You can only do basic tests for conductivity on the cap with a DVM. That really means just checking it is not leaky... but large value caps (particularly electrolytic types, bi-polar and normal) are inherently leaky anyway and so a bit of experience is called for.
If in doubt compare with the other crossover. Even meter lead polarity makes a difference with traditional electrolytics because the meter applies a small test voltage and if the cap is reverse biased it will show as leaky in that direction.
Small film caps should have essentially no leakage.
Measure a few you have lying around using different ranges on the meter and get a feel for what to expect.
If in doubt compare with the other crossover. Even meter lead polarity makes a difference with traditional electrolytics because the meter applies a small test voltage and if the cap is reverse biased it will show as leaky in that direction.
Small film caps should have essentially no leakage.
Measure a few you have lying around using different ranges on the meter and get a feel for what to expect.
These Audax specs may help for comparison purposes:
http://www.audax.com/archives/HD20B25H - Catalogue 1982.pdf
Have you examined the driver and moved all of the parts?
Loose dustcap
Loose surround (frame or cone)
Loose spider
Loose neck/triple-joint of cone/former/spider
I have a feeling there is a material failure somewhere if you can't find anything loose like debris.
Later,
Wolf
Loose dustcap
Loose surround (frame or cone)
Loose spider
Loose neck/triple-joint of cone/former/spider
I have a feeling there is a material failure somewhere if you can't find anything loose like debris.
Later,
Wolf
Hey it was worth a try, easy to try etc.
Shame it didnt fix your issue - glad you found St Andrew's Cross!
(Off topic, but I like the UK as a Union, I just sport St George's Cross, because I am English, and we generally seem reluctant to tell anyone! That shouldn't be the case and so. )
Quick first look the Monacor would probably be a very good first choice; You could think about Mark Audio or Fostex full range; they would most likely improve your mid range but more costly as well...just another alternative.
Hi all.
Aye, I’m still holding out on trying to find something structural here, an easy fix would be good. Ultimately though, these things need their surrounds replaced as they will be not performing to their ultimate capacity, and since it’s seeming to be unlikely there are any suitable surrounds available, it’s starting to look like replacing.
As you can gather, my knowledge on all of this is fairly limited. I compared the specs Galu kindly linked to for the Audax, to that of the monacor, and to me, they look fairly similar. The monacor Audax drops off a bit towards 5k whereas the monacor is quite proud there, which to my seems like a good thing, although that could perhaps translate into a grating plasticky edge to the midrange. I can’t tell. I’ve such little experience with this stuff.
I’m guessing if Steve recommended the monacor, it must be a good goer as a replacement though. Wouldn’t look too out of place aesthetically too, since it’s design is based on kef b200 I think. Might be tricky physically to install though as the screw holes are a a few mm out, and my cabinets have threaded inserts for the machine screws to go into. Would need to get a router into the baffle to countersink it properly too.
Regardless of fitting to the baffle, does anyone have any more thoughts regarding suitability in terms of frequency response etc? Would these likely be able to drop in without crossover mods?
Was there specific mark audio or fostex drivers you were thinking of Oldspkrguy? Improved midrange would be a bad thing!
Aye, I’m still holding out on trying to find something structural here, an easy fix would be good. Ultimately though, these things need their surrounds replaced as they will be not performing to their ultimate capacity, and since it’s seeming to be unlikely there are any suitable surrounds available, it’s starting to look like replacing.
As you can gather, my knowledge on all of this is fairly limited. I compared the specs Galu kindly linked to for the Audax, to that of the monacor, and to me, they look fairly similar. The monacor Audax drops off a bit towards 5k whereas the monacor is quite proud there, which to my seems like a good thing, although that could perhaps translate into a grating plasticky edge to the midrange. I can’t tell. I’ve such little experience with this stuff.
I’m guessing if Steve recommended the monacor, it must be a good goer as a replacement though. Wouldn’t look too out of place aesthetically too, since it’s design is based on kef b200 I think. Might be tricky physically to install though as the screw holes are a a few mm out, and my cabinets have threaded inserts for the machine screws to go into. Would need to get a router into the baffle to countersink it properly too.
Regardless of fitting to the baffle, does anyone have any more thoughts regarding suitability in terms of frequency response etc? Would these likely be able to drop in without crossover mods?
Was there specific mark audio or fostex drivers you were thinking of Oldspkrguy? Improved midrange would be a bad thing!
Well, something that would physically fit to make it easier. Just a suggestion, have a look at the specs, curves, etc. Most likely you need some crossover mods unless you find a replacement that is a VERY close match to the originals.
