Mark Audio CHR-70 Application Thread

[Nanook]

I am thinking of using autobody filler to fill any gaps and create an absolutely smooth surface for the veneering. Does carpenter's glue work well with this, or would you suggest wood filler?

any comments are welcomed.

thanx

[planet10]

Chris uses bondo... he might have some tips.

dave

[chrisb]

Originally Posted by speakrsrfun

Chrisb, if your watching this thread.... How difficult have you found it to get good seems and nice lines with figured veneer around the ports, I'm dreading doing it by hand because the slot isn't wide enough for a flush trim bit, not any I currently have anyhow. And with an xacto knife I've had very limited success with heavy figured veneers, generally with them tearing out along my cut line or causing very uneven cuts, even with a straight edge... Any pointers....?

Anyhow thanks for your time fellahs, it'll help out.

Shane

Shane

I guess there are really 2 parts to this answer, depending on

1) how you like to see the internal slot surfaces finished,

Whether a clear coat or dark paint, I pre-finish the slot internal surfaces during the fabrication of the layered walls - i.e. after the spacers are glued in place, and before attachment of the final panel.

2) the pattern of grain matching and how you actually adhere the veneer to the box

I've found paper backed sheet veneers works best with the iron-on glue method - yellow glue, velour nap paint or veneer glue roller, and clothes iron - particularly for the ease of trimming out the smaller openings we're talking about here.

edit: I'm either too lazy / rushed or short on skills to veneer a speaker enclosure with real (natural/raw) veneers - without some type of backer (kraft paper, wood backed 2-ply) they're invariably very brittle, particularly in the cross grain direction


My own practice is continuous wrapping of the 4 perimeter panels, with the front and back panels center matched from width of sheet. The sequence of overlapping is back/front*/side/side/bottom/top.

*in the case of something like the prime Fonken style with large side chamfers, the front / bevels are one continuous piece, which can be easily folded over the 45` bevel with the iron.

With the iron set to highest temp (linen), there's still a lot of working time. By using the to of the iron, you can quick distinctly outline the boundary of the slots (or rebated driver cutout) to be trimmed out.

Yes, the slots will be too narrow for even 3/8" laminate trim bit, so careful trimming with sharp Olfa utility knife or veneer knife is required. That's where the scorch marks from the hot iron guide you. With some practice (30 or 40 pairs later) the driver opening and port slots can be trimmed out in a single piece - but you might want to start from the center and slowly trim to the demarked edge. You may need to revisit the edges with the iron during the trimming process, and follow up with fine grit PSA sandpaper (150-200 to start) on a wood file or thin stock of wood to dress up the slots, and free hand on edges of rebated driver cut-outs.

[chrisb]

Originally Posted by Nanook

I am thinking of using autobody filler to fill any gaps and create an absolutely smooth surface for the veneering. Does carpenter's glue work well with this, or would you suggest wood filler?

any comments are welcomed.

thanx

Originally Posted by planet10

Chris uses bondo... he might have some tips.

dave

I think bondo etc would be the way to go, particularly if you're using the iron-glue method

I'd say it goes without saying, but as I've said before "that" doesn't work -

it is important that all edges are not rounded over before veneering - rather the opposite to a paint or fabric / vinyl / leather wrapped finish.

[doorman]

Chris: Where's a good source for veneers in Victoria?
Don

[xTr3Me]

Originally Posted by Nanook

Well I must say that in the nearfield, the beta tested dMar-Ken enclosure sounds great, but is a little large. If desktop listening is what you are after, maybe some of Dave's smaller designs (μMar-Kens? cMar-Kens?) might suit. The dMarkens are approximately 325mm (H) X 230mm (W) X 210mm (D) ( 12 3/4" X 9 1/16" X 8 3/8"), so not small, but not huge either. See the attached picture.

