Subwoofer bottoming out? - AVS Forum
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post #1 of 11 Old 07-15-2011, 12:33 AM - Thread Starter
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I have my Sound Splinter RL-P15 in a crappy 100 liter sealed box temporarily until I get my ported enclosure built. Modeling the sealed enclosure in WinISD, and entering 900 watts from a Crest CPX900 which is powering the sub, it shows that the subwoofer should not reach its xmax at any frequency.

Reaching the xmax is the same as overexcurting, or "bottoming out", correct?

If so, why does my subwoofer bottom out on certain songs at high volume?

I do have the gain up considerably, about 3/4ths of the way, which is fine for most songs. At what point will bottoming out cause damage to the sub that affects sound quality? How can you tell?

I would think that with the subwoofer gain turned to 100%, this would equate to 100% max potential of the amp, which in my case would be 900 watts. Is this correct or am I mistaken?

I do notice some of the amp "clipping" lights come on when the sub bottoms out, I'm not sure if this has to do with it, as I thought the amp clipping would only affect the amp and not the sound of the sub.

Are the red clipping lights damaging my amp or sub? I thought that my amp had some kind of system built in which protects it from clipping.

Also, since I'm using a pro-amp, I had to bump up the subwoofer level within my Denon AVR-2307CI to +12db to provide enough voltage to power the sub. Could this be causing distortion or anything? Would I be better off to get a line level booster, or would it essentially do the same thing? At what point does the increased voltage cause sound distortion?

Thanks for any help.

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post #2 of 11 Old 07-15-2011, 12:37 AM
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You sure you aren't just clipping your amp and not the driver? It makes an awful sound.


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post #3 of 11 Old 07-15-2011, 12:57 AM
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Quote:
Originally Posted by rocko1290 View Post

Reaching the xmax is the same as overexcurting, or "bottoming out", correct?

Exceeding xmax...
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If so, why does my subwoofer bottom out on certain songs at high volume?

Too much power...
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At what point will bottoming out cause damage to the sub that affects sound quality?

As soon as it starts...
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I would think that with the subwoofer gain turned to 100%, this would equate to 100% max potential of the amp, which in my case would be 900 watts.

That is 900 W RMS. Peak power can exceed that considerably.
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post #4 of 11 Old 07-15-2011, 01:04 AM
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Is your RLp15 a d4 or d2 model? I ask because they have pretty different t/s specs. The d4 model would fit in a 100 liter cab and with 900w it would be fine cuz the Qtc is ~.7-ish. The d2 in a 100 liter cab would be slightly over .5 which is pretty low. With 900w you will go past xmax below a certain point (around 12hz and below) so be careful not to damage the voice coil former.


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post #5 of 11 Old 07-15-2011, 01:24 AM - Thread Starter
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Quote:
Originally Posted by Scott Simonian View Post

Is your RLp15 a d4 or d2 model? I ask because they have pretty different t/s specs. The d4 model would fit in a 100 liter cab and with 900w it would be fine cuz the Qtc is ~.7-ish. The d2 in a 100 liter cab would be slightly over .5 which is pretty low. With 900w you will go past xmax below a certain point (around 12hz and below) so be careful not to damage the voice coil former.

It's the D2 model. Are you sure? The WinISD model shows the excursion at about 14mm at 10hz with 900 watts power...that's about 10mm of xmax to spare..even when I bump the power up to 1500 watts it still doesn't exceed the xmax..

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post #6 of 11 Old 07-15-2011, 01:24 AM - Thread Starter
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Quote:
Originally Posted by notnyt View Post

You sure you aren't just clipping your amp and not the driver? It makes an awful sound.

Perhaps..it sounds like the subwoofer is clanking against something..I assumed it was bottoming out..I didn't know amp clipping could cause distortion...

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post #7 of 11 Old 07-15-2011, 01:28 AM - Thread Starter
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Quote:
Originally Posted by Colm View Post

Exceeding xmax...{

Quote:
Originally Posted by Colm View Post

Too much power...

How so? According to the WinISD model, the driver won't exceed xmax in this enclosure.
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Originally Posted by Colm View Post

As soon as it starts...

You're telling me that I've already done permanent damage to my subwoofer because it bottomed out for a few second on a few occasions?
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That is 900 W RMS. Peak power can exceed that considerably.

I see. Is there a way to tell how much power is being delivered at a certain gain level? That way I won't be doing damage to my driver?

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post #8 of 11 Old 07-15-2011, 04:18 AM
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To much power will damage subwoofer cause of heat damage, if you exceed thermal limits, or if you physically damage voice coil due to overexcursion. I have always read that distortion will damage speakers just as quickly as to much power.
Correct me if I am wrong here guys, but isn't over driving an amp to the point of clipping, the main reason for a distorted signal getting to a speaker?
It sounds to me that you have the gain set to high, remember, gain is not volume. It's purpose is for you to give the amp the abilty to reach is full potential, with whatever signal you feed it. What I mean to say is, if you are driving your amp to clipping, and you are not at full volume on your avr the obviously you have it set a little hot. Which is fine if you have the headroom, but as the clip lights on your amp indicate, you do not...

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post #9 of 11 Old 07-15-2011, 07:50 AM
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Quote:
Originally Posted by rocko1290 View Post

Perhaps..it sounds like the subwoofer is clanking against something..I assumed it was bottoming out..I didn't know amp clipping could cause distortion...

I was in the same boat about a month ago with my THT LP - I thought it was bottoming out, as it would periodically made a horrendous clunk sound - but in my case, the signal level from the AVR to the parametric EQ (BFD FBQ2496) was too high, and causing the EQ to clip. I finally found a specific reproducible test case and watched the front panel lights during the test case, and every time I heard the sound coinciding with clipping.

The solution in my case was to turn the power amp (QSC RMX850) gain all the way up, and re-run MCACC to reset the sub trim level (went from +3 to -6 or something). So the same net output level, but less signal at the EQ input stage.


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post #10 of 11 Old 07-24-2011, 11:52 AM - Thread Starter
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Often times the red lights come on the amp even when the sub sounds good...

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post #11 of 11 Old 07-24-2011, 12:29 PM
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$100 says the amp is clipping. Hook it up to a 100w amp and send it into clipping and it'll do the same thing, especially if the d2 driver is running a one ohm load to the amp. I've had this happen before as well, just get an amp that has plenty of headroom.

Dan

Oh and I wouldn't set the gain to 100%. You don't need it that high to get the full potential out of the amp, it's not a volume control.
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