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To Dope or NOT

StimpyWan said:
I've tried Wet Look before, and didn't hear anything negative after. I mainly used it to help improve the appearance of some old, mildew stained woofers.

Members over at DIY Audio did some tests on woofers, before and after, using Wet Look. As far as they could tell, it didn't adversely affect performance. Most felt it stiffened the cone, improving transient response and bass detail. With the weight of the coating, it could slightly lower the resonance frequency of the woofers. But, that might not be a bad thing either. Heck, a lot of British speakers used to have doped paper cones, prior to polypropylene, I suppose. The cones must have been doped, due to someone in design, believing there was a benefit?
Click to expand...

That is poor advice and it is based upon internet "facts" which have been debunked.

Problem: You won't hear a difference because acoustic memory is notoriously unreliable. Without an A/B comparison it is impossible to say what the effect was. That diyAudio discussion was, I believe, in the context of altering cone properties. Cone alteration is not something to be casually done to a vintage speaker.

Using PVA (aka white glue) would be disastrous, as has been well documented here and on Classic Speaker Pages. RoyC and others tested different sealants on AR-3 drivers, i.e. they actually did experiments, and aside from butylene rubber all of them ruined the surrounds and the speakers. Every. Single. One. Some hardened over a period of months, but harden they did and ruin the sound they did.

The PVA cult refuses to understand that hardening or stiffening a surround raises Fs, which ruins the speaker. It may also create or exacerbate a resonance problem. Gasket cement or diluted silicone are just as bad. This has been well documented with actual experiments, yet the dogma and internet lore simply will not die. People want to believe they can "fix" something when they don't understand the chemistry or materials involved.

I urge everyone to do research on this before applying anything to a surround. Once the surround (or cone) is modified it cannot be restored, it must be replaced.

Ken Kantor, who actual understands these things has many times explained the issues involved and how difficult it is to return a refoamed driver to its original functioning:
ken kantor said:
But, with a woofer, a careful job can get the driver functioning at least somewhat within the ballpark of the original. ...

However, with something like a midrange, the changes wrought by refoaming will be really extreme. There is almost zero chance of getting something close to the original performance, and the refoamer generally has no way to check was has been done.
Click to expand...

ken kantor said:
How in the world do you folks know there weren't significant response changes from your midrange repairs? As a speaker manufacturer, I've seen tens of thousands of mids scrapped because a glue was applied at the wrong temperature or the cross section curvature of a surround roll was slightly off from print.
Click to expand...

PVA (white glue) is not the material to use. It is stiff and rigid. Adding mass to the cone by painting it is a bad thing as the motor (voice coil and motor) was designed to move a specific mass, not the "improved" cone mass. This is not science, it is unsubstantiated opinion which has been debunked, over and over, yet people keep repeating dogma they read as if it were proven fact. When a cone is altered, (a) its mass increases and (b) its resonance properties change. This alters the sound. Speaker designers expend a lot of effort making cones lightweight for better and more linear frequency response. I don't know why aesthetics (does a shiny cone really look "better"?) encourages people to degrade the sound.

Actual science and testing has been done by Roy C to evaluate the effects of various surround dopants. Other than butylene rubber ALL of them, every single one, stiffened the surround and raised Fs. In short, other dopants ruined the speaker. Butylene rubber does not harden and thus does not stiffen the surround. (Think chewing gum which remains sticky for decades.) Roy's work remains definitive on the subject and he brought clarity which finally dispelled the audiophool miasma, although it keeps creeping back into town.

Here's a few of the discussions here about how PVA, gasket cement, etc. ruin the speakers.

For the source material go to Classic Speaker Pages. Too much there to link. Google is your friend.

This is a long-settled and well-settled issue. The research is out there.
 
I'm sorry if I said something that upset you. That was never my intention. I'm also not in the habit of promoting falsehoods, or to compound bad advise. Typically, I usually express my opinion when it's based on my own personal experiences. So, in this case, that is what happened.

My Acoustic Research AR90 speakers were stored in a basement for some time, at one point. Due to the dampness of the basement, the woofers and lower midrange (to a lesser extend) developed some minor mold and mildew discoloration. As a fix, I allowed the drivers to air dry in the sun. Then I brushed off any loose material. But, the woofers were still noticeably stained. That's when I started researching woofer treatments. That lead to Wet Look, and that lead to researching other's user experiences. DIY Audio and the Parts Express Tech Forum were some of the few sites to discuss Wet Look, and the results.

Based on these online reviews, I ordered a can of the Wet Look. I coated and tested (A/B comparisons) the results, a woofer at a time. With their 2 woofers per speaker, my AR90s allowed for a number of before-and-after trials. That I coated all 4 woofers, speaks to the conclusion that I found no negative side effects.

