I know that the design of my sealed bass bins allows 85dB at 10Hz (Xmax limited). And the design of my sealed IB sub (parts in the garage, but not yet together) allows 92dB at the same frequency.
But I never actually thought of measuring them (or even using that frequency range really). I wonder what sort of boost you get from the room at those frequencies...
But I never actually thought of measuring them (or even using that frequency range really). I wonder what sort of boost you get from the room at those frequencies...
just a guy,
As I know, Infinite Baffel, IB, means a baffle that never ends, it is closed. So IB just means a sealed box. Using a adjacent room is just an extreme version of that. That is not out of the question.
As far as using more drivers than one, this does increase sound pressure level, but it does not otherwise extend low frequency limits. I'd prefere just one InfraSub. Now, I also know that room dynamics can make multiples desireable.
As far a impedance bumps. I know you can find fs on most drivers by looking for the impedance bump. So it must be there.
I know enclosures have a roll off. But it can be tuned real real low. But I think drivers also have a roll of from fs too.
I know about nausea and infra bass. Its been known for decades. I plan to use such sparingly. Obviously all of this is in the realm of experimenting with some extremes.
As I know, Infinite Baffel, IB, means a baffle that never ends, it is closed. So IB just means a sealed box. Using a adjacent room is just an extreme version of that. That is not out of the question.
As far as using more drivers than one, this does increase sound pressure level, but it does not otherwise extend low frequency limits. I'd prefere just one InfraSub. Now, I also know that room dynamics can make multiples desireable.
As far a impedance bumps. I know you can find fs on most drivers by looking for the impedance bump. So it must be there.
I know enclosures have a roll off. But it can be tuned real real low. But I think drivers also have a roll of from fs too.
I know about nausea and infra bass. Its been known for decades. I plan to use such sparingly. Obviously all of this is in the realm of experimenting with some extremes.
IB can be a sealed box but does not necessarily have to be. If weather were not a concern you could mount them on an exterior wall. The point is that the box or lack of do not inhibit the driver in any way. This reduces effective fs and removes box colorations. But power handling goes way down and becomes limited by mechanical excursion.
If you want an sub enclosure of reasonable size (10-30 cubic feet) with a reasonable amount of power your choices are ported like Steve's or tl or bandpass.
Distortion is certainly an issue with all speakers and certainly very low tuned subs but some enclosure types (IB and tl) can reduce distortion, but each design has it's own benefits.
If you want an sub enclosure of reasonable size (10-30 cubic feet) with a reasonable amount of power your choices are ported like Steve's or tl or bandpass.
Distortion is certainly an issue with all speakers and certainly very low tuned subs but some enclosure types (IB and tl) can reduce distortion, but each design has it's own benefits.
bassawdyo
You are correct about the organ pipes having harmonics. This is part of what links them harmonically to the rest of the music.
But you do also feel the fundamental, and this kinestetic perception, in the abdominal region, does seem to link with hearing.
bass and steve, I'm hearing diffent things about the need for Eq.
But about 10hz measurements.
When they publish speaker response numbers, they usually don't go down too low. Rather they have to stop because of the size of the anechoic chamber they are using, and the distance from the microphone.
Now, I know that what you experience in your listening room is also a function of that room. Some times bass is managed to compensate for these room issues.
You are correct about the organ pipes having harmonics. This is part of what links them harmonically to the rest of the music.
But you do also feel the fundamental, and this kinestetic perception, in the abdominal region, does seem to link with hearing.
bass and steve, I'm hearing diffent things about the need for Eq.
But about 10hz measurements.
When they publish speaker response numbers, they usually don't go down too low. Rather they have to stop because of the size of the anechoic chamber they are using, and the distance from the microphone.
Now, I know that what you experience in your listening room is also a function of that room. Some times bass is managed to compensate for these room issues.
A lot of the supposed rules change when dealing with very low tuned subs. Compromises must be made. I am betting your reference material does not cover much ground on subwoofers and probably none on the type we are talking about.