Regarding materials, these were built using what is readily available here: Baltic Birch Ply, marine grade, 12.7 mm (1/2"). The slats for the "vents" are BB ply, 10mm, marine grade. Big believer in BB ply as a material. Used 1/2" felt carpet underlay and poly for dampening material. Drivers are Dave's CHR-70eN. The internal dimensions have been strictly adhered to, and a little input from Dave has helped. Perhaps Apple ply or similar might be available where you are at, reportedly very good for enclosures as well. I always strongly advise against MDF for enclosures. Please no "materials" comments, there have been lots of discussions about this here, as well on other forums. Also note the spray painted black vents. This will be sanded down, leaving only the internal vents left black. Every time I see a speaker with lighter coloured vents compared to external finish of the speaker, it looks wrong to me. To be wrapped in Birch veneer, and then finished. I'm thinking either polyurethane or "grain" sealer, then a very red mahogany coloured finish.

Construction is just as TheSeeker has stated, somewhat trivial. Just take your time. With enough carpenters glue, little clamping is required, but suggested. Perhaps the most difficult part is cutting the bevel on the front baffle/sides.

Hi Nanook,

thank you for your reply!

The size of the dMar-ken is no problem for me. The loudspeakers I am using at the moment almost have the same size.

Where can I find further information about this dmar-kens? Actually I couldnt find anything on the net, besides this thread.

And:
What is changed in Daves CHR-70eN driver? And if this special driver is required, where can I get it?


greetings,
Chris

[TheSeekerr]

At this moment in time, only two dMar-Ken designs exist, and neither are generally available - aside from a passing reference on the Planet10 website to the Alpair 7 version, this thread is all the information there is to find (other than the plans themselves, which can only be had by agreement with Planet10).

CHR-70eN is just the EnABLed version of CHR-70 - I haven't heard it, so I can't say whether the sound is markedly different, but the design itself will work fine with both first and second generation CHR-70's, with or without EnABL. CHR-70eN is available from Planet10 Hi-fi.

[Henkjan]

if you want a small cabinet, I would suggest my "Black Beauty" (4 liters GHP)

[Nanook]

Originally Posted by xTr3Me

Hi Nanook,

thank you for your reply!

The size of the dMar-ken is no problem for me. The loudspeakers I am using at the moment almost have the same size.

Where can I find further information about this dmar-kens? Actually I couldnt find anything on the net, besides this thread.

And:
What is changed in Daves CHR-70eN driver? And if this special driver is required, where can I get it?


greetings,
Chris

The CHR-70eN is Dave's modified driver, as seen on his website. He tends to avoid self promotion, as he is one of the moderators here, and he could end up defending himself way too much. He has never (in my experience) disrespected others' work unless a glaring fault. For the amount of work done to the drivers, the premium over the stock ones is worth the extra. The Fe127 (stock Fostex) vs Fe-127eN (modified by Dave) is a no brainer. Someplace someone did a comparison (one of the online audio magazines...6moons?) and greatly preferred the modified drivers. As I have never heard a stock CHR-70, I can't comment, but the differences are expected to be similar to the comparisons to between the Fostex drivers. Someone (not Dave), sells a kit (with instructions) to allow folks to EnABL their own (or is it eNABL?) drivers. The great thing about the CHR-70 drivers is that they have a 4.5mm one way excursion (so 9mm total excursion), which can account for the amazing amount of bass these little guys are capable of.

As I stated earlier in my listening impressions the amplifier choice and sources are very important. Thus far my old Phillips console SE 6BM8 (ECL82) receiver is the best out of class-d, Sanken powered SS, and Nakamichi "Stasis" receiver. Methinks the SE tube amps may ultimately be the best. I need to try my McCormack with them, but feel ultimately it would be at best a compromise. When I get a chance to listen to the big SS amp, I'll post my comments here.

[Henkjan]

somewhat earlier in this thread, there was the subject of which amp. I mentioned that the best I heard my Black Beauties was with a tube amp, but that I did not remember which.. I did some digging and asking: it was a 6W EL84 pushpull amp (DIY of course).