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Old 17th August 2012, 01:51 AM   #11
GM is offline GM  United States
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Quote:
Originally Posted by djlivex View Post
Whats eigenmodes??? The 825/828 is bigger heavier??? Couldn't I just add an angled piece on the bottom horn mouth from the throat??? Thanks GM!
Hmm, didn't see this...........

Standing waves. Yes, but once chopped down isn't a lot bigger/heavier and IMNSHO it sounds enough better overall to justify the extra labor, etc.. Not really as it changes the horn's HF performance, though it might work out well enough for when using a smaller driver. Use HornResp to find out.

A belated you're welcome!

GM
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Old 17th August 2012, 01:53 AM   #12
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I just tried modeling something like this in hornresp with an Eminence Delta-12A, got about 102 db/w/m, 2pi, 90 to 700 hz from a 1800 cm^2 mouth cone horn with 80 hz tuned box. Interesting stuff.....
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Old 17th August 2012, 06:33 AM   #13
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I'll look at it again GM, what do you think about a phase plug simple cone elongated like meyer sound? Thanls!
Oh by the way turbodawg that sounds promising, can it be done straight sided horn mouth or curved sounds better?
Eminence Delta that's great that driver cost peanuts!
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Old 17th August 2012, 01:46 PM   #14
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The designs are 1:1 compression ratio, so if you don't need a phase plug for the driver on a flat baffle, I see no need for it in a 1:1 CR horn. For sure, Altec, JBL, et al historically didn't feel the need.

GM
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Old 17th August 2012, 02:07 PM   #15
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Originally Posted by djlivex View Post
I'll look at it again GM, what do you think about a phase plug simple cone elongated like meyer sound? Thanls!
Oh by the way turbodawg that sounds promising, can it be done straight sided horn mouth or curved sounds better?
Eminence Delta that's great that driver cost peanuts!
Well, I'm pretty new to horn resp, but things look promising so far. I'm looking for a cheap PA mid, so it be great to be able to build this with a simplified design and cheap modern woofer. I'll have more details later.
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Old 17th August 2012, 03:45 PM   #16
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So I'm going to call these the "econo mid-horn". I've been looking at the econowave designs for a few year (using the jbl copy waveguide and compression tweeter) but have always been disappointed with the overall sensitivity once baffle step correction is done on the woofer. Happened to be looking at PA kick bins, mid horns etc, and came across these old designs - EV SH1502ER and JBL 4560, then the Altec 816, which are a vented, horn loaded woofer. Just to be clear, these actually use the woofer in a bass reflex ported rear chamber that fires out the front of the cabinet.

The EV version claims a sensitivity of 102.5 db/w/m.

There are a few keys to this design. They do not horn load the driver into the bass range, thus the horn is much shorter (~1 ft) and smaller - the bass reflex porting fills in the bass in the lower useable octave. This design is a high efficiency midbass/midrange, so don't expect much below 100hz, and use of a sub or stereo subs is expected.

Lack of a baffle means no baffle step correction and resulting loss of efficency. Most drivers should be able to be boosted several db's in efficiency above their spec'd measurements and tuned for a relatively flat passband, +/- 2 db. For example, the Delta-12A I simmed last night spec's at around 96-97 db/w/m on an infinite baffle, or 2pi space (afaik) from 100 to 1000 hz. In the horn+vented box its around 102db +/- 2 from 90-700 hz. If you were to put this woofer in a normal box, you would have to baffle step correct it and it would end up around 93db in the midbass. So that seems like a massive increase in efficency to me, and a very good reason to use this type of design.

There are other variations of this type of design, that I believe make use of phase plugs to further extend the high frequency response with good success at the expense of build complexitiy. An alternative seems to be to use a woofer that has a natural response above 1000hz, to attempt to counter the rolloff off the horn. I'm not quite sure how this will work in practice, with dispersion etc. But it should, in theory, be enough to match up with a econowave compression tweeter around 1500-2000 hz.

Overall, I'd like to come up with a design that is cheap and simple to build, while sounding reasonably good and going LOUD. It would greatly preferable to avoid any complex horn shapes - no curves, multiple angles, etc, but will have to figure out how to sim a very simpler than cone horn shape. I'm not sure what the effect of having parallel top and bottom panels with curved sided in the altec, vs. box conical in the ev vs. curved and angled in the jbl.

Anyway, that's what I have so far. I think there's alot of potential here.
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Old 17th August 2012, 05:59 PM   #17
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The altec pro website is a wealth of information, go here and pull up the 816VIX spreadsheet:

Altec Lansing Professional Audio - Vintage Speakers

I believe the dip around 650hz and the peak around 850 are caused by the parallel top and bottom panels of the horn, spaced ~16" apart....?

Here's a version with ports on the sides:

http://www.lansingheritage.org/image...mer/page02.jpg

Last edited by turbodawg; 17th August 2012 at 06:05 PM.
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Old 17th August 2012, 07:42 PM   #18
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Looks nice with the vents on the side, you think the standing waves on front can be eliminated as per GM with an angled piece top and bottom of the horn mouth from the baffle instead of the straight piece. How about the plans for EAW MR101 which is the 10" version used in clubs in NYC previously by Paladium in the '90s from Richard Long Associates nice sounding back then and loud if I can remember. They have the phase plug infront mounted on the screen mesh. Typical EAW if you look also on the EAW KF850 concert cabs!
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Old 17th August 2012, 09:00 PM   #19
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No, not eliminate, merely cause them to rapidly decay away instead of just droning on, comb filtering with the horn's response. Note too that only one panel need be angled if it's at 12 deg and that adding 'wings' will further help plus lower the horn's horizontal response/baffle step.

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Old 17th August 2012, 09:20 PM   #20
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djlivex,
I think what everyone forgets is that the original Altec and JBL horn reflex cabinet enclosures were designed to go behind a movie screen and the bass response is not that good. The response of the ports below the cutoff frequency of the horn is down by more than 6db and the integration with the horn is really not very good. Why not just use the horn without the ports, sealed back and add a true bass tuned cabinet. That is what happened to all of the PA enclosures during the 70's, the ports were deleted from most of these types of cabinets. The Eq required to bring the level of the bass up to the horn gain is severe and the amplifier power required is heavy to do this. Also you get into the uncontrolled excursion of the driver at these frequencies and it was common for the cone to slam into the back of the throat of the horn. Just an observation from someone who has been there with these enclosures since the late 60's. Believe me I moved my share of A7 and A2 enclosures.
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