[JLM]

Wayner brings up a good point (that Scotty mentioned above), room construction.  With expotentially more energy involved the walls/floor/ceiling (especially with open crawl spaces under floors) can easily act as diaphragm resonators, producing much of the "one note" bass we've all heard.

[7x57]

Eminent Technology is the leader in low frequency bass transducers with a patented system that goes down to sub-1Hz, basically down to DC if the source material had that information. The LF system needs to be installed in a cavity outside of the room with hopefully venting to outside air and the room would need to be sealed to go down to DC. It is basically a spinning fan blade with very fast servo motors that rapidly change blade pitch and therefore the direction that air is pumped. A true sub-hearing range speaker is an air pump of some kind. The laws of physics applies a low frequency limit to a pistonic cone or moving diaphragm speaker. Doppler distortion is a fact with a system that moves in line with sound waves, so the line of motion must be at 90 degrees as in the Eminent Technology solution. The speed of the fan blades is just as fast at 1 Hz as it is at 20 Hz. For speed to stay constant, and constant SPL is from constant speed of acceleration, the distance traveled is far too long for any pistonic transducer at very low frequencies. The suspension reaches its limit at some point. SPL and frequency determines how far the cone must move to maintain flat frequency response.

My home has many resonance chambers connected to my listening room. An entryway with closet, an exit arch leading to 3 different sized rooms, an exit arch through two different sized rooms with another arch between them and then a walled stariway leading to a basement with 3 different chambers, one of them consisting of two rooms. Closing the doors to these resonant chambers has an effect on bass response. The stairway to the basement has a very definite Helmholtz resonance, like standing in the port vent of a huge bass reflex speaker. Closing the stairwell door has an effect on very low bass. There is a basement room under my living room, and I can open an overhead door that leads from my listening room to the attic. I have large flexible windows and sheetrock all around, which all have their own low frequency resonance. The resonances are not well damped and have lots of overhang when excited. If a certain song has a bad resonance bump, you can tune the room by opening and closing doors.

[Nuance]

The room is very influential below the Schroeder Frequency, so taking it out of the equation the best that you can will make a significant difference (the biggest difference IMO).  Put some bass traps in the corners and purchase a Parametric EQ unit such as a Behringer 1124p and use it along with REW to apply PEQ filters to achieve the desired response.  Proper placement + bass traps + PEQ = much better in-room bass response.  This, of course, is contingent on your speakers and subs being able to provide good bass to begin with.

Yes, I know this thread is old.

[DS-21]

The room is very influential below the Schroeder Frequency, so taking it out of the equation the best that you can will make a significant difference (the biggest difference IMO).

Yes.

Put some bass traps in the corners

Room mutilation is not only ugly, but also ineffective. Effective "bass traps" are better called "false walls with constrained layer damping."

and purchase a Parametric EQ unit such as a Behringer 1124p and use it along with REW to apply PEQ filters to achieve the desired response.  Proper placement + bass traps + PEQ = much better in-room bass response.  This, of course, is contingent on your speakers and subs being able to provide good bass to begin with, though.

Parametric EQ alone is fine for a very confined listening position, such as a nearfield setup. Otherwise, it causes many more problems than it solves. (Especially if used with single-point measurements, but also when used with proper spatial averages.)

But if used properly, i.e. as the icing atop a multiple subwoofer cake, EQ can be useful to fix minor problems. And in the first mode region, EQ is the only thing that really does anything.

For people who actually care about how music sounds, multisubs are not optional. "Stereo" or "mono" is irrelevant at these frequencies.

[stevenkelby]

Room mutilation is not only ugly, but also ineffective. Effective "bass traps" are better called "false walls with constrained layer damping."

Wow that's a bold statement!

"Ugly" is subjective and irrational in my opinion, but calling conventional bass traps ineffective is a controversial thing to say.

I know that you know your stuff though so have to ask, do you really mean that all "normal" bass trapping/room treatments are ineffective?

I would define normal as products sold by the "big 2" in room treatments.

[DS-21]

I know that you know your stuff though so have to ask, do you really mean that all "normal" bass trapping/room treatments are ineffective?

Yes.

Unless one considers measures that actually work, such as building false walls with constrained layer damping on one of every pair of room walls (i.e. front or back, left or right, floor or ceiling,) to be "normal."

[stevenkelby]

Yes.

Unless one considers measures that actually work, such as building false walls with constrained layer damping on one of every pair of room walls (i.e. front or back, left or right, floor or ceiling,) to be "normal."

Thanks for the reply.

I wouldn't think that would be normal no:)

I am surprised tough, you're the first person I've read who doesn't think normal trapping works.

What are you basing that on, have you tried it and it doesn't do much?

I've read so many threads where people put 4" or 6" traps in all the corners, maybe a couple on the walls, and measure a much flatter response VS no traps. How do you respond to that?