The monacor very nearly physically fits, the outer diameter is just a couple of mm smaller, but it’s where the screws attach, the Audax have kind of dog ear bits that go over the front of the baffle, and the mounting hole is completely round, whereas the monacor would be Ed the baffle to be routed out at the corners. Unless I could somehow mount it not countersunk, and gasket it enough so it seals and modify the screw holes just enough for the monacor to fit.
Here are pics of the audaxes and the monacors in question.
Google Image Result
MONACOR: SPM-205/8
Surely finding drivers with the same kind of dog ear mounts, same screw hole diameter, and suitably similar performance is too tall an order.
Here are pics of the audaxes and the monacors in question.
Google Image Result
MONACOR: SPM-205/8
Surely finding drivers with the same kind of dog ear mounts, same screw hole diameter, and suitably similar performance is too tall an order.
Does anyone know anything about these? They’re aparently from the seventies,
look like they’d at least physically fit, but I can’t find any specs for them online. VINTAGE PAIR OF PEERLESS PT210M/8 8" BASS SPEAKERS DRIVERS DENMARK 1970S | eBay
look like they’d at least physically fit, but I can’t find any specs for them online. VINTAGE PAIR OF PEERLESS PT210M/8 8" BASS SPEAKERS DRIVERS DENMARK 1970S | eBay
Special foam ring for Peerless PT210M woofer.
I did find this; I guess original with foam surrounds. It certainly LOOKS similar; even if they still work; most likely you would need new surrounds. I think the most modern surrounds these days that are foam based hold of a lot longer but decades ago, the foam usually ALWAYS dry rotted...
Give me something to do today! I'll keep looking!
I did find this; I guess original with foam surrounds. It certainly LOOKS similar; even if they still work; most likely you would need new surrounds. I think the most modern surrounds these days that are foam based hold of a lot longer but decades ago, the foam usually ALWAYS dry rotted...
Give me something to do today! I'll keep looking!
If I were you, I'd pin my hopes on being able to copy the one working mid, so wouldn't do any experimental surgery on it.
When using different model replacements (when you don't have full comparable specs on both) you'll need to do a controlled sound measurement.
To increase the validity of a single measurement which simplifies the measurement process, you should select a replacement which is similar.. mainly cone size, but material as well might benefit.
It will be almost necessary that the replacement is at least as sensitive as the original.
After which we can discuss how to make one just like the other.
When using different model replacements (when you don't have full comparable specs on both) you'll need to do a controlled sound measurement.
To increase the validity of a single measurement which simplifies the measurement process, you should select a replacement which is similar.. mainly cone size, but material as well might benefit.
It will be almost necessary that the replacement is at least as sensitive as the original.
After which we can discuss how to make one just like the other.
Don’t worry, there was never any talk of any experimental surgery on any working original drivers.
I either would like to have the originals restored, both need new surrounds.
This is looking increasingly unviable, so removal of them being replaced by something as similar as possible in both sides is looking like the best option for the health of these speakers, and I’ll store the originals incase it one day becomes possible to have them repaired.
The monacor spm 205/8 as suggested by Steve, looks to be pretty close in terms of cone size, material, and specs. although would probably require some minor routing of the existing baffle hole to countersink.
These peerless also look like they could be contenders. They’d certainly be easier to fit. Im wondering if anyone here has experience of them. I can’t find much mention of them online.
Shared album - david colin Tunstall - Google Photos
And here is the link to the monacors MONACOR: SPM-205/8
And the specs of the original drivers http://www.audax.com/archives/HD20B25H - Catalogue 1982.pdf
I’m inexperienced and naive with this stuff, so any guidance is very much appreciated. Thanks.
I either would like to have the originals restored, both need new surrounds.
This is looking increasingly unviable, so removal of them being replaced by something as similar as possible in both sides is looking like the best option for the health of these speakers, and I’ll store the originals incase it one day becomes possible to have them repaired.
The monacor spm 205/8 as suggested by Steve, looks to be pretty close in terms of cone size, material, and specs. although would probably require some minor routing of the existing baffle hole to countersink.
These peerless also look like they could be contenders. They’d certainly be easier to fit. Im wondering if anyone here has experience of them. I can’t find much mention of them online.
Shared album - david colin Tunstall - Google Photos
And here is the link to the monacors MONACOR: SPM-205/8
And the specs of the original drivers http://www.audax.com/archives/HD20B25H - Catalogue 1982.pdf
I’m inexperienced and naive with this stuff, so any guidance is very much appreciated. Thanks.
I design and build quite a few amps.
Crossover distortion is usually heard at low listening levels.
As you turn up the volume you hear it less.
As said previously probably a little bit of metal got into the magnet area nad is rattling.
Or some foreign object in the mechanism.
Or maybe voice coil has come apart ?
Crossover distortion is usually heard at low listening levels.
As you turn up the volume you hear it less.
As said previously probably a little bit of metal got into the magnet area nad is rattling.
