Hi guys,

I'm looking to install a single 12" sub in my BA Mk2 XR6t with Premo sound. I've been reading a fair bit and am looking at the options regarding runing the rear speaker wires to a line level converter to the amp to power the rear speakers and the 12" Sub.

The amp I'm looking at is a new Sony Xplod series:

Sony Xplod XM552ZR 2 Channel Amp, or the 4 Channel Equivalent XM554ZR.

Manual for the 2 channel amp

Manual for the 4 channel amp

These amps sound ideal because they have high-level input (so no line level converter required) and turn on when it senses the headunit is on.

Now, the manual for the 2 channel amp says you can hook up two speakers and a subbie which is good, because you'll need to unplug the cables from the rear shelf sepakers into the amp and then back from the amp to speakers for some noise. You then bridge these two channels to run the amp. To me that doesn't sound right because the signal would not go through a low-pass filter. Can anyone set me straight? (Speaker connection option 4 in the manual)

If we use the 4 channel amp we can have separate outputs for the rear parcel shelves and the sub. But, do you need four channel input in order to do this or are there any there issuse that need to be addressed? (Speaker connection 2 in the manual)

Finally, is there any harm is running the high-level signal from the factory 8" sub to the amp then to the 12" sub? Or is this not suitable? Which filter would you use?

Any help would be appreciated, I'm getting the sub this wekeend and want to get it hooked up soonish!

Hi Spud,

Good to see people having a dip at better in-car stereo, I hope I can help.

In relation to speaker level inputs you have a problem in that the signal to the parcel shelf speakers has already had the low frequencies filtered from them. I have a ute (no sub) so I might be wrong, but this should have been done at the head unit. So for your low frequencies (which is what you want lots of), your only source is the factory sub inputs, which I read on here are full range, and filtered at the amp. The issue here is that the design crossover probably isn't -18db / octave and 80hz. it might be close enough, and you might be able to find a setting you like by fiddling with the bass on the head unit (or amp gain), but it isn't optimal.

The low level inputs to the factory amp should be usable, but I believe that they are relatively weak signals. I would expect that the 2 channel amp on high gain would be able to reach a level where it integrates to the other speakers, but again, nothing is certain. Also running consumer level amplifiers on max gain is usually undesirable.

There may be hope if you can see a capacitor in series with the parcel shelf speakers, then it's likely that they are receiving full range and passively filtering. I would not expect this, but after seeing what is done to achieve the tweeters in the A pillar, I would not be surprised. If you do find these capacitors then you can use these wires as speaker level inputs on your amp.In this case have another look the manual diargram E for the inputs, and diagram 3 for connecting the sub.

Connecting the new amp inputs from the factory amp outputs is philosophically bad. The logic is that every component is the signal path degrades the signal, and an amplifier is a lot of components, and a 'built to budget' amplifier like ford, is likely to have noticable distortion, and then if you are using another amplifier anyway.....

The possible gains of using the factory sub amp in this way are that you will have good signal levels into the new amp, and already filtered in the way that the system was designed, so that might be OK.

Please post up any specific points that I need to clear up. And Good luck!

Chris.

Thanks for the reply, and I think that you have just confused me a bit more, I'll have to re-read again when I have a clearer head.

What is happening is that I've just come into a 12" sub and box and an otherwise completley stock system. I want to remove the 8" factory free-to-air and replace with this one in the boot. What would you suggest to get this done properly?

Pat

I use line level convertor off the rear speakers to run 2 x 12 alpine subs and a mono channel alpine amp and it sounds (rap. that's all I know!!!!!

Hey mate I run a 700rms amp with a 15 inch sub useing a signal converter from the back speaker wires to get my RCA out put's and I picked up my signal wire(which turns the amp on) from the 12V power supply were the cig lighter should be.

How ever what I didnt do was pick up the signal wire from the stock amp which is in the boot and heaps closer(dumb ass) so its very easy to do.

All in all with the rest of the stock sound system and my new sub and amp it CRANKS.

Hope that helps

That's what I'm talking about! What exactly is your amp? Which signal converter do you use? How are you running the rear speakers if you're using the signal converters?

Hi Spud.

If you use an amp with the speaker level inputs, you do not need line level converters, and the auto switch on (sensing) in that particular amp is a nice feature for your proposed application. It also avaids finding a remote turn on. ACC is OK but you have to have the key on to have the amp on, which is not factory functionality.

Hi Ypurv4 - can you confirm that your amp taking signal from the rear parcel shelf is recieving full range? It is possible that the factory amp just adds to the low frequencies, and the phase cancellation might not be too bad, seeing as the speakers and actual sub are reasonable close to each other. But I would be surprised. Also if the filtering to the rear speakers is passive, then ypurv4's arrangement makes good sense.

Mine is a BA Tornado, so no sub - all my speakers are full range.

Can anyone confirm how the filtering to the rear speakers is done?

Good to see a bit of good discussion here.

Cheers, Chris.

Hey Putrid frut sorry but im not really in to tech and know how of it all, I just know how to wire it up lol.

I only use the back speaker wire to covert them to the RCA out puts

I use the 12v power supply for the signal.

This is a pic of the parcel shelf speaker (from another thread), the factory 5x7 is on the left. Does that help with regard to the passive filtering?

Edited January 4, 200719 yr by SpudMuffin

I rekon that the low feq. is filtered prior to the speakers, if you unplug the factory amp then they will make full range sound, so if you use that xplod amp with the factory amp unplugged you sould be right if it has seperate high low pass filter for front and rear