Hello to all,
I recently have been looking for a different pair of speakers for my workshop and ran into what the label says is an A25 Scandyna product. However, when I took off the grille cloth, there were three speakers and no vent.
It appears that this is actually an M25 via the good folks of the interwebs and that is was built before the A25. That might explain why the sticker reads 4 Ohms and the speaker terminals say 8 Ohms. (Which is also what the impedance is-- DC resistance at 7 Ohms)
The sound for an extremely cheap pair of speakers is surprisingly good-- the highs are very present and clean with a nice mid range as well as plenty of bass, much more than I expected with a sealed cabinet. However, I did find the bass a bit boomy so I decided to open the cabinet and see what was inside.
Basically, the cabinets are very cheap particle board and the front baffle is loose on one speaker. It appears the baffles are stapled in at an angle and one in the corner by the bass missed so the whole baffle can flex.
As the speakers sound much better than I expected, and they seem to be a nice match with my Dynaco Stereo 35, how would I go about repairing the cabinets? As the original glue pulled quite a bit of the wood around the woofer, I am thinking it might have to be reglued?
Would it make more sense to build new cabinets all together? (Including putting the drivers in a row, or does this not matter so much?)
Thank you for any help!
I recently have been looking for a different pair of speakers for my workshop and ran into what the label says is an A25 Scandyna product. However, when I took off the grille cloth, there were three speakers and no vent.
It appears that this is actually an M25 via the good folks of the interwebs and that is was built before the A25. That might explain why the sticker reads 4 Ohms and the speaker terminals say 8 Ohms. (Which is also what the impedance is-- DC resistance at 7 Ohms)
The sound for an extremely cheap pair of speakers is surprisingly good-- the highs are very present and clean with a nice mid range as well as plenty of bass, much more than I expected with a sealed cabinet. However, I did find the bass a bit boomy so I decided to open the cabinet and see what was inside.
Basically, the cabinets are very cheap particle board and the front baffle is loose on one speaker. It appears the baffles are stapled in at an angle and one in the corner by the bass missed so the whole baffle can flex.
As the speakers sound much better than I expected, and they seem to be a nice match with my Dynaco Stereo 35, how would I go about repairing the cabinets? As the original glue pulled quite a bit of the wood around the woofer, I am thinking it might have to be reglued?
Would it make more sense to build new cabinets all together? (Including putting the drivers in a row, or does this not matter so much?)
Thank you for any help!
Attachments
I wonder if someone reporposed the box. The XO definitly has the same look as an A25 one, just with an extra cap & coil.
The little peerless tweeter is quite nice, looks like the foil cap gas been dented, one can carefully press it into a concave shape as a fix.
Are there open gaps under teh mids and tweeters?
The woofer looks very much like it is one that didn’t quite fill the hole — i have had to use screws in that many to solve the same issue.
New proper boxes made with quality plywood would definitly better, but if the one you have are already retrofitted you may also try to get the woofer T/S and optimize the box (would also allow for vertical placement of the mid & tweeter and perhaps mirror image.
dave
The little peerless tweeter is quite nice, looks like the foil cap gas been dented, one can carefully press it into a concave shape as a fix.
Are there open gaps under teh mids and tweeters?
The woofer looks very much like it is one that didn’t quite fill the hole — i have had to use screws in that many to solve the same issue.
New proper boxes made with quality plywood would definitly better, but if the one you have are already retrofitted you may also try to get the woofer T/S and optimize the box (would also allow for vertical placement of the mid & tweeter and perhaps mirror image.
dave
thank you for the reply...
I don't think the box was repurposed as I found very similar photos when I looked for dynaco m25 which evidently was produced for a couple of years before the a25.
On the classic speaker pages website (which appears to be down now) there are a few photos of exactly the same drivers and positioning.
There are no gaps under the tweeter and mids-- they look to be glued down with the same black stuff that was used on the woofer. I wonder if silicone could be used as a substitute here if I do try to reinstall the woofer?
The woofer fits but doesn't have any screw holes, if you look for photos of the A25s you will see they are also held in place with glue and four screws on the edges!
How does one find the T/S parameters for unknown drivers?
I don't think the box was repurposed as I found very similar photos when I looked for dynaco m25 which evidently was produced for a couple of years before the a25.
On the classic speaker pages website (which appears to be down now) there are a few photos of exactly the same drivers and positioning.
There are no gaps under the tweeter and mids-- they look to be glued down with the same black stuff that was used on the woofer. I wonder if silicone could be used as a substitute here if I do try to reinstall the woofer?
The woofer fits but doesn't have any screw holes, if you look for photos of the A25s you will see they are also held in place with glue and four screws on the edges!
How does one find the T/S parameters for unknown drivers?
That stuff is terrible. I would suggest new baffles at a minimum, and use closed cel neoprene door seal tape (darft exclusion tape) for gaskets.
An opportunity to at lease reconfigure the driver arrangement.
Another reason for doing it that way. There are proSound L-shaped clips that are better (and move the screws further out), that would be better, or at least bigger washers.
Don’t need to do that, i have dissambled many, i even had a workbench made from 6 x A25 boxes with thebaffles removed (until it just collapsed and i burned it).
One of the reasons i did drawings for all the Dynas i took apart, they deserve better plywood boxes.
Dynaco Enclosure Plans
Measure them. The testers that typical diyers used are not as useful as factory data (much pricier and NLA SW/HW) for box design in my experience. I only use it if it is all i have, but mostly for driver matching.
The manual method (i used the one from Brian Steel’s site) only needs a beefy amp, a signal generator, a VOM, and an R and gives more useful numbers than most diy test kits.
The boxes are sealed? I would suspect compromised on volume to push the price down (raw materials & shipping). If that is the case, a little bigger would be better, but sealed, once you get to a certain size, gets a lot bigger fast with little change in response. And volme fill damping can compensat esomewhat for a too small as box.
Sometimes alnico motors degrade over time, which pushes Qt up which indicates a larger box (and lower sensitivity).
dave
If I use my DATS V2 tester on a brand new drive and get essentially the same results as are on the factory sheet where is the problem? What if there is no factory data?
Granted the current DATS V3 costs $130 but it's a lot of bang for those bucks.
You are lucky. But it is reassuring.
If your drivers do not have factory data, then they are either vintage or not s driver i would buy if new.
If the measured data is not available your measurement is the only data you have. Most often it is a higher Qt.
Measure on a day when the weather is different you will get a different result, T/S are curves not scalars and the number swe use are picked at one spot.
I haven’t used either DATS 2 or 3, bu tthe authou tof the DATS 3 said he was using what i call, The Guess Method.
dave
If your drivers do not have factory data, then they are either vintage or not s driver i would buy if new.
If the measured data is not available your measurement is the only data you have. Most often it is a higher Qt.
Measure on a day when the weather is different you will get a different result, T/S are curves not scalars and the number swe use are picked at one spot.
I haven’t used either DATS 2 or 3, bu tthe authou tof the DATS 3 said he was using what i call, The Guess Method.
dave
Are you making a baffles for the old box or new speaker box?
For the new speaker enclosure, real T / S parameters are needed.