Audio buddies- need opinion!!

[lizardking]

Guys,

Since upgrading to my Utopia's (which I love) I decided they need more power to get the potential out of them. As most of you know you don't need music for the rear but I do for dual zoning for the rear passengers. Anyway I decided to go wit the JL Audio 450/4 which would give me 150 watts RMS X 2 for the Utopia's and 75 watts RMS X 2 for the rears.. The rears I always set them up -2db anyway's but I think this will give me the all around sound and power I'm looking for. I feel if I upgraded to a 100x4 or 125x4 amp I would be wasting wattage going to the rears which I don't need. What do you guys think of my plan?

[grunge311]

That was my plan when I started on my truck, but I found there was no way to fit it in the space I had designated for an amp.

I think that plan sounds great. You may have to adjust the levels at little depending on the sensitivity of your rears compared to the fronts, but it sounds good to me.

[lizardking]

Thanks for the input!! I think this will be the best all around setup and JL amps are very very clean so it should sound good..

[Justintoxicated]

my plan is to run the rears off the HU heh, sounds good to me. So long as you can turn jsut the rear down lower than 75x2, as in you can fade it almost all the way to the front when it's just peole in the front seat.

[lizardking]

That's kinda what I was thinking... I have all kinds of speaker controls on my deck and can adjust each one by itself.. I plan on doing just what you said..

[rcantu]

either way sounds good. I think as long as you can adjust gains or fading you're ok.

[lizardking]

Thanks, I won't be adjusting my gains once set with DMM at the correct AC voltage output for the load presented to the amp. I will be adjusting at the deck level, gains once set up properly shouldn't need messed with.

[Sammy Sandbag]

Originally Posted by lizardking

Thanks, I won't be adjusting my gains once set with DMM at the correct AC voltage output for the load presented to the amp. I will be adjusting at the deck level, gains once set up properly shouldn't need messed with.

Hey LZ, and everyone for that matter. How exactly do you set your gains? In the past I've just set them according to listening for clipping or watching the clipping LED on some of my amps. I have a digital multi-meter, but that's about it as far as testing equipment. I wanna get this set-up done right this time. I also have the audio-control MATRIX, so I can definately get plenty of power to the amps.

Also, setting crossovers; what's the best method? I don't have a spectrum analyzer (or whatever they're called) so it's pretty much done by ear, but I wanna ensure the comps and subs are getting the right freq range.

[smoketitan]

1) the jl 450/4 are cool--like the front stage power

I always thought utopias are ver efficient and dont need a ton of power?

you may want to look at the new alpine 125x4 4 ch--I heard they are pretty good amps and are cheap

just as another option

2) rear fill run it off the deck thats all it needs anyway (unless your unning 5.1 and you dig surround effect)

3)setting gains, if you have the cash its best to set them with a hand held oscilloscope, connect to the outputs, using some math you get the exact voltage amount you want to each speaker--youll never clip again

ive never had the la around cash to own one--so I do all my level matching by ear

clipping indicators will work also ,

use the multimeter to test voltage, ohm etc etc,


4)crossovers---its best to set them by ear from all that I have read, and have done myself

I have found its really cool to have either a HU with internal crossover, or a outboard digital crossover that you can control from the driver seat--so you can fiddle with the settings and hear the changes each slope/cross makes real time

i tend not to use the amp crossovers--

as a side note some say amp crossovers are better than deck crossovers, but some also say that amps are "cleaner if you defeat most of the onboard processing
so just thought Id add to the discussion

[Sammy Sandbag]

Originally Posted by smoketitan

3)setting gains, if you have the cash its best to set them with a hand held oscilloscope, connect to the outputs, using some math you get the exact voltage amount you want to each speaker--youll never clip again

ive never had the la around cash to own one--so I do all my level matching by ear

clipping indicators will work also ,

use the multimeter to test voltage, ohm etc etc,

Yeah, but specifically how would I use a DMM to set the gains? Like I said, I also have the MATRIX so I could probablly run the gain all the way down on the amps and still have the max power to each amp.

[Justintoxicated]

you set the gain on the amp though not on the Hu.

You use this formula

Max Watts of Amp or Speakers (Whicher is more) I.e Amp = 75w@4ohms x 2
Speakers = 100w@4ohms x 2

then we would use Amp's Max Power before clipping

If your Speakers are not as powerful as your amp, then you want to set the gains to match the appropriate power levels for the speakers so you would use speakers max RMS wattage rating.

if 75w@4ohms per channel

Voltage = Sqrt(W * R)

Voltage = Sqrt(75 *4 )

Voltage = Sqrt (300)

Voltage = 17.32 will be your goal

1) Unhook speakers from amps
2) Turn Gain down on amplifier all the way
3)Turn your HU up to a resonable Max Volume (you don't want your pre-outs clipping the signal either) 3/4's is usualy a good place to max out your volume on the HU.
4) Play Cd with Test Tone (1000htz sine wave for comps works well)
5) Connect DMM to Speaker terminals on amp (for one speaker)
6) Adjust the gain untill the DM reads the desired voltage

Some say you should Zero out everything on the HU prior to doing this, others say to use the settings as you would typicaly have them set to.

This helps ensure that you won't clip untill you go over that particular volume on the HU. You can still play over that volume, but you know that you could possibly have clipping over that volme and damage your comps. Typicaly your Pre-outs put out the most voltage from test tones, regular music will not. But know that past that setting on your HU, your in the danger zone.

The Gain is the input Sensitivity on the amp so I don't see how the matrix would screw things up. If your going to use the Matrix before the amp, just make sre you are using when you set your gains.

[m95roadster]

Originally Posted by Sammy Sandbag

Hey LZ, and everyone for that matter. How exactly do you set your gains? In the past I've just set them according to listening for clipping or watching the clipping LED on some of my amps. I have a digital multi-meter, but that's about it as far as testing equipment. I wanna get this set-up done right this time. I also have the audio-control MATRIX, so I can definately get plenty of power to the amps.

Also, setting crossovers; what's the best method? I don't have a spectrum analyzer (or whatever they're called) so it's pretty much done by ear, but I wanna ensure the comps and subs are getting the right freq range.

An easy quick way to do this is to set your HU vloume to 3/4 max, then turn up the amp gain until it starts to clip.

Your components have passive x-overs already so you will just need to use the high pass on the amp for them. Low pass for the subs 80hz is good then start your high pass at the same frequency. Those are good starting points.

[lizardking]

ALL, go to the www.jlaudio.com and read the tutorials on proper system setup including gains.. It's a basic start for someone wanting to learn... Remember though a DMM cannot detect clipping. You can pick up a decent o-scope for $150-$200.

[92TripleBlack]

Should work pretty good. Where did you find the Utopias? Did you get a good price? I used to have a site that had them really cheap sent from Europe but they went under so I don't have a good focal source anymore.
Thanks

[lizardking]

You can find them on Ebay, www.woofersetc.com, www.mobilesoundworks.com, and I think www.acaraudio.com and www.infinitecaraudio.com and I'm sure there are more then that...