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Ultimate Horn Speaker - First thoughts
Ultimate Horn Speaker - First thoughts
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Old 13th October 2017, 12:18 PM   #1
qQxSzbwqYW is offline qQxSzbwqYW  United States
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Question Ultimate Horn Speaker - First thoughts

Hi everyone, first post here.

Im working on a project, so first thoughts are not exactly acurate, for some time now.

Started 1998, big step to 4 way active horn 2007, and for 2 years now studying basics and buying material (drivers, amps etc).
The goal is, the ultimate final speaker - like many had this plan and failed before


My approach is somehow different, as im collecting all problems, and try to solve all, instead of focusing on 1.
Also, im trying to build a bridge between all the measurables rationals and some "soul" (buying non logical things because u believe sounds / looks sweet though the measures are not justifying )


So, in a nutshell, i want to give you a brief forecast bout the plan.
First tell why, thoughts of advantage, and if anyone wants, further xplanations.

1. Basics: In analogue times amplitude response + as little amount of drivers (group delay) was a main focus. Since FIR, all the linear-distortions are invertable, i want to build with focus on room acoustics and non-linear-distortion - which are in my eyes main obstracles.


2. More important than harmonics are multitone or IMD. The more ways the better, out of a principle. Downsides of group delay is handled via FIR.


3. Speakers are usually used in too wide passband, not enough capacity below/above for clean crossover slopes - requires more ways, see point 2.


4. Room acoustics spoil the best concept, its rarely considered thouroughly. The room has to be part of the speaker whereever possible. With special focus on the modal range and Schroeder - band.


5. Active, FIR, efficiency, are of course a must.




My solution is:



DC-90Hz: a nearfield dipole behind the sofa, with 4x15 or 2x21" driver


90-250Hz: two corner horns stacked vertical, each 4x8" drivers, phaseplug + folding mods + mouthmod, per channel


250-700Hz: two lowther PM4a in 1x1x1 meter horn, "half-cut-design" to use floor as a seemless mirror


700-1500Hz: A JBL 2482 in a 220Hz Radial Horn


1500-4000Hz: 2x Fostex FD200L as a pushpull-compound in a 300Hz TAD/Vitaxox-alike Radialhorn


4000-10000Hz: a JBL 2420 driver in JBL 2312 long conical horn


10000-50000Hz: A Fostex T705 tweeter



The mains would stand close to the corners, half meter.
Listening pos. is 3-4 meters triangle, middle of the room.
The complete sealing, front wall, and front part of sidewalls will be covered with special foam, absorbing 100Hz 0.1 / 150Hz 0.5 / 250Hz 1.0 and up.


The narrow beaming of HF + damping will give xcellent response on one hand, but too dry perception on the other. Ill compensate this with:
- a extra channel of wide dispersion slit radiator on the back, 5ms delay (precendence effect) and -10dB below the mains, creating intentional additional room reflections (modifyable)
- also xtra channel of optional (!) small horn & 8" fullrange, to cover on -10dB below mains in a resonant chamber 200-1000Hz a so called "injector" for more 3-dimensional body-borne-noise (verified positive results!)


All channels will be active driven with linear response+phase FIR correction plus soft-slope low order linear-phase crossovers.

I find myself revising details every couple of weeks for last year.
Recently i only make small changes over months, feeling that i head to the end of planning.


I'm asking you which obstracles you see in this concept, what may cause problems, and what i forgot to consider. I hope to find justification to most concerns, but more than that i hope to find an "aaaa yes damn i forgot" thing


cheers
Josh
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Old 13th October 2017, 12:53 PM   #2
hasselbaink is offline hasselbaink  Denmark
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You have obviously thought about the sound you wish to achieve, but I would be concerned about the destructive interference between drivers that have such a large center-to-center distance using 'soft slope' filters.

