SEOS-15 / DNA-360 + AE TD15M center channel - AVS Forum
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post #1 of 42 Old 11-23-2012, 11:07 PM - Thread Starter
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I finished my last build yesterday, and I've got a lot of parts ready to go for my next build, so lets get started...

I am building a single center-channel speaker to go in my fireplace. The fireplace opening is 32.5" wide x 27" tall. It is 19" deep at the top, and 23" deep at the bottom. The sides close in toward the back, too. I never burn anything in it, so I don't mind putting a speaker in there. I don't want any ports blowing soot around, though, so I need to go sealed or front-ported. The fireplace is visible in this picture:



I have a fiberglass SEOS-15 waveguide and DNA-360 compression driver, and an AE TD15M-8 midwoofer. I will be building speakers with the same drivers for the left and right next, and I always use subs (a THT currently), so I only need to be able to blend around 80Hz, but I view some additional extension as a plus. I want to go passive later, but Bwaslo has shared MiniDSP settings with me for the drivers that I'm using to get started. Thanks bwaslo!

So, I am open to suggestions for the cabinet design, if anyone has been thinking about these drivers and what they would do with them. I saw LTD02's chart here with some cabinet volumes and port tuning: http://www.avsforum.com/t/1291022/hey-guys-we-need-a-little-rallying-here/4350#post_22160832

Judging by the looks of Erich's CNC front baffle for the SEOS-15/JBL, which is 17.25x25", I can make my drivers fit in the vertical space, and maybe even have room for a slot port. The AE woofer does have a slightly larger OD at 15.563" vs. 15.25" for the recess diameter in Erich's JBL baffle, but that isn't a huge difference.

All my builds thus far have been from plans, so I'm having to learn a bit more this time, and I've got more questions. Such as:

1. With the Econowaves that use the (tall) QSC 152i waveguide, I read that it was important to minimize the center-to-center distance between the waveguide and midwoofer. So I know that the c-c distance is important for tuning. But that maybe it need not be minimized as aggressively with the shorter SEOS waveguides (as compared to the 152i). And I will need to have my waveguide and midwoofer pretty close just to fit in the available space, but is there an "ideal" distance between the two? Do I need to use the same distance that bwaslo used, so that I can use his minidsp settings?

2. I would like to mount my waveguide and midwoofer in recesses so that the they are flush-mounted in the baffle. But I remember that it was important to mount the midwoofer on the back of the baffle for my Econowaves to line up the acoustic centers of the drivers. Maybe this doesn't matter for active speakers, but I want to go passive later. Are there any acoustic issues that I need to be aware of as it relates to flush-mounting my waveguide and midwoofer?

3. The center of the waveguide will be about ~21" off the ground, and my ear is ~39" off the ground in my listening position. My listening positing is 13' away from the front of the fireplace. Are there any acoustic issues with sitting that far above the center of the waveguide? Should I consider angling the speaker (or the baffle) up to point it at my ears?

4. If I decide to go ported, I will probably need to make the baffle wider to achieve the necessary volume. I've been playing around with the dimensions and calculating volume in this spreadsheet. Are there acoustic reasons to avoid a wide baffle? On the other end of the spectrum, should I consider making the baffle take up the full area of the fireplace opening, so that it will be flush with the tile surface and thus effectively 59.5" wide (the full-height fireplace column is that width, with no mantle, and it sticks out 22.75" from the wall).

I know that I am asking a lot. Any feedback is welcome.

Thanks!
-Max
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post #2 of 42 Old 11-24-2012, 01:38 AM
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are you sure that you need/want a center channel?

that is a pretty big distance from the screen to the speaker and would drive me crazy.

"I will need to have my waveguide and midwoofer pretty close just to fit in the available space, but is there an "ideal" distance between the two?"

they should be close together.

if you are crossing to subs at 80hz, sealed 2.5-3.0 cubic feet is pretty much right on the money for the td15m. -3db right on 80hz.

Listen. It's All Good.
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post #3 of 42 Old 11-24-2012, 05:55 AM
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For starters, the baffle you are referring to uses a SEOS-12 like in the build on another thread here. I don't know if Erich has plans for SEOS-15 with 15" woofer baffle.

You can go sealed or vented. I usually suggest vented with the option to stuff the ports. This gives you the ability to try which ever alignment works best for your room and subs.

You generally want the waveguide to be as close to the woofer as possible. When using a crossover designed by someone else it is best to maintain the same spacing as the designer.

The Ewave Deluxes where back mounted to make passive crossover design easier. It is an option and may or may not make crossover design easier. It depends on a number of factors. You should mount it the same way that the designer of your crossover mounted his.

