set speakers large or small?

fronts 1.6 thiels 48hz-20khz,thiel center-47hz-23khz,rear thiel power points,75hz-20khz.reciever arcam 350,velodyne sub,should i set all speakers to large?
I have mine set to large, but best advice is try both and see what works for your system and room. That is how I set mine and determined the result.
I own speakers Wilson WP/7's that will play down to approx 28Hz and then start to roll off below that. I still have them set to small. If you have a good sub and it's placed in the room properly and setup correctly it can only help your mains when you really PUSH (over 100db) your system. I again emphasize PUSHING the system! Just observe the mechanics behind it.Let's begin with a larger driver designed specifically to move more air or a smaller driver with less air being moved and working harder to produce the same frequency?
Your main speakers roll off at around 50hz, if you set them to large just where you gonna make up those missing 30hz?.....thats a huge gap in sound. You set all to small, roll off mains at 60, center at 60 rears at 80hz and set your sub to cut off at 80hz.........thats the proper way to do it. Why would anyone tell a speaker that rolls off that high that it is "large"?
If you set the front LCR high-pass at 60 Hz and the sub low-pass at 80 Hz you can expect an overlap region. It's not obvious why you wouldn't just high-pass the LCR and surrounds at 80 Hz as recommended by THX. If the processor has a large-small designation, chances are 80 Hz is the cross-over it's using.

Set all to small. Crossover at 100, twice the low end of the mains. If you set the x/o lower, you will have a dip in the response because the speakers roll-off overlaps with the x/o roll-off. The 'double' roll-off won't sum together correctly with the sub's x/o causing a dip in the response between the mains and sub. (Setting to large will stress the speakers. They're not designed for handling very low frequencies.)
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All this really depends on how well the bass management is within system. I agree most with set to what sounds best though some will disagree. You will have different results from different sources such as dvd or cd. The mains are sufficient for most music as is therefore full signal/large setting would be appropriate in this case however when watching a movie things change. I would say that your mains will handle the full load of the main channel soundtrack but certainly not the LFE track which is entirely independent of the other discrete channels on any given dvd/br. Therefore to say that setting at large is not a good idea is a bit premature. The lfe will never make it to the mains or any other spkr for that matter. It can only be sent by cable to a dedicated sub...powered or not. One advantage of setting spkrs to small is to relieve amp stress by having to work hard to maintain high levels. Sending some of the lower freq's to a sub takes the pressure off the amp to run hard. But, I have founf that depending on the sub this will not sound good in all situations. I know that I could not live with my spkrs cutting off at or about 100hz and the sub taking over from there down. So back to point...whatever sounds better, what suits your needs, and how much flexibility/adjustment do you have with the bm in the first place.
If your speakers and amps can handle a lower setting than 80hz then ignore THX cause you gonna enjoy it more if you do. THX was invented and its more about consumer speaker size than anything else.
You better try different set ups and choose the one that suits better to your hearing likes. Some like big speakers, others dont.
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m/n sf128vx1o its about 12 years old,friend gave it to me.i called velodyne and they said to set the receiver at 80 and the sub crossover at 100.there is not a on/off direct switch on the sub
Reason for setting sub above xover point of recv'r/preamp is to make sure the range transfer for lack of better phrase is not missed. Example...if you set sub to 60 hz and recvr to 80hz....the info between the two settings would not get to sub therefore setting sub at or just above recvr/bass management setting will ensure there is no gap or more important too much overlap.

BReynolds is correct about the 100hz would be able to localize the sub with those higher freqs being sent to it. Sub should disappear in room so to speak. You should hear/feel it but not tell where it actually is. Do 80hz and listen to various material with large setting and small decide which is fuller and smoother.
Sounds below 80 Hz can be localized. The issue to address is not localization, but rather, a smooth, linear transition between mains and sub. It might be possible at 80 Hz, but highly doubt it could be done any lower with the Thiel 1.6. Velodyne's recommendation may be based on the fact that subs generally have a rising response in the mid-bass, by having a little 'gap' in the crossover it could help smooth out the hump, or the logic could be to help tame common room modes that often occur in the same frequency range. No matter how one looks at it, calibrating a sub is difficult. It requires time and patience.

"Sounds below 80 Hz can be localized" is a sweeping statement of purported fact. Can you provide a reference, a refereed JASA article, for example? It's been decades since I worked in psychoacoustics, and my memory may be faulty, but IIRC we're not vary capable at localizing LF sounds.

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Found a few references. In a nutshell, Interaural Level Difference (ILD) and Interaural Time Difference (ITD) are the means for interpreting the location of a sound source. Level difference is mostly used for high frequencies due to wavelength relative to head size, yet the time difference is identical for low frequencies as for high. Time difference allows for low frequency localization. (See the abstract at this link, The precedence effect also comes into play in a typical domestic room where one is listening relatively close to the source, and level differences are aided by proximity reinforcement. Try listening to sine waves coming from only the left or right channel. You can easily identify which speaker is producing the sound unless the frequency hits a room mode, then ringing may obscure the location cues. More reverberant spaces also make it more difficult to localize, even for high frequencies. Location cues tend to be easily obscured, and room acoustics can affect perception, for better or worse, making it difficult to determine a specific cut-off frequency. It's a convenience to say frequencies under X Hz are nondirectional.

This link suggests learning is involved:

This link goes into greater detail:

One more:

Only the abstract of the JASA article seems relevant, and it suggests that the model they tested and human ability to localize LF sounds is poor, especially in other than anechoic conditions. The link didn't get me to the JASA article, so I was unable to see a breakdown of their results, but I'd guess the octave band centered at 125 Hz was by far the most localized.

