john banks

I was wondering about getting a 2 channel amp to add to my four channel one so that I can run the front speakers bridged off the four channel. I only need 100WRMS X 1 for my sub - I was even considering one of those Jensen cheapos as I don't think a bandpass sub box is very quality sensitive. The alternative is another 4 channel - there are some Alpine "4x75" around the £100 mark. I guess two channels of this would do the job, and hey I might even hook up my rear speakers to the other channels. In reality about 37WRMS/ch; 100WRMS bridged, compared with 150WRMS/ch for fronts bridged (although speakers only 90WRMS in front but should improve compared with 50WRMS unbridged). So it should still be front soundstaged. Any thoughts?

Also, have 8AWG cable - may need to upgrade - pain. At present it has 60A fuse - my 4 ch amp has max current drain of 38A - what is the max safest fuse I could put in 8AWG wire - 80A would be plenty. Is this safe?

Scooby Doc

John

8 guage - waste of time. Ok at present but not future proof. Makes good washing line!

2 channel amp? Join me with my negotiations with Craga.

How about soundstream 300sx factory reconditioned for $180. Shipping add $60 but this maybe reducible.

Martin

kryten

Fuses are rated on the amount of current they will sustain for a certain period of time before blowing.

EG my last system had a 75amp fuse but was at times drawing in excess of 120amps for VERY short periods.

The fuse is really there to blow if anything grounds out - stopping massive arcing and a major fire risk.

I doubt you'd need to upgrade the fusing if you add another amp: upgrading the 8AWG to 4 AWG would be a good idea though, especially if its a long cable run.

See the RAC FAQ below for AWG recommendations based on length of cable and current requried:

john banks

Thanks Kryten - it seems they recommend 4AWG for anything like reasonable power. Anyway I bought the Jensen 2 channel and it is bridged, hidden away on the back of my sub box, running it even louder than the Kenwood did (!) - watch your walls ScoobyDoc - nifty little 45Hz bass boost helps just where the sub box response rolls off. Very impressed for the price - no apparent loss of quality either.

When bridged for the front channels the system really comes alive - excess amp power is clearly the way to go - I now cannot reach the onset of distortion with all channels playing. Red line in 3rd - (my acid test) is now obscured entirely by music at only 50% of max undistorted volume!
Thanks for the offer ScoobyDoc, but I'll always be a cheapskate, but I can recommend this nifty little Jensen for sub usage certainly - only £64 from

rockin'Ru

John,the sub you're running is a Pioneer band pass,right?The sensitivity must be around 100db? Almost any amp will run that sub with "seemingly"clarity.Try that amp on a sealed enclosure.SQ will plumet.
Have any of you heard of a "death box"?You have to buy the plans for $30,but this box will make a $20 woofer and $100 amp thunder.
Same idea as the Pioneer box.Do a search on Decware.You'll see what I mean.
As for the comps,you're using passive xovers and they're power hungry.Feed 'em lots.They'll take more than the rms rating.
Those baffles should be there any day.Sorry it took so long.Damned holidays.As if the elections weren't enough.LOL!

john banks

Thanks Steve. I think the sensitivity is something like 106dB/W "in car SUV type".

The cheapo amp - I tried it with my components whilst wiring things up as a test and it (surprisingly) didn't sound that bad at all! But I'm sure it's not a patch on a higher quality American amp.

I like the Death Box idea! Unfortunately can't access their website as at work.

What sort of insertion loss due to passive crossover? - I think they're 2nd order, but I can't get into the box to see. The Kenwood amp I'm using for the fronts is rated at 2 X 150WRMS (2 X 300W "Max") bridged 5Hz-50KHz -1dB <0.1%THD @ 14.4V, woofer says 90W rated, 270W peak, tweeter 50W (through supplied crossover - so it is obviously less, but I am not biamping so I spose it doesn't matter?)

It sounds quite nice with the HPF at 70Hz, but the main problem with going lower is the doors vibrating despite soundproofing (lots, but it is door trim shaking now) - my 1" foam is out - didn't bother putting it back whilst waiting for baffles. I hope the baffles will let me go lower on the fronts without the doors shaking - you mentioned 50Hz before - would I be best setting my sub crossover to the same or keeping it higher (70Hz at present)? I suppose it is suck it and see, but do you have any thoughts on this? Theoretically, I suppose the -3dB point should coincide to get flat freq response. The manuals don't specify but I am presuming by convention that crossover controls are marked with -3dB points rather than the "shoulder" of the crossover?

[This message has been edited by john banks (edited 09 December 2000).]