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horn sub(s) for WE13a horns?
horn sub(s) for WE13a horns?
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Old 17th October 2018, 06:59 AM   #11
weltersys is offline weltersys  United States
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Quote:
Originally Posted by GM View Post
No, all I did was load the details of it from the Badmaieff, Davis book "How to build Speaker Enclosures".
Great book, Alexis B. & Don D. pretty well sorted it out!
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Old 17th October 2018, 04:06 PM   #12
GM is offline GM  United States
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Gees...... my memory's getting so bad, totally forgot it had a drawing.

Indeed, a lot of really good speaker 'system' design info packed in a [mostly] easy to understand format 'buried' in it and a great update to Cohen's 'HiFi Loudspeakers and Enclosures' with of course the Davis's 'Sound System Engineering' being a veritable reference 'bible' for the advanced DIYer, pro designer.

GM
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Old 18th October 2018, 10:55 PM   #13
hollowboy is offline hollowboy  Australia
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Originally Posted by weltersys View Post
Great book
That pic / description seems to be:

a) a light hearted bit of engineering japery
b) a 100% theoretical free space horn (with no ground plane)

The "Artichoke" horn I linked in post 9 seems a bit more sensible (a relative term!), because it uses the ground plane, so has 1/2 the mouth area of the horn in the book.

Indoors, with good placement, you could shrink the mouth down much further.

Eso (who used to post on the High Efficiency Speaker Asylum) took it to the logical limit, by building his bass horns into the room. He had stereo 30Hz bass horns that were only 9' long, because "My subs each use the room essentially as a conical mouth extention".

I can't find / remember the mouth size of Eso's horns, and the pic links are now dead ...but from memory, they were roughly chest high - much smaller than 11' by 11'
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Old 18th October 2018, 11:12 PM   #14
noviygera is offline noviygera  United States
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Default Corner placement

Quote:
Originally Posted by GM View Post
Hmm, a 30 Hz flare, 14 ft axial length expo horn placed between the WE horns in 2pi space requires a ~41.43 ft perimeter mouth to be flat to nearly 30 Hz according to HR, so in retrospect might not fit in the room.

So, at this point, guess we need much more dimensional details to see what can realistically be done and/or what compromises he's willing to accept such as building it as a false [rear] wall in a bi-fold layout to load either a centrally located full height mouth to get a somewhat 0.5 pi loading or at both corners with much smaller full height slot mouths and use DSP to align them.

GM
This 14 ft long horn will be a folded or curled type. Also, I plan to have it by at least two surfaces of the room:
wall+floor or maybe even two walls+floor. In other words, it can be close to a corner.

It may actually face the corner or face the room and be within 2ft of the corner.

So that hopefully clarifies the horns location in the listening room. Will I still need ~41.43 ft perimeter mouth?

Herman
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Old 18th October 2018, 11:25 PM   #15
hollowboy is offline hollowboy  Australia
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Originally Posted by noviygera View Post
will be a folded or curled type [...] It may actually face the corner or face the room and be within 2ft of the corner [...] Will I still need ~41.43 ft perimeter mouth?
If folded + corners is OK, it sounds like you could just chuck a pair of 12pi (or whatever) into the corners, and be done.

For the DIY route, this is me quoting Steve Schell:
I encourage you to pursue horn loading to 20Hz. or below. The sound (and feel) you will get is closer to reality in my experience than any other type of subwoofer.

I designed the "Big Bottom" sub several years ago in an attempt to see how a long, slow flare horn would sound. The length inside the box is 20 feet, the flare rate is 15Hz. A 15" woofer drives the horn through a 67 square inch throat, about a 2:1 compression ratio. I don't know if this is close to optimal, all I know is that it works.

To conceptualize the relationship between a horn and its boundaries, I like to draw them out on graph paper as equivalent square cross sections. It is easy to plot out the horn shape by calculating the square root of the area every foot or two. Plotted this way, a plane wave expansion out of a trihedral corner is equivalent to a conical flare whose walls depart at an angle of 73 degrees, if memory serves. You can combine the proposed horn flare with the room flare and see how close the room serves as a continuation of the horn. In every case I have measured, a trihedral corner expands much too fast to maintain the expansion of the typical 30 or 35Hz. flare exponential horn. It will still help, of course.

