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Foam or rockwoll in la scala


SpeedLimit

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I asked Roy about this once.  If I can butcher his comment it was essentially "if a speaker needs foam, we put it in, if it doesn't, we don't"

 

The original LaScala didn't have it yet apparently the newer versions do.  Interesting.

 

 

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On 3/13/2022 at 1:02 AM, Coytee said:

I asked Roy about this once.  If I can butcher his comment it was essentially "if a speaker needs foam, we put it in, if it doesn't, we don't"

 

The original LaScala didn't have it yet apparently the newer versions do.  Interesting.

 

 

 

I assume that Roy has listened carefully to the newer Lascala IIs. It's really not the same enclosure material as an old Lascala. The old Lascala has thinner birch plywood and the new Lascala has thicker MDF. Probably the thinner birch plywood has different acoustic properties. It could be that the thicker MDF absorbs standing waves less well and creates other resonances that have to be damped with foam. It's just my guess. But in my view Roy is right, if they have to use foam then they do it. 

Besides Klipsch speakers, I'm also a decades-long fan of thin-walled BBC speakers. Look how much research they used to put into everything in the link below. This white paper is only about research of material types and thickness. They have many white papers like this available for all sorts of questions and developments around their speaker designs that are still valid today. E.g. they measured (and a panel test-listened) that thicker materials can produce more time smear and unclearer mids. Of course, we are talking about mid-sized bass reflex speakers at the BBC, not horns.

 

https://downloads.bbc.co.uk/rd/pubs/reports/1977-03.pdf

 

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On 3/12/2022 at 7:02 PM, Coytee said:

I asked Roy about this once.  If I can butcher his comment it was essentially "if a speaker needs foam, we put it in, if it doesn't, we don't"

 

The original LaScala didn't have it yet apparently the newer versions do.  Interesting.

 

 

It is funny how ideas and perceptions change isn't it?

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34 minutes ago, KT88 said:

It could be that the thicker MDF absorbs standing waves less well and creates other resonances that have to be damped with foam. It's just my guess. 

I don't think MDF or any type of wood is absorbing reflected sound waves. The sound waves will bounce around and eventually make it outside of the speaker enclosure through a speaker cone or by vibrating a panel (in other words; bounce around until they are attenuated so low they are not effecting anything). 

 

Absorbtion and attenuation are totally different things. 

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14 hours ago, Curious_George said:

Every HiFi speaker I have even taken apart or looked inside (regardless of type: transmission line, sealed, reflex, horn, horn/reflex) had some type absorbtion material inside it to reduce reflected waves, except a Heresy and LaScala. I've never seen inside or taken apart a k-horn.

 

 

 

I was under the impression that absorbent materials, usually Fiberglas batts or something similar, are installed in the cabinets of some speakers to provide "virtual volume".  That is, they make the enclosure act like it has greater volume than it really has.  Whether it does that by absorbing sound waves, I don't know.

 

It may be that the doghouse of a La Scala is the size it's supposed to be, so no absorbent material is required.

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3 hours ago, Islander said:

 

I was under the impression that absorbent materials, usually Fiberglas batts or something similar, are installed in the cabinets of some speakers to provide "virtual volume".  That is, they make the enclosure act like it has greater volume than it really has.  Whether it does that by absorbing sound waves, I don't know.

 

It may be that the doghouse of a La Scala is the size it's supposed to be, so no absorbent material is required.

Absorbent material is used to address two areas; standing waves and to increase box volume. 
 

https://en.wikipedia.org/wiki/Adiabatic_process

 

The increase in box size is plain ole physics, in this case, the laws of thermodynamics. Here is an interesting discussion on the subject: 

 

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55 minutes ago, SpeedLimit said:

Now, i do not know if i will put or not what i have bought to fill my cabinet.

 

In the scala box, the K33E behaves a bit like a compression driver with a horn (sorry for the perhaps false translation), don't you think so ?

the Peavey FH1 is not a Lascala Bass bin, , I would reach out to @ClaudeJ1 or @HPower both Forum Members  have  a lot of experience using the Peavey FH1  , and they can advise you better

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5 hours ago, Islander said:

 

I was under the impression that absorbent materials, usually Fiberglas batts or something similar, are installed in the cabinets of some speakers to provide "virtual volume".  That is, they make the enclosure act like it has greater volume than it really has.  Whether it does that by absorbing sound waves, I don't know.

 

It may be that the doghouse of a La Scala is the size it's supposed to be, so no absorbent material is required.

 

As far as I know, materials such as foam reduce the speed of sound. That is why an enclosure volume becomes virtually larger when foam is added.

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2 hours ago, RandyH said:

the Peavey FH1 is not a Lascala Bass bin, , I would reach out to @ClaudeJ1 or @HPower both Forum Members  have  a lot of experience using the Peavey FH1  , and they can advise you better

The FH-1, the bass horn portion of an SP-1, I used to call a "cheap Scala" since they were so cheap to get 10-20 years ago. They were designed by a couple of former EV engineers, AFAIK. It's a "classic" W bin, short horn, but longer than a LaScala by about 1/2 a foot or so. It's cutoff is about 90 Hz. vs. 104 for a LaScala.

 

The early SP-1's had no braces and Eminence woofers which were burned up by Bands trying to get too much bass out of them below cutoff, so Peavey made their own 4 ohm drivers with 4" voice coils to handle more power. They also added braces, which made it a Very Solid Horn Box! I still have a pair of them.

 

They can still be found at bargain prices, but are becoming rare over time.

