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I'd like to make a larger horn to go with my Jabo KH-55A horn, but am unsure if they are an exponential horn? I'm looking to make a horn with a throat of 250mm or 300mm and a mouth up to the width of a standard sheet of plywood (so just under 1200mm). I've not had any luck with the horn calculators on the internet, how low could I go? I'm looking to use either a 18sound 10M600 or 12MB1000. Any ideas?
Thanks!
Edits: 08/31/09 08/31/09Follow Ups:
Hi j_s,
The Jabo horns do have an exponential curvature according to the manufacturer (I asked him some time ago).
Best regards
Peter
Thanks PK. I've tried the expo horn calculator at mh-audio.nl, for a horn with a throat of 300mm it calculates a horn 70.16cm long and 109cm wide for a cf of 100Hz, does this sound about right?
Hi J_S,
The data you have provided are a little insufficient in order to do the calculations. I haven't got an exponential horn calculator available and uses HornResp instead.
If you by "300 mm throat" means 300 cm2, then a circular horn, 70 cm long and a diameter of 109 cm with an exponential curvature should have an Fc=134.4 Hz.
Best regards
Peter
Hi, I've just been looking at using the 18sound 12ND710, so I'd be looking at a throat diameter of 300mm, trying to get the lowest frequency extension possible with a round horn mouth of 1100mm.
18sound 12nd710 t/s parameters
Fs 52 Hz
Re 5 Ohm
Sd 0,053 sq.mt. (82,2 sq.in.)
Qms 6
Qes 0,2
Qts 0,2
Vas 92 lt. (3,2 cuft)
Mms 40 gr. (88,3 lb)
BL 18 Tm
Linear Mathematical Xmax ± 5 mm (± 0,20 in)
Le (1kHz) 1 mH
Ref. Efficiency 1W@1m (half space) 6% (100 dB)
Best regards
Peter
Hi J_S,
Above you see 'rought and dirty' simulation of the horn you have specified in half-space (that is, on the floor). With the specified driver it will take you just around 100 Hz 'in room'.
The horn throat you have specified is very large for the given driver. With a smaller throat you will raise the efficeincy a little and also make the horn go a little higher.
Hats off, if you want to turn this horn yourself - it's a lot of work for sure! You may consider either making the horn rectangular which will make it a lot easier to build, or purchasing a 'ready-made' one from StereoLab for instance. They make 140 Hz tractrix horns for different throat sizes at fair prices. The 140 Hz horn from StereoLab will not go quite as low of course.
Maybe someone else will chime in - I'm no horn expert for sure, I have just punched the numbers....
Good luck!
Best regards
Peter
Hi, thanks for the simulation, couldn't find the actual cone diameter on the eighteensound website, only the nominal diameter, but the baffle cutout is quoted as being 282mm, so I'm guessing this would be a better throat size.
Hi J_S,
The usual rule of thumb for throat sizes for bass horns is more like 1:2 or 1.3:2, so you should probably consider a throat size in the 260-300 cm2 range.
Best regards
Peter
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