I concur with LTD that you might be better of with just a L/R and a phantom center given the odd positioning of the center. If you do still build the center I would suggest building it at an angle so it is on axis with the listening position or at least as close as possible.
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post #4 of 42 Old 11-24-2012, 01:08 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

are you sure that you need/want a center channel?
that is a pretty big distance from the screen to the speaker and would drive me crazy.

Good question. I used to have a 5.1 setup, but I've been running 2.0 or 2.1 for the past 3 years after a move. I miss the 5.1 setup, but maybe I mostly miss the surrounds, rather than the center. As a test, I will stick a bookshelf in the fireplace (and elevate it near the top) and see how I like it.

Thanks,
-Max
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post #5 of 42 Old 11-24-2012, 01:22 PM - Thread Starter
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Quote:
Originally Posted by coctostan View Post

For starters, the baffle you are referring to uses a SEOS-12 like in the build on another thread here. I don't know if Erich has plans for SEOS-15 with 15" woofer baffle.

I know that most of them are for the SEOS-12, but that one is actually for the SEOS-15 and a 15" JBL woofer:
http://www.diysoundgroup.com/speaker-baffles/seos-15-jbl-baffle.html
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Originally Posted by coctostan View Post

You can go sealed or vented. I usually suggest vented with the option to stuff the ports. This gives you the ability to try which ever alignment works best for your room and subs.
You generally want the waveguide to be as close to the woofer as possible. When using a crossover designed by someone else it is best to maintain the same spacing as the designer.
The Ewave Deluxes where back mounted to make passive crossover design easier. It is an option and may or may not make crossover design easier. It depends on a number of factors. You should mount it the same way that the designer of your crossover mounted his.
I concur with LTD that you might be better of with just a L/R and a phantom center given the odd positioning of the center. If you do still build the center I would suggest building it at an angle so it is on axis with the listening position or at least as close as possible.

Thanks for the info / suggestions. It seems like the sealed/ported decision comes down to whether I want my L & R to be sealed or ported, and that I should make the center match. I need to think about that, but I like your suggestion about making it ported to give me the option of stuffing the ports. I like the additional extension from the ported box, too. It would be a weird shape, but I could make a 5cf ported box for the center that would fit in the fireplace -- something like 25Hx28Wx17D, with ports on the baffle on both sides of the drivers.

-Max
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post #6 of 42 Old 11-24-2012, 01:48 PM
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The description for the baffle says "Designed specifically for the SEOS-12 plastic or fiberglass waveguide and the JBL 15" 2226 woofer models."

I agree that the title reads differently. You should talk to Erich before ordering.

It isn't vital that your center matches the mains on alignment. I simply prefer having flexibility.
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post #7 of 42 Old 11-24-2012, 03:14 PM - Thread Starter
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Quote:
Originally Posted by coctostan View Post

The description for the baffle says "Designed specifically for the SEOS-12 plastic or fiberglass waveguide and the JBL 15" 2226 woofer models."

Oh, I see that now. And judging by the relative size of the woofer and waveguide recesses, that must be the SEOS-12. The SEOS-15 is 15.5" wide, which would be wider than the woofer recess.

I wasn't actually planning to order that, but rather I was just using it for size reference.
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It isn't vital that your center matches the mains on alignment. I simply prefer having flexibility.

That is good to know. I mistakenly thought that it would be very important to make the alignments match.

-Max
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post #8 of 42 Old 12-07-2012, 11:50 PM - Thread Starter
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I haven't done any testing of putting an existing speaker in the fireplace to see if the distance from the screen bothers me or not, but screw it; I'm going to build the center speaker anyway. I already have the waveguide/woofer/CD, and I like building stuff. If the distance bothers me, I'll lower the TV since I won't be burning anything in there.

I am also thinking that I will build a sealed speaker for the center, since the enclosure starts to get big when ported. Fitting a big enclosure into the fireplace would require an odd shape, and I'd like to avoid that. I don't know whether I will build the L and R sealed or ported, but I'm glad to hear that choice doesn't need to drive the center channel design.

I have read that 2.5-3.0cf is a good volume for a sealed TD15M enclosure. However, I want to better understand why. My lack of Windows computers is slowing me down a bit here, as I think that I should just download WinISD Pro and play with the design to get that understanding. I'll figure something out and do that soon.

Jumping ahead a bit, I've been thinking about the enclosure dimensions and how I should choose them. For ease of construction, I plan to build a rectangular box. I can tilt it up slightly by placing something under the speaker, rather than building a slanted baffle. It looks like I will be tuning the crossover myself, so I don't have a specific target width in mind. I will start active with bwaslo's minidsp settings as a starting point, and then will most like build passive crossovers so that I can power the speaker with my receiver. But anyway, I don't have to stick to the same width as the designer's speaker.

