how big is your woofer, how big is your box, what's your sensitivity

[James]

The ATC ports are not a typical reflex port implementation. They have a third-order roll off, i.e. between a typical reflex port and a sealed box.

Extended Bass Shelf or whatever. They still rely on Helmholtz resonance, which is a vibrating column of air tuned to a particular frequency. The last time I looked, vibrating air = sound.

 

[andyr]

609 sq in ... no box ... 84dB.

Andy

 

[Blzebub]

The last time I looked, vibrating air = sound.

It depends on the frequency. The ports are silent, so I think the frequency must be inaudible, i.e. 20 Hz or less.

 

[darrenyeats]

The last time I looked, vibrating air = sound.

Sure. All I said was it's not a typical reflex port implementation, and it has a third-order roll off.

 

[Guest432]

70 litres
6 ohms
89 dB

Sound bloody lovely

 

[merlin]

It depends on the frequency. The ports are silent, so I think the frequency must be inaudible, i.e. 20 Hz or less.

It's unlikely to be that low Bub.

It will most likely coincide with the Fs of the bass driver - which for the '50's will be around 30hz. The 150's will indeed be closer to 20hz although I don't have the specs for the drive unit.

JBL do something similar with the ports tuned to the drive unit's resonance - in their case 27hz. They place the ports on the back in order to reduce the chance of any "chuffing noise"...

 

[Blzebub]

Mine won't blow out candles, and I think chuffing noises are chuffing unlikely ever to happen. 18-20Hz seems likely for such an otherwise sensible piece of engineering. And the bass is truly awesome, which is the whole point.

 

[merlin]

Bass is IME always the strong point of active loudspeakers.

 

[Fox]

Extended Bass Shelf or whatever. They still rely on Helmholtz resonance, which is a vibrating column of air tuned to a particular frequency. The last time I looked, vibrating air = sound.

Ooh ooh, can. Show you my helmholtz resonator? Still a work in progress btw a lot more wadding it scheduled to go in but according to the guy who designed the roof and acoustician the chamber is roughly tuned right with what we require for the room below it -- if not, or if speakers change or if more subs get added or bigger stuffs, the solution is to just keep adding/extracting wadding until it is right.

Saves all that fannying with RATS in the room (and even better than having rats in the loft).

It's ever so clever and prgagmaticy this sciency acousticy thingy, stuff. Glad I don't have to sweat over it.

 

[juz400]

A pair of 12" sealed box (aboot 1Ft Qubed) Subs, estimated low 90`s sensitivity

http://www.triadspeakers.com/products/iws15sub.html#tab1

Not using them as inwalls and quite pleased with what they can do with just a 30w Nap90/3 and minidsp driving them.
Certainly makes Liquid Strangers Cryogenic Encounters give you a kick up the arse!

[YOUTUBE]watch?v=uzT8O6DBflo[/YOUTUBE]



Picked them up of ebay recently from the guys at Lifestyle AV
http://www.lifestyle-av.co.uk/
Thought I`d give them a mention and linky for the Brilliant job they did packing them up and the rapid shipping too!
Thanks Guys!

 

[ChrisPa]

Clever is a subjective term, so I can only tell you what I think is clever about the system:

1) The drive unit correction enables any size drive unit(s) to produce bass as low as you want in a much smaller box that is normal - all within the limitiation of volume displacement of course.
2) The 1st order rolloff inherently means that the transient response is very good, certainly better than a 2nd order system (acoustic suspension) or 4th order system (vented box).
3) The compensation scheme also reduces drive unit distortion by around a factor of 10.

This sounds like there may be current drive going on rather than voltage drive. Noticeably reduces the distortion (and temperature and other effects) in a moving coil driver. But has to be equalised (compensated) because innately the driver/enclosure system is free to follow its natural resonances. This is not a problem because whilst the uncompensated frequency response isn't flat it has less distortion.

It's worth a Google for current drive speakers. I understand that the Grimm speakers use current drive to further improve/control distortion.

S-man's absolutely right, if his music sources don't require large excursions then he doesn't need bass drivers with large excursions. It's all about getting the gain structure right for the complete system.