Bass Mgmt, the Right Stuff comments

G

Guest

Guest
<font color='#000000'>Gene,

I read your &quot;Bass Management, the Right Stuff&quot; article and thought I would comment.

I think you're right about bass management not being implemented correctly on many HT processors, both prepros and receivers, that are on the market today, even those with selectable crossover frequencies.

From my persepective, the proper implementation of a LPF/HPF crossover combination should result in a smooth transition across the crossover boundary without serious peaks and dips at or on either side of the crossover boundary.  This is easily accomplished with a symmetrical (LPF/HPF) 24dB/octave Linkwitz-Riley (L-R) crossover.

Actually the manufacturers typically provide a LPF that is designed as a 24dB/octave L-R, but it simply doesn't match with their misguided attempts at a HPF, which is unfortunately adopted from THX.

In addition to your LPF perspective, my beef is primarily with the implementation of the HPF.  Almost all have a 12dB/octave 2nd order HPF.

Problems arise because the HT processor manufacturers (actually the DSP chip hardware vendor who supplies the software algorithm i.e., Cirrus, Motorola, others) assume you will have a speaker with a perfect 12dB/octave acoustical low frequency rolloff at the prescribed crossover frequency selected, usually 80Hz.  Their misguided dream is that this 12dB/octave electrical + the speaker's 12dB/octave low frequency acoustical rolloff will sum to a 24dB/octave L-R HPF.  


Unfortunately that dream couldn't be further from the truth.  Many bass reflex speakers (most popular type these days)have something like an 18dB/octave low frequency rolloff or more at varying frequencies and are very unlikely to provide a satisfactory transition with any of the HPF crossover frequencies selected in the HT processor.

Typically, the only speakers that meet the 12dB/octave acoustic rolloff are sealed acoustic suspension speakers and THX rated speakers.  Only the THX speakers start their 12dB/octave acoustic rolloff at 80Hz, sealed speakers can be at various frequencies, like 46Hz.

To sum it up, not a pretty picture  


This is the primary reason I use the following:
large mains (towers -&gt;  -3dB @32Hz)
sub
small center
small surrounds

To get around this annoying HPF problem (I could never get a good match through any HT processor), I implement a time aligned 24dB/octave Linkwitz-Riley LPF/HPF active stereo crossover between the L&amp;R mains and sub(s).  In my case I use a crossover @60Hz, because it produces the least problems with my room modes and is about an octave above my mains -3dB of 32Hz.

This means in the speaker setup menu of my HT processor, I define  sub=No and have nothing plugged into the sub output on the HT processor.  This means all LFE bass and all re-directed bass from small center and small surrounds is sent to the main L&amp;R speakers+sub.


This provides well integrated low bass for both 2-channel and 5.1.

Any comments?</font>
 
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gene

gene

Audioholics Master Chief
Administrator
<font color='#000000'>Bruce;

I like what you are saying.  I wrote that article long ago and its in need of a major revamp.  My time is limited tonight, but perhaps we can exchange emails and if you are interested, assist me in updating the article based on your feedback and the current trends that I have been finding with hardware we have been reviewing.  Please email me when you have a chance.  Thanks for the great feedback!

BTW, your set-up sounds a lot like mine, but depending on your processor, I have a way for you to still use the sub out and I have a list of processors that have the flexibility I would like to discuss with you.</font>
 
G

Guest

Guest
<font color='#000000'>Gene,

I'll PM you when I get a chance.

Also, if you take a peak in the &quot;Member Systems&quot; thread, I listed my complete system layout --without pricing-- in the &quot;How much is your sys worth&quot; thread.

You can get a better picture of the components I'm using and how they are connected.</font>
 
G

Guest

Guest
<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>
Guest : <font color='#000000'>To get around this annoying HPF problem (I could never get a good match through any HT processor), I implement a time aligned 24dB/octave Linkwitz-Riley LPF/HPF active stereo crossover between the L&amp;R mains and sub(s).  In my case I use a crossover @60Hz, because it produces the least problems with my room modes and is about an octave above my mains -3dB of 32Hz.

This means in the speaker setup menu of my HT processor, I define  sub=No and have nothing plugged into the sub output on the HT processor.  This means all LFE bass and all re-directed bass from small center and small surrounds is sent to the main L&amp;R speakers+sub.


This provides well integrated low bass for both 2-channel and 5.1.</font>
<font color='#000000'>This is by far the best way to configure Bass Management for both 2-channel and digital theater surround. &nbsp;I'm doing the same thing with my HSU subs, except I'm crossing them over @ 51Hz.

Further, instead of fretting about variable crossover frequencies in a processor, I can simply call Dr. Hsu, buy the appropriate IC, and insert it into the black box to change the frequency.

I've got the Hsu's mated with Carver AL-III's and there is absolutely no way I'm about to compromise the integrity of my 2-channel audio, as I'm sure is the case with you. &nbsp;Kudos for using some critical thinking to avoid a lot of the Bass Management &quot;issues&quot; inherent in HT.</font>
 

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