Selecting "LFE Only" = no signal to sub

Hey folks. I have a 990 running five 2200 monoblocks, which power Dynaudio Focus 220 tower speakers, Focus 200C center channel, and Focus 110 rear surrounds.

I just completed the system with a Dynaudio Sub 500 powered sub unit. To connect it to the 990, I ran an RCA from the 990's SW1 Preamp Out, and connected it to the back of the Sub 500. On the sub, I've set its crossover frequency to 'flat' to allow the 990 to perform the filtering.

In the 990 setup screen, I kept the speaker xover settings as they were -- these settings have worked fine for some time for both stereo listening and home theater listening:
Front L/R: 40 hz
Center: 40 hz
Rear: 40 hz

I didn't change speaker size either:
Front L/R: Large
Center: Small
Surr L/R: Small

For my first attempt to configure the sub, I set Subwoofer to "LFE Only", which the instruction manual says "If you have very large front speakers, you will probably get the best results with the 'LFE Only' setting." It doesn't say anything else about this setting, nor does it define "LFE" though I can assume from context it's low frequency something or other. My front speakers aren't really HUGE but I wanted to see what happened. Result: No signal whatsoever being sent to the sub. None. Zip. Zero. Not my 20hz test tone, nothing.

So then I switched Subwoofer to "L/R+sub", which the manual states "blends some of the bass from the left and right speakers to the subwoofer." When I did this, the sub kicked on and performs like a champ with 20hz, 60hz, normal music, etc.

Just curious why "LFE Only" doesn't allow any signal to go to the sub -- what is the point of this? And does it seem like "L/R+Sub" is the correct option for me?

SACD through the 7.1 analong inputs works with the sub too -- I dont' know that "LFE" and "L/R+Sub" apply when using 7.1 as the input mode; I assume the ".1" sub information in the 7.1 signal overrides both of these settings (?).

Haven't tried DVD/BluRay yet to see how 5.1 surround works. Again, not sure that "LFE" and "L/R+Sub" apply for this. I assume the ".1" information in the 5.1 signal overrides both of these settings. (?)

Thanks for your help. Can't wait for the 998!

-Jeff

The 990 won't send the LFE (Low Frequency Effects)signal to the sub if your front speakers are set to large. It assumes if the front speakers are large that all the low freq stuff is going to them. I would suggest playing with the crossover and moving it up to 80 hz to let the sub do the hard work and save the power of your amp for the main speakers. The sub is designed for the low freq high power stuff so why task the mains with it. Although I am sure your mains do well at 40 hz they are actually working their hardest at that point. If you use the sub for everything less than 80 hz there is more power available for your mains to work where they are more well suited. Change your mains to small and let the 990 do the distribution.

Is it safe to assume the 970 is the same on this subject?

The 220's are pretty hefty speakers. Their -3dB point is a good 5Hz lower (or more) than my old Paradigm towers. That being said, now that you have a sub, you might want to experiment with running the fronts as "small" and using either the 40Hz or the 60Hz crossover point. The center and surrounds both deserve to use the 60Hz crossover point, as the 40Hz crossover is almost directly at the center's -3dB point and actually about 5Hz below the surround's -3dB point. You could even experiment with the 80Hz crossover point for those.


The LFE signal is the ".1" channel of 5.1 sources - it stands for "low frequency effects." When set to "LFE Only" the sub only gets that channel. Any test tone played to the fronts will go solely to the fronts when they are set to large and the sub is set to LFE only.


The "LFE Only" option only exists when using fronts that are set to "large". It is actually the most pure option for this scenario, as none of the low frequency audio being sent to the front speakers is duplicated in the sub and no speaker is asked to play frequencies lower than it can reproduce comfortably. You've told the 990 that your fronts can handle everything when you set them to "large", so it does exactly that. Only the dedicated subwoofer signal - the LFE channel - goes to the sub. The "L/R+Sub" option is there as a way to produce what's sometimes called "double bass" - the low frequencies still go to the fronts, but they also go to the sub, so two speakers are reproducing the same audio and "doubling up" on those frequencies. In reality, the fronts are rolling off. With a 40Hz crossover set for the "large" fronts, there's not a lot of overlap.

