Hi Paul
Thing is that this (new driver) is never going to happen (although B&C makes a 21" woofer that may be worth looking at). Thats because the sub 40 hz does not interest enough people for a manufacturer to look at it. And almost any good Pro driver can get down to 40 Hz with no problem. 20-40 Hz is another thing altogether. Realizing that no manufacturter would make a driver that goes this low, I looked at using existing drivers in obscure bandpass designs that can get down lowern - maybe not to 20 Hz., but close. It can be done, its very big and very inefficient and there simply is no way arround that limitation. The IB designs that are so popular makes the most sense if you want this very low bass. Any size limted box is going to be a compromise. I can't do IB in my room, but being sealed well it has a very large LF gain from presurization.
I have been thinking about an IB for the low end in my system, and plan to do some measurements to see if there is a reasonable location for it. I haven't quite gotten comfortable the concept of cutting a large hole in my hardwood floor yet, though.
-Doug
you can do it with some electronic trickery in a sealed box if you can handle a kit and a soldering iron.
P48 Sub-Woofer Controller (Rev-A)
I'm using one of these with a pair of car subs. Works fine.
col.
P48 Sub-Woofer Controller (Rev-A)
I'm using one of these with a pair of car subs. Works fine.
col.
Please remember the down-side of IB - the back side. There is as much radiation from that side as there is from the front, but it cannot go into the listening room it has to go somewhere else. make sure that this "somewhere else" is not somewhere that people will complain about. I have a friend who has an Ib sub in his floor. basically you cannot be in the house when this is playing UNLESS you are in the listening room. That a can be a big problem and a deal breaker in my house.
Once you use any form of electronic manipulation they all end up being the same thing in a different form - EQ. Just use a Berhringer DXC2496 to EQ ALL the subs at the same time, in-situ, and be done with it. This works fine but still requires a massive amount of power and excursion capability if you want to push the 20 Hz LF limit in a leaky room. In my room 15 Hz is no problem, but it is exceptionally well sealed - a big advantage of a sound proof room!!
Of the companies that I deal with, none of them make drivers with 20 Hz and below resonances. Perhaps there are some, but not mainstream. A 20 Hz resonance cone would be a big liability as far as reliabitity is concerned. Thats why the pro companies don't do it. I wouldn't want a cone that was so unsupported. Gravity alone would move this cone off center by a great deal if placed horizontally and it would stretch the suspension if placed vertically. You are simply asking for a failure with a driver like this.
Another issue with IB is the neighbours! A lot of IB guys put them in the ceiling. I'm surprised this issue isn't mentioned more often.
Sounds like Earl is talking about pro drivers. Home theatre subs with a fs of ~20 Hz are quite common. I'm not really up with the latest, but when I was more current a typical 12" HT sub driver had an fs around 20 Hz with the larger drivers often keeping the same efficiency and giving their bigger drivers low fs, more like 17 Hz.
Sounds like Earl is talking about pro drivers. Home theatre subs with a fs of ~20 Hz are quite common. I'm not really up with the latest, but when I was more current a typical 12" HT sub driver had an fs around 20 Hz with the larger drivers often keeping the same efficiency and giving their bigger drivers low fs, more like 17 Hz.
Links? http://www.bcspeakers.com/PDF/0000000015B&C - Product Comparison Matrix.pdf
Note that even the 21" Uber woofer is only 29 Hz. I believe B&C numbers. I would seriuosly doubt any consumer HT marketing numbers. They tend to report -3 or -6 dB numbers (exagerated) and not Fs.
My previous sub driver was the AE AV12 which had an fs of 21 Hz, but no longer shown on the website.
Exodus audio Shiva 12" has an fs of 21 Hz:
DIYCable.com : Intro » Home » Exodus Subwoofers » SPL: 85.1 db/1W/1M
and their massive 21" Maelstrom has an fs of 16 Hz:
DIYCable.com : Intro » Home » Exodus Subwoofers » SPL: 89.6 db/1W/1M
I must admit I was a little surprised to find that a lot of HT subs have a slightly higher fs where 25 Hz is more typical for a 12". Looking at Parts Express, their newer subs are in this range, but their older Dayton 12" DVC has an fs of 22 Hz. HT subs have changed a lot in the last 5 years.
