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Stereo fine tuning

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Old 03-26-2006, 02:15 AM
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Default Stereo fine tuning

Got the new Stereo installed and trying to figure this stuff out. It has Front, Rear and Sub preouts. Only using the front preout leads, to feed an amp for the cockpit speakers, and the recievers speaker wires to feed the cabin speakers. The front L&R headunit preouts are connected to the 4 channel amp by means of a Y on each cable tieing the F&R channels together. The amp is also bridged for a sub. Is that the correct way to feed the amp? I can't use the rear preouts because of my setup.


Also, the headunit itself has LP and HP settings I can program off, or on to different frequencies. What's the best setting for these choices, On-off? The amp has built in crossovers, Eq and bypass for each side.
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Old 03-26-2006, 12:07 PM
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Default Re: Stereo fine tuning

Start around 80 to 100 hz on both HP and LP. This will prevent anything below those frequencies from reaching the small speakers and anything above those from reaching the sub. I prefer the lower of the 2 numbers but you have an 8" sub, it won't sound as sloppy passing 100 hz. If you have a filter steepness setting, set it to the highest number such as 24 db/oct is better than 12 db/oct in most applications.
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Old 03-26-2006, 12:11 PM
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Default Re: Stereo fine tuning

Thanks!
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Old 03-26-2006, 12:27 PM
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Default Re: Stereo fine tuning

Unsanes advice is good. Ussually you will run a gap btwn your crossover settings. Ie the low pass at 100K and the high pass at 120. I think I have a issue with the RCA's feeding the amp. Are you saying that you are taking your front and rear out of the head unit and then Ying them combining them into the amp? Or are you taking your rear channel outs of the head unit and y-ing them out to 4 inputs into the amplifier? The latter is acceptable the earlier is not. Give me a call (978) 985-0639 if you can.

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Old 03-26-2006, 04:09 PM
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Default Re: Stereo fine tuning

Quote:
Originally Posted by Audiofn
Or are you taking your rear channel outs of the head unit and y-ing them out to 4 inputs into the amplifier? Jon
Yes. That is how it is hooked up.

For a bit more info. Hopefully not to hard to follow.

The headunit has 3 settings of Off, 78Hz, 125 Hz for both LP and HP. I am not using the sub preout or rear preout RCA jacks of the headunit. Just the front preouts to feed the amp for the 4 cockpit speakers and sub. Both the headunits front and rear speaker leads are used to feed cabin speakers for use of the DVD player/TV. This way I can have sound out of the 4 cockpit speakers and fade the rear speakers in the cabin. The front cabin speakers are on a 3PDT switch , along with the amp signal wire, so they are off when the amp is on and on when the amp is off. Otherwise I can't fade them off from the headunit because the front preout is being used. This much all works as I want.

I do not know if the LP and HP settings on the headunit should be on since the amp also has those settings, but are varible. Or are those only for the speaker leads, not the preouts?

Can't find a picture of the amp showing the adjustment options. Other than it has for each side: 2 push buttons for LP and HP (In and Out), 3 adjustable knobs: Gain, EQ, and Freq.
The gains, I have figured. The rest is foreign to me. When I unhooked the amps speaker input side to adjust the sub, it plays the songs at a low volume. I was expecting to just hear it thump.
Just trying to get all the info out so if it does require a phone call, you'll be up to speed.

Thanks!

Amp specs:
http://www.mtx.com/caraudio/archive/pro50x4.cfm

Last edited by US1 Fountain; 03-26-2006 at 05:35 PM.
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Old 03-26-2006, 06:48 PM
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Default Re: Stereo fine tuning

Start the Headunit at 78. It probably has a very slow rolloff though. Try your amp around 80 or so and set the filter to 18db/oct. Take a listen. Then set the HU to 125 and bump the amp up around there and listen again and compare. In your case, it would not be unusual to set the HU at 125 but bump the sub amp down to about 100 or even 90 or so. Normally I don't like passing that much stuff to a sub, but like I said before, you have an 8" and that won't sound too muddy passing 125 or so, but I would not go any higher. The key is to get rid of the lows out of the little speakers so you can get more gain out of the system as a whole.
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Old 03-26-2006, 09:09 PM
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Default Re: Stereo fine tuning

Unsane: I think you made a boo boo. If he only has one set of RCA's going to the amp, and that amp is driving all his cockpit speakers, then he needs that crossover on the head unit to be set to off. If not he will kill his high frequency's to the mids/highs. Unsane said that there are 8" subs is this correct?

