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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > AUDIO/VIDEO + BLUETOOTH + Electronics/Alarm/Software > best choice.. amp the underseats or rears?



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      11-29-2014, 01:31 PM   #1
sparkymarky
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best choice.. amp the underseats or rears?

So i have hifi in my e90.

I have some better kit but am short of amp channels for all the speakers.
so is it better to leave the underseats or rears on the oem hifi amp?



I have:

A Jl audio A4300

4 x 70w rms @ 4 ohm .
4 x 110w rms @ 2 ohm


& a sub mono amp @ 300wrms


So I have 5 channels available.


DO i leave the underseats on the stock amp or the rears on the stock amp.
I need rears to retain PDC.


So, amp the:

1. Front left, Front right, Underseats, Sub. (oem hifi amp for rears)

OR

2. Front left, Front right, Rear Left, Rear right, Sub. (oem hifi amp for underseats)






Tricky. I have the following available. All stock 2 ohm speakers. OR x4 4 ohm component speakers if needed (100w rms each) for fronts and rears.


IS it better to have the underseats amped or the rears amped in terms of any audio delay, soundstage, balance and the like as I will not be adding any EQ..
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Last edited by sparkymarky; 11-30-2014 at 06:03 AM.
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      11-29-2014, 01:44 PM   #2
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i'm thinking:

Front left new 4 Ohm @ 70w rms
Front right new 4 ohm @ 70w rms
Rear left new 4 ohm @ 70w rms
rear right new 4 ohm @ 70w rms

Underseats factory hifi @ 40w rms each

sub @ 300w rms.





Reason being feeding each underseat with 110w rms each is probably gonna blow them quickly. Even if I wire them both in series (4 ohm) using one amp channel that will then only give them 35w each...(so 5 watts less than the factory hifi amp will). Pointless.
So amp the rears rather than the underseats?



[
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Last edited by sparkymarky; 11-30-2014 at 06:04 AM.
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      11-30-2014, 09:18 AM   #3
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more power to stock door mids and underseats, but use low gains settings. it is wasteful to do anything with the rear speakers, especially if you are on a tight budget.
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      11-30-2014, 05:59 PM   #4
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No way to keep the stock amp hooked up if your using Technic's hifi harness. I wouldn't bother with the rears but since you need them for PDC you should try to trade your amp for an xd600/6.
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      11-30-2014, 06:09 PM   #5
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ah nope not using Technics harness so i'm free to hook up as needed.

Yea ideally I want one of those xd600/6's but theyre just too expensive over here in the uk though- $625 usd (400)
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      11-30-2014, 06:15 PM   #6
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I wouldn't do the install without the proper harness.
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      11-30-2014, 06:32 PM   #7
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Yea most people its easier and more convenient to use a harness, but we should remember its not a proper harness just one someone knocked up for convenience. Most installers won't use a harness just break out from the cables as needed. I'll be breaking out using bullet connectors so I can reinstall all to OEM just as easy as using that harness
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      11-30-2014, 06:40 PM   #8
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Since the HiFi HU has front and rear balanced outputs, you can use the front outputs as inputs for the JL amp, and leave the rear outputs hooked up so the PDC will continue to work. No sense amping the rears, use the 4 channels for the fronts.
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      11-30-2014, 07:34 PM   #9
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Quote:
Originally Posted by kaigoss69 View Post
Since the HiFi HU has front and rear balanced outputs, you can use the front outputs as inputs for the JL amp, and leave the rear outputs hooked up so the PDC will continue to work. No sense amping the rears, use the 4 channels for the fronts.

Ok will give this a go first. I'll stick front channels into the JL and sum to channels three and four. I've just noticed the The JL has seperate gains and crossovers so i can 'up' the gains for the new fronts if needed (Channels 1 and 2) 100wrms components with silks) and keep the gain low for the underseats (channels 3 and 4 of the JL).

What do you reckon the stock hifi underseats will handle power wise?
And what's a good crossover point for the stock underseats?
As I have a trunk sub i will set the seperate monoblock to LP 80hz so i would like to bandpass the underseats for about 80hz-200hz but my jl doesnt have band pass.....just either LP or HP (or OFF) , not both at once.....bugger..... no band pass possible on the underseats....i guess just a LP of about 150hz then....
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      11-30-2014, 08:10 PM   #10
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...or i may HP the underseats at about 80hz (leaving the sub to take care of <80hz) to stop them distorting with low frequencies with such an increase in power... hmmm experimentation will yield the best results i guess!
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      11-30-2014, 08:19 PM   #11
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Quote:
Originally Posted by sparkymarky View Post
Yea most people its easier and more convenient to use a harness, but we should remember its not a proper harness just one someone knocked up for convenience. Most installers won't use a harness just break out from the cables as needed. I'll be breaking out using bullet connectors so I can reinstall all to OEM just as easy as using that harness
I'd rather hack up Technic's harness than the wiring in the car. I only cut wires if its absolutely necessary and they get soldered and covered in heatshrink.
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