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Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz

69.219.145.131
Posted on February 18, 2010 at 10:06:48
Gera
Audiophile

Posts: 244
Location: Illinois
Joined: April 23, 2000
 Friends/Edgar horn specialists help me out.

I recently purchased a pair of Edgar 80Hz straight midbass horns. Overall, they sound very good but I'm getting huge peaks, over 10 db, at 80 - 100Hz in my room. Other freq. are flat. I measured in THREE different listening locations -- same problem. I cross them at 80 and 750Hz and measurements were done having the Edgar horns running only (so I know it's not the subs interfering with the sound).

Is this a room issue or a characteristic of my Edgar horns? One thing I'd like to note, the horns are sitting on 24" high subs; my system is tuned to listen standing up. See pictures:

http://picasaweb.google.com/noviygera/FunktionOne?authkey=Gv1sRgCOSSwZr886WaZQ&feat=directlink


thanks,
Herman

 

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Edgar 80hz Midbass--back chamber stuffing, posted on February 20, 2010 at 09:29:52
Pooge
Audiophile

Posts: 280
Location: N. Virginia
Joined: December 14, 2004
 Is there an optimum amount and type for the stuffing in the back chamber that can be recommended without measuring the response?

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz, posted on February 18, 2010 at 23:11:22
Bruce Edgar
Manufacturer

Posts: 525
Joined: October 29, 2001
 The response you cite is the true response of the 80hz exp horn. It has a 3/16 th size mouth. I have experimented with an 85 hz hyperbolic horn with a 1/4th size mouth (Titan II design) and a 75 HZ hyperbolic 1/4th size horn. My findings are that the 80hz horn works well at short listening distances like 8-12ft. The 85 hz hyperbolic horn is flat down to below 80hz and sounds best at listening distances 12-15ft. For a really large room, the 75hz horn goes down below 70Hz and requires at least a 20 ft listening distance. As I remember Rick's room, we sat at least 20ft away from the horns.

As a rule of thumb you must be one wavelength away from a horn to be in the far field radiation zone for the best sound. For 100Hz, this distance is a little over 11ft. The 80hz horn is essentially an 100hz horn with an extention to 80hz. In my home system, my listening distance is about 10ft. I tried both the 85Hz hyperbolic and the 80hz exp horns. The 80Hz exp won out. 85hz horn sounded better in back of my sofa rather than at the seated position. I now use the 80hz exp horn in my home system. So from my experience the one wavelength guide is a good rule of thumb.

So what do you do if you want response down to 70-80hz and your listening position is under 12ft? Use a bottom exhaust midbass horn like my Slimline horns use. The bottom exhaust changes the horn into a nearfield device. If I didn't use this bottom exhaust principle with my 35Hz sub, you would have to sit more than 30ft away fom it. But other than being a size of a refrigerator, no user complains about not working in regular sized rooms.

Hope this explanation clears the confusion about which midbass horn to use. Bruce

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz - on top of H-baffle, posted on February 19, 2010 at 09:36:54
freddyi
Audiophile

Posts: 3852
Joined: December 6, 2001
 Hi Bruce - look at Herman's installation - I missed his link - the midbass horns are sitting on top of H-baffles. Outdoors I found no ripple in the 100Hz horn - it behaved with ~3rd order slope below cutoff. Are the downward mouth horns more successful in the near field partly due to diffusion of beaming effects? Partly due to the wave hugging the floor boundary?

Best, Freddy

Herman's HORN SETUP

copy and paste in case above link quits

http://picasaweb.google.com/noviygera/FunktionOne?authkey=Gv1sRgCOSSwZr886WaZQ&feat=directlink#5434523461644780818
Karlson Evangelist

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz - on top of H-baffle, posted on February 19, 2010 at 13:20:31
Bruce Edgar
Manufacturer

Posts: 525
Joined: October 29, 2001
 There some unusual effects if you place the mouth directly on the floor, especially like my 100hz horn design. It is actually too short a bass horn, but if it is placed several inches above the floor the response looks like a normal 100hz horn should look like. But place the horn right on a concrete floor, the response turns into a nasty sounding resonant peak which is very close to Leach's resonant frequency. The same response is predicted by McBean's horn response software. But as I said earlier, this response goes away if the horn is raised and inch or two. A highly raised position will not exhibit these effects, only a reduced efficiency from the absence of a boundary.
The 80Hz horn does not exhibit similar behavior when place on a boundary except for a spike in the response at the low end. This usually doesn't sound good either, so I always recommend that all mid bass horns be mounted on roller wheels or spikes to remove boundary effects. Bruce

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz - on top of H-baffle, posted on February 19, 2010 at 16:38:14
freddyi
Audiophile

Posts: 3852
Joined: December 6, 2001
 thanks Bruce - that's interesting and good info
Karlson Evangelist

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz - on top of H-baffle, posted on February 19, 2010 at 16:01:11
Steyr
 I have to raise my mid bass front horn [80hz-1khz] about 2 1/2in or response is altered. Since I found this out the hard way folks should thank the good Doc for the tip.

