Carmody Tarkus 3-Way in a one-piece curved cabinet

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Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

take the dowl down a bit with a fostner bit and bondo.

[johnnyrichards]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

take the dowl down a bit with a fostner bit and bondo.

+1

By the way, this should be a lovely build when completed. It is a good design.

[cowtown]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

It depends on what kind of dowl is used, humidity, temp.... All wood absorbs most of its moisture through the end grain

I'm really, really glad you and FastBike mentioned this BEFORE I blissfully stuck the veneer on!

This is the first speaker build I've done with any non-MDF elements. I wasn't aware there could be a problem with the hardwood dowels, so thanks for that. I don't really know what kind of wood it is. It was marked as "Hardwood dowel" at Home Depot. I'm guessing oak?

The optomial way to do this would have been to drill the dowl holes w/ a forstner bit where the dowls are located from the inside out and stoping within about 1/8th" from the outside, glueing in place and never exposing the end grain. But I would think if Colin would use something like Poly and thin it w/ lacquer thinner and flood the end grain a few days before veneering it will be fine as long as the dowls are realy glued in place securely. R.K.

I was originally going to try to do the holes as you outlined, stopping before punching through, but I couldn't figure out how to locate the holes in exactly the same place on both the front baffle and rear piece. Now that I sit with my 20/20 hindsight, I could have made up a template and put it on top of each piece to locate the holes. But I was in a building groove, and all excited about my clever through-hole bracing scheme. :D

You could always laminate an 1/8" of hardboard over the face of the cab to cover the ends of the dowels. A "pre-veneer" layer if you will. Or if the dowels look nice enough, leave the dowels exposed as part of the finish, I suppose that could look nice if you were doing a birch ply cab with a natural finish.

A good idea - just not sure how I'd deal with the recess for the tweeter flange that is already routed out.

take the dowl down a bit with a fostner bit and bondo.

That sounds good...none of the dowels are glued yet, so it would be really easy to trim them down 1/4" or so.

I've never used bondo - is there a certain type that's best to buy? I'd like to do some practice with it before trying to fix this.

Thanks guys!

[Soundslike]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

Fascinating build there Cowtown. Very nice work -- I can see you're accustomed to doing things with precision. Impressive....

[snmhanson]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

Cool concept and great execution so far. I will be interested to get your listening impression when you are done. Particularly how they sound relative to your Statement Monitors. I too built Monitors, and I am planning on building the Tarkus as soon as I can free up some time. I love your curved cabinet design. I am going to implement some curves as well, though in a different way. Depending on how these turn out, maybe I'll just copy your design (with your permission of course).

Matt

[Randall Kepley]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

Cowtown , take one of your dowels and for every dowel hole you have cut a 1/4" slice off of a scrap dowel to make a plug for each hole. Now take the "Thinned" poly solution I was telling you about and seal each side of the "Plugs" and the edges. When their dry flush glue the plugs on the Veneer side of you cabinets, when the glue fully cures sand a fill any voids you may have. Now on the inside of your cabinets you will have a nice recess and plugged stop for your dowels to ride against, you'll just have to do the math to shorten your dowels to keep your correct dimentions. This will also keep your cabinets from shifting. The 1/4" sealed plug will have no virtually no expantion or contraction and you can veneer right over it w/out worry. R.K.

[cowtown]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

Fascinating build there Cowtown.

Cool concept and great execution so far...I too built Monitors, and I am planning on building the Tarkus as soon as I can free up some time.

Thanks! I've been using the Monitors as mains for over a year (with subs). I'm just itching to build something bigger, and different.

Cowtown , take one of your dowels and for every dowel hole you have cut a 1/4" slice off of a scrap dowel to make a plug for each hole. Now take the "Thinned" poly solution I was telling you about and seal each side of the "Plugs" and the edges. When their dry flush glue the plugs on the Veneer side of you cabinets, when the glue fully cures sand a fill any voids you may have. Now on the inside of your cabinets you will have a nice recess and plugged stop for your dowels to ride against, you'll just have to do the math to shorten your dowels to keep your correct dimentions. This will also keep your cabinets from shifting. The 1/4" sealed plug will have no virtually no expantion or contraction and you can veneer right over it w/out worry. R.K.

Thank you Randall. I didn't get too much done this weekend, but I did take your advice. (By the way, I saw that dovetailed battery box you built in another thread...:eek:. It's like I'm a Cro-Magnon man staring at an iPhone).

It was difficult to cut the plugs without turning them into little bullets that flew off the saw blade and self-destructed when they hit something (I used a miter saw), but I eventually got 20 of them done. Taping the rod around its circumference before cutting helped a bit.

So the plugs are in, and the hurricane nuts installed. Finally, I received the 3" Precision Ports, and had to narrow them down about 1mm to fit the recesses already cut. I should know by now not to cut port holes based on the published measurements, but my router was all set up from cutting the driver holes.

20 plugs finally cut:



Test-fit:



With the port and T-nuts. I didn't see any point in chamfering the insides of the driver holes - the drivers are so large and well-vented that there's no obstruction to speak of. I just hope the baffle is thick enough....



--Colin

[Pete Schumacher]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

--Colin

Take a drum sander and grind away the back half of the cutout hole for the mid, to give them a little more room to breathe.

[critofur]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

...I didn't see any point in chamfering the insides of the driver holes - the drivers are so large and well-vented that there's no obstruction to speak of. I just hope the baffle is thick enough...

