Author Topic: Speaker problem (Read 253 times)

David Houck · « **on:** January 30, 2005, 02:54:56 PM »

I have a problem with one of my 2x10 cabs. I'm getting a thumping noise at low frequencies even at relatively low volumes. I took the screen off and pressed on the cones and there was no rubbing noise; they moved smoothly. When I'm playing, both speakers seem to be moving ok. Even with my ears close to each speaker, I can't tell which speaker is making the thumping noise. I used to know what caused this type of noise; I'm thinking it's something like the voice coil traveling too far. But my memory is shot; so I have two questions. What's causing this noise; and how can a determine which speaker has the problem?

David Houck · « **Reply #1 on:** January 30, 2005, 03:30:39 PM »

Well! It's not the speaker. I changed cabs and got the same problem. More testing.

serialnumber12 · « **Reply #2 on:** January 30, 2005, 04:00:23 PM »

dave it sounds electrical (at least to me).OHMS?

serialnumber12 · « **Reply #3 on:** January 30, 2005, 04:05:03 PM »

OR, you could have a failing speaker? which could unbalance your OHMS.

adriaan · « **Reply #4 on:** January 30, 2005, 04:11:24 PM »

You definitely get a loud thumping noise when a circuit board in the control cavity of your bass touches the shielding paint. You're sure it isn't just one bass having the problem?

David Houck · « **Reply #5 on:** January 30, 2005, 04:15:29 PM »

It's not the bass, I tried two; and it's not the speakers, I tried two different cabs. It's my new reverb unit. When I took it out of the chain, the problem went away. I have no idea why this would be happening. The thump occurs even if the limiter is in the chain after the reverb unit.

David Houck · « **Reply #6 on:** January 30, 2005, 04:32:39 PM »

I figured it out. Although the LED indicators showed that I was ok; I was actually overdriving the input to the reverb unit.

adriaan · « **Reply #7 on:** January 30, 2005, 04:56:39 PM »

Good catch!

David Houck · « **Reply #8 on:** January 30, 2005, 05:58:48 PM »

This TC reverb unit, while it sounds very nice and is very tweakable, may be a little too sensative for a stage rack. Because of an impedence mismatch, it makes a lot of noise when in the effects loop of the F-1X; so it has to be between the F-1X and the power amp. And with the SF-2 in the effects loop, I was sending to much signal out of the F-1X to the reverb unit.

Piece by piece, I reorganized my signal chain to keep from overdriving the reverb and to keep noise down. As a result, here's my chain. Bass to tuner to F-1X. Compressor/limiter in effects loop. F-1X out to TC reverb then to SF-2. SF-2 to power amp. That was pretty much the only way I could get it all to work.

Before I got this reverb unit, the limiter, SF-1 and my Alesis midiverb were all in the effects loop. Thus, I could use the direct out on the F-1X to send the sound to the board. Now I'm going to need to get a DI box for connecting to the house.

cntrabssn · « **Reply #9 on:** January 31, 2005, 11:06:11 AM »

Dave,

Quick question for you; What happened when you tried the the TC in the effects loop between the limiter and the Superfilter?

I was thinking that this could possibly work around the impedance issue, as long as the limiter was always active.

Thanks,
- nate.

David Houck · « **Reply #10 on:** January 31, 2005, 11:28:35 AM »

Hi Nate; I did try that but it did not help. Whether it was alone in the effects loop or after the limiter, there was lot of white noise.

To add to what I reported in the last post; even when all I was running was the F-1X and the reverb unit, with the reverb between the F-1X and the power amp, I still had to turn the volume down on the F-1X to around 5. I had previously left it at 8. But after working with the rig some more last night and this morning, I seem to have dialed in a nice tone, which I look forward to trying out at the next rehearsal.

son_of_magni · « **Reply #11 on:** February 01, 2005, 06:57:02 AM »

Dave, your TC unit is an M-One, right? There is an output range control that has 3 or 4 available settings (basically output gain stage). It sounds like you just need to turn it to a lower setting.
- SoM

David Houck · « **Reply #12 on:** February 01, 2005, 07:25:31 AM »

Hah!!! Thanks Karl! I thought I had looked at every thing in the book and checked all the possible settings, but somehow I missed it. It does seem that this could be the problem. Hopefully, I'll try to work on it today and see what happens.

David Houck · « **Reply #13 on:** February 01, 2005, 08:54:02 AM »

Well I worked on it for a while; and while the output range control was indeed related to the thumping sound, adjusting it did not really solve any problems. The unit still makes too much noise to sit in the effects loop. And even with adjusting the output range control, I still have to keep a lid on the amount of gain going into the reverb unit. So after trying various combinations, I still ended up with the same chain as outlined above.