Anyone prefer 100hz crossovers?

It sounds as if your L/C/R speakers are distorting when forced to go as low as 80Hz.

My guess is that with the lower crossover, because you're starting to introduce fuller and lower bass with it, what is now being revealed is the insufficient quality of at least one and maybe all of the following;

1) your room and/or your seating position, the latter being if you listen mostly when seated in the same place (standing bass waves building up and creating uneven response in your existing seat, etc.).
2) lack of optimal center speaker and/or other speaker positioning contributing to the too bass-bloated sound.
3) lack of a sufficient enough quality EQ program in your receiver (Audyssey, MCACC, etc., depending upon receiver brand) to help tame and level out some of uneven in-room response.
4) Or, you haven't really used the EQ program in yours yet, as all too often, many users don't really take advantage of their receiver EQ software or give up on it too soon.


You can simply leave the crossover at 100hz and be continue to be happy. But if you have enough time and interest, you can begin the process of exploring how to improve your results with the lower crossover setting (by use of bass and other room treatments, using an EQ program, speaker and seating position adjustments, adding multiple subwoofers to even out the bass within the room {not to add more bass, just even it out}).

I say, just leave it at 100hz and be happy.
Edited by CruelInventions - 11/3/12 at 10:57am

For most practical purposes quoted low frequency extension is only a marketing number since it may not apply to the output levels you're interested in. A speaker that's "flat" to 40Hz may lack the displacement (product of driver size and how far they move in and out) to play comfortably down to 120Hz.

Maximum excursion limited SPL from a monopole operating into free space at 1 meter is

102.4dB + 20log(displacement) + 40 log(f) with displacement in meters cubed and frequency f in Hz.

or

102.4dB + 20log(travel) + 20 log(area) + 40 log(f) with travel in meters an area in meters^2 if you prefer.

Output at the maximum linear excursion into full space for various representative drivers one meter away is as follows at 120, 80, 40, and 20Hz. Subtract 3-6dB getting to your listening position in a typical living and more for a larger space.

You can add 6dB for a floor mounted woofer (as in many 3-ways), 6dB if there are a pair of bass drivers, 10dB for three, and 6dB at the cross-over point to a sub-woofer. A few drivers have more excursion although the things you do to increase excursion (like a longer voice coil) reduce high frequency output (more inductance) and can't be applied freely to mid-bass drivers. Many mid-bass units have less. A port gives you about 1/3 octave of extension where excursion is less but introduces other issues.

Size is the nominal marketing size (cone speakers are usually sold according to their mounting flange dimensions, and manufacturers often embed this in the part number with the Seas W22EX001 being a 22cm driver), Sd effective radiating area of the cone, and xmax about how far it can move one way before the motor looses strength which makes distortion go up.

Size Driver Sd (cm^2) x xmax (mm) 120Hz 80Hz 40Hz 20Hz
4 1/2" Seas W12CY001 50 x 3 89dB 82dB 70dB 58dB
5 1/4" Peerless 830873 88 x 3.5 95dB 88dB 76dB 64dB
6 1/4" Seas L16RN-SL 104 x 6 101dB 94dB 82dB 70dB
7" Seas W18EX001 126 x 5 102dB 95dB 83dB 71dB
8.5" Seas W22EX001 220 x 5 106dB 99dB 87dB 75dB
10" Peerless 830452 352 x 12.5 118dB 111dB 99dB 87dB
12" Peerless 830500 483 x 12.5 121dB 114dB 102dB 90dB

Where a pleasant -10dB from Dolby reference level with dialog at 64dB SPL implies 91-95dB peaks at your listening position and perhaps 97-101dB at the speaker many consumer market 2-ways are likely to have problems with an 80 Hz cross-over.

The same holds for music. Where jazz sounds great at 85dBC average and good recordings have 20dB of dynamic range peaks are hitting 105-108dB a meter from each speaker. Feeding _Take Five_ through 60Hz second order Butterworth IIR low-pass filters I noted right channel low frequency peaks 10dB down from that; although that's still 30 times the acoustic power you can squeeze out of a 6" driver at 40Hz.

