Home Theater Forum and Systems banner

1 - 20 of 20 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
Hello.
New member, been lurking and learning for quite a while, and I believe that I've finally figured out what I want. My plans are to add a homebuilt sub to the home theater. Was going to go bfm THT, but I simply do not have the home time to accomplish a project like this. My ol' lady would probably kick my butt, as well. So, this is what I've come up with for my 15' X 10' X 9' living room:

Driver: Dayton 12" ultimax
Cabinet: Diysoundgroup 4ft ^3 ported flatpack.
Cab asc: P.E.

Plan on running my Peavey cinemacoustic ca-a800 in 2 ohm stereo. 1 channel per vc. This thing is pretty much a Peavey 1.3K built for theater installation. Damping is >300, power is 1000wpc/2ohm. One reason I chose this speaker package, is because total cost is <$400. Another one would not be a problem to add, if a single doesn't cut it. Only worries I have are obliterating xmax and xmech. I obviously wouldn't have it cranked up FULL time... well occasionally... :R But pound for pound and dollar for dollar, I haven't come up with anything else even close with an f3 of 19hz. Would love a 15" or 18", but finding a flatpack cab that can play ultra low is the issue. I simply don't have the time to build a custom enclosure, though I can talk my dad into gluing this one up for me! What do y'all think? Is this gonna shake the theater? :hsd: I'm guessing so. Even my (supposed) 300 watt Bose acoustimass bass module could blast fairly loud in this room.
 

·
Registered
Joined
·
291 Posts
Can you post a link to the flat pack? I'd like to see what it has for porting.I can only find a 4 cu.ft. sealed. I can only find specs on the CA-A800B and it isn't rated for a 2 ohm load. Are you sure your model is?
Hey Mike.. It's at the bottom under SW FP. At 300w with a hp at 20hz, velocity comes in at 22m/s. Ramp it up to 500w it comes in at 28m/s.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #7 (Edited)
Sorry guys, couldn't post the respective links as I do not have 5 posts yet. The Peavey ca-a800"b" model is a slightly later edition. Didn't care for it as much as it was lacking 1/4" phono inputs. The speaker jack outs list: 8ohm 400wp/c 56 or 57 volts(cant remember), 4ohm 650wp/c 51v, 2ohm 1000wp/c 44.7v They say it isn't recommended to bridge into a load lower than 8ohms... but again, this is essentially a 1.3k p.a. amp (almost identical) and those are listed into 4ohm mono...2000watts. But hey, if I can do the same in stereo 2ohm, no big deal. I give $106 + 50 to ship on the amp (which was rack-mounted brand new and in a cinema for the last 18 years. Looks brand new. Total investment for ulf package, will be around $540, and again, can always add another and run 4 ohm stereo dual subs.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #9
Hey Mike.. It's at the bottom under SW FP. At 300w with a hp at 20hz, velocity comes in at 22m/s. Ramp it up to 500w it comes in at 28m/s.
Please, brother, enlighten me. Not quite sure what these statistics mean. Are the (2) 3" X 24" ports going to be large enough to avoid turbulence? Again, probably won't be running this box at full blast but for fractions of a second.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #10 (Edited)
Modeling shows you'll be good for 300 watts per coil into 2 ohms or 600 watts with the coils wired in series for a 4 ohm load. You will need a hi-pass filter at 20 hz so the sub doesn't bottom out.
10-4 on the high pass. Is there any particular slope or configuration that is preferable, and will still allow the sub to dip below 20hz, just roll it off a bit? I will do some checking into this. Thanks for the heads up. :T

Found these: Harrison Labs FMOD 20Hz Hi Pass Subsonic Filter Rumble Reducer. Something like these? No slope listed, will dig deeper!

Upon digging deeper, just realized the Behringer cx2310 that I had in my Carvin P.A. rack would have been perfect. Has anyone found these Harrison Labs FMOD's to be effective? Seems like a low cost alternative to an actual active x-over.
 

·
Registered
Joined
·
291 Posts
Please, brother, enlighten me. Not quite sure what these statistics mean. Are the (2) 3" X 24" ports going to be large enough to avoid turbulence? Again, probably won't be running this box at full blast but for fractions of a second.
You will see the pics of a project (I followed it) in the 3” vent review over at PE. The project is exactly what you’re contemplating (I forget the amp though) and he was very happy with the results. The sub turned out great! I have no doubt that you most likely would be quite impressed!
 

·
Registered
Joined
·
9 Posts
Discussion Starter #14
Thanks, Steve and Mike. Appreciate the information. Will check out the 3" port link, and snap some pics when I get ready to get this up and running. The FMODS show 12db/octave slope, which should buy a bit of protection for the sub 20hz frequencies. Although they don't list an impedance, they're supposed to be usable with any rca input or line out, (max 10volts). I only wish I had a pre that hot!
 

·
Registered
Joined
·
100 Posts
Mike, I'd be willing to bet that they are impedance sensitive. Just how sensitive, I don't know. But for that price, I don't see any way around it.

No, I don't believe they can be used on a "line out". Please correct me if I'm wrong about that, since I could use one on my sub if that was possible.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #17
Mike, I'd be willing to bet that they are impedance sensitive. Just how sensitive, I don't know. But for that price, I don't see any way around it.

No, I don't believe they can be used on a "line out". Please correct me if I'm wrong about that, since I could use one on my sub if that was possible.
I'm not sure why you couldn't use these on any sub with a line voltage under 10volts. (Only pre I'm aware of that is THAT hot is an older Kenwood Excellon car stereo pre @ 9v rms). These FMODS aren't speaker level filter caps, they are line level, (and unless a phonograph connection), I wouldn't think that impedance would be relevant. But I do have a lot to learn. Cheap gamble though, at 15bux each... could work out pretty well, and have a one year warranty.

http://www.ebay.com/itm/390791359452?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
http://www.ebay.com/itm/Harrison-La...bles_Snakes_Interconnects&hash=item564bc7c875

If I'm understanding this wrong, please correct me.
 

·
Registered
Joined
·
100 Posts
Ok, my idea of "line out" isn't correct.

Yeah, they are worth a try due to the low cost. They sell a bunch of them, and people seem to be happy with their purchase. However I would expect that due to the low cost, the attenuation and cut-off frequency precision is ummm, unstellar! Typical input impedances are in the 50kΩ range. But some are 10kΩ, and some tube amps are 1MΩ. I don't see an inexpensive inline filter coping with that range of impedances with any accuracy.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #19
Paulcet, Will give 'em a try. If I don't get satisfactory results, I may end up purchasing another Behringer electronic x-over, as they're fairly easy to find and not a huge investment. If one sub cab doesn't have the "thrill" I'm seeking, may possibly just build an identical second, and bring the power down to a much more manageable 650watt per sub. May not even need a highpass filter to keep xmax in check at that level.
 

·
Registered
Joined
·
11 Posts
We, not to beat a dead horse here, or a very old thread, but I had to laugh a little at this claim in the FMOD sales description.
"It is better than a much more expensive electronic crossover that requires power to operate"
.
Even a Behringer electronic XO is a much better choice, especially if you choose to Bi-amp your mids/tops.
I have used a Behringer 2496 XO of which I had 2 just simply die on me, it seems to be a PSU problem.
I had another Behringer XO (CX 2310) which worked beautifully.
I now have an ART CX 311 which I am very happy with, anyway the issue that I am getting at, having a knob to set the XO points and using my ears to choose them, I think gives me so many more choices than just using theory to choose the XO point and then being stuck with that setting.
Well, I guess it is something to think about.
Dave
 
1 - 20 of 20 Posts
Top