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Old 26th October 2011, 10:15 AM   #1
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Default Entering info into Hornresp

Hi all,

I've been using BBP for years and find this a very easy programme for me to use. Recently I've decided to look into tapped horns and downloaded hornresp-to say I'm baffled would be an understatement! I'm dyslexic and not only do the abreviations for everything confuse the bejesus out of me but the lack of a visual "box" also make it hard for me to mentally picture how my inputs relate to the horn I'm trying to design.

I have two KEF B139 that I'm trying to design a horn for, for a fixed space under a sideboard at home, gross dimensions available are: 46.5"w x 16.5"h x18.75"d. I live in a tiny house-so please do not suggest any other designs as this is the only space I can allocate to the enclosure.

I plan to mount the drivers isobarically mag-2-mag (to use the mags as bucking mags, old CRT sat above enclosure). The face of one subwoofer will be at the throat, the face of the other in the mouth. The enclosure I mentally came up with is pictured (crudely) below and the T/S specs I've pulled of the drivers are below, averaged from the two drivers and then the net figure from wiring the speakers in parallel to get down to a 4ohm load for my amplifier:

Fs: 28.94
QMS: 0.44
VAS: 59.3 net 29.65litres
CMS: 0.4 net 0.2
MMS: 75.34 net 150.7grammes
RMS: 31.25 net 62.5
SD: 323.1cm2
QES: 0.645
RE: 7.12 net 3.56
BL: 12.3tm
QTS: 0.262
No: 0.215 net 0.1075
SPL1w/1m: 85.37dB net 82.36dB
SPL 2.83V: 86.03dB net 86.03dB

Now for the favour: could someone input the above with the dimensions below and take a screen shot of it? From there I hope my brain will kick in and I'll be able to contiue with the design-if not I'll know it's off to the nursing home at 33yrs old Box will either radiate straight into the room (on the floor) or into a bay window (this being preferable as my 7month old will be crawling soon and the 20"x15" opening would be large enough for her to disapear into!) NB: I plan to use .75" MDF all round-as I have a load lying around and little baby=BIG MONEY, so can't go all out on this 1st tester box.

Thanks in advance!
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Old 26th October 2011, 01:56 PM   #2
tb46 is offline tb46  United States
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Hi TheBaronGroog,

Tapped horns are quite sensitive to variations in T/S parameters. I recommend to mount the drivers in a short tunnel that replicates their isobaric position in your proposed design, and than measure the T/S parameters of the combination as it will be actually used.

Have you looked at: Simple Tapped Horn Tutorial using Hornresp - AVS Forum ?

Well, back to work, maybe I'll find time to look at this tonight.

Regards,
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Old 26th October 2011, 02:13 PM   #3
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Hi oliver, thanks for the link-you're not on Diyma too are you?
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Old 26th October 2011, 03:11 PM   #4
tb46 is offline tb46  United States
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Hi, No mainly here on diyaudio. Regards,
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Old 26th October 2011, 03:14 PM   #5
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Ok, someone else then Thanks for your assistance
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Old 26th October 2011, 11:30 PM   #6
bjorno is offline bjorno  Sweden
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FYI: Re=Rdc= ~4.9 Ohm for Kef B139B..

See the simulation data example when used in a one driver T-TQWT:


b
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Old 27th October 2011, 03:01 AM   #7
tb46 is offline tb46  United States
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Hi TheBaronGroog,

There is a problem with your dimensions, the duct section widths plus the (5) board thicknesses add up to more than 18.75". Anyway, I stuck your fold into a drawing, and derived the input values for Hornresp.

As I do not have the T/S parameters for an isobaric pair of your Kef B139 drivers I entered the same parameters as bjorno (for a single driver).

Hope this will help.

Regards,
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Old 27th October 2011, 01:53 PM   #8
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Oliver, you, my man, are a legend-virtual beer on it's way to you!

Yeah, I realise my 18.75" is out when the partitions are condidered-I do have a little more depth to play with-the enclosure will just encroach into the living room a little more. Looking forward to having a play with it all now
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Old 27th October 2011, 03:08 PM   #9
tb46 is offline tb46  United States
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Hi TheBaronGroog,

For what it's worth, the enclosure seems to work fine as drawn, and the mouth is plenty large enough in respect to the Sd of the driver.

Let us know how you get along, pictures would be great.

Regards,
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Old 27th October 2011, 03:45 PM   #10
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Yes, seems to, quite a lucky guess then on my 1st forray into horns! -I'll try it with the drivers in the isobaric config-what differences would you expect to see?

I also ran sims in BBpro, in both clamshell and non-compound vented enclosures-using the same outer box dimensions and 15"x4" vent 160" long, see the results below, on set of results include port resonance-comments would be appreciated as the vented enclosures seem to have a 3dB gain over the TH, which I found odd! Other than output what would be the pros/cons to each design?
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File Type: jpg B139ported.JPG (203.6 KB, 189 views)
File Type: jpg B139ported2.JPG (206.0 KB, 177 views)
File Type: jpg B139TH.JPG (92.0 KB, 33 views)

Last edited by TheBaronGroog; 27th October 2011 at 03:48 PM.
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