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Old 5th April 2013, 12:45 PM   #11
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Thank you all for the replies... I am using PolyFil, 2.5 lbs per cabinet.
I will remove some PolyFill and see where that leaves me.

The inside walls are not lined with anything.
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Old 5th April 2013, 12:46 PM   #12
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Quote:
Originally Posted by mp9 View Post
I'm not getting where the simple rectangle equates to a Mass Loaded-Transmission Line aspect of the two designs? two designs?
An MLTL is a vented box. Bass reflex design assumes a uniform air particle density in the enclosure and no standing waves. An MLTL deliberately generates and uses standing waves in the box. The transition point from one to the other could be said to occur when one dimension is stretched sufficiently for the resulting eigenmodes (standing waves) to shift Fb for a given set of vent dimensions, or otherwise alter the FR from what you would obtain / be indicated for a given Vb under purely Helmholtz resonant conditions.
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Old 5th April 2013, 12:48 PM   #13
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Originally Posted by RonVinyl View Post
Thank you all for the replies... I am using PolyFil, 2.5 lbs per cabinet.
I will remove some PolyFill and see where that leaves me.

The inside walls are not lined with anything.
Good, they shouldn't be lined. To an extent, it depends on the amplifier & room conditions; that's why I designed them to have a degree of adjustability with a removable back & the damping. As an initial step, reduce overall damping density by 1/3 throughout; also make sure the damping isn't crammed up against the driver; too much too close will mass-load the cone & distort it under dynamic load conditions, preventing it from oscillating as intended.

As I say, the A12P based pensils are never going to be bass-monsters; that's not what they, or the driver were designed for, but they are quite efficient boxes and and not particularly reactive, so distortion levels are reasonably low and they're an easy load for most amplifiers, short of 500mW spud amps of course.

Last edited by Scottmoose; 5th April 2013 at 12:51 PM.
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Old 5th April 2013, 12:49 PM   #14
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Originally Posted by xrk971 View Post
Yes, +1 on this, make sure you follow stuffing plan. But typically no more than top 2/3 of pipe should be stuffed or 26 in down from top and the less you stuff, the more boomy the bass. If you stuff all the way and stuff densely, it becomes aperiodic and you get no bass enhancement.
The stuffing might be too close to the driver. I didn't know it needs to be 26" down from the top of the cabinet. Thanks!
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Old 5th April 2013, 12:50 PM   #15
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Can the wire used between the driver and the binding posts cause a large variance in HF or LF response? I am using 12 gauge speaker wire.
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Old 5th April 2013, 01:02 PM   #16
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Originally Posted by RonVinyl View Post
The stuffing might be too close to the driver. I didn't know it needs to be 26" down from the top of the cabinet. Thanks!
That's because it doesn't. They're designed to a default uniform damping density. Xrk presumably isn't aware of the specifics of the alignment used in these boxes. You can of course adjust to taste; that's why a removable back is strongly recommended. As I say above, as an initial step, try reducing total damping density by 1/3. Then adjust as you see fit / prefer. This may be necessary in any event, since dacron hollow-fibre pillow stuffing is assumed, but there's dacron & then there's dacron. There's a lot of different types, and they often have somewhat different damping properties which you don't know about until you try it unfortunately.

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Can the wire used between the driver and the binding posts cause a large variance in HF or LF response? I am using 12 gauge speaker wire.
Yes, if resistance is high enough. 12ga is frankly overkill for internal wiring, at least in terms of low resistance levels. You could try shifting to a pair of 24ga conductors pulled from a run of Cat5. The additional series R won't ammount to anything significant over short internal runs, but at least it's solid core.

Last edited by Scottmoose; 5th April 2013 at 01:04 PM.
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Old 5th April 2013, 01:11 PM   #17
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Hello RonV,
Can you take some close-up pics of the Polyfill? There's several grades, some might be closed cell, which must be avoided at all costs.

Cheers
Mark.
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Old 5th April 2013, 01:18 PM   #18
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Originally Posted by markaudio View Post
Hello RonV,
Can you take some close-up pics of the Polyfill? There's several grades, some might be closed cell, which must be avoided at all costs.

Cheers
Mark.
I used this for my PolyFill: Amazon.com: Fairfield Poly-Fil Premium Polyester Fiber, White, 1 Box, 5-Pound: Arts, Crafts & Sewing
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Old 5th April 2013, 03:33 PM   #19
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Looks to have finer fibres compared to some others I've seen, so the box is likely overdamped. As I say, first step, try reducing total packing density throughout the enclosure by 1/3 & see how you go from there.
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Old 5th April 2013, 03:52 PM   #20
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The best poly-fill is Hollow-Fill, fibers are like straws rather than solid strands! Better than that is multi-hole strands.

Larry
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