Speakers without Crossover

[Chippy476]

Hi all
I’m investigating local Pubs PA system (very basic) as it switched off last night after about 3hrs use. Moderate levels on a Open Mic night. Acoustic guitars and mics.

Thermal overload indicator in mixer/amp didn’t come on (StudioMaster PowerPack400) but it was running warm.

i suspect the speakers as I’ve had them on the bench this morning and the consist of a Eminence 10” (EM10-2008) and some unbranded horn tweeters. (Didn’t sound too bad when working!) …. but NO crossover what so ever. No inductors, no Capacitors, just a 33ohm 5W resistor inline with tweeter.

Any idea if this might the the issue?

Have checked all connections and cables… have also checked mixer fan and working fine.

Thanks

 

[TLS Guy]

Hi all
I’m investigating local Pubs PA system (very basic) as it switched off last night after about 3hrs use. Moderate levels on a Open Mic night. Acoustic guitars and mics.

Thermal overload indicator in mixer/amp didn’t come on (StudioMaster PowerPack400) but it was running warm.

i suspect the speakers as I’ve had them on the bench this morning and the consist of a Eminence 10” (EM10-2008) and some unbranded horn tweeters. (Didn’t sound too bad when working!) …. but NO crossover what so ever. No inductors, no Capacitors, just a 33ohm 5W resistor inline with tweeter.

Any idea if this might the the issue?

Have checked all connections and cables… have also checked mixer fan and working fine.

Thanks

The speaker not having a crossover is not the problem. The 10" is run full range, and the tweeter is a piezo tweeter, which are very high impedance. So the impedance the amp sees, will be entirely from the 10" woofer. The 33 ohm resistor is a padding resistor to reduce tweeter output. This is a common arrangement in cheaper commercial speakers.

So you need to look to the wiring. May be it is in wall and eaten by mice. That happens. So check the wiring when disconnected from the speaker with a meter.

Also check the DC resistances of the woofers. It is possible that the speakers have been over driven, and the 10" woofers have shorted turns, lowering the impedance.

The DC resistance should be about and I say about 1.5 less than the specked impedance of the speaker. If the speakers and wiring check out, then the amp is failing.

 

[highfigh]

Hi all
I’m investigating local Pubs PA system (very basic) as it switched off last night after about 3hrs use. Moderate levels on a Open Mic night. Acoustic guitars and mics.

Thermal overload indicator in mixer/amp didn’t come on (StudioMaster PowerPack400) but it was running warm.

i suspect the speakers as I’ve had them on the bench this morning and the consist of a Eminence 10” (EM10-2008) and some unbranded horn tweeters. (Didn’t sound too bad when working!) …. but NO crossover what so ever. No inductors, no Capacitors, just a 33ohm 5W resistor inline with tweeter.

Any idea if this might the the issue?

Have checked all connections and cables… have also checked mixer fan and working fine.

Thanks

What is covered by the electrical tape in the first photo? My curiosity would tell me to remove the tape and look at it. Since it's inline with the resistor, it doesn't really raise suspicion, but I would want to know what it is and why it was covered.

How were the controls set? If someone was trying to get more bass out of the system, that could have caused the amp to become too hot. Did the amplifier work normally after being allowed to cool?

You showed everything except the speaker cables- is there a chance that someone has repaired one or both, or added extensions? You need to check those, too.

 

[Chippy476]

Hi both
Checked speaker cables and terminations, all good.
Tape is just covering the solder joint of resistor.

Mixer Amp has Thermal error LED, which didn’t come on, but unit was warm (not too hot to touch). Initial thoughts were fan, but that is fine. Spins on power up and then comes on when on load. Have found. Schematics and it appears to be a variable speed fan circuit depending on heat. Works ok now in the garage, but have seen that the right channel is slightly lower volume than the left (have swapped sources around and it stays lower on right)

It was towards end of the night when it died, so volume might have crept up. No Base through mix (base guitarist had own amp), just vocals and acoustic guitar. Plus the heat LED didn’t come on.

Bit concerned to just hand it back as ‘tested’ as not found a fault as yet…

Mixer was a new purchase by pub from eBay, so wonder if sold due to fault…

 

[TLS Guy]

Hi both
Checked speaker cables and terminations, all good.
Tape is just covering the solder joint of resistor.

Mixer Amp has Thermal error LED, which didn’t come on, but unit was warm (not too hot to touch). Initial thoughts were fan, but that is fine. Spins on power up and then comes on when on load. Have found. Schematics and it appears to be a variable speed fan circuit depending on heat. Works ok now in the garage, but have seen that the right channel is slightly lower volume than the left (have swapped sources around and it stays lower on right)

It was towards end of the night when it died, so volume might have crept up. No Base through mix (base guitarist had own amp), just vocals and acoustic guitar. Plus the heat LED didn’t come on.

Bit concerned to just hand it back as ‘tested’ as not found a fault as yet…

Mixer was a new purchase by pub from eBay, so wonder if sold due to fault…

It seems to me that system is likely not up to the job. That whole system does not seem suitable to run guitars and vocals in that type of environment.

It may not be handing the bass guitar, but leads take lots of power. What is that mixer amp, and what are its specs? Those 10" speakers are 75 watt inexpensive drivers

Did you check the DC resistances of he voice coils of those drivers? Before a driver like that fails completely, the VC drops resistance due to heating and the output drops. This certainly can take down amps. I would be interested to know the DC resistance of both those 10" drivers.

My strong hunch is that this system is nowhere near up to the job.

 

[highfigh]

Hi both
Checked speaker cables and terminations, all good.
Tape is just covering the solder joint of resistor.

Mixer Amp has Thermal error LED, which didn’t come on, but unit was warm (not too hot to touch). Initial thoughts were fan, but that is fine. Spins on power up and then comes on when on load. Have found. Schematics and it appears to be a variable speed fan circuit depending on heat. Works ok now in the garage, but have seen that the right channel is slightly lower volume than the left (have swapped sources around and it stays lower on right)

It was towards end of the night when it died, so volume might have crept up. No Base through mix (base guitarist had own amp), just vocals and acoustic guitar. Plus the heat LED didn’t come on.

Bit concerned to just hand it back as ‘tested’ as not found a fault as yet…

Mixer was a new purchase by pub from eBay, so wonder if sold due to fault…

Switch the speakers- if the problem moves to the other channel, it's that speaker which has the problem.

 

[highfigh]

It seems to me that system is likely not up to the job. That whole system does not seem suitable to run guitars and vocals in that type of environment.

It may not be handing the bass guitar, but leads take lots of power. What is that mixer amp, and what are its specs? Those 10" speakers are 75 watt inexpensive drivers

Did you check the DC resistances of he voice coils of those drivers? Before a driver like that fails completely, the VC drops resistance due to heating and the output drops. This certainly can take down amps. I would be interested to know the DC resistance of both those 10" drivers.

My strong hunch is that this system is nowhere near up to the job.

There is absolutely no reason to run the bass guitar through that PA, in a pub.

If a conductor becomes warm or hot, its resistance increases- you know that. It could be a shorted voice coil, though. That could easily cause the amp to puke.

[/QUOTE]

 

[highfigh]

Eminence 10” EM10-2008

That's the date code, not the driver's model number. Post a photo of the whole label, so we can read the right side of it-

Use the link to contact Eminence if you need to find a replacement- while it's unlikely that you'll find the same driver, they have the parameters for all of their drivers (not too old, though) and can advise on something that would be close enough for this application.

Eminence Speaker

Eminence Speaker is America's premier manufacturer of guitar speakers, bass speakers, and professional audio loudspeakers since 1966.

eminence.com