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#1 of 42 Mark_J_H_Jr

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Posted February 26 2003 - 06:49 AM

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
mjh

#2 of 42 Guest_Anthony_Gomez_*

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Posted February 26 2003 - 07:46 AM

this should more than overflow most peoples heads with info Posted Image
http://www.prism.gat...29u/LinusWP.pdf

#3 of 42 Mark_J_H_Jr

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Posted April 10 2003 - 05:00 AM

I have looked through the links above and found Jim Myake's site as well. Still interested in this type of speaker.

Are there and detailed construction and crossover plans available?

What is the consensus of this speaker design? Do folks like it or is the size too intimidating?
mjh

#4 of 42 Greg Monfort

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Posted April 10 2003 - 07:43 AM

Ah, a local yokel. Posted Image They have their strong/weak points, like any design. The size doesn't bother me, but my hands wouldn't like making all those holes/rebates and doing all that tedious wiring. Posted Image Discrete lines work best in a VERY large venue where it can act more as a point source over a greater distance.

In a home HIFI app., they must either be power tapered to keep comb filtering low enough not to audibly degrade imaging/soundstaging or curved at the radius of the listening distance, severely restricting the 'sweet spot'. Also, IMO dipole versions with rear diffusors are preferred since they don't interact with the room much. Last, but not least, if low distortion at ~'live' SPLs are a goal then fairly high quality drivers are required, at least in the mid/midbass BW, jacking up the cost considerably.

Last year several of us had the larger ATLA DIY2002 room available to us the night before, and JG's Linus arrays began audibly distorting on a variety of selections before the Babbs 6" long throw fullrange Lorelei speakers did as the few drivers carrying both midbass/mids rapidly went into AMD. Actually, excepting organ music, the Babbs never did because we kept hard clipping the amp, but that's another story. Posted Image In all fairness though, all the Linus components cost considerably less than just the Babbs two hi-tech space age materials drivers.

Anyway, if I were to go this route it would have to be with high quality drivers and at least a three way plus sub system so the components could be small enough to allow each segment of the array to act more as a true line source, IOW sufficient comb filtering to be perceived as a singularity.

The cost would be high enough though that I'll gladly take the hit on living room real estate and stick to compression horns and HE LF drivers in refrigerator sized cabs to feed my addiction to hi def wide dynamic range.

As always though, YMMV. Posted Image

GM
Loud Is Beautiful, If It's Clean

#5 of 42 David Gadd

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Posted April 10 2003 - 11:24 AM

Greg:
Actually, I see the efficiency of the line array as a major selling point for me. In my room, the Linus Array would be equivalent to a 100dB point source. Typical kits would need 4 to 20 times the power (87-94dB point sources seem typical). I'm not in the market for 300 to 1500 Watt amps to replace my 75W/ch HK receiver if a speaker upgrade will do more good. I'm preaching to the choir on efficiency with you, though. Horns and 15" woofers would be an even tougher sell with my wife than a line array.

Questions on your experiences with the Linus Array, please:

1) IIRC, the Linus was tuned to 50Hz. Was the distortion you heard related to bass below tuning? (The Linus II is sealed.) How loud are we talking about and in how large a room?

2) I have a sub I'm satisfied with (i.e., its the best component in my current system Posted Image ), if I high pass a Linus (or equivalent) at 60 Hz (at least 2nd and probably 4th order), would my distortion limited sound levels be adequate (think 105 dB at 4 meters, i.e. amp limited)?

3) What if I run a Linus II full range with a sub low passed about 60-70Hz. 105dB at 4 meters clean?

