Subwoofer LFE
Join Our Community Subscribe to Paul's PostsIf you’re running a home theater receiver or surround sound processor it’s often tricky to get the subwoofer settings correct.
Theater processors are almost always different than analog preamplifiers in the way they handle bass frequencies. Unlike SSPs they almost never have separate subwoofer outputs.
Confusion arises between the two because (typical to) an SSP is a built-in subwoofer crossover. What often happens is users mistakenly plug the crossed over SSP output into the subs crossover-controlled input—and now we have two crossovers where we wanted only one.
Which is why so many subs have what’s called an LFE input (Low Frequency Effects). Basically, the LFE is a direct shot into the subwoofer’s amplifier without going through its crossover. Thus, the crossover in the receiver or SSP controls how high the bass goes and to what degree its roll off should be tailored to.
Here’s a simple rule of thumb. In a two-channel setup, you will always use the subwoofer’s built-in crossover.
In a home theater setting, it can vary: if connecting through the subwoofer’s high-level inputs use the sub’s internal crossover. If connecting the SSP via RCA use the subwoofer’s LFE input.
This is a good argument against using a separate pre-amp or SSR, which I never have.
Until yesterday I had Devialet and Bluesound, both of which have a sub-out connection. They are controlled by settings in the software/app, so you can choose whether or not to have a filter and, if so, the crossover, order etc.
The Bluesound was replaced with a CA CXA81 last night. It has a sub-out, but I used the Speakon connection. What I don’t understand is why the connection differs depending on what class amp you use.
For set-up, REW is invaluable. Each click on the volume and crossover is readily apparent.
Subs now seem very easy to get right. The best advice on set-up by ear was from BK, just place the sub next to the main speaker and send tones at 10hz intervals, starting at 100hz and going down to the lower limit of the sub, and adjust the sub settings until the main and sub sound continuous. You get the volume correct at 100hz and then adjust the crossover.
Best of Luck with the CA CX81! About a year ago, I purchased a CA CXN v2 streamer to replace a Musical Fidelity streamer. I have found the CA CXN to be very easy to use and the fidelity is great.
Also, their support team is excellent. I have the CXN feeding, via a digital output, to a PS Audio Stellar Gain Cell to a PS Audio S300.
If your are using internet radio, I would suggest trying JAZZ GROVE, either the MIX or EAST. Also, WBGO from New Jersey or WDNA from Florida, are excellent. There was a Jazz station from a university in Jerusalem ,until about a year ago, that was excellent. But for some reason they no longer transmit.
Getting back to the subject at hand, I am having difficulty finding info on the best way to connect
a single powered subwoofer to my system. My system does not have a dedicated sub output. However, my amp has dual speaker outputs for both left and right channels, that, I think, was primarily designed for bi-wire. Any suggestions?
Have fun
Larry
Thank you for for the recommendation – listening now.
You probably have the same remote and it indicates that the CXA/CXN/CXC are designed as a fully integrated system.
Cambridge Audio have been around a long time, their top-end Edge system is their 50th Anniversary product range. The CXA is Class A/B and slightly warmer than the Bluesound Class D, but still very agile. The S300 is good value, even in the UK, and is well reviewed even in AudioScienceReview, because the ICEpower unit is basically good and you don’t need to mess with it.
The best part of the deal is that the CXA81 cost just under one third the price of the SGCD/S300 combination at current UK discounted prices and takes up half the space. It has A and B speaker terminals, I have my sub and mains both on A, but could put the sub on B and so have the option to play with (A+B) or without (A only) the sub.
It is sitting on the floor of my office next to my Innuos Zen Mk3 server/Roon Core. In addition to serving 5 Roon end-points (Devialet Phantom and Reactor were software upgraded to Roon Ready and Airplay2 a few days ago), it has a high quality usb output (with a dedicated internal linear power supply) to act as a Roon player. So the CXA81 is directly connected to the Roon server by usb and that’s how I’m listening to Jazz Groove on Roon Radio now!!! This configuration saved me having to buy a dedicated streamer.
Apologies, here is a link for a connection from S300 to REL using the FLE cable to the speaker terminals. https://youtu.be/3F5WTOu60hE
Thanks Larry for the Jazz Stations. Consider KCSM in San Francisco and WPFW in Washington DC. Enjoy
Have you tried Jazz24 out of Seattle? I discovered it when Paul made a plea a few year’s ago to help fund the station. I find it very interesting to listen to, even though I do not consider myself a jazz aficionado at all.
Thanks Larry. I do enjoy all kinds of musical genre but jazz is my favorite. I will check out the jazz24 station.
