AllenB: 70 HZ will do for cutoff. From my limited understanding of horn design, I’m not particular about the T-factor. I am hoping for 20-70 HZ, as near flat as possible, and fitting into the allotted space I have. The horn can be bent/folded if required as well. If I understand correctly, at the frequencies I am hoping to achieve, folds and bends will not be a significant impediment. My understanding is that a straight horn is usually preferable, but I’m not sure if this matters for 20-70 HZ..
Cutoff is a horn parameter, not the usable low end. Usually you choose a cutoff frequency less than half the lowest frequency you want it to produce.. and high pass it all. At bass frequencies the attendant group delay issues are usually overlooked and you may get away with using a higher cutoff frequency than you would with a higher frequency horn.
T factor is usually set near 0.7-0.8 for quality purposes, but at bass frequencies you may take it nearer to 0.
For folds, like for straight sections, keep them acoustically small.
You can halve a horn if you put it up against a wall.
T factor is usually set near 0.7-0.8 for quality purposes, but at bass frequencies you may take it nearer to 0.
For folds, like for straight sections, keep them acoustically small.
You can halve a horn if you put it up against a wall.
AllenB: thanks for the refresher on Fc and T factor. Fc of 160 HZ will be good then, and a T-factor of .8 is good. In the first figure you posted in this thread, the two horns share a continuous single mouth on one side, and use the wall as the other side of the horn. Is this what you mean by halving a horn when it is up against a wall? If the design in that figure is scaleable, I can use it as the basis for mine. Will Hornresp simulate a horn of this size?
Greets!
Product specs, details? Driver (preferably measured since a compression horn design) specs?
I presume you mean 16 Hz Fc, though to control a woofer down low over a narrow BW (~ 2 octaves in your case) ideally requires a ~reactance annulled (hyperbolic) compression horn and nowadays a tapped variant maybe better overall if for no other reason than it's easier to design/build and Brian might have a folding designer to make it even easier.
Ignoring for a moment the three dimensional aspect, you can use a wall as a mirror to take a hornresp horn you've modelled in hornresp but to use half the throat size, half the mouth size but the same length. The parameters/shape/cutoff etc will be different to a horn you'd ask hornresp to model which had those throat/mouth/length qualitles to begin with, so be careful about scaling and better model to be sure.
In the end you have a bass horn for less space, which is a big deal.
Such a big deal in fact that you may want to experiment with the T factor and cutoff to ensure you have something workable.
In the end you have a bass horn for less space, which is a big deal.
Such a big deal in fact that you may want to experiment with the T factor and cutoff to ensure you have something workable.
Hi GM!
I have a lot of different drivers on hand. I intend on building this horn in a way that will allow me to easily swap drivers and decrease or increase back chamber volume. I will leave space so that a variety of different back chambers and/or compression/front chambers can be attached to the throat. Even though I have a lot of drivers, if required I will purchase a couple more in order to get it right. The emphasis is on sound quality and not SPL. This bass horn will be used in a Japanese style listening bar rather than in a nightclub or live music venue.
Here is the list with the specs I have...
For the Eminence made 18” drivers (I have 2)…
-Model #18245A
-4 Ohm
-400 watts RMS
-23 HZ free air resonance
-96 DB efficiency
-7.9 mm xmax
-Qts .32
-120 oz ceramic magnet
I have a pair of Klipsch K-33E (I thought I had four, but two are something else). Specs are...
Fs = 34.46 Hz
Qms = 7.39
Vas = 301.7 liters
Cms = 0.268 mm/N
Mms = 79.47 g
Rms = 2.328 kg/s
Xmax = 8.2 mm
Xmech = 12.3 mm
P-Dia = 336.6 mm
Sd = 889.6 sq.cm
P-Vd = 0.729 liters
Qes = 0.41
Re = 3.39 ohms
Le = 0.96 mH
Z = 4 ohms
BL = 11.93 Tm
Pe = 150 watts
Qts = 0.388
no = 2.903 %
1-W SPL = 96.78 dB
2.83-V SPL = 100.5 dB
A pair of Peavey Black Widow 1504DT-4 originally used in an FH1...
