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Old 14th May 2013, 07:52 AM   #141
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Excellent. Many thanks for the measures. Correlates nicely with what I was aiming for with the design under practical conditions.
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Old 10th August 2013, 02:23 AM   #142
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How sensitive are the Pensils to room placement? I'm looking for something that can ideally still work either in or out of corners.

Am I wrong to think the Pensils may be more flexible for placement than the FH3s?

Any feedback on placement and associated effects would be appreciated.

Thanks.
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Old 10th August 2013, 08:25 PM   #143
chrisb is offline chrisb  Canada
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in short, you're correct - the Pensils are far less sensitive to room placement than the FH3s, but I'd still strive for symmetrical placement in relation to room boundaries, open archways, etc.
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Old 11th August 2013, 01:13 AM   #144
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Quote:
Originally Posted by chrisb View Post
in short, you're correct - the Pensils are far less sensitive to room placement than the FH3s, but I'd still strive for symmetrical placement in relation to room boundaries, open archways, etc.
If speaker placement in the room is asymmetrical it'd less likely to generate room resonances. At least that's how the acoustics should work out. In a true nearfield arrangement, it shouldn't matter much except for bass reinforcement.
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Old 22nd September 2013, 01:56 PM   #145
martinn is offline martinn  Germany
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Default How does one properly stuff a Mark Audio's Pencil 7 and Alpair 7.3 drivers?

Whatever combination of amount of stuffing material and compactness I have tried some frequencies are still missing.

What is missing I guess are the higher harmonic frequencies.

For example mike oldfield's musica universalis sounds very dull
musica universalis MUSIC OF THE SPHERES - YouTube

or hugh masekela's stimela misses the sounds which are in the background. Drumms are there, vocals and trumpet are also very clear and precise, but in between a lot of hmm sounds which bring the color to the music are not there (and with my headphones I hear them, so it's not the cd player .

If I make the stuffing very compact around the drivers (first two pictures), the sound is more punchy and louder. I've tried stuffing below the drivers and the speakers are very neutral (last two pictures). But more or less stuffing, or a combination of driver stuffing and cabinet loose stuffing, or no stuffing at all, doesn't bring the color to the music. I am slowly running out of ideas what to try.

On the back of the speakers and the top around the drivers the black rim is a sheet of bitumex. If you have any ideas what I am doing wrong or what I can change to improve the sound I'd be more than happy to hear them

Martin
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Old 23rd September 2013, 05:05 AM   #146
zman01 is offline zman01  Bangladesh
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martinn,

Looks like you will need to change the stuffing - both type and how you have installed it in the cabinet.

The stuffing that is recommended for the Pensil deisgn is dacron type polyfill; if you prefer a "brand" then Acousta stuff comes to mind, however generic dacron should also work.

The polyfill should be fluffed up and distributed throughout the cabinet. Do not place too close to the rear of the driver, and do not block the port. Recommended quantity AFAIK is 0.75 lb/cubic foot, but you might end up needing less.

I see that you do not have any bracing installed in your cabinet - if the stuffing keeps on falling down you might have to put in a horizonal brace (will stiffen you cabinet too) or maybe few pieces of string criss-crossed on the inner sides to support the stuffing material.
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Old 23rd September 2013, 03:43 PM   #147
chrisb is offline chrisb  Canada
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as Zia notes, any of the stuffing configurations shown would not yield the best results, and some bracing wouldn't hurt either

I might get a bit carried away, but like to include side to side and front to back in a tall enclosure like these. It also helps to keep the teased out fibre fill in place.

I don't have pictures at hand of these with stuffing, but as Zia noted, I ended up pulling out some of the originally recommended amount
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Last edited by chrisb; 23rd September 2013 at 03:45 PM.
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Old 23rd September 2013, 04:15 PM   #148
martinn is offline martinn  Germany
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Thanks a lot for the suggestions Zia and Chris. It sounds much better now that I use more stuffing. There is more dampening and I have to turn the volume up to get the same loudness. And then the low-mid frequencies I've been missing, also get louder.

Is dacron = polyester fleece? The white one is puffy polyester fleece and the darker one is sheep's wool. I got it from some on-line store.
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So the next step would be to make the stuffing really fluffy, but if I make it fluffy it's going to fall on the driver?

I am just curious, but I don't understand why there shouldn't be any stuffing directly around the driver? It has a metal cap, so the stuffing won't obstruct any moving parts. And if I remember what I've seen in the forums, the bracings are often done in a way that they touch the back plate of the driver, but not press on it with force. Is a bit of air movement desired?

Martin
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Old 23rd September 2013, 05:18 PM   #149
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Dacron is a brand name for hollow fibre pillow stuffing.

The cabinets are designed with a default for uniform density throughout. After that, adjust to your own taste / requirements. That's why I designed them with a removable back: so people can experiment as they wish. Give a little room around the driver however to prevent any possible excess of pressure temporarily distorting the cone under higher loads.
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Old 23rd September 2013, 05:28 PM   #150
chrisb is offline chrisb  Canada
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Yes, dacron = polyester fleece. Probably the best of class would be considered to be Acousti-stuff.

When well teased out and even bracing less elaborate than shown in my earlier photo (such as a few 1/2" dowels), or some strategically placed strips of the male barbed side of Velcro, the fibrous material will not shift as much as you seem to be worried about.


Alpair cones are very thin metal alloys, and too much fill, particularly very high density, immediately behind them could cause compression of dynamics, coloration that's easiest to describe as chesty-ness, and distortion of lower level detail at the very least. I've found the same to be true of very shallow depth enclosures with paper or metal cones.
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