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From    : MARC BAMFORD                         
> I have been following this echo for some time now (yes, all the way 
>from Sydney!) with increasing frustration at the car audio vs home 
>audio debate (I enjoy both).  In a vain attempt to distract everyone 
>with a question,  I was wondering if anyone could help answer the 
>following about my home theatre setup.
 
Glad to see you and New Zealand back with us again. Now just wish we 
could get the Hong Kong crowd back in here again. They REALLY were 
into the high end home stuff! We missed all of you.
 
>1.  I have a pair of small 2 way vented speakers as my mains in my
>  home set up and a single sealed 12inch sub running via a small 
>  dedicated amp from the lowpass output of the Yamaha Pro Logic 
>  decoder (VSX1050).  Even though the main speakers are not 
>  particularly "bass heavy" do I need to run some sort of high
> pass filter on them to prevent interference from the sub?  
 
No, I don't believe that you will need to bother. The small mains 
probably have a built in high pass due to the nature of cabinet size,
et al. A lower sub frequency crossover Fc could leave a hole in 
frequency response coverage on that system. Locate the sub at the 
center front location, which will minimize the displacement effects 
since it's coming from the "window on the wall" is a more natural 
direction for that band of bass.
 
> 2.  The lowpass output of the decoder has an Fc of 400HZ and there 
>   are lots of directional clues coming from the sub - what is the 
>   best Fc to use and how do I do this  - at line level (before the 
>   amp) or at speaker level?
 
That Fc does sound much too high... but then you didn't say just what the 
response of those main speakers are, and I agree, directional info is there. 
Subs work best below about 200Hz where the fundamental frequencies made 
by the source material reproduce as pressure changes in the room and are 
nondirectional and diffuse, even throughout the room except where room 
node cancellations cause the sound to wink out which needs room treatment 
to cure.
 
My current "main studio monitors(and keyboard gig/personal sound system",
if needed)" starts to fade at 120Hz (3db down point and loses about 6dB 
the first octave below,that and about 12 more the next octave down, so 
I have the 18" woofers of the (2-1-18" Gauss) currently setup at for about 
90 Hz, on a 6dB/octave electronic crossover and running an EV 100 WHAT? 
per channel in the studio or in mono mode as a live system though with 
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