I am completely serious. The Linkwitz stuff is not new - we were doing this a decade or more before him at Ford.
The fact is that the actual free field response of a woofer is completely irrelevant in a small room setting so all this "alignment" stuff is meaningless. You put a speaker in a box - who cares what its free-field response is - you use several of them and EQ the multiple drivers to smooth out the in-room response. It is the end result that matters, not the responses of whatever components go into the end result as individual elements.
The fact is that the actual free field response of a woofer is completely irrelevant in a small room setting so all this "alignment" stuff is meaningless. You put a speaker in a box - who cares what its free-field response is - you use several of them and EQ the multiple drivers to smooth out the in-room response. It is the end result that matters, not the responses of whatever components go into the end result as individual elements.
"Put a driver in a closed box, EQ it, what difference does it make what its Q, f0, or Vas is? "
Earl is exactly right on this.
Did you know that the sealed resonant frequency on Velodyne subs is over 80hz?
Same with Bag End subs.
Earl is exactly right on this.
Did you know that the sealed resonant frequency on Velodyne subs is over 80hz?
Same with Bag End subs.
Last edited:
This is similar to the dilemma of what difference you'll find from two different (properly functioning) compression drivers on a waveguide. When the two are equalised for their own differences, it comes down to the waveguides.
I know it seems non-intuitive to declare that the room is in control. Maybe you can try to lump the discrepancy into the spatial domain and see where that leads?
I know it seems non-intuitive to declare that the room is in control. Maybe you can try to lump the discrepancy into the spatial domain and see where that leads?
Four 21" drivers in a sealed box, about a 50hz resonance.
http://www.bagend.com/wp-content/uploads/2015/06/bassault-r.pdf
An externally hosted image should be here but it was not working when we last tested it.
http://www.bagend.com/wp-content/uploads/2015/06/bassault-r.pdf
"Put a driver in a closed box, EQ it, what difference does it make what its Q, f0, or Vas is? "
I've got a fane 15" driver here that will hit 96dB at xmax at 20Hz with either ~80w or ~240w depending on whether the box Q is 0.5 or 0.7. Surely it would be beneficial to keep the power low and not heat up the coil so much ? (if box size was not an issue)
The idea of sticking any old driver in a small box and brute force eq'ing it doesn't seem right to me. (unless you're using so many drivers / amps that they will never be stressed ? )
I've got a fane 15" driver here that will hit 96dB at xmax at 20Hz with either ~80w or ~240w depending on whether the box Q is 0.5 or 0.7. Surely it would be beneficial to keep the power low and not heat up the coil so much ? (if box size was not an issue)
The idea of sticking any old driver in a small box and brute force eq'ing it doesn't seem right to me. (unless you're using so many drivers / amps that they will never be stressed ? )
RobWells - context here is the key point. I only use 12" and 15" 400-600 watt pro woofers and I use as many as six of them in a small room. The speakers being overloaded is never an issue, although I have had trouble with some plate amps that just could not put out what they claimed they could. So yes, I am "using so many drivers / amps that they will never be stressed " One should never cut corners on LF capability as it just always seems to bite you back at some point. I am never a fan of "overkill", but somehow it just does seem like the LF stuff can get to that point.
That clears your statement up a bit. Do you consider box size for the midbass / midrange driver/s or eq that / those to the desired roll off too ?
Rob.
Rob.
Above the modal region of the room, one no long wants to have dispersed sources and the direct (i.e. anechoic) should be flat with a HF roll-off of several dB. And of course those are "EQ'd in the sense that the crossover is designed to yield this result. But in no case does the traditional TS parameters enter the picture. If I were to use a cone midrange then I suppose they might, but I don't do that.
cradeldorf - gee, thanks. After doing this for about 50 years I should hope that I would pick up something worthwhile.
Are there any alternative core materials to polyurethane for a Geddes-style sandwich wall construction? I only ask because of price: I am getting insanely high pricing locally for rigid PUR, like US$300+ for a 30mm sheet, $250+ for 16mm.
Looking for the same properties, though: light, high damping, amenable to fibreglass coating.
Looking for the same properties, though: light, high damping, amenable to fibreglass coating.
Yea, I'd like to find an alternative as well!! I pay those prices now, and I haven't found an alternative. Next best, I would say, is the eleven ply Baltic birch plywood, but it is much heavier.
Thanks Earl, no, I won't be going back to plywood. So, none of those other closed cell foams are close. Interesting.
I presume you use rigid PUR sheets and not casting your own molds? That looks like much more work to me.
I also see a lot of variation in rigid PUR density, SD from 0.03 to 0.5. Is it a case of the lighter the better? Discussion in this thread says lighter is better, but is there a point where the PUR damping is insufficient with super-light foams?
I presume you use rigid PUR sheets and not casting your own molds? That looks like much more work to me.
I also see a lot of variation in rigid PUR density, SD from 0.03 to 0.5. Is it a case of the lighter the better? Discussion in this thread says lighter is better, but is there a point where the PUR damping is insufficient with super-light foams?
Hi and thanks a lot for the very interesting thread.
I have some questions ...
May i ask you few words about the sound from these speakers from ACI ? maybe a nice soundstage ?
i am trying to understand how the excellent cabinet construction contributes to the sound
do you refer to the sound generated by the knock test ?
this is a very interesting test because is very easy to carry out.
What should i heard from a good cabinet ?
sorry but i have not been through all the thread ... have you posted them ?
if so i will look for them.
Thanks a lot again for the very interesting thread
The cabinet design and construction issues interest me a lot indeed.
Regards, gino
I have some questions ...
May i ask you few words about the sound from these speakers from ACI ? maybe a nice soundstage ?
i am trying to understand how the excellent cabinet construction contributes to the sound
do you refer to the sound generated by the knock test ?
this is a very interesting test because is very easy to carry out.
What should i heard from a good cabinet ?
sorry but i have not been through all the thread ... have you posted them ?
if so i will look for them.
Thanks a lot again for the very interesting thread
The cabinet design and construction issues interest me a lot indeed.
Regards, gino
Last edited:
I use both cast poly and boards, mixed together where each is the best solution to the problem. I do use the "lighter" density boards (not sure if it is the lightest) because the stiffness to weight ratio is greater than the denser boards. I don't recall the actual density, but the boards are pink.
What about harmonic distortion measurements? typical harmonic distortion measurements for speakers show various even and odd order distortions at far lower levels than the fundamental, and while they may not change the frequency response in most cases, they most certainly do contribute to the sonic signature. Wouldn't the sound radiation of an enclosure be no different? Cone resonances certainly have a direct impact on harmonic distortion, it seems like cabinet resonances would also. Perhaps this could be an effective way to measure the cabinet influences.