"Boathull" custom milled speakers/cabinets

tortugaranger · « **on:** 8 Sep 2015, 09:04 pm »

I've been working with a customer who is looking for a set of custom speaker cabinets that utilize a curved laminated cabinet shaped like a boat hull...hence "boathull speakers". These will be milled out of baltic birch plywood and finished naturally showing the thin laminate look of this fine hardwood plywood. The top, bottom and baffle will be veneered. The pics below don't reflect the external "look" of the final version but the structure and shape are accurate.

Once we get these done I may build a similar but larger mid-size cabinet suitable for a Audio Nirvana full range driver.

Anyone interested in something similar feel free to contact me. Keep in mind these are not low cost cabinets. I won't do these in MDF - the dust is terrible even with a good vacuum system.

Here are a few CAD pics. The last one is a top view with the top removed showing the internal brace located between the 2 drivers.

datman · « **Reply #1 on:** 8 Sep 2015, 10:11 pm »

I am looking for a pair of cabinets for an Audio nirvana 15 inch classic driver. The Audio Nirvana cabinet designs suggest a 5.6 cubic foot bass reflex box. I don't know if this design would be appropriate or not. I have already spoken with a couple of cabinet makers but I would like something really special.

mresseguie · « **Reply #2 on:** 8 Sep 2015, 10:43 pm »

In your design, are the front baffles Baltic birch plywood, or could another material be used? Specifically, I'm curious about using Plyboo (bamboo plywood) with matching tops and bottoms.

Thank you.

Michael

FullRangeMan · « **Reply #3 on:** 8 Sep 2015, 10:46 pm »

Quote from: datman on 8 Sep 2015, 10:11 pm

I am looking for a pair of cabinets for an Audio nirvana 15 inch classic driver. The Audio Nirvana cabinet designs suggest a 5.6 cubic foot bass reflex box. I don't know if this design would be appropriate or not. I have already spoken with a couple of cabinet makers but I would like something really special.

Experts say this 5.6 box is not suited to the TS pars from this driver, but if its for guitar use...
I would suggest the Super10Alnico to stick with manudacturer.

tortugaranger · « **Reply #4 on:** 8 Sep 2015, 10:48 pm »

Quote from: datman on 8 Sep 2015, 10:11 pm

I am looking for a pair of cabinets for an Audio nirvana 15 inch classic driver. The Audio Nirvana cabinet designs suggest a 5.6 cubic foot bass reflex box. I don't know if this design would be appropriate or not. I have already spoken with a couple of cabinet makers but I would like something really special.

I had roughed out a layout for a 12" Audio Nirvana the other day which ended up with a ~48" tall boathull stack. Obviously the 15" driver would need a wider baffle. Something like 18-20". I think the 12" boathull had a 20" depth. If I wider then baffle to accommodate the 15" driver the volume per slice will go up probably from 200 sq inch to over 250 which will reduce the height several inches. To keep total height up towards 48" would have to reduce the depth. Definitely doable. And it would definitely be something really special.

tortugaranger · « **Reply #5 on:** 8 Sep 2015, 10:57 pm »

Quote from: FullRangeMan on 8 Sep 2015, 10:46 pm

Experts say this 5.6 box is not suited to the TS pars from this drivers, but if its for guitar use...
I would suggest the Super10Alnico to stick with manudacturer.

One thing I have noticed looking at the Audio Nirvana's is the Qts vary considerably depending on whether you go with Alnico or Neodymium. On the 15" driver it's 0.98 and 0.34 respectively. That's going to have a huge impact on optimum size. The optimum volume on the 15" Alinco's is enormous. Neo's are more reasonable.

FullRangeMan · « **Reply #6 on:** 8 Sep 2015, 11:01 pm »

Why the 15'' model?
The best TS data in this brand are the new Classic10Alnico, which VAS also big.

tortugaranger · « **Reply #7 on:** 8 Sep 2015, 11:04 pm »

Quote from: mresseguie on 8 Sep 2015, 10:43 pm

In your design, are the front baffles Baltic birch plywood, or could another material be used? Specifically, I'm curious about using Plyboo (bamboo plywood) with matching tops and bottoms.

Thank you.

Michael

Yes, the approach with veneer is use baltic birch but no reason you can't go with bamboo ply without veneer. We have some 1/2" bamboo ply in our shop and for the most part it mills ok. It does have a tendency to chip out along the cut edge but worst case that can all be milled out. For that matter we can make the whole thing out of bamboo but it's pricey stuff. Cost us $500 to land 2 4x8' sheets of 1/2" - almost half of that was commercial trucking so it pays to buy in volume. You'd want 3/4" or 1" for baffle material etc.

tortugaranger · « **Reply #8 on:** 8 Sep 2015, 11:12 pm »

Quote from: FullRangeMan on 8 Sep 2015, 11:01 pm

Why the 15'' model?
The best TS data in this brand are the new Classic10Alnico, which VAS also big.

Not sure if "bigger is better" applies here but that's probably the thought behind it.

I've had Super 8 Alnico's running in mid size ported box for a few years now and I think they're amazing. Have not tried their newer Classic line without the whizzer cone. Do you think the Classic's are superior to the Supers?

