SubMaximus -- A Large Front-Loaded Horn for UXL18 and Stereo Integrity HT 18" - Page 17 - AVS Forum
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Old 07-23-2014, 08:47 PM - Thread Starter
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posted.

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Old 07-31-2014, 06:00 PM - Thread Starter
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post mortem

a couple of things have had me concerned about how close the actual measurements were to the model.

first, there seemed to be a little more 'chop' in the frequency response than in the model.
second, there seemed to be more "ripples" under 100hz than the model predicted.
third, and of primary concern was the larger drop at the last leg of about 8db or so where the model forecast about 6db or so.
fourth, the low corner seemed lower than the low corner in the model. the target low corner was around 14-15hz and actual ended up around 10hz or so (which is getting into likely signal chain rolloff).

so with all that considered, and after reviewing the layout again, I think what has happened is that with three 180 degree turns, the effective path length has been extended by about 50% relative to the model. this is good news and bad news. it means that with three 180 degree turns, a horn can be shortened by about 33%, which in this case would provide a good deal of space savings. that however is just a theory for the moment.

in order to test the 50% "effective increase in length" hypothesis, I went back to the original hornresp model and increased each leg by 50%. the picture below shows the original target in red and the 50% longer horn in black. the 50% longer horn in black exhibits all four characteristics that were noted above.

as everybody who followed along knows, the construction was a masterpiece, so I don't think any concerns rest there.

the design just missed the mark by coming in with a lower effective tuning than plan.


original hornresp model (red), 50% increase in path lengths (black):




actual measurement with low pass filter in place:






edit: updated initial 25% number to 50%.
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Last edited by LTD02; 07-31-2014 at 06:34 PM.
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Old 07-31-2014, 06:27 PM
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So design up another... and I'll build it and test it. How's that ? But make it even more awesome so I can wreck my house with a few of them. The only issue I have is one dimension needs to be like 30" to fit behind screen wall. A few more inches probably ok. But the other dimensions can basically be about as big as you want. If you walk me through folding process that would be super cool.

This idea and subwoofer is just too awesome to let it die. It needs a version 2.0

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Old 07-31-2014, 07:06 PM
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SUBMAXIMUS V2.0: "home wrecker"

What drivers would work in this monster? Anything other than UXL18 ? (that driver is fine with me btw)

also, what low pass filter was in place? It doesn't look so strong...

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Old 07-31-2014, 09:23 PM
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Quote:
Originally Posted by maxmercy View Post
The model is wrong. Make all the hornresp segments PAR in the model (according to post 1, the segments are EXP) and you will see the results meet the model much more closely w/ regards to the ripple amount. I didn't notice this until after I looked at it when I entered the model into hornresp myself a few days ago. If you will build a re ?horn with a rectangular cross-section, always use PAR.

The lower corner is because of horn length/x-section areas not accounted for in the corners by hornresp.

JSS
Can you explain this more?

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Old 10-29-2014, 09:22 AM
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Quote:
Originally Posted by Mfusick View Post
That is the idea that intrigues me. I want to build a really big horn that digs down that extra octave. I know it takes 4x as much space but I think I could pull it off. If I could not get that extra octave then I will probably abandon horn idea. I am not interested in doing something average.
I've been following this build for a long time now, and its pretty amazing. I would really like to thank LTD02 for all his time and willingness to share his expertise.
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Old 10-29-2014, 09:38 AM - Thread Starter
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asarose did the tough part.


there has been some more thinking about this in the background, but I don't want steal any thunder (so to speak).


.............


"Can you explain this more?"


par is the expansion rate of a horn that uses straight sides such as most of these folded horns.
however, by sectioning the horn into smaller sections each with an expansion rate that increases with the length, the overall result is no longer par, but can be closer to con (conical) or even exp (exponential).


while it is true that each section should have "par" as the flare rate, since the overall horn follows generally an "exp" expansion, it doesn't really matter if each section is modeled as par or exp.


if it is still confusing what is going on here, imagine a curved line. now try to approximate that curved line with a single straight line. you can't. however with 3 straight lines, you can get close. with 5 you can get really close and so on. so even if you are using straight lines, section by section, the overall smooth curve "exp" can be well approximated. just because each section uses a straight line, doesn't mean the entire horn flare is expanding as a straight line.


this post shows the neglible effect of switching the sections to "par" from "exp" because the overall horn was designed to be "exp".


SubMaximus -- A Large Front-Loaded Horn for UXL18 and Stereo Integrity HT 18"

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Old 10-29-2014, 11:08 AM
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This really is a great design John! It is one of my favorites for sure.

Kudos once again!
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Old 10-29-2014, 11:24 AM
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I'd rather have a couple of these on the side walls being as they are only a couple feet wide then a ported box that jets to far out into the room.
Building vertically doesn't take up much real estate.
Can a FTW21 be used also?
I guess that would totally change the design though.

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Old 11-04-2014, 08:23 PM
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I discontinued my test in as much as things are definitely
working and it was hotter than he&& for july and august
BUT! loading vertically can help wrt to the large footprint
on the dolly vertically , the horn would be abput 35-36 inches from the 8 foot ceiling, under 1 meter
since it weighs about 350 making height adjustments could be tricky , , ,
BUT I can get the help to try at least that and the distance wrt to loading adjacent to the wall could provide other data i.e. tight to the wall, 6 inches from the wall, etc.
one measurement John had me try back in the day was in the back of the room directly into a the rear corner, with the horn at 6inches, and 1/2 and then 1 meter and the REW mike about 14 feet away at the MLP, after the near field measurements
the denon 4000 seems to make love to me in the bass department, though the 2 BF subs in an 8 ohm series/parallel combo and being 14 feet apart make any statement regarding "best bass EQ ever" seem sketchy, but
there's plenty of it, no localization
and gaming with the Xbox1 and the sound and especially bass potential there, it does get your attention
Any constructive and or feasible suggestions will be considered
after all there is NO! WAF and we all might just learn something . . .
and every now and then I hear a quiet whisper,
"MAX is lonely, build another one . . ."

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