Bass Management: A Controversy

[Rob Babcock]

I agree and disagree- if you were one of those rare guys with speakers capable of Dobly Ref levels at 20 hz with your mains, then bass management & subs wouldn't be necessary. But those speakers are as rare as hens eggs. My current speakers have superb bass, but they can't touch my pair of HSU TN1220's for true low-end, high-output sound.

Plus using bass management allows you to use parametric EQ only on the low pass without mucking up the other freqs.

 

[Seth=L]

If speakers do have usefull output to a certain frequency, why not just use the x-over on the sub, so the sub can pick up exactly were the main speakers roll-off? I guess that is more my point, rather than cutting you main speakers off at 100hz.

I am not saying that most main speakers can acheive such low bass, I know that they don't.

 

[MDS]

If speakers do have usefull output to a certain frequency, why not just use the x-over on the sub, so the sub can pick up exactly were the main speakers roll-off? I guess that is more my point, rather than cutting you main speakers off at 100hz.

Regardless of whether you use the xover in the receiver or in the sub itself, if you set it to 100 Hz, you WILL be cutting your main speakers off at roughly 100 Hz (remember the xover is a slope and not a brick wall that cuts off at exactly 100 Hz).

There are many possible ways to utilize the sub's internal xover instead of or in addition to the receiver's xover...

 

[Seth=L]

I also understand that it slopes.

 

[Sleestack]

In my 5.1 setup, I only use the sub for LFE signals and a crossover on my limited range center channel. I go full range on my mains b/c they utilize 2 12" drivers which can handle lower frequencies, however i do rolloff at 30Hz. I don't route any of my main or rear channels to the sub. I'm not sure how it would all sound w/o the room correction applied by the TACT TCS MKII, as that unit allows me to seamlessly integrate the various speakers throuh correction. What I do know is that w/ room correction, running my system with only LFE going to the sub sounds much better than when I use a 80Hz crossover on all speakers. Much more balance. I am able to apply separate corrections to each speaker.

Below is a picture of the uncorrected in-room response and a sample corrections set. You can see the 80Hz crossover on the LFE and the way I rolled off the center channel to utilize the crossover.

 

[JackT]

That was a hypothetical speaker system for starters. And second, why is it always about output. I am discussing accuracy, not loudness. A subwoofer is going to produce louder bass than a speaker system in most cases.

Many subwoofers suffer from audible overhang, slowness of bass. If a drum wack sounds more like a lingering dong on a sub and not on some nice full range speakers, then what is causing that?

A "whack" has appreciable high frequency content, because it is an impulse. No matter where your crossover freq. is, the high frequency components will be reproduced by your mains, and the low frequency components by the sub. "Fast" means having high frequency content, so there is NO SUCH THING as fast bass. If you gate a 20 Hz signal off and on, the power spectrum looks like a sinc function, with high frequency content everywhere. These high frequencies would be above your crossover frequency in any case.

 

[Buckle-meister]

Why does everyone one on these forums insist that you use bass management on your receiver, or pre/pro amplifier combinations even if someone has exeptional speakers...

Whilst it's been mentioned that a sub is used primarily as a more capable speaker than most at reproducing low frequency content, it's worth noting that in terms of room acoustics, freedom of placement is far greater for a sub than for any other speaker and that makes it invaluable in helping tame the negative effect a room has on the sound you hear.

 

[Sleestack]

Whilst it's been mentioned that a sub is used primarily as a more capable speaker than most at reproducing low frequency content, it's worth noting that in terms of room acoustics, a sub comes in very handy in that freedom of placement is far greater for a sub than for any other speaker and that makes it invaluable in helping tame the negative effect a room has on the sound you hear.

Very good points. I do feel that crossing over at 80Hz sends too much information to the sub and ruins the balance I get with my speakers running full range, however, sometimes I use a 50Hz crossover on those channels just to get some of that super low frequency energy directed to the sub. Room correction does wonders for low frequencies.

 

[Buckle-meister]

Room correction does wonders for low frequencies.

So does room treatment.

 

[Sleestack]

So does room treatment.

I use both. Room treatment alone can't achieve what it does with room correction, especially in a multi-channel system.

Uncorrected v. corrected for a 2.2. system in a treated room:

 

[Buckle-meister]

I use both. Room treatment alone can't achieve what room correction does, especially in a multi-channel system.