FullRangeMan · « **Reply #9 on:** 8 Sep 2015, 11:16 pm »

I think the lack of whizzer cone prevent the beaming.
The Classic line seem a upgrade from the Super.
Definitely I prefer the Classic Alnico, mainly the 10'' model.

ebag4 · « **Reply #10 on:** 8 Sep 2015, 11:17 pm »

Here is a link to a similar project albeit done for GR Research drivers:
http://www.audiocircle.com/index.php?topic=79983.0

Best,
Ed

FullRangeMan · « **Reply #11 on:** 13 Sep 2015, 02:03 pm »

Quote from: tortugaranger on 8 Sep 2015, 11:12 pm

Not sure if "bigger is better" applies here but that's probably the thought behind it.

I've had Super 8 Alnico's running in mid size ported box for a few years now and I think they're amazing. Have not tried their newer Classic line without the whizzer cone. Do you think the Classic's are superior to the Supers?

Hi,
Here is a comparison Super10Alnico x Classic10Alnico for your evaluation,
you will note Super are stronger at bass and hi freq while Classic is smoother.
Also smoother at the Impedance chart.

DaveC113 · « **Reply #12 on:** 13 Sep 2015, 02:09 pm »

Quote from: FullRangeMan on 8 Sep 2015, 11:16 pm

I think the lack of whizzer cone prevent the beaming.

It does not... but it is likely the highs will be rolled off on a 6.5" or larger driver without a whizzer.

FullRangeMan · « **Reply #13 on:** 13 Sep 2015, 02:17 pm »

Quote from: DaveC113 on 13 Sep 2015, 02:09 pm

It does not... but it is likely the highs will be rolled off on a 6.5" or larger driver without a whizzer.

So remove Super10Alnico whizzer will be a great tweak?

DaveC113 · « **Reply #14 on:** 13 Sep 2015, 02:22 pm »

Quote from: FullRangeMan on 13 Sep 2015, 02:17 pm

So remove Super10Alnico whizzer will be a great tweak?

No, I think you need a whizzer on a larger single driver. You can see the classic 10 is very rolled off, I couldn't deal with that but I suppose some like it.

Morten, nice cabinet! I have access to a Shopbot CNC router which I am very excited about. Going to be making waveguides and cabs out of stacked ply...

FullRangeMan · « **Reply #15 on:** 13 Sep 2015, 02:30 pm »

Quote from: DaveC113 on 13 Sep 2015, 02:22 pm

No, I think you need a whizzer on a larger single driver. You can see the classic 10 is very rolled off, I couldn't deal with that but I suppose some like it.

Morten, nice cabinet! I have access to a Shopbot CNC router which I am very excited about. Going to be making waveguides and cabs out of stacked ply...

OK thanks for your evaluation.

craig sawyers · « **Reply #16 on:** 13 Sep 2015, 04:56 pm »

Quote from: tortugaranger on 8 Sep 2015, 11:04 pm

Yes, the approach with veneer is use baltic birch but no reason you can't go with bamboo ply without veneer. We have some 1/2" bamboo ply in our shop and for the most part it mills ok. It does have a tendency to chip out along the cut edge but worst case that can all be milled out. For that matter we can make the whole thing out of bamboo but it's pricey stuff. Cost us $500 to land 2 4x8' sheets of 1/2" - almost half of that was commercial trucking so it pays to buy in volume. You'd want 3/4" or 1" for baffle material etc.

Bit off topic, but relevant to baltic birch and veneering....

These are 3/4" (19mm) baltic birch dipoles that I built to Siegfried Linkwitz's LX521 design. The top parts and bridge are hand veneered using hide glue and French polished by moi, because I'm a traditionalist. The dark wood is solid Cocobolo rosewood. The feet at the bottom of the bridge are Goncalo Alves. The bass dipoles are also baltic birch and are painted in black milk paint.

Craig

tortugaranger · « **Reply #17 on:** 1 Nov 2015, 02:31 pm »

A few pics of the custom set of "boathull" speakers we're making for a customer. These are 0.32 cubic foot cabinets for a 2-way design. These will look very cool when finished. The baffle and top/bottom will be veneered in zebra wood to compliment that striped laminate look of the baltic birch. Took a bit of trial and error on laying out the boathull toolpaths but after the first few we adjusted the layout/spacing and it went smoothly. Always nice working with wood.

After building the initial stack but without ends and before sanding. The peppering you see is part of the plywood color variations and are not voids. Very few voids in the baltic birch plywood and what few their are will fill in nicely and disappear.

The first boathull stack - 17 layers. Each glued and power nailed. Extremely strong/rigid even without baffle, ends or internal brace.

Tried to maximize utilization of the wood while maintaining the integrity of the sheet to keep it clamped down in place while milling. The lower right corner area shows initial attempts at getting even more utilization but this proved unworkable as adjoining pieces would not hold together during milling.

poseidonsvoice · « **Reply #18 on:** 1 Nov 2015, 02:47 pm »

Suhweet! Digging it! I know it's not easy!

Best,
Anand.

mresseguie · « **Reply #19 on:** 1 Nov 2015, 03:01 pm »

Thank you for posting the update. This had slipped my mind. (happens to me a lot it seems)

I like how this looks, but I don't have a clue how much this might cost for a pair. Are you comfortable putting a probable cost for the pair in this thread either or in a PM? A ballpark price is fine at this point. My next pair of speakers will have 6.5" to 8" midwoofers in a two-way monitor. Im still debating different speakers' merits.

Michael