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Old 8th May 2008, 07:26 PM   #1
RyanC is offline RyanC  United States
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Default Horn Loaded Neo8s

Hi All-

A while ago I heard a pair of B&G Neo8's in tratrix horns, and while there were some things I didn't like about the system (mainly the directionality he had going on; too wide horizontally, too narrow vertically) I was awestruck. Lisening to sweep tests had the lowest amount of distortion I've ever seen/heard. And the imaging and dynamics were fantastic. These completely distroyed my system with audax hm100z0's. And after I accidentally destroyed one of the ol HM's (in a puff of smoke), I went back to the drawing board.

So I searched on here a while ago and found a guy whe used 4 Neo8 drivers per side in a 70x30 conical horn. This appeals to me as I would rather have even HF response when standing and sitting (studio control room). He said with the loading he could get 200hz to 20k minimal EQ and make it fairly flat.

Well I tried it. I wanted a slightly narrower H so I threw together some MDF horns at 50x30 (12 inch depth) and let me tell you they play loud and clean down to 200 no problem. And more suprizingly they go all the way up to 20k no problem. Only a small amount of wide band LF cut/shelving is required to attain a very respectable response, and a small notch at 12k is good for that little spike as well.

So here is my issue, and the reason I would like some advice; I know very little about horns or line source behavior and I've been trying to research it more, but I'm getting stuck.

Mine are 2 neo 8's per side; and while I am very happy with the sound; I really need a little more vertical directionality (sitting, standing).

So If I go to 4 neo8's (about 31" of vertical radiating area) per side how far into the room will they have line source behavior and what are the ramifications of that? Or does the Horn loading nullify the line source behavior?

And also, has anyone tried horn loading the 40" or bigger B&G drivers?

I'll take some pics when I head over to the studio in a minute.

Thanks-

Ryan
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Old 8th May 2008, 07:49 PM   #2
ScottG is offline ScottG  United States
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Default Re: Horn Loaded Neo8s


I've contemplated this for some time now.. in fact its the primary reason I purchased some, I just seem to be to lazy to get of my @ss and put in the work required to "get it right".

Beyond the stand-up sit down problem, what was wrong with the original set-up? IMO wide horizontally is a very good thing, what did you dislike about that? Also, was it a "compound horn".. i.e. was there a horn on both sides of the driver for a dipole horn?

(sorry about all the questions, but the only one I've seen to do something like this was Fcserei.)
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Old 8th May 2008, 08:12 PM   #3
ScottG is offline ScottG  United States
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Oh yeah, your questions..

For line source vs. point source character look at page 8 of Dr. Griffin's Line Array Paper.

If the line is just under a meter in length then the line should behave as a line source to about 1.5 kHz within a two meter distance. Moreover as you get closer that freq. will decrease, and of course as you get further away that freq. will increase.

Practically speaking that means at increased distances you higher freq. response will be elevated in comparison to the average. (line sources decrease in output at about -3db a meter and point sources decrease in output at about -6db a meter - not factoring any additional gain.) A variable shelving filter would work well if you found it objectionable.

Your current version will likely be a bit elevated in freq. above 7 kHz at 2 meters, and about 10 kHz at 3 meters.

I believe the Carver Corporation used the longer lines in a semi-horn loaded line (may not have been the BG planars specifically though), it seemed to be more of a upper mid wave-guide though.
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Old 8th May 2008, 08:34 PM   #4
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Default Re: Horn Loaded Neo8s

Quote:
Originally posted by RyanC
Hi All-



Well I tried it. I wanted a slightly narrower H so I threw together some MDF horns at 50x30 (12 inch depth) and let me tell you they play loud and clean down to 200 no problem. And more suprizingly they go all the way up to 20k no problem. Only a small amount of wide band LF cut/shelving is required to attain a very respectable response, and a small notch at 12k is good for that little spike as well.
Interesting. I tried this using some of the Monsoon planar drivers which are similar in principle to the BG Neo's. In my case, I used a flare that approximated the Oblate Spheroid profile. Results were great, although they rolled off severely well below 15k, which was just a bit lower than I was willing to live with.

