Hi all, 9 plus year lurker, first time poster here.
I recently acquired a pair of Electro Voice Interface D's. I made the decision to apply new dope to my surrounds and am in fear that I overdid something. Long story short, when I first hooked them up, I found them to have somewhat "hand cupped around mouth" mids, with them also sounding too pronounced and somewhat disconnected from the woofer/tweeter. When looking into work I should do to them, I stumbled across several people describing them as "stiff", etc. and noticed that mine seemed pretty flexible and closer to plain fabric, maybe slightly doped at best. Further investigation brought me upon the excellent thread by @PeterSchut wherein he had this to say concerning doping:
Based upon this recommendation, I went ahead and bought the PVA based MI-1291FG surround sealant. When applying it, I didn't think to water it down, and simply went straight to applying it. It was thick enough that it was relatively difficult to spread, I estimate needing to use >10-12 healthily sized drops of it per surround to get a somewhat even coating. See here for how it looked before fully curing:
And the day after:
Note: in my haste, I didn't fully apply coating to the very inside or outside of the surrounds. See those areas as reference for what my surrounds looked like beforehand.
At the same time as coating them, I also recapped them and bypassed the tweeter protection circuitry. In retrospect, I probably should have listened in between or started with just the recap. I did not change any capacitance values and am confident that I didn't accidentally alter the circuit in any way.
In any case, now that they've had the work done, I still don't find the sound of the mids to be right. They are missing some snap/presence and lower mid body to my ears. When measuring one playing pink noise with my phone microphone, I noticed a wide dip between about 2k and below the crossover point at 3k:
The red line is peak and what is useful to be looking at here. I am aware that this isn't the best measurement, but it does corroborate what I'm hearing. I had the tweeter set to -9db for this measurement.
Also shown is a tight peak just below 1k that is audible to me as well. In addition, I am hearing what sounds like breaking up/minor distortion on some sustained tones, very close-mic'd piano, etc. The upper mids sound very lax and unergetic, and as a whole the mids still sound a bit disconnected and hollow. Though these (or maybe all of this...?) may have been there before I did any work. Is it possible I overdoped? Underdoped? Neither?
I have also since read some PVA horror stories, such as from the venerable RoyC:
It is also my understanding that PVA can cause a surround become too stiff, and reflect energy back into the driver and cause breakup, though if the VMR surrounds are supposed to be as stiff as people say, I'd hope that wouldn't be some of my current issue.
Here are some videos demonstrating how they sounded before:
and after:
and something demonstrating surround "springiness" to the best of my ability:
These have been my dream speakers for a while, so I wouldn't like to give up on them just yet. If need be I am willing to source replacement surrounds, drivers, etc. or purchase something like a Dayton DATS.
Many Thanks,
Isaac
I recently acquired a pair of Electro Voice Interface D's. I made the decision to apply new dope to my surrounds and am in fear that I overdid something. Long story short, when I first hooked them up, I found them to have somewhat "hand cupped around mouth" mids, with them also sounding too pronounced and somewhat disconnected from the woofer/tweeter. When looking into work I should do to them, I stumbled across several people describing them as "stiff", etc. and noticed that mine seemed pretty flexible and closer to plain fabric, maybe slightly doped at best. Further investigation brought me upon the excellent thread by @PeterSchut wherein he had this to say concerning doping:
Based upon this recommendation, I went ahead and bought the PVA based MI-1291FG surround sealant. When applying it, I didn't think to water it down, and simply went straight to applying it. It was thick enough that it was relatively difficult to spread, I estimate needing to use >10-12 healthily sized drops of it per surround to get a somewhat even coating. See here for how it looked before fully curing:
And the day after:
Note: in my haste, I didn't fully apply coating to the very inside or outside of the surrounds. See those areas as reference for what my surrounds looked like beforehand.
At the same time as coating them, I also recapped them and bypassed the tweeter protection circuitry. In retrospect, I probably should have listened in between or started with just the recap. I did not change any capacitance values and am confident that I didn't accidentally alter the circuit in any way.
In any case, now that they've had the work done, I still don't find the sound of the mids to be right. They are missing some snap/presence and lower mid body to my ears. When measuring one playing pink noise with my phone microphone, I noticed a wide dip between about 2k and below the crossover point at 3k:
The red line is peak and what is useful to be looking at here. I am aware that this isn't the best measurement, but it does corroborate what I'm hearing. I had the tweeter set to -9db for this measurement.
Also shown is a tight peak just below 1k that is audible to me as well. In addition, I am hearing what sounds like breaking up/minor distortion on some sustained tones, very close-mic'd piano, etc. The upper mids sound very lax and unergetic, and as a whole the mids still sound a bit disconnected and hollow. Though these (or maybe all of this...?) may have been there before I did any work. Is it possible I overdoped? Underdoped? Neither?
I have also since read some PVA horror stories, such as from the venerable RoyC:
I experimented with a number of the white surround "treatments". This group included the stuff sold by Simply Speakers, Orange County, M-Sound, and Global Adhesives (who labels it "white surround dampener"). These are all water soluble/PVA based, and as advertised, dry more flexibly than regular white glue. They are also advertised as being able to be used for a "wet look" on woofer cones. The problem with all of them is that they gradually stiffen. One 3a woofer I experimented on went from an fs of 16hz upon treatment to 32hz after one month!
It is also my understanding that PVA can cause a surround become too stiff, and reflect energy back into the driver and cause breakup, though if the VMR surrounds are supposed to be as stiff as people say, I'd hope that wouldn't be some of my current issue.
Here are some videos demonstrating how they sounded before:
These have been my dream speakers for a while, so I wouldn't like to give up on them just yet. If need be I am willing to source replacement surrounds, drivers, etc. or purchase something like a Dayton DATS.
Many Thanks,
Isaac
