Anyone prefer 100hz crossovers? - Page 3

I don't see a heck of a lot of difference between the two curves , and I'm not sure which would be preferable.

Which of course is intended, as the bass modules are supposed to integrate seamlessly. If you don't play material with a lot of low frequency contents, you'd probably prefer not to run with the bass modules, but if you are looking at extending the range as far as possible then lower curve is quite a bit better. The lift extends outside the graph too as my filter has a plug-in card that compensates the roll-off to extend the range of closed boxes well into the infrasonics.

Given that there is a bench for the electronics with a large ol' CRT inbetween the speakers, the floor is uncovered oak, there's one doorway to the library and two big openings leading to kitchen and hallway/stairwell... I don't expect to be able to do any better.

Now, the cinema project... if that does not measure quite a lot better when done, I will be most disappointed.

Could be the case.

Depends on lots of things. While it is generally an audiophile myth that running power amps less hard (but never clipping) makes them sound better, speakers are generally nonlinear enough that offloading them, particularly offloading low bass does indeed have the potential to make audible reductions in nonlinear distortion.

There is another influence that affects even perfectly clean main speakers. The positioning of our main speakers needs to be strongly influenced by soundstaging in the upper bass, midrange and treble. That is likely to compromise their performance in the mid bass and lower bass. Since the subwoofer need only handle bass, we can position it to optimize bass without necessarily compromising the upper bass, midrange and treble.

Totally agree with you there, Arnold!

I've seen a few cases where people with very capable subs have gone up to both 100 and 120Hz to reduce the demands on the top speakers due to listening to music that puts a lot of effect just above the normal 80Hz crossover.

If I remember correctly, Tremtemöller - "Vamp" was one of the tracks these guys used to torment poor speaker systems at loud levels.
Here's an analysis of the track:

Toole seems to indicate that you can not optimize bass with a single subwoofer (location), so you really have to define what bass frequencies you are talking about to make that statement accurate.

In my room, bass below 50 Hz can be driver by a single subwoofer location. Above 50 Hz (AKA mid bass) is a different story!

Do you (or however does the mixing) mix the bass as mono? If so, below 50hz, 100, 150..?

These recordings involve no electrical mixing of the channels in any way.

However, Mother Nature has some ideas of her own! For acoustical reasons there is probably pretty darn close to zero separation at low frequencies,

I know about and agree with this paper:

http://www.aes.org/e-lib/download.cfm?ID=13680&name=harman

"Low-Frequency Optimization Using Multiple Subwoofers*

I've long suspected that to be true in most setups, but have never explored it myself. If I had less sunk costs in expensive bass drivers, I probably would, because one can optimize both the footprint and cost of one's system pretty well that way. For the modal region (in your room, apparently from around 50Hz) one could use relatively small but efficient modules with a fairly high cutoff, and in the first mode region (below 50Hz in your room) one could use any old cheap bass pump with a big cone and long overhung voice-coil in a closed box or 4th order bandpass (or vented/6th order BP/"tapped horn" if one wanted greater efficiency above cutoff, and tuned the system to one's desired LF corner).

Most records with a lot of difficult bass information was never recorded per se, rather computer/synthesizer generated. The people behind the controls do not always follow the example set by mother nature.

Sure, but there are limitations to that paper. In particular, assumption 3 assumes that you are going to waste resources with multiple subwoofers being placed at inefficient (for SPL) locations.

"Some limiting assumptions are made:

1) More than one seat is to be optimized.

2) It is assumed that the system in question will be
equalized.

3) Maximizing the output of the system is considered a
secondary goal."


In addition, this was noted in the paper:

"The question must be asked: Is it preferable to maintain multichannel presentation at the cost of location dependent frequency response variations resulting from unoptimized bass? Which is more objectionable and to what degree? To the authors’ knowledge, this has not been directly addressed by published research."


I find that It is possible to maintain a multi-channel presentation if you crossover at lower frequencies along with using bass management of one kind or another. I use bass management, but not all of my speakers are set to small. That paper notes a comparison of bass management with all large speaker settings against all small speaker settings.
Edited by J_Palmer_Cass - 11/28/12 at 3:00pm

Geddes uses a 50 Hz on down main subwoofer in his setup along with setting his mains to large. However as I see it all of his bass routing schemes still leave a lot to be desired.