From what I gather, this isn't necessarily critical, but using the Golden Ratio to choose dimensions sounds like it can help minimize standing waves in the box. The Ratio is interesting and I don't have any other guides, so I might as well give it a try. The Golden Ratio is ~1.618, so for instance you could make the interior depth 10", the interior width 10*1.618 = 16.18", and the interior height 1.618*16.18" = 26.18". However, that results in a working volume of just 2.45cf, and it is already taller than I can fit in the fireplace. Hmm... that just isn't going to work for my fireplace speaker, though perhaps I will try it again for the L and R later.

So I did some calculations for 1.414, which was mentioned as another "sacred ratio" in this thread and which I visually verified to be "special" on this page, and that turned out much better. For instance, using a double-thick baffle, a cabinet with external dimensions of 26.625"h x 19.25"w x 14.75"d has a total internal volume of 3.27cf, which is in the ballpark of 3cf once the driver, waveguide, and brace volumes are subtracted. 1.414 is perfect for my fireplace speaker.

I'm going to back up and build a working understanding of what volume I should be targeting, and then I'll probably use the 1.414 ratio to choose some cabinet dimensions.

I found 3/4" Arauco plywood in stock at a nearby Home Depot. Or at least it says it's in stock on the website, and it isn't a far drive to verify. So I plan to pick up a few sheets this weekend, hopefully. smile.gif

-Max
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post #9 of 42 Old 12-08-2012, 11:10 PM - Thread Starter
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Score! A Home Depot near me did indeed have Arauco 0.703" plywood, so I picked up a sheet today.
http://www.homedepot.com/h_d1/N-5yc1v/R-202519005/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=cabinet+grade+plywood&storeId=10051#.UMQ3889QDnY

On to WinISD fiddling...

I was able to install WinISD Pro and run it under Wine on Linux. So far I haven't noticed any problems whatsoever. It just works. Yay!

To start understanding what I was doing, I decided to play around with models for the Econowave SR speakers that I built in 2011. I have measured my SR speakers in the past and found that the response begins to drop off slowly below 200Hz, and is down several dB by 80Hz. Cerdic and Mrkazador were helping me with the port in my build thread, and thankfully convinced me to build them ported. But I didn't understand enough of what they were telling me to make a smart choice about the port length, so I sort of picked it haphazardly. Playing with WinISD tonight has convinced me that I should cut the ports down on those speakers. Check it out:



Driver excursion and port velocity don't show any problems with the shorter port. So shortening the ports on my Econowave SRs is now on my TODO list. I'll try to measure the before/after response of the speakers with REW to verify the model.

But I'm going to press on with designing the cabinet for my SEOS-15/DNA-360/TD15M center speaker first. The TD15M was not in the driver library that ships with WinISD Pro, but I found a thread that has driver info for many different drivers, including the TD15M:
http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/14410-downloadable-winisd-pro-files-2.html#post264170

-Max
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post #10 of 42 Old 12-09-2012, 07:50 AM
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Did you measure your Econowaves away from boundaries? If so, that is likely why you experienced that roll off around 200hz. I don't believe the Ewaves were designed with baffle step compensation. They are generally best used near a wall or corner and would measure flatter closer to a wall.

If possible, I would suggest building your enclosure vented. You can then plug or unplug the port to see which gives you the best response in room. A sealed TD15M will generally work well down to ~80-90hz. A vented TD15M is probably best tuned to around 35-40hz. What subs are you using and where are they located?

I wouldn't worry much about golden ratios with box dimensions. Just build it to fit your space. You simply need to avoid long skinny boxes that can act like a pipe. You should also line the box with something like cotton insulation.
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post #11 of 42 Old 12-09-2012, 09:29 AM
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Quote:
Originally Posted by maxcooper View Post

Oh, I see that now. And judging by the relative size of the woofer and waveguide recesses, that must be the SEOS-12. The SEOS-15 is 15.5" wide, which would be wider than the woofer recess.
I wasn't actually planning to order that, but rather I was just using it for size reference.
That is good to know. I mistakenly thought that it would be very important to make the alignments match.
-Max

I just did a sealed TD15M box in WinISD and got a max flat Qtc .707 box right at 3cuft (87liters) that looks about ideal. -3db is ~80hz. That looks good for a center I'd think.

