Why the fuss with subwoofer specs and brands?

[bodhi]

And, to your point, I think most of us (certainly me until last week), have no conception of how much extra SPL bass requires.

Have you tried this test:

The Subwoofer Kick Drum Test

Give your subwoofer a kick (or two... or six).

www.audiocheck.net

If I understand correctly then if all those test tunes play at same level with the chosen volume then you have enough SPL available.

 

[krabapple]

I've been doing a lot of learning since discovering ASR recently. When it comes to subwoofers, I find a lot less data (at ASR and in general), and more of brand-loyalty or brand-shaming than for other areas at ASR. Even in the subwoofer comparison thread by sweetchaos, the frequency response data is sparse. A lot of the models listed don’t have any frequency measurements.

Learning more, in any case: in mid-sized or smaller rooms, for low frequencies, the response is heavily influenced by the room, and clued in people like ASR readers are probably going to apply some EQ, either rolling their own or with Audissey/Dirac etc. Some will do multi-Sub to tame room modes with physics.

There was also a presentation by Floyd Toole shared by NTK on “Getting the bass right”.
A few jewels from that:

• corner placement for subwoofers is highly recommended, and gives the signal a 6dB boost, to, em, boot

Actually he calls the corner placement a *logical starting place*. An unequalized sub in a corner 'can work very well' , he writes, but also that it might not. If not, try somewhere else. Toole said he has an uneq'd corner sub setup in his office/den. He most certainly doesn't in his main listening room, where he uses highly sophisticated software bass control of multiple subs.

I recommend corner to my friends who wade into subs but have no clue about room EQ software.

 

[krabapple]

Your vintage sealed cabs roll off at 100hz or higher. The classic Ampeg fridge variants roll off anywhere from 55 to 80hz. Ported cabs go lower but frequently get farty until you turn the lows down. Then you have built in high-pass in the amp (preamp) which in old amps is usually fixed, in modern amps may be adjustable; A Mesa Subway adjusts from 30-125hz, for instance. Rarely do you get below 35hz - the old SWR amps that advertised to go down near to DC were notorious cab killers. The common Broughton high-pass filter pedal adjusts from 25-190hz or so, and center default is 80 hz. I have an fdeck pedal that adjusts from 35-140hz.

Keep in mind these HPFs are all cumulative, and live the FOH is dialing your lows out anyway if you don't beat them to it, because it's uncontrollable rumble.

People think bass cabs go low because they have big drivers (or they try to use sub drivers in a bass cab, with terrible results) but that's almost always for SPL and efficiency, not low extension. A bass cab built for sub frequencies would be as big and heavy as an actual (PA) subwoofer and no one wants to drag that thing in and out of a van. "Shouldn't my cab be able to reproduce the low E" is like the number 1 misconception for newer bass players and it's only worse for 5-string / BEAD types.

For more see for instance https://www.talkbass.com/threads/high-pass-filter-hpf-and-low-pass-filter-lpf-mega-thread.1333720/

Yes, but many do record bass direct. No cabinets involved. There is no rolloff except what's inherent in the bass pickup and the downstream electronics. An open low E has a fundamental of 41 Hz. 5 string basses of course go even lower.

 

[Vacceo]

Have you guys listened to the Petlisten subwoofers? Are they as impressive as reviewers tell?

 

[Sancus]

I'd like to go back to this great answer (I've only quoted a fragment). I still have not done the compression tests you suggest on my system.
I've been able to do the sub integration today, with smooth response 20hz - 20khz at 80db with a slight downward tilt.

But, I was wondering: given what you mention, which is basically the non-uniformity of human hearing relative to frequency.
Wouldn't it make sense if, say, REW had a "follow Fletcher-Munson levels" mode?
Testing at 100dB over the whole audio band would be bad.
And, to your point, I think most of us (certainly me until last week), have no conception of how much extra SPL bass requires.
Would it not make sense to do frequency response curves with uniform perceptual loudness levels?
Perhaps this already exists? If so, how is it called?

You can restrict the bandwidth of a sweep, you can see mine only went to 200hz. DO NOT sweep tweeters above 100dB, that's a great way to kill them(and your hearing).

