Mark_J_H_Jr
Stunt Coordinator
- Joined
- Jan 29, 2002
- Messages
- 72
The line array towers look very impressive. Where can I/we find more info about these. I have searched this site and AVS but don't find too much info.
Thanks
Thanks
As you know, acoustic solutions for acoustic problems is my credo, especially in our hearing's sensitive BW, so putting an XO in it is a no-no IMO.Credo dittos!
Bill
Please correct me if I'm wrong, but you mean a strip of felt along each side of the top and bottom third of the stack of mid-woofs, that gets thicker (adding a layer of felt every driver) towards the ends of the stack) out towards the ends of the stack?I'm suggesting completely obstructing some mid-woofs with felt, beginning with a single thin layer toward the middle of the array and adding a layer or two (only experimentation will tell) for each driver closer the top/bottom of the array. Since the felt is transparent to lower freqs and becomes progressively more opaque to higher ones, it would roll off the treble response of the top/bottom of the array, ideally with a net transfer function that is the inverse of the on-axis baffle step. The practical result is that the radiating portion of the array is progressively shortened as frequency increases, thereby minimizing comb filtering.
Also, vertical lobes from each felted driver would have to traverse comparatively more felt than on-axis radiation.
Overall, I think this felt treatment would let you keep the lower mid/bass efficiency that a power-tapered array throws away, while pulling off acoustic XO tricks that minimize comb filtering while leaving the time domain relatively unscathed.
Certainly, though, each implementation would need to be individually tuned.
I have recently been wondering about using acoustic foam and felt to treat arrays. It seems to me that acoustic foam wedges between drivers, like M&K uses--only more extreme, could simultaneously cut back on comb filtering and perhaps compensate for the baffle step....This would do little to minimize comb filtering effects.
With planar tweeters mounted about 1" apart from each other the comb filtering effects that occur between side by side drivers are above a frequency range that we are capable of hearing.
Adding the felt would have no effect on the filtering effects that take place through out the array.
Keep in mind that the cancellation is distance related.
You, or your ear, will always be closer to the center of the array than the ends and no amount of felt around the drivers is going to change that.
Comb filtering effects are the same on a long RD ribbon or New Form ribbon as well and it is a long single driver.
Adding this felt will not have an effect on sensitivity losses associated with baffle step loss either. Baffle step loss occurs from a lack of surface area to reflect from. Adding felt around woofers will minimize the surface area and increase the loss.
Adding this felt will not have an effect on sensitivity losses associated with baffle step loss either. Baffle step loss occurs from a lack of surface area to reflect from. Adding felt around woofers will minimize the surface area and increase the loss.I'm not sure I get you here... Are you saying that baffle-step loss will increase, as in become greater than the theoretical maximum of 6dB?
I think of baffle step in terms of spacial loading--that is (given a driver mounted in the center of a baffle with 90 deg. transitions to parallel sides in free space), above a certain frequency related to baffle width, the driver loads 1/2 the space it did at the bottom of its passband, so its on-axis SPL is up 6dB. Centered on the same freq. and over the range of this transition, if you can shave off 6dB through absorbtion, you'll maintain flat on-axis response.