Collaborative Tapped horn project - Page 103 - diyAudio
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Old 19th January 2008, 09:57 PM   #1021
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got a link to that driver? What is the total volume for that design?
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Old 20th January 2008, 03:31 AM   #1022
Killjoy is offline Killjoy  United States
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Default Driver Specs

Here's the link: http://www.usspeaker.com/ciare%201500sw-1.htm.
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Old 20th January 2008, 03:32 AM   #1023
Killjoy is offline Killjoy  United States
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Default Ooops!

I forgot about the total volume question. The volume is 402L.
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Old 20th January 2008, 03:28 PM   #1024
tb46 is offline tb46  United States
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Hi,

Killjoy: The link to the Ciare 15" you modelled does not seems to work, and going on usspeaker.com the only Ciare 15" that is listed - Model 15.00SW - has considerabley different parameters. Must be a different model.

Anyhow, enclosed is the hornresp input and SPL for that speaker in your box dimensions. Obviously,it does not look smooth, but seems to be a good example to point out some of the tuning that may apply to the tapped horn in general:
1. Active high pass filter to prevent excessive cone deflection below the passband, and to control any low peaking (e.g.: in this case @ 21Hz),
2. Series passive filter element (L) to control the peaking @60Hz and to modify the speaker parameters. (As an aside, the Jensen Transflex paper recommended a 45hz 2nd order passive cross-over network.)
3. Tuned resonators to reduce the first few resonant peaks, maybe @ 94Hz, 150Hz, 235Hz, 330Hz.
4. Lining of parts of the horn walls to reduce the higher frequency hash.

I feel, that even if one does (obviously) a better job of speaker selection and box tuning, all of the above will apply to just about any tapped horn. Which, if nothing else, makes this quite a project to get right. This is really interesting.
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File Type: jpg usspeaker_ciare_15.00sw.jpg (73.6 KB, 780 views)
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Old 20th January 2008, 04:18 PM   #1025
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I dont think the peaks and nulls above the passband is such a big problem as Hornresp simulates. I cant hear any of the peaks as any kind of distortion when playing loud with my small tapped horn. If I realy had 10 dB higher efficiancy around the second and third harmonics of the bass coming out of the horn, it would sound terrible, but it dont. The bass is much cleaner and purer than any closed box/BR/BP i have ever heard. (of comparabel size)

Johannes.
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Old 20th January 2008, 05:59 PM   #1026
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@tb46: I have finally read the paper and it looks interesting, but for the moment I'll refrain from trying to model it in AkAbak. Since a TH Sub is mostly for a rather limited bandwidth I don't consider resonators an issue for extending the response.

I removed the "radiator" elements from my script above, as the only part that connects to the outside air is the mouth of the horn. (Why didn't I think of that earlier?)
The SPL plot is now what I would expect from a TH. The upper and lower knees of the passband are now clearly defined and the average sensitivity is as predicted in Hornresp.

However ... there is a broad dip over the passband that I don't have in the equivalent TH in hornresp. Since I'm using Hornresp as my reference, I'm wondering if this could be because of a difference in horn theory between AkAbak and Hornresp? Maybe someone can explain this?

for reference: here is my equivalent script in AkAbak:

-----------------------------------------------------------------


Def_Reflector TopCorner
Left=1.0m Top=1.0m Right=1.0m
HAngle=45.0°


Def_Driver 'SPH-212'
dD=21,2cm dD1=6,5cm tD1=2,5cm |Cone
fs=30Hz Vas=82L
Qms=2,21 Qes=0,5 Re=6,2ohm fre=8kHz Le=0.6mH




System 'RLDCTH'


Driver Def='SPH-212'
Node=1=0=200=300 |Driver connected to node 200 and 300


Duct 'FrontCompchamber'
Node=200=201 |driven by node 200 (front driver) and it drives/connects to node 201 (open end of resonator)
sD=0,206m2 Len=1cm Vf=0,1L




Duct 'Resonator' |80Hz one end closed resonator
Node=0=201 |def "resonator" with node 0 as closed end and connected to node 202
sD=0,206m2
Len=40cm


Waveguide 'Conical Horn'
Node=201=301 |Conical horn between nodes 201 and 301
STh=0,206m2 SMo=0,250m2
Len=300cm Conical


Duct 'BackCompchamber'
Node=300=301 |Driven by back of driver and drives/exits in the conical horn
sD=0,206m2 Len=1cm Vf=0,1L



Horn 'Endhorn'
Node=301 |Horn driven by node 301 (conical horn+output back comp chamber)
STh=0,250m2 SMo=1m2
Len=60cm T=1
x=0 y=0 z=0 HAngle=0 VAngle=0 dEdge=3m Reflection

---------------------------------------------------------------

With the SPL plot attached:
Attached Images
File Type: jpg th-akabak-spl.jpg (69.6 KB, 1244 views)
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Old 20th January 2008, 06:00 PM   #1027
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And here are the settings of the same horn in Hornresp:
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File Type: jpg th-hornresp-sett.jpg (65.5 KB, 1222 views)
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Old 20th January 2008, 06:02 PM   #1028
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and the Hornresp SPL plot:

Any ideas?
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File Type: jpg th-hornresp-spl.jpg (61.4 KB, 1250 views)
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Old 20th January 2008, 10:44 PM   #1029
tb46 is offline tb46  United States
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Hi,

Circlomanen: Thanks, that is very useful information, especially the comparison to other subs of similar size. Just like GM said:"...the 'ripple' isn't as bad as predicted...".

Cordraconis: I hope you had some fun with the Jakulis paper. In your script you have a number of area values as e.g.: STh=0,206m2 is that how AkAbak denotes cm^2? I think normally 206cm^2 would be 0,0206m^2, right? Anyway, you'll get me into AkAbak yet, as soon as the oil price falls and we're getting back to a sane work schedule around here (Texas).
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Old 21st January 2008, 02:20 AM   #1030
tb46 is offline tb46  United States
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Hi,
Don't know if anybody has already modeled the Mach 5 Audio MJ-18-8? It will fit into the same size as the DTS-20, with a relatively smooth response.
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File Type: jpg mach5audio_mj-18-8.jpg (72.8 KB, 1221 views)
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