<font color='#000000'>Hi All
I have been trying to explain the Large vs Small set up
to my Clients and Audiophile friends for years
It always seemed to create a heated debate and usually was
met with skeptisim.I thought it must be the way I am explaining
the reason for the set up. I came across this article that explains the reason
in simple understandable terms The author makes his case clearly
Read it, Frame it ,Hang it on your Home Theater Wall
Read it often
Enjoy
Oh dear...how to begin?
I was asked by a college to pop over here and provide some feedback as this is a topic I have been very deep on for some time.
Yet I hesitate. I don't know if the forum is the right medium and what I have to say is for many unpleasant, and for others will mean the realisation that they have been living a sonic lie.
Still, for what its worth...
I started by reading the soundstage article, and liked a lot of what Mr. Blackburn had to say, especially as it relates to crossovers and the need for each complement (main speaker and sub) to competently reach across the crossover point. Such is the source of linearity if the crossover itself is strict in its curves (though I should note that certian cross-overs, such as THX's, actually count on the speaker exhibiting a natural roll-off at or near the crossover). I also liked that he calls the bluff on the non sub subs (or as I like to call them: bass modules).
I'm a little tickled that he opens the piece with a rather definitive "disclaimer" of sorts. I guess he must have known his conclusions were easily questioned.
But alas, the essay totally falls apart at the very notion that there are "home theater" subs and their are "music" subs. I am diametrically oppose to this point of view. Is Mr. Blackburn crazy? Not likely. So why does he find some subs better for one or the other? He doesn't. What most likely is the reality is that he categorizes "good" subs as "music" subs, and acecpts others as "home theater" subs. I don't care where you heard it, it is just wrong to suggest that a system should apply a boost of any kind in the 40-80Hz region when watching a movie. For crying out loud, 99% of the movies I watch contain substantial music. Music! Does no one see the fallacy of the argument?
Lets go back to the source for a moment: The motion picture soundtrack. The sound artist/engineer assembles (or I like to use the word crafts) the soundtrack on a dubbing stage which is calibrated to the same rules as the commercial theater where the work will first be appreciated. These rules, trust me, result in a sound far more linear than you can ever hope to get in your home (no matter what you've spent on hardware) unless you have some of the gems that cinema hardware include. Dolby's staple cinema Dolby Digital decoder (CP500) has separate 1/3 octave 27 band eqs for the front channels, full octave 12 band eqs for each surround channel, and a digital parametric eq for the LFE channel/sub. The rules for set up are: each channel (including the LFE/sub within its band) gets an ISO 2969 response. That is, flat up to 2 kHz and then rolled off at 3 dB per octave (which in the large room yields a perceived flat response). Quick side bar: this is the very reason for THX's 'Re-Eq' feature. Point is: there is no boost/dip or anything else done to the 40-80Hz range. Why the #### should we or our subs do anything of the sort? Yes there are subwoofers on the market which offer a 'switch' to insert a boost but this is just plain wrong. If you like it (and I think Mr. Blackburn does) that is your prerogative, it is your right, it is your taste. But please don't pass your preference as some definition of 'proper' home theater sound.
Next I read the article on home theater subs. Unlike the one at soundstage, I found less of value. Again to suggest that a boost is (quote) "needed" in the 40-80Hz range is an ugly ugly statement. Although I intend to research it further, I'm hard pressed to recall a receiver or processor which does what Mr. Blackburn suggest: Forces a high-pass to the mains when the LFE channel is turned on. Heck, I'm hard pressed to think of a unit which has a magical "on/off" switch for the LFE channel. If yours has one, or behaves as Mr. Blackburn suggests, it simply means it's bass management is pretty piss-poor. Write to me and we'll find you a model that behaves a little better.
Suggesting that you get 6 subwoofers is a dramatic misalocation of funds. Sure it would be cool. The lads at Widescreen Review do it, but everything in their main system is by any definition excessive (which has often puzzled me: wouldn't I rather know how a DVD is going to look or sound on a real world system? Whatever...).
Since we're rolling on the subject, I'll touch on the issue of setting speakers as 'large' vs.'small'. When you boil it down, there are really only two ways to get it "right", if your definition of "right" is faithfulness to the signal, which in the context of subs, means linear response (or as linear as possible) within the band in question. You can either (A) set all speakers to large or (B) set all speakers to small. Don't worry, I'll explain why any combination in between is costing you sonic truth.
