What is this weird sound?

Here, pull my fing.... uh, check this video I uploaded:


http://media.putfile.com/Kappalite_weird_noise


This is my Eminence Kappalite 15" sub on an EP2500 amplifier. I had it hooked up in stereo. So the 8ohm kappalite was drawing about 450 watts.

I have been bothered by an odd sound. At first I thought there was something wrong with the speaker. But now, I'm not so sure. It may have something to do with my setup?

Onkyo TX-SR705 a/v receiver feeds directly into a Behringer EP2500 amp. I had the same problem with a Behringer BFD1124 in the chain also.

At the following db levels/frequency is when the weird sound starts happening. This is with 450 watts at full gain.

20hz @ ~72db
25hz @ 89.3db
30hz @ 97.5db
35hz @ 101.6db
3/4 gain = 99.8
1/2 gain = 95.7/106

If I move that down to 3/4 gain, then I get the weird noise at 99.8db with 35hz insteado f 101.6 earlier. If I move it down to 1/2 gain, then the noise starts at 95.7.

So then I went and bridge power to the kappalite. Now it's getting 1300 watts.

Now at 35hz, it doesn't start making the noise at 1/2 gain until 106db.

Does anyone know what this noise is? It doesn't appear to be bottoming out because the speaker cone is hardly moving.

I just hooked up the speaker to a Marantz home adio MA500 125 watt mono amplifier. I lost two db of total output, but otherwise had the exact same results.

I did notice though, that putting my DC leads on the MA500's terminals showed 0.00. But putting them across the EP2500's terminals showed 0.02. I'm not sure what that indicates though?

Btw, I'm able to hit 124db uncorrected at 48hz with the SPL meter next to the cone, before I get the buzzing machine-gun type sound.
This translates to 110db from 1 meter.

HTPC (M-Audio Delta 192 card) to Onkyo TX-SR705 to EP2500.


Doesn't matter what frequency, I still have the same issue. I experienced it at 80hz while testing a few hours ago.

I've killed just one speaker in my life. And it was a quick, smelly, frozen-in-position kill. So this sound is new to me. I've never heard it before and am puzzled.

Wow, good call! Taking the Onkyo out of the loop solved it!

Without the Onkyo in the audio chain, I was able to max the volume on my HTPC and the gain on my amp and hit high SPL's at all frequencies I tested, without any problems at all.

Well, now I just need to figure out why my HTPC & Onkyo are not playing well together.
I lowered the intellivolume to -6 on the HTPC input for the Onkyo, and still had the popping problem. I also lowed the sound card to 75% volume and still had the popping.

Thanks for helping out, John!!

Thanks again!

I have an Art Cleanbox II on the way. I don't know if it offers adjustable signal voltage like it's predecessor is advertised as having. But hopefully it will make some difference. If not, then I may end up with a DCX if I purchase a second Kappalite to run in tandem with my L&R mains.

I often get a couple of very small pops after powering off my EP2500.




I heard the original Cleanbox had the low frequency rolloff, but the Cleanbox II was not subject to this? I'll post before & after REW when I get it.

I did a lot of troubleshooting today. The only time I hear this weird sound is when the Onkyo is in the loop. When I remove the Onkyo from the audio chain, then the "weird sound" goes away. And also a stupid "hum" that I've been battling goes away.

I'm going to call Onkyo service tomorrow. I read up on the TX-SR705 main thread and it sounds like a lot of people are experiencing a hum problem with their Onkyo.

I've tried combinations of different amplifiers, cheater plugs, grounding chassis to chassis, with & without BFD, cabling changes, gain adjust from all sources, HTPC vs. HD-DVD, etc etc.

No. And I know this for a fact because I reproduced the problem in free air and watched the tinsel leads. They were both fine.

The problem occurs at about 3/4" of cone movement. Without the Onkyo in the loop, I get well over an inch of cone movement before I run out of power.