The Pencil: inspired by Ohm Micro Walsh Tall

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Hi OhioTanner

Well, the pencil can go anywhere - since the port is on the back, moving closer to wall, increases the bass. I haven't placed them close up to a wall or corner - but general omnidirectional practise states that this kind of speakers prefer some air around'em. Mine is placed with minimum 30 cm to backwall, 200 cm to sidewalls - Minimum, because they are rotated 45 degrees in to the room, like this (to avoid standing waves in general):
 

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Renron said:

This pic (link) reminds me of the Robot in "Lost in Space".
No offense intended.
Ron
Hi Renron - no offense taken - esp. as I once lived in "Sac-of-tomato's" for like 30 plus years. Prototypes have a way of being cute and getting to hang around because of it. Providing that you have a spousal unit that is forgiving and supportive - and believes that I'm a living genus and Lord of Audio! Poor girl - sigh - :angel:
 
Thomas,
Thanks for not being offended, none was meant. :)
I have now been stuck in "Sac-of-Tomatos" for 10 years, Living at Lake Tahoe for 20 years prior to that. Shocking!!!!
You must have a very "understanding" wife unit. I had to pleade and cajole mine into letting me build a pair of "curved small thors" that were "too big" for the living room. Now she accepts the tall sound makers and never complains. I do like the Pencil design.
Ron
 
Sweet loudspeaker!!!!!

Jusper:

That looks like one sweet Microwalsh loudspeaker!!! The choice of woofer is superb - for the money ~$37 the Nomex cone provides for superb FR with well-controlled rolloff above 6 khz (is that a foam, buytl or neoprene surround?) obviating the need for 'mamboni' damping of the cone. And the woofer incorporates a shorting ring and a generous size magnet - very fine choice. I am most tempted to build a pair with your exact choice of premium drivers (the MDT tweeter is top shelf!); I might opt for an intrinsically rigid/nonresonant cyclindrical cabinet and a vertical port in the base. But your design is most esthetically pleasing - very nice to look at.

You get useful bass to about 55 Hz? Have you done any FR measurements? I'll wager that the distortion is very low and the waterfall plot is quite clean and resonant-free.

Congratulations - a job well done.

Have you compared the PENCILs to any other loudspeakers while listening?
 
Hi Mamboni
I think a cylindrical cabinet is far the best - however I couldn't get any decent bass with a vertical port - not even with the 2 foam-shelves above the port (and the peerless couldn't "see" the port).

Well, the bass seems to extend beyond 55 Hz at full level - 55 hz I should get, according to the calculations. I guess the two foam-shelves makes the speaker behave like a MLTL.

I haven't measured FR, BUT I've tried playing sinus waves 200 hz, 190, 180... 60, 55, 50, 45, 40 - and it seems to be at full level to 45 Hz, whereafter a quick roll-off is happening. 40 hz seems subjectively to be half the sound level of 45 hz IMO.

I haven't compared the pencil to other commercial speakers in the building phase - but I've owned KEF IQ3, KEF RDM2, Marten Design Monk, Quad 11L, Mission 707 among others - and have longer listening sessions with Martin Logan (various Models) and Vivid Audio 1.5.

Apart from Marten Design Monk, Martin Logan and Vivid Audio, the others are midfi. Monk, Logan and Vivid are very different, so I can't point at a similar speaker to the pencil - but the pencil makes you play song by song, without skipping the tracks, which previously was boring, but now has come to life...

The pencil is subjectively in the 2000-2500 $ league, compared to commercial speakers. But I have a feeling that it can be enhanced even more by swapping capacitor to Mundorf Surpreme or equivalent. At the moment the x-over is just a single capacitor 2,7 uF in series with the tweeter.
 
Juspur said:


The pencil is subjectively in the 2000-2500 $ league, compared to commercial speakers. But I have a feeling that it can be enhanced even more by swapping capacitor to Mundorf Surpreme or equivalent. At the moment the x-over is just a single capacitor 2,7 uF in series with the tweeter.

Update: The crossover has been updated - it's now just a 2,2 uF capacitor in series with the tweeter. Take a look at:

http://www.humblehomemadehifi.com/Cap.html

I swapped from Jantzen standard to Silver Supreme, ending with the Obligato caps from www.diyhifisupply.com. They are outstanding, period. The Pencil is definitely a superior speaker now, competing in a higher $-league.
 
