ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1] 2 3   Go Down

Author Topic: Line Array HF Throats  (Read 16286 times)

Jim McKeveny

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1087
Line Array HF Throats
« on: June 15, 2011, 08:40:32 am »

I have been fortunate enough to hear, listen, and disassemble many prosound cabinets over the years. When the line-array concept first reared, terrific attention was paid to the geometry required to transform the circular throat inlet from compression drivers into a rectangular exit for proper L/A form. Patents apps flew...

Up to that time, the circle-to-slot transform was commonly done somewhat empirically to produce diffraction slit loading into constant-directivity horns. As line array tech has evolved I see alot of much simpler, yet fine sounding HF throat areas out there.

My question: How different are the newer mathematically "correct" L/A throat guides - in terms of high and low frequency extension, distortion, and efficiency vs. ye olde diffraction slit?

Talking about throat only, not the final flare.
Logged

chuck clark

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 348
Re: Line Array HF Throats
« Reply #1 on: June 16, 2011, 05:35:21 pm »

Yeah, I found it interesting that Peavey -holders of "quadratic" throat  patents, chose to go with ribbon drivers (which have the desired cylindrical output) for the top end in their line arrays. Things that make you go Hmmm?!
Any engineers out there, that can put some basic concepts into relatively simple terms without spilling any trade secrets?
Hope so!
Chuck
Logged

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1651
Re: Line Array HF Throats
« Reply #2 on: June 16, 2011, 08:09:39 pm »

I have been fortunate enough to hear, listen, and disassemble many prosound cabinets over the years. When the line-array concept first reared, terrific attention was paid to the geometry required to transform the circular throat inlet from compression drivers into a rectangular exit for proper L/A form. Patents apps flew...

Up to that time, the circle-to-slot transform was commonly done somewhat empirically to produce diffraction slit loading into constant-directivity horns. As line array tech has evolved I see alot of much simpler, yet fine sounding HF throat areas out there.

My question: How different are the newer mathematically "correct" L/A throat guides - in terms of high and low frequency extension, distortion, and efficiency vs. ye olde diffraction slit?

Talking about throat only, not the final flare.
There are a number of different approaches in line array throats, but generally speaking they put less of a "squeeze" than the older style diffraction slit throats used on many "constant directivity" horns.

The squeeze was not a good thing, technically speaking it caused a kind of "shussy" sound.

High and low frequency extension, distortion, and efficiency are still largely dependent on the driver choice.
Drivers have improved HF and distortion, but no most line arrays use the HF driver from somewhere in the 1K range all the way up, rather than splitting that range in two. Net result is distortion is not improved a lot, but who cares about distortion ;^)?
Logged

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1651
Re: Line Array HF Throats
« Reply #3 on: June 16, 2011, 08:37:49 pm »

Yeah, I found it interesting that Peavey -holders of "quadratic" throat  patents, chose to go with ribbon drivers (which have the desired cylindrical output) for the top end in their line arrays. Things that make you go Hmmm?!
Any engineers out there, that can put some basic concepts into relatively simple terms without spilling any trade secrets?
Hope so!
Chuck
The "quadratic" throat works well for single horns with fairly wide vertical dispersion. I have recently built several, and they do sound better than the "pinched throat" approach, but require a longer horn to have the same vertical pattern control.

Line arrays require the high frequency horn to have a very narrow vertical dispersion, and an output that is theoretically like a wedge, or a cylinder. This requires path length compensation, some wiggles or other shapes need to be placed in the throat path so the top, bottom and center all arrive in phase as an output that (hopefully)  does not cause interference patterns with other units above and below.

DSL uses a different approach to do the same, the Paraline device, used in the VTC line arrays and various DSL horns with Biblical names. It is less than an inch deep, many "conventional" line array throats  are as much as 10 times that length.

Ribbon drivers eliminate the complexity of the HF throat, and are even shorter in depth than the Paraline, but are low efficiency, and need a fairly high crossover point because they have very limited excursion capabilities.
Those problems limit ribbons to a fairly "short throw"  compared to compression drivers.

Art Welter
Logged

Iain.Macdonald

  • Full Member
  • ***
  • Offline Offline
  • Posts: 213
Re: Line Array HF Throats
« Reply #4 on: June 18, 2011, 11:00:05 am »


DSL uses a different approach to do the same, the Paraline device, used in the VTC line arrays and various DSL horns with Biblical names. It is less than an inch deep, many "conventional" line array throats  are as much as 10 times that length.

Art Welter

To illustrate what Art is saying.
Logged

Iain.Macdonald

  • Full Member
  • ***
  • Offline Offline
  • Posts: 213
Re: Line Array HF Throats
« Reply #5 on: June 18, 2011, 12:28:41 pm »


Ribbon drivers eliminate the complexity of the HF throat, and are even shorter in depth than the Paraline, but are low efficiency, and need a fairly high crossover point because they have very limited excursion capabilities.
Those problems limit ribbons to a fairly "short throw"  compared to compression drivers.


Art Welter

This might change your mind.

Logged

Jim McKeveny

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1087
Re: Line Array HF Throats
« Reply #6 on: June 20, 2011, 07:49:32 am »

If I am seeing this properly, compression drivers have an internal correction for the "path length problem" - i.e. phase plug - before the driver exit....where there is yet another correction for the "PLP" in the circle-to-slit conversion. Cannot bode well for absolute signal integrity (but is still quite usable).

Ribbons seem an obvious solution - a direct drive of the waveguide entrance w/o coercive geometry - but despite improved thermal capacities, I cannot imagine they have a sustained high power w/ good bandwith.

The grail quest continues...
« Last Edit: June 20, 2011, 07:52:13 am by Jim McKeveny »
Logged

Niels Janssen

  • Newbie
  • *
  • Offline Offline
  • Posts: 4
Re: Line Array HF Throats
« Reply #7 on: June 21, 2011, 05:05:38 am »

This might change your mind.
Please note these are from Alcons Audio (www.alconsaudio.com).
Logged

Iain.Macdonald

  • Full Member
  • ***
  • Offline Offline
  • Posts: 213
Re: Line Array HF Throats
« Reply #8 on: June 21, 2011, 08:04:52 am »

Please note these are from Alcons Audio (www.alconsaudio.com).

Hi,

Niels, the forum rules requires that you put your real name in the name field of your profile, not your user name. You should also put the company name in/after your signature.

Recovered from the show yet?

Iain.

Logged

Iain.Macdonald

  • Full Member
  • ***
  • Offline Offline
  • Posts: 213
Re: Line Array HF Throats
« Reply #9 on: June 21, 2011, 08:17:32 am »

If I am seeing this properly, compression drivers have an internal correction for the "path length problem" - i.e. phase plug - before the driver exit....where there is yet another correction for the "PLP" in the circle-to-slit conversion. Cannot bode well for absolute signal integrity (but is still quite usable).

Ribbons seem an obvious solution - a direct drive of the waveguide entrance w/o coercive geometry - but despite improved thermal capacities, I cannot imagine they have a sustained high power w/ good bandwith.

The grail quest continues...

Actually quite the opposite. The larger diaphragm area allows a better thermal path. If you check the alcons site, you will see that the power rating is for a time period twice that normally quoted for compression drivers.

Iain.
Logged

ProSoundWeb Community

Re: Line Array HF Throats
« Reply #9 on: June 21, 2011, 08:17:32 am »


Pages: [1] 2 3   Go Up
 



Page created in 0.051 seconds with 25 queries.