Help! La Scala industrial woofer

[dondrummond]

I recently bought a pair of 1980 La Scala industrial speakers. One of the woofers is barely making any sound. I opened up the cabinet and tested the K43 with a multimeter and got a reading of 4 ohms, and can’t see damage to the speaker. The working woofer also reads 4 ohms, and both horns can drive the working speaker. Should I just replace the woofer or is there something else I can try first to troubleshoot the woofer in question? I didn’t get to try out the speakers before buying but the previous owner confirmed they were working.

 

Thanks for your advice and help with troubleshooting! 

[parlophone1]

Have you tried if the connections and cables to the woofer are working as they should?

[CWOReilly]

My LSI both had loose connections at crossover. I’d start there. 

[Peter P.]

Put the suspect woofer in the working cabinet. If it works, there's a fault in the crossover.

 

You could also try putting a voltmeter across the woofer terminals and setting the meter to AC volts.

You could just connect to the woofer outputs on the crossover which is easier to access, but that won't

tell you whether the signal is reaching the woofer's terminals.

 

Play some music and as you turn up the volume, the number should go higher. Of course, the number

will bounce around with the music; bonus if your voltmeter has a "Max Hold" feature. You can then

compare with the working speaker.

 

[dondrummond]

3 hours ago, parlophone1 said:

Have you tried if the connections and cables to the woofer are working as they should?

Thank you! I’ve tried running a speaker cable from the crossover directly to the woofer with the same result. Resistance reads 4 ohms both at the woofer and the binding posts that receive the input from the crossover. Does this rule out connections or cables?

[82 Cornwalls]

Have you tried from amplifier directly to the woofer bypassing the crossover?

[Bacek]

If you gently press membrane with full hand there is any resistance/difference to googspeaker?

[dondrummond]

2 hours ago, Peter P. said:

Put the suspect woofer in the working cabinet. If it works, there's a fault in the crossover.

 

You could also try putting a voltmeter across the woofer terminals and setting the meter to AC volts.

You could just connect to the woofer outputs on the crossover which is easier to access, but that won't

tell you whether the signal is reaching the woofer's terminals.

 

Play some music and as you turn up the volume, the number should go higher. Of course, the number

will bounce around with the music; bonus if your voltmeter has a "Max Hold" feature. You can then

compare with the working speaker.

 

Thank you Peter! My version has the horn+crossover combo separated from the woofer. I’ve run a cable directly from either of the LF post at the crossover to the bad woofer and with either crossover the result is a faint LF output from the speaker. When I connect either crossover to the working woofer speaker, the result is a good LF output. Does this exclude the crossover being the problem? I mentioned earlier that since I have the cabinet open, I’m  attaching a cable directly from the LF output post at the crossover to the connection at the broken speaker, to try and rule out the original speaker connection/wire as the source of the problem. 

[Peter P.]

If you place your hand on the backside of each woofer for comparison, I presume the suspect

woofer feels like there is less excursion, yes?

 

If you've connected to the suspect woofer using the same speaker wire using each crossover,

you certainly wouldn't have to remove the crossover, just make the wires long enough. Sounds

like that's what you did, and it's a convenient and valid test.

 

As you increase the volume, does the suspect woofer move more? Have you removed the

suspect woofer from the cabinet to see if something is limiting cone travel from the front

side of the woofer, which you typically can't see?

[dondrummond]

On 11/14/2024 at 8:28 PM, Peter P. said:

If you place your hand on the backside of each woofer for comparison, I presume the suspect

woofer feels like there is less excursion, yes?

 

If you've connected to the suspect woofer using the same speaker wire using each crossover,

you certainly wouldn't have to remove the crossover, just make the wires long enough. Sounds

like that's what you did, and it's a convenient and valid test.

 

As you increase the volume, does the suspect woofer move more? Have you removed the

suspect woofer from the cabinet to see if something is limiting cone travel from the front

side of the woofer, which you typically can't see?

Correct, good speaker excursions are greater than the bad one. The cone on the bad speaker barely moves when pushed. The voltage readings while playing are similar on the good and bad speaker. 

another community member suggested a faulty voice coil. This is probably the issue since it’s not connections/cables, crossover/ or tears in the cone. I’ll go ahead and replace the failing speaker, or should I replace both? 

 

Thanks for the great support with troubleshooting. This is the first time I’ve closely looked at a speaker.

[dondrummond]

On 11/14/2024 at 8:37 AM, Bacek said:

If you gently press membrane with full hand there is any resistance/difference to googspeaker?

I didn’t unscrew the other speaker, but the broken speaker barely moves if I push on it. 

Edited November 16, 2024 by dondrummond

[dondrummond]

On 11/14/2024 at 8:01 AM, opnly bafld said:

Have you tried from amplifier directly to the woofer bypassing the crossover?

Didn’t make a difference, broken speaker sounded the same. 

[geoff.]

Hi @dondrummond, I have a pair of LSIs that had a similar issue with one woofer and I wound up finding a replacement on eBay. Shipping was a killer for me, but if you’re in the states you shouldn’t get zinged too hard.

 

I am in the habit of hitting all the drivers with an ohmmeter when I get a pair of used speakers home and found the woofer to be reading a little high so I took it out of the doghouse to have a better look. The basket was a little hung up when I pressed on it and finally settled on a reading of over 22 ohms so it got recycled. 
 

 

 

 

[82 Cornwalls]

The Speaker Exchange can get new ones.

[Peter P.]

I would expect the supposedly faulty speaker to measure a different resistance if the voice coil was bad as

that's what the voltmeter is measuring; the wires of the voice coil.

 

Does the cone of the faulty speaker move as freely as the good speaker? Perhaps it's a friction issue.

 

If you choose to replace the speaker,  save the old one to dissect later to see what the fault is.

 

Or, you may be able to send it to a place like Simply Speakers and get it repaired. Go this route and

you'll end up with two matching woofers.

[CWOReilly]

3 hours ago, dondrummond said:

Didn’t make a difference, broken speaker sounded the same. 

Open the cabinet, remove and test. It could still be a connection. 

[dondrummond]

2 hours ago, Peter P. said:

I would expect the supposedly faulty speaker to measure a different resistance if the voice coil was bad as

that's what the voltmeter is measuring; the wires of the voice coil.

 

Does the cone of the faulty speaker move as freely as the good speaker? Perhaps it's a friction issue.

 

If you choose to replace the speaker,  save the old one to dissect later to see what the fault is.

 

Or, you may be able to send it to a place like Simply Speakers and get it repaired. Go this route and

you'll end up with two matching woofers.

Resistance is exactly the same, right at 4 ohm. Cone of the faulty speaker does not move easily when pushed by hand. What’s the solution if friction is the issue? 

[dondrummond]

1 hour ago, CWOReilly said:

Open the cabinet, remove and test. It could still be a connection. 

It’s not the connection, or the crossover. I’ve tried connecting the speaker directly to either crossover, and then directly to the amp, ending up with the same result from the broken speaker.

[CWOReilly]

2 hours ago, dondrummond said:

It’s not the connection, or the crossover. I’ve tried connecting the speaker directly to either crossover, and then directly to the amp, ending up with the same result from the broken speaker.

But have you taken it out of the cabinet?

[Peter P.]

On 11/16/2024 at 6:01 PM, dondrummond said:

 What’s the solution if friction is the issue? 

An experienced firm like Simply Speakers (there are others) can remove the cone and dustcap and possibly find something stuck in the gap

where the voicecoil is. They may have to replace the cone and dust cap as a result, but it might be easier and cheaper than trying to source a replacement

woofer.