Quote:


And also, has anyone tried horn loading the 40" or bigger B&G drivers?

I've thought about it, and if I had the room I would try it. If you are actually in Denver as your profile states, PM/email me. I have a set of the 60" Carver ribbons that would be suitable as a project/prototype that are taking up space in my garage. (I'm pretty sure they still work :-)
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Old 8th May 2008, 10:23 PM   #5
RyanC is offline RyanC  United States
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Hey DWK-

I'm on 38th and federal, born and raised in the ol mile high city. . .

Scott thanks, I'll read that paper, but that makes sense with what I'm hearing in the room. . .

Also I know that traditional wisdom is that a wide spray is better, but to my ears it starts sounding like the polarity is reversed on something. . . especially in a narrower room, it just doesn't make that much sense to me to put 100 degree horns so that 30 percent of sound goes right into the wall. Also My Room isnt wide enough to have a two person wide sweet spot, so I'm tryinig to make the sweet spot long (eg one person in front of another) So far so good. . .

You are an recording engineer also right?

Here is a pic
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Old 9th May 2008, 02:34 AM   #6
ScottG is offline ScottG  United States
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Just an "enthusiast".

It looks a lot like the CD that Fcserei described! Nice!

By "polarity reversed" do you mean that everything sounds "farther away" or "more recessed"? And/Or are you talking about imaging being less specific/apparent? (..or something else all together?)

With wide dispersion what I found is that in most instances the soundstage expands, and it is NOT due to side wall reflections. (..you can try it with and without panel absorbers on the side walls for the distinction.) IMO it has more to due with the direct radiation from the driver/horn.

Note though that while I do like wide dispersion designs I also prefer to be closer to the speaker than the speaker is to the side wall (intelligibility and tracking goes up). Basically 2 meters from the speaker and more than 2 meters from the loudspeaker to the nearest wall, seated pretty close to the rooms back wall (..speakers about 7 feet apart with no "toe-in"). If the room is still rectangular you can sometimes "flip" listening position to get more width, but less depth (..of course it also sounds like you have other limitations that would nix that).

Anyway, please keep us updated on your progress - it looks like you are at the start of something far better than the "same ol' same ol' ".
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Old 9th May 2008, 04:48 AM   #7
RyanC is offline RyanC  United States
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Hey Scott-

Yeah exactly, neither the room I'm in or the one I heard the tractrix loaded BGs was more than 12ft wide. Even down the road I probably wont be in a position to have a control room bigger than around 3000 cu feet. I agree completely WRT to wide rooms, but I think this is a better listening situation and potentially worse for mixing (I've only ever worked in one big mixing room like that and I found it a little bit confusing).

The first ones I heard had some serious amps, SET with each discreet component placed into grooves of machined 1" plate aluminum. The 15" BR also had custom machined 6" Alu phase plugs (over the 4" VC) and doped cones to lower the Res Freq. Dont trip and fall on those!

I have em toed in, because they are only about 6 inches away from the walls now. So they are in to the point that the outside of the horn is parrallel with the walls.

By polarity reversed, I mean it sounds almost as if one of the horns was wired reverse polarity. Not that it actually is, but if I take a mix I did, and I know how much out of phase information is in the mix, it sounds as if there is WAY more. This can be euphonic (depending on the origional mix) but isn't really what I want for monitors. Plus the really big sound stage can make you want to slather a bit too much room mic/reverb for a mix that still needs to hold up over the radio.

I lowered my horns a bit and I had them high and angeld down. They are much more consistant sounding w/o the angle and lower so thats good. Also I think the drivers are breaking in a bit.

For the rest I'm thinking BR with a 2226h, tad 1603, or Beyma 15p1000

But I'm toying with the idea of an OB mid bass, and a true sub. Hiding in some dark corner of my soul I find myslef lusting after that 15" audiopulse woofer.