A single layer of 3/4" MDF will resonate/transmit some of the back wave - if you put your hand on it while the speaker's playing, you'll feel some significant vibrations.

Thanks for sharing/posting photos.

I might be pressing my luck, but I cut through 3/4" MDF in ~ 3 passes with either the 1/2" or 1/4" spiral carbide bits...

Hardwood dowels are excellent braces for a number of reasons. This thread has good photos illustrating their use. Of key interest is: they could be added AFTER a speaker was built, if somebody builds their speaker without realizing they should have put more braces, or they just figure later that they want to improve it.

I'm quite pleased at the combination of value + quality combination of the drivers used in this project. I haven't heard them yet, but I have both the 10" SLS woofer and a box of 10 of the 5-1/4" "SDS" midwoofers, which would be a decent substitute given some crossover adjustments...

The XT25TG30 tweeter could potentially be implemented as another option. I can't say as to whether it would be audibly superior having not seen direct comparisons between it and the DX25 though...

Take a drum sander and grind away the back half of the cutout hole for the mid, to give them a little more room to breathe.

He would want to be very careful, if he uses a roundover/chamfer router bit, to avoid hitting the nuts... It's something I would probably go ahead and try, but, sparks might fly... Hopefully no bits of metal would end up impaled in flesh (safety goggles should cerrtainly be worn!).

[Paul Carmody]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

With the port and T-nuts. I didn't see any point in chamfering the insides of the driver holes - the drivers are so large and well-vented that there's no obstruction to speak of. I just hope the baffle is thick enough....

For what it's worth, I didnt' chamfer the back of the baffle for mine. Everything is just surface-mounted on 3/4" MDF (except the tweeter, which was flush-mounted).

[Pete Schumacher]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

A single layer of 3/4" MDF will resonate/transmit some of the back wave - if you put your hand on it while the speaker's playing, you'll feel some significant vibrations.

He would want to be very careful, if he uses a roundover/chamfer router bit, to avoid hitting the nuts... It's something I would probably go ahead and try, but, sparks might fly... Hopefully no bits of metal would end up impaled in flesh (safety goggles should cerrtainly be worn!).

For what it's worth, I didnt' chamfer the back of the baffle for mine. Everything is just surface-mounted on 3/4" MDF (except the tweeter, which was flush-mounted).

The thicker the baffle, the more problem a "tunnel" formed by the thicker baffle becomes. There is a chance for resonances to build up in that short chamber, in the upper mids, that a chamfer will greatly reduce.

That's why I mentioned a drum sander. It's easy to grind away the spaces between the t-nuts.

The ONLY problem with hardwood dowels is that when they span a good distance, they will vibrate under load, deflecting the most at the midpoint between the ends. Just physics. That's one reason shelf braces are preferable.

[critofur]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

...the ONLY problem with hardwood dowels is that when they span a good distance, they will vibrate under load, deflecting the most at the midpoint between the ends. Just physics. That's one reason shelf braces are preferable.

Probably worth putting in a cross brace which touches them slightly off center [I say off center so that the two sections will then resonate at different frequencies] then putting a screw through to connect the two. I'd say a cross brace is better than an MDF shelf brace - certainly in terms of performance to volume ratio... Making shelf braces out of 1/2" or 3/8" Baltic Birch would be very good though...

[badman]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

Probably worth putting in a cross brace which touches them slightly off center [I say off center so that the two sections will then resonate at different frequencies] then putting a screw through to connect the two. I'd say a cross brace is better than an MDF shelf brace - certainly in terms of performance to volume ratio... Making shelf braces out of 1/2" or 3/8" Baltic Birch would be very good though...

Or even out of 3/4". The problem with dowels is that they only restrain one point, where shelves tend to have dozens of times as much area. Attached is the bracing system I used for my "ultimate" bassbins.

[cowtown]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

Wow badman, that's some elaborate bracing. Looks great.

At the risk of beating the bracing topic to death, I did a bunch of reading on this site re:dowels vs. shelves and windows, and decided on dowels because
1) My box doesn't have a lot of extra volume and I didn't want to displace any more than necessary; and
2) I read a few fairly convincing posts by respected builders that crossties are pretty effective (not to say that window braces don't work well - I've used windows in all past builds).

I have a feeling that either method would work really well, but the dowels are also "something new" for me to try, and that appealed to me as well.

Here are a few posts about crossbraces that I found really convincing:

http://techtalk.parts-express.com/showthread.php?p=1672676

http://techtalk.parts-express.com/showthread.php?t=221828

http://techtalk.parts-express.com/showthread.php?p=1729379

Probably worth putting in a cross brace which touches them slightly off center [I say off center so that the two sections will then resonate at different frequencies] then putting a screw through to connect the two. I'd say a cross brace is better than an MDF shelf brace - certainly in terms of performance to volume ratio...

I'll do that - thanks!

[mattk]

Re: Carmody Tarkus 3-Way in a one-piece curved cabinet

Probably worth putting in a cross brace which touches them slightly off center [I say off center so that the two sections will then resonate at different frequencies] then putting a screw through to connect the two. I'd say a cross brace is better than an MDF shelf brace - certainly in terms of performance to volume ratio... Making shelf braces out of 1/2" or 3/8" Baltic Birch would be very good though...

I like using shelf supports, for want of a better term, of 3/4" thick mdf or plywood on either side of a cabinet with masonite attached to the supports (with holes of course).