Speaker Testing

matzingerz

matzingerz

Dec 26, 2018
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4,551
Germany
#1
Hey TB,

I have a cab sitting in our rehearsal room that a guy told me it should work, but it had an XLR input and 2 of the 3 pins were bypassed on the inside so it really had only 2. because normal mic XLR cables aren't meant for that purpose e.g. beeing used from amp to cab, (and it also did not produce any sound at all) I soldered a 1/4" input jack on the 2 wires from the speakers.
(I already build some pedals and stuff so I can solder properly and know where ground and the signals comes).
When I finally connected an amp that was expecting a 4ohm load (the speaker is a 215 cab and they a wired paralell and the multimeter reads also 3,8Ohms, so everything fine I guess. It also says 8Ohm on the back panels of the speakers) but when I played something, the top speaker was really fuzzy, almost like if I had a pedal in between. (actually sounded not that bad tbh lol) but I want clean sound first. The bottom speaker did not produce any sound at all.

My next step is removing the metal grill by removing tons of screws and removing both speakers. Measuring them both and testing them individually. Probably resolder both connections, even though they look pretty clean and read the right resistance.

Can you give me some advice, what else I can check before buying new speakers?

Thanks in advance
 
#2
Yes, verify EVERYTHING first.

Verify the DC resistance of each driver and from that you can make a reasonable assumption of each driver's nominal impedance.

Verify that each driver is functional (at low volume) on its own, and in not distorted. Do you know the brand and model of the drivers?

Verify that there is no damage to the wiring. If there's no tweeter, insure that there are no crossover parts lurking and still connected.

Measure the resistance of the wiring with no drivers connected to be sure there are no short circuits.

Then carefully reassemble and test in the cabinet.
 
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#3
First thought: you're thinking of investing in new speakers to repair an old 'that-should-work' cab in your rehearsal room? Por que?

Setting that aside, what you're planning--to remove and test the speakers individually--is the right path. It sounds like the top one is already history. The bottom one probably is too, but the resistance measurements point to the voice coils still being intact in both drivers. It makes sense that the top one is, as you can hear it working, however badly, but if the voice coil is still intact on the bottom one, why doesn't it make noise? After you get them out of the box, push in gently on the cone of the suspect driver and see if it moves and if it rubs in the gap. After that, there's not much you can do if it doesn't make noise, other than replacement.

What kind of cab is it? Did the XLR input look to be original equipment? Was is a standard, 3-pin XLR, or was it a 4-pin? Your description of 2 of the 3 pins not being used kind of leaves one wondering how the circuit was intended to be completed...on the shell? Not that it matters if you've already removed it from the circuit.
 
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#4
Thank you for your fast answers,
agedhorse said:
Do you know the brand and model of the drivers?
Click to expand...
Redbrangus said:
Did the XLR input look to be original equipment? Was is a standard, 3-pin XLR, or was it a 4-pin?
Click to expand...
So I already contacted the german manufacturer SOLTON.
The cab is all original, it is a 3 Pin xlr female input and 2 pins are bypassed. The Cab is from 1984 so no Neutrik cables then I guess and they tried somewhat of an improvement with the XLR beeing more secure in termns of not to just fall out due to loose input connctions vs low frequency vibrations or something.
The Impedance on the outside says 4 ohms and rated 400W. Its and 215 so no tweeter or what so ever, only 2 15 inch drivers wired in prallel.
Redbrangus said:
First thought: you're thinking of investing in new speakers to repair an old 'that-should-work' cab in your rehearsal room? Por que?
Click to expand...
I was looking for an 4Ohm 215 cab for my Svt 2 pro, and the guy I bought it off from (very long story) ensured me with a couple other guys at the rehearsal room building that he had tested it a month ago and everything worked, but they had the cable from the drummer in the basement who wasn't anrount when I was there, and normal xlr cables did not work.
And even if its broken 40€ would be okay for an empty cab on wheels I guess.
But anyway, I want to be sure weather it is broken or not, so I contacted SOLTON and they said, they don't ahve much Information left about this cab other than the Drivers were called E15 and rated 300W RMS 8Ohm, which is what I could also read on pictures i sent them with the drivers and the back panel.(Don't ask me why it says 400W on the backpanel then).

The speaker cones btw look in almost perfect condition other than bit of dust, but much less dust than on my usa svt810e speaker cones, which work perfectly.
 
#5
As you say, if the cab is solid and in good shape, it's probably worth that sort of money. I'm dubious of a 300-watt RMS rating on old Solton drivers.

