Sealed DIY sub questions (1 Viewer)

[BrianMu]

After being talked into a DIY sub as opposed to a cheap Sony, (see this thread) I'm ready to get into the design process.
I'm planning on running over to PE to pick up the 300-794 plate amp while it's still on sale for $125. Can everyone agree that this is the best I can do for this price as far as an amp is concerned?
As for a driver, I was planning to use the Dayton 12" DVC as recommended by Jack Gilvey. In fact, I was planning on making a sub very similar to the sub Jack made (see this thread). After re-reading that thread though, I read where Jack said:
"Comparing the Dayton DVC with the Shiva (both of which I own)in a sealed box ,it looks like the Dayton needs a smaller box for a given Qtc, but the Shiva will go a bit deeper for the same Qtc (in a larger box). Either woofer has excellent excursion, power handling, and SPL capabilities.
If you wanted something very small, the DVC is excellent. If you can go to a net 2.2ft^3 or so, I might opt for the Shiva."
This is directed mostly at Jack, but anyone who has an opinion, please chime in: Do you feel that a 2.2 cf box with a Shiva driver would be a better overall sub than a 1.2 cf box with the DVC? This is my first DIY speaker and I am going to have to go on what you guys tell me, but I want to do this right the first time around. This sub will be used both for HT and music (maybe 70% HT, 30% music). I am looking for a sub that's not at all boomy. I want tight "clean" bass and the best "overall" sub with that in mind. What do you guys think? Shiva or DVC? I don't mind a larger enclosure if I were to go with the Shiva (it could still be only 18"x18"x18" which isn't too large). Any opinions would be greatly appreciated.

 

[Wayne A. Pflughaupt]

Brian,
I can’t comment on the Dayton, but I have two Shivas in 2.5 cubic ft. boxes. According to everything I have heard, the Shiva works best in at least a 3.0 cubic ft. box (i.e., best extension).
However, even with the slightly undersized box I have been very happy with mine, especially after EQing out a room-induced response peak at 40Hz. I use mine mostly for HT, but personally I wouldn’t have a sub that didn’t do a great job with music. The Shiva delivers.
Anyway you cut it, you will have to get an EQ if you want “tight, clean” bass. Otherwise it will be boomy.
Since you’re building from scratch I’d do the 18”x18”x18” box (if you go with the Shiva), if you can afford the extra space. It will get better extension for HT use. You can always reduce the internal volume by putting in Styrofoam blocks if it’s not tight enough.
Regards,
Wayne A. Pflughaupt
------------------
My Equipment List

 

[Jack Gilvey]

You know things have gone down the sh*tter when people start quoting me.
I don't have the numbers handy, but I seem pretty sure of myself in that quote, so I guess I'll stick to it (given equal Qtc, though, might be too close to call). Jon also has some favorable comments on the Shiva in this thread . There's also a good discussion of the relative merits of each driver here (going back to that one, I see some of the FR graphs have been replaced with screenshots from the flight deck of an aircraft carrier. Not as useful, of course, but very cool nonetheless.)
Given that your use will be 3/4 home theater, though, I think I'd go with a ported or PR design. Much more output in the regions that are crucial, and a good alignment will sound very "tight".
[Edited last by Jack Gilvey on November 11, 2001 at 10:32 AM]

 

[BrianMu]

Jack,
Do you really think building a ported or PR sub is a good idea for someone who's never built a speaker before? I'd really worry about getting all of the parameters correct to get a good sounding sub (especially since I really need a sub that's not boomy). Won't the size of the enclosure likely increase significantly with a ported sub? While I have room for a 2-3 cf enclosure, I think that's about the max for me.
Brian

 

[Jack Gilvey]

quote: Do you really think building a ported or PR sub is a good idea for someone who's never built a speaker before? [/quote]
There's no question that sealed is the easiest, and there's almost no way to get it "wrong". If you can construct it properly(!), though, going with one of the vented or PR designs from Adire for the Shiva would leave little to chance as far as the design aspect is concerned.
quote: Won't the size of the enclosure likely increase significantly with a ported sub? While I have room for a 2-3 cf enclosure, I think that's about the max for me.[/quote]
Yeah, in general it'd need to be bigger. A PR design lends itself to a smaller enclosure than a vented, and the "Adire alignment" from the Shiva PR applications paper is only 3 ft^3.
Going with a sealed first and seeing how you like it would make the most sense, maybe, and you'd certainly have learned a lot to tackle a more involved project.
[Edited last by Jack Gilvey on November 11, 2001 at 12:21 PM]

