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Old 17th March 2014, 12:05 PM   #1
giulio is offline giulio  United Kingdom
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Default Opinion on Pensil 7 response sought

Hi,

I am finalizing a pair of Pensils with Alpair 7.2 enabled drivers. These replace a pair of open baffle three ways with Lambda TD15s, Supravox 215 and ESG1 Ribbon (you know the WAF story).

At the beginning I just stuffed the box uniformly with the recommended 300g of polyfill. Even after a protracted break in, I could not bear the boxy sound compared to the open baffles. After a long search I got some recycled denim insulation from Innotherm (I guess the UK equivalent of Bonded Logic). I sliced it into 0.75" thickness and lined the area around the driver. I moved the polyfill down to the area below the driver. The sound opened up and I am amazed at what such a small driver can do.

The only minor gripe I have is a mild lack of body in the midrange (most noticeable on male voices and brass instruments). I wonder whether I should increase the amount stuffing. I am hesitant since the current stuffing is already rather compressed (dense).

I wonder if anybody has any suggestion on the basis of the attached smoothed (1/12 octave) in room response taken with REW. The first picture plots the on axis response for the right and left speaker (green and purple) at 1m and the joint response at the listening position (ocre). The second picture is the average of the three.

The response looks rather good to me. I am just wondering whether the peak around 80hz suggests to increase the amount of stuffing or whether it is typical.

Thank you very much in advance.

Giulio
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Old 17th March 2014, 04:03 PM   #2
hajj is offline hajj  Lebanon
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If you made your measurements in-room, anything below around 150hz cannot be really trusted, room modes play a bigger in this frequency range.
Anyway, try reducing the stuffing and see if you get some of the male vocals back
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Old 17th March 2014, 04:26 PM   #3
chrisb is online now chrisb  Canada
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I certainly found that my Pensil7 build (A7.2) needed somewhat ( 1/3?) less than the suggested amount of stuffing to elicit the tonal balance that worked for my room/system. They're currently running on a Denon HT receiver, XO'd at 110Hz, and I've yet to be interested enough to get someone who cares and has the appropriate gear to take some in-room measures. In any case, the Audyssey calibration / EQ probably helps out in that respect.

Assuming that your enclosures have easy access, I'd play with removing a small portion of the fiber, and teasing out the remaining.

At the risk of opening a can of worms here, what material are the enclosures, and is there any bracing between side walls?
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Old 17th March 2014, 07:20 PM   #4
giulio is offline giulio  United Kingdom
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Thank you both.

To Hajj: the fact that the peak shows up on both speakers and with the mic in three different positions made me hope that it was not a room mode.

To Chris: 18mm Baltic birch ply, there is a horizontal rectangular brace (basically a 1" frame) connecting the four walls.

The back is screwed, so I will try to take away some stuffing.
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Old 17th March 2014, 07:26 PM   #5
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Quote:
Originally Posted by giulio View Post
there is a horizontal rectangular brace
Incorrect orientaion. It will create a restriction ine TLs cross-section and is less effective as a brace than a vertical brace.

dave
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Old 17th March 2014, 08:50 PM   #6
chrisb is online now chrisb  Canada
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Try to orient like below - interlocking / full length not essential, but can't hurt either.
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Old 18th March 2014, 06:21 AM   #7
giulio is offline giulio  United Kingdom
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I will experiment over the weekend and report back. Too late for the brace though...

Thanks
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Old 24th March 2014, 10:23 PM   #8
giulio is offline giulio  United Kingdom
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As promised here's my update.

It turns out that the version measured above had 200g of stuffing.

I have teased out the stuffing more as suggested by Chris (see picture) and I have first taken out and then added 50g of it. I have measured and listened. Both 150g (green plot below) and 250g (blue plot below) sound to me and measure better that the original 200g version. I conjecture that the stuffing in that version had not been teased out enough.

Of the two I prefer the version with 250g of stuffing. After some more listening, I might even try 300g next weekend.

Attachment 408102Attachment 408103Attachment 408104

Last edited by giulio; 24th March 2014 at 10:26 PM.
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