Exodus DPL fs 19 Hz (IB driver)
DIYCable.com : Intro » Home » Exodus Subwoofers »
Exodus Tempest 15" fs 19.5 Hz
DIYCable.com : Intro » Home » Exodus Subwoofers »
Peerless XLS and XXLS - some of them have an fs below 20 Hz and need no introduction
XLS | Tymphany
XXLS | Tymphany
Exodus audio Shiva 12" has an fs of 21 Hz:
DIYCable.com : Intro » Home » Exodus Subwoofers » SPL: 85.1 db/1W/1M
and their massive 21" Maelstrom has an fs of 16 Hz:
DIYCable.com : Intro » Home » Exodus Subwoofers » SPL: 89.6 db/1W/1M
I must admit I was a little surprised to find that a lot of HT subs have a slightly higher fs where 25 Hz is more typical for a 12". Looking at Parts Express, their newer subs are in this range, but their older Dayton 12" DVC has an fs of 22 Hz. HT subs have changed a lot in the last 5 years.
Exodus DPL fs 19 Hz (IB driver)
DIYCable.com : Intro » Home » Exodus Subwoofers »
Exodus Tempest 15" fs 19.5 Hz
DIYCable.com : Intro » Home » Exodus Subwoofers »
Peerless XLS and XXLS - some of them have an fs below 20 Hz and need no introduction
XLS | Tymphany
XXLS | Tymphany
Those woofers all get their low fs with massive cones - and resulting very low sensitivity. I'm not sure where this is going, but I think that your post proves my main point that low frequencies mean low efficiency. I doubt that I would ever consider using any one of those drivers so I guess thats why I never noticed them. As I said, none of the companies that I would consider using ever get down that low in Fs.
Higher mms actually means more low end, higher low end sensitivity so to speak
Quite contradicting I would say
Apart from that, Qts seems the uebercontroller of how deep you can get
Low Fs sub drivers only get that low because they usually have very hign Qts
Usually, fore woofer you go fore max 0.4 Qts fore a closed design
And wouldnt dream of using such high Qts fore a BR design, but more like 0.35
If you choose a "strong" woofer with say 0.25 Qts, low end bass will be much less, or not very low at all
Sub drivers with 0.5 Qts is not unusual
It will even be used in BR designs
And maybe even with yet a bit of EQ
A really strange thing to think of, in light of its heavy cone, that ought to be better controlled with low Qts
Any woofer like that in a 3way would be considered sloppy, but not in a sub design
I really do not understand much of this
But obviously we are ready to compromise quite a lot to get the desired 20hz
Are we being blindfolded ?
Many people obviously believe they have very nice bass if the whole room is rumbling
Others think that a good sub should not be noticed at all, until its turned off, then you notice its gone
Quite contradicting I would say
Apart from that, Qts seems the uebercontroller of how deep you can get
Low Fs sub drivers only get that low because they usually have very hign Qts
Usually, fore woofer you go fore max 0.4 Qts fore a closed design
And wouldnt dream of using such high Qts fore a BR design, but more like 0.35
If you choose a "strong" woofer with say 0.25 Qts, low end bass will be much less, or not very low at all
Sub drivers with 0.5 Qts is not unusual
It will even be used in BR designs
And maybe even with yet a bit of EQ
A really strange thing to think of, in light of its heavy cone, that ought to be better controlled with low Qts
Any woofer like that in a 3way would be considered sloppy, but not in a sub design
I really do not understand much of this
But obviously we are ready to compromise quite a lot to get the desired 20hz
Are we being blindfolded ?