Two questions; I happen to have access to 1/2" plate aluminum for cheapish, would it be good to make the horn out of something harder than wood (alu)? Obviously they would need to be damped to minimize the ring (I'm thinking fill the backside with concrete and cellulose mixed in).

The other: There does not appear to be much vertical dispersion from the drivers themselves. I'm wondering if really only the side flare is necessary, or would this cause it not to function as a horn, say if it had a parrallel bottom and an open top? I'm guessing that this would defeat the purpose, but I'm trying to understand horns better.

Man these things sound good, right now I'm thinking about asking Dianna Krall if she wants to marry me, unfortunately when I open my eyes I see this-
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Old 9th May 2008, 04:59 AM   #8
RyanC is offline RyanC  United States
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Oh and DWK-

Let me know if those are working. . . I dont think I'd really have space for 60 inchers, but I'm thinking about the 40s pretty hard right now. And it's pretty easy to slap these things together, mine are a little slopy, but I like to get the hang of it before. The carvers are a true ribbon right? Ive never heard those, always wanted to though. . .

Does anyone know are they essentially the same (the neos and the big ones)?

Thanks guys-
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Old 9th May 2008, 06:42 AM   #9
ScottG is offline ScottG  United States
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Quote:
Originally posted by RyanC


For the rest I'm thinking BR with a 2226h, tad 1603, or Beyma 15p1000

But I'm toying with the idea of an OB mid bass, and a true sub. Hiding in some dark corner of my soul I find myslef lusting after that 15" audiopulse woofer.

Two questions; I happen to have access to 1/2" plate aluminum for cheapish, would it be good to make the horn out of something harder than wood (alu)? Obviously they would need to be damped to minimize the ring (I'm thinking fill the backside with concrete and cellulose mixed in).

The other: There does not appear to be much vertical dispersion from the drivers themselves. I'm wondering if really only the side flare is necessary, or would this cause it not to function as a horn, say if it had a parrallel bottom and an open top? I'm guessing that this would defeat the purpose, but I'm trying to understand horns better.

Man these things sound good, right now I'm thinking about asking Dianna Krall if she wants to marry me, unfortunately when I open my eyes I see this-
Its not that bad.. a little darth vader meets home depot'ish.

IMO horns are best made from cement - rigid and non resonant. Thats also the case for baffles, and it makes a BIG difference with baffles. The only real problem is cracking and weight.. and some polymer additive can pretty much negate the first problem.

I would not suggest aluminum, but end-cut and blocked hardwood (like cutting boards) can be excellent. Aluminum might be excellent though for the connection to the horn and the initial bit of flair in that with some decent machining you can get much more precise with it.

For your current setup I don't think you can go "open baffle" - too close to the corner/walls.

For your midbass - well thats largely depends on how it integrates with the room, it would be a really tough call to say one thing would be better than another ..BUT a wave guide for the midbass driver might help considerably (..and match better with your Neo 8 dispersion). Supravox 215 GMF.. low mass, good force, high eff. and a fairly low sd for keeping the waveguide size down.

There are plenty examples of limited to no-vertical flair horns, try it and see if you like it. To me it seems as if there is some vertical dispersion from the drivers (not a lot, but some). In a two driver config. like you have you may well be encountering some higher freq. "combing" between the two drivers that would likely lessen the perception of clarity. You *could* try a tapering waveguide (wedge) between the two drivers and see if that does anything (though it may introduce more problems than it might fix).

You know, Horn response *may* have calculations for a non-standard driver like the Neo 8.. you could always give that a look-see to get a better handle on what works and what doesn't before prototyping.

In any event - good luck, its always nice to hear someone taking a trip down an alternative path.
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Old 9th May 2008, 08:48 PM   #10
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To damp your 1/2" Aluminum plates I recommend constrained layer damping; perhaps layering the Al w/ 1/4" or so steel plates and they would be bonded together with self adhesive elastomeric vinyl damping sheets.
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