Question for any audio experts

[dave88sw]

Hi,

I've got a Kenwood underseat sub in my Discovery (just a little thing like this: http://www.ebay.co.uk/itm/Kenwood-KSC-SW11-Compact-Under-Seat-150W-Active-Amplified-Powered-Subwoofer-Sub/171165909764?_trksid=p2485497.m4902.l9144 ) as well as the original rear sub and 4 speakers.  Both the rear door sub and the underseat one run off the same pre-outs on the head unit (only 1 pair so split between the 2) and all works perfectly.  My friend (who also has a disco) was with me in the car the other day and commented on how good the sound was and has asked if i'll do something similar in his disco.  His disco was a base spec so has no rear door sub woofer (not a big issue really, the underseat one is better, i only wired my rear sub up because it seemed stupid to have it sat there doing nothing) and he has an aftermarket head unit with no rca outputs.  Now, the sub i've linked to above is capable of taking pre-amp input or speaker level inputs.  Is there any reason why i couldn't use the rear speaker feeds to drive the subs amplifier as well as the speakers themselves? Basically, do i have to sacrifice the rear speakers in favour of the sub or is it ok to have both, i imagine the subs amplifier is only using the feed for a signal and so wouldn't overload the head unit's built in amp?

 

Thanks

Dave

[Cynic-al]

I doubt you'd overload it as it can only give what it can give although depending how it works it might effect the impedance? I have an active sub in my house that can work the same way and it doesn't cause a problem although I run it off a dedicated sub out on the current setup.

It will pick out the lower frequencies which only works if the head unit is sending them there in the first place so you need to make sure it sends everything to the back and isn't splitting the sound up. It will also still play the bass to the smaller speakers so if they're distorting it won't cure that unless you filter them too?

Stick it in and if it's rubbish get a better head unit? 

[dave88sw]

I'll probably upgrade the standard paper cone speakers to some 4" kenwoods, i'm certainly happy with mine with that setup.  I don't think distortion is too much of an issue, i find i have mine on a much lower volume with the sub. 

As you say, all i can do is try it and if it doesn't work i'll have to rethink it. 

Thanks

Dave

 

[SPendrey]

I did exactly what you're describing... I took a feed off of the cables to the rear speakers and fed them to the amp.  No issues encountered.

 

The challenge will be getting the tuning right, getting the right balance of cross-over, volume etc.

[teabag]

Subs are mono, the rear loud speakers are stereo and a higher frequency. Installl a sub from the preamplifier of the head unit and adjust the gain according. No preamp then get a head unit that has one. Simples.

[Scotts90]

I think the whole point is not having to change the head unit, hence the info about high level line inputs..

In a word, No. You won't have to lose the rear speakers, in order for the sub to act as a monoraul speaker the high level inputs from both left/right channels should be used (the multiplug will have 4 tails to splice into R+R- and L+L-). Back in the day we used Line out converters to converter speaker signals to RCA, the amp just has this facility built in. 

There are highly expensive ways to create RCA pre-outs on OEM head units and provide a higher voltage and cleaner signal but if a little bass is all you want then the above should work just fine. 

[dave88sw]

Sorry for the late reply.

Thanks for the help, really appreciate it.  Yes, in an ideal world we'd change out the head unit for something better but at the end of the day, this Discovery is used mostly for a bit of off roading fun and being a Land Rover, a decent sound system would be wasted on it.  I've wired it up to the rear speaker outputs and it seems to be working very well.  My friend is certainly happy with it so mission accomplished.

Thanks again

Dave