Curved cabinet Overnight Sensation build

[timk]

Rinnav was up here over the weekend, and we cut the parts for his Speedsters on my CNC router. He brought up his OS MTM's that he'd put in some very nice curved cabinets. The looked great and, of course, sounded great.

Here's the link to his thread.

http://techtalk.parts-express.com/showthread.php?t=229387

It inspired me to try my hand at a pair. I'm going to use the same stacked construction method he used because it' well suited to CNC techniques.

I drew up some shapes on the CAD, and then started making test parts. My goal was to get a pleasing shape (to me), and to keep the internal volume the same as the original design using the prescribed baffle dimensions.

The overall dimensions of these are 13" X 7".

http://i27.photobucket.com/albums/c173/tkulin/CIMG4255.jpg

I'm going to need either 19 or 20 of these stacked to make up the proper internal volume.

My plan is to cut rough driver holes in the cabinets once they are all glued up, then put a finished baffle on the front. I'm toying with the idea of covering them with some sort of metallic high pressure laminate. My supplier is looking for something cool right now.

I'll need to stack the ports vertically, and I wonder if that will be a problem.

The next step is just to get some MDF in the shop and set the router to cutting a test cabinet. I'll update after I get that accomplished.

[djkest]

I'll need to stack the ports vertically, and I wonder if that will be a problem.

The next step is just to get some MDF in the shop and set the router to cutting a test cabinet. I'll update after I get that accomplished.

You don't even have to use 2 ports. You could use 1 larger port instead. You could make a slot port, which wouldn't be hard if you are using a CNC to cut your individual "slices"

The problem would be the mouth of the port (inside) in relation to the woofers. BUT, if you look at the OS-MTM from DIY sound group, they put both of the ports behind one woofer and that didn't seem to be much of a problem so.. you could probably get away with just about anything.

[bungelow_ed]

That is a really sleek shape. I can't wait to see the completed boxes.

[lunchmoney]

I would suggest that you cut holes in the layers for dowels to pass thru. This will help you keep them aligned during stack-up.

[timk]

I would suggest that you cut holes in the layers for dowels to pass thru. This will help you keep them aligned during stack-up.

Great idea.

[djkest]

A single 1 7/8" or 2" ID port would work well to replace the dual ports, just to give you an option.

[RINNAV]

Tim,

I will mess around with an enclosure program when I get home and give you an option for a single port. I looked at this when I was planning mine but decided to go with two--I can't remember what the final outcome was off hand. This ought to be really :cool:

How wide is it across the back of that lamination?

[RINNAV]

I would suggest that you cut holes in the layers for dowels to pass thru. This will help you keep them aligned during stack-up.

I thought about doing that when I did my trans-lam but didn't have a CNC available--It would surely make alignment and glue easier. I was going to use triangulation with three in the main body (one on each side and one in center of the back). Three 1/4" hardwood dowels should be sufficient I would think.

[RINNAV]

Rinnav was up here over the weekend, and we cut the parts for his Speedsters on my CNC router...

I guess I should get started on the Speedster build thread now:p

[timk]

Tim,

I will mess around with an enclosure program when I get home and give you an option for a single port. I looked at this when I was planning mine but decided to go with two--I can't remember what the final outcome was off hand. This ought to be really :cool:

That flat section at the rear is only 2 1/4" wide. If the port diameter exceeds that I'll have to fiddle with the design (again) to accommodate it. I might actually prefer the two stacked ports in that case. Due to the limitations of my cad software, it took a fair amount of trial and error to get this design to cut properly.

[timk]

I thought about doing that when I did my trans-lam but didn't have a CNC available--It would surely make alignment and glue easier. I was going to use triangulation with three in the main body (one on each side and one in center of the back). Three 1/4" hardwood dowels should be sufficient I would think.

I just happen to have about 100' of 1/4" diameter aluminum rod left over from a previous job and some special drills for the router that cut holes 0.005" over size.

[timk]

I added the alignment holes and made tops/bottoms. I ran all the scrap we had in the shop but only got 8 of the required 19 slices to complete a cabinet. Still, as a proof of concept it worked fine.