As to PVA (white glue), I've never endorsed it's use in coating a driver surround. That would be obviously disastrous. I have read about using thinned yellow wood glue to dope paper cones. But again, not as a doping agent for the surround. The late Brian Cheney, of VMPS loudspeakers, supported the use of yellow wood glue, to treat paper woofer cones. Especially when used to seal and stiffen the various passive radiators used in his designs. Brian even coined the term 'vitrifying', when describing the process.

Again, my endorsement of woofer doping, using Wet Look, is based on personal experiences. Nothing nefarious intended. Nothing to debunk. I was just trying an experiment, having fun, and enjoying music. That's what it's all about to me. Other's mileage may vary? :)

Retrovert said:
That is poor advice and it is based upon internet "facts" which have been debunked.

Problem: You won't hear a difference because acoustic memory is notoriously unreliable. Without an A/B comparison it is impossible to say what the effect was. That diyAudio discussion was, I believe, in the context of altering cone properties. Cone alteration is not something to be casually done to a vintage speaker.

Using PVA (aka white glue) would be disastrous, as has been well documented here and on Classic Speaker Pages. RoyC and others tested different sealants on AR-3 drivers, i.e. they actually did experiments, and aside from butylene rubber all of them ruined the surrounds and the speakers. Every. Single. One. Some hardened over a period of months, but harden they did and ruin the sound they did.

The PVA cult refuses to understand that hardening or stiffening a surround raises Fs, which ruins the speaker. It may also create or exacerbate a resonance problem. Gasket cement or diluted silicone are just as bad. This has been well documented with actual experiments, yet the dogma and internet lore simply will not die. People want to believe they can "fix" something when they don't understand the chemistry or materials involved.

I urge everyone to do research on this before applying anything to a surround. Once the surround (or cone) is modified it cannot be restored, it must be replaced.

Ken Kantor, who actual understands these things has many times explained the issues involved and how difficult it is to return a refoamed driver to its original functioning:




PVA (white glue) is not the material to use. It is stiff and rigid. Adding mass to the cone by painting it is a bad thing as the motor (voice coil and motor) was designed to move a specific mass, not the "improved" cone mass. This is not science, it is unsubstantiated opinion which has been debunked, over and over, yet people keep repeating dogma they read as if it were proven fact. When a cone is altered, (a) its mass increases and (b) its resonance properties change. This alters the sound. Speaker designers expend a lot of effort making cones lightweight for better and more linear frequency response. I don't know why aesthetics (does a shiny cone really look "better"?) encourages people to degrade the sound.

Actual science and testing has been done by Roy C to evaluate the effects of various surround dopants. Other than butylene rubber ALL of them, every single one, stiffened the surround and raised Fs. In short, other dopants ruined the speaker. Butylene rubber does not harden and thus does not stiffen the surround. (Think chewing gum which remains sticky for decades.) Roy's work remains definitive on the subject and he brought clarity which finally dispelled the audiophool miasma, although it keeps creeping back into town.

Here's a few of the discussions here about how PVA, gasket cement, etc. ruin the speakers.

For the source material go to Classic Speaker Pages. Too much there to link. Google is your friend.

This is a long-settled and well-settled issue. The research is out there.
Click to expand...
 
StimpyWan said:
I'm sorry if I said something that upset you. That was never my intention. I'm also not in the habit of promoting falsehoods, or to compound bad advise. Typically, I usually express my opinion when it's based on my own personal experiences. So, in this case, that is what happened.
Click to expand...

Sigh. I wasn't "upset". I was concerned that someone without adequate technical background would follow these recommendations and destroy a set of speakers. I have heard many such stories which end with a statement along the lines of why didn't someone post that this wasn't true, everyone said it worked.

StimpyWan said:
My Acoustic Research AR90 speakers were stored in a basement for some time, at one point. Due to the dampness of the basement, the woofers and lower midrange (to a lesser extend) developed some minor mold and mildew discoloration. As a fix, I allowed the drivers to air dry in the sun. Then I brushed off any loose material. But, the woofers were still noticeably stained.
Click to expand...

I am unconcerned with appearance of the cone, only its sound matters.

Adding mass will change the sound.

StimpyWan said:
That's when I started researching woofer treatments. That lead to Wet Look, and that lead to researching other's user experiences.
Click to expand...

Wet Look is described as a high-gloss polymer. It will alter the cone mass and its flexibility. Get it on the surround and that will alter the compliance and thus Fs.

This is basic physics and engineering. How does adding mass to a cone or stiffening the surround not alter the sound of the speaker?

StimpyWan said:
DIY Audio and the Parts Express Tech Forum were some of the few sites to discuss Wet Look, and the results.
Click to expand...