Or some foreign object in the mechanism.
Or maybe voice coil has come apart ?
Musiciseverything, people say that different drivers sound different. The thing is that when you take two sufficiently similar drivers and take steps to balance their response, these differences can be minimised. Knowing this, and taking a chance on your skills may get you through. The alternative is to obsess over driver options.
Looking for a Visaton WS 20 E - 8 woofer? - SoundImports
Available in 8 Ohm and 4 Ohm both. Maybe this would work; low cost alternative
Looking for a Visaton WS 20 E - 8 woofer? - SoundImports
getting a wide band driver that size with that shape basket and mounting ears is very limited it seems. Maybe give up the exact mounting configuration and just find the closest driver with a regular round frame?
Available in 8 Ohm and 4 Ohm both. Maybe this would work; low cost alternative
Looking for a Visaton WS 20 E - 8 woofer? - SoundImports
getting a wide band driver that size with that shape basket and mounting ears is very limited it seems. Maybe give up the exact mounting configuration and just find the closest driver with a regular round frame?
Those look like they could potentially be goers, they extend up a decent amount which could be handy, although being a bit bigger, would need a bit of baffle surgery to fit. Why do you say I need a wide range driver? The audaxes in question, although 8”, are only being used as squawkers, so it’s just the upper mids that need to be looked at here. I’m not at home right now but I’ll run my sine wave generator and figure out by ear where roughly it’s crossed over top and bottom.
Allen B, I’m all for getting drivers in and changing crossover parts to get them sounding right. I just literally have no idea what I’m doing here. I’m looking at spec sheets and comparing them to my drivers, and they are not the same numbers, but I don’t have the experience of knowing how much these difference will affect the sound. I’m guessing something of a similar efficiency and if higher, can be tamed down with an L pad.
I’m rather hoping that someone will give me the go ahead on a good replacement driver, probably something that’s at least in the ball park, and has the frequency response to suit the situation I’d be asking of it. Then I’d be happy to be advised on what to do to the crossover to get it sounding right.
I found these audaxes like mine on eBay, surrounds look relatively still concave and not stretched and flat like mine. However, as is usually the case when these rare audaxes come up for sale, is that they are the more common smaller magnet J iterations, whereas mine are the larger magnet H ones.
I don’t even know what this means, the magnet size difference in terms of getting them to work and sound the same or if it’s even possible. Could I get these to work? Pair (2) Polydax (Audax) 8" speakers drivers woofers - France - Working | eBay
Allen B, I’m all for getting drivers in and changing crossover parts to get them sounding right. I just literally have no idea what I’m doing here. I’m looking at spec sheets and comparing them to my drivers, and they are not the same numbers, but I don’t have the experience of knowing how much these difference will affect the sound. I’m guessing something of a similar efficiency and if higher, can be tamed down with an L pad.
I’m rather hoping that someone will give me the go ahead on a good replacement driver, probably something that’s at least in the ball park, and has the frequency response to suit the situation I’d be asking of it. Then I’d be happy to be advised on what to do to the crossover to get it sounding right.
I found these audaxes like mine on eBay, surrounds look relatively still concave and not stretched and flat like mine. However, as is usually the case when these rare audaxes come up for sale, is that they are the more common smaller magnet J iterations, whereas mine are the larger magnet H ones.
I don’t even know what this means, the magnet size difference in terms of getting them to work and sound the same or if it’s even possible. Could I get these to work? Pair (2) Polydax (Audax) 8" speakers drivers woofers - France - Working | eBay
By wide band I mean higher frequency extension than is normal for a nominal 8 inch driver. If you look at 8 inch woofers and mid-woofers, most are never used above 2000 Hz, usually best if used at 1200 Hz or lower.
Another possible?
Peerless Drivers - Tymphany
Vifa/Peerless/Tymphany related had this and similar models nominal 8 inch that are smooth past 3000 Hz. That is why I was mentioning full range; better mids and more FR extension even in something 8 inches.
Just ideas as I think of them
Looking for a Peerless HDS-P830869 woofer? - SoundImports
Vifa M21WG-09-08 Heybrook HB1, Snell Type K, JPW P1 / AP2 / AP3 Woofer - Willys-Hifi Ltd
and so on...
Another possible?
Peerless Drivers - Tymphany
Vifa/Peerless/Tymphany related had this and similar models nominal 8 inch that are smooth past 3000 Hz. That is why I was mentioning full range; better mids and more FR extension even in something 8 inches.
Just ideas as I think of them
Looking for a Peerless HDS-P830869 woofer? - SoundImports
Vifa M21WG-09-08 Heybrook HB1, Snell Type K, JPW P1 / AP2 / AP3 Woofer - Willys-Hifi Ltd
and so on...