The router is having trouble holding all the little corners that get left over, and it's catching them, running them into good parts and knocking them out of alignment. I may just have to turn them into dust so they don't interfere. I was lucky not to lose any parts, but there was a lot of dancing around the machine grabbing scraps before they could do damage. Scary stuff when you're not dead sure where it's moving next.

http://i27.photobucket.com/albums/c173/tkulin/CIMG4257.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4256.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4258.jpg

[RINNAV]

That flat section at the rear is only 2 1/4" wide. If the port diameter exceeds that I'll have to fiddle with the design (again) to accommodate it. I might actually prefer the two stacked ports in that case. Due to the limitations of my cad software, it took a fair amount of trial and error to get this design to cut properly.

Looking a various models and your 2.25" constraint, I would probably opt for the double vertical 1.375" (1.625" OD) ports too. Going to a single 2" would get pretty long and elbows would likely be needed. Not to mention the vent velocity...

[djkest]

Looks great! I can finally see the pics that I couldn't see before. Unique shape too. These are going to be stunning!

I think Rinnav is right, with that narrow back a 2" port just wouldn't fit. I could argue about the air velocity but it's a moot point. You should seriously think about increasing the internal volume a little- Paul C mentioned that the enclosure size is less than ideal. Even something like 12 Liters would give you a smoother, lower extension. How "high" would that make your speakers?

I'm thinking about attempting curved cabinets on my upcoming "high end" build, maybe I should talk to you about making the internal braces for it. The shape I'm considering is similar to that, but wider, and would probably need a brace right across the middle.

Is that 1" MDF you are using, or 3/4"?

[RINNAV]

I could argue about the air velocity but it's a moot point.

That's why I didn't reference any numbers so you could argue:p A couple of the models I did the vent velocity was reaching ~29 M/S (80W input)--a little high for my taste.

[timk]

I'll add a layer or two with braces on mine, too. Should be easy enough. The material I used for these test pieces is 3/4". 1" might not work well for my design because the parts are so small and the cutting forces large. For bigger parts, it would probably be fine.

[djkest]

That's why I didn't reference any numbers so you could argue:p A couple of the models I did the vent velocity was reaching ~29 M/S (80W input)--a little high for my taste.

I guess you went there:
You know these drivers will bottom out with less than 40W right? (between the 2 of them...)

9 Liters, tuned to 53 Hz (standard Design). Xmax is breached at 80 Hz with 26W input power.
Dual 1.375" ports, 30W input, 24.1 m/s 18.96 cm long (using PE provided parameters, I know this is off)
Single 2" port, 30W input, 22.8 m/s 19.07 cm long

Simply put, a 2" ID port has more cross-sectional area than 2 1.375" ports. It also suffers less from surface effects. And it's less than 1% longer. What are you using to do your modeling?

https://lh6.googleusercontent.com/-q-_37Qpyv2I/TzJ0dEhjROI/AAAAAAAAB6M/B2jjohKSqSw/s800/sim_1.png

[RINNAV]

Even something like 12 Liters would give you a smoother, lower extension.

At 12 liters in volume I see a small 50Hz bump starting to rear it's head. Does your model show the same?

[RINNAV]

You know these drivers will bottom out with less than 40W right? (between the 2 of them...)

Yes, I was using Pe-20w for the input... Not sure if I believe the 40W excursion. I think I have pushed mine harder than that with my UPA-2--no ill effects.

I was using measured parameters for the B4N.

[djkest]

At 12 liters in volume I see a small 50Hz bump starting to rear it's head. Does your model show the same?

Well I'd have to see what parameters you used and if it was a broken-in driver and not a new one, BUT
The bump can be avoided by lowering the tuning. It's a tradeoff between power handling and extension- as has been discussed on the OS-MTM design. (I can dig up some threads if you want)

The standard tuning has something like a 2.2 dB bump in it already, centered around 90 Hz.

ETA: I'm sure the "factory" T/S parameters are off, and it seems Paul C. used his own or someone else's measurements in his design.


Yes, I was using Pe-20w for the input... Not sure if I believe the 40W excursion. I think I have pushed mine harder than that with my UPA-2--no ill effects.

I was using measured parameters for the B4N.

It's hard to say how much power you gave it with the UPA-2, since output power vs. volume is not a linear relationship, but an exponential one. BUT you are right in saying that a simulation, especially one as simple as Unibox, can account for all the factors to determine power handling. The DCR of the air-core inductors in the woofer circuit plays a part in this as well.