Which appear to be "to my ears" instead of objective measurements.

StimpyWan said:
Based on these online reviews, I ordered a can of the Wet Look. I coated and tested (A/B comparisons) the results, a woofer at a time. With their 2 woofers per speaker, my AR90s allowed for a number of before-and-after trials. That I coated all 4 woofers, speaks to the conclusion that I found no negative side effects.
Click to expand...

Again, you have no frequency plots of the difference in drivers before and after? Only your ears? Again, acoustic memory is unreliable.

Roy C measured the effects of tinkering with surrounds and the Fs can drop. I doubt you can remember an Fs drop of a few Hz. But there it is. And over time as Fs increases as the stiffener hardens you will become accustomed to the distorted sound.

If the cone warps the sound will be distorted and the voice coil can begin to rub, ruining the speaker.

StimpyWan said:
As to PVA (white glue), I've never endorsed it's use in coating a driver surround. That would be obviously disastrous. I have read about using thinned yellow wood glue to dope paper cones. But again, not as a doping agent for the surround. The late Brian Cheney, of VMPS loudspeakers, supported the use of yellow wood glue, to treat paper woofer cones. Especially when used to seal and stiffen the various passive radiators used in his designs. Brian even coined the term 'vitrifying', when describing the process.
Click to expand...

Errr, what do you think the primary ingredient in "yellow wood glue" is? Wood glue is PVA!!!

Cheney was stiffening passive radiators. Taking these techniques and applying them to vintage speakers is disastrous.

StimpyWan said:
Again, my endorsement of woofer doping, using Wet Look, is based on personal experiences. Nothing nefarious intended. Nothing to debunk. I was just trying an experiment, having fun, and enjoying music. That's what it's all about to me. Other's mileage may vary?
Click to expand...

PVA Cult (aka Aleens), Gasket Cement Cult, Silicone Cult, and other such cults have ruined innumerable speaker surrounds.

Endorsing products and promotingchanges which permanently alter speakers is not "having fun". It is promoting ideas which have been extensively researched, tested, and debunked, and people who are not sophisticated may follow this nonsense and ruin speakers. This is actually legally actionable if someone follows your "advice" and destroys the speaker.
 
Oh well. I stand by my contributions here. All were based on my personal experience. I noted what I've tried and why. Nothing stated was meant to be misleading, in the hope that someone would damage a speaker. I don't work that way. I never stated that everyone has to follow my advice either. I don't work that way either. Advice is freely given, not forced upon the recipient.

Peace, and over! :)

About time to lock this thread. It's done. :p
 
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StimpyWan said:
Oh well. I stand by my contributions here. All were based on my personal experience. I noted what I've tried and why. Nothing stated was meant to be misleading, in the hope that someone would damage a speaker. I don't work that way. I never stated that everyone has to follow my advice either. I don't work that way either. Advice is freely given, not forced upon the recipient.
Click to expand...

It is problematic to suggest as beneficial or a "fun" project: (1) adding mass to a cone or surround, (2) stiffening a cone or surround, (3) altering the properties of the paper in a cone or surround. The very act of making the suggestion is misleading given that the results have been thoroughly investigated, analyzed, dissected, refuted, and debunked. What I did was explain the issues and show that much of what was claimed cannot function as claimed and will be detrimental. You have no hard data on the effects, and it the proposed modification is permanent and irreversible.

Multiple Thiele/Small parameter will be affected by your "freely given" advice to coat the cone and surround, including Mms and Mmd (a stiffer cone likely increases the acoustic load so both could be affected), Cms, and Rms. Those, in turn, affect the related parameters of Fs, Qms, Qts, etc.

What you are doing is creating a new driver with different characteristics than the original, yet you have not altered other aspects of the driver to compensate or better mesh with your new cone and surround. This is the key point.

The original driver designers created a voice coil and magnet to drive a particular mass cone with particular mechanical properties. Many cones are an amalgam of multiple materials (typically plant and animal fibers, but synthetic fibers are also used) in order to achieve a certain balance between mass, stiffness, flexibility, and other parameters.

The fact that proponents of a product make unsubstantiated claims as to its wonderous benefits is no substitute for research and testing. PVA, gasket cement, silicone, and a host of other materials have been promoted in such fashion, even though all damage the cone's ability to accurately reproduce sound and this is well known.

Butylene rubber—a sticky, compliant, and non-hardening material dissolved in toluene—is easily applied to the surround and will restore it to proper functioning with a minimum of change in driver characteristics. This has been widely demonstrated and confirmed.

I therefore urge anyone considering such modification to read the work of Roy C and the discussions here and on Classic Speaker Pages.
 