 

[BrianMu]

OK,
This is getting more complicated... To many options! I've spent a lot of time looking at the Shiva applications pages. I'm not sure if they helped or confused me even more. I guess part of my problem is that I don't know what I want in terms of a Qtc, etc. I know I don't want boomy. So as I understand it, that means I don't want a Qtc much over 0.7 no matter what design I go with, correct? I do want relatively low extension, so does that mean that I should have a Qtc higher than 0.6? Is 0.7 a good place to be for me? While this will be used slightly more for HT than music, my ears detect crappy subs during music passages more easily than with movies. Boomyness is more obvious to me with music than movies. I guess this is because I know more what music is "supposed" to sound like than I do with movies.
Anyway, here's another possibility for you guys to comment on: What about a 15" DVC or Tempest in a sealed enclosure. I realize these would require larger enclosures, but might this be a best of both worlds compromise? From what I can tell, either of these drivers would give at least a little lower extension than the 12" drivers in equally "optimized" designs. Might going to a 15" driver give the sealed enclosure better HT performance while still allowing me to build a sealed enclosure and not making me worry about boomyness as I would with a ported enclosure?
Brian

 

[Jack Gilvey]

Qtc refers to sealed subs, and .7 is usually a good value for ht/music subs as it allows the lowest F3 for a driver while still having good transient response.
I imagine you've been exposed to lots of bad subs if you're that worried about a ported sub being boomy. They're not unless designed/made that way.
A sealed Tempest would be an excellent option. As with a sealed Shiva, 20Hz extension will ultimately depend on the amount of room gain you get.

 

[BrianMu]

I've been looking through the design information on Adire's website and the enclosure for a sealed Tempest is definitely borderline large for my living room. If the performance increase were worthwhile, I could probably pull it off through. Could a sealed enclosure for a 15" DVC be smaller than the Tempest? If so, how would it compare performance-wise? Is there any site on the internet that would have quantitative comparisons between the 4 drivers that I'm looking at (2 DVCs and the 2 Adire drivers) each in their own Qtc=0.707 sealed enclosures? I have played around with them in the spreadsheets provided on diysubwoofers.org and in Unibox but don't really know enough about what I am looking at to decide how they would be ranked. I think I'm going to go with sealed at least for this first time around. The only thing I need to decide on is the driver and performance and enclosure size are the two means I can use to discriminate between the 2 of these.
Sorry for all the questions, but I appreciate the help!
Brian

 

[Jack Gilvey]

Is there any site on the internet that would have quantitative comparisons between the 4 drivers that I'm looking at (2 DVCs and the 2 Adire drivers) each in their own Qtc=0.707 sealed enclosures?

None that I know of, I would have posted it long ago. The LspCAD demo fron Adire will give you a pretty good idea of what you can expect in-room.
As for "ranking" them, I'd put the 15" drivers ahead of the 12" if you can spare the room. If I were you, I'd go with a Tempest and one of the exact sealed designs from the Adire site. That way, there's no design worries.

 

[BrianMu]

Jack,
Thanks so much for your help. I've printed the sealed applications page for the Tempest driver and will give it a closer review. I think if I decide that it will not be a problem space-wise, I will go that route. If not, I will go right on down the line (15" DVC, Shiva, 12" DVC) until I find the largest sub design that I can fit in our living room.
Thanks again,
Brian

 

[BrianMu]

