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Parts Express just sent me the new Ultimax 18" sub for testing. It is a monster that comes in a kit with enclosure and 1200 watt class D amp with DSP. I have not had a chance to do complete testing but the closed miked distortion at 100 dB is the lowest of any low frequency driver I have ever tested. Not surprising because it is 18" and has 22mm Xmax. One of the interesting things I have seen is that if you put in the full range signaleither analog or digital the pass through to the main speakers is not just a straight connection or a simple one capacitor fixed high pass. Rather you can select the crossover point and slope of the high pass with the DSP. I should have the testing and the comparison to two of my 15" sealed box subs done this month. In theory one of these should be the equal of two of my subs in a box considerably smaller than two of my current subs. The photos do not do justice to seeing it in person.

Here is a link to their info:

http://www.parts-express.com/dayton-aud ... --300-7200

Tom

Looking forward to read more about your finding. One of the things is how high in frequency can you push it to, but more important, how well one can integrate box wooded with dipole "main" speakers?

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SamB

I don't generally go above around 90 - 100 Hz with a sub. Afterall it is designed to be a subwoofer not a woofer. The interesting thing about integration is how well a sealed box sub can integrate with dipole speakers. David Berning was quite surprised at how well two small sealed box subs I did for one of my articles worked with the home made electrostats he had. We used them last year at CAF. People generally react to what they consider slow as the effects of ports, passive radiators, transmission lines and other bass reinforcement techniques that mess up transient response.

As far as radiation pattern, dipole patterns are important to maintain in the range of frequencies where the wavelengths are small in relation to the room. Once the frequencies get low enough that the wavelengths are in the range of room dimensions, it really no longer matters. My sealed bass subs have integrated quite well in my system which is dipole from 100 Hz up.

Tom

Where would you place a sealed subwoofer in a room? (I'm assuming Qtc of no more than 0.7?...)

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SamB

Sam:

I'm not too woried about the QB of a sealed box sub because I use DSP to correct any anomalies in response that occur with a QB that is not optimum. It also allows me to compensate for room gain or lack thereof at low frequencies. There are a lot of conflicting opinions about placement in a room of any sub or combination of subs regardless of enclosure types. The predominant thinking is in the corners at the floor or the middle of the walls at the wall/floor interface. I have always used the corners. I have to say that my current listening room is one of the worst I have ever had. That coming from a great room in my last home. It is frustrating. Using electrical eq is OK at long wavelengths but not effective at shorter wavelengths. Here is a photo showing the placement of one pair of my subs in the room. The subs are in the other corner at the right side but the two dipole driver arrays are not the same distance from the wall at the right side because the room has a window on the right side that caused some problems, That necessitated some interesting phase and timing corrections. Everything is always a compromise.

Tom

I was thinking to start with reasonable acoustic/mechanic plan, and than just tweak it a little.
Any recommendation for a 12" or 15" for a sealed box? I'm going to build 2 of of them.

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SamB

Have you read about these. They sound interesting though I have never heard them.

http://www.transcendentsound.com/Subwoofer.html

ray

I saw it before.....however, since I'm plan to set them at the corners, I can make a box that will fit nicely to the corner....
Also for bass you want to use tho bigger wooded you can fit....

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SamB

Tom, Where can I read your review?

Tom,

I'm looking forward to your review. Im going to be getting a new sub next year and I'm very interested to hear your thoughts.

Regarding sub placement I was recently told that for a single subwoofer, the best way to determine placement is to place the sub at your listening position and walk around the listening room. Whatever spot sounds best is where you should place the sub. I've not tried this year but the guy that recommended it is pretty well versed.