Thanks also for your contributions on this forum.
taiye
Larry- This is what I’ve done with my single REL Storm III sub for the past twenty years, in my two-channel system. Following REL instructions, the sub is in the corner of the front wall to provide deep LOW BASS pressurization below 40 Hz. The sub is connected to my amplifier speaker cable posts through its hi-level input. I set the crossover to 28Hz, no higher, and it blends smoothly with the speakers. The sub’s low pass filter drops off at 12db/octave, so it’s down 12 db at 56 Hz.
Most people, for convenience I guess, are looking to set-up their subwoofer(s) to a ‘set & forget’ (one size fits all) setting.
This doesn’t work for me as there are many tracks on many CD’s with different levels of bass in the recordings (compilation CDs from the 60’s & 70’s are the worst) that require slight or significant adjustments (crossover/gain)
Some recordings have such strong bass, who here doesn’t know of the Jennifer Warnes CD – ‘The Hunter’, where the bass is just so ridiculously ‘overblown’ that the subwoofers are not even required.
And then there’s the opposite, those “where’s the f#@king bass?” recordings.
While I’m up changing a CD I take the opportunity to make those adjustments on the rear of my subs.
I know by now which tracks don’t even require subs; then the gain is set to zero.
For me it’s all part of the fun of being an audio-enthusiast.
I’ve always preferred to drive a manual (stick) than an automatic.
I thought I had a similar situation with varying need for subwoofer gain until I read a series of articles by Jim Smith in the PS Audio publication. Long story short, if you have to vary the sub gain for different recordings, your subs are not properly set up. They are not meant to be used as tone controls to alter the response of individual recordings. Set up properly, they extend the response of the main speakers in a very holistic manner. Not that having tone controls is necessarily a bad thing; it’s just not what the subs are designed to provide.
jk,
Ideally yes.
However, in my listening room if I have the subs set for the album, ‘A Letter From St.Paul’ – The Silencers & I don’t adjust them down for say ‘The Hunter’ – JW (yes I’m using two extremes here to illustrate) it will overload the listening room with bass & make listening very uncomfortable.
I have set them in & around the listening room in various positions, even stacking one on top of the other, & it doesn’t make a helluva difference.
I guess that that’s the compromise in my situation.
Having said all that, I did originally buy those subs to augment a couple of 5″ two ways however since going back to 3way floorstanders there is now much more bass coming from said floorstanders & so the subs don’t have to do as much work as they did before.
Manual or Auto! Manual is fun, but if you live in an area like I do, manual would be a headache.
Driving in Miami makes the Indy 500 look like kindergarten! Driving in Miami is more difficult than
trying to find some agreement as to how to set up a set of speakers and a sub woofer!
I just spent the better part of a day “playing ” with speaker positions. Fortunately, I found a spot that sounds terrific- great bass, great mid range and not too bright sounding. After all was said and done, I listened for several hours with zero fatigue!
Larry
Larry,
“zero fatigue” is the place to be 😉
I know Paul has spoken many times about his preference for using speaker level inputs for his subs. I have tried it that way in the past and actually feel from my experience it is a tad better than the LFE inputs. However, to reduce further clutter, with multiple sets of speaker wires all around, I switched back to the LFE outs on my kit to the subs (I use dual subs). It’s good enough so I won’t sweat the minuscule differences.
I forget exactly the process but I recall that I had to turn the crossover knob on my sub totally one way or the other to disable it, then the digital room correction on my receiver plays a series of tones and sets the crossover frequency to send to the sub. I’m afraid I fall into the “set and forget crowd” that Fat Rat talks about, I want to do it once and then for the most part just forget about it.
Thanks for this post, Paul. I have a pair of subs and some new Magnepan speakers I was trying to mate them with. I use an external crossover. Last weekend, while trying to fine tune the crossover now that the Maggies have broken in, I noticed that the left and right subs didn’t sound the same: one was louder and went higher up in frequency than the other even though I had turned the crossover point of both subs all the way up (160Hz), thinking that would essentially move the internal crossover out of the way.
Your post prompted me to check which inputs I was using on the subs. The subs are placed in such a way that I can’t see the inputs very well. As it turns out, I had (more or less by rote, without being able to look at the markings closely) plugged the left channel from my crossover into the left input on the left sub, and the right channel into the right input on the right sub. What could go wrong? Looking more closely this morning, I see the right input on the subs is marked “(LFE)”. So one sub had a “double crossover” and the other sub was using the straight shot into the sub’s internal amp. You solved a mystery and helped get the subs working correctly.
When I was looking for a small, used sub, I finally gave up on finding one with high level inputs. Many many…including the vaunted RELs…have none. I finally got a 10 inch ML, which works great with my Maggies.
I set up my subwoofers once and never touched them again. Well, a few times for very tiny adjustments.
And yes, jimkannry, you are totally right.
Too much bass sometimes? Then there is probably something “wrong” with the recording. You can’t fix that, it is what it is.