There is a psychoacoustic smoothing setting in REW but there's no way to adjust measured SPLs to their perceptual loudness I don't think. Would be a fun feature. I always just refer to https://chart-studio.plotly.com/~mrlyule/16.embed

 

[krabapple]

What has that got to do with the price of cheese?

The only point I am trying to make is that I do not see any reason to ascribe any special requirements to movies with regard subwoofer capability compared to music in a domestic setting.

Maybe this helps? :

The LFE channel (which is distinct from 'subwoofer output' and 'bass management') is a dedicated channel with more headroom, specifically for loud, low, often transient movie soundtrack effects. That's just plain history.

For movies, an LFE is certainly useful and requires a subwoofer to play back its contents properly.

For music recordings, an LFE channel is pretty much *not needed* . Cannon fire and other high-level explosive low bass events are rare in music. Typically all the bass in music can be happily contained within left, right, center, and surround channels. All that's required at the playback end is either (truly) full range speakers, or speakers + subwoofer(s) + bass management. So, 5.0 would suffice just fine for a surround music release. But the industry assumed consumers would balk at that missing .1. So they pointlessly add an LFE channel to surround music releases, and populate it unnecessarily with bass.

 

[Chrispy]

But for a few of us, we have been discussing the input on a subwoofer labeled "LFE".

Including the recent digression where @sarumbear is providing some very helpful insight from the perspective of the *source media*, this thread has cleared up a significant confusion that I have had about when to use a subwoofers "LFE" vs "Main R & L" inputs. Originally, I had assumed that the subwoofer's LFE input should ONLY be feed the LFE output from the source.

What I have learned -- from the view of the subwoofer connection called "LFE":

• If the AVR (or 2.1 stereo amp) is not doing any bass management, then the AVR's subwoofer out will only send the LFE channel from the source media. In this case, in addition to the subwoofer interconnect, you need to also need to connect the Right & Left channels (either speaker-level or mains-level) to the subwoofer if you want it to also provide low-end bass for the speaker channels in the source media.

• If the AVR (or 2.1 stereo amp) is doing bass management, then the AVR's subwoofer out will include both the LFE channel from the media source as well as the low-bass from the speaker channels in the source media. In this case, you only need to connect the AVR's subwoofer out to the the "LFE" connection on the subwoofer. Which means the "LFE" jack on the subwoofer is incorrectly (and confusingly) named because it is actually receiving both the LFE channel and the lower-bass range for the speaker channels ("right & left") in the media source.

What I also learned is that it is always important to be clear which part of the audio chain your answer relates to. The term "LFE" actually means very different things if you are talking about the LFE channel in the media source or the LFE input jack on the subwoofer.

Some thoughts on what subs have labeled LFE input....sometimes that specific input will bypass the sub's LPF automatically, for doing bass management elsewhere (some you still need to manually set it to max so as not to interfere with your incoming lpf). Sometimes it's just mislabeled and is only differentiating a single input vs the stereo inputs (if you don't have another way to sum signal to mono). Then again a lot of subs have mislabeled "crossover" as it is only a LPF. Sometimes in discussion of subs the term LFE is misused too.

 

[krabapple]

The Crawl is crude, but done properly can be very effective.
In order for it to work, you have to disable all Speakers excepting the Subwoofer. Then, you must get down on your hands and knees so you can listen where the Woofer itself will be.
For me, when I first did it, it took me about an hour to figure out what I was listening for. But once I did it was pretty eye opening. What made it all click for me was moving in and out of a corner and hearing how the quality of the Bass changed (from clean and precise to boomy and muddy). Once I caught on to that I was able to do the whole room pretty quickly, even finding a spot I was planning on putting a sub which was in a complete null.

Just curious, before your crawls, do you elevate the sub so it is literally where your head would be at your main listening position?

 

[jsilvela]

Have you tried this test:

The Subwoofer Kick Drum Test

Give your subwoofer a kick (or two... or six).

www.audiocheck.net

If I understand correctly then if all those test tunes play at same level with the chosen volume then you have enough SPL available.

