Modifying Markaudio Pensils

[mahleriana]

Hello,
I am eventually decided on building a Pensil for a CHP70 I have on order, rather than a BR, hoping it won't need BSC this way, thanks to Planet10 advice.

I may try solid wood (oak) for the front but won't be able to find it at the specified 146 mm width.
To be sure what is to be kept : volume, mouth area, height, Zdriver ?

Also, some propose to add bracing inspired from the Pensil 12 : is the induced change of internal volume without any impact ?

Thanks in advance !
eric

[planet10]

Most important to keep cross-section, z-driver & height. Going narrower is not really an option, as you still need to fit the driver on the baffle. As well too narrow induces early reflections off the sides back thru the cone. You may have to join 2 pieces of the oak together to get appropriate width. This actually gains 2 advantages... as a (minimal) butcher block you reduce issues with the solid "moving" and cracking and it gives you the opportunity to have horizontally mirrored grain.

The impact on volume of a holey brace is minimal, if you want to be precise, you would increase box width brace by 2/3 the thickness of the brace.

dave

[mahleriana]

Originally Posted by planet10

Most important to keep cross-section, z-driver & height. Going narrower is not really an option, as you still need to fit the driver on the baffle. As well too narrow induces early reflections off the sides back thru the cone. You may have to join 2 pieces of the oak together to get appropriate width. This actually gains 2 advantages... as a (minimal) butcher block you reduce issues with the solid "moving" and cracking and it gives you the opportunity to have horizontally mirrored grain.
The impact on volume of a holey brace is minimal, if you want to be precise, you would increase box width brace by 2/3 the thickness of the brace.
dave

Do you mean global volume and mouth area are in fact not important ?
I am not anyway sure it will be narrower or larger : it depends on the piece of oak I shall eventually find (one piece available I have at home is 136 mm, but I can get some circa 210 mm at quite affordable prices)
Concerning "cracking/moving" : I found solid oak to be less of an issue than solid pine for example.
Anyway Birch ply seems almost unfoundable here in France.

[planet10]

Cross-section + height being maintained means that the volume remains the same.

Port area & Depth needs to be maintained as well

dave

[mahleriana]

So this means you just can't modify anything !

[planet10]

You could make them wider & shallower, keeping the vent the same

dave

[chakija]

One more question: how important is fillet on port edges ? I made my pencil 7 and i left this port flat. I could fillet outer edges of the port, but i don`t know how it will effect the sound so i left it unchanged-rectangular. Also, i have putted damping material from the driver up to the top of the box, 2" on the back side and 1" on the bottom of the box. Side walls and front baffle are without damping...

[planet10]

I don't believe it is critical.

dave

[mahleriana]

Originally Posted by planet10

You could make them wider & shallower, keeping the vent the same
dave

Shallower : 1. the front panel or 2. the depth of the speaker ?

> Kepping the vent the same : is the volume of the vent to be kept (if 1) ? or just the vent height to be kept, whatever its width (if 2) ?


thanks in advance, dave
eric

[Scottmoose]

The box needs to remain the same internal length (i.e. height), driver location needs to remain the same distance from the sealed end, the box needs to retain the same cross sectional area, and the vent needs to retain the same cross sectional area. You can, within reason, alter the WxD dimensions of the box and the HxW dimensions of the vent providing the areas remain per the original design.