Sensitivity Ratings

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oneinthepipe

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Re: Sensitivity Ratings
« Reply #60 on: 28 Jan 2009, 12:57 am »
Modeling clay has been ordered.

Chickens! :flame:

and cowards, too.

S Clark

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Re: Sensitivity Ratings
« Reply #61 on: 28 Jan 2009, 01:32 am »
You don't have a supply in stock??? Haven't you been listening to The Chair Guy on the vinyl circle.  Modeling clay applied generously cures dandriff, increases your IQ, and makes you more attractive to the opposite sex! :rotflmao: :rotflmao:

funkmonkey

Re: Sensitivity Ratings
« Reply #62 on: 28 Jan 2009, 01:48 am »
Forgive my ignorance, but wouldn't some acousticly isolating foam serve well as a dampner between speaker and cabinet?  Thats where we're talking about sticking the clay, no?  The sheet foam could be cut and used like a gasket and be a lot less messy than the clay, though perhaps not quite as effective...

Big Red Machine

Re: Sensitivity Ratings
« Reply #63 on: 28 Jan 2009, 01:56 am »
The speakers already use a compressible gasket to prevent air leaks.

We're talking about adding mass to the spiders or basket of the speaker.

DMurphy

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Re: Sensitivity Ratings
« Reply #64 on: 28 Jan 2009, 02:16 am »
The speakers already use a compressible gasket to prevent air leaks.

We're talking about adding mass to the spiders or basket of the speaker.

Well, I'm not talking about adding mass to the spider.  That's the driver suspension, and you don't want to mess with that.  Maybe you were referring to the support arms of the basket.  I'm still skeptical about all this.  I will try it on one of my ST's.  If I hear the same difference that I heard on the CA12 experiment, then I'll move over into the believer corner. 

avahifi

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Re: Sensitivity Ratings
« Reply #65 on: 28 Jan 2009, 01:24 pm »
The object is not to add mass to the system in this case.  The object is resistive damping of non-moving parts to reduce stray resonances.  Again a test at B&W a few years ago showed acoustic output of the metal speaker basket in one case was only 10dB down from the driven cone at some frequencies.  Note that B&W makes their own speakers with very substantial cast frameworks in most cases.

Glad to hear that you are going to go ahead with the test with a set of Songtowers, Dennis.

Regards,

Frank Van Alstine

P.S.  Note that adding mass properly is not always a bad idea.  Years ago at the home of a group of audiophiles in Barbados, I was given an interesting A-B test of this idea with a big set of bookshelf speakers. The owner had made up a set of very heavy (about 40 pounds as I remember) concrete plates the size of the speaker tops.  They were Naugahyde padded to avoid scratching the speakers and to provide a good contact.  The difference between the speakers with the pads on top and with them removed was very obvious.  Probably Newton's laws of motion at work again. You could here the sound change with your eyes closed as the were placed and removed during play.

DMurphy

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Re: Sensitivity Ratings
« Reply #66 on: 28 Jan 2009, 02:26 pm »
How were the B&W measurements done?  It seems like the basked would have to be open to the air so the sound sources could be isolated.  But inside a cabinet with the cone acting as a barrier of sorts, how do we know the basket would be adding anything audible?  Anyhow, looks like I'll be spending some time damping up my ST's this weekend. 

fishinbob

Re: Sensitivity Ratings
« Reply #67 on: 28 Jan 2009, 03:22 pm »
I love it when it gets all technical like this.

claymation plus concrete... right up my alley. aa Maybe if I put the speakers in some sand.....

avahifi

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Re: Sensitivity Ratings
« Reply #68 on: 28 Jan 2009, 10:08 pm »
B&W does their measurements of raw speakers in free air, clamped in a jig.  They can train the laser anywhere they want to observe cone breakup and whatever else about the driven system that is of interest to them.  They had not looked at the metal baskets until I suggested this to them.  How much of the actual unwanted resonant output from the driver "escapes" into the room when the speaker is in its properly designed cabinet is unknown to me.  However I suspect more than anticipated inasmuch as how much difference resistive damping the the framework seems to make whenever it has been tried.

Regards,

Frank Van Alstine

Zheeeem

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Re: Sensitivity Ratings
« Reply #69 on: 28 Jan 2009, 11:03 pm »

P.S.  Note that adding mass properly is not always a bad idea.  Years ago at the home of a group of audiophiles in Barbados, I was given an interesting A-B test of this idea with a big set of bookshelf speakers. The owner had made up a set of very heavy (about 40 pounds as I remember) concrete plates the size of the speaker tops.  They were Naugahyde padded to avoid scratching the speakers and to provide a good contact.  The difference between the speakers with the pads on top and with them removed was very obvious.  Probably Newton's laws of motion at work again. You could here the sound change with your eyes closed as the were placed and removed during play.


