82801BA

Anyone here knows what is the correct procedure to level match for multiple amps?

I have PPI 404.2, Alpine MRV-T757 and MRV-T320, full active system, need to match level for each independently.

BTW, I forgot if PPI 404.2 is 4V or 2V, possibily 2V. If so, how do I level match the gain on the Alpine (4V)?

WhiteRabbit

id use a digital multimeter on the open end of the amp outputs, playing a sine wave through the cd player.

jttegx

iTrader: (3)

the manuals of the amps should state how.
but i think the basic rule is setting all your EQ's and settings to normal and/or 0. insert cd and play song of choice. play at 80% volume or til you hear distortion, set the gain/level back a little notch.

82801BA

How about using SPL meter and oscillator? If I have both, then how can I tune it?

82801BA

I don't know if it's my SPL meter's problem or my car's problem. When I measure each channel indpendently(Left tw, Rt tw, Lt mid, rt mid, left woofer and right woofer) I get the response of +7dB and +5 dB(boost) for passenger side midrage and woofer. Not sure if I've done something wrong or it's normal.

82801BA

I always suspect this method, you know, if EQ is done then using this method may be more appropriate. My reason is that, if you turn 80% volume FLAT, turn back when you here distortion to "safe" mode, then when you try to EQ the system, it will absolutely start to clip. Simply because for a flat, non-clipping response tuned to maximum level(matched with amp), then wherever it needs a boost it will just go pass the thresold of non-clipping. Cutting level at some specific frequency is another story. But it has no way to know either to use cut only or boost only. There may be some mix though.

82801BA

I also want to know the relationship between crossover output and amp input. ie. If I am to decrease the gain on the amp, is it the same as I decrease the output from the crossover(work the same way?)?

WhiteRabbit

oh! you are trying to match gain for different sized drivers!

I thought you were trying ot just match gain for two subwoofers.

well, the bottom line is that no two drivers will have the same gain in your car! not if you want it to sound good

your tweeters will have a different efficiency than your mids will have a different efficiency than your subwoofers. youll inherrently have different gain. if you match them and your tweeters are more efficient, your music will sound like you put in a pair of infinity references

as for left and right, thats all a matter of phasing. which speakers are on axis, which are off axis, and your proximity to them.

you cna use your o-scope to match the levels if you relaly wanted to, though. youd play a sine wave through each output and check the wave amplitude. itll be the same when the levels are matched.

as for inter-eqiupment matching, thats for your ear to determine. I always try to maximize gain at the opening of the signal chain and have it small as possible at the end. this doesnt always work though. the idea is to have ZERO audible noise and not get distortion at high volumes.

the iasca or usac zero bit track helps here.

edit: reread the question, interpreted it differently. if you have an active crossover with a line driver, yes, the gai nworks basically the same way. radio volume, amp gain, and line driver, all they serve to do is boost output voltage. its not exactly the same, as your radio volume and line driver boost output voltage, and the amp gain was designed to match input voltage, but you still at the end see the results with a multimeter. empirical testing I still think is the best way to set them, with confirmation from the oscope.

82801BA

Because I ouput analog thru PXA-H701 therefore I come up with this question about the output level though. I don't think it works as a line driver because my output from headunit is purely digital to H701.

82801BA

I do level matching by pointing microphone about 1 foot away from each side's determined "voice coil center", then from there I play each channel independently with appropriate crossover point. Use the theory that different frequencies do not sum up, I take the apparent SPL level(total peak stable) and set each speaker independently to that level. That's how I got a 7dB and 5dB boost on passenger side mid and woofer by the car, and I cut those outputs. Now it sounds pretty nice though.

Still, I found out that Dyns works extremely well with 6dB filter. No idea why, but 6dB filters (12dB on tweeter HP and mid LP for phase issue) gives me the most natural sounding and transition between high mid and woofer.

WhiteRabbit

dont forget that off axis your response will change radically, and those boosts may be off by several db at the actual listening position.

82801BA

So do you recommend that I take several measurements across the seating position(s), pointing toward the speaker and take the average of the measurement for this?

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How do you make a virtual "depth" on the sound stage?

WhiteRabbit

you know, ive always been kinda shitty with depth, so im probbaly ont the best person to ask. increasing seat distance from the speakers can help, but I hear that can hurt width.

as for taking measurements, id do it fomr the drivers seat and nowhere else, personally.

but remember flat sound doesnt neccesarily mean good sound! its how you get it flat!

82801BA

increasing seat distance from the speakers???????

Is it possible to do it? It doesn't work that good while driving(!!) unless may be driving between towns(2hour+) then it may make some sense.

Stage width wise, it's not that bad for now. But I have the left side LOWER than the right side, what's wrong?

WhiteRabbit

phasing.

kickpanels will increase your speaker distance as well as put the drivers more on axis.

you can also put your tweeters on the a pillars rather than the doors or sail panels to increase distance.

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That's how I corrected the passenger side height. I have the passenger side mid/woofer out of phase of each other and it brought up the height significantly. It seems harder on the driver's side though.....

WhiteRabbit

might try changing the x/o cutoffs

82801BA

Which one?

WhiteRabbit

drivers side mid/tweeter, starting with the tweeter.

82801BA

Mid tweeter? I think the only thing about mid/tweeter relationship is about where the "absolute center" will pull to which side. Are you sure?