My bedroom system used for lower level listening has the Peerless 830873 midrange drivers crossed to stereo sub-woofers at 100Hz for this reason although the -3dB point from their mechanical roll-off is about 60Hz.

The other side of this is amplitude variations and phase shift caused caused by the speaker's low-frequency roll-off.

The low-frequency cut-off isn't a brick-wall. A sealed speaker may be -6dB (1/4 power) at 40 Hz and -3dB (1/2 power) at 60Hz. Where that's close to your cross-over frequency you get an additional dip.

A high-pass response like that caused by a speaker's electrical and mechanical parameters (All speakers have the driver's moving mass and the spring formed by its suspension; conventional speakers add a spring in the form of the air compressed by the driver in the box; and ported speakers have a moving mass of air in the port) implies a phase lead which varies from 90 degrees per pole at very low frequencies to 0 degrees at very high frequencies. A sealed enclosure has two poles (180 to 0 degrees) and vented one four (360 to 0 degrees).

Where the speaker's low frequency cut-off is too close to your electrical cross-over frequency and this isn't taken into account (one octave is the rule of thumb, which is to say a speaker which plays to 40Hz is good for an 80Hz cross-over and one that manages 60Hz just 120 Hz) you get peaks and nulls in the summed response (180 degrees of phase shift from a ported speaker could really hurt - if you reverse the leads on one of your front speakers, stand it beside the other, and feed them bass test tones or music at safe levels you'll notice that the bass is gone compared to a normal wiring configuration).

The THX 80Hz cross-over was specified as a part of a total system standard.

THX speakers were sealed with a two-pole high-pass function -3dB at 80Hz with 90 degrees of phase lead.

They got paired with a matching two-pole electrical high-pass function yielding 4 poles -6dB at 80Hz with 180 degrees of phase lead and the sub-woofer got a low-pass filter with 4 poles -6dB at 80Hz with 180 degrees of phase lag so they're 360 degrees out of phase at all frequencies which is in-phase.

Add them together and they sum flat at all frequencies (disregarding the effects of distance which is compensated for electronically and phase lead from the sub-woofer's inherent high-pass function which is not).

Other permutations of speaker and electrical high-pass functions at 40-80Hz won't work as well.

1. You have speaker interactions with the environment. Low frequency output increases significantly as you near a boundary (6dB or 4X the acoustic power in theory; although in real rooms which leak and absorb sound you get more like 3-5dB and may only have double the bass). A center channel speaker in an entertainment center is going to have a lot more bass than one on a stand and one near the floor or ceiling will have more output than one at ear level behind an acoustically transparent screen.

You also get a dip in output when the low frequencies wrap around the speaker and bounce off the wall behind them and the resulting total delay is about 1/2 a wavelength. With a speaker's front 4' from the wall this occurs at about 70Hz and at just 2' it's 140Hz.

2. Many small (they don't take up a few cubic feet of space. A 30" tall x 15" wide x 12" deep speaker can be only medium sized depending on how low it plays) speakers have a small bass boost which causes your brain to believe lower frequencies they can't reproduce are present (it fills in the fundamental note it's expecting from the harmonics). Where those lower frequencies are actually present because you have a sub-woofer it'll be too much.

Actually that's what the science suggests.

Although people like simple rules of thumb they're not always accurate.

You're balancing lower distortion and flatter response against the risk of localizing the sub-woofer which is more likely with shallower cross-over slopes, mismatched levels, port noises and rattles from bad design, etc. Without those problems and a sub-woofer near the front wall you don't have down-sides through higher frequencies than with one or more of those issues.
Edited by Drew Eckhardt - 11/4/12 at 10:42am

Without actually doing in-room measurements (e.g. REW) or have NIST-traceable calibrated ear drums ;-), you're guessing.

For example there could be some room effect that gives you an unexpected bass boost for say, your center channel. The boost from the room turns your 100 Hz crossover into one that is actually much lower.

Without any info about what your mains are, we're guessing as to what their actual bass dynamic range is like.