Indeed, having read something similar in an old audio basics, I went to my local stonecutter and had him cut two 3" slabs of limestone with the exact footprint of my subwoofer.  One goes underneath to help decouple from the floor, and the other goes on top - and it's probably 40-50 pounds.  The stone was cheap, it added slightly better clarity and definition, it looks great, and keeps the top of the sub from getting marked up when I use it as an end table.

My stonecutter thought I was nuts, but he didn't complain when I asked him to cut a rack for my entire system plus some stands for my biro L/1s.

rahimlee54

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Re: Sensitivity Ratings
« Reply #70 on: 28 Jan 2009, 11:07 pm »


[/quote]

Indeed, having read something similar in an old audio basics, I went to my local stonecutter and had him cut two 3" slabs of limestone with the exact footprint of my subwoofer.  One goes underneath to help decouple from the floor, and the other goes on top - and it's probably 40-50 pounds.  The stone was cheap, it added slightly better clarity and definition, it looks great, and keeps the top of the sub from getting marked up when I use it as an end table.

My stonecutter thought I was nuts, but he didn't complain when I asked him to cut a rack for my entire system plus some stands for my biro L/1s.
[/quote]

Can you post some pictures of that, just so I can see something I have never seen before.  Espically interested in the rack, that sounds kind of neat.

Rahimlee54

TomW16

Re: Sensitivity Ratings
« Reply #71 on: 29 Jan 2009, 12:38 am »
I designed my speakers cabinets with a 1 inch thick steel plate (~40 lbs) to go between the top cabinet (containing the midrange and tweeter) and the woofer cabinet.  The steel plate is isolated from the cabinets with Sorbothane pads that were sized according to the weight they support. 

I never listened to the speakers with and without the steel plates but they sound pretty good with them so I don't doubt the benefits of added mass to a speaker.

And since this is a Salk thread, that's a Salk T-shirt I'm sporting  8)

Tom




DMurphy

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Re: Sensitivity Ratings
« Reply #72 on: 29 Jan 2009, 03:53 am »
Good heavens.  You look normal.  How did you get into this thread?

fsimms

Re: Sensitivity Ratings
« Reply #73 on: 29 Jan 2009, 04:00 am »
Quote
I designed my speakers cabinets with a 1 inch thick steel plate (~40 lbs) to go between the top cabinet (containing the midrange and tweeter) and the woofer cabinet.

That is a killer cabinet.  It looks almost as good as Jim's!

Bob

BrianM

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Re: Sensitivity Ratings
« Reply #74 on: 29 Jan 2009, 01:20 pm »
P.S.  Note that adding mass properly is not always a bad idea.  Years ago at the home of a group of audiophiles in Barbados, I was given an interesting A-B test of this idea with a big set of bookshelf speakers. The owner had made up a set of very heavy (about 40 pounds as I remember) concrete plates the size of the speaker tops.  They were Naugahyde padded to avoid scratching the speakers and to provide a good contact.  The difference between the speakers with the pads on top and with them removed was very obvious.  Probably Newton's laws of motion at work again. You could here the sound change with your eyes closed as the were placed and removed during play.

I wonder how much (if any) it had to do with a not very rigid or well-damped cabinet in the first place. But yeah, something easy to try out.

avahifi

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Re: Sensitivity Ratings
« Reply #75 on: 29 Jan 2009, 03:11 pm »
Those Barbados audiophiles were real speaker fanatics.  One had exact copy of the old B&W DM6 cabinets done in cast concrete built into the walls of his sound room with all the original drivers installed per stock.  Another had "unfolded bass horns" - -  about 30 feet long or so - - - of cast concrete extending way out into his back yard with the big old KEF rectangular woofers at the far ends and openings the size of picture windows into his living room walls.  :o  Talk about good bass performance!

I don't remember the bookshelf speakers the fellow was using, but they were heavy and were sitting on concrete pedestals, again cast directly into his concrete floor as I remember.

They are a fun group to visit.  I brought a power amp with me on the trip, ordered by one of them.  I was on a cruise that called there.  Since he worked for their Customs office, there was no problem just carrying the amp right through the gates with him.  Personal delivery.  :D

I even had one client fly his seaplane in from a different island for a visit  He had actually lost one of my amps when a hurricane took out the customs house on his island before the amplifier could be delivered to him.  The airline covered it, they could not prove it had been delivered, all the paperwork was blown away too.

Regards,

Frank Van Alstine

Zheeeem

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Re: Sensitivity Ratings
« Reply #76 on: 29 Jan 2009, 05:07 pm »

Can you post some pictures of that, just so I can see something I have never seen before.  Espically interested in the rack, that sounds kind of neat.

Rahimlee54

Ah.  I would have, but the batteries were dead in my digital camera.  I'll try to do this over the weekend, post 'em on the appropriate forum, and PM you when posted.