Many people obviously believe they have very nice bass if the whole room is rumbling
Others think that a good sub should not be noticed at all, until its turned off, then you notice its gone
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Just because of efficiency? I'm currently running one single sealed sub with a Shiva-X1. Never drove a Samson 120a into clipping athough it only delivers 60watts@4ohms.
Best, Markus
I ran some simulations a second ago so I could make this point. It's one that I’ve noticed before, it's what I was trying to point out, and I think has been lost on a few here. I do believe Dr. Geddes understands it. Take any of the popular 15" uber drivers with 60mm of xmax and 50000 watts power handling, put a pair of them in the biggest ported box tuned as low as you want, 8hz and 30 cubic feet. Besides being unreasonably large, even that setup is still limited in maximum low frequency spl and LF efficiency to a level about the same as any number of less uber drivers. Where they can beat the others is that they can handle greater power and move more air before hitting their limits. This is, of course, assuming they are being accurate in their results.
BMS has an 18" driver and B&C has that 21" driver that, just one of those, in a reasonable box, will produce within 3-4 db's of these pairs of uber drivers in both max spl and LF sensitivity. They all seem to converge in that area and you just end up having to pair lots and lots of drivers, maximizing the cone area, to get more sensitivity and output in that area.
As is during loud peaks in movies with a lot of lf effects, the power sags considerably causing my power conditioners to switch into their brown out modes. The projector is on a battery back up for protection as well, but I feel it is ridiculous to have to use those durring movies because I don't have enough efficiency in the low frequencies.
BMS has an 18" driver and B&C has that 21" driver that, just one of those, in a reasonable box, will produce within 3-4 db's of these pairs of uber drivers in both max spl and LF sensitivity. They all seem to converge in that area and you just end up having to pair lots and lots of drivers, maximizing the cone area, to get more sensitivity and output in that area.
As is during loud peaks in movies with a lot of lf effects, the power sags considerably causing my power conditioners to switch into their brown out modes. The projector is on a battery back up for protection as well, but I feel it is ridiculous to have to use those durring movies because I don't have enough efficiency in the low frequencies.
greater mms doesn't seem to increase LF sensitivity, it just lower the higher bass sensitivity so that the lower bass sensitivity is higher relative to that level. In other words, take a driver with a given MMS, say in a sealed box it's at 85db's at 40hz and at 150hz its 95db's. Now double the mms, massively lower the resonance, and what happens is that the 40hz point is still 85db's, but the 150hz is now 80db's.
I mean, I don't have speaker simulation software where I can fully design and test a driver to see how a driver properly designed around one moving mass works compared with a redesigned one with double the moving mass. Simply increasing the mass though seems to do that, akin to putting weights on the cone of a given driver. I've done this, it doesn't do anything good. I've simulated and tested simply increasing the MMS and it does nothing to increase LF sensitivity.
I mean, I don't have speaker simulation software where I can fully design and test a driver to see how a driver properly designed around one moving mass works compared with a redesigned one with double the moving mass. Simply increasing the mass though seems to do that, akin to putting weights on the cone of a given driver. I've done this, it doesn't do anything good. I've simulated and tested simply increasing the MMS and it does nothing to increase LF sensitivity.
They are not that special at all, at least not on paper, if you try and calculate
And they are way too expencive
Some of those new pro sub driver may cost up to 1000USD each, around here
Neither of those are anywhere near that price. The B&C is in the 700's and the BMS in the 400's. They are only special in that they have greater power handling and air movement abilities that many other drivers. There are other good 21" drivers, but the B&C is one of the best and most affordable. I'm not sure your point here Tinitus, just wanted to bash on the examples I gave, or was this something constructive? What would be your better choices for less money?
Yeah, I thought about that. One possibility is to close off the back end of my ~4' crawl space. That would create a ~144 cu ft 'enclosure' and also isolate it from the heating vents and the rest of the house. Of course that would also limit where I could put the outlet(s). Not a true IB, but there isn't a big difference in the response based on modeling. I also thought of building a large bandpass box with an external port that comes up to floor level, but I think the IB would be easier, and possibly more cost-effective.
- Doug
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