HSU uses a 50 Hz on down subwoofer along with the HSU MBM setup. There are multiple ways to place the MBM)s), but the main subwoofer placement recommendations are pretty clear.




The only thing that I will note is that the main speakers need to be bass capable. I am pretty sure that most smaller 2 way speakers will not pass muster for a lower crossover frequency.

All the subs (and mains) contribute at ULF.

I've yet to hear anything else that sounds more like music and less like the can it came in. Nor anything that produces similar (let alone better) results in actual use.

True. Applies to most larger 2-way speakers, too. I wouldn't do it with anything smaller than a 10" concentric driver.

Geddes is now talking about using decorrelation filters in lieu of his trademark multisub approach. More than one sub would still be required but location becomes less critical making it much more user friendly. It would be very interesting to see how it plays out.

Yes.

Typical 2-way mid-bass drivers lack the displacement for acoustic music at less than live but subjectively realistic levels and have audible signs of distress when you try.

I commented on that previously in this thread http://www.avsforum.com/t/1437182/anyone-prefer-100hz-crossovers#post_22553780

Geddes uses bandpass subwoofers, so how much ULF bass (AKA sub 20 Hz bass) that is contributed by those speakers is an unknown.

I run my R & L mains as large, so I know that there are benefits to that scheme.




That is a subjective opinion. How do movies sound?

Still, that does not address how Geddes routes his bass as noted in your link





That's fine if you want speakers that are on the large size.

My R & L main and surround speakers are on the narrow side.

+1 or whatever number you deem appropriate, Drew! ;-)

Keep up the good work. I'll try to do my part.

For now people should look at:

http://www.data-bass.com/drivers

http://www.thielesmall.com/database.asp#

A really good 18" subwoofer driver has 30+ mm Xmax and SD = 1210 square cm diaphragm area. SOTA drivers has nearly twice this Xmax.

A really good 5 1/2 2-way "woofer" has 8 mm Xmax and SD = 115 square cm diaphragm area. This is about the current SOTA

A minimum of 40+ times the displacement!

NHT 2.3 ?

That's one of the few models from that period I haven't managed to get a listen to...

What do you combine them with?

You caught me. Those are pictures the NHT 2.3 speaker. I have the NHT 2.1 that looks near identical to the NHT 2.3 speaker.

What do you mean when you say "What do you combine them with"? For the low end I use corner located NHT subwoofers. For the center I use the NHT 1.1C speaker.

EDIT: My memory was bad. Those picture are the NHT 2.1 speaker that I own.

The NHT 2.3a reverses the tweeter and mid-woofer locations.



Edited by J_Palmer_Cass - 11/30/12 at 1:13pm

Good question.

I have a pair of 2.5i, and the midrange driver runs out of linear excursion trying to keep up with its little sub. Audible IM - sounds like the vocalist has a throat full of phlegm.

The 2.5i was a downgrade in sound quality from the 2.3 based on what I have read.

I also have a pair of NHT 2.9's as well as a full Evolution system (new and unused) that I bought when NHT was dumping their product prior to the sale of the company. I need to finish off my multi purpose room one of these days so I can setup that system.

Ah. Sorry!

ok!

I used to have 7 x SuperZero in the tv-room together with a SW2P subwoofer. And I have the NHT 1259 woofer in my stereosetup, which they used in the 3.3 and the SW3P subwoofer. So, NHT is definitely in the top range of what I like - preferrably the once from the early Kan Kantor era.

I still have a pair of SuperZero's lying around. I used them for the surround speakers for years. The NHT 2.1 was an update from the early Kantor NHT 1.8 speaker. Same update of the tweeter that changed the Zero to a Super Zero.

I bought a second pair of NHT 2.1's on Ebay cheap for use as surround speakers, so the SuperZero's are back in the box.

From what I've read and discussed with Dr. Geddes, nothing's changed except the filters.

