Originally Posted by fartucci
I'm sure there are others on this forum who understand these issues much better than I do. I was thinking that if the front speakers are set to large, and the subwoofer is set to on, then the LFE channel would go to the sub (as well as any low frequency sounds in the surround channels), and any low frequency sounds in the front channels would go to the front speakers. As opposed to setting the front speakers to small, in which case any low frequency sounds in the front channels would also go to the sub. I'm just wondering if one setup is better than the other.
Yes, the LFE channel will always go to the sub no matter what size the speakers are set to. And, yes, the low frequencies below your crossover setting(s) from any speakers that are set to SMALL also go to the sub.
What are the benefits of setting a speaker to SMALL?1.)
The low frequencies from those channels that ARE set to SMALL are sent to a speaker, the subwoofer, that is specifically designed for reproducing low frequencies. In addition to usually having a larger driver a sub has a dedicated amp which is often much more powerful than the amps in a receiver. Low frequencies are harder for an amp to amplify than higher frequencies (see below).2.)
In setting a speaker's size to SMALL, you relieve it of the burden of having to reproduce the lowest frequencies. This results in cleaner reproduction of those frequencies that the speaker IS asked to reproduce. In the case of your XQ40s, even though this will not benefit the UniQ driver, the lower drivers will still benefit. So, with an 80Hz crossover, the lower drivers will be relieved of having to reproduce the full output of those frequencies below 80Hz. Yes, the receiver's crossover is not a brickwall and does have a slope (usually 12dB/octave) but still, the signal sent to the speakers will be down 12dB at 40Hz and even lower beyond that. My XQ5s still have fairly significant output at 32Hz. So, even though the speakers' -3dB point is 45Hz, they do still have significant output below that and they benefit from not having to reproduce frequencies even lower than their 45Hz -3dB point.
You will not be "wasting" the potential of the lower drivers with the speakers set to SMALL. The lower drivers in the XQ40s are crossed in with the UniQ driver at 400Hz. This means they WILL still be used significantly to reproduce those frequencies from (in the 80Hz crossover example) 80Hz to 400Hz. This is more than 2 octaves. The speakers will be able to reproduce those frequencies from 80Hz to 400Hz with more finesse than they would be able to were they burdened with frequencies lower than that. The main channels in a movie soundtrack can contain information that is as low as 20Hz, maybe even lower. Those speakers cannot reproduce that. So, it is best to let a subwoofer, which is specifically designed for it, reproduce those frequencies. In fact, if you set the speakers to LARGE, you will actually miss out on those frequencies encoded in the front channels that are below the speakers' capability. So, even if it is not capable of reproducing them all the way down to 20Hz (or lower), a sub will still be more capable than the speakers and you will be able to reproduce more of those lower frequencies encoded in those channels.3.)
When you set a channel to SMALL, the amplifier doesn't have to amplify the frequencies below the crossover setting. So, relieved of having to amplify those lowest frequencies (which I said above are the hardest to amplify), an amp can amplify those frequencies it IS asked to amplify more cleanly.
So, when your speakers are not LARGE (and XQ40s are not LARGE), setting the speakers to SMALL results in cleaner output from the amps and cleaner reproduction by the speakers. And, provided it IS capable of it, cleaner output of the lower frequencies by the sub. It is a win/win situation.
Now, generally, movies contain more low frequency info than music. At least a greater quantity of it. Whether you want to reproduce your 2-channel music with the aid of a sub is a personal preference. Theoretically, with a perfect setup that provides a smooth and flat transition between the main speakers and sub, the sub should only enhance the overall capability of the speakers+sub combo to reproduce music. But the reality in many instances, unless you make an effort to ensure a smooth transition (with EQ, for example), this is not always the case. Music listening is generally more critical listening than movie listening, so any faults between the speaker and sub integration are usually much more noticeable. So, many people prefer to listen to their 2-channel music traditionally, with 2 speakers, whether they are truly capable of full-range output or not. There is also an arguable but understandable 'purist' point of view that would posit that a subwoofer should not be used for 2-channel music; it was recorded for 2 speakers therefore that is how it should be reproduced.
Personally, as I said, I listen to 2-channel music both ways. Sometimes I supplement it with a sub (speakers = SMALL), sometimes not. Which way I might listen can depend upon the characteristics of the music itself or it might just depend upon what I feel like doing. My setup is far from perfect as far as having a flat overall frequency response is concerned. Sometimes, depending upon the music, I find the subwoofer to be distracting. My receiver can be set to a 'pure direct' mode which bypasses any bass management (and time management) settings and instead sends a full-range signal directly to the speakers. In doing so it bypasses much of the componentry within the receiver that is dedicated to processing the sound with the end result (supposedly) being cleaner, unmolested (if you will let me describe it that way) sound. Most receivers nowadays feature some sort of mode like this. The main intention of this mode is for 2-channel music reproduction without bass management. With my receiver, I can switch to this mode with the push of a button. So, I can leave my speakers set to SMALL all the time. Using this mode bypasses the bass management so the speaker size settings are irrelevant. Point being, I do not have to go into the receiver's setup screens to change the size to LARGE just to use them for 'full-range' 2-channel reproduction.
The low "E" string of a standardly tuned 4-string bass guitar is tuned to ~41.2 Hz.
The low "B" string of a standardly tuned 5 or 6 string bass guitar is tuned to ~30.9 Hz.
The low "A" key of a standardly tuned 88-key piano is tuned to ~27.5 Hz.
Many other instruments and synthesizers produce considerably low frequencies as well.
So, an argument CAN be made that 2-channel music listening CAN benefit from the use of a subwoofer.
Upshot? Your XQ40s should be set to SMALL, particularly for movie reproduction. The 80Hz crossover that is recommended for your 3005s is also ideal for the XQ40s. How you use them for 2-channel music reproduction is up to you. Very most likely your receiver has a setting or mode which provides 'pure direct' output which should allow you to switch between SMALL and LARGE easily.
Drawbacks of setting speakers to SMALL? There aren't many. The main one is that you may lose a very slight amount of stereo bass information which MAY possibly be noticeable with 2-channel music. There IS stereo bass information below 80Hz in stereo music soundtracks. But the dogma is that bass below 80Hz is not localizable. This is one reason that 80Hz is oft-cited as an ideal crossover point for the subwoofer. In reality, in most of our imperfect listening environments, frequencies below 80Hz probably are localizable. So, you can detrimentally lose some of the stereo bass info as it is sent to the subwoofer to be reproduced in mono. And, as I said, if your room, setup, and subwoofer are not ideal, critical 2-channel listening with your subwoofer may not be ideal.
Hope this helps. Quiz on Monday.