I shot a video on this subject, knowing full well it would be controversial. I noticed that while playing around with the LFE + Main settings, you could get bass signal back to the subwoofers when you have speakers set to “Large”.
But setting speakers as “Small” on my AVR and the crossover at 80 hertz yielded the best results. So what gives?
In working with SVS, Ed Mullen helped me understand a few things about Room EQ Wizard, and the results I was getting with the Umik-1.
The first lesson was that a marginally better graph does NOT mean better sound. I could vary the phase of one subwoofer and eliminate a null, but it didn’t sound as good. Trust your ears. I keep the subs at zero phase, adjusting timing using the distance settings instead.
I asked Ed about the problems with the LFE+Main setting for the Denon, also known as Double Bass for Onkyo, and I’m sure a few other terms. Some people will refuse to set their towers to “Small” out of sheer pride, so why not let them get the bass back that is typically “lost” when the fronts are set to “Large”?
When you set a speaker to “Large” or “Full Range” on your AVR, all of the bass on that channel, including signals down to 20 hertz, goes directly to the speaker, and NO signal gets diverted to the subwoofer.
This is bad for several reasons, primarily because, as Ed pointed out, very few speakers are truly “Full Range”. Even their venerable Ultra Tower cannot deliver at 28 hertz the same dynamic output found in their subwoofers, and the Ultra Tower is a truly outstanding tower speaker, especially given the price.
Setting the speakers to “Small” keeps the subwoofer “fed” properly and keeps the main drivers fed more comfortably above the crossover, reducing stress on the amplifier and the main speakers.
Bass requires GOBS of power, and the subwoofers I discuss have comfortably capable amplification, 300 watts RMS/700 watts peak for the very smallest on the list, and as much as 1,500 watts RMS, 5,000 watts peak for the largest.
Asking your AVR amplifier to handle that load only makes sense in a few, very expensive setups. AVR’s are typically rated at 2 channels (Denon X6300 = 140 watts with 2 channels driven) which gets divided up among the other channels. So not much power when you really look at it. That’s a great AVR, but it’s still better to lighten the load.
For those who are still hung up on setting their speakers to “Large”, the “LFE+Main” or “Double Bass” setting duplicates the low frequency signals and sends them to the subwoofer as well, which explains the names.
A setting of “LFE” only (instead of LFE+Main) does not send that signal to the sub, making it difficult to integrate a subwoofer correctly. The bass only comes from the LFE channel of the content, and other speakers set to Small. Really difficult to properly integrate.
Then Ed sent me this EXTREMELY helpful write-up:
“Here is the best way to understand Small/Large , LFE/LFE+Main and the LPF for LFE.
- Small applies a 12 dB/octave high pass to the speaker at the selected crossover frequency.
- Small sends a duplicate signal to the subwoofer and applies a 24 dB/octave low pass to the subwoofer at the selected crossover frequency.
- LFE means the subwoofer gets the LFE channel and redirected bass from any channels set to Small.
- Large sends that channel a full-range signal. This is also known as ‘Full Band’.
- LFE+Main sends a duplicate signal to the subwoofer for any channel set to Large and applies a 24 dB/octave low pass to the subwoofer at the selected ‘crossover’ frequency1.
- When set to LFE+Main, the subwoofer still gets the LFE channel and redirected bass from any other channels still set to Small.
1 Note if the mains are set to Large and the subwoofer mode is set to LFE, there is no crossover selection available for the mains. If the mains are set to Large and LFE+Main is selected, then the ‘crossover’ selection becomes available for the mains. This really isn’t a true ‘crossover’ at all, because the mains are still being sent a full-range signal. What the ‘crossover’ becomes when LFE+Main is selected is the low pass filter setting for the duplicate signal being sent to the subwoofer. In this sense, the user can select the amount of ‘overlap’ between the mains and the subwoofer.
This distinction is not well understood by most enthusiasts, nor is it well communicated by the AVR GUI menu. It suggests or implies a crossover is still being applied to the mains when they are set to Large, when in reality that is not the case.
The LPF for LFE is the low pass filter setting for the LFE channel. Normally this is set to 120 Hz, since that is typically the upper limit used by DVD mixing engineers.”
So yeah, I think you can begin to see why I like SVS so much, and why I worked to become their first ever affiliate. The knowledge they have on hand is world-class.
So basically, with the “Small” speaker setting, your crossover is a “soft” limit for your mains/towers/center/surrounds, with only 12 dB/octave of filter below the crossover setting. The speakers still get the bass signal, just not as much of it.
A tower rated for 32 hertz is absolutely worthwhile, even when crossed at 80 or 90 hertz. Some people might feel their tower’s capability is “wasted” in the small setting, but that’s just not the case. Even as “Small” and set to 90 hertz, the Ultra Towers bring a LOT to the table, more than you would expect!
Even a bookshelf can produce enough bass signal to cause havoc under 50 hertz when set to “Small” and crossed at 80 hertz. I had some bookshelves with passive radiators that had nasty peaks at 40-50 hertz, and I’d blamed it on perfectly functioning subwoofers!
So again, you’re still getting bass signal to your main drivers when set to “Small”.
The crossover setting is more of a “hard” limit for the subwoofer, at 24 dB/octave, which means it really chokes off the subwoofer above the selected frequency. It’s a stronger filter (24 vs 12). That’s why I feel crossover is less about what you’re “keeping” from your towers, and more about what you’re “giving” to your subwoofers.
I appreciate Ed Mullen at SVS taking time out to offer his input on this subject, it has been a confusing one that I understand much better now. I think we both agree that the “Small” setting is best for 99% of applications. I knew what I was hearing, and his contribution above really added a lot to my understanding of the issue.
Hopefully this helps clear it up for you too! Set those speakers to “Small”, even the large ones!
More useful reading:
Getting started with Atmos/DTS:X/Auro 3D