JoshK on most other audio forums
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post #12 of 42 Old 12-14-2012, 12:03 AM - Thread Starter
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Quote:
Originally Posted by coctostan View Post

Did you measure your Econowaves away from boundaries? If so, that is likely why you experienced that roll off around 200hz. I don't believe the Ewaves were designed with baffle step compensation. They are generally best used near a wall or corner and would measure flatter closer to a wall.

I measured my Econowave SR in the position you see in the first pic in this thread. It is on a chair with the baffle roughly 30" from the wall behind, but next to the fireplace. The front edge of the cabinet is 5" in front of the fireplace. I'm not sure how much of that matters, but I guess I would call that "away from boundaries". I'm also not sure it matters since I used a gated measurement in REW. The mic was 1m in front of the speaker. I found a pic of my measurement graph:



There's some weird stuff going on in that graph, though I'm not really sure how to diagnose and correct the problems (assuming the measurement is accurate).
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Originally Posted by coctostan View Post

If possible, I would suggest building your enclosure vented. You can then plug or unplug the port to see which gives you the best response in room. A sealed TD15M will generally work well down to ~80-90hz. A vented TD15M is probably best tuned to around 35-40hz. What subs are you using and where are they located?

Building vented and then plug or not-plug sounds like a good strategy, but it's going to be a lot easier to fit a sealed cab in the fireplace, so I'm leaning toward sealed for this build. I'll play with the dimensions for ported one more time before I commit to sealed, though, based on your feedback.

For subs, I have a single THT LP in the front corner of the room. You can see it in the top right corner of the first pic in this thread. It is vertical, firing up. And it's white but looks cream in the pic. It has a 6' strip of bacon painted on it, too. biggrin.gif
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Originally Posted by coctostan View Post

I wouldn't worry much about golden ratios with box dimensions. Just build it to fit your space. You simply need to avoid long skinny boxes that can act like a pipe.

I realize that the ratios are not that critical to performance, but I like the idea as a constructive constraint, and it seems like a "free" optimization.
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You should also line the box with something like cotton insulation.

I know where to get polyfill, but where do you get cotton insulation?

Thanks,
-Max
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post #13 of 42 Old 12-14-2012, 12:14 AM - Thread Starter
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Quote:
Originally Posted by AudioJosh View Post

I just did a sealed TD15M box in WinISD and got a max flat Qtc .707 box right at 3cuft (87liters) that looks about ideal. -3db is ~80hz. That looks good for a center I'd think.

That's what I got in WinISD, too. I am glad that we got the same results. biggrin.gif

Here's a comparison of sealed vs. ported for the TD-15M. Sealed volume is 3.059cf, and ported is 5.153cf with a 4.02" diameter x 2.54" long port (WinISD picked the box and port dimensions, which seem optimized):


-Max
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post #14 of 42 Old 12-14-2012, 04:34 AM
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Max-

I can get cotton insulation at Menards near me (big box store in midwest). I'd imagine it is more available in CA given it is a "green" building material. Polyfill and regular pink fiberglass insulation work well too. I prefer cotton insulation because it performs a bit better than polyfill and doesn't blow nasty fibers into the air if the box is ported. If it is sealed you can just go with fiberglass.

If sealed is easier to pull off in your spot you can definitely do that. You should be able to make it work and a F3 of ~80hz should allow it to be high passed from 60-80hz in your receiver.
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post #15 of 42 Old 12-15-2012, 03:44 AM - Thread Starter
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Quote:
Originally Posted by coctostan View Post

Max-
I can get cotton insulation at Menards near me (big box store in midwest). I'd imagine it is more available in CA given it is a "green" building material. Polyfill and regular pink fiberglass insulation work well too. I prefer cotton insulation because it performs a bit better than polyfill and doesn't blow nasty fibers into the air if the box is ported. If it is sealed you can just go with fiberglass.

I'll check my local stores. I thought it might be audio-specific, but I'm glad to hear that it is a common building material.
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If sealed is easier to pull off in your spot you can definitely do that. You should be able to make it work and a F3 of ~80hz should allow it to be high passed from 60-80hz in your receiver.

I did run the enclosure size numbers again, but ported would have been a pretty tight squeeze in the fireplace, and would have been a weird shape, too. So I went sealed.

I started making sawdust tonight. Here's the double baffle gluing up:


Now that I have cut some panels and see how big they are, this speaker is going to be pretty big.

I've been looking at the bracing of Erich's flat packs for design inspiration, but my bracing will likely be much simpler. I enjoy the building process, but it really makes me appreciate how good Erich's flat packs are (excellent bracing, super convenient, great prices).

