My first design...please critique (1 Viewer)

[Bill Catherall]

Well...I finally came up with a design that I like and also has a good SAF. The reason the SAF is higher on this design is because it can hide in the corner behind the couch. We have a sectional that has a curved corner piece. This leaves a sizeable unusable area behind the couch. I was thinking that if I make a subwoofer that fits back there then the wife might not object to it. So here it is:
A front view.

A back view with a side removed so you can see the inside.

You can see all the design specs by http://wcatherall.homestead.com/files/subwoofer/sub.html I'd rather be wrong now than after I spend the money.
Also, I have no idea what the actual dimensions of the flare are so I had to guess. What is the mounting hole size for a 6" flare? I plan on putting a grill over the vent to keep the kids from putting things inside. I know that's where all the toys and even food will go if I didn't.
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Bill

 

[Philip Hamm]

Boy, that looks really nice to me. Please keep us informed as you build it with pics and information. I've never seen a sub like that. Where are you going to put the speaker terminals?
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Philip Hamm
AIM: PhilBiker

 

[Patrick Sun]

Nifty design. Just pay attention to the bracing, and creating an airtight seal around all those sharp joints at the vertices.
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PatCave; HT Pix; Gear; DIY Mains; DIY CC; Sunosub I + II + III; DVDs; Link Removed

 

[Jack Gilvey]

Looks great to me, Bill. Nice job.
quote: The back of the couch will sit about 1" away from the Tempest. Will that present any problems?[/quote]
I'd think that a couch should be more or less acoustically transparent to these frequencies, but maybe a little more more clearance would be in order. Might depend on the couch...not too sure on that one.
quote: The material is 3/4" MDF. Should I make it thicker?[/quote]
I'd either make it a bit thicker, or go with 3/4" no-void ply like Baltic Birch or marine ply. http://www.hometheaterforum.com/uub/Forum17/HTML/002655.html
[Edited last by Jack Gilvey on October 03, 2001 at 07:55 AM]

 

[Bill Catherall]

Thanks for the replies. To answer some of your questions...

Please keep us informed as you build it with pics and information.

I hope I can get to build it soon. Right now my budget is my biggest constraint. Also, I'm lacking in a few essential tools that I need to get anyway. It might be a few months before I can even start. Meanwhile I plan to lock down the design to make sure I'm absolutely happy with it, and confident that I'll be spending my money wisely. I would build a Sonotube sub, but until I have a dedicated room for home theater, I have to keep things looking "normal" in the living room. By the way, this sub will be used 95% for movies. Actually I really never listen to music, so it's going to be more like 99% movies.
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Bill

 

[Jack Gilvey]

I went with a 6" port because the air speed in the port went up too high when I was using a 4" port. Where can I find 6" port kits? including the flares?

And I think that's a good idea, especially given the top placement of the port in relation to the couch. I got my 6" flares Link Removed

 

[Bill Catherall]

Thanks Jack. I'll look around for a marine ply supplier and get some prices.
What if I don't flare the port? What difference will it make?
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Bill

 

[Jack Gilvey]

With no flare, there's more potential for some port noise.
With a plate amp like the AVA250 , though, I doubt it would be an issue. People are even using 4" flared ports with that combo with success. You'd probably be ok without it, but there's no reason not to do a roundover like I described. I only stressed it because of the location of the port, which seems to be within a few unobstructed feet of listener's ears (I'm assuming, of course).
The marine ply I just got ran about $53 for a 3/4" sheet.
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[Patrick Sun]

I would not flare a 6" port for this application.
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PatCave; HT Pix; Gear; DIY Mains; DIY CC; Sunosub I + II + III; DVDs; Link Removed

 

[Jack Gilvey]

This sub was just posted to the basslist, thought you might find it interesting.
[Edited last by Jack Gilvey on October 03, 2001 at 01:09 PM]

 

[Bill Catherall]

I would not flare a 6" port for this application.

Hey Pat, you're so verbose on your web site. Why the sudden silence?

While it would be much cheaper and easier for me to avoid the flare, can you give me a reason? (You've probably stated it somewhere before, but I've missed it.)
Also, will having the port located so close to the sides be a problem? I located it there because I wanted to pull it as far back from the listener as possible and also to make room for the driver if I wanted to mount it higher up (like in the middle). I dropped the driver down low to not only make the sub more stable (I didn't want a high center of gravity) but so that it wasn't directly behind the listener's back when sitting in the corner.
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Bill

 

[Fred Seger]

I agree with Pat. (IMO) The airspeed in a six inch port is going to be low enough that you shouldn't have to worry about port noise. But then again my hearing isn't the best...
Just my 2 cents.
[Edited last by Fred Seger on October 03, 2001 at 03:48 PM]

 

[Jon Hancock]