Can you give me any more info on your point of view?

How about diffusion, do you consider that useful or not?

I am considering building both but have not as of yet.

Thanks and best regards,

Steve.

[earwaxxer]

I voted none of the above, because in my DIY world, I have improved on my HSU sub by hacking out the driver, and getting a monster amount of power in the shape of a Crown pro amp. It blows away the stock HSU!

So I would say, good driver, tons 'o' power!

[DS-21]

I am surprised tough, you're the first person I've read who doesn't think normal trapping works.

In the bass, it doesn't. Up higher, room mutilation can be used to some degree to compensate for incompetently-designed loudspeakers. I prefer the approach of competently-designed loudspeakers and no room mutilation.

I've read so many threads where people put 4" or 6" traps in all the corners, maybe a couple on the walls, and measure a much flatter response VS no traps. How do you respond to that?

I've yet to see any measurements showing material improvements in the modal region or below from marring one's room with ugly traps.

How about diffusion, do you consider that useful or not?

Down low, no. In the midrange, it depends. Can be good, can be bad. I prefer not to have the issue by using speakers that are competently-designed, i.e. without directivity shifts in the midrange.

That said, my idea of "diffusion" is not "buy some ugly audiophile thing" but rather "put a bookcase with your favorite books there."

[stevenkelby]

OK thanks, makes things clearer

[medium jim]

No personal attacks...

[stevenkelby]

Apologies if I crossed a line, do you think I did?

I didn't mean to. Post edited anyway

[Jonathon Janusz]

In the bass, it doesn't. Up higher, room mutilation can be used to some degree to compensate for incompetently-designed loudspeakers. I prefer the approach of competently-designed loudspeakers and no room mutilation.

Down low, no. In the midrange, it depends. Can be good, can be bad. I prefer not to have the issue by using speakers that are competently-designed, i.e. without directivity shifts in the midrange.

That said, my idea of "diffusion" is not "buy some ugly audiophile thing" but rather "put a bookcase with your favorite books there."

Okay. . . I'll stick my neck out and give this a shot. . .

Specifically, in regards to the current conversation, what types of speakers (or is it a model-to-model thing?) would you consider "incompetently designed"?  Being constructive, do you have any examples to offer of what you would consider "competently designed"?

Regarding your viewpoint on "diffusion", are you suggesting there is no difference in performance between a purpose-built, scientifically researched, intentionally designed, lab and real-world tested, application-specific diffusion system and a basically arbitrarily arranged, thoughtfully placed book shelf?  Alternately, in your statement are you suggesting that although there is a notable difference in performance between the two, with your priorities in your system and in how you have it configured that the difference in performance did not justify the use of one over the other?

Thank you in advance for any clarification of your points.

[JLM]

With bass think of sound traveling in waves, with mid/high frequencies (above the Schroeder Frequency) think of sound traveling in rays.  Commerical absorption treatments are typically too small to help with bass and if not, would over dampen the mid/high frequencies.  Diffusors are just too small to help with bass, even mid/bass. 

Multiple subs, properly positioned, is the most effective way to deal with bass in residentially sized rooms.  Read Floyd Toole's "Sound Reproduction" and think of a room like a bathtub with bass waves acting like water being pushed back and forth along the length of the tub. 

For those who already own a sub or full range speakers, this should be a reasonably effective solution:

http://www.spatialcomputer.com/page9/page10/page10.html

[ptmconsulting]

Yes, of course a good subwoofer will help. Yes, room treatments make a difference, and can tame boomy bass issues. Yes, using a SS amp instead of a tube amp can do the same. But if you have those things covered then the best way I have found to firm up and extend the bass lower is to replace the crappy capacitors most speakers have in their crossover with a better brand. Also check out the inductors in the bass section and replace them with air cores or pot them.

[oboaudio]

Eminent Technology is the leader in low frequency bass transducers with a patented system that goes down to sub-1Hz, basically down to DC if the source material had that information. The LF system needs to be installed in a cavity outside of the room with hopefully venting to outside air and the room would need to be sealed to go down to DC. It is basically a spinning fan blade with very fast servo motors that rapidly change blade pitch and therefore the direction that air is pumped. A true sub-hearing range speaker is an air pump of some kind. The laws of physics applies a low frequency limit to a pistonic cone or moving diaphragm speaker. Doppler distortion is a fact with a system that moves in line with sound waves, so the line of motion must be at 90 degrees as in the Eminent Technology solution. The speed of the fan blades is just as fast at 1 Hz as it is at 20 Hz. For speed to stay constant, and constant SPL is from constant speed of acceleration, the distance traveled is far too long for any pistonic transducer at very low frequencies. The suspension reaches its limit at some point. SPL and frequency determines how far the cone must move to maintain flat frequency response.

