JBL e120 in midbass horn application
Hi,
I am planning to build a "proper" midbass horn to cover 100 to 500hz to replace my current 80Hz Edgar straight Horn (a compromised design). Efficiency goal is AT LEAST 103db, to match my other horns. The new midbass horn will have a 12" driver, full 100hz mouth area, and possibly 4:1 or 3:1 compression, flare shape not determined yet but most likely -- straight tractrix.
Question:
I have a pair of working JBL e120-8 drivers. Are these good in the above application or should I consider a better candidate (used or new)? What I mean by "good" is actually the best available for my application. If anyone tried e120-8 for "no compormise" midbass or compared it to other JBL models, TAD, Presicion Devices, etc.
Thanks,
Herman
1 Attachment(s)
E120 chassis with 2220 cone question
The e120 and 2202h have different magnet depth. So what happens if I re-cone e120 with 2202h cone?
As far as the phase plug goes:
If the e120 pole piece has a hole in the center I can mount the phase plug to the pole with a screw and a washer. The washer will be at the back of the magnet (covering the vent on the back, the screw will go through the pole piece exiting at the front and attaching to the phase plug.
Attachment 55424
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Sample of the phase plug horn
http://www.funktion-one.com/products/resolution-3-sh/
Look at the midrange section, it uses a 10" mid. The idea is to keep this concept but adapt to the 100Hz horn with 12" driver.
Attachment 55439
Also see this 15" midbass horn.
http://www.funktion-one.com/products/ds15/
my version would be something between the 10" and the 15". You guessed it, 12" midbass!!!
Herman
let's do this, looking for cooperation in Chicago
Quote:
Originally Posted by
more10
I have done some simulations using 2202, E120 and PD.121. They all perform very similar in a horn optimized by hornresp. What varies are the compression factors and horn lengths.
I have used fs=68 to get the first acoustical impedance minimum at 100 Hz, making the horn useable from 100.
Driver compression length
E120 4.22:1 189 cm
2202H 3.4:1 190 cm
PD.121 5.17:1 203 cm
The biggest problem with this kind of horn is the beaming. At 0 degrees the response rises 9 dB from 100 to 400 hz.
Thanks for the modeling! The phase plug will reduce this 9db beaming and diffuse the sound energy on axis, providing much more even coverage. This works well in my midrange horn, the picture of which was posted earlier. It must be noted that this phase plug must be big enough, close to the driver area at the plug's max cross section to "steer" the sound energy around the plug.
Also, the dome (dust cap) must be removed so that effectively REDUSES the driver area and must be accounted for in the modeling. 80" is one long horn already! Also, because the plug is big, the horn throat and flare shape must be adjusted for the plug to maintain the proper flare rate/compression.
By the way, which type of horn flare are you thinking about for this midbass thing?
This is all just my theory but so far the phase plug seems very appropriate for this midbass project and everything is naturally falling in place. Although it is a tricky project, but very simple and elegant at the same time.
Making the phase plug from aluminum is a very good idea and will promote very effective "active" cooling of the pole piece!
here is another Funktion-One model, this one seems more symmetrical, perhaps easier to use as the "base" of the midbass build:
http://www.funktion-one.com/dl/files/2113.jpg
Maybe with a few changes, but the concept seems solid and I am motivated to give it a shot. I am looking for some cooperation on this project, I am in chicago. Will be happy to discuss this with anyone interested. I have an interesting (but tricky) idea on how to approach this so emial me: noviygera (at) gmail
if interested.
Herman