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What do you guys/gals think of PVC for FR enclosure?
What do you guys/gals think of PVC for FR enclosure?
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Old 4th November 2017, 01:05 AM   #41
Dr1v3n is offline Dr1v3n  United States
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Originally Posted by planet10 View Post
The fiberglass converts the sound energy into heat thus dissipating it...

dave
I guess my real question is why fiberglass converts soundwaves into heat and a common filler like 'acousti-stuf' or 'poly-fill' doesn't.
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Old 4th November 2017, 01:08 AM   #42
planet10 is offline planet10  Canada
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What do you guys/gals think of PVC for FR enclosure?
But 'acousti-stuf' or 'poly-fill’ do convert sound energy to heat. They work the same way.

dave
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Old 4th November 2017, 02:27 AM   #43
luigi is offline luigi  New Zealand
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Default FR driver and PVC tubing

Trying not to hijack thread here. But it's relevant. FR driver and pvc tubing.
I'm planning on trying to produce a BIB using pvc tubing with divider in the middle and ff125wk driver.
I realise the dimensions won't be narrow and deep like a regular BIB and the mouth up top won't expand either but if volume is right acc to the calculator could it still work okay?
I'm using pvc as I have no woodwork skills apart from being able to rout circles.
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Old 4th November 2017, 11:19 PM   #44
Zarathu is offline Zarathu  United States
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Originally Posted by planet10 View Post
But 'acousti-stuf' or 'poly-fillí do convert sound energy to heat. They work the same way.

dave
Just not near as efficiently, according to research in Vance Dickersonís THE LOUDSPEAKER COOKBOOK, 6th edition, page 101.

And since fiberglass insulation is far cheaper, why use something more expensive that does the job less well?
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Old 4th November 2017, 11:21 PM   #45
planet10 is offline planet10  Canada
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What do you guys/gals think of PVC for FR enclosure?
Quote:
Just not near as efficiently
Maybe.

dave
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Old 4th November 2017, 11:28 PM   #46
Zarathu is offline Zarathu  United States
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Originally Posted by Dr1v3n View Post
Zarathu, thx a mil for posting. A couple questions I have out of curiousity, since I'm experimenting out of my realm....

1) Would there be any value to mixing square enclosures amongst the tubes so one gets a mix of even and odd harmonics?
If the purpose is to reduce harmonic back flow through the speakers why would you want to increase it? And why would you want to increase the one which doesnít bring clarity to the music?

Quote:
Originally Posted by Dr1v3n View Post
2) Why does the fiberglass heat up from the sound waves in your opinion? And at what SPL levels?
Dickersonís research is a long long article. I have no idea, why fiberglass is more effective. Im sure there is something in the physical properties of fiberglass material, but Iím not a physical chemist, so I have no idea.

In my line arrays, I have to really push them, and since each speaker only produces 1/17(5.8%) of the total sound of the array per channel in the mid range, the SPL is negligible. Suppose they are producing 75 db. This means that each speaker is only producing 4.5 db, which is lower than a whisper.

The warmth I feel is after a few hours of use as the total sound collects.

I suggest you purchase the book.

Most people just use very heavy boxes; you probably should too.
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Old 4th November 2017, 11:29 PM   #47
Zarathu is offline Zarathu  United States
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Originally Posted by planet10 View Post
Maybe.

dave
You need to argue with Vance Dickersonís research, not with me. Iím only reporting it.
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Old 5th November 2017, 09:19 AM   #48
wesayso is online now wesayso  Netherlands
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Be sure to look into some claims made here a little deeper. On audibility of harmonic distortion personally I'd avoid third order even if it has been said to enhance perception of detail in some cases. One should realize that the detail which is perceived isn't real. Not something I'd want in any form or way. It probably won't work out that well on all types of music either.

Boominess often is a frequency response problem. Arraying more and more drivers will change overall frequency response. Room modes can play a role too. Don't guess, measure!

If anything, most people would prefer 2nd order harmonics over 3rd. They tend to sound more musical. At least that's what I've been able to find in most studies on this subject. I'm not saying you should want any of them in any large quantities though.

Fiberglass certainly is an affordable sound absorber that works over a wide frequency range. Perfect for use in sealed enclosures, not as much for ported ones as you shouldn't want those fibres flying freely.

To see the effectiveness of any damping material in your enclosures compare the impedance curve of the speaker within the enclosure to a free air curve.
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Old 5th November 2017, 12:03 PM   #49
Dr1v3n is offline Dr1v3n  United States
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Originally Posted by wesayso View Post
Be sure to look into some claims made here a little deeper. On audibility of harmonic distortion personally I'd avoid third order even if it has been said to enhance perception of detail in some cases. One should realize that the detail which is perceived isn't real. Not something I'd want in any form or way. It probably won't work out that well on all types of music either....
I intend to and I see Vance Dickason's book is now up to the 7th Edition.

But before I can do that, it's onward with the construction. Today, I'm headed into work to make PVC dust. I have to shave off 20 PVC encaps flat to mount the P7's. I also am going to try to paint 4 of the mounts gloss black using Krylon Fusion spray paint. Then a few coats of Krylon Fusion Clear. Maybe I'll paint 1 tube as well, just for a pic I'll post later today.

I received the last 4 P7's from Madisound yesterday, but forgot to order the binding posts! I'll have to rush ship them...

The remaining 20 magnets should be here tomorrow...

This Wednesday, I should have a first listen to 12 P7's per side.
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Old 5th November 2017, 12:25 PM   #50
Zarathu is offline Zarathu  United States
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Originally Posted by wesayso View Post
Be sure to look into some claims made here a little deeper. On audibility of harmonic distortion personally I'd avoid third order even if it has been said to enhance perception of detail in some cases.
In a line array there isnít any distortion, so we are not talking about harmonic distortion in the back wave of sound. Even if I run my speakers at 120 db, each mid range speaker is only asked to put out 6 db of that, and so there is no harmonic distortion in the back wave at all. Additionally, the amount of harmonics that come through is small after being absorbed by the fiberglass.

So we are only talking about the small amount of harmonics 180 degree out of phase which comes back through the speaker cone and muddies the sound. You wonít actually hear it due to the Haas effect since it will be only a couple of millisec after the original sound, but it will be perceived as a muddying effect.

And even order harmonics bring a bigness to the sound, whereas 3rd order brings clarity and timbre. If you use tubes as your cabinet, then you wonít have any even order harmonics coming back through the wave since the physics of sound in a closed tube simply doesnít allow even order harmonics to be produced. So the back wave consists entirely of the original sound 180 degree out of phase and odd order harmonics. But remember since the line array is not producing distorted harmonics, its only the natural harmonics of the music itself.

You have to understand the physics of what is happening here and not get confused with thinking we are talking about harmonic distortion or not understanding the physics of sound.
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