OK,
I thought I was done with all of the preliminary questions, but I have one more. I was looking at the Adire alignments and noticed that the drawings that they provide don't show a plate amp and in fact, the brace design would have to be fundamentally altered in order to mount a plate amp to a side. If I alter the brace design to fit a plate amp in, should that have a noticeable affect on the sound? Also, the addition of the plate amp and the redesign of the bracing would slightly alter the volume. Should that be compensated for as well? I was thinking that the Adire design would allow somone to make a sub enclosure that the driver manufacturer had specifically designed and tested. Apparently that only applies if an external amp is to be used.
Also, Adire shows the drivers mounted in a downfiring position in the drawings. Are there any disadvantages/advantages to downfiring vs. frontfiring (assuming the driver is meant for both applications as the Adire drivers are)?
Brian

 

[SalMaglie]

From a reply I got in another forum, you might not have to modify the bracing to mount a plate amp. Seems as though the way the components are lined up on the interior side of the plate amp, it splits the middle of a brace that is installed on the center of a side panel. I have no way of verifying this though since I'm just starting to build my first one, a 54 liter sealed Shiva with the Parts Express 250w plate amp and none of the parts have showed up on my doorstep yet. Perhaps somebody can verify this.

 

[Jack Gilvey]

I would contact Dan at Adire about the need to modify any bracing for a plate amp. Any change in Vb should be quite minimal, and have no real effect on a sealed sub.
Downfiring/upfiring will perform the same for all intents and purposes.

 

[BrianMu]

Thanks for all the help! I got an email reply last night from Dan at Adire and he told me that notching out the bracing for the amp will be no problem at all. He was quite helpful. So this morning I ordered my Tempest from Acoustic Visions ($140 shipped). Saturday I'll go get the amp from PE along with whatever I'll need as far as wiring and grill material. I'm going with the Q=0.707 122l sealed alignment as suggested by Adire. I can't wait to get started building!
Thanks again!
Brian

 

[Dan_D]

hey guys,
i notched out the bracing w/ my tempest project. take a look
http://thend.org/~dannydigital/tempesthowto.html
(sorry i keep posting this link everywhere, but it keeps seeming helpful )

 

[BrianMu]

Dan,

Looks nice! I ended up notching the bracing to fit around the amp as well. As it turns out, I didn't have to notch very much since I doubled up on the back side and the front (I went with a front-firing version) which moved the amp out of the box somewhat. I'm not nearly as far along as you (I built the MDF portion of the enclosure yesterday) but am planning on covering the box with 1/4" oak plywood as well. I'm glad to hear (and see) that you like the way your box turned out with this method. Let us know how that big boy sounds when you get it hooked up!

Brian

 

[Dan_D]

actually is been done and in use for about 4 months now. Im very pleased with how it turned out. i can play some nice drum n bass or jazz for my more audiphile'ish friends or some bass mekanics SPL cds for my less educated bass head friends. hehe either way i get lots of positive feedback. And of course in the whole HT environment its just insane
Im also planning a smaller Adire Shiva based sub for my dad for christmas. Ive had good results from Adire so far so im stickin with em.

 

[BrianMu]

I'm glad to hear you like your sub, Dan. I'm hoping to have my enclosure finished and ready to go for when I get the Tempest driver Monday (UPS is going to take their time in delivering it, apparently). Hopefully at that point my wife will like the way it sounds enough to forgive me for spending $350 on a sub instead of redoing the kitchen floor!

 

[BrianMu]

Hi All,
Sorry to drag this thread up again, but I just wanted to say thanks to all that helped answer all of my questions. I got my sub all hooked up last night (it's now completely finished except for the grill). All I can saw is WOW! I'm glad I went the DIY route. I haven't calibrated it yet, but it sounded great while listening to some CDs and when I put in Star Wars TPM (I'd heard that it was great for low bass but had never heard it with my old sub), I was blown away. The THX trailer at the beginning scared the crap out of me (and my dog:frowning: ). For the first time, I really felt the bass. While playing the pod race chapters, I learned that the springs in my living room windows (they're aluminum windows) have a tendancy to rattle at many low frequencies (which became very annoying). I don't know if I can find a way to fix that or not. Other than that, it sounded wonderful. Very tight, clean, low bass. It's great for music and movies. I had no idea what I was missing.
After I get the grill made, I'll take some pictures and can post them here if anyone is interested.
Thanks again,
Brian

 

[Jack Gilvey]

Sounds great, Brian, glad you like it. I'd certainly like to see some pics when you're done.