TimK- sorry for hijacking this thread. Can't wait to see what comes next for these sweet cabinets.

[RINNAV]

I guess this could be a hijack if Tim absolutely didn't want to use a single port? What say you, Tim?


BTW, I used the CLIO T/S parameters located on the B4N PE page...

[djkest]

Well, it looks like neither the PE data or the CLIO data was used by Paul- the 53 Hz tuning he notes in his writeup requires an 8" long port, not 6" as indicated. So I guess he neither used the CLIO data or the PE / manufacturer provided data.

Anyone have good measurements on the HiVi B4n broken-in?

Coincidentally, the system modeled with the CLIO data looks much better in the 9L enclosure. The one "fault" is that the "D" should not be used for Sd, I think Sd is much closer to 65 or 70 cm^2 than 82 cm^2.

[timk]

One or two ports doesn't matter to me as long as a single will fit that dimension.

[RINNAV]

The Fs difference between the specified and measured (in the CLIO text) really makes a difference on excursion at a specified power... Still getting port velocity in excess of 21 M/s @25 Watts and limited by excursion at ~40 watts in the mid 70Hz range with a 26+ M/s port velocity... Dv=2" and Lv=8"

[timk]

Some progress. This design is terribly inefficient in its use of materials. It ends up taking 1 1/2 sheets of 3/4" MDF. Below are pics of the parts when the router got finished, a stack of freshly cut parts, and the boxes in the clamps. My helper is in the background.

I have some 1" SCH 40. Does anyone know if I can use that instead of the 1.25" and how much I'd need to adjust the length? Should I just go get a stick of the 1.25"?

http://i27.photobucket.com/albums/c173/tkulin/CIMG4265.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4266.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4267.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4268.jpg

[djkest]

Tim:
[Build looks amazing by the way!]
Paul Carmody said that some people have used 1" and reported that it works OK. BUT, according to simulation it WILL chuff when you turn it up. So I would err on the side of caution and get the 1 3/8" ID PVC pipe instead. You can read about it here if you want.


In order to clear up confusion about the vent for the Overnight Sensations, I am spec'ing that one use the 1 3/8" ID Adjustable Port available from Parts Express. Simply glue the sliding portion so that the total vent length is 6". These are easy to mount and give a clean, professional look.

However, if you insist on saving a few bucks, you can use a piece of 1 1/4" SCH 40 PVC pipe. (Whose inner diameter is actually 1 3/8". Why? I have no idea.) This is available at any hardware store. The total vent length is 6" and must include the back baffle.

http://sites.google.com/site/undefinition/diy-overnightsensations


I should also add that this vent from Parts Express has been used by some builders. Due to its reduced diameter, the stock length of 4" is actually right on-target, so no cutting is required. The downside of this vent is that it's pushing the limits of port velocity. However, there are several very nice builds of the Overnight Sensations out there that use this port, so it must be OK.

[timk]

Thanks, that's just what I needed to know. Off to the hardware store.

[timk]

Here they are after block sanding. Vents tomorrow, and maybe the baffles.

http://i27.photobucket.com/albums/c173/tkulin/CIMG4272.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4273.jpg

[CUtiger]

Wow looks awesome, makes me feel super slow as I've only gotten the brace sections cut out for my translam build in over a week. Motivation to go back down to the shop though.

What are you planning for the baffle?

[timk]

Don't feel too bad, I have $100,000 in machinery t use. I darn well better be fast.

The baffle will be 3/4" MDF, probably painted black. I may cut a test piece tomorrow.

[djkest]

Tim,
You are probably all over this but I wanted to "remind" you that it's a really good idea to chamfer the inside of the woofer cutout. If you can chamfer or oversize the woofer cutout in the main cabinet that would be good as well.

Need any gasket tape for your baffle? I have a ton of the really good stuff from parts express. It's a little thick is the only downside.

Cabs look awesome, and you even have your family in there!

[RINNAV]

Woooah! Someone's been busy--looks great! Just got done doing a little work on the Speedsters... I guess I am going to have to step it up tomorrow. For some reason I have a mental block about doing an "in progress" build thread:eek: Your build thread is moving along at break-neck speeeeeed--very nice indeed.