Hi Sreten
I've just today tried filling the upper part of the speaker completely with acoustilux (slightly pressed). The pro's should be a better impedance response in the bass. From what I've heard so far, a general more clear sound is achieved - not more detailed, but simply clearer. The pencil should probably be seen as a kind of MLTL.
 
Two thoughts:

1) You know, this could be great when loaded as a Transmission line speaker as well . . . the tall shape certainly lends itself to the alignment, and deeper bass response would be possible . . .

2) Anyone out there have the testing equipment to test the side-rear-vs-front FR curve of some drivers? While the posted FR of the Monacor looks most encouraging, I think it is safe to say that the response from the rear (of any driver) could be considerably different - listening 90 degrees off-axis, from the convex rear of the cone. Perhaps better (no dust cap or in-the-cone artifacts), perhaps worse (driver basket and frame diffraction) . . . although being an omni radiator would help with some of the latter. In this configuration, some drivers may yield a radically different response, once past the pistonic range.

Siegfried Linkwitz's Pluto just avoids the concern by firing the driver "face-up" and crossing over at end of piston range. But I totally prefer the minimalist XO your configuration achieves. I, too, hate the ubiquitous 3K crossover point.

I had followed the Mamboni thread with interest as well, so I'm certainly NOT doubting Juspur's results at all. 'Just something the community need consider if relying on manufacturer specs for drivers that are currently only given a "one-sided" test.

:spin:

-- Mark
 
R. Jamm said:
Juspur,
Did you fill the chamber with acoustilux to the 1st 5cm thick damping foam or did you force it down further? Would you now suggest using the damping foam at the suggested point and fill the rest of the chamber with acoustilux material?


I filled the chamber with acoustilux to the 1st 5cm thick damping, which is what I suggest (that means: non-filling from the 1st 5cm thick damping and down to the bottom, apart from the 2nd 5 cm thick damping.
 
Re: Sweet loudspeaker!!!!!

mamboni said:
Jusper:

That looks like one sweet Microwalsh loudspeaker!!! The choice of woofer is superb - for the money ~$37 the Nomex cone provides for superb FR with well-controlled rolloff above 6 khz (is that a foam, buytl or neoprene surround?) obviating the need for 'mamboni' damping of the cone. And the woofer incorporates a shorting ring and a generous size magnet - very fine choice. I am most tempted to build a pair with your exact choice of premium drivers (the MDT tweeter is top shelf!); I might opt for an intrinsically rigid/nonresonant cyclindrical cabinet and a vertical port in the base. But your design is most esthetically pleasing - very nice to look at.

You get useful bass to about 55 Hz? Have you done any FR measurements? I'll wager that the distortion is very low and the waterfall plot is quite clean and resonant-free.

Congratulations - a job well done.

Have you compared the PENCILs to any other loudspeakers while listening?
Where do you find that woofer for $37?

A vertical port in the base works quite well, actually.

Originally posted by Tubamark ...think it is safe to say that the response from the rear (of any driver) could be considerably different - listening 90 degrees off-axis, from the convex rear of the cone. Perhaps better (no dust cap or in-the-cone artifacts), perhaps worse (driver basket and frame diffraction) . . . although being an omni radiator would help with some of the latter. In this configuration, some drivers may yield a radically different response, once past the pistonic range.

Siegfried Linkwitz's Pluto just avoids the concern by firing the driver "face-up" and crossing over at end of piston range. But I totally prefer the minimalist XO your configuration achieves. I, too, hate the ubiquitous 3K crossover point.

I had followed the Mamboni thread with interest as well, so I'm certainly NOT doubting Juspur's results at all. 'Just something the community need consider if relying on manufacturer specs for drivers that are currently only given a "one-sided" test...[/B]
The "back side" of a woofer most often does measure significantly different, and, as drivers are designed to be heard from the "front" that is the side that usually measures best.
 
Juspur said:
... And everybody: Thank you for the positive feedback - I'm looking forward to hear from the next pencil-owner ;)

Enjoy

I've been wanting to try that particular driver in a Micro Walsh variant since about 2003, hadn't gotten around to it yet partially because they're kind of expensive - and - Parts Express discontinued them, so I didn't know if they would continue to be available. The new Nomex series with the phase plugs don't seem to have nearly as nice of a freq. response, unfortunately.

I have some old 6.5" Peerless Nomex drivers to do something similar with, but the cabinet volume has to be quite large with these particular drivers and the response is not quite as smooth.
 
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