Placement is less critical when one has more subs. That's one reason I'm using 5 rather than 3 right now, and will be using 5 (in a slightly different configuration) when my the new mains cabinets I've commissioned are done (hopefully by the end of the year).

No it's not. One can easily model his subs. They use commonly available drivers (B&C 12TBX100), and one can make reasonable inferences as to their relative cabinet volume and tuning based on their external dimensions.

Also, 4th order BP contribute below cutoff, because they're still monopoles (backwave trapped). My understanding, furthermore, is that he's talked about a separate ULF sub, but never actually implemented it. Just the three B&C 12TBX100 based subs. But Perhaps I'm wrong about that.

But I believe Dr. Geddes' answer as to sub-20Hz bass is the same as mine: don't care. Besides, placement can't materially effect anything down there. It's just volume displacement and EQ.

Don't know, and don't care. Movie sound is entirely irrelevant to me, as long as dialogue is audible at low volumes.

Besides, if some special effects dude's idea of what a bomb blast sounds like is 2dB quiet or 3dB hot, who cares?

It works fine on concert videos (Radiohead TKOL Live from the Basement, Adele at Royal Albert Hall, Zeppelin at the O2 Arena 2007, etc.) though.

I don't understand what you mean by that.

Yes, if one wants a 2-way it has to be "on the large side," because otherwise it won't be capable of the required output. A reasonable reading of my earlier post would appropriately limit the scope of my comments to 2-way speakers. Multiway speakers allow different form-factors (assuming narrow directivity isn't a goal; width is the only way to get that).

The NHT speakers you showed were 3-ways, not 2-ways.

Likewise, I needed narrower speakers for aesthetic reasons, so my old 12" concentrics in 17" wide cabinets had to go. To get similar volume displacement (but even so, markedly lower efficiency, down from ~96dB/W/m to likely 87dB/W/m if I'm lucky) I had to move to a 3-way design: 5.5" concentric driver flanked by two 7" midwoofers. (Though it could be considered a 4-way design, given that the mains will sit on "stands" containing side-bottom-back firing 12-inch "flanking sub," a la NHT 3.3 and others. But that's separately powered from the tops)
Edited by DS-21 - 11/29/12 at 8:48am

Did you follow this discussion?

Yes.

"I would say that this filter would seriously minimize the importance of placement, but I do think that placement would always have some effect. I would say that the decorrelation filter would be a 'compliment' to multiple subs" is not materially different from what I wrote above.

And it's also worth noting that, to my knowledge, most of that talk is still theory, not practice. Perhaps Arny or another SWMTWMS member/person who lives near Dr. Geddes knows more about that, though.

Geddes clearly hopes that decorrelation filters would minimize the number of subwoofers and the importance of placement.
If he is successful, you would be able to get by with just 2, perhaps 3, subwoofers and the placement will be dictated by convenience rather than necessity. That's how I understand him.

I have no idea how far he is in the development. it did sound a little bit like thinking out-loud.

Bandwidth is 45 to 120 Hz per Geddes

http://www.gedlee.com/Subs.htm

Note that ULF bass on AVS is defined as bass below 20 Hz.

As I recall, Geddes did use a dedicated subwoofer that covered down to the 20 Hz area.





If you don't know and care about how movies sound, then you don't care about defects in Geddes bass routing schemes.

I tend to stay clear of discussions where the primary use of the system is based on music listening. I learned that lesson in the past from having discussions with Sanjay.





I would not "crossover" to a subwoofer in the 40-50 Hz area or run my mains as large if I did not have 3 way speakers.

Running mains as large on a movie compatible system probably requires a 3-way speaker or a 2 way that has significant capabilities (meaning it is probably has a large cabinet).

I do have an NHT Evolution system that I have not setup yet that is simiar to what you have described. Evolution 3-way mains crossed to Evolution 12" subwoofers (4 total) that the R & L speakers can sit on if I choose to set them up that way. That setup depends on the room's FR in the bass region, so the location of the 12" subwoofers is up in the air.


Main Evolution speaker that can be used either vertical or horizontal (AKA same speaker all around).