Also, are my rules of thumb correct (anyone)? With the whole power tapering issue I'm having a hard time comparing an array to my current commercial speakers (twin 5 1/2 mid/basses).
-- 6 dB increase in SPL requires 2x the displacement
-- one octave lower requires 4x the displacement
-- 3 dB/meter falloff for line sources
-- 6 dB/meter falloff for point sources

#6 of 42 Dan Wesnor

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Posted April 10 2003 - 12:15 PM

For the Linus array, your best bet is to either ask questions at Madisound's forum (http://www.madisound...bin/discuss.cgi) or to e-mail Rick Craig directly (www.selahaudio.com). Rick is the "keeper" of the kit. I believe Rick donates all the profits from his kits to a charity, so he keeps the designs close-hold to prevent the charity losing money.

#7 of 42 Danny Richie

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Posted April 10 2003 - 02:20 PM

Dan,

There were some kits that he offered as published designs that one could go purchase the parts for and build.

In exchange he requested that I donation to be made to his charity as an appreciation for his design work.

But any money that you give to Rick goes to Rick. He does not give away the money that he makes to charity.

Mark,

I have sold four pairs of Alpha LS's in Atlanta GA. If you want to hear a good pair of line sources it can be arranged.

#8 of 42 Dan Wesnor

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Posted April 11 2003 - 09:33 AM

He no longer shows any sort of plans on his site. Just pictures and measurements. And there no longer any mention of the donations, either. Used to be he requested a donation, but you had to mail him for designs. You're right, the donation was voluntary.

#9 of 42 Greg Monfort

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Posted April 11 2003 - 01:19 PM

>Greg:
Actually, I see the efficiency of the line array as a major selling point for me. In my room, the Linus Array would be equivalent to a 100dB point source.
====
Hmm..... I haven't bothered to research the LA since it's mid/midbass drivers don't appeal to me and the ones JG brought to the meet had too short a HF ribbon array, IMO seriously compromising the overall performance. He said more were going to be added though, four, IIRC.
====
> Typical kits would need 4 to 20 times the power (87-94dB point sources seem typical). I'm not in the market for 300 to 1500 Watt amps to replace my 75W/ch HK receiver if a speaker upgrade will do more good. I'm preaching to the choir on efficiency with you, though. Horns and 15" woofers would be an even tougher sell with my wife than a line array.
====
Understood. They didn't sound effortless enough to me to be 100dB, maybe 94-95dB, so without measuring them.....
====
>Questions on your experiences with the Linus Array, please:

1) IIRC, the Linus was tuned to 50Hz. Was the distortion you heard related to bass below tuning?
====
It definitely had some, but on a couple of tracks with big transients I could plainly see the central mids moving far enough to distort their surrounds from ~13ft away and my vision sucks, so got up and looked at them up close and personal to confirm it.

At this point JG just shrugged, rhetorically asking something to the effect of "what do you expect from a $(can't remember now) driver?"

Don't get me wrong, they were quite impressive for what they are and would be much better with a longer tweeter array, just too many tradeoffs for me as presented. With higher resolution mid.midbass drivers and LF line I'm sure it would be a different story, not to mention much larger/expensive.

JG has written a new line array White Paper that he asked me to review and it's a lot more informative without resorting to plowing through referenced AES papers than his previous White Paper, though he's still quoting free space theory to make them seem much more efficient in a typical home HIFI room than other designs.
====
> (The Linus II is sealed.) How loud are we talking about and in how large a room?
====
No measurements, and the room is all concrete with some severe acoustic problems so it sounded louder overall than the speakers were putting out, but based on the measured efficiency of the Loreleis and the amp's rating, the LA's were sounding pretty rough with ~105dB peaks/listening position in the 300-500Hz BW where the most power is required for most music.