Lets go over the first option: set all speakers to 'Large' and have a single subwoofer for the LFE channel. Any processor I've seen simply requires you to say "yes, I have a sub" and it will send the LFE channel to the sub-out jack (incidentally, if you say "no sub", a responsible decoder should send the LFE data to the main left and right, but we're assuming a subwoofer for this discussion). This is actually a pretty cool setup because it 'emulates' the set-up in a cinema: In commercial Dolby Digital there is no bass management. One could further argue that in the cinema, the main channels naturally have a low end rolloff somewhere under 40Hz just because that's how low the stage speakers go. In Mr. Blackburn's defence, the idea of a sub for every channel is in essence the same thing, only you are spending unheard of money to extend the response of each speaker down to 20Hz. Nothing wrong with wanting linear response down to the nether regions for each channel but there is a better way to do it (we'll talk about how latter). Short of the 'sub for every channel' route, this set up is next to impossible to balance. For one, every channel must be able to 'handle' a full range signal without risk of physical damage, thought they may not actually voice the nether regions. Such speakers are not so hard to find. What is impossible is getting a similar low end response from all 5 speakers. With any conventional choice of loudspeaker model, the centre will always exhibit less low end extension than the mains, the surrounds probably even less. So you get a real unbalanced sound system with "good" low end response from the mains, "poor" extension from the centre/surrounds, and "great" extension from the sub/LFE.
People's first instinct is to set their centre and/or surrounds as 'small'. Good move but not a complete solution. Unless you have one of a hand-full of exotic decoders, the bass from the centre/surrounds will get sent to the subwoofer. Now you end up with centre and surrounds having dramatically better bass than the main left and right. And if you try to tell me that your mains are as good or very close to yours sub's extension, then you are either deceiving yourself or you bought a really lousy sub which is not a good complement for the rest of your system.
Having said that, people then turn to see if their processor/decoder will let them at least "copy" bass from the main left and right to the sub. Many will let you do this and it sure sounds like a plan: now all speakers have the same low end extension as all the bass is coming from the sub. Not so fast: You have asked your system to send bass from the main channels to two transducers: the main speaker and the subwoofer. This is going to net you a 3dB in room gain that you don't want, within the band which both the sub and main speaker are voicing. Just as an example, if your crossover is nominally 80Hz and your mains are good to 35Hz (lets be generous), by copying bass from mains to sub, the region of 35-80Hz will be in-room 3dB too high. You cannot adjust for it: If you lower the sub level, you lower the bass from the other channels (remember we've set centre and surrounds to 'small').
So now we've come full circle. We set the mains to small and voila: All speakers are set to small, the sub is voicing all bass, each channel is in a practical sense getting identical low end extension.
There are two gut or knee-jerk reactions to this: First, people with tower or floor standing speakers feel they are in some arbitrary way "wasting" their speaker if they set it to small. This is so unfortunate and so far from the truth. As noted by Mr. Blackburn, a speaker should have linear response below the nominal crossover point anyway for certain crossover designs, which in the case of an 80Hz point means being good to at least 40. You are NOT "wasting" a speaker by setting it to 'small'. The second reaction by many many people is that they "prefer" the sound, especially music, when they set their speakers to large. Here is where I start to really upset some people. You don't prefer your mains set to large. What you prefer is not hearing your subwoofer. In other words, you did not buy a good enough subwoofer. Dare I say it: You bought one that is not "musical" enough for your taste. Maybe its one of those oddities which provide the absurd boost on the 40-80Hz region, I don't know. But if you have a "good" sub, you would prefer setting your speakers (no matter their physical size) to small.
Just a couple weeks ago, on this very forum, we had a guy who was in the process of buying speakers and actually had a set in his home but hadn't finalized the deal. He liked music with the floor standing mains set to 'large' and was looking for advice on spending a little extra on even bigger mains with the intention of leaving them as 'large' for music and home theater. He took my suggestion of spending the extra money instead on a better subwoofer and was elated with the results: He kept the first pair of floor standing speakers and is running them as 'small'. The sub is so good that he likes his music with it even better than the mains alone running large.
So, rather than going through the expense and complexity of 5 + 1 subwoofers, simply get a really good, linear, honest subwoofer. If that's not enough power or output, daisy chain a second one and stack it on top the first one.
My mind is a little blown now from trying to impart so much so quickly, and I'm definitely suffering from a coffee deficiency at this point. This is infinitely interesting stuff and I invite feedback but for now, I've GOT to get to Starbucks.
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Brian Florian
Editor, Canada
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I would only add two points to this well written article
If you still think your mains sound better set to Large
Then you most likely don't have enough Subwoofer or your subwoofer is inadequate
Or you have not placed your subwoofer or woofers in the correct location
and have not optimized your system</font>
