Collaborative Tapped horn project - Page 200 - diyAudio
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Old 16th June 2008, 06:39 AM   #1991
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Quote:
Originally posted by cowanaudio
You can't just buy Danley or Geddes speakers here! Freight would cost 1/2 as much as the speakers.
Gday William!

Remember corresponding to you in a post regarding JBL 2242H and 18sound 18LW1400 drivers. Well actually I have taken the tapped horn route, but non-DIY with the TH-112. Unfortunately cab-makers are not easy to come by here, so its not cheap....and I probably wouldn't know if the TH cab is even gonna be done up properly since its outsourced.

For those interested in DSL products maybe can contact Kelvin at www.thesoundbroker.com
He still can't give you a lot of discounts as apparently DSL now is recognised (or marketed/placed) as a premium brand in SR circles.
But I got quite a good deal in shipping (Bax Global/Schenker), I'm not sure if its good to post here but its definitely way below usd500. Our countries aren't that far away neither.
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Old 16th June 2008, 07:10 PM   #1992
obeman is offline obeman  Finland
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Thanks GM, nice work, had a hunch you'd show up with something. that had actually been "small" enought to be built. driver was spl dynamics 15d2 mk4 (in series)
http://www.spldynamics.fi/oldmodels/oldsubs/index-e.htm


had, because chose not to buy the driver - and off it went a day ago.
too different to join these couple mk3s in foreplanned large "infratuned" refl box. wan't 2 more of those for that.. so.. tapped horn was only choise of use, and yep.. that parameter difference.. anyway, good to know driver with those parameters would give results with the design..

is there some formula for calculating mmd -as there seems to be quite a bit difference?

well, onto something that might actually be finished some day..
these 2 eminence govern(at)or.. 12" ohm driver:
http://www.eminence.com/guitar_speak...2&SUB_CAT_ID=4

the plan is to test (and use if got lucky) these is one box, with drivers in V position, sharing the upwards opening first half of the horn after which both having their own, but same sized last part that ends behind and below them again in shared space and opening..

i managed to simulate really nice 50 to 400 hz extension, tho i'm dying to again remember what exactly were lenghts and areas..
is it safe to assume 2 drivers with good enought match were to
work well with shared first horn part?
and that response could be simulated with "one half"?
somehow can't seem to get 2 drivers look similar to just one :/

-Samuli
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Old 16th June 2008, 09:31 PM   #1993
Naudio is offline Naudio  United Kingdom
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try the eminence definimax, what u are looking at is a guitar speaker, it only has a 1.2mm xmax so im guessing a single definimax would be louder as it has a 6.2mm xmax and costs less, also this saves the complexity of the V design, in my opinion it seems logical anyway

2 very nice horns have been made with this driver, mikehunts 30hz version and my own lower tuned 25hz/5db@20hz version, and im very happy with it

however u seem to be looking for a higher extension and higher cutoff so the xmax may not be an issue and u may need the higher resonance frequency

i thought a flat response from 50hz-400hz was only possible with a front loaded horn, in which case your in the wrong thread
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Old 17th June 2008, 04:25 AM   #1994
GM is offline GM  United States
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Quote:
Originally posted by obeman
Thanks GM, nice work..........

is there some formula for calculating mmd -as there seems to be quite a bit difference?

is it safe to assume 2 drivers with good enought match were to
work well with shared first horn part?
and that response could be simulated with "one half"?
You're welcome! Thanks!

Mmd is Mms minus the air load, but I don't know the formula. Since all the formulas I've seen use Mms, I don't understand why Hornresp uses Mmd.

Drivers sharing the same throat in a horn tend to average out somewhat due to the air mass loading, ergo in a tapped horn this would apply on both sides of the driver.

Why would you sim with 'one half' when you can sim two drivers? Anyway, ideally you'd measure both drivers and design based on their averaged specs, so don't understand why you're having problems simming two theoretically identical drivers.

