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Old 21st February 2016, 04:08 PM   #1
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Default The quest for 20hz open baffle bass

My listening room is approximately 15X30 and the ceilings are vaulted. I hear it is difficult to get open baffle bass below 30hz which is about what I think I am getting with my Kazba with 10" drivers. The sound is great though so I am exploring the option of trying to build something open baffle instead of employing a sealed sub for those last few hz. So can something "reasonable" be built open baffle that has great 20-200 bass or am I looking at building something comparable to a Visaton Grande Orgue. And is it worth it; I've also heard that in small rooms a sealed sub won't excite room modes much from 20-50. Let the fighting, ehr, I mean constructive comments begin. (This wouldn't be half the fun if we all agreed on everything though would it? )
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Old 21st February 2016, 05:59 PM   #2
xrk971 is offline xrk971  United States
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It's a noble and worthy endeavor to seek dipole bass as low as possible. But without a sealed back it may be very hard to generate rumble that deep. How far away is your listening position from the sub?

To get 20Hz with a larger Kazba it may be possible. CLS's Kazba used dual 18's but he had rather low Qts pro audio woofers. A pair of Eminence Alpha 15's in a Kazba may have a better shot at 20Hz, say 5 ft away.

Maybe CLS can chime in what his low extension was. IMO, if you are hitting 30Hz you are doing very well.

Note that bandpass injection into a short horn with an open back can achieve 30Hz. With some wings on the back perhaps 20Hz can be had? Bushmeister was able to get 30H easily with very low HD. I would imagine some EQ would allow 20Hz with a little more distortion.
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Old 21st February 2016, 06:29 PM   #3
GM is offline GM  United States
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Carver's dipole 'sub' alignment gives a good account of the basics to low dipole bass design and the 'wall of science' you're going to be 'beating your head' against doing it in a relatively large acoustic space with readily available 'sub' drivers; not impossible, just about as practical to do as its corollary, a same gain BW reactance annulled BLH: Carver Amazing Loudspeaker (Platinum Edition) | Stereophile.com

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Old 21st February 2016, 06:35 PM   #4
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5' to listening position is doable.
Good to hear Kazba might work for this. I like the look too.
And I've had my eye on this PRV 15" Resonant frequency of 31, .62qts and 5.5 xmax $68.00!
PRV Audio 15W700 15" High Power PA Woofer 8 Ohm
Do you think it would better the Alpha in a Kazba? Alpha's at 41hz, 1.26qts and 3.8xmax
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Old 21st February 2016, 07:06 PM   #5
Bare is offline Bare  Canada
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Isn't Normal human hearing somewhere near -100 db at 30 hz ?
Suggesting one Plan accordingly
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Old 21st February 2016, 07:12 PM   #6
Decker is offline Decker  United States
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I am using the MCM 21" woofer in a U-frame stuffed with denim insulation. 6 db boost at about 30 hz, and a high pass filter set for 20 hz. No 20 hz response, but I get very good bass down to 30 hz. Best bass I have ever had in my room. Before this I was using a pretty good subwoofer, but took it out because I was getting plenty of good bass from the OB woofers.
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Old 21st February 2016, 07:12 PM   #7
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Hi, no way a woofer classified as P.A. speaker would serve as to subwoofer duty.
Waaaay more expensive is the Acoustic Elegance TD15M series, being the H model the one designated for subwoofer. See the gum suspension ? It allows more X-max than pleated fabric ones
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Old 22nd February 2016, 09:02 AM   #8
Toaster is offline Toaster  United Kingdom
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The GR Research servo OB 12" drivers and matching plate amps are the best thing I've heard, and are what I've been using at home for a few years now. The plate amps can drive either two or three of the drivers each. I use two drivers a side in a smaller room than yours- but they will go far louder than I can stand.
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Old 22nd February 2016, 09:21 AM   #9
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Just to maybe add a bit of common sense into the thread. The reason why dipoles are effective at improving the bass response within a room is due to the way they energise the rooms modal region. In small acoustic spaces the modal region has a defined end point. In my room this is 40Hz. In smaller rooms this would be higher in frequency and larger ones lower.

The point here is that once the rooms modal region has ended there is absolutely no point in bothering with a dipole. There are no room modes or issues for the dipole to try and fix.

Dipoles are an often acceptable answer to improving bass reproduction in small acoustic spaces but they come with the huge penalty of terrible efficiency. Going lower only makes this worse. Put simply there is no point in going dipole below the rooms modal region. You should go sealed or better yet with a well designed ported box.
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Old 22nd February 2016, 09:22 AM   #10
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Those are under my trigger too; when I'll happen to have 500$ disposable or 1000$ ( I like dual channel, dunno...! ) probably yes ( probably not )
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The GR Research servo OB 12" drivers and matching plate amps
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