Too much bass all the time ? Then there is probably something “wrong” with the acoustics and/or setup (including placement) of the sub(s).
You can fix that.
In the past I connected my subs to the speakerterminals of my amp.
Nowadays I have connected my subs to the speakerterminals of my main speakers.
Right sub to the right speaker, left sub to the left speaker. Sounds great.
BTW., “The Hunter” (J. Warnes) too much (overblown) bass ? No way. I don’t have the album myself but heard it on several occasions at several dealers on several amps/speakers.
The bass never sounded overblown. Mainly the opening track has a distinct (electric) bass, but not overblown.
You wanna now what real fat (maybe a bit overblown) bass is ? Then listen to “Little big” by Aaron Parks.
Compared to that the bassnotes on “The Hunter” are child’s play and very innocent.
jb4,
“…no way. I don’t have the album myself….”
Hilarious!
I do have the album; I’ve had it for 28 years & I’ve played it on different amps & loudspeakers & yes, the bass in the recording, compared to most music that I have in my CD collection, is overblown 😉
Yes, no way.
But as so often you don’t read my post or only 25% or so.
I heard the album at least 5 times….on very, very good systems.
Way way better than what you have (according to what you wrote about this).
Anyway…. I’m not gonna repeat my previous post.
Just READ it, and this time do not stop reading when you read the word “myself”. There is more, just READ it !
And compared to most music you have…Yes that may be true. I have this audio buddie who, just like you, is stuck in the past when it comes to music.
And I told him that there is hardly any (deep) bass on his Zappa and Lou Reed records.
That’s the case with most 60’s, 70’s and a lot of 80’s records.
And you now what ? He said I was right about that now that he listened carefully.
So, “the bass in the recording, compared to most music that I have in my CD collection, is overblown”….
That I believe !!
But if you listen to more modern music (1990-2021) than you learn what REAL fat (sometimes overblown) bass is.
Good example is hiphop. Now that is overblown !
And, to a lesser extend, the example I mentioned.
I know every song on The Hunter. The bass is nothing special.
As I wrote yesterday, only track 1 has a distinct electric guitar bass. Not overblown. The rest of the album are harmless in this respect.
jb4,
Subjective opinion strikes again.
Errr…I’m not the only one who has commented on how overblown ‘the bass’ is on ‘The Hunter’ in the last 28 years…just sayin’ 😉
jb4,
It’s been a busy day & now that I have the time to banter with you further, I will do so.
I didn’t stop reading your post when I got to “myself” otherwise I wouldn’t have done the four dots “….” afterwards to signify that the quote continues but that I’m not going to waste my time typing it all out.
I always read ALL of your posts, not just 25% or so, because I find them entertaining (I already told you that, at least twice)
It seems that if I don’t agree with you you like to pull out the, ‘you don’t read all of my post’ excuse…sorry I’m not buying that.
You type, “I have this audio buddie who, just like you, is stuck in the past when it comes to music”
Wow, that’s a big call for anyone who likes any classical music or blues or jazz or Rock ‘n Roll that was written or performed before 1980!
I’m happy to know that I’m in very good company. 😉
“If you’re running a home theater receiver or surround sound processor it’s often tricky to get the subwoofer settings correct.”
What does correct mean in this context?
The rest of this posting is about how to connect a subwoofer to an HT receiver. Some HT receivers have more jacks on the back panel than an old style telephone switchboard. I like the ones that have separate input jacks for each channel. It would be good to have tape monitor in and out jacks for each channel or at least pre out power amp in with jumpers to enable the use of external processors and equalizers.
So for 2 channel listening the passive xovers in subs are recommended above the digital xover in preamp.? Ok. Rules are meant to be verified and sometimes broken. “But mama, Thats were the fun is”
If I haven’t listened to ten utube gurus on this subject,I’d be surprised. Including at least one from Paul. This is the first time anyone one said that in a clear way. Experimenting i figured out the knob on the sub did nothing. Possibly,now i know why. What I’d like is for the subs to turn on at low volumes.
The Crown icore 2 series amplifiers have built in programmable crossovers you can use for bi-amping. These amplifiers are so inexpensive that you can easily afford two. They run from about $330 each to $665 each. They offer immensely powerful class D amplification, are super reliable, and according to the reviews I’ve read on YouTube they are difficult to find fault with. Whether or not they were the reviewer’s absolute favorite nobody didn’t admit they are an incredible bargain at those prices. I keep in mind that if the reviewers said they were giant killers the giants wouldn’t be sending them any more free equipment to review. If you don’t like their FR you can easily change it with an equalizer. They are stable down to two ohms. They have been adapted from the previous versions to be friendly for home hi fi use as well as professional use.
If you are using a 2 channel preamp that does handle high and low pass crossovers internally (NAD M12), wouldn’t it be better to use it instead of the subwoofers crossover?