DerrickM

Hopefully Elduderino or somebody can offer some insight into this:

I'm getting occasional distortion in my tweeters at high volumes. Doesn't happen all the time, but it is definitely volume-related. The speakers are high-end, and are not getting anything near what they're rated at. The amp is a MTX 4x70 rms, double that peak, with 93 wpc on the birthsheet. (MTX 564--560 watts max, 4 channels).

How can I measure to see how much power I'm getting when the distortion starts? (I want to know if it's the amp).

It's not the speakers, because my old tweeters made the same distortion at the same volume.

The one really bad thing I'm doing: using a relay to switch the preamp signals for my cd changer. (So, the preamp signal goes through that even when the cd changer is not in use). I'm going to bypass this relay tomorrow to make sure the distortion is not coming from there.

Here's the equipment in question:

sony cdx-c90, sony xdp-210eq, mtx 564, dls ur6, 12awg wire with no breaks or connectors.

elduderino

What's it sound like? And what instrument does it happen with?

If you have access to a signal generator or a sine-wave sweep disc (old Alpine CAN disc?) see if it's happening at a specific frequency.

The other thing to check is with a discman or something like that and see if you have the same issue.

Bass Mechanic

hmm are you running subs on the other 2 channels?

DerrickM

Hi,

It seems to happen with prolonged high-notes, like upper female vocals holding a note--but only at high volumes. This was happening on the fronts, can't say about the rears yet, because I'm still installing them. (The sub is a seperate amp).

My notes for tomorrow are as follows:

1. bypass relay
2. hook up studio monitors to amp to see if it happens there
3. use a home CD player with a noise supression coil to bypass the HU

I do have some test CDs laying around somewhere from my last system install a couple years ago--I'll see if I can find them.

elduderino

Those are very good tests... let us know. That's why I like the Discman on batteries...: )

Scott P

out of curiosty can you adjust the crossover to like -1db or something of the sort. I've run into similar problems as such with our components on our sound board at work and usually all it takes to correct it is simply readjust the crossover.

DerrickM

That's an idea. The crossover has two jumpers, tweeter level, and tweeter slope adjustment. (The second one has low/high settings for if the tweet is close to the mid or not--I could try that one, as the level is already at the lowest settings.

But, since the last speakers did the same thing, I think it's too big of a coincidence to be the speakers. I'll let you know how the testing goes this morning.

DerrickM

Okay, it was the relay. Note to self: don't send signals through relay contacts. I just bypassed it for a couple days to see if that was it, and the sound is pretty much perfect at this point. I ordered a Sony xa-300 aux adapter, like I should have done in the first place.

I'll go start a new thread to tell everybody how happy I am finally...

elduderino

Uh, I don't know how the xa-300 works (it might have a solid-state MUX IC in it) but lots of switchers like that have used relays. Just sounds like some weirdness at a certain power level... glad it's fixed!