It seems like you are willing to spend a load of money sometime in the future and it really isn't necessary. Steve's sub is in the range of what you are looking for. I'm not sure what he has invested but there are plenty of designs that can be built complete for under $1000 that will shake your house apart.
You never mentioned yet what SPL levels you are looking for, how much power you can afford and the exact freqency range you want to reproduce. Even if this is just a theoretical study, those answers will lead to specific designs.
It seems like you are willing to spend a load of money sometime in the future and it really isn't necessary. Steve's sub is in the range of what you are looking for. I'm not sure what he has invested but there are plenty of designs that can be built complete for under $1000 that will shake your house apart.
You never mentioned yet what SPL levels you are looking for, how much power you can afford and the exact freqency range you want to reproduce. Even if this is just a theoretical study, those answers will lead to specific designs.
What I am envisioning is in stages. But the ultimate would be a built in large enclosure.
I want to make a built in amp, running off 230VAC. It could be a few thousand watts class D.
I'd like to comfortably do 8hz, or maybe lower and high sound pressure level.
To me the simplist would be one giant driver with a low fs, if such exists. I though a 32" would do it. But they are not that low.
So I want to look at the full range of possibilities and trade-offs.
Peerless speakers, they have 10hz fs?
I want to make a built in amp, running off 230VAC. It could be a few thousand watts class D.
I'd like to comfortably do 8hz, or maybe lower and high sound pressure level.
To me the simplist would be one giant driver with a low fs, if such exists. I though a 32" would do it. But they are not that low.
So I want to look at the full range of possibilities and trade-offs.
Peerless speakers, they have 10hz fs?
phase accurate, There are places to get the materials to make custom toroids. That is how I am thinking. Of course I want a transformer.
But, is have seen some tower speakers in audio phile mags that have a subwoofer amp built in, and its just a little circuit board. I think they are going unisolated. I don't like that idea.
They also don't have much filtering So they depend on the amp circiut to reject power supply ripple. That can mean lower thermal efficiency, because during some of the 60hz cycle, you have more voltage than you need by far. I think those amps are only for short power bursts.
But, is have seen some tower speakers in audio phile mags that have a subwoofer amp built in, and its just a little circuit board. I think they are going unisolated. I don't like that idea.
They also don't have much filtering So they depend on the amp circiut to reject power supply ripple. That can mean lower thermal efficiency, because during some of the 60hz cycle, you have more voltage than you need by far. I think those amps are only for short power bursts.
Hi Zenmasterbrian. The bass response i have here now is from two way speakers with 20cm bass unit in a ML-TQWT. It goes down to 28 Hz, and is the more natural sounding bass for me compared to bassreflex. Even with home cinema it is sounding good.
When the sub is ready eventually, I problably get a less "restrained" sound from main speakers and can dig slight deeper in the bass-basement.
just a guy, and all about going below fs.
I think I'm starting to understand this better now.
An Isobaric Enclosure, means one so big that there are no pressure changes.
Well, that certainly is a non-resonant way of thinking.
With a standard system, running above fs, with an Infinite Baffle, there are pressure changes, but that is not lost amp power. Rather, it just adds to the speakers suspension. You get the power back.
When you are way way below fs, everything is different!
Presure increases do mean lost movement and extra amp power and extra voice coil heat.
You really are just using the speaker's motor against its own suspension. Very little power goes into moving air.
It would seem that soft suspension would be desired.
But also, you are driving an impedance way way below the published number. The amp has to be made to do this. Its actuall output power has to be re-evaluated. The Power supply rails need be moved, etc.
The voice coil heat would become a big big issue.
Now, if you go away from isobaric, and back to resonant enclosure, but still below fs, things change again. This is complex.
I still see impedance bump issues.
Some have talked about making constant current amps to drive speakers. So the drive with a current source instead of a voltage source. Maybe that is the way to go, for far below fs?
I think I'm starting to understand this better now.
An Isobaric Enclosure, means one so big that there are no pressure changes.
Well, that certainly is a non-resonant way of thinking.
With a standard system, running above fs, with an Infinite Baffle, there are pressure changes, but that is not lost amp power. Rather, it just adds to the speakers suspension. You get the power back.