-Max
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post #16 of 42 Old 12-17-2012, 03:11 AM - Thread Starter
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A little more progress:

I cut the woofer recess and hole tonight. I cut the recess on the front side first, which took a few passes at different diameters. I also made a final pass on the front at the cutout diameter at full depth. But the baffle is too thick for me to cut from one side, so I finished the hole off from the back side. I didn't do anything to hold the center in place, but it only gouged the flange a little bit. In hindsight, though, I probably should have done something, such as cut it out on a rug mat, for safety and less sloppy results. Here's a pic of the recess and the final cutout:




Then I did a test-fit of the woofer. I did the cut using the dimensions off the engineering drawing. I cut the recess diameter at 15 5/8", which is a little larger than the driver, to give enough gap around the edge to easily slide it into place. I cut the hole equal to the 14" dimension from the engineering drawing. After the cut, I wondered if I should have made the cutout a little bigger, but upon test-fitting the driver, 14" turned out to be perfect, so I'm glad that I didn't increase that dimension at all. The recess diameter turned out to be a good size, too. I will use the same sizes (15 5/8" recess, 14" hole) when I do the left and right speakers.



I'm still waiting for the phase plug for the TD15M, but I'm not letting that slow me down. If I finish the speaker before the phase plug arrives, I'll just run it like that until it arrives.

I got a SEOS-15 waveguide out, too, to mock it up to see what the speaker is going to look like. This is going to be a fairly large speaker (26.8h x 19.4w x 14.8d) and it really feels large in person.



I'm not sure if I'll have time to do it before the holidays, but next I will be making a router template for the SEOS-15 using the method described here:
http://www.exquisiteaudio.com/baffle.html

-Max
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post #17 of 42 Old 12-29-2012, 01:59 AM - Thread Starter
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I cut the recess and hole for the SEOS-15 in the baffle today.

To cut the recess, I followed these basic instructions:
http://www.exquisiteaudio.com/baffle.html

The first challenge was holding the waveguide in place to cut the template. I ended up putting a long bolt through the throat of the waveguide. First I taped over the face of the waveguide to protect it from scratches. I just taped the front, but left the edges bare so that the router plate would ride directly against the edge of the waveguide. I used some 3/8" threaded rod instead of a bolt, since I didn't have a bolt that was long enough. I used the centering cone from my router to center the bolt in the waveguide. It doesn't really matter if it is centered, but I figured that would protect the waveguide and hold it tight. I carefully aligned the waveguide to be square with the template stock, and then tightened it down using a wingnut.

Before the cut:


This was after the cut, but shows how I held the waveguide in place:



The first cut is a plunge cut with a 1/4" bit to create a "throwaway" template. It is important to hold the router base plate tight against the edge of the waveguide for this first cut. I was using a backing sheet of plywood that happened to have a hole in the middle, which is not ideal, but I was careful at the end of the cut to keep the edge smooth as the center "broke loose". I also checked the template after the cut, and had to sand it a little bit to smooth out the end of the cut. It would be better just to use a full sheet of plywood for the backing so you don't have that problem. The waveguide held tight, and the cut turned out excellent:


You can see how the spiral upcut bit leaves a feathered edge, but they clean right up with minimal sanding, leaving a really nice template edge.

Cutting the hardboard seemed to make nasty dust. I usually don't use a dust mask when cutting wood, but I quickly put one on after my first cut of the hardboard. It just felt like I was breathing something that I shouldn't. I wasn't using dust collection for these cuts, since I installed the router guide holder in the plunge base, which prevents installing the dust hood. Maybe part of my impression here was due the lack of dust collection. Man, I really miss the dust collection.

The next step is to use the "throwaway" template to cut the real template. I clamped two pieces of hardboard together, and ran around the inside of the throwaway template with the 1/4" bit:


After cleaning up the edge, I took some time to position the template onto my baffle. This was a bit complicated due to the fact that I am using a double baffle, and the smaller "backside" half of the double baffle is the positional reference. I cut the "frontside" baffle a bit large and will trim it to fit with a flush trim bit once the box is built. But I was a bit sloppy in gluing the two baffle pieces together, so they aren't quite square with each other. I was eventually able to get a centerline on both the template and the baffle, and that was all I needed to line the template up. I'm leaving just 1/4" between the woofer recess and the waveguide recess. The template happens to be 1/4" larger than the waveguide all the way around, so I lined up the edge of the template with the edge of the woofer recess. Blah, blah, blah, here it is:


I installed a 3/4" router guide, and together with a 1/4" bit and the template, I ended up with a cut that is the same size as the waveguide. The edge of the waveguide is a little more than 7/16" thick, so that's how deep I cut. The template worked great for making the 1/4" wide groove at the edge of the recess, but I obviously needed to cut a wider recess. I didn't have any other guide+bit combinations that would help me widen the recess, so I removed the template and just started to "freehand" the rest of the recess with the 1/4" bit. But then I started to think about how I was going to do the cutout. I decided to use my jigsaw. First I looked at the waveguide to determine how wide the recess should be, and I decided on 1/2" for the top and bottom, and about 1.25" for the sides. I penciled in some lines on the baffle. And then drilled a 1/2" hole to give myself a starting point for the jigsaw. You won't see the cutout in the final speaker, so I wasn't very careful making the cut.


