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Old 23rd February 2010, 02:30 AM   #11
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thanks Dave! that makes sense about the increased cross section in the begining acting as a high pass filter, same as increasing the chamber in a BLH. From your advice I think I will alter what I drew in the previous post in two ways. Slightly lengthening the "tail" although I don't think I can go a full 1/4 length as I think the fs is some where in the 70's, a little too long there. But I'll certainly lengthen in from what I drew. I'll also shorten the stand some. I was thinking putting it up higher on the stand like that would help reduce diffraction even more by putting it farther away from any other objects. Maybe I'll still keep the Tang band's stand a little taller. Certainly not the fostex's stand though, it just doesn't seem to have the excursion to go any lower than 300Hz with out some kind of horn loading.
As far as the Midwest goes, I always consider it more of a band east to west.... Maybe the Dakotas to Illinois? Probably some grey area there....
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I mentioned wanting to eventually build a high effeciency three way... my only reservation on the Audax PR0170m0 is that I've heard it's not well suited for horn use. It would be fun to compare a driver on both a front loaded horn and a ceramic enclosure.... hmmm maybe I could try that with the fostex? Anyways if and when I do build a front horn I'll probably use a method similar to this. I don't think ceramic horns would be a great idea for two reasons, one I could be wrong, but I feel like the horn shape would be more prone to ringing at the mouth of the horn. Also with my midrange enclosures if I end up being a half and inch off here or there... ehh, no biggie as long as I get the curves consistent, keep the baffle area flat, and have two that match. However even a quarter of an inch off inside the throat of a horn would be pretty bad.
A little off topic do you recall whose large wood fired kiln you saw? We fire all our pots in a large outdoor wood kiln, not all that common anymore.
Joe
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Old 23rd February 2010, 06:45 AM   #12
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Originally Posted by planet10 View Post
A baffle is the weakest panel in the box because of the big hole...
dave
Very true

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and MDF won't reliably hold a screw.
dave
Very mistaken. It will provided you drill the right sized pilot hole and use vaseline on screw threads to lubricate as you tighten it, and of course use the large threaded 'chipboard' type screws.
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Old 24th February 2010, 06:05 PM   #13
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Well after thinking about it, I think the tangband and fostex will go in different enclosures. The tangbands are being used as computer speakers so space is somewhat limited. The fostex on the other hand are in the living room, and have a little more space. I've attached a picture of what I think I will make. The short one on the stand will be the tangband. The only question I have here is with it being so short, can I still stick with the aperiodic loading or would I be better off making it sealed. I'm not too concerned with bass performance, as this is just for the computer, and is running off of an unmodified sonic impact (so there's no bass either way). The fostex I'm going to stick with the original plan except for removing the stand to get the fostex closer to the 12" driver, for better integration. I don't think I can do a full 1/4 wavelength aperiodic transmission line, hopefully somewhere between 18-24" will suffice.
Anything thoughts or suggestions?
Joe
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Old 24th February 2010, 06:27 PM   #14
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Hi Joe.
Have a look at this thread and scroll down to posts 17 & 19
porcelain enclosure speakers
You should hear Toccata and Fugue on these!
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Old 25th February 2010, 01:55 AM   #15
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Originally Posted by Josephjcole View Post
The only question I have here is with it being so short, can I still stick with the aperiodic loading or would I be better off making it sealed. I'm not too concerned with bass performance, as this is just for the computer, and is running off of an unmodified sonic impact (so there's no bass either way). The fostex I'm going to stick with the original plan except for removing the stand to get the fostex closer to the 12" driver, for better integration. I don't think I can do a full 1/4 wavelength aperiodic transmission line, hopefully somewhere between 18-24" will suffice.
Anything thoughts or suggestions?
The box doesn't need to be 1/4 wl long to make it aperiodic, and in a TL, the steeper the taper the shorter the line should be.

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Old 25th February 2010, 02:42 AM   #16
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A quick survey of speakers built commercially and by knowledgeable DIYers over the last decade or two will show that there is nothing resembling a consensus supporting the rejection of MDF as a cabinet material. I'm not suggesting you reject that advice out of hand, but I wouldn't recommend blindly accepting it either. Instead, it might be best to sample the advice from multiple sources before drawing your conclusions.

Have you considered damping the ceramic enclosure's walls' vibrations if they turn out to be a problem?

Finally, this might be of no use at all, but I'd be tempted to experiment with something like this material. You could pour it so that it molds perfectly to the driver and the ceramic enclosure. Its stiffness might mate well with your ceramic enclosure walls.

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Old 25th February 2010, 03:46 AM   #17
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A quick survey of speakers built commercially and by knowledgeable DIYers over the last decade or two will show that there is nothing resembling a consensus supporting the rejection of MDF as a cabinet material.
And roaches outnumber humans... IMO MDF as a "quality" loudspeaker building material is the most successful snake oil perpetrated on hifi lovers ever

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Old 25th February 2010, 05:58 AM   #18
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And roaches outnumber humans... IMO MDF as a "quality" loudspeaker building material is the most successful snake oil perpetrated on hifi lovers ever

dave
LOL no that would be acrylic paint blobs on my driver.....

seriously though. Ply IS better, but MDF isnt really any worse than chipboard, which was used for years, or for that matter 'solid' wood. many people still advocate real wood use where it makes no sense, ie pine TL's, which would probably be the least solid boxes i can think of.

Its a matter of degrees. 19mm ply, 25mm MDF, or 6mm steel, are similar equivalents. Since birch ply is denser, but stiffer than MDF its advantages are slightly counteracted. similarly, MDF although slightly less dense needs a larger thickness to match ply, and i do believe that a thickness 133% that of ply yields equal to slightly higher stiffness. steel of 6 mm thickness is probably stronger than either material.

The main problem is internal damping.

steel is the worse,
then PLly next,
followed by MDF

since most MDF is about 0.75-0.8 times as dense as good BB ply, applying 130% thickness to an equivalent MDF panel, would yield simliar weights, stiffnesses, and as such resonant frequencies. ONLY the damping internal to the material would determine Q of peaks and distribution of resonances harmonically above the fundamental.

IN short, ceramic would ring like hell, unless a suitable damping method was found, much like a steel cabinet would.

As if you didnt know that already lol
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Old 25th February 2010, 06:33 AM   #19
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LOL no that would be acrylic paint blobs on my driver.....
Don't judge till you have been experienced... besides most people still believe those measels are snale oil, and as the largest vendor of same i can assure you not successfully perpatrated (certianly be careful if you get to Owston, some people there seriously pleased with their spotted drivers)

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MDF isnt really any worse than chipboard
MDF is easier to finish and work, but not as good.

Quote:
for that matter 'solid' wood
In the hands of someone who knows how to keep it from "exploding" when the weather changes it can be very special.

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19mm ply, 25mm MDF, or 6mm steel, are similar equivalents
But MDF has higher energy storage... creating a continual ooze of low level time smeared grunge that kills the downward dynamic range.

Quote:
steel is the worse,
then PLly next,
followed by MDF
Because of all the layers and the impedance changes across the boundaries, plywood is better damped than MDF. Because MDF is homogonous its resonances have lower Q which makes them more audible.

Quote:
IN short, ceramic would ring like hell, unless a suitable damping method was found, much like a steel cabinet would.
But if you can get the resonance up high enuff, and the Q of the resonance high enuff, it will never get excited and it will be as if it has no ring at all.

dave
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Old 25th February 2010, 12:10 PM   #20
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Joe, you might find these interesting:

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