My home has many resonance chambers connected to my listening room. An entryway with closet, an exit arch leading to 3 different sized rooms, an exit arch through two different sized rooms with another arch between them and then a walled stariway leading to a basement with 3 different chambers, one of them consisting of two rooms. Closing the doors to these resonant chambers has an effect on bass response. The stairway to the basement has a very definite Helmholtz resonance, like standing in the port vent of a huge bass reflex speaker. Closing the stairwell door has an effect on very low bass. There is a basement room under my living room, and I can open an overhead door that leads from my listening room to the attic. I have large flexible windows and sheetrock all around, which all have their own low frequency resonance. The resonances are not well damped and have lots of overhang when excited. If a certain song has a bad resonance bump, you can tune the room by opening and closing doors.

Adding a Eminent Technology TRW-1 Rotary subwoofer is the way to go if one wants very low and powerful bass.    Pipe organ
music is the most difficult to reproduce with low distortion and realism.   Low bass transients are just awesome with this subwoofer,
and no conventional sub can achieve what the rotary can.    There is no going back to conventional subs after hearing the rotary.

I use this sub in conjunction with Magneplanar Tympani IV bass panels, which reproduce bass to just below 30 hz with the same
great transient response and the two work together (coherence is awesome) seamlessly.   

Great sounding bass also requires a room that is designed for this kind of performance.    Many bass traps are needed, as well as,
construction of room, etc.   

[medium jim]

Yes, of course a good subwoofer will help. Yes, room treatments make a difference, and can tame boomy bass issues. Yes, using a SS amp instead of a tube amp can do the same. But if you have those things covered then the best way I have found to firm up and extend the bass lower is to replace the crappy capacitors most speakers have in their crossover with a better brand. Also check out the inductors in the bass section and replace them with air cores or pot them.

I disagree with the comment about SS vs Tube amplification.   Please explain in the difference. 

Jim

[JLM]

oboaudio,

The rotary woofer is most impressive, but is there an application for music?

For the $24,000 stated cost plus creation of a rigid infinite baffle (that wouldn't transmit vibration throughout the house, cracking drywall/etc.) there'd better be a dramatic effect.

[DS-21]

Specifically, in regards to the current conversation, what types of speakers (or is it a model-to-model thing?) would you consider "incompetently designed"?  Being constructive, do you have any examples to offer of what you would consider "competently designed"?

Most so-called high end speakers are incompetently designed, but it's out of the scope of the topic so I'll be brief: if it has a flush-mounted tweeter and a midrange larger than 4", maybe 4.5", or a tweeter capable of playing especially low, it's incompetently designed.

For more, see my review essay on the Soundfield Audio Monitor 1.

As for a few off-the-cuff examples of competently designed speakers at various pricepoints, the above SAM1, all of the Pioneer Elite and TAD speakers by Andrew Jones, KEF Q100, Revel Salon2, Gradient Revolution, all the GedLee speakers.

Regarding your viewpoint on "diffusion", are you suggesting there is no difference in performance between a purpose-built, scientifically researched, intentionally designed, lab and real-world tested, application-specific diffusion system and a basically arbitrarily arranged, thoughtfully placed book shelf?

In the modal region and below, a "diffusion system" doesn't do a bloody thing. Above that (again out of the scope here, so I'll be brief) such room mutilation may change things, but there is in truth very little relevant "science" behind such things. Yes, there are measurements, but very little in terms of perceptual studies. At any rate, get a speaker with controlled directivity and a midrange/treble pattern appropriate to the room, and room mutilation is unnecessary.

Yes, of course a good subwoofer will help. Yes, room treatments make a difference, and can tame boomy bass issues. Yes, using a SS amp instead of a tube amp can do the same. But if you have those things covered then the best way I have found to firm up and extend the bass lower is to replace the crappy capacitors most speakers have in their crossover with a better brand. Also check out the inductors in the bass section and replace them with air cores or pot them.

Is it April 1st somewhere in the world?

And what is a "better" brand of a commodity part like a capacitor? One taken from the usual factories (only a few make the things) and silkscreened by some "high end" company? (Indeed, the few times I've personally played with "boutique" caps. the primary distinguishing factor of them was that their tolerances were appreciably worse than standard Solen/Orca/Dayton caps of the same type.)

That said, there may be a smidgen of merit - but no more! - to the point about inductors. (Though "potting" them, assuming that word is used in the common sense of "surrounding with some resin of some sort," is just a waste of time and materials.) Solid-core chokes may saturate at high power, which can cause problems. However, arbitrarily replacing chokes in a crossover is going to just mess things up. Competent crossover designers treat the DC resistance of a choke as part of the crossover circuit, and for a given inductance the DCR of an air core choke is going to be very different from a solid-core choke.

[medium jim]

I thought I was in a thread about getting better bass, but the last several posts make me wonder!  Great reading and points of views...
Jim