Some basline questions re: DIY sub

[Bengoshi2000]

I have gotten spousal approval to build a sub (to replace the melamine coated dbx-15 I have now). The room is approx. 13' x 26' x 8' w/popcorn ceiling, with only two standard door-size entryways (on one of the 26' walls) and a full masonry fireplace (on the opposite 26' wall). Intended use for the sub is probably 50/50 music/HT. Size is a factor here... SWMBO will not tolerate anything over 20"w x 20"d x 24"h. Budget max. is $600 (for the entire project, including finish, which will be furniture grade... hopefully).

Other environmental considerations are my 2 year old, who will poke at any front firing sub and will likely stuff shoes into any front firing ports. All of my kids are small and go to bed early... so bone jarring, seismic-concussion inducing bass is problematic. My L/R mains are Polk Monitors (5-1/4" 2-ways about 15 years old) and the matching CS 100 center. Surrounds are Atlantic Technologies 3.5" dipoles.

I've downloaded UniBox and WinISD Pro. I've looked at sealed and vented alignments for several 12" subs (Shiva-X, CSS SD12, GR Research SW-12B, Peerless XXLS 12) to the point I have a headache. I've even drawn up several models in Sketchup. I have an appointment next Thursday with my therapist for my evolving OCB disorder (spawned by this sub project).

I've done so much modeling at this point that I've lost perspective. And now, I'm wondering if I shouldn't go to a 15" sub (assuming that a 15" sub will be more efficient with low frequencies at low volume than a comparable 12").

Ladies and Gentlemen, I need focus.

[Mike P.]

Budget max. is $600 for the entire project......

That would mean the amp is included in the budget?

[Bengoshi2000]

Mike P. wrote:

That would mean the amp is included in the budget?

Yes.

My inclination at this point is to go with the Shiva X or the CSS SD12 in a sealed enclosure for simplicity.

[Mike P.]

Actually you have "ported" option. CSS will be introducing a new12" sub within a week or two. It will be replacing the SD12 and it's called the TRIO12. There will be a introductory special consisting of the sub and 2 passive radiators for $199. The box design is the same as the SD12 subwoofer kit, a 3.2 cu. ft. box which translates into a 20" cube. The cabinet plans are here:

http://www.creativesound.ca/pdf/Quar...woofer_Kit.pdf

CSS also sells the Bash 500 amp which is a perfect match for the sub and enclosure size. The sub, PR's, amp, lumber and finishing would be well within your budget, and would have superior low end performance for HT compared to a sealed design.

[tcarcio]

The Shiva is on sale now and if you pair it up with either the Behringer EP-2500 or the O-Audio or Bash 500w plate amp you will be able to stay in your budget.

[Bengoshi2000]

Mike P. wrote:

CSS will be introducing a new12" sub within a week or two. It will be replacing the SD12 and it's called the TRIO12. There will be a introductory special consisting of the sub and 2 passive radiators for $199.

Wow! I'm assuming that kit will be $199 US (without an amp)? That price may have just changed my mind.

The only problem I have with a front firing woofer (and side firing PR's) is my above-mentioned two-year-old. I love her to death, but she's gonna make a b-line for that sub and start poking/prodding at anything that looks interesting.

Hmmmm... I wonder what creative solutions I could come up with for protective grills to cover the driver and PR's? Maybe I could mount the TRIO12 as down firing... then I'd only have to be creative with protecting the PR's?

Any ideas?

[BillCinLR]

Ben,

I know that this will be met with a LOT of negative comment, but I have just rebuilt my old DBX-15 with a CSS SDX-15 and an o Audio 500 W amp, some panel damping foam from PE, and 3 lbs of poly-fill from Walmart. It isn't the ULTIMATE, but it does sound good and compliments the EPIK Dragon 18" sealed sub that replaced it.

After I replaced the DBX with the Dragon, I just couldn't stand to throw it away (You can't GIVE away a 20 year old passive sub!), so I decided to "Tweak" it a bit ... I don't have REW or an equalizer like most on this site seem to have, but comparing the two side by side listening to familiar material I found the tweaked DBX to be very tight, loud, and musical ... it just won't dig as deep as the Dragon. When run together, they sound great!

Again, this is NOT an optimum, precisely engineered speaker, but it would solve your problem with "child proofing" while providing amazing sound.

For the techies, this box is 82.8 L with speaker & amp, 5/8" MDF sides/top, 3/4" MDF baffle. WinISD shows the SDX-15 3db down at 35hz, 10.7 db down at 20hz.

Have fun,

Bill C

[Mike P.]

Down fire the sub and making grills for the PR's is easy enough if you have a router. Have a look at the grills I made for my 10" sub kit.

http://www.hometheatershack.com/foru...0-sub-kit.html

[Bengoshi2000]

Well, I'm fairly well decided on the CSS SD12 (or the TRIO12 when it arrives). I'm leaning away from the PR option at this point (due to WAF, and TDT issues).

What I am leaning towards is the SD12 in a 76.3l box tuned to 23hz (single 4" port 20.5" long). This is fairly close to the suggested size/tuning that WinISD Pro initially calculates. I modeled it with an 18hz 3rd order hpf with a Q of 1 (as used by the PE 500w plate amp... NOT the Bash 500). This would give me an F3 of 24.5hz and F10 of 19hz.

I'm leaning towards this amp because the peq gives me some flexibility for taming room nodes.

Honestly, I'd prefer the O Audio 500w Bash, but from what I've read it would need to be set up VERY carefully for a ported enclosure.

[Bengoshi2000]

This is the amp: PE 500 watt plate amp

SPL Curve:

[BillCinLR]

Ben,

Something that everybody seems ignore on the o Audio 500W amps is the built-in parametric equalizer that can be used to reduce unwanted boost in the lower frequencies (at least down to 20Hz). I looked at the amp from PE and decided that a selector switch was much more convenient than un-soldering/re-soldering on the printed circuit board of the amp. I believe that the PE amp comes with a built-in boost at 35Hz that requires circuit board modification to change. You can always employ an outboard equalizer to tame room response.

OOPS! Sorry, I was thinking of the PE 500w BASH amp ... please ignore that last comment on the built-in boost.

Good Luck,

Bill C