TomW16

Re: Sensitivity Ratings
« Reply #77 on: 30 Jan 2009, 02:22 am »
Good heavens.  You look normal.  How did you get into this thread?

I can't be that normal, I put a steel plate in my speaker  :wink:

Quote
Quote
I designed my speakers cabinets with a 1 inch thick steel plate (~40 lbs) to go between the top cabinet (containing the midrange and tweeter) and the woofer cabinet.

That is a killer cabinet.  It looks almost as good as Jim's!

Bob

Thanks Bob.  I haven't seen Jim's cabinets in person but from the pictures and the rave reviews, I believe that Jim's cabinets are a notch above mine.   I'm not the most patient person so I went with automotive primer, paint and clear coat since you can put many coats on in a day.  Jim hand rubs his finishes out with curing time between.  The pictures of Jim's speakers look stunning and I understand that the pictures don't do them justice.

Cheers,
Tom

Big Red Machine

Re: Sensitivity Ratings
« Reply #78 on: 31 Jan 2009, 10:50 pm »
Now the whole time I'm wrapping green clay around this midrange frame I'm thinking this is the sickest joke Frank has ever played on us.  Who is gullible enough to try this, photograph it, and then tell about it!! Oh the shame!  Oh the horror!!

DAMNED IF THERE WASN"T A DIFFERENCE _ IMMEDIATELY!!


Luckily I had my 12 year old with me (he was bored and has been shadowing me - trying to irk me into giving him his Xbox controllers - it worked).  He heard it as well.

I put clay on one speaker and then we ran the balance back and forth side to side to see if we heard anything.  Sure enough, the clay speaker wasn't as bright as the other.  So is bright bad or good?  Is quieter bad or good?  I wasn't sure.  I put him in the sweetspot and he said it was brighter (non-clayed speaker).

So okay, I'll modify the left one now.  Yep, it quieted down as well (less bright).  It might be that the brightness was actually some sibilance now tamed.

So now I'm doing some listening to see if I actually like the "new" sound.

Jury's still out.  But there is an impact.  Damn Frank! :bowdown:

Thanks very much for running the tests Dennis.

I can assure you that plastic modeling clay (available in 5 pound bricks at art stores) will not ever come loose or fall off of the speaker metal parts if properly installed in the first place. You can actually carefully heat it up in a microwave oven to make it very soft and workable.

We have used this on the little Biro L/1 speakers we built for Mithat Konar for years without ever a field problem.

The test I ran at B&W in Worthing, England years ago was a true double blind test.  John Bowers gave me a matched set of their little CM-1 bookshelf speakers to play with in their lab.  I had brought a half pound of plasticlay along with me when invited to a factory visit.  I pulled the driver assembly from one and damped it thoroughly and then put it back together very privately.  Since they had identical cabinets and no serial numbers yet, not even I could tell which one I had worked on.

We set them side by side in their sound room and A-Bd them with mono material using the balance control of the drive preamp to switch from one to the other.

The whole tour group got to listen.  I asked everyone to write down the answer to two questions.  First, can you hear any difference?  Second is it a better worse difference and which one do you like better?  After everone voted, I opened up one of the speakers again.

The results, much to B&W's surprise, was that the damped speaker was by far preferred by nearly everyone.

Again Dennis and or Jim, I urge you to try this on the midrange basket of a HT3 or Songtower.  It is a very easy and inexpensive way to build a better speaker.  The sonic result can most accurately be described as having stuff that was obvioulsy not supposed to be there go away, leaving more of the music, less garbage, and better sound.

Best regards,

Frank Van Alstine

P.S. DO NOT TRY THIS WITH PLAYDO.  THAT IS A FLOUR WATER PASTE AND SETS UP LIKE A ROCK AND IS USELESS FOR THIS PURPOSE.

The scientific principal behind this proceedure is simple.  Meatballs don't bounce.  :)

Biscuit

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Re: Sensitivity Ratings
« Reply #79 on: 31 Jan 2009, 11:03 pm »
Good heavens.  You look normal.  How did you get into this thread?

I can't be that normal, I put a steel plate in my speaker  :wink:

Quote
Quote
I designed my speakers cabinets with a 1 inch thick steel plate (~40 lbs) to go between the top cabinet (containing the midrange and tweeter) and the woofer cabinet.

That is a killer cabinet.  It looks almost as good as Jim's!

Bob

Thanks Bob.  I haven't seen Jim's cabinets in person but from the pictures and the rave reviews, I believe that Jim's cabinets are a notch above mine.   I'm not the most patient person so I went with automotive primer, paint and clear coat since you can put many coats on in a day.  Jim hand rubs his finishes out with curing time between.  The pictures of Jim's speakers look stunning and I understand that the pictures don't do them justice.

Cheers,
Tom

Where did you get the steel plates?  I've been thinking about this or just getting thick marble or granite plates cut and doing the same thing with my speakers.  I know where to get the granite but not steel.  That's a good idea!