Kris
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Old 13th October 2017, 12:58 PM   #3
Scott L is offline Scott L  United States
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Ultimate Horn Speaker - First thoughts
1) di-pole bass (aka open baffle) is the single LEAST efficient way to attempt bass.
In contrast, an infinite baffle would be thee most efficient (save for horn bass, but too large and complex for the home)

2) far too many crossover points.
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Old 13th October 2017, 01:23 PM   #4
qQxSzbwqYW is offline qQxSzbwqYW  United States
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Hi Scott, Hi Kris


"Many XO, low steepness - problematic. "


Yes. Usually.
1. With linear phase FIR the summing on the lis-pos. is still flat, fine & ripplefree.
2. I wasn't precise enough, im using subtraction filter with steep lowpass but soft highpass. Far less critical.
3. This is a pure off-axis problem. Not relevant for the listening position.
Normally it is, because of indirect sound coloration due to lobing. Which should be very very low here, as the room is dampened aggressively on one side, but controlled by the rear-diffuse ones on the other.
4. Majority of coloration is happening on the big off axis scales (60-180) which is exactly the part of the room killed with foam.




" 1) di-pole bass (aka open baffle) is the single LEAST efficient "


Yes. That's the advantage here. You loose up to 20dB within a few meter.
The reason why you have superband flat response in the nearfield.
Nearfield also boosts the SPL. While all horns are 4 meters away, that one will be 0.3m.
At the end, same result: little voltage, little xcursion, resp. little distortion, while big SPL at the ear.


See simulation and scribble:


Click the image to open in full size.


Click the image to open in full size.


Click the image to open in full size.


simulated at 2.8 volt / less than 1mm xcursion >20Hz
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Old 13th October 2017, 01:30 PM   #5
qQxSzbwqYW is offline qQxSzbwqYW  United States
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Forgot to add, Kris:
Center-center distance is way smaller than in most 4-way round horns (like lecleache), as I stack vertically only radial horns, that are wide but flat. So my Offset in the mid & highs are about 20cm between the ways.
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Old 13th October 2017, 01:45 PM   #6
qQxSzbwqYW is offline qQxSzbwqYW  United States
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btw, that simulation was with single 15" only, so theres more to expect at the end.
Here a real world mockup measurement of the woofer, 10-100Hz
no gating, no smoothing, listening position, full sweep
Click the image to open in full size.

Last edited by qQxSzbwqYW; 13th October 2017 at 01:51 PM.
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Old 13th October 2017, 05:39 PM   #7
whgeiger is offline whgeiger  United States
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Default The Listing Space Comes First!

Once chosen, then work on the system design to fill it with sound.
Most likely, a 'horn farm' will not be included in any solution, appropriate to a domestic venue. WHG
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Old 13th October 2017, 06:00 PM   #8
qQxSzbwqYW is offline qQxSzbwqYW  United States
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Y.....esss.
Many thanks for earlier posts focusing on the tech part !
Appreciated. More of that pls
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Old 14th October 2017, 01:26 PM   #9
LineSource is offline LineSource  United States
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PMA! has an excellent thread on a horn speaker using dipole woofers. Nelson Pass also published a note on slot loaded dipole woofers. This "stack-them-up" woofer construction might fit your design goals.

My DIY Horn setup

S.L.O.B.S.
Slot Loaded Open Baffle Subwoofer

This dipole cabinet generates a high impact bass wave launch with a focused air pressure energy that travels several feet before diffusing. In a small room, the slot is aimed at the listener in an effort to increase the perceived dynamic impact. This directivity control is a good match to horn or dipole polar pattern. At modest SPL levels, the slot's focused energy wave is linear over a wide frequency range. The slot dimensions are smaller than the crossover wavelength to avoid resonances. JBL measures a directivity index DI = 13 on their dual 15" slot loaded woofers.
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Old 14th October 2017, 01:56 PM   #10
Scott L is offline Scott L  United States
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Ultimate Horn Speaker - First thoughts
Quote:
Originally Posted by LineSource View Post
This dipole cabinet generates a high impact bass wave launch with a focused air pressure energy that travels several feet before diffusing. In a small room, the slot is aimed at the listener in an effort to increase the perceived dynamic impact. This directivity control is a good match to horn or dipole polar pattern. At modest SPL levels, the slot's focused energy wave is linear over a wide frequency range. The slot dimensions are smaller than the crossover wavelength to avoid resonances. JBL measures a directivity index DI = 13 on their dual 15" slot loaded woofers.
Does not have to be di-pole in order to work. As a matter of fact, I think that an even greater pressure wave is created when there is no wrap around loss.
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