The Fine Art of Pinching Putty - The Why, the How, and the Method

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John Casler

The Fine Art of Pinching Putty - The Why, the How, and the Method

Years and years of putty pinching have given me many insights as to what results to expect.

As most of you know Big B, now does most of the "pre-Pinching" for you so likely you'll be called on to do very little.

What does putty pinching do? 

It adds mass to the Passive radiator to cause it to "cooperate" with the other active bass drivers, in such a way as to "react" to them at a lower frequency, and different phase.

This reaction to the active drivers extends bass response in frequencies lower than the actives, because the Passive Radiator moves slower, and in a different phase.

If the putty is exactly right, this reaction will "seamlessly" add the lower bass extension.

If it is too light or too heavy, it will create cancellation and distortion.

If I have one caution, it would be to tell everyone not to "keep removing" putty.

I would guess that a great percentage of VMPS speakers and subs have "too little" putty damping them.

This causes the PR to react too fast, and will not create the lowest of bass performance.  If the PR reacts too fast it will put out too high a frequency, (closer to the active driver) and this will not give you a clean, well phased frequency, and sound.

So the point is, DO NOT be afraid to "add" putty.

The goal is to adjust the mass to the amount needed to cause the PR to fall within the reactive frequencies and phase.

The sound of too little putty is a bass that doesn't sound low enough, and is a little woolly.  This is caused by the PR moving too fast, and too close to the phase of the active.  It might be described as "lean, yet fuzzy"

The sound of too much putty is the same, except, it will sound deeper and "woolly" or slightly boomy and too full.

I suggested to some to try various positions and orientations of the PR on their subs.  I also suggested that they might "remove" the bass plate, and allow the woofer to "fire" out into the room.

What I might have neglected to mention, was that in doing so, you reduce the impedance or pressurization that the PR sees, and you must "add" putty to make up for this.

So just a little bit more info, on the fine art of "tuning" your speakers, and what you might need to understand in doing so.

Oh and in case you missed it, those with the RM series speaker (RM1/RM2/RM30/RM40 and RM/x) you can "reverse" your passive radiator slot, and cause it to fire rearwards rather than forward, as an experiment to see if that orientation might offer a more pleasing and enjoyable bass performance "in your room".

Have fun,

And

"Stay Tuned" (in all the best ways possible)

soundguy3

John, thanks for that great explanation....I have a question regarding the putty...over these last few years with the Rm 40's, I have removed, added and then subsequently lost the removed putty due to several factors, one of them was the cleaning lady thought it was junk sitting on the edge of the speaker platform and promptly threw it away! :o :o  Now I have no idea what the correct amount should be.... Maybe the best idea is to remove all the putty and start from the beginning...so what is the correct amount that should be in each PR?  I know I could improve the bass response if had the right amount to begin with.

Thanks,

John

rblnr

And what kind of putty is it?  I remember reading 'mortite' -- is this correct?  What should I buy at the hardware store if I need some more?

John Casler

And what kind of putty is it?  I remember reading 'mortite' -- is this correct?  What should I buy at the hardware store if I need some more?

Rope Mortite is the best.

Here are B's suggestions, should you wish to "de-putty" and begin "fresh".

RM30 = 5" each PR
RM1 = 4"
RM2 = 6"
RM40 = 6"
RM/x = 6"
 
Dedicated and Smaller = 7"
Original and 215 sub = 8"
LARGER Sub = 8"

OTL

Hi John,

Does Brian actually start with a measured length of Mortite?  One would think that by know he'd have a quite exact weight measurement that's just a few grams or so on the heavy side.

soundguy3

Hi John,

Thanks for the info......good question Otl......I could not find Mortite....I did find a type of pipe puty that looks very similar and feels the same....Is there a weight for the "6 or 5" inches of the mortite?

Thanks,

John

warnerwh

You can get mortite at Ace or True Value here in town.  It's probably in the window putty area. I have a spool of it still as there's plenty on a roll.
« Last Edit: 6 Aug 2006, 09:42 pm by warnerwh »

mjosef

Mhnn...last time I asked Brian about the original amount of putty for the RM1, he said start with 8". By these posted amounts my speakers are seriously over damped. My RM1s  came with the carbon fiber megawoofers(?) and soundcoat. And I have since done the SR1 and vitrified passive tweeks. During tuning I ended up removing just about 1/2" or so.
Mhnnnnn....

