SDA or cross-channel echo / channel / phase delay?

lawdogg

I have been noticing this intermittently (rarely and unpredictably) with my 3.1TLs for a little while now, with two different amps (both definitely common ground, a NAD C370 and a NAD 2200PE).

The effect is just that, an echo. I usually notice it during dialogue in something I'm watching. I always seem to think it's a channel echo - as in the right channel getting to my ear a split second before the left channel - but it also could, I suppose, be a delay of the stereo channel getting there before the SDA channel. But if I watch / listen to the same playback again, no echo. So no repeatability (as far as I can tell) which makes solving it challenging.

I did some poking around and found a few mentions of this in the past, with no definitive cause or solution - other than some people fixing positioning or wiring or some other setup-related thing (see list of links for some examples of past discussion).

My crossovers are 100% original and sound great otherwise - although it isn't hard to imagine that a grossly out of spec component could cause such an effect. The curve ball being some discussion of the "echo" effect even with newly rebuilt crossovers.

Would love thoughts / comments / insight / suggestions. Thanks!

http://forum.polkaudio.com/discussion/167082/sda-2a-question
http://forum.polkaudio.com/discussion/130566/sda-2
http://forum.polkaudio.com/discussion/159842/voice-echo
http://forum.polkaudio.com/discussion/comment/2299945#Comment_2299945
http://forum.polkaudio.com/discussion/comment/2233669#Comment_2233669
http://forum.polkaudio.com/discussion/comment/1783405#Comment_1783405
http://forum.polkaudio.com/discussion/comment/1396925#Comment_1396925
http://forum.polkaudio.com/discussion/comment/887141#Comment_887141

lawdogg

The echo showed up more often recently during the Stranger Things 2 marathon. Nobody ever hear this from their SDA speakers?

F1nut

Say what......what......what.....

xschop

Since the signal is flipped 180 deg. and delayed, could an echo elucidate an intermittent SDA driver (eg voice coil or connection issue)?

nooshinjohn

I would begin by addressing the crossovers. There is nothing good in a 40year old crossover.

pitdogg2

nooshinjohn wrote: »

I would begin by addressing the crossovers. There is nothing good in a 40year old crossover.

Inductors are good

delkal

Are you sure that absolutely no sound is coming from your TV's speakers. When I set up my surround sound speakers I left the TV's speakers active so if I didn't want to turn on the stereo I could still watch TV. But every now and then I would get the remotes mixed up and both would be on. I got a definite echo every time.

lawdogg

Thanks guys - I'll check the SDA drivers and make sure they're good, and then maybe start to plan the crossover rebuild!

The TV volume definitely is noticeable when it's left on - but immediately gets turned off!

delkal

It is hard to believe a defective resistor or capacitor is some how "delaying" an electric signal. Distorting Yes, but delaying No.

Upgrade your crossover. It will sound better. But I do not think it will solve your problem

pkquat

What is the time delay of the echo? I played around with some mono material when first got my 1C's. If pointed one speaker away from me and got close to the other while pointing one ear at it I got more of a cancellation - reduced volume effect than any delay. I had originally thought SDA's had a built in delay circuit, but everything is close to real time, well under milliseconds, and probably less than microseconds. The cancellation and any delay is from the speaker spacing.

If it is like a millisecond range echo, I would have to think something else is going on upstream. Otherwise, I would have to vote that somewhere something is loose. Maybe have someone connect and disconnect the interconnect (at your own risk... I am not sure if that is a really bad thing to do) for something like a mono test tone and see if you hear a pulse or some other change in the sound as the sound stage changes. If my interconnect is not connected I loose my razor sharp center, most likely because the speakers are not toed in some.

delkal

pkquat wrote: »

What is the time delay of the echo? I played around with some mono material when first got my 1C's. If pointed one speaker away from me and got close to the other while pointing one ear at it I got more of a cancellation - reduced volume effect than any delay. I had originally thought SDA's had a built in delay circuit, but everything is close to real time, well under milliseconds, and probably less than microseconds. The cancellation and any delay is from the speaker spacing.

If it is like a millisecond range echo, I would have to think something else is going on upstream. Otherwise, I would have to vote that somewhere something is loose. Maybe have someone connect and disconnect the interconnect (at your own risk... I am not sure if that is a really bad thing to do) for something like a mono test tone and see if you hear a pulse or some other change in the sound as the sound stage changes. If my interconnect is not connected I loose my razor sharp center, most likely because the speakers are not toed in some.

I don't understand how capacitors and inductors can delay an analog signal. From my limited understanding I can see how the SDA crossover can change the phase of one speaker. But not put in a delay.

I am still leaning that the OP had his TV speaker on too. If you run a digital signal thru 2 different DACs I can see how a delay can be introduced due to different processing times. You can hear this if you ever went to a sports bar and listened to two 2 different TVs playing the same broadcast. There is often a delay or Echo.

I can get this on non-SDA speakers at home. The next time the OP hears this echo He should double check his TV volume. Even if it is playing really low it can mess things up. I ended up turning my TV speakers off

If it is something different it is a real mystery!

lawdogg

Definitely don't have my TV speakers on when I hear this. I'm not that oblivious, I promise!

TennMan

lawdogg wrote: »

...
The effect is just that, an echo. I usually notice it during dialogue in something I'm watching. I always seem to think it's a channel echo - as in the right channel getting to my ear a split second before the left channel - but it also could, I suppose, be a delay of the stereo channel getting there before the SDA channel. But if I watch / listen to the same playback again, no echo. So no repeatability (as far as I can tell) which makes solving it challenging. ..

I think you might have an intermittent connection to one of the SDA drivers. The next time it happens check to see if one of the SDA drivers has stopped working. You probably won't be able to tell by listening to the driver but you can feel for vibrations with your finger tips.

gmcman

I don't know how you have your system hooked up, but does your receiver or preamp occasionally change back and forth from DD 5.1?

Are you experiencing this through a DVD, Cable, satellite?

[Deleted User]

I'd go into the TV's menu for audio settings and make sure some kind of goofy two channel "surround sound" processing or some other sound affect isn't turned on.

K_M

If it is intermittent as the O.P. says, and playing the same section over immediatly gets different results, with no other changes made, that would lean to something intermittently changing, maybe loose connections somewhere or an intermittent driver?