WRT room size, I'd have to check with the hotel since they're a bit odd shaped, but I'm guessing ~1000-1200ft^2 with the speakers ~1/3 into the room, spaced ~10ft apart. Maybe Pat, Chris, or one of the others who was there has a better handle on the room size than me.
====
>2) I have a sub I'm satisfied with (i.e., its the best component in my current system ), if I high pass a Linus (or equivalent) at 60 Hz (at least 2nd and probably 4th order), would my distortion limited sound levels be adequate (think 105 dB at 4 meters, i.e. amp limited)?
====
Probably, they had a pretty stout midbass, about like a prosound 10", and would be for most older folks, etc., but I'm not you and haven't been in your room. Posted Image It doesn't work for me though since I like to occasionally listen at ~'live' levels at low distortion to other than acoustic music.
====
>3) What if I run a Linus II full range with a sub low passed about 60-70Hz. 105dB at 4 meters clean?
====
Again, without measurements I can't say, but I'd be very surprised if the ones I auditioned could hit 105dB/4m cleanly (by my standards) below ~400-500Hz and I'm skeptical about the implied ~100dB/m in-room eff..

Still, I think it's safe to say that in overall performance they will blow the doors off the majority of consumer speakers, and many DIY designs, regardless of cost, so you could do a lot worse IMO. If you tired of their, hmm.... interesting sonics, I imagine you could recoup much of your $$ investment.

That said, I recommend reading his new WP and either checking out his new LA designs he's showing at Lima this weekend, or 'roll yer own' based on the WP.
====
>Also, are my rules of thumb correct (anyone)? With the whole power tapering issue I'm having a hard time comparing an array to my current commercial speakers (twin 5 1/2 mid/basses).
-- 6 dB increase in SPL requires 2x the displacement
====
2x = 3dB, assuming they are acoustically close, then you have to double the power to get the other 3dB, assuming a parallel connection.

You'll have to measure a speaker at 2.83V/1m and at the listening position to find out how much they're rolling off in-room/listening position. If it's like most rooms it will be frequency dependent. 1/3octave resolution is sufficient.
====
-- one octave lower requires 4x the displacement
====
Bingo.
====
-- 3 dB/meter falloff for line sources
-- 6 dB/meter falloff for point sources
====
These would be for every doubling of distance, so 3 or 6dB/1m, 6 or 12dB/2m, etc., and this is in free space, though a horn is a point source and falls at 3dB octave also, though not for as far away as a true line. Depending on the BW, mine fall off at 2-4dB whereas a line array would be in its nearfield for most/all of its BW so its response would be mostly room independent, falling at ~ the same rate as the horns.

GM
Loud Is Beautiful, If It's Clean

#10 of 42 David Gadd

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Posted April 14 2003 - 09:09 AM

Thanks Greg. Posted Image

#11 of 42 Bill Fagal

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Posted April 15 2003 - 01:31 AM

Had a fun time at Lima!

I made it a point to listen to JG's arrays, as I have always had interest in arrays (though I soon came to recognize their compromises after I built my first pair).

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. I'm picturing large, horizontal wedges that protrude a few inches between drivers and occlude all but a horizontal center stripe of each cone. Ideally, at higher frequencies, the foam would absorb most of the vertically off-axis sound, effecively narrowing vertical dispersion to minimize beam interaction. The foam would become progressively more transparent to the lower frequencies, amounting to baffle-step compensation.

Also, I've wondered about layering felt over perhaps the top and bottom third of an array's drivers, starting with one thin layer and progressively thickening it toward the ends. This would give you a frequency-dependant power taper without the complexity and phase effects of doing the taper with multiamping and coils.

I'm also thinking of how absorbtive materials could improve the characteristics of single drivers, but that's another story Posted Image.

GM, I seem to recall seeing some FR speakers you built making pretty heavy use of felt over portions of the cones. What were your thoughts in that case?

Bill

#12 of 42 Rick Craig

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Posted April 15 2003 - 05:03 AM

To clarify things:


I do still provide some kit designs for no charge. I only ask for a donation to my charity, FSMA. 100% of the donation is sent to them; in fact, I prefer a check made out to FSMA so that I can forward it to the organization. My wife and I lost two children to Spinal Muscular Atrophy. You can visit www.fsma.org to get additional information.

#13 of 42 Danny Richie

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Posted April 15 2003 - 06:05 AM

Thank you Rick for that Clarification.