John Casler

Only Mr. B could answer how much the "mass" weighs, but as an aside, in a pinch, I have even used "chewing gum" to add mass, when needed. 8)

John Casler

Mhnn...last time I asked Brian about the original amount of putty for the RM1, he said start with 8". By these posted amounts my speakers are seriously over damped. My RM1s  came with the carbon fiber megawoofers(?) and soundcoat. And I have since done the SR1 and vitrified passive tweeks. During tuning I ended up removing just about 1/2" or so.
Mhnnnnn....

Wonder if he meant 4" each? :scratch:

Hope you have "high damping ratio" amps and short speaker cables :green:


rblnr

Thanks for the info. everybody.

John Casler

I will add some of these numbers to the "set up" sticky for future reference. :rules:


mjosef



Wonder if he meant 4" each? :scratch:

Hope you have "high damping ratio" amps and short speaker cables :green:



Hah, would a Jolida tube amp qualify as "high-damping-ratio"? But hey my speaker cables are 8', thats short.  :lol:
Well I guess I would have to experiment for myself, and compare the sound with 4" vs 8".

I have been wondering though about the legacy of VMPS, would there be a continuation after the "chief" has gone on? Seeing that his work is dependant on his personal participation/touch? Is there a plan in place for the 'future' of VMPS?
Don't get me wrong, I wish Brian the best of health and life, but as a long time VMPS customer (since the late 80's), lately I have been wondering about VMPS without Brian.

fredgarvin

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Wonder if he meant 4" each? :scratch:

Hope you have "high damping ratio" amps and short speaker cables :green:



Hah, would a Jolida tube amp qualify as "high-damping-ratio"? But hey my speaker cables are 8', thats short.  :lol:
Well I guess I would have to experiment for myself, and compare the sound with 4" vs 8".

I have been wondering though about the legacy of VMPS, would there be a continuation after the "chief" has gone on? Seeing that his work is dependant on his personal participation/touch? Is there a plan in place for the 'future' of VMPS?
Don't get me wrong, I wish Brian the best of health and life, but as a long time VMPS customer (since the late 80's), lately I have been wondering about VMPS without Brian.

That is wierd, I was thinking just that, the other day. :lol: I was thinking that if Brian retired or sold out would the "putty" system that has been so important in his designs remain or would it be a better idea to move to powered woofers or perhaps Scanspeak mags or something else that requires less "hands on".

OTL

Hmmm...that's the RM30C versus the RM30M question.......Big B advised M's.....I'm still digesting that direction.......and dreaming about sub's....

John Casler

Well, let's not place B, on the table just yet :lol:

Shirley keeps him young and he is to cantankerous to quit building speakers.

That said, I think at some point the putty pinch system will be replaced with another "secret invention" B has up his sleeve.

He told me about it some time ago and probably hasn't had time to work on it yet.

But adjustable damping on a closed bass system with a PR is one of the best ways to reduce bass distortion, or at least allow you to "dial it down".

Hipper

May I be so bold as to suggest you update the 'So now you own a VMPS "NOW WHAT" Set up Guide' page.

I recently bought RM30M's and there were instructions on the back which say the Level Controls should be at 1200 and 1230 for mids and treble respectively, and that for Bass Damping Adjustment I should 'see instructions for details', instructions which I didn't recieve. I therefore followed the above set up guide, taking a pea size piece of putty from each of the four passive radiators. In doing so I noticed that the front PR of each speaker had been tampered with, possibly some putty having been removed.

I'm leaving it as it is for the time being and will review the situation in a few months when hopefully all the drivers will have been burned in enough.

nathanm

Quote
That said, I think at some point the putty pinch system will be replaced with another "secret invention" B has up his sleeve.
Threaded rod in the center of the PR with rubber washers for the adjustment???  I never liked messing with the damn putty; it's a case where stepped, repeatable increments would be desireable.  That way you can at least say, "8 washers good, 4 washers too boomy" instead of "small greying mass of filthy goo too boomy, large viscous hunk of sludge just right"  I gave up on adjusting the thing and learned to love it as is.  Might be different if I had a 'putty boy' to do all the hard work. 

J

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How would laying an original sub on it's side effect putty amount? I'm thinking about using them on there side after I install the new mega woofers and passives.

John

John Casler

How would laying an original sub on it's side effect putty amount? I'm thinking about using them on there side after I install the new mega woofers and passives.

John

The PR system of the VMPS speakers is affected by gravity, mass, and the impedance/pressurization of the slot. when it is enclosed by the plate or by sitting on the floor.

Each of these elements serves to "control" the performance of the PR.

Placing the Sub on its side reduces the effect of gravity slightly, so you would need to "add" mass (putty).

If you also remove the "slot plate" (Large flat plate that encloses the slot) then the pressurization of that chamber is reduced and a small amount of putty should be added.