Hole!


Then I went back and finished cutting the recess using my router. I could have switched to a wider bit, but I kept using the 1/4" spiral upcut. It took a little while, but eventually I finished. After sanding away some feathers by hand, I was left with this recess + cutout:


Finally the moment of truth... test-fitting the waveguide. It fits -- quite well, in fact:


That template technique is pretty easy to do and it worked perfectly. I'm really happy with the results.

-Max
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post #18 of 42 Old 12-29-2012, 01:33 PM
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Nicely done!

JoshK on most other audio forums
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post #19 of 42 Old 12-29-2012, 02:06 PM
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Cool, could I please get a photo of a person standing beside one ? Difficult to get an idea of the size.
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post #20 of 42 Old 12-30-2012, 10:03 PM - Thread Starter
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Cool, could I please get a photo of a person standing beside one ? Difficult to get an idea of the size.

It's just me and a cell phone, so I wasn't able to get a pic of me with the speaker baffle (even though I know that would be easier to grok), but here's a pic with some other common objects for size reference:


I also installed some hurricane nuts to mount the driver. I know that many experienced builders have had bad experiences with them -- bad threads or insulation caught in the threads leading to spinning a nut. But I am very careful to epoxy them in place, and avoid getting any epoxy on the threads, or chase the threads with a tap if they aren't nice and smooth.


I was planning to just glue the waveguide in place once I finished the speaker. But now I'm planning to run it unfinished for a while, so I don't want to glue the waveguide in place yet. I need another way to mount the waveguide. I want to keep the appearance as clean as possible, so I don't want to drill screw holes. So, my plan is to make a small wood block, recess a 1/4" carriage bolt in it, sand down the surface to make it flat, and then epoxy it to the back of the waveguide. The wood block will give some extra surface area for the epoxy to grip. I'll put one bolt in each corner of the back of the waveguide. The corners have enough flat surface to avoid having to shape the wood block much, or maybe not at all. Then, I'll use some 1/2" plywood to clamp the back of the baffle. I'll use a little weatherstrip to seal the waveguide, and maybe also between the brace and the back of the baffle, to be sure that it won't "rattle" at all. I'll use a washer and nylon lock nuts to ensure they they don't work loose.



-Max
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post #21 of 42 Old 12-30-2012, 10:11 PM
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thanks
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post #22 of 42 Old 12-31-2012, 03:22 AM - Thread Starter
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I started putting my waveguide mounting plan into action tonight.

I found some nice off-cuts in my scrap bin and used a Forstner bit to cut a little recess for the carriage bolts:


Next I drilled the hole for the carriage bolts and tapped them into the wood blocks before cleaning them up on the disc sander. After test-fitting, I ended up shaping the surface slightly using the belt sander to better match the back of the waveguide.


I traced the outlines onto the back of the waveguide, and lightly hit it with a hand sander to rough up the surface:


I looked at the various epoxies for sale while I was at Lowe's today, and JB Weld had the highest strength and said that it would bond to just about anything. I already had some at home, so I mixed up a bunch, slathered it onto the stud blocks with an old butter knife, and pressed them into place.


To keep my assistant from messing up the job, I draped a rag towel over the waveguide and studs. And now it is just a waiting game.


I cut the sides tonight, and started to design the bracing before I ran out of steam. I'm having a hard time deciding what to do about the bracing. I want simple, but it would also be nice to have bracing that helps me glue up the cabinet. I'll try again tomorrow.

