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 General Tuning/Clipping, basic tuning info
Posted: Jan 9 2009, 07:18 AM


Group: Member
Posts: 33
Member No.: 1,953
Joined: 8-September 08

Here is a tweaking process for getting the most from your subs and amp. Additional boom from the sub(s) is/are our main goal here, so will focus mainly upon that. Here we go:

Get out a few of your favorite CD's. Something with good mix and some low thump content. Dial back on the sub amp gain so there is very little sub in the mix. Turn off any bass boost features in the amp for now. May need a little later, but for now, no bass boost for now.

1. Set the EQ functions on HU to "0" or "flat" (no cuts, no boost)
2. Pop in the CD/tape/MP3 and select your favorite cut(s) and repeat.
3. Turn up the HU volume knob until you hear some distortions from the interior stage speakers.
4. Back off on the volume until distortions are gone. Is best to get out of the car and listen with doors open from a few feet away. If you still hear a rough sound, back off on the volume a bit more.

5. Now, time to add the sub into the mix. If amp has a low Pass filter, set it in a range between 70-120 Hz. No bass boost just yet. If you have continously variable LPF, determine what sounds best in your ears, within the range noted.
6. Bring up the gain on the sub amp, until you get it thumping and hear a "little" distortion.
7. Back off on the sub gain (a wee bit) until it sound full, deep and clean.
8. If bass seems a bit lacking of punch or deep lows, a small amount of Bass Boost, can be added. (+3 to +6dB is all you should ever need here)
9. Again, if you hear the sub getting rough from distortion, back off on the gain a bit more.
10. Now, you may use the Bass Tone control on the HU to adjust your bass from the driver's seat. This works well in simple HU's. But if you have a menu driven EQ system, this is a bit more cumbersome.

That's about it and now time for a test drive to ensure you have the system well balanced and in control. However, if you still have poor bass performance or weak bass output. May try reverse the wires to the sub and see if that improves the overall affect. If it gets better, you're good to go. If it seems worse, return the sub wires to original orientation.

This optimizing process, should get your
sub(s) up to par with the rest of your system. If not, something is off kilter here and needs more attention. Happy thumping! wink.gif

user posted image
Posted: Jan 9 2009, 07:24 AM


Group: Member
Posts: 33
Member No.: 1,953
Joined: 8-September 08

First off, let's define CLIPPING distortion...

This is when an amplifier has reached its maximum output capacity yet tries to keep up with the input signal gain ratio between the signal source "HU" and Amp. The amp hits an imaginary wall whereby the output signal is no longer a symetrical replication of the input signal. The wave form in, does not match the wave form out in shape or amplitude. (you can see this easily if you had a A/B channel oscilloscope; channel A connected to the amp input, channel B to amp output) The only difference you should see between channel A & B are signal amplitude values. If the signal shape varies considerably in channel B, you have a problem with clipping.

So.. what's wrong with this picture? The amp tries to put out the appropriate power, but runs out of voltage from the supply rails and we get a flat spot at the upper and lower peaks of the wave form. In an extreme case, "severe clipping", there is so much additional energy buildup (heat) into the voice coil(s), but the cone does not move (motivate) enough to cool the voice coil and former adequately. Hense, the voice coil over heats and either seizes in the gap or burns the voice coil windings. RESULT: OPEN CIRCUIT and a blown speaker!

OK, what happens to the speakers when they are underpowered? Under normal listening conditions... NOTHING! There is adequate signal voltage from the amplifier to motivate the speaker. This moves the speaker cone and draws/expells air to cool the voice coil adequately. No problems here... just modest output from the speaker. This happens all the time when we ride with the tunes playing low enough to hear our buddy in the co-pilot seat chattering on his/her cell phone.


Yes... When we use a small amp to drive a high powered speaker, the speaker can take all the "clean power" the amp can deliver and more. But it's when we push the amplifer into high distortion ("clipping") mode, the speaker cannot move (motivate) in and out adequately to cool the voice coil. Eventually, this will even fry a very expensive speaker in this manner.


Glad you asked! The amp will try to meet the power demand placed upon it, but it cannot exceed its design capabilities. This in turn, produces the deadly "square wave" output to the speaker. The speaker sees this severely clipped signal as something similar to DC current. Speakers cannot deal well with DC inputs. The cone goes in or out and stays there. No motivation to cool the voilce coil and sooner or later, the speaker will fail.


Alright, we know what clipping is, how it affects amps and speakers. What do we do to keep this problem from destroying our expensive drivers? Easy deal:

1. Use amps that closely match or modestly exceed the power rating of the speaker. A 100 watt speaker will love getting 125 watts of "clean power" vs a 100 watt speaker getting 25 watts of badly clipped (distorted) power.

2. Know what distortion sounds like and prevent it by proper amp setup procedures. (HU/amp gain matching, limited bass boost usage)

3. If you are not sure your system is clipping, best thing to do is get out
of the vehicle, open the doors and step to the rear of the vehicle about 10 feet and listen...

a. Are the highs and mids clear and natural sounding or harsh, shrill and very poor SQ? You are clipping the amp if you hear the latter!

b. Does the bass sound full, tight, have a definite thump and smooth transitions from one note to another? If not, good chance the sub amp is clipping or your enclosure design is not optimal for the subs.

OK, that's about all I can do for now on this topic... Class dismissed and PLEASE... NO CLIPPING ALLOWED !!! You will eventually pay the piper! tongue.gif

user posted image
Posted: Jan 9 2009, 11:01 AM

D' AuDiO TeCh MoD

Group: Moderator
Posts: 2,324
Member No.: 1,994
Joined: 16-October 08

nice info markzz

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