How can a DIYer produce a subwoofer that can go to 11hz with an enclosed isobaric configuration at -3db and 110db reference? It doesn't even seem possible. Yes these are engineered to take up less space, I'm not concerning myself with space, just in principle. What driver specifications would I look for to do an enclosed isobaric design and hit 11hz with only 1000W? I have used winisd and nothing seems to get even remotely close to that low without a port. If I use an Ultimax ii for example, I can't even come close to 11hz in an enclosed box no matter what I do. I can hammer in power and get spl, but then the response is nowhere near flat. Are they just EQing it down to be more flat?
As a new person learning how to build multi thousand dollar systems, what the heck am I missing? This just doesn't seem possible, but people are doing it.
https://us.kef.com/products/kc92-su...ltAwBynNoNxF2-ZNXttFOGH7uZzYksJkaAnu9EALw_wcB
As a new person learning how to build multi thousand dollar systems, what the heck am I missing? This just doesn't seem possible, but people are doing it.
https://us.kef.com/products/kc92-su...ltAwBynNoNxF2-ZNXttFOGH7uZzYksJkaAnu9EALw_wcB
Is that how KEF measures? With room gain added or nearfield? I'm wondering on how to make infrasonic subwoofers and it looks like nothing I can find can come even close, and this is in a TINY box. Yes they have custom drivers with large power handling, but in principle if I took 2 8in, 10in, etc drivers and chuck them in a sealed box of any size, I'm not able to come close to 11 at 107db. I don't know what drivers I'd have to choose to make that happen.
With 2 dayton audio ultimax ii 18in isobaric configuration with 2000W jammed at it I am looking at a 107db at around 11hz and near over excursion in a MASSIVE nearly 11ft3 (306L) enclosure. Yet somehow 2 9in drivers in a 14x14x14in box are managing 11hz at 107db.
If you were to use an isobaric configuration (only one driver exposed to the outside air), the drivers would have to have twice the displacement of the KEF KC92 (2x9") horizontally opposed drivers.
Any driver can hit 11Hz with a fraction of a watt, you (or KEF) have not specified the level.
The drivers used in the KEF KC92 have at most ~16mm excursion, output could be equalized -3dB 11Hz to 200Hz, but output would be no more than 89dB at 11Hz with no room gain.
With room gain, the level could be considerably louder, perhaps even approaching audible levels.
Max output is stated as 110 dB, which would only require ~2mm excursion at 100Hz, no problem with 500 watts per driver.
Yes, EQ along with dynamic DSP to limit LF output to under the excursion limits of the drivers, and keep the amps from clipping.
Like Bag End's Infrasub (with 8Hz response), the dynamic control of reducing the low frequency extension or amplitude will allow the system to play with the upper bass notes unaffected while protecting the system from overload caused by playing the lower notes louder than the amplifier and/or loudspeaker can reproduce safely and undistorted.
No, the SPL was not specified for 11Hz, only the -3dB points and maximum output.
No lies, other than by omission 😉.
Art
Ok so it is 110db but drops off like a rock to 90db at 11hz. Making it more peaky. Isn't this still isobaric because they are back to back sharing the same cavity, just with both drivers exposed to the air? Similar principle to push and pull each other instead of jamming energy into the box.
I did wonder why the output waves wouldn't cancel out with only a short distance between each signal being opposite of one another.
I did wonder why the output waves wouldn't cancel out with only a short distance between each signal being opposite of one another.
No, if the sub is playing at ~90 dB, response remains flat, as volume is increased, the lower level is reduced to keep excursion within set limits. No peaks are introduced, though the -3dB point raises as volume is increased.
No, the definition of isobaric is "constant or equal pressure", which is what the air contained between two isobaric drivers is:
Both the drivers in an isobaric are driven in the same direction, in a push pull "clamshell" configuration one driver is wired reverse polarity.
Single or multiple drivers in a sealed enclosure with all cones exposed to the outside air are not "isobaric", the pressure on either side is unequal. All the drivers push "out", or pull "in" together.
The larger the sealed cabinet, the less pressure differential between the two sides of the cone(s), so less power is required to push the drivers to their full excursion potential.
An 11Hz wave is 31.6 meters (103 feet) long.
The drivers are wired with the same polarity, at low frequencies the orientation of the drivers makes no difference to the output. Even at 200Hz, the KEF KC92 drivers are within 1/4 wavelength of each other, so will still have no cancellation.
The KEF KC92 horizontally opposed drivers cancel mechanical vibrations while also reducing cabinet height. If both woofers are on one side of an enclosure, any asymmetry in the reproduced waveforms will tend to make the cabinet rock or walk.
Art
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Oh they are firing at the same time and the back wave vibrations cancel, so it is just like 2 front facing drivers in terms of box volume, wouldn't that box have to be huge?
one of the first tests I tried a Behringer DEQ 2496 mit ECM8000 microfone was to linearize a loudspeaker down to 20hz just to find out it sounds horrible due to excessive bass.
Room gain adds up even not being close to side walls and you simply dont hear the mids anymore, psychoacoustically a desaster.
Room gain adds up even not being close to side walls and you simply dont hear the mids anymore, psychoacoustically a desaster.