Why is my amp clipping

Status
Not open for further replies.
Jump to Latest
T

trojantrow

Member
Joined 2015
#1
Any help appreciated

Anyway I can’t understand why my amp is clipping. I need to know if I’ve reached the limit of the sub or the amp or the AVR is sending too much signal.
I have the following equipment

Anthem MRX700 AVR
RCA output to
QSC RMX1450 bridged 8ohms (800w rms)powering a Alpine Swr1542d 15” dual 4 ohm Sub wired for 8ohm.

So most of the time it’s no problem. But I get clipping in certain bits of some movies when at reference level (-10 volume on anthem avr)

Now.. the anthem has sophisticated room correction called arc..

I have the QSC set at just over half gain which results in the test tones being around 65db.

When matches my fronts and rear speakers test tone levels.

So after calibration. The anthem sets everything at plus or minus 1dB (sub was actually 0db) so everything seems to be leveled correctly..

So am I right in thinking I’ve reached the limit of this amp? The sub is moving a fair bit so I think the limit of the sub is really close too coincidently. I did model it to be close.
 
#2
Chances are the room correction has put a big boost in there somewhere. Probably trying to EQ out a cancellation, which is never gonna work.

If the red lights are lighting up on the QSC amp, it's at the end of its tether. Chances are the sub will be near its limits, too.


My recommendation here would be, if possible, to try a few locations for the subwoofer, and use the position that requires the least EQ boost to get a good response.

Chris
 
#4
Thanks for the responses and I think there is some truth in this.

I’m not sat at a boundary. I’m sat in the middle of the room so peaks are already tamed quite considerably, I’m not sat in a position where that sub is it’s loudest. But the overall response is very good

But I do have a cancellation that’s doing my head in. At around 50hz at the seating position.

Sub is more or less quarter way in to room from left and at the front wall. It’s built in to the tv cabinet so can’t be moved. (Very strong and heavy)

So to combat this I’ve already got another sub. And cabinet I’m currently building of identical size that’s going in the opposite position to the first sub.

I’m hoping that adding the second sub will sort this issue out.

I’ve measured a speaker at the the other position and the 50hz dip is gone. So this should help.

I’m getting a inuke6000dsp to power them both so I can also mess with the delay and I’m also getting UMIK 1 mic and going to measure it all with REW

Does this sound like the correct plan?
 
#5
It does. But I would setup the dsp yourself using Rew to check the result. And then no room correction by the avr

If you can't get it right, you can also use the mso software for setting your dsp channels. However, it takes some time to learn to use that software.
 
#6
To be honest the room correction is rather good at sorting out peaks and smoothing things out .it’s know to be one of the best in the business... and it does a good job.

However it’s not perfect for every situation like some of the dips I am experiencing that won’t be there with the additional sub.

I will take your advice and use second sub with rew and see where I get.

Thanks
 
#8
trojantrow said:
I’m not sat in a position where that sub is it’s loudest.
Click to expand...

The deepest, widest null/dip [even order harmonic] is the center of the room, so assuming the mains, CC [and maybe more] are near/at a wall [odd harmonic/boost], then when calibrating the system it's going to boost everything by however much of the dip it measures plus anything else that's affecting the response of each component.

This of course not only drives the system harder, it could easily eat up most of the amp's dynamic headroom, so in theory better to move the LP to a room odd harmonic and recalibrate it, but probably not practical, so just some advice for future builds to maximize system efficiency.

GM
 
#9
It appears to have already been determined that the amp is clipping, and my first thought was to play with relative placement between the sub, the front mains, and the primary listening location - sometimes only a foot or two can make a huge difference - but it sounds like you might be snookered in that regard.
If you have any option to borrow another sub and play around with location, that might at least prove that point, and remember that the freedom of mobility of multiple smaller subs can be a big tool in the room acoustics kit.
What is the room size, layout and are there any major architectural/ traffic pattern or furnishing constraints? Those are often factors beyond practical or affordable control, but hopefully there’s some flexibility with placements.
 
Status
Not open for further replies.
Top Bottom