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz - on top of H-baffle, posted on February 19, 2010 at 19:25:52
Wojciech
Audiophile

Posts: 4120
Joined: June 23, 2009
 Isn't it because the midbass horns you guys are using are far too short and have too big of a throat to properly EQ the responnse down to the flare?

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz - on top of H-baffle, posted on February 20, 2010 at 08:05:31
Bruce Edgar
Manufacturer

Posts: 525
Joined: October 29, 2001
 The 80Hz exp horn needs to be extended couple of inches to a 1/4th size mouth, and then the response will look better. But I designed the horn to get the best performance out of a 2ft horn, and the 80 was one of the better combinations. In many applications it integrated better into smaller listening rooms better (as in my listening room) than the midbass horn with better low end response. But as I pointed out in earlier posts, in larger rooms the Titan II (85 Hz hyperbolic) and the 75hz hyperbolic horns perform better at longer listening distances.

If I looked at the short midbass horns from a straight theoretical perspective, I would doubt that tghey would not perform well. But after building many models of many different flares and mouth sizes, I can state that they are a good choice for midbass horns with good performance in small to moderate sized listening rooms. They are simple to build for the DIY person and you can align the midbass and midrange horns which you can't do with longer bass horns.

The 15" woofers can handle the larger throat sizes. The optimum throat size's are typically around 60 sqin. The 9"x9" (81 sqin) is not too much larger. At larger throat sizes, you can run into problems. I've experimented with 12" woofers on the same throat, and definitely they will have problems with essentially a 1:1 coupling. Bruce

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz, posted on February 18, 2010 at 17:45:20
weltersys
Industry Professional

Posts: 685
Location: FL
Joined: September 28, 2004
 Looks like you are getting a serious room problem due to the ceiling height, room width and length.

About 7, 15, 25 feet?

As Bill says, take it outside to confirm, but there is no reason that horn should do that on it's own.

You will probably want to cross the mids above and the subs below the room boom to make an acoustically flat crossover.

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz, posted on February 18, 2010 at 12:47:40
cv


 
Floor to ceiling mode? How do they measure if you put them on the floor at the same locations?

 

Based upon my experiences with the 75 hz straight horn, posted on February 18, 2010 at 11:34:36
rickmcinnis@dogwoodfabrics.com
Audiophile

Posts: 3040
Location: Atlanta
Joined: December 15, 2003
 I would ask you what choke you are using the roll off the horns?

Are you using the ELECTRA PRINT?

My experience was that anything with a higher DCr will make you think you have room problems.

Do you get the same anomalies with no choke in series?

 

Are you speaking of a series choke as a low pass filter?, posted on February 18, 2010 at 11:45:34
Ivan303
Audiophile

Posts: 48887
Location: Cadiere d'azur FRANCE - Santa Fe, NM
Joined: February 26, 2001

The original poster writes "I cross them at 80 and 750Hz", so I guess my question would be:

How are they crossed at 750Hz?

How are they crossed at 80Hz?

What driver is used?

Why, in the picture linked to the post, does it appear that I can see the tiled floor inside what looks like the horn mouth?

Never saw an Edgar Titan II 80 Hz straight horn look like that. See Picture above!



First they came for the dumb-asses
And I did not speak out
Because I was not a dumb-ass

 

I agree with you, posted on February 19, 2010 at 13:08:26
rickmcinnis@dogwoodfabrics.com
Audiophile

Posts: 3040
Location: Atlanta
Joined: December 15, 2003
 I have had many of the horns but never one that looked like that.

I must say the photograph leads one to believe that a very fine job of veneering was done.

750 hz seems way high. I know Dr. Edgar would like to find a driver that would allow this but I think I remember hearing that 500 was as good as one could do with less than field coil drivers.

If the question was addressed to me, yes, I was speaking of a choke as a low pass filter.

Rick McInnis

PS Dr. Edgar you have made me mad as I have made clear but I still love you and your horns. I hope you are doing O.K..

 

don't look like titan IIs to me, also the op said they were 24" off the floor, posted on February 19, 2010 at 08:47:19
Dan_ed

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz, posted on February 18, 2010 at 11:15:41
Bill Fitzmaurice
Industry Professional

Posts: 5370
Location: New England
Joined: October 20, 2002
 Measure them outdoors, well away from any buildings. That gives an accurate result. Any deviation from that is caused by the room. I'd be looking at the distance to the rear wall being the culprit.

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz, posted on February 18, 2010 at 10:39:33
Dan_ed
 I get that around 250Hz in room with my straight Titan II's. Mine are about 4" off the floor.

 

RE: Edgar 80hz Midbass problem -- uneven freq. responce 80 to 100Hz, posted on February 18, 2010 at 10:14:28
freddyi
Audiophile

Posts: 3852
Joined: December 6, 2001
 unless its a lot different from the old 100Hz shell I wouldn't expect the speaker to cause those effects (??????) - what's its throat size, mouth size and path length?

in approximate half-space, here's a Klipsch K43 type versus JBL 2220 light curvilinear cone type in Bruce Edgar's earlier 100Hz horn with an 80sq.in. (8x10) throat, ~20.5"x20.5: mouth and ~20.5" path from throat to mouth
(100Hz distortion shown for K43 - 2220H was ~10dB higher in distortion at that point.)

Karlson Evangelist

 

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