 

Either way I have not tested them with any kind of insulation inside the dog house. PWK didn't use it, so I haven't tried. Although the "Golden Jubilees" that Ms. Valerie Klipsch commissioned from the Hope Factory's best builder to follow PWK's drawings of the Jube use foam to fill the back chamber, which is all I know first hand when I looked at and measure the second of only 2 pairs ever made. No factory built bass horn MWM, Khorn, or LaScala ever used any kind of adiabatic insulation in the back chamber, AFAIK. that's reserved for Bass Reflex.

 

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17 hours ago, SpeedLimit said:

Now, i do not know if i will put or not what i have bought to fill my cabinet.

 

In the scala box, the K33E behaves a bit like a compression driver with a horn (sorry for the perhaps false translation), don't you think so ?

 

That's exactly what it's meant to be.  The narrow slot in front of the woofer causes an increase in the speed of the air movement at the throat of the horn, just like a small round compression driver.  Only bigger.

 

As for adding absorbent material to any cabinet, it will change the behaviour of the cabinet, which has been carefully designed to operate the way it leaves the factory.  Changing the apparent/virtual volume of the cabinet will mess up the way the cabinet operates.  It's very unlikely to make an improvement, but is very likely to make the speaker sound worse than stock.

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16 hours ago, KT88 said:

 

As far as I know, materials such as foam reduce the speed of sound. That is why an enclosure volume becomes virtually larger when foam is added.

 

AFAIK, the speed of sound only changes when the air density or temperature changes.

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4 minutes ago, Islander said:

 

That's exactly what it's meant to be.  The narrow slot in front of the woofer causes an increase in the speed of the air movement at the throat of the horn, just like a small round compression driver.  Only bigger.

 

As for adding absorbent material to any cabinet, it will change the behaviour of the cabinet, which has been carefully designed to operate the way it leaves the factory.  Changing the apparent/virtual volume of the cabinet will mess up the way the cabinet operates.  It's very unlikely to make an improvement, but is very likely to make the speaker sound worse than stock.

you convinced me, I'm not changing anything.

And i do not know if in the original FH1, there is any foam inside.

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On 3/15/2022 at 12:19 PM, KT88 said:

 

I assume that Roy has listened carefully to the newer Lascala IIs. It's really not the same enclosure material as an old Lascala. The old Lascala has thinner birch plywood and the new Lascala has thicker MDF. Probably the thinner birch plywood has different acoustic properties. It could be that the thicker MDF absorbs standing waves less well and creates other resonances that have to be damped with foam. It's just my guess. But in my view Roy is right, if they have to use foam then they do it. 

Besides Klipsch speakers, I'm also a decades-long fan of thin-walled BBC speakers. Look how much research they used to put into everything in the link below. This white paper is only about research of material types and thickness. They have many white papers like this available for all sorts of questions and developments around their speaker designs that are still valid today. E.g. they measured (and a panel test-listened) that thicker materials can produce more time smear and unclearer mids. Of course, we are talking about mid-sized bass reflex speakers at the BBC, not horns.

 

https://downloads.bbc.co.uk/rd/pubs/reports/1977-03.pdf

 

 

During the development of the La Scala II, Klipsch (Roy?) built two pairs of prototypes, one pair made of 1" MDF and one pair made of 1" plywood.  During listening tests, they found that they preferred the sound of the MDF cabinets, so that's what the production speakers are made of.  The plywood prototypes were sold to a Forum member years ago (the LS2 came out in 2006), and he was very happy with the sound.  This suggests to me that every listening room and every listener is different.  The engineers can't make speakers that please everyone.  They do their best to make speakers that most fans of that type of speaker will be very happy to have, and hopefully at least some fans of other types of speakers will also like them enough to buy them.

 

Harbeth seems to use the same logic as the BBC, in that their cabinets are also thin-walled, and some models are fairly large.

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7 hours ago, Islander said:

 

During the development of the La Scala II, Klipsch (Roy?) built two pairs of prototypes, one pair made of 1" MDF and one pair made of 1" plywood.  During listening tests, they found that they preferred the sound of the MDF cabinets, so that's what the production speakers are made of.  The plywood prototypes were sold to a Forum member years ago (the LS2 came out in 2006), and he was very happy with the sound.  This suggests to me that every listening room and every listener is different.  The engineers can't make speakers that please everyone.  They do their best to make speakers that most fans of that type of speaker will be very happy to have, and hopefully at least some fans of other types of speakers will also like them enough to buy them.

 

Harbeth seems to use the same logic as the BBC, in that their cabinets are also thin-walled, and some models are fairly large.

 

Yes, that‘s because H.D. Harwood was part of the BBC development team like Spencer Hughes who founded Spendor.

 

https://harbeth.co.uk/harbeth-about-us-page-1/

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Guys, DO NOT overstuff the dog house with foam, polyfill, pillows!!!! IT WILL KILL YOUR SOUND.

Believe me, I've been there: I covered the entire doghouse panels with eggs crate foam and it was like the woofer was stuck.

A raw doghouse is part of the design and how the horn works.

 

If you insist on doing it, you can place just ONE piece of foam covering the triangular horizontal panel, above the woofer, it will kill some little resonance, but THAT'S IT. 

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I have not seen the inside of the latest La Scala's but I will say this. If Roy is putting foam in there it is part of a whole system approach and another piece of the puzzle that includes cabinet, drivers and crossovers designed to work together. Putting foam in older LS's may or may not do the same thing. One thing that will work with all pre 1" sides is the dog house bracing. Of all potential modifications this one has the biggest return for the money spent BY FAR. You might not like the look but you will like the sound. I never let a set go from here without doing something about the side wall resonance. These will also reduce dog house resonance at the same time. I was going to say stop the resonance but there will always be some. It makes a dramatic improvement and there is a picture floating around the forum of PK doing just that. I would love to know why they were never incorporated into the design by him.

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