Swap 'room treatment' for 'room correction' above and your sentence will still be correct (I do agree that neither is a complete solution).

What do the four graphed lines represent?

 

[Sleestack]

Swap 'room treatment' for 'room correction' above and your sentence will still be correct (I do agree that neither is a complete solution).

What do the four graphed lines represent?

Room treatment first is fine by me. Nevertheless, for some people who won't do acoustic treatments room correction is a must. I do both and appreciate the necessity of both.

The 4 lines represent each speaker I use in my 2.2. setup below. 2 mains, 2 cornerload subs (which just can't be used w/o correction)

The 2nd graph show the corrected response after I have applied my correction curve to the first graph. I have more tweaking to do, but that is the product of 10 minutes of work.

 

[mtrycrafts]

That was a hypothetical speaker system for starters.

Oh, now you tell me.

And second, why is it always about output.

Because I'd like to hear the output, not see the cone just move and pretend.

I am discussing accuracy, not loudness.

Useless if it cannot be heard.


Many subwoofers suffer from audible overhang, slowness of bass.

Oh, really? Fast subs are really called tweeters.

If a drum wack sounds more like a lingering dong on a sub and not on some nice full range speakers, then what is causing that?

Who knows. Maybe the recording? Maybe the full range is not reproducing it accurately? Many reasons. Sobs being slow or fast, an oxymoron, is not one of them.

 

[Seth=L]

What I meant about output, louder isn't better. Even responce across the board is desireable.

What makes a subwoofer boomy, other than room placement and source material?

 

[Rock&Roll Ninja]

Why does everyone one on these forums insist that you use bass management on your receiver, or pre/pro amplifier combinations even if someone has exeptional speakers.

because unless your loudspeakers can reproduce high SPL at low frequencies you're both missing bass, and potentially overdriving your mid-woofers.

And most AVRs preset their crossover at 120 or 100 for lowest common denominator. Many AVRs will let you adjust for 80, 60, or even fewer Hz.

But those speakers are as rare as hens eggs.

I think you mean 'hen's teeth'.

 

[Seth=L]

I think if you have speakers that can handle it, say you have anything that Sleestack has, would you guys use a x-over?

 

[gene]

Why does everyone one on these forums insist that you use bass management on your receiver, or pre/pro amplifier combinations even if someone has exeptional speakers. Before I get rolling, I do beleive that bass management does have a purpose in many applications, just not all.

Bass management is essential for many reasons:
1. Almost no speakers can be considered full range - able to play high SPL levels down to 20Hz
2. In order to achieve the best bass response for the entire listening area, properly placed subwoofers need to be use. Full Range speaker placement almost never coincides with optimal placement for subwoofers.
3. Bass management usually extends system dynamic range allowing a dedicated subwoofer channel to be directed towards multiple self powered subwoofers.

I suggest reading the following articles as a reference:
http://www.audioholics.com/news/editorials/SurroundSound.php

http://www.audioholics.com/techtips/setup/loudspeakers/bassmanagementbasics.php

http://www.audioholics.com/techtips/setup/loudspeakers/SubwooferplacementP1.php

Many subwoofers suffer from audible overhang, slowness of bass.

Most of the time this has more to do with improper setup (ie. location, xover point, SPL level matching between sub and mains).

 

[Seth=L]

Alright so what is the problem with setting subwoofer's x-over so it picks up were the mains left off without using the receiver or processors' x-over network? Does this make any audible difference? In case I caused some confusion here, I am sorry. This was my argument. Of coarse setting a sub's x-over to 40 hz when a hypotetical speaker starts rolling off around 60 hz.

 

[Sleestack]

I think if you have speakers that can handle it, say you have anything that Sleestack has, would you guys use a x-over?

Keep in mind that when you look at my target curves, I restrict the output of my Andra IIs below 30Hz, primarily because I setup more for 5.1 audio than video. Also, even with 12" drivers, the Andra IIs can't do what the Velodyne does at 20Hz. that's pretty clear on the graph as well. I have another setting that crosses the front and rear full range speakers at 50hz, which I use for HT. I don't like using an 80Hz crossover on those speakers.

 

[Seth=L]

I mostly listen to music, so that's which side I am really asking about. Thank you for the info though.