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Old 29th April 2008, 08:43 AM   #1
sr2002 is offline sr2002  India
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Join Date: Jul 2005
Location: india
Default Using a Car Subwoofer for Home theatre

helo guys ... its been a while since i logged on to this forum.

The thing is i live in india and here where i live i am not able to find any good quality subwoofer drivers ...

So i was wondering if the car subwoofers can be hooked up with an amp that i built using Lm3886's ... ?

To breif u guys ... i have built the above amp using a 10amp trafo and two separate circuit boards of lm3886 in parallel.. and each board has a 2 lm3886's in bridge config....
Right now im using the amp a stereo amp ... so is it possible to further bridge these two channels ... so that they can drive these large subwoofers ?

If not which amps can u suggest to drive it ... and that are simple to built ... ?

these are the two subs in my mind...

JBL GT4-12
SPECIFICATIONS

General
Frequency Response 28Hz - 450Hz
Sensitivity 93dB
Impedance 4 Ohms
Voice-Coil Diameter 50mm
Cut-Out Diameter 283mm
Mounting Depth 161mm
Overall Diameter 311mm
Vas 100.45 liter
Qts 0.43
Fs 24.75Hz
Qes 0.46
Qms 6.46
Sealed Enclosure (vol) 28L
Vented Enclosure (vol) 64L

Sony Xplod XS-L124P5B
General
Woofer Size (cm)
30
Type
Enclosure / Single Voice Coil
Peak Power (W)
1300
Rated Power (W)
380
Weight (kg) approx
Approx. 4.5kg
Impedance (ohm)
4
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Old 29th April 2008, 09:46 AM   #2
sr2002 is offline sr2002  India
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I would also like to add that i currently have 1 opa549 and 1 opa541 ... and around 5 lm3875's lying around .... so im kinda keen to use them ...
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Old 30th April 2008, 12:59 AM   #3
dudes_ is offline dudes_  United States
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I'm using Car Subwoofers in my setup. I had one 12 MTX DVC 4ohm I tested before purchasing 2 JL's 12".

I'm pushing them /w 2 Audiosource AMP300 bridged, speakers in series @ 8ohm.

It sounds pretty good. It's bit rougher than running the 4 DCM 12's that I have. But I like it better with the loudspeakers cause it seems to drown out the treble more. They have deeper bass and they don't hit the coils as easy. However, if you don't have enough power they will distort at fairly low volume so make sure you have enough power. I like having a AMP rated at the RMS if not 100+W's more.

They seem to sound good front firing but they sound much louder when pointed toward a wall or in a crack somewhere (that's also true with most speakers, but it's much much louder even still.) Rear fire, everything just rattles! A proper sound room would likely render better results.

I haven't had too much time to play lately. Allergies are bad this year as well, so it's difficult really review the quality.
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Old 30th April 2008, 02:34 AM   #4
sr2002 is offline sr2002  India
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thanks for the reply dudes......

But thats my basic problem .... which amp to use?

I have a bridged lm3886 amp ... which is i guess 100wattRms ... running at 22volts/10amps .... but the thing is that this amp gets pretty heated up even when im using 8ohm speakers .... so i dunno how good it will handle the 4ohm jbl sub?

How are the Opa549/541 or the Lm3875's for this project?

Any simple circuit u could suggest?
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Old 30th April 2008, 05:17 PM   #5
sr2002 is offline sr2002  India
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i would realy apreciate some help guys
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Old 30th April 2008, 05:35 PM   #6
sreten is offline sreten  United Kingdom
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Default Re: Using a Car Subwoofer for Home theatre

Quote:
Originally posted by sr2002

To breif u guys ... i have built the above amp using a 10amp trafo and two separate circuit boards of lm3886 in parallel.. and each board has a 2 lm3886's in bridge config....
Right now im using the amp a stereo amp ... so is it possible to further bridge these two channels ...


Hi,

You cannot bridge amplifiers that are already bridged.
You can wire them in parallel, which you need to do for a 4ohm driver.

