One Blackback louder than others in a 4X12

[Mxzx]

I have a '70's slant cab with 25w Blackbacks. They all appear to be the same, although one or two may be re-coned. Wiring is correct.

When I play it, the top right speaker sounds louder than the rest. I also noticed that I have 25ohms at the speaker jack, 12ohms across each speaker. Does that number seem correct?

Any ideas what might be going on?

Thanks

[Lefty Lou]

I have a '70's slant cab with 25w Blackbacks. They all appear to be the same, although one or two may be re-coned. Wiring is correct.

When I play it, the top right speaker sounds louder than the rest. I also noticed that I have 25ohms at the speaker jack, 12ohms across each speaker. Does that number seem correct?

Any ideas what might be going on?

Thanks

Sounds like you're only measuring only one side of your 4 x 12" speakers which are in series (in your case, 12 Ohms + 12 Ohms = 24 to 25 Ohms). Typically english brand speakers like Celestion read around 15 Ohms. If you're up to it, you could remove the back cover to make sure that your (4) speakers are wired Series/Parallel as they should be like this:



Also, if one or more of your speakers are out of phase with one another, that could cause what you're hearing. You know how to test your speakers for (phase/polarity) right? Do your individual speaker polarity test first. Then, say you should find that one speaker's cone moves inwards, while the other three speakers move outwards, you will at this point need to swap speaker terminal connections on the "inward moving" speaker. Again you want all (4) speaker cones to travel either outward or inward at the same time. After you've addressed this issue, then double check your overall cabinet wiring. If as you say, one or two speakers have been re-coned there is the extreme possibility that you have as many as (2) speakers that may be out of phase with the other pair of 12" speakers.

[youtube]http://www.youtube.com/watch?v=xIMHGkxw72o[/youtube]

[Mxzx]

I checked the wiring and its correct.

I'll def test the polarity though. Thanks for the info.

[Scumback Speakers]

If one of your speakers was an 8 ohm it would draw twice as much power as the 16 ohm it's wired with. That would explain why it's louder. But you'll have to unsolder/disconnect that speaker to test it individually with a multimeter to find out for sure.

[Mxzx]

Well I checked them all out. They all tested correctly for polarity and ohmed at 12-13, except the lower left. No movement on polarity test and open circuit on the meter. Would that explain some things?

Next question, what to do with the speaker? Can it be repaired?

Thanks

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[Lefty Lou]

Well I checked them all out. They all tested correctly for polarity and ohmed at 12-13, except the lower left. No movement on polarity test and open circuit on the meter. Would that explain some things?

Next question, what to do with the speaker? Can it be repaired?

Thanks

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If you can find a speaker repair facility locally that can take a look at it and see if it can be repaired with destroying the original cone, that would be your best bet. I'm guessing it's your voice coil. If you don't have anything locally, Jim @ Scumback would probably say that Weber has the right replacement cone kits if he doesn't have them (that is if it were necessary to recone) also, there is Bill @ Great Plains Audio in Oklahoma City where I live that does excellent speaker work as well.

[Mxzx]

Thanks for the info, does that one look like it was re-coned previously? It does have the 1777 code on cone.

[Lefty Lou]

Thanks for the info, does that one look like it was re-coned previously? It does have the 1777 code on cone.

Not that I can see or tell Mxzx, looks like the original cone (or an original cone replacement). Most likely you or the previous owner used a 100 watt head with the cabinet, and being that the speakers have nominal power handling, that speaker was the weakest link. If that was the case, it's a wonder that more of your black back 12"s weren't taken out as well. Another thing that's bad for (amps/speakers) are large square waves (ala fuzz face pedals) hitting the front end of the amp, so one has got to be careful of how hard they drive their amps with these pedal effects.

You'll have to check with a speaker re-coner to see if they can (remove/replace) the cone w/o damage and to replace the voice coil with the accurate replacement voice coil, as this seems to be your problem that you incurred with the open circuit reading.

[Scumback Speakers]

That speaker cone looks like it's an original judging by the pics. Sounds like you have a bad coil, or connection to the speaker. I would recommend sending that to Orange County Speaker Repair, or I could do it. It uses a cone that Weber doesn't offer for recones, based on my experience. OCSR or I do have it in stock.

Good luck with whatever you decide to do.

[Lefty Lou]

That speaker cone looks like it's an original judging by the pics. Sounds like you have a bad coil, or connection to the speaker. I would recommend sending that to Orange County Speaker Repair, or I could do it. It uses a cone that Weber doesn't offer for recones, based on my experience. OCSR or I do have it in stock.

Good luck with whatever you decide to do.

Thanks for chiming in Jim since you're the resident speaker guru, and a walking history of Pre-Rola, Rola, and Celestion speakers. If I were much better off financially, I'd sure be ordering your speakers w/o a doubt.

[Mxzx]

Thanks for all the info.

Jim, do you know what it would cost to fix it if you did it?

Thanks

[Scumback Speakers]

Assuming the frame has no issues, $99 and shipping. Typical turnaround on a recone is 2-3 days plus shipping.

[Lefty Lou]

Assuming the frame has no issues, $99 and shipping. Typical turnaround on a recone is 2-3 days plus shipping.

With todays prices being what they are, I'd say that's one heck of a deal Mxzx.

[Mxzx]

I'll be sending it off, Jim. Thanks!

Can you send me a pm with details of shipping, payment, etc?

Thanks

[Scumback Speakers]

PM sent. Prefer to handle this via email from here though. Email is in the PM.

Jim