-Max
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post #23 of 42 Old 12-31-2012, 05:53 AM
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Quote:
Originally Posted by maxcooper View Post

I cut the sides tonight, and started to design the bracing before I ran out of steam. I'm having a hard time deciding what to do about the bracing. I want simple, but it would also be nice to have bracing that helps me glue up the cabinet. I'll try again tomorrow.
-Max

Cutting dadoes into the top, bottom, and sides for a window brace can make the box stable for glue up. Then you have the option to brace the front & back to the window brace or each other.
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post #24 of 42 Old 01-02-2013, 05:00 AM - Thread Starter
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Before gluing the cabinet together, I finished my waveguide mounting setup. The epoxy dried on the waveguide studs, and they seem pretty strong. So next I made some plates from 1/2" plywood scraps to clamp against the back of the baffle. I didn't notice until after I was finished, but the wood grain is going the wrong way on my clamp plates. They seem to work fine, however, so I'm going to stick with them anyway. I did not control the stud positions carefully when I epoxied them, so I held the clamp plates on the ends of the studs and tapped with a hammer to mark the stud positions so that I could drill the holes in the right positions. I also marked the plates and the studs, since the plates are not interchangeable from side to side due to non-uniform stud positions. I drilled the holes one size larger than 1/4" to avoid binding during installation. Fortunately, they slip right on without any fuss. I need to seal the waveguide to the baffle, so I installed 1/4x1/2" high density gray foam weatherstripping around the edge of the waveguide. This foam is highly compressible, and is very easy to bend around the corners on the waveguide as long as you remove the backing paper as you work. I also installed some foam pads of a less compressible foam on the clamp plates, so that there would be foam on both sides of the baffle. I did a test-fit and it works very well.



I stated thinking about how I was going to glue up the cabinet, and I found a way to do it all in one shot. Dadoes would be cool, but I don't have a table saw handy and doing them with a router is too much work. So I had to think up something simpler. I had already glued the double-baffle with smaller inner baffle, so I laid the baffle face-down. The back is the same size as the inner baffle, and so would just fall in if not supported. So to hold it up I just cut four pieces of wood to hold up each corner, to be removed after gluing. Here's a pic of the supports (after gluing):


Before gluing, I did a dry fit and installed clamps to work out a plan:


It is getting pretty cool in the garage, so I put the glue in the house yesterday to warm it up. I also used a radiant heater to try to put a little heat into the wood.

And then I just glued it all up with Titebond 2, installed the clamps, and used a warm, wet towel to wipe off the squeeze-out and drips:


I did end up with one joint that had just enough gap that it didn't seal completely at one end. I think my cut was just slightly out of square, which tends to happen since I seem to forget that plywood sheets don't come perfectly square, even though I know better. I squished in more Tightbond twice to strengthen the joint, and ultimately "caulked" it from the inside with PL Premium when I was gluing the supports inside the cabinet. The rest of the joints were all nice and tight.

Another mistake was that I had the inner/outer out of alignment enough that the outer baffle didn't quite reach the edge in two places, despite the fact that I cut the outer baffle large (to be flush-cut after gluing). I guess I should cut the outer baffle even larger, or be more careful with the alignment next time. I plan to use Bondo to resolve the problem. I also realized that I used a slightly non-parallel strip of wood to align the waveguide recess to the inner baffle, with the result being that the waveguide is just slightly out of square, relative to the box. The misalignment is very slight, and this speaker will be all black and sitting behind a fireplace screen, so I'm not too worried about it. This whole cabinet is less than $30 worth of wood, and I feel like I am learning from the experience, so I'm not too worried about any of these mistakes.

After about 20 hours, I removed the clamps. I did a little inspection and sanding to prepare for the flush-cut bit, and then trimmed up the oversized panels with the router and flush-cut bit. Then I switched to the 1/4" radius round-over bit and did all the edges.


I decided to use "stick" cabinet braces, mostly because I already had some sticks and thought it would be easy. I came up with a plan, cut some additional sticks and two supports, and then did a test-fit:



Once I was satisfied, I used PL Premium to glue the braces to the cabinet and to each other. I used PL Premium because it expands and would help ensure that my supports were making a solid connection to the cabinet.



So now I have a cabinet, almost ready to load:


I plan to run the speaker unfinished for a while, and use a MiniDSP and separate amp channels for the 2 drivers. I guess I could temporarily just drill a hole, run 4 wires through it, and seal it up with a little museum putty or something. But after looking at various binding post options, and realizing that I don't want to install 4 binding posts, I ordered a Speakon connector. It is 4-pole, which should would out nicely during the active phase, and is easy to just use 2 poles once I build a passive crossover.

I was able to pickup a big package of denim/cotton insulation at my local Lowes, too, so I will be using that for stuffing. There's enough of it that I'll probably stuff my Econowaves with it, too, since they currently have just a small amount of polyfill in them. And there's probably enough to stuff many more speakers after that, too. smile.gif

I expect to have the speaker working this week, and I'm looking forward to hearing how it sounds and playing with some new gear (MiniDSP, new amp, new MiniDSP microphone setup).