A SpeakOn will fit in the cutout for a female, panel mount XLR without further modification, if that's what's there.
 
#7
Sounds like its not worth the risk, even for free. What model is the cab?

2 (good) 15" speakers wont be cheap. and they wont sound good if not designed for the cabinet they are installed in.

EDIT: Ah. bass cab from 1984. Hard pass for me. Bass wasn't bassey enough back then. IMO.
 
#8
200 watts RMS may in fact be a reasonable rating for the speaker based on reliability factors.
 
#9
agedhorse said:
Yes, verify EVERYTHING first.
Click to expand...

Hey im back with new information.
So yesterday I unmounted the speakers and measured both resitances, they were both 6,2 Ohm so that seemed to be correct. Then I tested both with a 9V battery if they react and to determine where I should solder the input and the ground onto the 1/4" input. And both made that "whomp" and went either inside or outside. Ofc I only connected the battery for a second or so to not overheat or damage something... but well, when I connected an amp to the speakers, one of them still gave no sound at all, and the other one farted just like before.

Redbrangus said:
After you get them out of the box, push in gently on the cone of the suspect driver and see if it moves and if it rubs in the gap. After that, there's not much you can do if it doesn't make noise, other than replacement.
Click to expand...

What exactly do you mean by the driver rubbing the gap?

I even resoldered the connections on the speakers to check if that was the problem. Is there more testing to do without further knowledge of disassambling and reassambling a driver?
 
#10
Have you tested the speakers with a different amp and speaker cable?

Something isn't right here.
 
#13
matzingerz said:
I used this as an input? Can this be the problem? But why would both divers react differently then?
Click to expand...
Nothing wrong with that. I'm a little shocked that it sells for 4.09 Euros, but that's a standard American 1/4" input jack. I'm sure you're aware that the mounting shaft/nut arrangement is 'hot', in that it is carrying signal, just as the back shell in the male connector does. Just mentioning that...your symptoms don't indicate a short at that point.
matzingerz said:
Then I tested both with a 9V battery if they react and to determine where I should solder the input and the ground onto the 1/4" input. And both made that "whomp" and went either inside or outside.
Click to expand...
This tends to indicate that both drivers are (or were) working, so they are not the problem. But something isn't adding up...are there any other components in the signal path, like old, unused crossover components?

I suppose swapping the physical positions of the two drivers would indicate if the problem is the actual driver itself.

Another highly speculative hypothesis: you mention soldering...is it possible you've disturbed the small tensile-wires that connect the terminals to the voice coil?
 
#14
Ok so to get more detailed, I just removed the top speaker, which was wired in parallel to to bottom one, had to unscrew the driver and unsolder the connection. Then i conencted the hot and the ground to the input jack of the bottom one, since it still was connected to the wire, and measured 6,2Ohm and it passed the battery test. But no signal from amp.
After that I soldered the same cable, as there was on it before, on the top speaker outside of the cabinet, on the driver again and measured 6,2Ohms and it also passed the battery test, nut only fuzzy notes from the amp.

So I did not remove the bottom driver yet since I thought if it gives the proper resistance and the battery test works and it looks fine, it won't be the cable, but I did not try other copper cables yet.
Also on the top driver which i removed, I only used the wire that was soldered on it before.
So I guess I shall check with other wires?
 
#17
if not mentioned yet you should check polarity of the drivers.

both cones should move outward or inward. when you apply DC

something as simple as the 9 volt battery test. any polarity doesnt matter.
but both drivers should move inward or outward to confirm they are not out of phase
 
#18
There was a time when XLR were fashionable for speakers. AIUI they were better than jacks and cheaper than other alternatives but it was still a dumb idea.

You need to go through this stuff steadily step by step when something weird is happening. You've checked voice coils and resistance. You need not to be rushed, have quiet and not have other people about so rehearsal venue probably a bad idea.

Next is to check that voice coil is not touching the magnet. The clearance is v small so this can happen. Do what Redbrangus described, push each cone v gently and only 1mm and listen for rubbing sounds and uneven movement. You'll need a very quiet room and be very gentle. I would get both drivers out of the box for this. And take them somewhere quiet.

Solder a pair of new wires onto the back of each speaker. Lightish two core mains out of the outer casing is fine. Do the battery test on end of the new cables, make sure both move the same way and check resistance again just in case.

At this stage i would just try feeding music into them from say headphone socket of mobile phone or something. Won't be loud, but it will be very audible. If you've still got silence from one and distortion from the other they are probably beyond help from folks like you and me and need professional repair or chucking in the bin.
 
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