Pensil 7 (Alpair 7)

[zman01]

Dave,

In my experience the Alpair's have a very pleasing and tight mid-bass; crossing 200 Hz or above will get in the way of that?

-Zia

[chrisb]

Originally Posted by zman01

Dave,

In my experience the Alpair's have a very pleasing and tight mid-bass; crossing 200 Hz or above will get in the way of that?

-Zia

While that certainly couldn't hurt what the 7s do so well above that point, or help but improve the system's overall power handling, you could be encroaching on the area where elegance of XO solution aside, finding a woofer that can seamlessly integrate and not call attention to itself will be more difficult. As mentioned before, I settled on XO of 110/120 for Alpair7s in the front row of my HT system.

[planet10]

Originally Posted by zman01

mid-bass

= 40-80 Hz.

I want to maintain upper bass punch and the option of a passive XO.

dave

[zman01]

On the topic of XO, some sound cards have a "Flexbass" to set the XO anywhere between 50-250 Hz.

However the software XO takes this as a 2.1 system - so the LF information, is this being down-mixed to mono? If mono, then does have 2 woofers play two mono sound streams help?

-Zia

[Studio Au]

Slight update of bracing and alternating (random) inside pattern.

Will start a new thread of the build.

[andb]

Studio Au,

Looks really cool.

1. I think there have comments about increasing the diameter of the front rounding to reduce baffle diffraction, have you decided not to consider that?
2. What if the speaker actually was pushed out a bit increasing the baffle round off not just horizontally, but also to some extent vertically? After all, if you are using CNC, your imagination is your main limitation to design.
3. Can you round off the bracing to make it a cylinder? With all this work to prevent reflections, this seems an easy win.

[Studio Au]

it was just a quick exploration into the bracing and the internal shape, (10 minutes of playing on sketch up). I wanted to try and keep them as slim as possible, but am willing to change anything if it will be beneficial.



1) for ease of construction the actual solid walnut baffle was going to be a single flat piece, however this could be curved from the outer edges of the drivers surround, i think this would have to be done by hand as although quick and east cnc machines still have limitations. To make something KEF Blade like, would require many many more man hours and without knowing the benefits perhaps a waste of time.

3) Do you mean have a circular hole cut? or simply make the struts edges more curved.

I think i need to go back to the drawing board, and start from very beginning.

[chrisb]

Originally Posted by Studio Au

it was just a quick exploration into the bracing and the internal shape, (10 minutes of playing on sketch up). I wanted to try and keep them as slim as possible, but am willing to change anything if it will be beneficial.



1) for ease of construction the actual solid walnut baffle was going to be a single flat piece, however this could be curved from the outer edges of the drivers surround, i think this would have to be done by hand as although quick and east cnc machines still have limitations. To make something KEF Blade like, would require many many more man hours and without knowing the benefits perhaps a waste of time.

3) Do you mean have a circular hole cut? or simply make the struts edges more curved.

I think i need to go back to the drawing board, and start from very beginning.

Consider that in an enclosure fabricated with conventional sheet materials, the intention of bracing is to reinforce structural integrity, and mitigate resonance artifacts of large panel surfaces, which in the case of the Pensils would be the sides and front/back. It would be these panels that I'd think you'd want to brace to each, in a longitudinal manner so as to not interfere with the 1/4 Wave action. (see photos of interlocked holey braces of my own and several other Pensil / super Pensil builds)

"I don't know it for a fact..." , but in the case of curved panels of translam fabrication as drawn, I'd be inclined to suspect the materials would not exhibit the same flex/resonance behavior as single flat sheets of approx same thickness and surface area - so bracing might even be as essential.

The struts shown in your drawing would be bracing the front "corners" and near to the apex of a truncated ellipse - both areas that would likely be subject to less flexation than the center of curved side panels?

Re the curved front panel, if you can model it in your favorite flavor of 3D CAD there is virtually nothing you can't achieve with enough time on a 5 or 8 axis CNC router, but $$$$$

[Jozua]

Hi Studio Au

1. Why not just internal formers and use vertical slats cut to follow the rounded curve?
Alternatively use thinner sheets and build up a laminated wall.
2. If you set on routering why not increase the thickness of the walls?

Regards

Jozua

[Studio Au]

Started a fresh thread, so as to not bloat up this one.

Would be great to think through some more radical ideas

Designing a cabinet for Mark Audio Alpair 7.3