-Max
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post #25 of 42 Old 01-02-2013, 05:10 AM - Thread Starter
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The external size is: 26.8"h x 19.4"w x 14.8"d

I know, weird numbers, but that's what I came up with using the 1.414 ratio. And I just did the best I could with the measurements while cutting. I tried converting the measurements to metric, but quickly realized that I don't have the layout tools for metric. It turned out okay, but it would have been a little easier to use more "normal" measurements.

-Max
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post #26 of 42 Old 01-07-2013, 07:53 AM
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Quote:
Originally Posted by AudioJosh View Post

I just did a sealed TD15M box in WinISD and got a max flat Qtc .707 box right at 3cuft (87liters) that looks about ideal. -3db is ~80hz. That looks good for a center I'd think.

Josh,

What would those numbers be for a critically damped box (Qtc 0.5)?

Thanks
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post #27 of 42 Old 01-07-2013, 10:47 PM - Thread Starter
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I finished the speaker on Friday, and I've been listening to it all weekend. Well, not "finished", really, since it doesn't have a finish on it, and the wires are just coming out of a hole and sealed with museum putty until I get a smaller circle jig to cut a recess for the Speakon connector. This is my first time messing with Speakons (on the amp side), and so far I really like them -- much better than sloppy banana plugs. I also stuffed the speaker with the cotton/denim insulation, and I really like that stuff, too. I used one of the five strips that came in the huge R19 pack I bought, and could have used a little bit more. I felt like I got a ton of that stuff, but maybe I'll use it up faster than I expected.

Here's the speaker, along with an Econowave SR and my THTLP "bacon" sub:


It sounds good, but I feel like it is hard to tell without another one to use for music listening. About the best test that I've had so far is a few listenings to Dark Side of the Moon in 5.1. Having the single speaker really, really makes me want to have two. Comparing it to my Econowave SR, I'd say that the high frequencies are smoother -- I really like my SRs, but they are a bit "edgy" sometimes. My new speaker is not edgy. If I was writing an audiophile account, I would say that the bass has more texture and weight, too. :-)

I'm currently running it active with an unbalanced MiniDSP and a Behringer iNuke 3000DSP. I used BWaslo's settings -- huge thanks!!! I did some quick measurements to verify the gain settings on the iNuke, and the settings I dialed in by ear looked spot-on. The measurements show an even frequency response, for the most part, as expected, though I'm still working out some kinks in my measurement setup, so I don't want to post graphs yet. I'm having trouble measuring bass, I think due to using an HDMI connection to the receiver -- like it takes a moment to sync and misses the beginning of the sweep. Phase looks insane, too, but I'm not sure what to expect.

I don't really notice it much from my listening position, but if you get a little closer there is very audible hiss coming from the horn. It's pretty loud, and not something that I want to live with forever. I'm curious to try a linear power supply for the MiniDSP (or maybe a battery, just for kicks) instead of the switching USB supply that I'm using now. I've also got a balanced MiniDSP that I could try, though my receiver's pre-outs are unbalanced so I doubt it will make a big difference. I might also try the DSP inside the amp, rather than the MiniDSP. The comparative lack of hiss from my similarly-high-sensitivity Econowaves suggests that a passive crossover might be my ultimate solution.

Overall, I'm happy and really excited to make the L and R now, so I can really hear what these sound like.

-Max
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post #28 of 42 Old 01-08-2013, 06:00 AM
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By Maxcooper-"I didn't notice until after I was finished, but the wood grain is going the wrong way on my clamp plates."

Plywood alternates the grain on every layer, so it will not make much of a difference. The alternating of layers is what helps keep plywood stable. Wood wants to swell across the grain and the alternating layers glued together, help keep it from being able to do so.

Nice looking speaker. I think once you listen to it (them) more and more, you will appreciate them even more.

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post #29 of 42 Old 02-27-2013, 04:47 PM - Thread Starter
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I'm so dumb. tongue.gif I made the speaker too tall to fit in the fireplace. I didn't measure the fireplace opening correctly.

New plan: though I find that I don't mind the distance between the screen and center speaker that much, having it higher would still be better. So I'm planning to build a taller version of the center speaker, and maybe so something funky so that it covers the fireplace opening completely. (The fireplace has to be covered to keep the cat out.) So, maybe narrow at the top, and expanding out to the fireplace width early enough to cover, with angles or even curves.
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post #30 of 42 Old 02-27-2013, 08:10 PM
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Max, I made a plate for my fireplace out of MDF and used some chair railing to trim the outside edge as well as installed handles for ease of removal.



Ignore the construction.
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