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Old 1st February 2009, 04:20 AM   #1
ro9397 is offline ro9397  United States
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Default Substitute for Ovangkol enclosure panels?

What less costly panel material might approximate that of solid Ovangkol? Ovangkol is the wood employed in a monitor being cloned. “Less costly” is compared to the Ovangkol at $17/linear foot.

OEM monitor description: internal volume .45cf/800ci. One 17cm midbass & one 28mm dome tweeter, f3 mid-high 40 Hz range, xo estimate 2.2kHz, about 87 dB sensitivity.

Description of enclosure panels of OEM monitor being cloned: HWD 14.5 x 9.5 x 11-5/8". Top/base 30mm solid Ovangkol, sides 34mm solid Ovangkol, baffle/rear panel 22mm MDF laminate.

Subs will normally be employed w/ mains HP crossed @ 80 Hz & their port tightly stuffed w/ foam. But still desire to approximate as closely as possible the OEM performance, especially at rare times when the mains may run fullrange w/ reflex port open & no subs. Curb weight 28 lbs ready to play music. Sum total internal damping is high-density convoluted foam about 1” from flat to peak.

FYI Ovangkol is an African tonewood employed by Taylor & other luthiers as a less costly substitute for rosewood. I am a good flat top acoustic guitarist w/ good knowledge of tonewoods employed in the world’s finest guitars (Klynes in the $20k + range, vintage Martins, Schoenberg, Ryan Thorell who at the tender age of 29 is one of the world's best guitar builders, R Taylor, etc.). To these ears Ovangkol indeed does sound a lot like medium quality Indian rosewood, but appears to have a “flatter” more neutral response. I could, at least academically, see how a player may even prefer the Ovangkol over rosewood for this neutral quality. Ovangkol's more neutral response is consistent w/ the speaker engineer’s choice.

Sorry for the wordiness, but I figured the more information the better. I’m picky, have auditioned some of the best monitors up to about $17k/pair USD MSRP & the monitors being cloned are far & away my favorite. Ovangkol will be employed for some of the speakers being cloned but an alternative is sought for a less critical application.

What are potential acoustic reasons, if any, for the different panel thicknesses, sides vs. top/base (34mm/30mm respectively)? How much performance might be lost if the sides, top & base were all the same thickness, say about 32mm/1.25”?

What if any lower-priced alternative may perform similar to the Ovangkol? What about a laminate such as 1/3rd birch play + 2/3rd veneered MDF or 2/3rd particle board? The baffle/rear panel will be 22mm MDF same as OEM.

Many thanks!
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Old 1st February 2009, 06:21 AM   #2
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I know a bit about tonewoods as I have traded in instruments a lot and have a friend who's a luthier. However a speaker is a reproducer, not a producer of sound like an instrument. You want none of the speaker's character to come through for accurate reproduction.

For a small box like that, Baltic Birch or other quality ply with adequate bracing and solidly constructed will be fine. I would go with better bracing rather than just thicker.

If you're cloning the design, it will be the net internal volume that is important for the driver to work the same as the original (assuming you have the correct drivers and a copy of the xover).
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Old 1st February 2009, 05:17 PM   #3
ro9397 is offline ro9397  United States
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Quote:
Originally posted by Brett
[B]I know a bit about tonewoods as I have traded in instruments a lot and have a friend who's a luthier.
It's great to read the opinions of someone w/ similar experience.

Quote:
However a speaker is a reproducer, not a producer of sound like an instrument. You want none of the speaker's character to come through for accurate reproduction.
The less enclosure output the better is a well accepted & seldom-if-ever-argued design goal. There are some variations of this theme, such as the British architecture where thin ply panels are engineered for a certain amount of flex. BTW, 10-15 years ago Honda engineered something novel called "Tuned Flex" into motorcycle frames; prior to this it was (apparently wrongly) believed that the more rigid the frame the better. Under the most extreme cornering forces a motorcycle frame's rigidity works counter to its ability to track accurately.

It appears true that the enclosure will always contribute something rather than nothing to overall output. The OEM speaker company states the enclosure's "voice" was an integral deisgn element of the overall performance. It's very difficult to argue w/ the resulting product.