Which is right? Personally, I'd suggest spending some time running the system with the fronts set to "small" and the crossover points I mentioned earlier. This could be considered the most "proper" approach, since even those big Dynaudio towers aren't truly "full range" (which would mean flat down to 20Hz if taken literally). In this scenario, the sub will simply be on, with no option for "LFE Only" or "L/R+Sub". On the other hand, there is no one right answer. The goal is to produce sound that pleases you. If running large fronts and the sub set to "L/R+Sub" pleases your ear, do it.


If it's a multichannel SACD, there's probably an LFE channel. Same for DVD's and Blu-ray Discs. That LFE channel will go to the sub no matter what else you do. Redirected bass from the fronts may or may not, depending on your settings (large fronts and "L/R+Sub" and small fronts will both send bass from other channels to the sub). The bass management settings still apply for the 7.1 analog input as long as you don't set all speakers to "large". They also apply to any digital audio input.

As far as the "LFE Only" and "L/R+Sub" settings for the subwoofer when the fronts are large? I believe so, yes. As far as what "large" and "small" mean, most definitely yes. Bass management on the two processors is similar in most respects, although the 7.1 analog input is pretty different due to the 970's analog bass management option.

Fascinating, thanks for the detailed responses folks; I've learned a lot. I like the suggestion of using the -3dB points as guides for setting the highpass for the various speakers, and I'm fortunate to have an old Home Theater magazine SPL plot to go by for these speakers. (however this plot is using the Sub 250 rather than the much larger Sub 500).

I will definitely set the front speakers to 'small' and play around with the settings. It makes sense. Now if we only had the same amount of great information on when the 980 will be available!

-Jeff

The -3dB points are the best place to start when selecting a crossover point. The catch is that you have to go to that point and then move up a ways - crossovers aren't sheer cliffs around which signals drop straight down, they are slopes that start turning down to one side of the crossover's given number and tail off for a good ways beyond. The plot you linked is a great resource for understanding this, as it shows why a 60Hz crossover for your mains could be a good idea.

I set all of my speakers to 'Small', which changed the Subwoofer from "L/R+Sub" to "On"; and, I've set the highpass to 60 Hz on my Focus 220 tower speakers (and also on my center & surround).

I fiddled with crossing the Focus 220 towers at 80 Hz highpass, and it sounded OK. But I ended up dropping it to 60 Hz, when I realized the notes in a walking bassline didn't have the same intensity for each note as it was nearing the bottom frets on the E string.

Now it sounds phenomenal. It was hard to acquiesce to my 990 that my speakers were "small", and it took a lot of restraint to keep turning down the level on my brand new sub until I couldn't really notice it. But I can't believe how much of a difference a capable sub makes in stereo listening, particularly for jazz and metal.

Thanks!
-Jeff

I'm glad to hear that the system is working well! It's not unusual for folks to lean toward running big tower speakers as "large", but as you've found there are often cases where it actually sounds better when you let the sub step up and do its job. I had similar good luck with the 60Hz crossover point with my old Paradigm towers.

what speakers do you run now, Gonk?

I still have Paradigms for my rear surrounds (Studio/ADP v2). Fronts are Outlaw BLS, center is Outlaw LCR, and side surrounds are Outlaw SL. I've got some notes about them in the speaker review in my sig.

990 nOOb here. Picked up a used one last week. Man what an improvement over my 10 year old Rotel prepro. Haven't had a lot of time to watch movies, but I've been spinning CD's a lot since I got the 990 up and running.

I've got B&W Nautilus 804's and HTM1 center, a mishmash of surrounds, B&W sub and a pile of Rotel 200wpc amps.

Being able to do bass and distance management on the 7.1 analog inputs is perfect for my situation.

I'll be posting questions as they come up. Thanks in advance!


My setup is on another site here. Need to update with the new addition though.

That's a nice looking setup, petew. Welcome to the saloon!

very nice indeed!