US1 lets go back to basics

IMO do not adjust anything on the head unit. Turn off any EQ's, turn off any bass boost, center all your balance, treble, bass make sure your cross over on the head unit is off. ONLY work from the amp to start with.

Your amp specs.
RMS Power to your full range speakers is 25 watts per ch.
RMS power to your subwoofer is 100 watts.
THIS IS AT 12 VOLTS

Your low pass crossover slope is 12db per octave. This should be pushed in
Your hi pass crossover slope is 18db per octave. This should be pushed in.

Since you have a small sub don't expact to get a ton of bass out of it. I would to start with turn the EQ to 0. The EQ is centered on 45hz and that is a little low for your 8 unless you have it in a very good enclosure. Start with Unsanes settings for the crossover. You will be kind of guessing the exact settings on this amp as it really depends on the amp but get it close it will work ok.

As for setting your gains I would start with the mids/highs down low. Bring up your sub as much as you can with out it distorting or clipping. Once you have that set then you should be able to match the mids/highs easily.

Jon
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Last edited by Audiofn; 03-26-2006 at 09:11 PM.
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Old 03-26-2006, 10:04 PM
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Default Re: Stereo fine tuning

I was meaning the High Pass, but no that I look at his setup again, you're right he can't use any filters on the deck because he'll kill the lows. (I misread the fact that he was NOT using the sub out)(I need that cataract surgery soon and glasses) So disregard my previous post US1. You have to send full range from the deck and do the tuning from each amp. There should be a second sub amp, I remember coming up with something for you, don't know if you went with that. If you have a seperate amp for the sub, set its filter around 100hz for starters using the steepest filter you have (18db/oct) and set the amp pushing the full range speakers to 100 hz, but it actually might be ok soundwise to set the filter at 12. Just play with settings a little bit. Make sure all EQ on the deck is off though. What you want to do is balance the subs with the mains. Play at different volumes and listen to the balance between the 2 and play with the levels a little bit just like Jon said, bring up the subs to clip and then blend in the mains for your overall tone.

PS: Jon, you still on for Fl in April?
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Old 03-26-2006, 10:46 PM
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Default Re: Stereo fine tuning

Thanks guys, That really helps alot. Starting to understand parts of it.

Unsane,
No, I did not get another amp just for the sub. AT least for now. I'm wanting to get the basics down 1st ,then go from there if it still needs more. Plus, really don't have the room to add a 2nd one if I don't need to. Space is a premium. Remember, this ain't no contest winner system. Just wanna make sure it is adjusted right for the best sound.

Audiofn,
The sub is in a box FG'd inside the rear bench seat storage. I forget exactly what it is called, but the sub itself is inside the box approx mid point, with the front of the box sealed airtight, and the rear of the box with a 1- 1/2" dia or so port.
When you say both the crossovers buttons need to be pushed in.... are you meaning all 4 of them? The 2 for rear channels that feed the cockpit speakers and the 2 for the front channels that are bridged for the sub? (Each side has 2 buttons and 3 knobs)

When I am adjusting the knobs to these numbers being mentioned, the amp doesn't have any marking for reference. So I assume by using the specs range from the link I posted, that I can use that as a guide to get in the ball park?

Thanks.
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Old 03-27-2006, 03:02 AM
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Default Re: Stereo fine tuning

I think that what you will find is that one of those buttons with be for cross over and the other will be for high pass or low pass. So one will be both in and the other will be one in and the other out. I looked for the manual but did not see it. I will try and search some more tomorrow.

Jon
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