You trying to riddle us or what? ;-)

The advantage to a higher crossover frequency is that the higher you set your crossover, the more energy you off load from the mains (a good thing) and the more energy you route to your sub (no harm done, as your sub can generally handle the higher bass frequencies better than the mains).

The trade off is bass imaging which relates to room acoustics, how far you sit from the speakers, and how close the speakers are to each other. If the speakers are close to each other and you, then higher crossover frequencies can cause no audible problems with bass imaging. Of course you said nothing specific about that, either so again your situation is a riddle, not really a proper question.

If your sub is more distant from the mains, and particularly if the sub is off to one side from the viewpoint of your listening location, the more likely there is going to be strangeness to the bass imaging.

The 'inventor' of the 80Hz ( not meaning Tom Holman now, but the guy who wrote the paper Tom read ) has on a number of occasions recommended higher crossover for the center channel, so there's nothing wrong with crossing center at 100 or even 120Hz.
(Orignal paper for Swedish Radio was written for 2.2 stereo system - not for surround. )

That would be my guess as well, that modal interactions with the center channel at 80 Hz were boosting more than when emanating from the sub

My experience has been that you should try to set up your front speakers to go down to around 50 Hz (or just set them for full-range operation), set the subwoofer's filter so that it only goes up to 50 HZ (NO HIGHER!!!), and try to set your center channel to only operate from 120 Hz to 3 Khz; that will give you best clarity. Your center channel should have NO bass coming from it. The best center channel speakers, in my experience, are those with 4-inch drivers; larger ones sound mucky, not crisp and clean.
The Cambridge S50 is exceptionally good, and would be a big improvement to your system.

Your front speakers are designed to go down to 50 hz, and IMO it is idiotic to not let them do so! You want full stereo sound from those main speakers down to 50 Hz. It is also stupid IMO to have MONO sound, from the subwoofer only, above 50 HZ. This makes the system sound poor.

Your subwoofer is not really optimized for anything above 60 Hz, so set it to only go up to 50 HZ; you do not want it to overlap the main speakers. This causes mushiness in the bass due to interference between the sub and main speakers.

I have helped many people who are doing this crap all wrong, and this works every time; greatly improved sound every time. Crossing over those large speakers at a higher frequency is to ignore what they are and how they should be used, and is totally inappropriate. The worst myth ever perpetrated is this 80 Hz crossover crap. Trying to slavishly go by that screws so many people up that is is a real problem. An 80 Hz crossover f is only appropriate for very small 2-way speakers that cannot go much lower.

I would PLUG that rear port on that center speaker, either with a thick piece of foam or a wadded piece of heavy cloth.




Edited by commsysman - 11/22/12 at 10:35am

Pretty much everything in this post is exactly how not to set up a multi-channel system. It goes against accepted standards and will not provide the best immersive surround experience your gear will be capable of. The companies that produce the technologies and features (audyssey, thx among others) all provide set up recommendations that are contrary to what this poster has advised. I implore anyone new to surround sound to take this advice with a grain of salt.

+1 Could hardly get/give worse advice.

It may go against common wisdom usually found in home theatre circles... but he does have a point.

Go to more music orientated forums and you'll hardly ever see anybody talking about or recommending an 80hz crossover. Subs operating at 40hz are more typical there.

I keep trying higher crossovers like 80hz and even up. Sure I can get a flatter response in my room more easily with the higher crossovers, but I very quickly feel underwhelmed with music playback as the soundstage feels less dramatic and more flat. For example the other day I was trying a higher crossover again and was listening to some chamber music with a cello playing deep notes on the left of the stage. With a high crossover (80 and up) the bass notes were more coming from the centre of the stage. With a lower crossover (60 or below) the deeper bass notes were coming from the left of the stage with the cello where it was actually placed. It sounded more real and life like that way as if the cello was physically in the room with me on the left side of the room. For music playback I simply don't like anything higher than 60hz for my crossover otherwise the soundstage becomes less dynamic.

.
Edited by kiwi2 - 11/22/12 at 7:50pm

80hz is a compromise based on a few factors:

1: it is the point where sound is starting to become omni-directional.

2: It is the point where a lot of smaller (surround) speakers begin to drop off dramatically and play poorly.

