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Perforated Steel - Acoustic Transparency?

9786 Views 11 Replies 6 Participants Last post by [omen], May 28, 2007

[omen]

Discussion Starter · May 24, 2007

I'm building my own AV cabinet and want to use perforated steel inserts in the doors. This would allow IR signal passthrough and still keep the gear well-ventilated. The thing is, the cabinet is also designed to hold my center channel speaker and I'm now starting to wonder how much high frequency cut-off I'm going to experience by using perforated steel.

I was planning on removing the speaker grille that came with my CC (which is cloth) and adjusting the receiver to compensate for a possible loss in level, but now I'm wondering if that's going to be enough. I'm thinking I might lose a lot in the high-frequency range, more than I'd be able to compensate for with my AVR.

Ideally, I would switch the center door panel to cloth and not even worry about it, but for reasons of aesthetics and durability want to keep all door panels as perforated steel.

I know Salamander and Studiotech both use perforated steel in their cabinets - which are also often meant to house center channel speakers - I'm just not sure how acoustically transparent they are. Can any Salamander or Studiotech owners out there who use their cabinets to house the CC tell me how it sounds? Do you experience any high-frequency loss? Barring that, do any of you guys who have used perforated steel in your own cabinets/installations have any first experience as to how it sounds when you have a speaker behind it?

Thanks!

By the way, here are the specs on type of perf steel I want to use (as best I can tell, this is the exact same type perf steel used by both Salamander and Studiotech):

Product Type : Round Hole

Major Material : Plain Steel

Gauge (Thickness) : 20

Hole Size : 1/8"

Hole Centers : 3/16"

Hole Pattern : Staggered

% Open Area : 40%

http://www.mcnichols.com/eCommerce/s...ber=1618312038

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LuncHwagon

· #2 · May 24, 2007

big difference in sound. I would stick with cloth.

FYI: The bigger the holes, the better the sound.

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[omen]

Discussion Starter · #3 · May 24, 2007

Quote:
Originally Posted by LuncHwagon /forum/post/0

big difference in sound. I would stick with cloth.

FYI: The bigger the holes, the better the sound.

Have you used perf steel in the past? What kind/how big of a difference are we talking?

LA AudioFile, when reviewing Studiotech's U-22T cabinet (which uses the same kind of perforated steel I'm considering), spoke very highly of it:

"The perforated front screen is designed to allow IR commands to pass through and we verified that it does indeed work... As you can see from the photo, our M&K S150THX center channel fit nicely in the center of the cabinet. The acoustically transparent cover on the doors worked well with this configuration." [Bolding is my emphasis.]

http://www.laaudiofile.com/u22t.html

I really don't want to go with cloth. I can see it getting torn or ripped and dusty. If the perf steel really is a problem I'll have to reconsider it, but according to these guys it didn't seem like a problem acoustically. Any thoughts?

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trekguy

· #4 · May 25, 2007

Many automotive speakers, even very expensive ones are behind perforated grills.

For home use a/d/s speakers, for many years, had perforated metal grills. I own several pairs and allowing for the fact that my hearing >15 k Hz ain't what it was, have always liked the sound with the grills in place. The balance changes with the grills off, but not by so much as to make it a critical issue.

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speco2003

· #5 · May 25, 2007

Quote:
Originally Posted by LuncHwagon /forum/post/0

big difference in sound. I would stick with cloth.

FYI: The bigger the holes, the better the sound.

Not true in the least on all points. Sorry but you dont know what your talking about. This man http://www.smwinc.com/about/dennis_paoletti.html

has done alot of halls I have worked. I know him and he has great charts showing the properties of all sorts of things used for grills. Metal is not bad and bigger holes do not equal better sound.

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Chu Gai

· #6 · May 25, 2007

Whether you notice the difference or readily adapt to it is a matter to be determined. Manufacturers and reviewers say all sorts of things that aren't grounded in anything more than selling their product.

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[omen]

Discussion Starter · #7 · May 25, 2007

Thanks for the replies, guys.

Quote:
Originally Posted by trekguy /forum/post/0

Many automotive speakers, even very expensive ones are behind perforated grills.

For home use a/d/s speakers, for many years, had perforated metal grills. I own several pairs and allowing for the fact that my hearing >15 k Hz ain't what it was, have always liked the sound with the grills in place. The balance changes with the grills off, but not by so much as to make it a critical issue.

