CECAA850 Posted January 26, 2015 Share Posted January 26, 2015 A subs tuned to 20 Hz can have a flat down to 10-15 Hz with no problem in smaller rooms with good room gain which is 12 db per octave for sealed subs. OK, confusion alert. You talk about a sub tuned to 20 Hz, OK fine. They drop off like a rock below tuning frequency BUT you'll get some extension with the rooms help. You then reference sealed subs in the same sentence which roll off much more gradually and are better down low. I can't follow the sentences structured logic. BTW, horns drop off fast as well below the tune of the box. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 26, 2015 Share Posted January 26, 2015 (edited) A subs tuned to 20 Hz can have a flat down to 10-15 Hz with no problem in smaller rooms with good room gain which is 12 db per octave for sealed subs. I never imagined that. I figured at 10 hz, a ported sub tuned to 20 would have the port's output 180 degrees out of phase with the driver. What did you think about 40Hz? Edited January 26, 2015 by CECAA850 Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted January 26, 2015 Share Posted January 26, 2015 (edited) Sealed subs can extend low. You are correct that ported subs drop fast due to the hpf to protect the driver. Vented subs also benefit from room gain but they roll off at a 24 db slop compared to 12 db slop for sealed. I can see where there is some confusion since I use sealed and ported. The main point was that someone ask for which sub to go with and it depends on room size, the number of subs the person can tolerate in the room, ect. Also, extension without brute force is meaningless for the most part. A few bass shakers and no need to worry about some of these things, lol. Edited January 26, 2015 by derrickdj1 Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 26, 2015 Share Posted January 26, 2015 You are correct that ported subs drop fast due to the hpf to protect the driver. They drop off fast as a function of the design. You can see it in Winisd. You are correct though. HPF's are needed to protect the driver below the tuning frequency of the box. Quote Link to comment Share on other sites More sharing options...
John Warren Posted January 27, 2015 Share Posted January 27, 2015 (edited) I had some fun with the McCauley 6174. The -3dB was 16Hz assuming an "optimistic" Q of ~20. http://www.northreadingeng.com/McCauley_6174/McCauley_6174.html The McCauley unit is around $1400. The output from this will easily rattle a large house. The enclosure is about 300lbs. Mounting the driver to the baffle requires serious fasteners, eight 3/8"-18 machine cap screws into tee-nuts. When I purchased the speaker, I measured Qes using a couple of methods. It was higher than advertised specification of 0.38 (for this driver, I'd be ok with numbers between 0.34-0.42). I was measuring numbers closer to 0.60 which is UNACCEPTABLE given the cost. I shipped the magnet to McCauley, they re-charged it and sent it back. Measurements were better but still higher than advertised (fwiw, on a 18" JBL unit that I also had, the Qes was LOWER than advertised). McCauley sent me the process router they use that instructs the technician as to how to measure Qes which was, essentially, identical to the method I was using. So the point is, if you intend to go to the trouble of building something with a large driver and you just use the OEM specs in a canned program to give you box dimension don't be surprised that the result is a "boom-box" with "flabby bass". Also, building large cabinets is a challenge all by itself. They have to be rigid otherwise more "flab". Ideally, the enclosure would be fabricated from Phenolic plate like Wilson Audio uses. Edited January 27, 2015 by John Warren Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 27, 2015 Share Posted January 27, 2015 Also, building large cabinets is a challenge all by itself. They have to be rigid otherwise more "flab". I couldn't agree more. There's a few inherent issues when building a large box. If you use MDF, you'll have an issue with weight. If you use hardwood ply, you'll have an issue with warping. Both require extensive bracing which is more work. I'm working on a 29 cu ft box now with a couple panels that are nearly 6 ft. This particular box is made of Birch ply. It would have been a lot easier fitment wise using MDF. When I have to move it, I'm glad it's Birch. Quote Link to comment Share on other sites More sharing options...
mxr dad Posted January 30, 2015 Share Posted January 30, 2015 I dont have any knowledge to bring to this discussion other than to say......... Thats my 29 cu ft he's building for me! Good to see ya again Carl. The build looks great. When are we gonna start a thread with this bad boy? Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 30, 2015 Share Posted January 30, 2015 When are we gonna start a thread with this bad boy? After the last coat of paint I don't want anyone to know how slow I am. If you post them start to finish all at once it looks like you built it overnight 1 Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted January 30, 2015 Share Posted January 30, 2015 (edited) That sub must be the size of an SUV, lol. I can't wait to see it! This forum is really starting to beef up the bass. It is all about that bass. Edited January 31, 2015 by derrickdj1 Quote Link to comment Share on other sites More sharing options...
Paducah Home Theater Posted January 30, 2015 Share Posted January 30, 2015 I just want to see how you're going to ship the thing. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 30, 2015 Share Posted January 30, 2015 I just want to see how you're going to ship the thing. It's only going a little over an hour from here. He'll bring a pick up truck (and a big friend I hope). Quote Link to comment Share on other sites More sharing options...
mxr dad Posted January 30, 2015 Share Posted January 30, 2015 Let me introduce you to my big friend; Carl, meet Carl!!! So your saying it wont fit behind my seat in my truck? It is about same size as fridge. Cant wait to shake the dust off the rafters! And the neighbors rafters! Yep, we got shipping and handling under control. My son lives right down the road too. Maybe I can get enough help where Carl and I can just supervise with 1 hand, the other hand holding a cold one! Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 30, 2015 Share Posted January 30, 2015 Maybe I can get enough help where Carl and I can just supervise with 1 hand, the other hand holding a cold one! \ NOW you're talking! Quote Link to comment Share on other sites More sharing options...
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