Diagnosis help needed: left speaker making noise while amp is off

[Soundserge]

Hello all, I need some help figuring this out. I'm pretty sure the bottom line is "Expensive", but still...

I have a Jeff Rowland Model 2 power amp with Dynaudio Contour 1.3SE speakers. Amp is plugged into a Running Springs Audio power conditioner.

Last night I listened to music as normal, put preamp (Meridian 818) into standby and pushed the power button on the Rowland (which technically puts it into standby, I believe)

I went to bed and came downstairs the next morning to find the left speaker making a squeaking noise. My half-asleep response was to pull the plug on the power conditioner. This took care of it, as expected.

Plugging the power conditioner back in to the wall, the squeaking and a static came back again immediately, without having to turn anything on otherwise.

There's a distinct smell coming out of the left speaker's port that isn't there on the right. Not quite a burning smell, but it's like you can smell electronics if that makes any sense.

I suspect the Rowland's left channel croaked in some way and probably damaged my left speaker.

Nothing out of the ordinary is visible on the outside of the speaker or the amp.

What do you think?

Thanks,

Soundserge

[Randy Myers]

You could try flip the speakers to or the speaker wires to verify the speaker. probably best to not do this until sure about the amp though.

I would probably call Jeff Rowland abut the amp.

[Soundserge]

Thanks Randy. I've been hesitant to swap speakers for fear of damaging the known good speaker. Plan is indeed to call Jeff Rowland on Monday.

Soundserge

[piolaxo]

Do you have a ohm-meter? With one you can check the resistance of the speakers. Normally
blown speakers get open so you would see a OL or OR (out of range). The other possiblity is
that the resistance is near zero which means that your speakers have a short and yes,
you don't want to connect them to your amp.

If the speakers measure between 4 and 8 ohms (even down to 3 ohms), then they should be good.
In this case, you can connect them to another amp that you know is good and then test them.
This will prove if your speakers are good or not.

If they are good, then things will point to your amp.

[Soundserge]

Thanks for the advice piolaxo, I will track down an ohm meter. I was going to try the speaker on another amp but I will wait to confirm the speaker's resistance is in normal range.

Soundserge

[audio bill]

Just one point regarding measuring a speaker's impedance that you should be aware of. You can use an ohmmeter to check for an open (infinite) or a short of a speaker, but don't expect that you'll be measuring the actual value of a speaker's impedance. An ohmmeter measures DC resistance while a speaker's impedance is a complex value which includes a reactive component that an ohmmeter will not measure.

[Soundserge]

I'm seeing ~1ohm on the suspect speaker and ~4ohm on the other, measured at the terminals.

¯\_(ツ)_/¯

[piolaxo]

So you have one suspect speaker. From the Technical Specification the impedance
from 20Hz to 200Hz should be from 3.6 to 23.9 ohms. So the DC resistance that you
measure should be close to 3.6 ohms, so at ~4 ohms, your second speaker is good,
but your concerning one is not.

If you want to investigate it further, to rule out a coil in the crossover or the woofer,
you can take the woofer out and measure its resistance. Again since the
woofer fits in the above mentioned range it should measure close to 3.6 ohms.
If it does, then you can turn your view to the crossover which is the best news,
but less probable.

We should rule out the tweeter since it is most common that when the tweeter goes,
it becomes open so there is no sound coming from it and its crossover (cap in series)
will work as coupling cap if a DC signal will be let past by the dammaged amplifier.
In other words, the tweeter could be out, but it won't cause the short.

Now, if the woofer is dammaged, it may be because of the dammaged amp which is
the other more worrying issue. Since the speaker was making sounds with the amp
off, one guess would be with a power supply.

Sal

[cma29]

^^^
Wow, Sal You know your stuff. Nice advice.

[Soundserge]

Most definitely. Thanks, Sal. I'm waiting to speak with Jeff Rowland and am getting ready to ship the speaker to Dynaudio.