15" speaker?

[Bluefinger]

Hi,

I hope this is the correct forum section.

I currently have two 15" speakers that I can use in my 5e5a based tweed amp. I like the overall tone of these but they both have a certain unpleasant buzz in the upper frequencies. If I connect other speakers to that amp (1x12, 2x10) it's not there and if I connect these speakers to other amps I get the same buzz so it's definitely coming from the speakers. One is a Weber 15A150 and the other one a '62 Chicago Jensen C15N, reconed by Weber.

So what I would like to know ... is that a common quality of 15 inchers or just a Weber thing (both have the same Weber cone). Usually I buy Webers for their smooth top end but I wopnder if there are other alternatives that you all can recommend. I am definitely going for a Jensen type of tone, not british.

thanks!

[soundguruman]

I would try to make the bias hotter. It may not be the speakers at all.
But if you want serious bass speakers use EVM 15B.
The surround of the speaker (the outer cone, near the frame) can be treated with damping compound, which dries...
This stiffens the compliance of the speaker and stops the buzz.
Any JBL speaker repair center (or speaker shop) can apply this to the speaker and test it again.

[Bluefinger]

Thanks,

it is the speaker ... as I mentioned above I swapped amps and speakers and the buzz is always stays with the speakers, not with the amp.

I'll check if there is somebody in my area who does this kind of repairs ... thanks!

[soundguruman]

Thanks,

it is the speaker ... as I mentioned above I swapped amps and speakers and the buzz is always stays with the speakers, not with the amp.

I'll check if there is somebody in my area who does this kind of repairs ... thanks!

If you do buy new ones, and you want bottom for days, start with a speaker that has a cast frame.
Speakers with stamped metal frames just don't cut it for low frequencies.
You will also find cast frames are quite expensive. They last...quite a bit better.

[olddawg]

If either of those speakers have a metal dust cover, make sure it isn't loose and rattling.

[Tom Phillips]

...what I would like to know ... is that a common quality of 15 inchers or just a Weber thing...

Since this question from your original post has not been answered I’ll say NO to the first question and “probably not” to the second.
You provided good information to indicate that you isolated the problem to the speakers. However, I’m still wondering if it could be something to do with the combination with your cabinet.

I troubleshoot this kind of problem by driving the amp with a sine wave and sweeping the frequency until the buzzing sound is heard continuously. Then I press on various places on the speaker and the cabinet to try to determine exactly where the buzz is originating. One trick is to lightly push around the speaker spider with a finger. If I find a spot that affects the buzz then I know that there is a problem with the voice coil. It is either rubbing, has a loose turn, some contamination in the gap etc.

This same technique can be used with the speaker out of the cabinet. That will allow you to additionally investigate dust cap issues as suggested by Olddawg.

If you don’t have a sine wave generator maybe you can find someone who does or have a buddy use a guitar to play a pure note that emphasizes the problem. One you know a little more we can go from there.

Regards,
Tom

[olddawg]

There are a bunch of signal generator aps available for free online. I have one in my iPhone. You can dial individual frequencies and wave functions and set it to sweep. All for free.

[Tom Phillips]

There are a bunch of signal generator aps available for free online. I have one in my iPhone. You can dial individual frequencies and wave functions and set it to sweep. All for free.

That's good information.
However, I really like having my hand on an analog dial to tune the frequency.
Tom

[deci belle]

Hi Bluefinger, both my JBL d130 and 140 15" speakers are doing this too. I need to do what Tom has suggested.

[Tom Phillips]

Hi Bluefinger, both my JBL d130 and 140 15" speakers are doing this too. I need to do what Tom has suggested.

Interesting. Do your JBLs still have the original cones?

Here is an interesting story.
I was troubleshooting a D120F that had a bad raspy buzz at all mid and low frequencies. It sounded just like a rubbing voice coil and I thought that a recone would be needed for sure. When I got the speaker out of the cabinet I noticed a very tiny metal shaving that was being held against the aluminum dome by the speaker’s magnetic field. As the speaker cone vibrated that sliver would bounce around on the dome and make a huge noise. I removed the sliver and the speaker sounded fine. I’m not suggesting that you have the same problem but this is a good thing to know about.

Regards,
Tom

[deci belle]

Yes, Tom. Thank you for the story! Both of mine are very clean and seem to be original. The magnet covers are both tight, too. Your suggestion is something I'll just have to tackle because it's driving me crazy!!

[J M Fahey]

Pull the suspect speaker and put it over the cabinet or with somewhat longer leads over the table and play all notes from end to end of your fingerboard, until you clearly hear the buzz.
Although a guitar does not provide a *continuous* sweep, by definition, you can fine tune when close by plucking a lower note and bending it up, if necessary.
Post results.

[deci belle]

OK, Juan! Thank you!!

[olddawg]

That's good information.
However, I really like having my hand on an analog dial to tune the frequency.
Tom

Yeah, I know what you mean. I have an at least 50 year old tube HP signal generator with a huge aluminum dial on it. There is something in turning that big old dial. It is, however, a bitch to put in your pocket!

[Bruce / Mission Amps]

If you determine it is just a bad pair of speakers, I'd send them to Orange County for speaker reconing. I don't think I've ever had one come back from them over the last 10 years that wasn't near perfect.... I can't NOT say that about a couple other speaker reconers.