When you are way way below fs, everything is different!
Presure increases do mean lost movement and extra amp power and extra voice coil heat.
You really are just using the speaker's motor against its own suspension. Very little power goes into moving air.
It would seem that soft suspension would be desired.
But also, you are driving an impedance way way below the published number. The amp has to be made to do this. Its actuall output power has to be re-evaluated. The Power supply rails need be moved, etc.
The voice coil heat would become a big big issue.
Now, if you go away from isobaric, and back to resonant enclosure, but still below fs, things change again. This is complex.
I still see impedance bump issues.
Some have talked about making constant current amps to drive speakers. So the drive with a current source instead of a voltage source. Maybe that is the way to go, for far below fs?
A while back someone said that distortion explodes when you go below fs.
Now I understand. That is because its controlled by the linearity of the driver's suspension and motor. These are not especially linear.
Above fs, its energy storage, spring and mass. So the primary resonance is a sine wave.
But also, you have your enclosure, air suspension.
Again, I'm thinking this current driving way could be best.
Martin Colloms thinks current source amps could be better for all loudspeaker applications. It only been lightly explored.
With current driving, I don't thing there would be impedance bump or many other problems. Still might need some simple eq.
That is still going to be hard on the driver! Way below fs, the electrical power is all going into voice coil heat.
Maybe need a special class of drivers intended for below fs use, and with current source amps being recommended.
Now I understand. That is because its controlled by the linearity of the driver's suspension and motor. These are not especially linear.
Above fs, its energy storage, spring and mass. So the primary resonance is a sine wave.
But also, you have your enclosure, air suspension.
Again, I'm thinking this current driving way could be best.
Martin Colloms thinks current source amps could be better for all loudspeaker applications. It only been lightly explored.
With current driving, I don't thing there would be impedance bump or many other problems. Still might need some simple eq.
That is still going to be hard on the driver! Way below fs, the electrical power is all going into voice coil heat.
Maybe need a special class of drivers intended for below fs use, and with current source amps being recommended.
BassAwdyO, the differences in the timing between pulses running through the floor can actually be sensed. Though I guess it gets back to you saying different things in the room will begin to resonate at different low frequencies, my floor felt like it was actually flexing as opposed to just vibrating with 10hz and 12hz sine waves.
That's because the foam wedges they use to absorb sound aren't nearly long enough to absorb really low frequencies. Their purpose for testing in an anechoic chamber is to remove all reflections and boundary gains to see what a speaker puts out by itself with no "contamination". My subwoofer definitely won't measure flat to 10hz anechoically, like I explained earlier, but it's anechoic output does lend itself to mesh very well with room gain, and thus, in room, I am flat to 10hz with a subtle house curve. That's basically the goal with a sealed subwoofer, but you'll find that most rooms won't yield a 12db/octave gain (most are too large and not air tight) - the rolloff should be more shallow. Ultimately I have to put up with the steeper 4th order rolloff of my ported design, but it occurs low enough that I can still manage my flatness to 10hz.
It comes out to about $750 per sub for me including amplification. I've got two more waiting in the wings
The problem I see in that is that there is no competition in that kind of market, so those exotic, extremely large drivers typically don't end up being as good as they can be or should be, and the price gets ridiculous rather quickly. Just my opinion, but I think you'd be much better off going with multiples of 15-18" drivers. And again, you don't have to obsess over Fs, it's not going to make or break the design.
Now you are getting isobaric and IB mixed up. No big deal, isobaric is a loading method, IB is an enclosure. With IB there is no air spring for the driver to fight against so it moves very freely with only the suspension to keep excursion in check.
I don't think you really understand what you are asking for. If you are thinking Steve's sub would not be enough for you it would be interesting to see what you think might make you happy. Steve has shown a frequency response that is relatively flat to 10 hz, and even if the graph doesn't go any further down, the sub output does. I don't remember if he said what SPL he gets at 10, but I'm sure it's enough, especially with more identical units in the future. And it costs less than half of what you are willing to pay for raw drivers. Look at his FR curve. Does it look to you like there are big problems with impedance or overdriven amps? Look again and see that this sub is exactly what you are after. A measured frequency response curve does not lie.