3: 80-100hz is the limit of a lot of subwoofers capability. Many (not all) subs start to perform poorly when playing above 100hz.

The 80hz "default" I believe is a holdover from the days when a single crossover was used for all your speakers. Even today, some AVR brands only allow a single crossover point and applies it to all speakers. Auddessy based AVR's allow different crossovers for each individual speaker and I think one should take advantage of this feature; crossover your smaller, less bass-capable speakers at 80hz (or higher if necessary, just try to avoid going over 100hz unless you sub can handle it) and cross your mains lower if they can handle the bass. If you feel the dialogue is too "bassy" because of a low crossover point, simply raise the crossover for that single speaker to where you are happy with it. If your AVR allows only one crossover point, you are going to have to compromise and choose the crossover point based on your least capable speaker, or risk having holes in that speakers frequency response where you lose sound before the sub kicks in and takes over.

There's a reason I bought an Auddessy enabled AVR...

Now, the particulat case may be one thing, but in general I'd definitely say you're wrong. The 80Hz choice is based on acoustics/psychoacoustics, so it's not a matter of wasting capacity, it's a matter of not introducing problems.

On the stereo vs. mono issue... just use dual (preferrably four) subwoofers and you can use stereo as well. The filter I'm using has a flipswitch for stereo/mono for checking what works best for the room/material in question. ( It can also join the .1 channel with the front channels for using the same subwoofers for the low range on the fronts and .1-channel )

Might be the case, but not on the forums in Sweden. We have a lot of people with extremely capable stereo setups using 80Hz with multiple subwoofers here. Or rather bass modules as they are not
to go below where the woofers end, but rather replace it's workload for the bass.

Would that more likely be stereo sub arrangements though, with a sub for each speaker with speaker-level input and output... rather than the mono output bass management like with AVRs?

I had recently been steering toward running my mains full range (rated into low 30's, plenty of output in 40's) but after some more measuring and playing around I run them with a 120hz crossover.  A lot will depend on the number of subwoofers you have and how flat you can get your response.  Plot of my bass is here (can read the entire thread if you'd like to see where I started from) 

http://www.avsforum.com/t/1440078/bass-management-vs-full-range-speakers/30#post_22616860

 

For those of you thinking you can locate an 80hz tone, you can try what I did and maybe be enlightened.  I always thought I could too.  I moved both my subs out into the middle of the room and sat just a couple feet from them and played various tones.  Sitting right next to the subsI couldn't tell where the tone was coming from until well into the 100s.  I was shocked!  If you can hear where the sub is coming from more than likely there is a bump in your response giving it away.

Yes, although one sub per speaker is a bit little, two per speaker is better, myself I have 4 NHT 1259 12" per speaker in the livingroom ( green boxes in my avatar pic ). But some people still find running them in mono works better, myself I run stereo.

There's nothing preventing you to use the same setup for home theater and run the fronts full range. I do realize that few filters have the option built in to sum in the .1 channel to the subs, unfortunately.

Or too high distortion so you can locate it by the overtone(s).

Which is also a reason to make sure the cutoff is sharp. 30dB per octave is good. The HP for the fronts can be kept more shallow, say 18dB per octave.

I too can get a nice flat room response if I crossover at 120hz. But there is more to the musical experience than that. Turn off the power to your subs with that 120hz crossover and continue listening to your speakers now. Think about how heavy bass instruments will be placed on that soundstage with in effect small 3" satellite speakers that you have now. How can the full range of a cello be placed to the extreme left? How will your system be able to relay a large set of kettle drums on the extreme right?


It's not about locating or not locating where a sub is placed. Indeed, if you have your subs set up correctly then they should fill the room with even bass. What I am talking about is *not* having localised bass to either the left or right of the stage. Speakers playing low can do that. Mono bass in a room cannot. I can live with 60hz and below being mono... but not higher.

I don't listen to orchestra music so doesn't come into play much for me I guess.  

 

I have been on both sides of this...insisting I can locate the sub and bass...but more measuring and tweaking has revealed the frequencies I thought I could locate I cannot.  