Yeah, all the a/d/s speakers say they come with "acoustically transparent perforated steel" and by the looks of the grilles they don't appear to have a higher percentage of open space than the one I referenced above, which has 40% open space.

Quote:
Originally Posted by speco2003 /forum/post/0

...Metal is not bad and bigger holes do not equal better sound.

Quote:
Originally Posted by Chu Gai /forum/post/0

Whether you notice the difference or readily adapt to it is a matter to be determined. Manufacturers and reviewers say all sorts of things that aren't grounded in anything more than selling their product.

I started a similar thread in the Speakers forum and got some interesting replies from Kal Rubinson, Contributing Editor at Stereophile Magazine. He noted that anything in front of the driver is going to alter the sound (as well as placing the speaker in a cabinet) and recommended I rethink the design. While I'm sure this is true, I really want to know how much these obstacles (the cabinetry, the grille) affect it.

Here's the thread if you guys want to see what he had to say:

http://www.avsforum.com/avs-vb/showthread.php?t=852063

I can understand Audiophiles being purists - hence the usual removal of any grille and the display of the speaker itself - and how that could lead one to question their opinion, but the last thing I would want to do - after spending months designing this cabinet - would be to cripple the performance of my system.

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Kal Rubinson

· #8 · May 25, 2007

Quote:
Originally Posted by [omen] /forum/post/0

I started a similar thread in the Speakers forum and got some interesting replies from Kal Rubinson, Contributing Editor at Stereophile Magazine. He noted that anything in front of the driver is going to alter the sound (as well as placing the speaker in a cabinet) and recommended I rethink the design. While I'm sure this is true, I really want to know how much these obstacles (the cabinetry, the grille) affect it.

All the statements about the relative characteristics of steel, fabric, etc. aside, the effect that they have on the transmitted sound is generally considered by manufacturers designing speakers with grills and, I assume, by hall designers as well. Take off the grille of almost any speaker, for example, and it will sound different. The Paradigm Reference 60s that I have in one system were 'voiced' for use with the grilles on and removing them results in a much less flat FR.

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[omen]

Discussion Starter · #9 · May 25, 2007

Thanks again for your input, Kal. Yes, my Paradigm mini monitors all come with cloth grilles, and hence (I'm sure) weren't designed to be used with any other kind of grille. Which is the main point, it seems.

I started looking into using speaker cloth for the inserts of my doors last night. It's a heck of a lot cheaper, maintains ventilation and IR passthrough and - if I can match it closely enough to my Paradigm cloth - should be very close acoustically (I hope). Also, taking into account your notes about early reflections that could be caused by the cabinetry itself, I've modified the design to move the speaker shelf forward so it is virtually flush with the door (and the cloth grille) when closed. In reality this leaves about 1/4" clearance between the front of the speaker and cloth since it will be recessed in the door slightly.

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Kal Rubinson

· #10 · May 25, 2007

Sounds like progress.

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speco2003

· #11 · May 26, 2007

Quote:
Originally Posted by Kal Rubinson /forum/post/0

All the statements about the relative characteristics of steel, fabric, etc. aside, the effect that they have on the transmitted sound is generally considered by manufacturers designing speakers with grills and, I assume, by hall designers as well. Take off the grille of almost any speaker, for example, and it will sound different. The Paradigm Reference 60s that I have in one system were 'voiced' for use with the grilles on and removing them results in a much less flat FR.

This is true. I wanted to point out to the one fellow that there are indeed programs for design of grills. I don't have any but have seen the acousticians use them.

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[omen]

Discussion Starter · #12 · May 28, 2007

OK, a couple more questions...

I'm researching grille cloths and I'm reading a lot about Guilford of Maine (GOM) Fabric. It appears this stuff is sturdier, fire retardent and apparently acoustically transparent. Any of you guys think I should use GOM in this application or would that be overkill / inappropriate? Is flame retardation necessary here? Again, the cabinet will not only be housing my center channel speaker, but also the rest of my AV gear (all well ventilated and power managed, mind you). If GOM is inappropriate, but fire retardation is a must, are fire retardent speaker cloths like Acoustone:

http://www.acousticalsolutions.com/p...ille_cloth.asp

...as acoustically transparent as regular speaker cloth, like this one:

http://www.partsexpress.com/pe/pshow...44&rak=260-335

?

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