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For a small box like that, Baltic Birch or other quality ply with adequate bracing and solidly constructed will be fine. I would go with better bracing rather than just thicker.
Interesting that the OEM designer chose such thick solid Ovangkol w/ NO bracing. Considering the dimensions, do you consider something like one vertical ply window brace placed mid-depth "adequate"? Thickness? What about the fact that the speaker's rocking motion is minimized by its mass, which comes from the thick Ovangkol? I imagine 3/4" BB ply will weigh considerably less than 1/2 the 1.25" Ovangkol. I suppose a metal ballast could be added to the base.
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Old 1st February 2009, 05:37 PM   #4
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Quote:
Originally posted by ro9397
The less enclosure output the better is a well accepted & seldom-if-ever-argued design goal. There are some variations of this theme, such as the British architecture where thin ply panels are engineered for a certain amount of flex. BTW, 10-15 years ago Honda engineered something novel called "Tuned Flex" into motorcycle frames; prior to this it was (apparently wrongly) believed that the more rigid the frame the better. Under the most extreme cornering forces a motorcycle frame's rigidity works counter to its ability to track accurately.

It appears true that the enclosure will always contribute something rather than nothing to overall output. The OEM speaker company states the enclosure's "voice" was an integral deisgn element of the overall performance. It's very difficult to argue w/ the resulting product.



Interesting that the OEM designer chose such thick solid Ovangkol w/ NO bracing. Considering the dimensions, do you consider something like one vertical ply window brace placed mid-depth "adequate"? Thickness? What about the fact that the speaker's rocking motion is minimized by its mass, which comes from the thick Ovangkol? I imagine 3/4" BB ply will weigh considerably less than 1/2 the 1.25" Ovangkol. I suppose a metal ballast could be added to the base.
The Honda frames were designed that way to allow a certain give at the edge of the performance envelope to allow the rider an opportunity to correct before a high side or some other unfortunate incident during a race. I don't find it an appropriate analogy to a speaker enclosure.

I can have no idea why the original designer chose the material in those dimensions. Perhaps he has an unlimited supply of reject Warwick bass bodies to work with. Perhaps it is an artistic flight of fancy: I cannot speculate from here. Have you attempted to ask the designer why?
However, I do not see how you can 'tune' a resonance into a panel and make it consonant with all music all the time. No panel talk = best.

However, what my experience tells me is that quality ply with a Matrix type bracing, well implemented works very well.
Other variations such as composites and other esoteric processes may be even better, but I don't have the facilities to manufacture using them.
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Old 1st February 2009, 07:59 PM   #5
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Quote:
Originally posted by ro9397
The OEM speaker company states the enclosure's "voice" was an integral deisgn element of the overall performance. It's very difficult to argue w/ the resulting product.
Can you tell us what speaker you are trying to clone?

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Old 1st February 2009, 08:58 PM   #6
ro9397 is offline ro9397  United States
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I'd rather not mention the speaker for private reasons. The knowledge is of little use, I know of only one other pair landing in the USA; probably similar scarcity overseas. A Google search will uncover likely suspects (MSRP $6500-$7k/pair USD summer '07).

The company stated their reasons for choosing ovangkol (see above). One should only inquire further if there was reason to doubt their claim. No such reason exists, though one can read above for completely unsubstantiated suggestions & add to them as they see fit. The company does not claim the cosmetic look of the ovangkol was unrelated to choosing it. One generally sees above average looking products in this price class. Cosmetically these exceed all or most of what exists in the class, though that's obviously subjective.

To the extent it appears to be impractical to build our own enclosures w/ zero output there may be value in discussing the idea that certain types of panel output will provide more desirable results than another. Another way to look at this may be: one panel material may have a platue-shaped resonant bump over a wide range where the ear has low-sensitivity & this bump may be easy to work w/ in the xo; another may have several tall irregular-spaced spikes in a high-sensitivity range. Which might be preferred?

I suppose I'm typing myself into this corner: if the Ovangkol is indeed a primary ingredient contributing to the overall performance either Ovangkol at $17/linear ft will be employed or performance will suffer.

Anyone try the laminates mentioned in Aug '08 Stereophile News: 1/3rd BB ply + 2/3rd either veneered MDF or particle board?
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Old 2nd February 2009, 06:02 AM   #7
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Want to send the ovangkol to me and I'll do some tests when the accelerometer arrives.

One should not be so naive as to believe that marketing and something that differentiates a product in a class are often not the dominant reason for a given choice.
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Old 2nd February 2009, 07:40 AM   #8
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Discussion on what materials to build speakers out of

Quote:
Google search will uncover likely suspects (MSRP $6500-$7k/pair
Atelier de Synergie Acoustique would be my guess from your post on Audio Circle.

Click the image to open in full size.

http://web.lerelaisinternet.com/asa....onitor_pro.php

except for 1 dimension (13" instead of 11 5/8") and a couple dB of efficiency jives well with your description

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