The BB sub is built as a roughly 8' by 8' by 2' box which exhausts out one side. It sits along a wall, the mouth ideally aimed at a corner 4' away. The plane wave expansion out of a 90 degree, floor to ceiling corner (8' ceiling) actually plots out as a parabola, but nicely meshes with the 15Hz, flare, coming quite close to maintaining the horn shape out to a total length of 35' or so.

Practically speaking, the room boudaries' contribution to the horn flare is dependent on the building's construction. In my single story wood frame house, the wavelengths below 40Hz. all but ignore the structure and go where they please. My neighbors have no doubt noticed this. I would say it is best to make the horn as long as you can, use 3/4" plywood for the enclosure, and use as low a flare rate as you can manage. Even at 20', my design is only about one third of a wavelength at 20Hz., and about one wavelength at the upper limit of 80Hz.
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Old 20th October 2018, 05:42 AM   #16
GM is offline GM  United States
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Quote:
Originally Posted by hollowboy View Post
That pic / description seems to be:

a) a light hearted bit of engineering japery
b) a 100% theoretical free space horn (with no ground plane)
Not really AFAIK, I've been led to believe it was a real WE/Lansing horn, but Don Davis is still around and probably knows for sure, so anybody here on speaking terms with him? Art?

Regardless, you imply the pioneers didn't make big 'free' space horns, but they did and propped them up like this ~20 Hz, 1" throat Magnavox horn and there were other smaller ones too, but my Google link no longer displays what I originally found long ago, so for now this is all I've got: File:Large horn loudspeaker.jpg - Wikimedia Commons

Note that I posted this 'no compromise' horn as a proper period correct bass horn with the kind of comparable 'no compromise' performance as the WE13A, i.e. max efficiency/BW, but of course it can be shrunk to a much smaller size with increasing number of boundaries, just each added boundary reduces the quality of its performance in relation to the WE13A.

Frankly, without being able to compare the full size to one heavily truncated in room, I doubt anyone would notice due to how bad the room modifies a speaker's [mid] bass response. Still, if one has the space, budget, etc., to drive a full size, wide range horn system to ear splitting levels at low distortion with a single 300B tube, why compromise?

Anyway, I see he's given us more details, so will address the'shrinking' of it or some other alignment as time permits if he chooses to pursue it.

GM
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Old 20th October 2018, 06:45 AM   #17
freddi is offline freddi  United States
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horn sub(s) for WE13a horns?
GM - nice response - but at 8000+ liters internal airspace, that sub might take some plywood.

could one cheat and use a horn to ~50-60Hz then tapped pipe or pipehorns for the lower octave? (BFM puts a lot of path in a given bulk)

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Old 20th October 2018, 07:06 AM   #18
GM is offline GM  United States
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Yeah, it would be a costly sucker for sure, though wouldn't surprise me if it was less than a pair of pristine WE13As.

Well, the pioneers were happy with truncated 70 Hz horns bass tuned to 35 Hz, so figure 2 octaves for the sub = 17.5 Hz works for all but some special effects recordings and movie soundtracks, which require 40 Hz horns bass tuned to 20 Hz.

That said, DSL's DTS15 comes close to the 'magic' <10 Hz goal and many have XO'd them at 80 Hz/4th, so a bit bigger version theoretically could do it with a 60 Hz horn.

GM
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Old 21st October 2018, 09:08 PM   #19
freddi is offline freddi  United States
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horn sub(s) for WE13a horns?
I think ol' banned BFM might (?) have something appropriate. Here's a $27 8" driver in a Table Tuba. Something with a larger driver could be ok.

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or

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Last edited by freddi; 21st October 2018 at 09:14 PM.
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Old 22nd October 2018, 07:30 PM   #20
Zwiller is offline Zwiller  United States
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I vote artichoke horn. Probably would fold it somehow. Aesthetics match the WE too.



TH50 might work. $300 TH-50 Knockoff
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