4 channels bridged to 2, midbass making a 'thumping' sound.....clipping???

[Latina33 10+ year member]

I've got an Alpine MRD F752 Class T 5 channel amp....I've got channels 1-4 bridged to my Crystal SSCS6 components up front, which is giving them approx. 200W RMS a side. Channel 5 is powering my 12in sub.

When I got these all installed a couple of weeks ago, I turned the gains WAY down on the amp (basically to 1/4 of their adjustment range), and it seemed as if I had way too much bass, and not nearly enough mids and highs. So I adjusted the gains up just a notch or two, and when I played my CD's at the same volume as before, I noticed my door speakers making a 'thumping' sound....like they're getting too much power. Is that the 'clipping' that you guys refer to all the time? It's not a good midbass sound.....it sound like the woofer is being over-stressed.

Is that happening because the speakers haven't been broken in yet, or because my gains are most likely set too high?

Any input would be appreciated!

Click to read more...

 

[btlking 10+ year member]

i think there bottoming out try turning your gains down

 

[Latina33 10+ year member]

i think there bottoming out try turning your gains down

Cool, thanks btl....that's what I was thinking, but I just wanted to post it up here to get some feedback from more 'experienced' peeps.

As speakers are broken in over a few weeks, such as my Crystals, should they be able to handle the gains being turn up a little more, or is this usually not the case with higher end components?

 

[bbaccord 10+ year member]

Check that they are crossed over properly. High passed at around 80Hz is a good place to start. I would not go any lower than that, especially with that much power. They should be able to play quite loud without bottoming out.

I'm not too familiar with that amp but make sure the crossovers are enabled and set properly.

 

[Latina33 10+ year member]

Check that they are crossed over properly. High passed at around 80Hz is a good place to start. I would not go any lower than that, especially with that much power. They should be able to play quite loud without bottoming out.
I'm not too familiar with that amp but make sure the crossovers are enabled and set properly.

Thanks, bbaccord. I've got my front and rear crossovers on my HU both set to 100hz, with the rear adjusted to a -3 slope. The sub crossover on the HU is set at 80hz. If I set the front and rear HU crossover points, to 80hz, man, I really get some unwanted 'thump' from my midbass! I've got to adjust, and turn the volume way down if they're crossed over at 80hz.

I've attached a pic of the gain/eq/crossover panel settings on my amp. The top two at the left are for my bridged components. As you can see, they are barely turned up over the second notch.

 

[bbaccord 10+ year member]

Is there a bass boost on that amp by any chance? Make sure it's off or turned down all the way. I 'm sure you checked that already anyway...

What HU are you using and do you know what slope the crossover is?

 

[Latina33 10+ year member]

Is there a bass boost on that amp by any chance? Make sure it's off or turned down all the way. I 'm sure you checked that already anyway...
What HU are you using and do you know what slope the crossover is?

Yeah, there's a bass boost adjustment on the amp, but it's grouped with the adjustments for the 5th channel, so I assumed that it would not affect the frontstage speakers at all. Now that you mention it, I'll just turn it down all the way, anyways, just to be sure.

My HU is the older Alpine CDA 7998, and right now for the front and rear crossover points, I've got them both set at 100hz. The front has 0 slope, and I've set the rear setting at -3. If I keep the rear setting at 0, like the front, I can hear the Crystals begin to thump a little.

The SUB crossover setting on the 7998 is set at 80hz, with 0 slope.

Any suggestions? Thanks again, bb!

 

[chucku 10+ year member]

I have had to crossover mids at up to 130 hz to play loud without bottoming out with alot of power. Try more adjstments.

 

[bbaccord 10+ year member]

I just quickly went over your manual on alpine's website. The 0 and -3 you set are the speaker levels, not the crossover slope. To view/set the slope, first you use the UP/DN buttons to select the crossover frequency. Now don't turn the knob, press the SOURCE button to browse through the available slopes. Make sure it is not set to flat. Your options are flat, 6, 12, 18 and 24 dB/oct. At the bare minimum, use 12dB. If that doesn't cut it, try a higher slope or raise the crossover frequency altogether. Let us know how it turns out.