GM
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Old 17th June 2008, 05:27 AM   #1995
GM is offline GM  United States
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Quote:
Originally posted by Naudio

i thought a flat response from 50hz-400hz was only possible with a front loaded horn, in which case your in the wrong thread
Not in theory. Consider this theoretical single 8" driver expo TH in half space coupled to an 8 W SET amp. It's no larger than some similar BW multiple 15" driver built in concrete horns I've seen pics of, so you can't say its size is untenable per se...........

GM
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Old 17th June 2008, 05:28 AM   #1996
GM is offline GM  United States
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z50-400 Hz expo TH response plot:
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Old 17th June 2008, 07:43 AM   #1997
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Quote:
Originally posted by GM
I don't understand why Hornresp uses Mmd.
Hi GM,

Hornresp uses Mmd because dynamic mechanical mass is a fundamental parameter of the driver, whereas Mms is a derived value. The air load on the diaphragm is calculated internally by the program as necessary. Mmd can be determined using the 'Calculate Parameter' tool if Sd, Cms and fs are known.

Kind regards,

David
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Old 17th June 2008, 11:17 AM   #1998
obeman is offline obeman  Finland
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Quote:
Mmd can be determined using the 'Calculate Parameter' tool
ah, of course. seems i did simulate with too large mmd, as guestimated air load to only couple of grams.


Quote:
try the eminence definimax
sure is better, but reason for this project to actually finish some day is that i already have these laying around, for a year now..

it seems this design doesn't need lot of excursion (apart those "impulses".. first periods of waves that i'm not so sure of..)
definimax is bit expensive where i can easily get it, and neo kappalite cheaper

plus, i need that high frequency extension because these will
form the bass part for zomax horns http://www.ljudia.se/pdf/211335.pdf that go no lower that 200-300hz.
gonna mate these with eminence apt-50 tweeters. have this funky idea.. kind of coaxial horn of putting tweeter right in front of mid, forming a tight throat of a ring shape with it's magnet, structure and horn itself.
this for getting highfreq cancellation as low as possible + high xover possible.


Quote:
Drivers sharing the same throat in a horn tend to average out somewhat due to the air mass loading, ergo in a tapped horn this would apply on both sides of the driver.
well, i'm kind of noob what comes to horns so... do i correctly assume that doupling driver surface (2 drivers) means doubling areas everywhere? might be wrong as i don't seem to get the frequencies match when simulating two.. this was the reason for simulating one half at a time.

with this.. 2 drives in V -shape -idea, i hope to smooth the high.
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Old 17th June 2008, 03:50 PM   #1999
GM is offline GM  United States
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Quote:
Originally posted by David McBean

Hornresp uses Mmd because dynamic mechanical mass is a fundamental parameter of the driver, whereas Mms is a derived value. The air load on the diaphragm is calculated internally by the program as necessary.

Mmd can be determined using the 'Calculate Parameter' tool if Sd, Cms and fs are known.
Greets!

OK, true, but it's normally derived also since it's very rarely published, so still not sure why you prefer it over the ~universally used Mms.

Understood, thanks, but I was hoping you'd publish the formula. Oh well, doing a bit of Googling yielded this from Bill Geiger:

[Mmd] = [Mms]-2*([Sd]^2)*[Ma1]

[Ma1] = 8*[p0]/(3*[pi]^2*[a]) - Acoustic Mass of Air Load on one side of equivalent piston (kg/m^4)

[p0] = 1.18 kg/m^3 - Air Density

[pi] = 3.14159

[a] - Driver Effective Radiating Piston Radius (m)

[Sd] = [pi]*[a]^2 - Driver Effective Radiating Area (m^2)

GM
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Old 17th June 2008, 04:20 PM   #2000
GM is offline GM  United States
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Quote:
Originally posted by obeman

........do i correctly assume that doupling driver surface (2 drivers) means doubling areas everywhere?
No, Sd has no bearing on speaker/horn design per se. Doubling drivers means doubling all dims of the horn due to a doubling of Vas to theoretically clone the single driver design, though wiring them in series will sum Le and halve it if wired in parallel, so there will be some performance variation from the single driver design that may require either adding a zobel filter or inductor.

GM
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