Hi Bill,
Looks like you've got an interseting project on your hands!
A friend of mine in Denver and I built a similar design speaker, using a Stryke HE-15 woofer, though. However, that enclosure was similar in acoustical concept to yours, and it would work with the TEMPEST.
Regarding the ports, by all means go with the flared port design- we did. It cuts the port noise at high playback levels, and seems to allow linear port operation to a somewhat higher acoustic output. We had a bit of a hassle finding someone that made 6" port flares, but finally found a vendor in Texas; they were about $50 for a set. If you already have them located, and particularly if they're cheaper, all the better. Otherwise, let me know if you need the address for our source for the flares.
Your general concept for cabinet construction is good- we were actually building something to "klone" an Aerial SW-12, but scaled up to a 15", with an internal volume of 160 liters. We installed the wall brace panels about every 6" along the length of the cabinet. The front panel was built up from three layers of 3/4" MDF. Also, the outer wall was 3/4" MDF, but between each brace layer was an inner wall of an additional 3/4" MDF. The finished box is pretty heavy, but it's not absolutely dead, vibration wise, when you start pushing it- but probably dead enough.
Last, I'm guessing from your design that you're planning on putting this in a corner. And the driver will be rather close to some listeners. If at all possible, I'd reconsider this. For a good explanation why, see the article on room acoustics and sub positioning in the October 2000 issue of Stereophile Guide to Home Theater. It may be available on the web site, I don't know. It explains very succinctly the interaction between various room placements and listner posisitons, due to both boundary interactions and room modalities. You can also do this kind of analysis with RPG Acoustics Room Optimizer software; it's one of the best $100 I've ever spent for optimizing room and speaker placement and setup. In the article, they show how the typical corner placement interacts with room modes for various seating positions (re total flatness through bass region), and also give locations for placement of up to three subs to achieve flattest in room response at the widest number of listening positions. Corner placement, though giving high bass output at some frequencies, also gives the most irregular response at most listening positions. This is a must read article for anyone hoping to get the most out of a subwoofer in a music or HT system, particularly if they're having placement problems.
Best regards,
Jon

 

[JerryD]

Jon,
The RPG Acoustics Room Optimizer software sounds very interesting. I found this web site for it:
Link Removed
Maybe you could answer a question about it for me that the web site did not seem to cover... Does it work with non-rectangular rooms? My room is "L"shaped and has multi-level risers for the seating and some sofets on the ceiling. I've not found anything that works on other than perfectly rectangular rooms.
Regards,
Jerry

 

[Jack Gilvey]

Bill, Link Removed
Jon, a question on the flares, if I may: How would using just one of them, the "outside" one, compare to dual flares, or none at all?
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[Bill Catherall]

Thanks for your input Jon. And thanks for the link Jack. How important would it be for me to support the lower end of the vent in my design? Right now it's just hanging free.

I'm guessing from your design that you're planning on putting this in a corner. And the driver will be rather close to some listeners.

Yes. The basic driving element of this design is to hide it in the corner right behind the couch. That's probably the biggest flaw in the design so far. It's designed with a specific location in mind, and that location isn't very ideal. My room isn't very acoustically sound anyway. I've got an 8 ft wide sliding glass door taking up most of my right wall. That causes all kind of terrible acoustical problems. I didn't really realize how bad it was until I took some SPL readings of various frequencies and the results were all over the place. But I did notice that I was severely lacking in the low end frequencies.
I have some tower speakers that look like they can go low (they have big drivers) but they just don't. And for what I paid I'm really not surprised. I plan on replacing them in the future with some Kit281s from Adire, but meanwhile I'd like to fill in that lacking low end.
The biggest problem in my room is sub placement. I don't really have anywhere to put one. Of course, this could change in the near future. The home we have is just a "starter home" for us. Even though this sub will be placed behind the couch in this room, it may end up in a front corner sometime in the future.
Again, thanks for everybody's input. I'm soaking it all in and improving the design as we go along.
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Bill

 

[Chris Eriksen]

Hi Bill,
Nice looking design. However, there is one thing that you may have overlooked. Will it be backed into a corner, with the 'sides' butted up against the walls? If so, your choice for the amp location may not allow for sufficient cooling. Otherwise, I think it looks good.
PS: Are those Pro/E drawings? I love that CAD package.
[Edited last by Chris Eriksen on October 04, 2001 at 08:48 PM]

 

[Jon Hancock]

Regarding the port flares, you really should use them at both ends- it is necessary to avoid chuffing from turbulence at the port entry/exit.
For large, long ports, it's desirable to support them along the length. The "ideal" thing to do is to use an internal baffle with the internal flare supported by the baffle.
Yes, unfortunately Room Optimizer is designed to work with rectangular rooms. It could be worhwhile, though, to use some simplifications to approximate your listening space and see what comes up anyway. If you can model at least three walls somewhat accurately, it will probably be worthwhile. One program that does do irregular room modeling is Bodzio software "Sound Easy", this is actually a speaker design package, but it includes room analysis. It doesn't have a listening posistion optimizer like the RPG software.
In a complex situation, I recommend using the Wilson approach- put a speaker in the listening position, then listen in the positions where you think you want the speakers, listening for flattest overall response - or measure if you have the equipment, using an RTA.
Regards,
Jon

 

[Bill Catherall]

Thanks again Jon.
Chris, the amp placement has been bugging me too. I don't plan on putting the subwoofer all the way up against the wall because I don't want it be in contact, but having the amp there will force me to have it at least 2" away. That's going to be a problem. I've thought about moving the driver up and putting the amp down in the front under the driver. That would make for really easy access, but might be ugly if I ever move the sub to the front of the room. Or...actually it might look pretty cool. I'll have to try it and see how it looks.
Nope...not Pro/E. I use Pro/E at work, but these models were made at home on SolidWorks. I have...ahem...demo copies of both SolidWorks and Pro/E at home, but Pro/E doesn't work so well on my computer. I think I have a troublesome graphics card. SolidWorks is a lot easier to use than Pro/E, but no where near as powerful. It also costs about $8000 less! I really prefer Pro/E, but SolidWorks is do-able in a pinch.
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Bill

 

[Carl K]

Bill - it's nice to see someone else planning along the same lines.
Couple of questions - how did you paste your Solidworks drawing into this page? I couldn;t seem to get it to work. Also, as a novice SW user, could you send me your design tree so that I might follow your design steps? I'm not sure how to proceed to get the braces in.
Nice model of the Tempest. My design is similar, about 145L, with a 4" port above the Tempest, and a back wide enough to mount the AVA250.
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