I did enjoy the reference to the binaural processing model of Lloyd Jeffress. My primary interest when I was a post-doc was binaural processing, and I thought the Jeffress model of neural-spread made much more sense than the equalization-cancellation (E-C) model derived from the theory of signal detection (TSD). Jeffress was a nice guy and helpful in encouraging and critiquing my work. I did a study of the detection of sinusoids in computer generated noise waveforms in which I adjusted the phase of the sinusoid in the noise waveforms. I imagined it would be a crucial test of the theories, and the detectability did vary widely, but not as predicted by either model. By that time, I was losing interest, and never published the work even though I was encouraged by Jeffress to do so.

This research was done with earphones, so we could control the signal that was delivered to the ear, and the lowest frequency was usually 250 Hz. We did have an anechoic chamber that went pretty low, but transducers were inadequate for LF work.


Here's a professional and hobbiest experience with all this:
I recommend that you should strongly consider doing what THX found works, and that's to cross over your passive speakers system at 80hz, and let the active sub handle the much more demanding bass dubties - even with larger, more full range speaker systems. This free's up the receiver/amplifier to better handle the rest of the sound spectrum, relieving it of taxing bass dubties. This is especially helpful on receiver systems, with limited current deliver, and with passive speaker systems which offer limited efficiency and control going through passive crossover networks. Overall, you'll have much better efficiency, dynamic power, and range from the system this way.
This must be qualified however in direct respect to a "properly setup" and engineered sytem, fundamentally! Where people run into problems -and thus make all kinds of adjustments to overcome fundamental setup and acoustic issues - is that they most always never properly address issues such as critical speakers and seating, setup, and the acoustics in play, because they don't know what they're doing. As is too often the case, in directly adressing the main question being posted here, is that what happens is speakers will end up in acoustic holes in the bass response, making it impossible to get flat dynamic, accurate resonse from the system. Either the speakers, or the sub, or both will be sitting in a hole in the bass response, yielding a weak bass response. To try and compensate for this, what more often than not happens is that they'll move the crossover point to where things sound fuller. Or they'll crank up the bass/sub to try and overcome acoustic issues - and thus never properly adress the fundamental problem.
What needs to be done is to assure that the speakers are first flat (or at least not in a hole) at the critical crossover reigion. Ahd that goes for the sub too! Then, even with EQ assisting things, you can attain a solid, flat, accurate resonse from the system, with solid dyamic potential and range. You couple this with good bass managment in the above type of system, and you get simply tremendous performance results.
Basically, it all must be taken in context. Everything must balance out. If you ignore or aren't ware of all the issues in play, and don't properly adress things, you can easily make adjustments elsewhere in the system to try and mask over the real fundamental problems.
You can then see why results vary so extremely in regards to setting parameters and preferences from person to person, setup to setup, room to room, and equipment to equiopment. It's simply way to easy to not adress issues such as discussed here, as well as others such as toe-in, aim, speaker spacing, speaker and seating locations, speaker height, acoustics in the room, frequency response, water-fall plot, RT time, phase issues from speaker to speaker and/or seating location, speaker to boundary
interaction, etc, and so on.
Takes time to learn all of this, and it all adds up like ingredients in a master chef's recipie, or an experienced mechanic tweaking a race care.
If you don't know what does what, you're limited in results.

--Pertinent Quotes: "The only source of knowledge is experience" (Albert Einstein)

"It's not that I'm so smart, it's just that I stay with problems longer." (AE)

"Sometimes one pays most for the things one gets for nothing." (A.E.)

"A person who never made a mistake never tried anything new" (AE))

"I think and think for months and years. Ninety-nine times, the conclusion is false. The hundredth time I am right" (AE)

"The important thing is not to stop questioning. Curiosity has its own reason for existing."(AE)

"I am passionately curious about finding the truth" (AE)
To expound a bit further - for all you 2 channel audiophile purists and full range stereo speaker devotees - yes, you're going to certainly get more perfect coherence running a full range speaker system, full range (and maybe adding minimal subwoofer integration to the very bottom registers, .1 configuration, etc, for home theater). A main trade off's here includes getting coherent full range integration of the sound, but most always yields limited dynamics and impact from the system, from relying on typically dynamically limited passive speaker systems to provide the weight and authority to the overall sound. You cross things over with bass management, to an active woofer in the system, and the efficiency and power just went up! You get higher efficiency speakers, and or even active speakers on the top end, and you have even more dynamic range and impact potential!
Of course, again, integrating a separate woofer speaker with your mains, and you will face a trade off of perfect driver to driver integration, from crossover issues, phase, slope, whatever. Still, the trade-offs here - for most all multi-channel/ht applications, far out-weigh the negatives!
Anyway, opinions will vary. But every multi-channel, full range, passive speaker system I've ever heard lacks proper dynamics and impact, compared to integrating an active woofer in the chain - at the very least.
I concur with pretty much everything Queefee wrote, but add this cautionary caveat to his Pertinent Quotes: Just because AE was a brilliant physicist does not imply he was a brilliant philosopher. There are many things I'd rather know through reading, secondary observation, or generalization rather than direct experience.

Palen, the THX rationale is based on the contention that we are not well able to localize frequencies below 80 Hz, a contention I contend that is based on psychoacoustic evidence.

wow,a lot to take in,i did use a spl meter to set it up but my room is a little strange i think the best thing i can do is try differant settings and move my speakers around a bit,not much room for movement and cannot move sub at all.i would like to thank you all even though a lot of it was over my head
Set your front mains to large. Your center channel to large if you can, but try it in both to see what works best for your room. The LFE channel in movies is separate from the bass information that is routed to the individual speakers, so you aren't robbing from your sub by setting individual speakers to large. I have my Focal 826V mains set to large and the movie/concert watching experience is much more visceral that way.