I'll have a try, thanks!

 

[Chrispy]

Just curious, before your crawls, do you elevate the sub so it is literally where your head would be at your main listening position?

You put it in your chair/seat to get close

ps with the larger subs this gets difficult

 

[ryanosaur]

Just curious, before your crawls, do you elevate the sub so it is literally where your head would be at your main listening position?

This is an interesting one. I've seen people say it's important while others have said it's not.
Now of course... the one thing in common is that everybody is listening in the "place" where the woofer will be!

For myself, no. I did not elevate the Subwoofer. At 100#, I was not about to try lifting it by myself to get it into position where my ears are at roughly 49" high. Mine are also downfiring, so then that presents another question of whether it should be "aimed" elsewhere...

In the end, only using my XT-32 Audyssey App to focus on the "Before" sweep, I did pretty well just using the Crawl and my ears to find 2 places on opposite side walls. Each sub is placed asymmetrically in the room.

Considering that result, I am in the camp that states placing the Sub in an elevated position at the LP is not necessary. Likewise, getting your ear in exactly the same spot as the woofer is also a bit of an exaggeration whereas getting within about a foot or two is what will make the most sense. And lastly, anybody truly chasing a "textbook" FR sweep will still need to confirm placement of each Sub...

...To this, it becomes what I call the "poor man's" Geddes technique for placing Subs. When I move to refinish my room, I will go to the next level of taking measurements to confirm additive results and will not rely on simply reading the "before" sweep from Audyssey.
But in the meantime, I have been well served by this.

YMMV
(Though I maintain that the best results will come from being completely open-minded and not insisting on placing the Subs where it is simply most convenient/conventionally accepted.)

 

[bluefuzz]

That's just plain history.

Thanks. I understand perfectly well what the LFE channel is and why it is there even though I personally have little interest in or use for it. The point I am apparently failing to get across is that regardless of how the bass frequencies get into a subwoofer – LFE channel, downmixed multichannel, stereo music, mono, whatever – for a given SPL requirement and room, from say ~20 Hz to ~100 Hz, the actual physical requirements of the subwoofer(s) is surely the same for music as for movies. Bass is bass wherever it 'comes from'. I wouldn't have thought this was a particularly controversial or difficult point ... ;-)

 

[Digital_Thor]

Have you tried this test:

The Subwoofer Kick Drum Test

Give your subwoofer a kick (or two... or six).

www.audiocheck.net

If I understand correctly then if all those test tunes play at same level with the chosen volume then you have enough SPL available.

Very nice test Luckily it sounds exactly like described

 

[ex audiophile]

I had the same experience when I tried it, that the crawl process didn't really correlate well after the sub was placed. On top of that, once I got a simple understanding of acoustics, the sub crawl sounded like "go find where your sub activates the loudest room mode for your seating position, and put it there," and that doesn't sound like the greatest criteria to choose your sub placement to me. Maybe it's because I have a simple understanding of acoustics, or maybe it's because I didn't do it right, or maybe the sub crawl isn't a great idea. I've always thought it was the latter. If nothing else it might help you get the most out of an under sized sub.

As for finding best sub locations, I put them where I'd like them to be first (practically, visually, and what I think might work), and then I take measures with REW. From there I start trying other acceptable sub locations in the room, take more measurements, and compare them to my "preferred" spot(s). Rinse and repeat. In the end I decide based on weighing measurements against practicality combined.

I do much the same, using the Anthem ARC Quick Measure function to see what the sub is doing in a particular location. With the sub on sliders you can move it around while the Quick measure is making sweeps. Fascinating stuff and makes a lot more sense to me than the crawl method. Besides, putting a 100+ pound subwoofer onto your couch is not something I can or want to do anymore! Best wishes for 2023.

