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Using a JL12w7 (3ohm) with 4 ohm Power amp


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#1 of 12 OFFLINE   Norm12345

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Posted December 09 2011 - 07:26 AM

Hi everyone, This is my first post here... but I had a question that I can't find a clear cut answer to... I got a great deal on JL 12w7 in a sealed box a while ago from a friend of mine, originally this was going to go in car, but I spent the money on some good component speakers instead and I can drive as much as bass as I really need in a car application with just those. So I'm looking at using this speaker for my Home Theater/Stereo setup. I'm really not aiming at using it to its full capacity as of right now, its rated at 1000w with a 3 ohm load. I'm also a bass playing musician, and in the mean time, we don't have a current rehersal studio that I can use my power amplifier. Our practices are generally running through a headphone amplifier and I really only need my pre-amp for this. So Its coming out of my rack unit for now... The power amp is a Yorkville AP4040 it rated at 1200w@4ohm continuous per channel, and I was simply going to use one channel to power the JL12w7. Again, I doubt I'll be using all its potential power and the amp does have thermal protection in case I do over load it... Right now, its only going in 2.1 system with 2x klipsch F-20 tower speakers... but eventually it will evolve to a 5.1 system, with some better towers, leaning towards Paradigms... Also, can anyone recommend me a suitable amp in the future for the JL 12w7 sub? I assume I'll have to get a 2ohm amp. Thanks,

#2 of 12 OFFLINE   Robert_J

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Posted December 09 2011 - 11:01 AM

Can you post the Theile/Small parameters for the sub? When you put it in a box, you will get some impedance rise naturally. That said, you may be able to use 1 channel of your current amp to power it. If Yorkville is like other pro amp manufacturers, they rate their power at 1khz. Behringer does that with their EP-4000. At 2 ohms is puts out 1,250w / channel. But at 20hz, it only does 800w / channel. The power supply just can't keep up. The reason I bring up Behringer, it is a great value amp. Being a musician, you have probably heard the negatives on Behringer. I'm sure they can't stand up to a tour like Crown, QSC or Carvin but in the home, they work just fine. I run one at 2 ohms stereo into a pair of TC Sounds 15" TC 3000's. What is your enclosure design for the sub?

#3 of 12 OFFLINE   Norm12345

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Posted January 04 2012 - 09:20 AM

ok, that setup did not work :( Bit the bullet and bought a used Crown CE4000 that should do the trick... waiting for shipment... Also, if its worth mentioning... right now its in a sealed box... I think for the room size, I'll have to build a custom ported box... Playing around with some design software to come up with some ideal dimensions... My co-worker told me to tripped the volume, so like ~3 cu ft. does that seem about right... I also noticed that the design software seem to favour circular ports, instead of the slotted ports, any reason why? I was going to do slotted port for simplicity sake... give me your thoughts... I'm all ears... thanks,

#4 of 12 OFFLINE   Robert_J

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Posted January 04 2012 - 09:43 AM

I also noticed that the design software seem to favour circular ports, instead of the slotted ports, any reason why? I was going to do slotted port for simplicity sake...

A port is a port. Just convert the circular port to slotted.

My co-worker told me to tripped the volume, so like ~3 cu ft. does that seem about right

You haven't posted the T/S parameters.

#5 of 12 OFFLINE   Norm12345

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Posted January 04 2012 - 10:07 AM

Humm... can't seem to find it in the specs... here's the link tot the specs... http://www.jlaudio.c...r-drivers-92112 Not sure if it might be called something else...

#6 of 12 OFFLINE   Norm12345

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Posted January 04 2012 - 10:09 AM

Humm... can't seem to find those parameters... Here's the link to product specs... maybe its called something else?

#7 of 12 OFFLINE   Norm12345

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Posted January 04 2012 - 10:18 AM

try the link again... http://www.jlaudio.c...-drivers-92112

#8 of 12 OFFLINE   Norm12345

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Posted January 04 2012 - 10:20 AM

ok, lets try the link again... http://www.jlaudio.c...-drivers-92112

#9 of 12 OFFLINE   Norm12345

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Posted January 04 2012 - 10:22 AM

ok, lets try the link again... http://www.jlaudio.c...-drivers-92112

#10 of 12 OFFLINE   Robert_J

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Posted January 04 2012 - 10:26 AM

If you are working with design software then you have the Theile/Small parameters.

#11 of 12 OFFLINE   Norm12345

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Posted January 04 2012 - 10:28 AM

ok, found out what theile and small is ;) sorry, still kind of new at the AV game... I was actually looking for that parameter name in this list, didn't know this collection of parameters was called that... Free Air Resonance (Fs) 27.2 Hz Electrical “Q” (Qes) 0.514 Mechanical “Q” (Qms) 7.807 Total Speaker “Q” (Qts) 0.482 Equivalent Compliance (Vas) 2.33 cu ft / 66.0 L One-Way Linear Excursion (Xmax)* 1.15 in / 29 mm Reference Efficiency (no) 0.249% Efficiency (1 W / 1 m)** 86.2 dB SPL Effective Piston Area (Sd) 84 sq in / 0.0542 sq m DC Resistance (Re) 2.47 Ω

#12 of 12 OFFLINE   Robert_J

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Posted January 04 2012 - 12:07 PM

http://en.wikipedia....ki/Thiele/Small 3 cubic feet sealed looks good. Keep the power under 600w and you will be fine. 4 cubic feet ported, tuned to 20hz is also great but you need a subsonic filter set at 17hz with at least a 12db/octave slope. 18db/octave would be much better.