Re - 3.5
Fs - 31.3
Qts - .29
Qms - 6.2
Qes - .32
Vas - 385 litres
No - 3.6%
Xmax - 3.0 mm
Vd - 240 ml
A pair of Eminence Kappa 15C...
| SPECIFICATION | |
| Nominal Basket Diameter | 15", 381 mm |
| Nominal Impedance* | 4 Ω |
| Program Power | 900 W |
| Watts | 450 W |
| Resonance | 31 Hz |
| Usable Frequency Range | 63 Hz - 2.8 kHz |
| Sensitivity* | 98.1 dB |
| Magnet Weight | 80 oz. |
| Gap Height | 0.375", 9.5 mm |
| Voice Coil Diameter | 3", 76 mm |
| THIELE & SMALL PARAMETERS | |
| Resonant Frequency (fs) | 31 Hz |
| DC Resistance (Re) | 3.68 Ω |
| Coil Inductance (Le) | 0.88m H |
| Mechanical Q (Qms) | 10.14 |
| Electromagnetic Q (Qes) | 0.25 |
| Total Q (Qts) | 0.25 |
| Compliance Equivalent Volume (Vas) | 329.9 liters / 11.65 cu.ft. |
| Peak Diaphragm Displacement Volume (Vd) | 206 cc |
| Mechanical Compliance of Suspension (Cms) | 0.35 mm/N |
| BL Product (BL) | 14.7 T-M |
| Diaphragm Mass Inc. Airload (MMs) | 77 grams |
| Efficiency Bandwidth Product (EBP) | 124 |
| Maximum Linear Excursion (Xmax) | 2.4 mm |
| Surface Area of Cone (Sd) | 856.3 cm2 |
| Maximum Mechanical Limit (Xlim) | 11.6 mm |
| MOUNTING INFORMATION | |
| Recommended Enclosure Volume | |
| Sealed | N/a |
| Vented | 40-79 liters / 1.4-2.8 cu.ft. |
| Driver Volume Displaced | 0.138 cu.ft. / 3.92 liters |
For the sake of completeness, I also have four 15 inch PA style drivers from a Yorkville cab that I don't have any specs for. They look like the Peaveys with accordian surrounds and similar magnet size.
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I would like to use the horns from 20 to 80 HZ. I meant to say cutoff of 160 HZ. 20 HZ is good for a -3DB point, but lower is better if it is doable. The available space for the horn or horns is 2.5' X 20' X 11-14'. The 20' is the front of the stage. Ideally, there would be two horns with one opening out on each side of the stage, and with the front L and R speakers placed above the openings.
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rdf: The equipment will most likely be located off the stage, but if not I will isolate the booth. It appears from the first figure posted by AllenB in post #8 that there is an area of the stage that will not have a horn under it, so it should be possible to isolate that part more easily. Do you think that this sort of horn will be more of a problem than free standing bass speakers located on the stage?
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I'm still skeptical of the energy drivers in a horn even for low power as they are from a sealed subwoofer suggesting relatively high qts. If you don't need massive SPL a more classic 18" horn driver would work. Something like void v1000, pd18650, various JBL offerings around 10mm xmax with large motors and stiff cones.
Mechanicaly decoupling the stage from the sub would be a good idea.
Indeed, for a 20 - 80 Hz BW we only need a Qts' = 2x (20/80) = 0.5.
(Qts'): (Qts) + any added series resistance (Rs): http://www.mh-audio.nl/Calculators/newqts.html
My comment, after just running afoul of the fire department, is to make sure you don’t violate the building code. It doesn’t matter that your construction is strong enough to support elephants, it has to comply with the code. Of course that would require an inspector...
Good luck. I really like your idea.
Good luck. I really like your idea.
Good point! Had totally forgotten about my 'adventures' in just putting dual huge reflex boxes under a local neighborhood cinema stage. Fire codes tend to be draconian, especially in stick built construction.
kipman725: the Qts I have listed above may not be accurate. That said, if it is, it is in line with the other drivers I have listed that are used in horns made by Klipsch and Peavey. I will need to measure the driver to confirm it’s actual Qts. Again, if I need to buy new drivers, I will do so. Thanks for the recommendations.
This will be a new build and a change of use, so it will require inspection by building, fire, and health departments in order to be approved for occupancy and a liquor licence. I’ve done this a few times, but this is an entirely new thing, so it should be interesting at a minimum.
As I showed, Qts is a function of design BW, so obviously a wider (HF) BW was desired for these horns and you ideally don't need in your app unless using a 1st order XO where you ideally want a ~flat BW out to (XO point x 2^4), which typically you don't want unless all XOs are (optimized) 1st order, though considering that audible driver distortion rises once past its ~ 5 octave design BW (Fs x 2^5), generally not a good plan, especially for (sub) woofer apps.
That said, considering the need for room EQ/voicing, best to use DSP for the entire system since it's become so cheap, relatively speaking.