what to build?

[greasemonkey]

Hi all! So here is my problem. I am putting together a small p.a. system for a group of belly dancers. Lots of bass heavy music, including some techno/trance stuff. Small venues, less than 100 people usually. I have a Peavey xr600c mixer amp and a set of mtx aal-15 speakers that I have donated to the cause, as it was my garage stereo. They sound decent together and their power rating complement each other well (read that as-me and my buddies cant blow them up with this amp, even after the beer comes out). I will be making new cabinets for them in the same size and configuration out of 3/4 plywood so they can take road use. We need more bottom end though. I have a Peavey cs-800 amp that we can use as a sub amp, and a pair of rockford fosgate RFP-1212 subs sitting on a shelf from a project long ago. What kind of enclosure should I build for them? One of the girls' grand father is a professional cabinet maker, and I'm pretty good myself, so complexity isn't really an issue. I know these driver aren't ideal, but we own them. And cost is an issue. I'm basically working for Guiness and getting to go to the after parties I need smooth clean deep techno/trance bass and a really solid chest hit when the kick drums kick. Scaled down cubo 15? TL? plain ol ported? Any suggestions are MUCH appreciated, and the driver specs are in the link below. Thanks guys! I know its a miss match of equipment, but its what we got.

http://www.rockfordfosgate.com/libra...fp-1212-ts.pdf

[djk]

Driver Properties
Name: RFP1212
Type: Standard one-way driver
Company: Rockford Fosgate Corp.
Comment: Punch HX2 series
No. of Drivers = 2
Mounting = Standard
Wiring = Parallel
Dual voice coils = series
Fs = 25 Hz
Qms = 5.4
Vas = 103.9 liters
Cms = 0.251 mm/N
Mms = 147 g
Rms = 4.697 kg/s
Xmax = 11.2 mm
Xmech = 16.8 mm
P-Dia = 262.2 mm
Sd = 540 sq.cm
P-Vd = 0.605 liters
Re = 6.6 ohms
Z = 8 ohms
-----------------------------------------
Box Properties
Name:
Type: Bandpass Single-Tuned Box
Shape: Prism, Bandpass
with two chambers
Chamber 1 - lower-freq.
Vb = 2 cu.ft
Fb = 54.02 Hz
QL = 6.654
F3 = 32.19 Hz
Fill = minimal
Chamber 2 - upper-freq.
Vb = 2 cu.ft
Fb = 54 Hz
QL = 6.773
F3 = 91.83 Hz
Fill = minimal
No. of Vents = 1
Vent shape = round
Vent ends = one flush
Dv = 8 in
Lv = 16.16 in
*******************************
95dB/2.83V/1M, 32hz~92hz. Coils for each driver wired in series, both drivers wired in parallel.

[greasemonkey]

Thanks! What would the advantage of a band pass be over the vented enclosure be? I only ask because WinISD shows a slightly deeper low end response with the same SPL everywhere else. Would it have a better SQ? I like the idea of having the subs protected in the enclosure. Better to run two enclosures so I can spread them out, and pole mount the mtx's in the sub boxes, or just one enclosure with both subs. Thanks for the help

[Arty]

bandpass has the advantage of -usualy- better efficiency.

[revboden]

generally, bandpass has worse group delay (ie muddy sound) than a BR box and is much worse than a sealed box. I'd go with a simple slot ported box. ~5ft^3 port tuned to 20hz ebs3 alignment.

[Brian Steele]

Originally Posted by revboden

generally, bandpass has worse group delay (ie muddy sound) than a BR box and is much worse than a sealed box. I'd go with a simple slot ported box. ~5ft^3 port tuned to 20hz ebs3 alignment.

I don't agree wrt group dely of BP and BR boxes. The real answer to the group delay issue is.. it depends on the alignment.

As this is for a "pro" audio use where SPL is more important, I don't think an EBS alignment is a good fit for the requirement. DJK's suggestion adds just about 2dB of gain overall, which is a plus.

This driver might also be a good match for a "bandpass with expanding vent" alignment, which can be modelled in HornResp. You really don't need 30 Hz response for the intended use, so if that can be pushed up to 40 Hz (with the corresponding increase in gain), all the better.

BTW, if you're going to go to the trouble of doing this, for heavens' sake confirm the t/s parameters before committing to the design!

[revboden]

after additional mucking about, 4ft^3 port tuned to 25hz. 111.5db at 30hz with 268w f3-25hz.

as brian said, definitely double check the T/S parameters, there is something fishy about the published Q parameters.

P.s. I'm modeling single driver boxes.

[revboden]

I've heard Trance ( YouTube - Rob Sparx - Going Back - Z Audio.wmv ) that goes to lowC so having the extra range may be useful.

[Brian Steele]

Originally Posted by Brian Steele

This driver might also be a good match for a "bandpass with expanding vent" alignment, which can be modelled in HornResp. You really don't need 30 Hz response for the intended use, so if that can be pushed up to 40 Hz (with the corresponding increase in gain), all the better.

I was able to come up with a HornResp alignment for one of these drivers that does from 40 Hz to 100 Hz that's ~94dB/1W/1M in the passband. It's a fairly big box though - about 59 litres (net) per driver. It's basically a bandpass design with a huge reverse-expanding vent. I've never built one of these things though, so I can't tell you if the results will match the HornResp predictions.

DJK's alignment is less sensitive, but uses a smaller box and results in an excursion minimum around 54 Hz - my design pushes that up to 60 Hz.

[bjorno]

FYI: 2xRPF-1212-DVC paralleled coils ,serial connected ~6.5cu.ft, ~30-115 Hz, build height external dimension = ~47.3" T-TQWT:

b