[timk]

I had some inspiration on my run this morning for some adjustable speaker stands. They sidetracked me, so the only progress I made was cutting a set of test baffles.

http://i27.photobucket.com/albums/c173/tkulin/CIMG4276.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4275.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4274.jpg

[RINNAV]

Very nice, maybe I should start running more! I may have to take a run up there after work sometime this week--parts should be in today...

[timk]

Very nice, maybe I should start running more! I may have to take a run up there after work sometime this week--parts should be in today...

Monday, Tuesday, or Thursday are open.

[timk]

Some progress. I'm on death's doorstep with the worst cold I've ever had, but since no one will let me in I decided to get some work done on these.

I ditched the adjustable stands. My wife saw them and was pretty underwhelmed. They're tall because they're going in our bedroom and we have one of those adjustable beds. You actually sit pretty high.

I veneered the boxes in some tiger stripe maple veneer I had lying around. The speaker stand posts are three layers of 3/4" MDF with a big roundover. I wrapped them, too. The baffles, stand bases and stand tops will all be painted. Haven't decided yet exactly what I'm going to do, but it will likely be some sort of textured, multi color finish.

There is some grey analine dye on its way to me. Stuff is hard to find. I'm shooting for something a shade darker than stainless steel. It all ought to coordinate nicely with the room.

Crossover assembly is next, at least until the dye comes in.

http://i27.photobucket.com/albums/c173/tkulin/CIMG4283.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4282.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4288.jpg

[Paul Carmody]

... but since no one will let me in I decided to get some work done on these.


They just leave their sick out in the cold to wither and freeze? ;)

[bkeane1259]

HOLY CRAP.

Next time I'm in CO, I'm booking a vacation in your shop. Not joking.

:p

[timk]

HOLY CRAP.

Next time I'm in CO, I'm booking a vacation in your shop. Not joking.

:p

There's no turndown service here, but if you come out, we'll put you to work.

[timk]

Stain and laquer are on. The stain is a grey analine dye from W.D. Lockwood in NYC. It's alcohol based and very difficult to apply, but it really pops the tiger in the maple. Stands and baffles are in paint right now.

http://i27.photobucket.com/albums/c173/tkulin/CIMG4292.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4293.jpg

[RINNAV]

Wow! Those are looking sweet... I can't wait to hear them all buttoned up. Quit slacking and let’s go:p

Which ratio did you use 1lb to 8 gallons or the 1 to 16?

[timk]

1/4 oz to 1 1/2 pints. Mix ratio doesn't matter much with dyes. Unlike a traditional pigmented stain, a dye gets darker every coat. This is exactly what makes it so difficult to apply. I like to mix it a little light then use multiple applications to work up to the color I want. It allows you to even up the color, shading up the light areas.

Scary stuff. One drip left for more than a second or two leaves a permanent dark spot. I hate using it but love the results.

[timk]

The baffles needed one more clear coat, but here are the boxes on the stands. Crossovers are assembled, so I should be into final assembly tomorrow or Saturday.

http://i27.photobucket.com/albums/c173/tkulin/CIMG4295.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4298.jpg

[timk]

The baffles went on this morning.

http://i27.photobucket.com/albums/c173/tkulin/CIMG4300.jpg

[Sidi]

Wow.

[PWR RYD]

Those look fantastic! Can't wait to see how they look with the drivers installed.

[RINNAV]

Man-oh-man, I can't wait to see these in person... I am sure the picture does not do them justice! I guess you’re waiting on me to bring the binding posts up... If you are going to assemble tomorrow I may have to make a trip up there.

[timk]

Yeah buddy, I'm waiting on you...

[bungelow_ed]

Wow, simply wow! Those are some incredibly beautiful cabinets and stands. I've got some black Transtint.....wonder if it would produce a grey color if dilute enough? I really like that look.

[djkest]

Pretty awesome work there. I really like that, it's unique, and the finished product is pretty stunning. Still curious about 1 thing though- did you chamfer the back side of the woofer hole? Hard to tell from the pics. For the HiVi B4n drivers, it's critical because the venting behind the cone is pretty sparse (and you get reflections coming back through the cone).

