subwoofer question......what size sub ?

Whether an 8" or 21" driver IMO its all about control. The more control the more versatile with a wider range of rooms and speakers and therefor a better value over time.  

http://syzygyacoustics.com

I'm a big fan of Hsu.

You could do just about any driver size. Depends mostly on output and room size. 

The bigger issues are integration. Room acoustics, placement and EQ make or break a sub installation.

For this reason, smaller subs with higher -3dB cut offs may outperform bigger subs. They don't rouse the dragons in the lower octaves. 

Best,


Erik 

The trick about good integration of a sub has more to do with room integration than with the sub itself. Hence also, the proper size of the sub and driver are largely related to the size of the room. Pump too much deep bass into a small room and the result is pretty awful because of room modes. For that same reason I would always go for at least two smaller subs instead of one larger one, and always tamed by dsp room eq like the Antimode 8033. See here for a good first introduction: http://www.acousticfrontiers.com/20101029using-multiple-subwoofers-to-improve-bass-the-welti-devanti...
For music I would usually prefer a sealed sub. In a smallish room and on a limited budget perhaps two SVS SB1000s. In a larger room and on a bigger budget you may want to consider the Audiokinesis Swarm System: http://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/
Both combined with the Antimode, of course.

Willemj,

Regarding the Antimode 8033, how does this device interface, if at all, with the sub's plate amp controls such as delay, phase, crossover, and volume? So, do you first zero-in your controls for sound and then put the 8033 in line? Or, will you need to recalibrate?
Kenny

It sits between the amplifier (either at line level if you have that or with an attenuation cable at speaker level). It does not do low pass filtering or anything for you. You have to figure that out in the usual way. All it does is measure the room response of the subwoofer (an easy one time only automatic procedure with the provided microphone) and then applies an appropriate correction curve to the signal before it reaches the subwoofer. Since it removes bass peaks you may have to increase the sub’s level a bit, and that is all. See here for the manual: http://www.dspeaker.com/fileadmin/datasheets/dspeaker/antimode8033CinemaSIIen.pdf
I have found it very easy to use, and remarkably effective for relatively little money. See here for a review: http://www.theabsolutesound.com/articles/dspeaker-anti-mode-8033-dsp-subwoofer-equalizer-tas-204/
In my case, my main speakers are Quad 2805s, and they lacked a bit of deep bass. So I added a B&W PV1d, but found it hard to integrate the sub perfectly. So I remembered all those stories about fasts stats and slow subs, and feared I had made a mistake. Then I stumbled upon the Antimode by chance and decided to take a gamble, because the theory and the physics seemed right, and so did the room response measurements that they presented as examples. And indeed, the bass suddenly became much tighter, more tuneful, and ’faster’. What I learned is that fast and slow has nothing to do with the moving mass of the speaker but with the slowly lingering decay of the in room response that you can see in waterfall plots. Stats are fast because they are dipoles that excite fewer room modes, and subs are slow because they go low and thus excite many room modes. Deal with those, and the sub becomes almost as ’fast’ as the stats.
I have since learned that multiple subs are another good way to proceed, and the conclusion is, of course, that combining those two approaches is likely to give the best results.