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Old 7th November 2007, 05:31 PM   #571
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Quote:
Originally posted by KarlXII
I need to get some advice on stuffing.

I know it's supposed to be well enough to stuff the upper part of the speaker, but how much?
Is it just loosely put in there, or gently compressed?
Or do I in fact get the best results with just cramming and compressing it in there?

Looser in the front and heavier in the back or vice versa?

How did you guys do it?
Uniform density of about 0.35lbs ft^3 of hollow-fibre material in the top 22in of the line should do it.

Just to expand a little on what Dave has already said, one of the assumptions made in BR math is that the (air) particle density in the enclosure is uniform, and there are no standing waves. The latter is why there are so many non-parallel sides seen in BR cabinet designs. (As it happens, I'm of the Linkwitz persuasion in believing that this can cause more problems than it solves, because you are just going to shift the cabinet resonances around and make it harder to work out at what frequency they will occur.)

An MLTL is also a ported box, but it differs from a reflex cabinet in that while the latter tries to avoid generating standing waves, the MLTL deliberately uses them. The air-mass in the restricted terminus (i.e. the vent), resistively loads the QW pulses generated by the main cabinet, helping to damp the unwanted higher harmonic resonances, and dramatically lowering the overall system resonant frequency.
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Old 7th November 2007, 06:12 PM   #572
Byrd is offline Byrd  South Africa
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My build is just around the corner. You know that corner - the one that she'll be coming arounf when she comes! Anyway just got some magnets for mounting the grills when it actually happens.

Now to the question. Has anybody ever done / thought of a coupled cavity MLTL?
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Old 10th November 2007, 05:35 PM   #573
KarlXII is offline KarlXII  Sweden
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Quote:
Originally posted by Scottmoose


Uniform density of about 0.35lbs ft^3 of hollow-fibre material in the top 22in of the line should do it.

Scott,

are you sure about the above figure?
I'm just about to stuff them and was chocked over how little it is.
0,35 pound is 159 grams.
The blueprint says 0,5 pound per ft^3 which is 227 grams.
The actual space to be filled is just a little over a ft^3. A ft^3 is 28 liters and the actual figure is 30 liters.

Ergo: The amount of filling for the Smallthor in the metric system is for 0.35lbs ft^3 = 169 grams. For 0.5lbs ft^3 = 242 grams.

I tried to fluff sheeps wool as much as possible but could not fill the top 22 inches of the line with 169 gram.

Click the image to open in full size.

What to do? Fill it up as fluffy as possible (which will mean appx 300 grams) or get a lower density filling?

Maybe I'm a bit over the top here but I still want to ask what's best..
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Old 10th November 2007, 05:50 PM   #574
KarlXII is offline KarlXII  Sweden
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Here's another pic with the Thor on the stand, which also is a compartment for the XO.
I think it's a good looking speaker. It will be painted soon in a high gloss offwhite-bonewhite color with the stand in high gloss black.

Click the image to open in full size.
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Old 10th November 2007, 11:41 PM   #575
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Quote:
Originally posted by KarlXII
Scott,
are you sure about the above figure?
I'm just about to stuff them and was chocked over how little it is.
0,35 pound is 159 grams.
The blueprint says 0,5 pound per ft^3 which is 227 grams.
The actual space to be filled is just a little over a ft^3. A ft^3 is 28 liters and the actual figure is 30 liters.

Ergo: The amount of filling for the Smallthor in the metric system is for 0.35lbs ft^3 = 169 grams. For 0.5lbs ft^3 = 242 grams.

I tried to fluff sheeps wool as much as possible but could not fill the top 22 inches of the line with 169 gram.
Yes, I'm sure about the above figure.

When I designed the cabinet, I erred on the side of caution. Some time has passed since then, and these days I usually favour a slightly reduced quantity for MLTLs to preserve the microdynamics. More can be added to taste if it's desired after initial listening. Just fluff the material out as much as you can; if your chosen damping doesn't go the full 22in down, so be it. It's not especially critical. All the damping is for is to kill the unwanted higher harmonic resonances.
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Old 11th November 2007, 09:55 AM   #576
KarlXII is offline KarlXII  Sweden
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Quote:
Originally posted by Scottmoose


Yes, I'm sure about the above figure.

When I designed the cabinet, I erred on the side of caution. Some time has passed since then, and these days I usually favour a slightly reduced quantity for MLTLs to preserve the microdynamics. More can be added to taste if it's desired after initial listening. Just fluff the material out as much as you can; if your chosen damping doesn't go the full 22in down, so be it. It's not especially critical. All the damping is for is to kill the unwanted higher harmonic resonances.
I see. Just checking.

I canīt get it to fill all four compartments (as separated by the bracing)
It is impossible.
Would it - in your opinon - be better to fill the two forward compartments, to fill all four from the top down or to fill them from the 22" down point and upwards?
Sorry to bother you with this type of question, but since I have no idea about the dynamics in work inside the box, I have to ask.
I really want to try to get it right before closing up the box. Getting behind the bracing from the driver holes will be a challenge.
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Old 11th November 2007, 11:05 AM   #577
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It's not a bother. There's no such thing as a silly question if you need to know the answer, and you want to get it right with all the effort you're putting into these cabinets.

Start the damping at the top, and at the required density, go as far down as practicable with it. Stuffing is at its most effective at the point where air velocity for the frequency we wish to damp is at its maximum. For the fundamental resonance (cabinet first mode) this occurs at or near the terminus of the line. The point of maximum air-velocity for the harmonic resonances (which occur at even multiples of the fundamental, in an untapered line like this), being of a considerably shorter wavelength, occur higher up the line. So that's where the damping will be most effective at supressing these while preserving the first mode we are utilising to provide LF gain.

Regards
Scott
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Old 11th November 2007, 11:18 AM   #578
KarlXII is offline KarlXII  Sweden
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Thanks a million, Scott.
What a support you are! I'm really very, very grateful.

Now it's tooltime! I'll be back with more pictures tonight.
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Old 12th November 2007, 02:49 AM   #579
KarlXII is offline KarlXII  Sweden
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One up, one to go.
I actually got 159 grams to fill up the first 22", but it took a lot of tearing and fluffing.

Paintjob next. I absolutely refuse to mount the drivers first - I know they're gonna have that good old MDF-color for years if I do.

Click the image to open in full size.
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Old 12th November 2007, 03:12 AM   #580
troystg is offline troystg  United States
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Quote:
Originally posted by KarlXII
One up, one to go.
I actually got 159 grams to fill up the first 22", but it took a lot of tearing and fluffing.

Paintjob next. I absolutely refuse to mount the drivers first - I know they're gonna have that good old MDF-color for years if I do.

Repute originally stuffed his to the Madisound recommendations but that was WAY too much. Once he removed some they sounded better.

Smart move on the paint first, Reputes are still MDF.
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