A song with a drum riff that races across from left to right then? Such a track was what first made me notice the stereo effect of a higher or lower crossover. With a low crossover you get a good sense of the drum riff moving from left to right and back again. With a high crossover, it was more of a drum sound from the centre of the soundstage with less left to right panning.



Have you tried turning off the power to your subs and listening to your 120hz crossed over speakers by themselves yet?

How common is that sort of drum riff in music? I'd argue it is also unnatural because I've never seen a drum set move across the stage ;-)

no, I have not turned off the subs.. Not sure what you are getting at with that since what I'm trying to do is integrate them together the best so it doesn't matter what they sound like apart. I could see what it sounds like but that wouldn't change my mind for any reason.

Well what you will hear while doing so is all you are ever going to get for stereo imaging. Everything below that which is being handled by the subs is all going to be mono. It does have an effect on the dynamics of the soundstage. Just everything in audio is always a compromise against something else.

How do you know there is stereo content below that in the source? I agree it is all a world of compromise.

Not sure how valid the source is but at it is a perspective, http://www.soundonsound.com/sos/oct00/articles/stereomix.htm

 

"Once a workable balance has been achieved, you can start to work on the effects being used (try to keep these to a modest level in the early stages) and the basic panning of the different sounds. The most important thing to bear in mind here is that low-frequency sounds work best when panned to the centre. Low-frequencies contain most of the energy within a typical mix, so it is best to share the load of reproducing them equally across both speakers in the end user's hi-fi system -- this means bass guitars, bass synths and kick drums shouldn't be allowed to wander very far from the centre of the soundstage.

 

If you have an artistic reason for putting a heavy bass sound to one side of the stereo spectrum, then it's worth knowing that our ears can't glean much in the way of directional information from low-frequencies. This means that you can get away with using a mastering plug-in or processor to sum all the frequencies below about 120Hz to mono, without disturbing the stereo image -- most bass and drum sounds have ample mid-frequency content which can be panned to produce the illusion of localisation even when all that power-hungry low-frequency energy is bang in the middle of the stereo field."

 

 

and people having a similar discussion, http://www.idmforums.com/showthread.php?t=103069

Edited by primetimeguy - 11/23/12 at 5:12pm

That's mostly because people are used to crappy bass fidelity. Here are measurements of "full range" speakers in rooms in the bass.

Two speakers operating in a domestic living room at positions to optimize midrange spectral balance and imaging cannot have good performance in the bass. The reason is simply that the modes in the upper bass (say, 50-150Hz) are unevenly excited.

With one sub, or with multiple subwoofers? One sub is usually even worse than two full range mains in the upper bass...

Sounds like something else is going on there. With well-integrated multiple subwoofers (see link, supra) the only effect they have on soundstaging is to make the stage more expansive and more palpable. Turn the subs off, and the stage collapses into a shell of its former self. And I'm talking about sub lowpass filters in the 150Hz range, with mains run unfiltered. Obviously, with weaker mains one needs to filter them, but ideally one should use mains stout enough to be run without highpass filtering and with response deep into the modal region.

There's no such thing as "stereo bass" in a small room.

And consider the masking effect of higher frequencies, too!

That said, IME the most common cause of subwoofer localization is localized rattling or buzzing around the subs. With a really powerful system, one would be well advised to invest in quality weatherstripping, little Sorbothane feet behind artwork on the wall, etc. And yes, higher high-pass filters on the sub means more opportunities to make stuff rattle.

It's in your head. Localization cues are well above that region. Though one would be advised to use something stouter than "small 3-inch satelite speakers" for mains if at all possible. With such speakers, you may be getting better performance simply because the mains don't have the output to drive room modes in the upper bass, and the subs fill in below the upper bass.
Edited by DS-21 - 11/27/12 at 8:55am

You mean I won't hear a difference between my right stack of subwoofers playing a 75Hz tone pulses compared to flipping the switch to play it in mono on both stacks? Or pulses alternating left-right or left-center-right might be even more interesting...

I'm quite certain I would, but I have no one around to blindtest me, so I can't check it in a proper way.
Edited by Nightlord - 11/26/12 at 8:41am