More about Peerless low fs drivers...I saw them on their website but there is no info on them whatsoever except their moving mass (over 400 g) and fs (somewhere around 10 hz). I haven't seen them for sale anywhere. These drivers will not be large, probably 10 or 12 inch at most and are likely optomized for small sealed enclosures but could be used with other types of enclosures if ts parameters are known. They are likely to be very expensive and hard to find.
Now at this point you can continue to try to sort all this out intellectually, which is not working, because your trusted reference materials are not even talking about the right subject (super low tuned subs) or you can download WinISD and experiment and find out exactly what happens below fs with graphical documentation immediately.
Download WinISD, it's free.
Select any driver from the database, there are lots.
Model the driver in it's recommended vented enclosure.
Now make changes, add volume to the box, change tuning, add weight to the cone, add another driver in isobaric fashion, change port lengths and widths, etc.
This will show you response curves similar to the one Steve posted, but without room gain. If there are impedance bumps they will be shown. You can also look at max power rating vs frequency, max output and a multitude of other factors that we haven't even mentioned.
If you get a bit disappointed in the sensitivity drop when tuning very low it might be time to read up on tl theory a bit. My driver models 5 db higher in a tl than a ported box with the same tuning. That is a huge difference.
I really don't understand why you want to cling to the notion that this is going to require huge expensive drivers. 8 hz at 130 db is going to cause problems anyway. If you have plaster anywhere in your house it will crack and disintegrate. That goes for your neighbour's house too. You might not incur any structural damage but drywall joints will crack and bad things will happen. Your house - any house - was not made to sustain 8 hz at high volume, you are actually recreating an earthquake at realistic levels. Obviously the lower you go and the higher the SPL level the worse it's going to treat your house.
I don't think you really understand what you are asking for. If you are thinking Steve's sub would not be enough for you it would be interesting to see what you think might make you happy. Steve has shown a frequency response that is relatively flat to 10 hz, and even if the graph doesn't go any further down, the sub output does. I don't remember if he said what SPL he gets at 10, but I'm sure it's enough, especially with more identical units in the future. And it costs less than half of what you are willing to pay for raw drivers. Look at his FR curve. Does it look to you like there are big problems with impedance or overdriven amps? Look again and see that this sub is exactly what you are after. A measured frequency response curve does not lie.
More about Peerless low fs drivers...I saw them on their website but there is no info on them whatsoever except their moving mass (over 400 g) and fs (somewhere around 10 hz). I haven't seen them for sale anywhere. These drivers will not be large, probably 10 or 12 inch at most and are likely optomized for small sealed enclosures but could be used with other types of enclosures if ts parameters are known. They are likely to be very expensive and hard to find.
Now at this point you can continue to try to sort all this out intellectually, which is not working, because your trusted reference materials are not even talking about the right subject (super low tuned subs) or you can download WinISD and experiment and find out exactly what happens below fs with graphical documentation immediately.
Download WinISD, it's free.
Select any driver from the database, there are lots.
Model the driver in it's recommended vented enclosure.
Now make changes, add volume to the box, change tuning, add weight to the cone, add another driver in isobaric fashion, change port lengths and widths, etc.
This will show you response curves similar to the one Steve posted, but without room gain. If there are impedance bumps they will be shown. You can also look at max power rating vs frequency, max output and a multitude of other factors that we haven't even mentioned.
If you get a bit disappointed in the sensitivity drop when tuning very low it might be time to read up on tl theory a bit. My driver models 5 db higher in a tl than a ported box with the same tuning. That is a huge difference.
I really don't understand why you want to cling to the notion that this is going to require huge expensive drivers. 8 hz at 130 db is going to cause problems anyway. If you have plaster anywhere in your house it will crack and disintegrate. That goes for your neighbour's house too. You might not incur any structural damage but drywall joints will crack and bad things will happen. Your house - any house - was not made to sustain 8 hz at high volume, you are actually recreating an earthquake at realistic levels. Obviously the lower you go and the higher the SPL level the worse it's going to treat your house.
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