Solved! Amplifier Connection From computer multimedia woofer

[umar.ghauri176]

Hi Guys,
How are you,

Actually im new to this so want your opinion on it. The thing is that I have 2 jbl woofers. Which is connected to yamaha amp avx-700. The thing is that as i hook the woofer wires in `Main Speaker terminals`, so from woofers i get the bass plus vocal music, but not the pure bass.

So an idea came into my mind, I have a 2.1 ch multimedia computer speaker set. from which the speakers got damaged somehow and got wasted, but the multimedia woofer box working fine. So I opened up the woofer box, and the thing which I did is, I disconnected the woofer from the circuit board and connected the 2 RCA cable (L, R) to that wire which goes to the woofer for providing it low frequency signals.

And then from the RCA cables, from the other end I connected the RCA jacks to the yamaha avx-700 back panel in CD Line input. So that the low frequency signals will go to the avx-700. Then for testing it, I switch on the avx-700, and the multimedia woofer box. and connected the aux cable to the woofer box, and play the song from mobile. the JBLs sound goods. No more vocals music, only bass.

So I want to know it that approach is suitable ?, as I provide the low frequency signal from one of the multimedia woofer box circuit via RCA cable to the avx700 ?

 

[doolittle]

ok so it sounds like your JBL subs are unpowered and in a box (like a car sub) so yes, that is why it's working as it is using the RCA cables from the 2.1 sub amp to them.

Probably best to not use the RCA cables for that, they are made for low-level signal and not really made to handle any amount of amplified power, best use thicker wires that are made for power transmission like real speaker wire or zip cord - I would worry those wires would melt if you had it running on higher volumes for any amount of time.

I believe the AVX-700 does have A and B channels so just connect the regular speakers to the A channel, get a pair of these passive sub crossovers and connect them to the B channels and the subs. Should work well enough.

I have an old BSR unpowered 15" sub, I am using a car amp to power it with an old PC power supply that has +12v@130w and it's connected to my Onkyo AVR that has an LFE / sub-out - that's the best way to go IMHO, since the subs really love a lot of juice.

EDIT - was just reading up on the AVX-700 it appears it can only handle 6-ohm speakers and higher, so if they are indeed 4-ohms each the best bet may be to bridge them in series into a single 8-ohm load and use with a higher power amp like I have on my setup, it may damage the AVX-700 if you crank it up too high like I have previously mentioned. If they are 8-ohm, then no worries will work directly connected.

 

[umar.ghauri176]

Thanks bro for your feedback,
Actually i have 2 jbls woofers, each one have rated at 4ohms, with 300watts RMS.
So if i connect both woofers in series to get 8 ohm load on avx700, as avx only handle minimum of 6ohms.
So is it suitable, ? ok I agree thats fine for 8ohm load for the avx, but the power 300 + 300 = 600w RMS. does avx damage or not. can avx handle that much power 600w rms. ?

 

[doolittle]

Well the main problem is on the AVX is you cannot bridge the output on the B channel to make a single output so you can connect both outputs to the single sub series connection - possible you could connect just one channel L or R, but then you are not getting lows from both L/R channels and that is not ideal.

It may be simpler to just use a single car amp with a 12v power supply and get some low-level sub filter to make it an LFE. I would use these to make them all work:

Wecooland Subwoofer Equalizer Crossover RCA
BOSS Audio R4002 - Riot 800 Watt, 2 Channel
12v 30a Dc Universal Regulated Switching Power Supply 360w

The spec on the amp says "150 W X 2 RMS @ 4 ohm" which is more than enough to power your subs, and the 360w power supply should be well more than enough (since car amps are very inefficient). Connect it up to one of the AVX line-out, it will sound very, very good!

 

[americanaudiophile]

If you have to use the speaker level signal to provide an bass only input for the Yamaha then you want to connect a speaker to line level converter in between them. That makes it safe to use the crossover in the 2.1 to provide a bass only input for the Yamaha.
The other option is to try to find the line level output to the amp that drives the 2.1 woofer and connect that to the Yamaha.
You can split that output to drive both channels of the Yamaha and so both woofers.