I like the painted pieces contrasting with the steel grey dyed birds-eye maple. Who wouldn't want those in their house? :)

Another mundane build detail to keep in mind is stuffing. Paul Carmody recommended a small handful of polyfil or acousta-stuff behind each woofer.

The enclosure could be lined with convoluted foam, which is pretty standard for a vented design such as this. In my case, to keep things simple, I did not line the enclosure at all. Instead, I used a few light handfuls of polyfil behind the woofers (the internal braces sort of held it in place). As I told many people who built the original Overnight Sensations, getting the right amount of stuffing takes a bit of experimentation. I find the best results when I over-stuff a bit, then gradually take some out, listening each time. I know when I get the right sound; the speaker suddenly just sounds "huge."

You probably knew all that though. Congrats on nearing the end. :)

[timk]

The woofer holes in the baffles are indeed chamfered. The holes on the cabinets themselves are not for the obvious reasons. The holes in the cabs are as large as I could make them, so they're as good as can be.

The stuffing (thanks RINNAV) is on the bench, waiting for installation tomorrow.

Hopefully, they'll be done tomorrow.

[Paul Carmody]

They look like they're ready for a Sonus Faber catalog! Great work.

I've found that I like working with dyes. But I'd never heard of gray. I too wonder if black dye, with the right dilution, would achieve a similar result?

[timk]

RINNAV came up yesterday and helped me chew through getting these done. Note the color matching cables he made for me. Pretty sweet.

This was about the most fun I've had building a pair of speakers. Not only did they turn out pretty nice looking, the sound from them is just amazing. I audition with Dire Straits Brothers in Arms, and listening to the 4th track yesterday was quite an experience. I can't believe how close they come to my personal reference pair of speakers with Scan Speak drivers.

Getting to know RINNAV, who inspired the trans-lam idea, has been a real treat, too. Quite a guy. I think we are both looking forward to many more collaborative efforts.

My thanks to Paul for such a great design. I was honestly a little nervous about powering them up yesterday since I'd spent so much time and effort on the appearance. I was worried the sound would be underwhelming considering the modest cost of the components. I just could not be more pleased with the rather amazing performance.

So, here are the pics of the final product installed in the bedroom. Wife acceptance factor is pretty high. She's gotten hard to impress over the years, but this got some high praise.

http://i27.photobucket.com/albums/c173/tkulin/CIMG4337.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4336.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4333.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4325.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4321.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4320.jpg

http://i27.photobucket.com/albums/c173/tkulin/CIMG4309.jpg

[cwad8505]

Wonderful job, Tim!!! These look absolutely stunning! I do love the way that grain popped with your color and finish. Congrats!
Chris

[Leroy R]

Those are beautiful. The quality of craftsmanship of the members of this board never ceases to impress me.

[WWWJD]

Awesome job, Tim!! Solid as a rock.

[timk]

Thanks for the kind words.

Next, I going to whip out an exodus anarchy sub to possibly go with them. I'll build a prototype first to see how it sounds together. If I like it, I'll either jazz up the sub with veneer and a base or build another one with a more interesting shape.

Honestly, these don't need a sub for bedroom use, but I have the driver and amp already and don't need a sub anywhere else in the house.

[Kooshbal]

The baffles went on this morning.

http://i27.photobucket.com/albums/c173/tkulin/CIMG4300.jpg

Silly question, but how did you attach the baffle...just carefully glued and face-clamped?

Awesome build!

[timk]

Correct, just glue and clamps.

[Kooshbal]

And did you use a vacuum press for the veneer work?

[timk]

No, just contact cement. Been doing it that way for 20 years with zero problems.

[Kooshbal]

No, just contact cement. Been doing it that way for 20 years with zero problems.

Paper backed veneer or raw wood? Any experience with the 3M peel and stick veneers on MDF speaker cabs?

[timk]

Paper backed. I've used lots of PSA backed veneer and like it very much. If you do two coats of contact cement on the MDF and then use the PSA, you get a superb bond. I've not made any effort to test the relative bond strengths, but my impression is that the PSA backed stuff is superior.

[Kooshbal]

Paper backed. I've used lots of PSA backed veneer and like it very much. If you do two coats of contact cement on the MDF and then use the PSA, you get a superb bond. I've not made any effort to test the relative bond strengths, but my impression is that the PSA backed stuff is superior.

what contact adhesive are you using?