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Here's an article I wrote a few years back that may be of interest to some of you DIYers. It is not brand specific and can be used with any conventional amplifier setup. Hope some of you find this useful.





 

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Any easy way to get consistent results:
It's the second movie listed: Movie

Some manufacturers supply voltage settings for their amps. If your amp does not have these, here's the formula you can use:

Voltage = Square Root (power (watts) x resistance (ohms))

For example:
If I had a 500 Watt amp conected to a 4 ohm subwoofer, I would use the above formula.
V=Square Root (500x4)
V=Square Root 2000
then hit the Square Root (looks like a V) button on the calculator
V=44.7

It makes sense to use a 1K Hz tone for the high frequency amps and a 40 - 50Hz tone for the bass amp. It's important that the tone is 0dB reference. A disk I have used for years is made by Autosound 2000 titled CD 104

If you are paying a professional to install the amplifer ask him how he set the "gain". If he says "by ear", ask him to please do it this way (or any of the other reliable ways). The increased average power brought on when severe clipping starts will cause headaches.
Extra power means extra heat (on the amp and the voice coil). There are a lot of sonic things that spring up, but it you are a knuckle-dragging mouth-breather, you don't care about those.

Everyone drives their system into clipping. No one would be happy with the output of a zero-clipped system. Even "golden-eared" audiophiles can clip their systems 10dB without even knowing (especially with music). The reason the 3/4 volume was chosen to set "gain" was no head unit has seemed to clip their outputs at this point. When you go beyond the 3/4 mark (and you know you will) you move into the realm of moderate clipping which all sane people do!

Watch the movie a couple of times, you'll see it's only like a 2 min process!
You have my permission to pin this.
 

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Thanks guys, thats helps super lots.
 

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If you just want to make your own test tone and burn to cd, this is a great program to do it. It also defaults to 0db.

Oh, and its shareware.

late
 

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i am using line level inputs on my infinity amp with gains all the way down and I can still overheat the bitch (mounted next to spare tire w/no fans at the moment) if a bump the thing max for an extended period of time ... I can't imagine what would happen if i turned the gains up.
 

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I realize this is quite an old post, but all the links are dead. JLTD, can you fix the links or update your post.

I found a program that you can use to generate test tones (including pink noise). Obviously enough its called the "Tone Generator Software".

Thanks guys.
 

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ok so i did what this page said to do, using an AC voltmeter like suggested.

http://mobile.jlaudio.com/support_pages.php?page_id=143

I also used the whole Voltage = Square Root (power (watts) x resistance (ohms)) thing to get the number needed before i started.

Using a 50hz test tone i can not get to the voltage needed(only about 1/2 way)

Using an alpine MRD-M605, 600watt RMS amp.

Voltage = Square Root (power (watts) x resistance (ohms))
600wattx2ohm = 1200, square root = 34.6

At 3/4 volume and full gain of the amp i get about 18.

So either im doing something wrong, or this can not be used on an alpine amp? I really dont want to do it "by ear" so any help would be great.
 

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Originally posted by $The TC$ @HTown@Jul 25 2006, 05:39 PM
sorry, what is it you're trying to do? Tune your amp?
smart ass's still spit #### and burp gas.
 

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Listen homo (wmccauley)...i'm trying to figure out what this guy is trying to do. SO blow me.

OP: Start with the volume on your headunit and gain on the amp both at ZERO. Turn up the volume on the headunit to about half-way or 2/3 of your maximum listening level (the max listening level is the loudest you can push your speakers without distortion or clipping). Now, slowly turn up the gain on the amp and you'll hear the bass volume start to get louder. Keep turning up the gain on the amp until you reach a satisfactory level of bass output, or you start to get distortion. If you DO hit distortion or clipping at a high gain settting, turng it back down a notch or two.

You don't need any voltage calculations, just a good ear.

Hope this helped. if not, i'm not quite sure what else you're trying to accomplish. Let me know if you got any more questions.
 

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ugh, I am LIKE SOOOO offended

oops heavens to betsy, my wrist just went limp,

htown? houston? i heard the people there are simple. must be the reason why everything the alpman is talking about can be done with a good ear, right?
 

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Come on, fellas; keep it to PM, please.

-Ed
 

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Originally posted by Davie_06_tC@Jul 25 2006, 11:11 AM
Using an alpine MRD-M605, 600watt RMS amp.

Voltage = Square Root (power (watts) x resistance (ohms))
600wattx2ohm = 1200, square root = 34.6

At 3/4 volume and full gain of the amp i get about 18.

So either im doing something wrong, or this can not be used on an alpine amp? I really dont want to do it "by ear" so any help would be great.
The process should work just fine on your Alpine amp, and any other brand out there.

With a 0db 50Hz tone, and your digital multimeter set to AC, your target is ~34v.

As stated in the article, amplifiers have gain controls because of the varying strengths of preout votlages available in source units;

For instance, I have an Alpine CDA-9830. The advertised preout voltage is 4v. In order to realize anywhere near that voltage, the Subwoofer setting on the headunit needs to be way up there, one click from max.

It really depends on the headunit; Some will clip with a tall subwoofer setting, some will not. Music is dynamic anyway, and as much as there is a science to it, it's also not quite as fragile as all these calculations would have you think.

(You should see the formula to calculate the area of a port to give your enclosure a particular peak frequency. Another post, maybe.)


* Are you running one dual 4 ohm subwoofer? Your calculations have 600wrms into a 2 ohm final impedance as your target.

To run that amp at 2 ohms, it should be "bridged"

In other words, when you're touching the terminals on the amp with the multimeter leads, you should be touching the leftmost, and rightmost terminals. (1 and 4)

+ - | - +
1 2 | 3 4


Here are some things to check:

* On the amp, turn the SSF (Subsonic Filter) all the way down; If it's up too high, it could be affecting the strength of your 50Hz signal.

* On the amp, turn the LPF (Low-pass Filter) all the way up; Again, it could be altering your 50Hz signal.

* On the headunit, set Bass Boost off (and leave it there - forever.)

* On the headunit, set Bass level to flat; (in the middle.)

* On the headunit, set the Subwoofer level to 3/4, or near maximum.

Best of luck;

(first post, for the win.)
 

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* I should add,

If your subwoofer is in a sealed box, I'd set the SSF to ~20, and the LPF to ~80

If it's in a ported enclosure, and you don't know the enclosure's tuning, set your SSF a little higher; ~30 is a safe bet. LPF to ~80.

This all depends on the enclosure, processing at the headunit, and the theile/small parameters of your subwoofer;

But I could go on for days, and those settings are pretty widely accepted as a good, safe default.

* Heaven help you if you have a Bazooka tube. Garbage.





* Good sticky, OP.
 

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Hi thanks for your reply. However one problem i see with your reply is you tell me to bridge the amp. Its a mono amp with only 1 set of speaker outputs


However what i did not do to increase outcome was, i did not turn up the power to the sub from the headunit...i left that at zero. I guess that is where my problem came from then?

Again thanks so much for your reply.
 
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