I again point out the cautions of Ken Kantor:
ken kantor said:
But, with a woofer, a careful job can get the driver functioning at least somewhat within the ballpark of the original. ...

However, with something like a midrange, the changes wrought by refoaming will be really extreme. There is almost zero chance of getting something close to the original performance, and the refoamer generally has no way to check was has been done.
Click to expand...

ken kantor said:
How in the world do you folks know there weren't significant response changes from your midrange repairs? As a speaker manufacturer, I've seen tens of thousands of mids scrapped because a glue was applied at the wrong temperature or the cross section curvature of a surround roll was slightly off from print.
Click to expand...

If you don't know who Ken is or why you should pay attention to his advice, you could Google him.
 
N8Nagel said:
How much power are you driving these with? I have several pairs of speakers that sound ''meh" on 30-40 WPC receivers but come alive on 100+ watt power amps or oddly, similar 30-40 WPC tube gear.
Click to expand...

You bring up a wise and vital point. Indeed, I've been wondering how these (rated 35 W, as you know) will sound on my S-C ASR-444 amp (rated 30 wps) when I've finished it. Even a friend of mine tells me to wait on selling these till I hear them on the S-C. And maybe I'll try them on my newer Harman Kardon HK-3490 that I use for computer audio and TV. It has, I think, 110 per side.

And you have me recalling when they blew a fuse on the Advent 300 receiver. Bass seemed to have something to do with causing the blow. Right before the fuse blew, and as I was increasing bass, the woofer started "flopping," then a couple seconds later the fuse blew. I gotta think this ties into what you're saying. Different amps bring out or exaggerate certain characteristics of the speakers. Maybe the Advent brought out too much bass? But then again, as I say, I played the speakers on three other amps with no trouble, one of them a 12 wps Lafayette solid state cheapo receiver, LR-200 I once found in the dumpster.
 
If the thread is to be locked, I'd like to say that I have learned a ton here! And I want this much very clear: I appreciate and thank you all for your help.
 
Retrovert said:
It is problematic to suggest as beneficial or a "fun" project: (1) adding mass to a cone or surround, (2) stiffening a cone or surround, (3) altering the properties of the paper in a cone or surround. The very act of making the suggestion is misleading given that the results have been thoroughly investigated, analyzed, dissected, refuted, and debunked. What I did was explain the issues and show that much of what was claimed cannot function as claimed and will be detrimental. You have no hard data on the effects, and it the proposed modification is permanent and irreversible.

Multiple Thiele/Small parameter will be affected by your "freely given" advice to coat the cone and surround, including Mms and Mmd (a stiffer cone likely increases the acoustic load so both could be affected), Cms, and Rms. Those, in turn, affect the related parameters of Fs, Qms, Qts, etc.

What you are doing is creating a new driver with different characteristics than the original, yet you have not altered other aspects of the driver to compensate or better mesh with your new cone and surround. This is the key point.

The original driver designers created a voice coil and magnet to drive a particular mass cone with particular mechanical properties. Many cones are an amalgam of multiple materials (typically plant and animal fibers, but synthetic fibers are also used) in order to achieve a certain balance between mass, stiffness, flexibility, and other parameters.

The fact that proponents of a product make unsubstantiated claims as to its wonderous benefits is no substitute for research and testing. PVA, gasket cement, silicone, and a host of other materials have been promoted in such fashion, even though all damage the cone's ability to accurately reproduce sound and this is well known.

Butylene rubber—a sticky, compliant, and non-hardening material dissolved in toluene—is easily applied to the surround and will restore it to proper functioning with a minimum of change in driver characteristics. This has been widely demonstrated and confirmed.

I therefore urge anyone considering such modification to read the work of Roy C and the discussions here and on Classic Speaker Pages.
Click to expand...
Thank you for your essential insights.
 
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Retrovert said:
You are welcome.

I hope this ensures your speakers and those of others are not damaged by discredited advice.
Click to expand...
Thanks again. As I say, I appreciate everyone's time and help, but I did have a gut instinct to do nothing more to the speakers than redope the cloth surrounds (and change out the bad capacitors).

Again, I learned a ton from everyone's points of view.
 
Loudspeaker Design Cookbook, 7th edition i think is the latest, my copy was printed in 2006. I wore out the earlier editions I used to have. Anyone wanting a better understanding of loudspeakers would find the information useful, Parts Express sells it.
 
FB night said:
Loudspeaker Design Cookbook, 7th edition i think is the latest, my copy was printed in 2006. I wore out the earlier editions I used to have. Anyone wanting a better understanding of loudspeakers would find the information useful, Parts Express sells it.
Click to expand...
Hi, thanks!
 
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