#14 of 42 Greg Monfort

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Posted April 15 2003 - 08:25 AM

>Had a fun time at Lima!
====
Great! I was offered a ride up, but just couldn't generate enough enthusiam for a ~long road trip.
====
>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. I'm picturing large, horizontal wedges that protrude a few inches between drivers and occlude all but a horizontal center stripe of each cone. Ideally, at higher frequencies, the foam would absorb most of the vertically off-axis sound, effecively narrowing vertical dispersion to minimize beam interaction.
====
This works OK with two or three drivers in a nearfield situation, but not a long line's portion of its BW that's 'feeling' a far field.
====
> The foam would become progressively more transparent to the lower frequencies, amounting to baffle-step compensation. ====
When I first got on the net in '96 there was a company hawking a line using a tapered block of foam to do exactly this. From the side it looked like a curved array, but wasn't. No idea what, or number of drivers were used, but it was tall and had no sub. I lost the link in my first 'crash' and have never seen one again, so either it didn't sound good, no one was interested at the time, too expensive, or.....
====
>Also, I've wondered about layering felt over perhaps the top and bottom third of an array's drivers, starting with one thin layer and progressively thickening it toward the ends. This would give you a frequency-dependant power taper without the complexity and phase effects of doing the taper with multiamping and coils.
====
If I were to do another line, this is the way I would attack the problem rather than with XOs. 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. Posted Image

FWIW, it was polyfil, though I'll use felt, fiberglass, foam, cloth, a mix of them, whatever gets the job done.

GM
Loud Is Beautiful, If It's Clean

#15 of 42 Bill Fagal

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Posted April 15 2003 - 08:48 AM

Quote:
This works OK with two or three drivers in a nearfield situation, but not a long line's portion of its BW that's 'feeling' a far field.


Sorry, I'm not understanding...Can you expand on this "feeling" Posted Image

Quote:
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

#16 of 42 Greg Monfort

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Posted April 15 2003 - 09:24 AM

Acoustic impedance over distance.

GM
Loud Is Beautiful, If It's Clean

#17 of 42 Hank Frankenberg

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Posted April 16 2003 - 12:37 AM

Bill - interesting, and Jon uses quite a bit of felt around his tweets. 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? Sounds good and if it works, then of course it's better than extra crossover components.

#18 of 42 Bill Fagal

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Posted April 16 2003 - 02:03 AM

Quote:
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.

#19 of 42 Danny Richie

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Posted April 17 2003 - 04:27 AM

Quote:
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.

#20 of 42 Bill Fagal

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Posted April 17 2003 - 07:03 AM

Incidentally, for all of you who want to model array interactions, here's a slick little spreadsheet with a nice 3D visualizer.

Quote:
This would do little to minimize comb filtering effects.


You may be right and I'm willing to learn from those who know, but let me see if I can explain what I think this would accomplish.

At higher frequencies, an array's individual driver's beams begin to narrow and decouple, but they also throw strong off-axis lobes which can become additive along the vertical axis of an array. These strong up & down lobes get a quick bounce from the floor/ceiling, and reduce on-axis clarity.

So what I'd like to happen is for those lobes to be largely absorbed in the vertical dimension before they add together, bounce, and spear you in the ear. By absorbing as much vertically divergent radiation as practically possible, it seems to me that you take a step closer to the array ideal where each driver shades its own vertical segment of space.

If I'm all wet here, I stand ready to be corrected.

Quote:
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.


True, but I'm suggesting felting OVER (not around) drivers to roll on a frequency-dependant power taper that progressively biases the array toward the middle with increased frequency to minimize the effects of the differing distances. This is a seperate idea from the foam wedges, so I hope I didn't create confusion by introducing both ideas at once.

Again, it's just a theory I have that's open to correction...

Quote:
Comb filtering effects are the same on a long RD ribbon or New Form ribbon as well and it is a long single driver.


Yup. As you get nearer to a perfect line source, it models like an array with more and tinier drivers (That spreadsheet above is fun to try this on.)

Quote:
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.


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