 

[Chrispy]

Thanks. I understand perfectly well what the LFE channel is and why it is there even though I personally have little interest in or use for it. The point I am apparently failing to get across is that regardless of how the bass frequencies get into a subwoofer – LFE channel, downmixed multichannel, stereo music, mono, whatever – for a given SPL requirement and room, from say ~20 Hz to ~100 Hz, the actual physical requirements of the subwoofer(s) is surely the same for music as for movies. Bass is bass wherever it 'comes from'. I wouldn't have thought this was a particularly controversial or difficult point ... ;-)

When I hear follk going back and forth about capability for movies vs music I just figure they're of the music camp that doesn't care to spend for the deeper extension subs as they "don't need it". We need different things. Personally I want my subs to be as capable as possible for whatever I wish to play....as I use subs for both.

 

[krabapple]

This is an interesting one. I've seen people say it's important while others have said it's not.
Now of course... the one thing in common is that everybody is listening in the "place" where the woofer will be!

For myself, no. I did not elevate the Subwoofer. At 100#, I was not about to try lifting it by myself to get it into position where my ears are at roughly 49" high. Mine are also downfiring, so then that presents another question of whether it should be "aimed" elsewhere...

In the end, only using my XT-32 Audyssey App to focus on the "Before" sweep, I did pretty well just using the Crawl and my ears to find 2 places on opposite side walls. Each sub is placed asymmetrically in the room.

So, to be clear, you turn off all your speakers, put your sub on the floor at your MLP. Play some bassy content while you crawl until you find a nice sounding spot. Then put the sub there. Then put an Audyssey mic at the MLP (ear height), run Audyssey, and examine the 'before' measurement when it's done? (Is Audyssey OK with only having the sub on, no other channels?)

Then rinse and repeat all that as needed to find the best 'before' measurement?

Ah, I do love this hobby.

 

[Chrispy]

Have you guys listened to the Petlisten subwoofers? Are they as impressive as reviewers tell?

LOL would love to demo one....but in home and am not likely to travel to anywhere that has one (let alone properly setup). Don't want to spend that much on a sub, tho, altho these look to be quite excellent.

 

[sarumbear]

So, 5.0 would suffice just fine for a surround music release. But the industry assumed consumers would balk at that missing .1. So they pointlessly add an LFE channel to surround music releases, and populate it unnecessarily with bass.

Hence the need of the separate LFE channel even on (multichannel) music.

 

[Prana Ferox]

Yes, but many do record bass direct. No cabinets involved. There is no rolloff except what's inherent in the bass pickup and the downstream electronics. An open low E has a fundamental of 41 Hz. 5 string basses of course go even lower.

Even with a bare instrument into a DI box you have the FR of the pickups themselves - any device that depends on a conductor moving through a magnetic field needs AC input (literally, movement) and will have low frequency rolloff. Popular transformer-coupled DI boxes also have a low frequency rolloff - again, DC doesn't go through a magnetically coupled coil.

That was what I meant when I talked about bass player misconceptions. A rational person thinks "Low E is 41hz, if I pluck a low E, I will get a 41hz sine wave." You very much don't, what you get is a lot of 2nd harmonic with a spray of higher harmonics changing as the note decays. The human ear and mind are very good at taking those harmonics and perceiving the mostly missing fundamental, distinguishing the low E from higher notes with different harmonic patterns. This is also the basis of certain 'bass boosts' that increase the harmonics while sometimes reducing the fundamental, for ex Peavey's KOSMOS Psycho mode, IIRC there are some AVRs that do this as part of 'night mode' or similar.

For instance, compare a 41hz test tone here with the low E sound here - you can tell there's a lot of higher frequency tonal content and it is likely difficult to impossible to hear any of the fundamental. If you listen to an acoustic double bass it will have more of the fundamental relative to the harmonics - this is part of the reason DB is difficult to record and amplify (and thus part of the reason we have electric bass guitars in the first place.) I haven't tried this but if you have something like GarageBand you can probably simulate a BG low E and see the waveform output as well.

Now we need someone to come in and explain the science of the kick drum impulse.

 

[krabapple]

Hence the need of the separate LFE channel even on (multichannel) music.

Or not. I have silenced/deleted the LFE on some surround music releases with no deleterious effect to my enjoyment. There is plenty of bass in the main channels to be routed to the sub.

[edit: I've done this to some Center channels too. Typically I'm talking about old quad releases that were 'repurposed' for releases a 5.1 without actually going back to the multis for a remix]