One Woofy Tower After Reconing Sub

[jabrookbank]

I have a pair of decent, late 70's Sony towers. A 10" sub, a mid and a tweeter. One of the speakers just resonates bass to the point that it's visibly shaking that subwoofer, even at low volumes. I've switched the wiring left to right, so I know it's not the channel of the amp and have switched out amps and turntables so it is definitely the speaker itself. I've opened it up to check if wiring was loose and made sure all the speakers were screwed in tightly. So right now my only recourse is knock off a couple db's off the low end via a graphic EQ. Any idea why with two identical speakers with newly coned speakers would react so differently? I can put my hands on top of each tower and feel a drastic difference in the vibration the trouble speaker puts out. I should also say that I've moved the offending speaker away from the turntable/receiver and the speaker "farts" in the same way so it has nothing to do with resonance as the good speaker is fine even at high volumes when on the floor a foot away from my setup.

 

[mikeybc]

Try measuring the DC resistance of the woofers voice coils with an ohmeter. Possible short within the coil itself...and the amp isn't liking it.

 

[jabrookbank]

Try measuring the DC resistance of the woofers voice coils with an ohmeter. Possible short within the coil itself...and the amp isn't liking it.

Thanks so much for the reply. I don't own an ohmeter so maybe I'll track one down. Could probably be useful down the line. But a short in the coil: would that require soldering or just replacing the speaker?

 

[CoogarXR]

Were they reconed or just refoamed? Did you do the work, or have it done?

I just wonder if the spider is detached or something, that would make a woofer quite "loose".

 

[jabrookbank]

Were they reconed or just refoamed? Did you do the work, or have it done?

I just wonder if the spider is detached or something, that would make a woofer quite "loose".

The woofers were dry rotted when I got them so I took it to a place that fixed my JBL 2600 bookshelf speakers' woofers when they tore. Not sure if that means they were reconed AND refoamed or not. May be able to look into the terminology/email exchanged with the shop who did the work and get a clearer idea. Also, worth mentioning that it has been almost a year since the work was done and the problem was noticeable at some point but has gotten much worse.

 

[jabrookbank]

And I guess they would have to have been refoamed if the cone was completely replaced?

 

[CoogarXR]

Yeah, if the cone was replaced, then it was reconed. Many times in a recone job, the whole motor assembly is replaced (cone, surround, spider, voice coil). I just wonder if the spider has come loose. I would take the woofer out, look under the cone at the (usually yellow) spider. Gently push the cone out and see if the spider lifts off the basket.

 

[jabrookbank]

Ok! Will do that when I get home. But if it has come loose, it needs replacing or repair via soldering or something?

 

[mikeybc]

If it's just unglued from the basket it can be reglued, though re-centering the voice coil (preferrably with shims) will be required. Also the outer edge of the surround may need to be separated from the basket first if the coil was off a little bit the first time it was glued on.

 

[jabrookbank]

Ay yi yi. Looks like this is all above my current understanding but nothing a little googling and youtubing can't fix if I am able to pinpoint something specific to tackle. I will report back if there is anything of note on another visual inspection. Wasn't crazy about paying $90 for reconing the pair because even getting the Sony's for free, they are doubt they are worth more than $30-40 in working condition. So doubt I will shell out any more money on them anytime soon. Thanks so much for your time. Hopefully I'll put some of this info to good use in troubleshooting this thing and have some stuff to share for any other noobs with this same problem.

 

[donprice]

Also, worth mentioning that it has been almost a year since the work was done and the problem was noticeable at some point but has gotten much worse.

If it is a loose spider, you could take it back to the shop and ask them to reglue it since it sounds like it may not have been quite right to begin with.

 

[jabrookbank]

Took it back to the shop that has done all of my reconing. I am blanking on the term he used (it was something like "flashing" the speaker) but it was more than just checking that the ohms were reading in the correct range. He said something along the lines of that he tested the whole frequency spectrum by running a tone through it (I'd like to actually know that term though). He said it was 100% functional and he's an old school guy with a nice shop, spent some time talking with me about it so I am very comfortable taking his word. He said since it was a 3 way speaker tower it should have a crossover that could have something that has come loose in it.

So took it home and the final troubleshooting test I did was swapping the woofers. I was swapping wiring/channels (L to R) and placement of the physical speakers and the "good" woofer did the same thing. Used Radiohead's "King of Limbs" for the louder modern mastering and that clear sub-bass and it seemed to handle the intro's bass of the drum loop but once the synth bass came in the tweeter and mid speaker were coming through clear but the sub from the other speaker that I put in did the same thing. Just crazy vibration. Doesn't have that flapping buzz of a torn speaker, just a rattling that beyond a normal loose casing sound that I've heard in guitar cabs. I'm attaching a picture of the innards that shows the wiring from the connector on the back of the speaker as it connects to the other two speakers and the loose wires that go to the sub. I have very little familiarity of the terminology or identifying the workings of any electronics really, but does there look to be a crossover in this picture?

IMG_1384

• jabrookbank
• Apr 14, 2016

sony wiring

IMG_1372

• jabrookbank
• Apr 14, 2016

sony front

IMG_1371

• jabrookbank
• Apr 14, 2016

sony tag