DIY woofer dead?

[trnqk7]

I was hoping that perhaps someone could be of some help-I have a pair do DIY speakers made from parts ordered from the Madisound website a few years ago (maybe 7 or 10 yrs). The woofers in the speakers are a the old Madisound Sledgehammer woofers DVC 8 ohm(10" size) I am 99% sure. My question is this-one of them seems to have quit working. The woofer in the left speaker is going like crazy, but the one on the right does nothing. I've now noticed this with 2 different cds. I took it out and checked the connections, the solder has held up well it appears. Also, I measured with a multimeter on AC voltage and did pick up a voltage across the terminals of the speaker (woofer and binding posts to the xover as well), so the crossover should be ok (at least in the sense that it is allowing power to the speaker). Connections to the voice coil didn't appear bad either...but I'm out of ideas as to what to look for...any thoughts? I'm soon to be replacing these speakers, but will want them back in service in a few years as we will be building a theater room. Right now they are getting replaced for smaller speakers (Dali Ikon 6's) as they are quite large (about 44" H x 24" W x 10" D) for a little better appearance upstairs in the living room. Any thoughts or suggestions would be appreciated. Thanks guys!

 

[JKL1960]

First thing I would do is swap them side to side. You can just switch the wire. If the problem moves to the other speaker then it is probably not the speakers and occurring before them. If the problem stays with the bad speaker then it is likely that speaker.

Connect the suspect woofer directly to the amp, bypassing your xover. If it seems to sound normal then your xover is probably the issue. If it is still dead then it's probably the driver. ETA: It would be a good idea to measure ohms across the speaker to make sure it isn't shorted somehow before hooking up an amp.

That's what I would do. Good luck.

 

[TLS Guy]

First thing I would do is swap them side to side. You can just switch the wire. If the problem moves to the other speaker then it is probably not the speakers and occurring before them. If the problem stays with the bad speaker then it is likely that speaker.

Connect the suspect woofer directly to the amp, bypassing your xover. If it seems to sound normal then your xover is probably the issue. If it is still dead then it's probably the driver. ETA: It would be a good idea to measure ohms across the speaker to make sure it isn't shorted somehow before hooking up an amp.

That's what I would do. Good luck.

If you have a meter check the DC impedance of the voice coils, that will tell you if the driver is functional. If the voice coil is out, Madisound can re cone the speaker. I bet you will find an open circuit voice coil on the nonfunctional woofer. If you have not been driving it hard and the voice coil is open circuit, check your amp for DC offset. Don't swap speakers until you know the amp does not have DC offset, otherwise you may re cone two speakers.

 

[trnqk7]

I measured about 3.5 ohms across the voice coil (it's wired up in parallel across the dual voice coils). As the connections are all soldered and I don't have a soldering iron (I built these before I moved out of my parents house while I was still in high school...about 7 yrs ago) it will be a little messy/difficult to swap the speakers. Oh well, perhaps a slow project in the months to come after they get temporarily mothballed anyway. Any other thoughts?

 

[Rickster71]

Oh well, perhaps a slow project in the months to come after they get temporarily mothballed anyway. Any other thoughts?

Gently push the cone in and out with your hand.
(Spread your fingers wide, to distribute the force)
Do you feel, or hear binding, in the bad driver?

 

[JKL1960]

TLS is the guy.

I would think that you should completely disconnect the woofer before you measure the resistance otherwise you might just be measuring the crossover that's still connected. If it's a dual voice coil you should probably check them separately.

 

[TLS Guy]

TLS is the guy.

I would think that you should completely disconnect the woofer before you measure the resistance otherwise you might just be measuring the crossover that's still connected. If it's a dual voice coil you should probably check them separately.

He will not measure the resistance of the crossover. In a woofer crossover all the inductors will be in series with the woofer. Only the caps are in parallel and they have exceedingly high DC resistance. There will be no L-pads in a woofer crossover.

That is what the DC resistance should be. Take your ohm meter and put it across the input terminals of the enclosure. You should get a reading slightly above the 3.5 ohm. If not, there is an open circuit somewhere between the input terminals and the speaker. You should be able to solve this one very easily with a little applied logic. Yes and do make sure the woofer cone is free without gap rub.

 

[trnqk7]

I'm going to hazard that there must be an open somewhere, although I am not sure-the woofer cone is easily pushed and makes no sound and I don't feel anything any different than any other woofer I've ever pushed on before (playing around with car audio subs, etc). What kind of voltage should I be measuring across the speaker? When I checked, I did measure AC voltage, but I think the batteries are slowly dying in the meter, as at one point it was a little over .6V-.7V and another time it said 90-112V (yes, I was changing the scale to check as I wasn't sure what voltage level to expect). Both were varying in time with the music, during loud bass passages, the voltage seemed to increase a little. Although in thinking about it, this doesn't make sense...that is how the current should be behaving, not the voltage...I will slowly start to check things out one piece at a time. These speakers are going into temp. retirement anyway in a few weeks. Thanks again for the input! And let me know if there are more ideas-I will amass as many as you guys will give me and slowly try them out.

 

[trnqk7]

I forgot to mention, when measuring across the terminals of the entire speaker, I don't get an impedance reading-it shows it as being open. I am assuming that I just was not able to get the leads into a good contact position. The mids and highs are still operable and have plenty of output. Thoughts?

 

[TLS Guy]

I forgot to mention, when measuring across the terminals of the entire speaker, I don't get an impedance reading-it shows it as being open. I am assuming that I just was not able to get the leads into a good contact position. The mids and highs are still operable and have plenty of output. Thoughts?

Then the voice coil is burnt out. Make sure you have good contact with the speaker terminals and disconnect it from the crossover. I have a feeling this is the problem it nearly always is. If it is open circuit, get a quote from Madisound for re coning.

Voltage measurements will be all over the map, and you should be able to solve this one just with the ohmmeter.