See : http://www.national.com/an/AN/AN-1192.pdf see BPA200

Use the JBL driver, at least you have some specifications.
For Sealed use a wellstuffed box 35 to 45L.
For Vented use 70 to 80L tuned to 20Hz.

/sreten.
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When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
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Old 30th April 2008, 07:39 PM   #7
Dan2 is offline Dan2  South Africa
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I am using a 30W x2 amp bridged to run a car sub (JVC 12", 750W max), in a small sealed box, but i use it for music - not movies (although i stil want to try it)
It sounds pretty good, but i am not using the sub to its full potential with this amp - but as it is the box already moves around a bit when i trun it up.

If you are going to buy a sub, maybe look at a dual voice coil - that way you do not have to bridge your amps, you jus hook one amp(channel) to one coil, and the other channel to the other coil.
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Old 1st May 2008, 01:30 AM   #8
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Location: Florida
1st of all, a good car sub works GREAT for a home sound system if you have a good amplifier.

Lots of people here will tell you to use a home sub instead, but car subs work great despite what others say. IMO a good car sub sounds better than the average consumer grade 10 or 12" home sub.

The two subs you mention are both good, The JBL will be louder due to the higher efficiency, which is good for the small amp, but for better bass in the low-end for Home Theatre, get a bigger amp and PICK THE SONY XPLOD!

JBL 24hz
Sony 18hz

I have the Sony Xplod XS-L120P5 (red) which is a slightly lower model than the L124P5, but nearly the same woofer. The sub had the best and deepest bass out of several subs I've tried. The double spider and surround, and leadwires (in the top spider) are bulletproof, and well built, and you can not break these subs mechanically!

Only way I killed my Sony Xplod was with raw power when I completely melted the voice coil together after clipping with heavy rock music with my DIY sub amp with over 350W+RMS. I could give it the biggest bass notes on the loudest songs, and push the cone to the limits and suspension took it all. I plan on getting the newer XS-L124P5 to replace it.

*I'd recommend at least 100-200W RMS amp or more for a subwoofer for good power. The amp HAS to be capable of 4 ohms or less for the best sound, or you may get distortion and eventually a dead amp.

Build a descrete amp instead of LM3886. You will get more power without the current limit that the ICs have.
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Old 1st May 2008, 03:11 AM   #9
sr2002 is offline sr2002  India
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wow ... thanks for the replies guys ... its really good to see that people are trying wierd stuff like me too ...lol

My main problem right now is ... that earlier i had asked national to send free samples of Lm3886 lm3875 and lm337 n lm317 ...

So the thing is .. that i used all four lm3886's for my current amp ... so im only left with lm3875 ... and Opa541 and one opa549 ...

So is there a good schematic to parallel the Lm3875's ...

And as u suggested to use a descrete amp ... which is the simplest one to build .... cause the main problem is ... i often dont get all the parts mentioned in the schematics here in india ...

SO a descrete amp with commonly available transistors would be really gr8 ....

And i had another question .. i have a sony Hi-fi system ... which claims to have an output of 85wRms into 8ohms .... can this thing be any good to drive the sub?
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Old 1st May 2008, 03:20 AM   #10
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Let me make it very clear............

8 ohms = NO!
DO NOT use an 8 ohm amplifier for a 4 ohm speaker!!!
You can use a 4 ohm amp or a 2 ohm amp to drive a 4 ohm speaker.

You can parallel two 8 ohm amps to push 4 ohms too. If that SONY amp you have is 2 channels in stereo at 8 ohms, you can parallel the two channels with 0.1 ohm resistors and drive the sub.

If you are unsure how to build a complete descrete amp to drive 4 ohms, you can use the Lm3886 to drive a pair of biased NPN/PNP transistors for a better output stage.

Other option is to use an LME49810 chip to make a descrete amp with IC voltage amp driving it for easier construction.

If you use an under-rated amp with a sub, the bass peaks will sound muddy and not as solid as a good amp with the right impedance.
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