will probably get around 150w under 12 Ohm. So, pick a powerfull amp.

Look into Yamaha power amps - P3500S / P5000S - as they are cheap and reliable - and often available used.

Lee

[toddalin]

I was thinking the load on the amplifier might be the reason why you would run them at 12 ohms.

So i've never had to wire anything for 12 ohms, usually just 2 4 or 8. Most amplifiers i've seen online do not have listings for 12 ohms. Where would i look for a 12 ohm amp? Toddalin, what are you using to power these?

Would i go for an amp that's 4 or 8 ohms, and just do the math for 12 ohms?

Thanks a bunch for the advice man, it's great to have somebody who has been there!

I really just don't know where to find a 12 ohm stable amplifier

An amp will double its power with a halving of the impedience provided the amp has the current capacity to push the load. Loads over 8 ohms are easy to push and don't require as much current. The loss in power going from 8 to 12 ohms is ~33.3% or ~1.8 dB.

I run my W15GTi as a true sub and power it at 12 ohms with a Crown PSA-2XH. This could put about 1,000 watts to the 12 ohm load if necessary (but will first trip my home's circuit breaker). But I run the W10GTi's on my surrounds and these channels are rated at 130 watts on my Yamaha RX-Z9.

[DoctahGonzo]

So i've been looking at some of your suggestions, especially the yamaha P5000 or P7000s, among others.

So now I'm crossing another bridge (Bridged lol) that I'm not too familiar with. Looking at some of the stats listed on certain amps, the amount of watts put out on certain amps bridged isn't what i would expect. I thought bridging just meant that you added the power output of both channels, is this not true? I've seen some bridged specs that are higher than the added total of both channels. Is there an equation for this?

And would it be okay if i slightly underpowered the W15gti's? like 700 watts per channel okay? I know that you shouldn't underpower speakers by too much, but i didn't think 100watts would be that much of a problem.


And lastly, as a side note. Where should i start looking for box designs? I was planning on making two boxes for the subwoofers, and another for the mid and horn combo. Any suggestions guys. As always, you guys are awesome, Wish i could soak up more of your knowledge. Thanks again!

[Lee in Montreal]

Making a separate box for the woofer and the upper bass/mid driver would be great. This way, you can redo a cabinet without having to redo everything.

PS My 240wpc (under 8 Ohm) PC2002 Yamaha outputs 700w when bridged. So, yes, it is normal that bridged output is higher than the sum of each channel

Lee

[DoctahGonzo]

How much higher is the power output on bridged channels than normal?? Is there an equation?

And should i bridge the channels if i will be running the amplifier @ 12 ohms for the JBL W15GTi's with DVCs?

Lastly, can i buy an amplifier that will not be the full 800 watts RMS that is suggested for the subwoofers??


Sorry about so many questions guys, but the help is extremely appreciated! Thanks guys!!!

[Lee in Montreal]

Every amp will behave differently when bridged. Forget about any formula.
Start building your cabs. Show us some nice pictures and then we'll see for your amp. ;)

[toddalin]

How much higher is the power output on bridged channels than normal?? Is there an equation?

And should i bridge the channels if i will be running the amplifier @ 12 ohms for the JBL W15GTi's with DVCs?

Lastly, can i buy an amplifier that will not be the full 800 watts RMS that is suggested for the subwoofers??


Sorry about so many questions guys, but the help is extremely appreciated! Thanks guys!!!


Varies with the mfg., but usually at least twice the power to ~2.5 times of a single channel.

Yes you can use less power, but you will loose volume.

Each doubling/halving of the power results in a change of about 3 dBA and is barely discernable. A change of 5 dBA is clearly audible and a change of 10 dBA sounds twice/half as loud. So you find the dBA tha tthe speaker is rated at and at what power and you can go from there to determine what is acceptable to you.

These speakers do take a lot of power. But at that power, they make a lot of volume and were designed for mobile competition dB levels where volume is everything.

[Lee in Montreal]

...they make a lot of volume and were designed for mobile competition dB levels where volume is everything.

So true. And at home I doubt you will require the same window shattering power as under an SPL competition ;-)

[honkytonkwillie]

And lastly, as a side note. Where should i start looking for box designs? I was planning on making two boxes for the subwoofers, and another for the mid and horn combo. Any suggestions guys. As always, you guys are awesome, Wish i could soak up more of your knowledge. Thanks again!

Any box designs you're likely to find on the web for this woofer will have been designed for an automotive environment, which has a completely different transfer function than a living room. You would be much better off getting the woofer's Thiele-Small parameters and plugging them into some speaker design software.

And this woofer has been around for a few decades with different versions, so make sure the specs you find are for the version that you have.