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ROAR with Helmholtz front resonator
ROAR with Helmholtz front resonator
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Old 1st November 2018, 06:52 AM   #41
wonderfulaudio is offline wonderfulaudio  India
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Very nicely explained Circlomanen, thanks.
I know you already said that the overlaid graphs are only for understanding, but it looks like you tried to tune the Helmholtz so that the dip on the upper side could be filled, is it?

Also, do you think the Helmholtz could be tuned on the lower side of the pass band instead of the higher side?
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Old 1st November 2018, 08:26 AM   #42
Circlomanen is offline Circlomanen  Sweden
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TPBP10-1.JPG

TPBP-2.JPG

Quote:
do you think the Helmholtz could be tuned on the lower side of the pass band instead of the higher side?
No. The Helmholtz resonator is a low pass filter. You don´t want to filter away most of the passband.

See the simulation above. I substantially lowered the resonant frequency (low pass cut of frequency) of the front chamber + port in the second simulation.
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Old 1st November 2018, 09:21 AM   #43
Sabbelbacke is offline Sabbelbacke  Germany
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Quote:
Originally Posted by Circlomanen View Post
No. The Helmholtz resonator is a low pass filter.
Actually, A Hehlmholtz Resonator acts like a Bandpass.

Volume of the resonator, length of port and area of port are used to tune resonant frequency and Q of the Hehlmholtz.

In a simple Bandpass Cabinet (two adjanced volumes, driver in between, one volume closed, one with a port), the portet chamber is a Hehlmholz Resonator.

I assume you already knew
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Old 1st November 2018, 09:43 AM   #44
Circlomanen is offline Circlomanen  Sweden
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Actually, A Hehlmholtz Resonator acts like a Bandpass
With a large and short port it will pass anything below its bandpass resonant peak - inclusive pure DC (steady airflow) without any problem. But you are right, the resonant part of the Helmholtz resonator is a bandpass function. Thanks for pointing this out.

It makes it easier to explain when viewed as a lowpass function in this design, since the port is extremely acoustically permeable below its passband.
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Old 1st November 2018, 09:45 AM   #45
wonderfulaudio is offline wonderfulaudio  India
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Thanks again.

What do you think of adding a low pass filter the following way, its an attempt to low pass only the throat side of the driver.

The idea is that a normal TH is limited in bandwidth because the upper freq range is dominated by constructive/destructive interference similar to comb filtering. So, if the TH can be modified such that the throat side is low passed then interference can be avoided. The rear of the driver (mouth side) can go higher in frequency without being interfered by the throat side which is low passed now. The throat side is like a high tuned MLTL.
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Last edited by wonderfulaudio; 1st November 2018 at 10:06 AM.
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Old 1st November 2018, 10:06 AM   #46
Circlomanen is offline Circlomanen  Sweden
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8thROAR15-test.JPG

If you balance a ROAR with an added quarter wave front section between the driver and the front resonator then you can get a very wide usable bandwidth. I have no idea how it will sound in real life, but it does look nice in Hornresp.
It is basically an 8th order ROAR15.
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File Type: jpg 8thROAR10-crude.JPG (132.3 KB, 240 views)
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Old 1st November 2018, 10:07 AM   #47
wonderfulaudio is offline wonderfulaudio  India
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You replied before I could attach the image
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Old 2nd November 2018, 12:21 PM   #48
martinsson is offline martinsson  Sweden
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Quote:
Would someone be so kind to write the full acronym ROAR? I try to deduce it but it is impossible for me ...
Answering it as the other responsible part of the way this came to be, as Johannes pointed out it started as a bit of a joke but it got stuck, but trying to find something more straight forward and deductible as THAM (Tapped Horn Anders Martinsson) proved extremely challenging in the case of a series tuned 6'th order quarter wave design, or tapped pipe + quarter wave resonator which I feel describes it better.

After having spent a lot of time and many notes on trying to arrange the letters describing the design in right way without having it spelling out something sounding like a medical condition I finally gave up and started approaching it in another way.

So I took Johannes surnames first to letter, RO, and I wanted the R from Resonator in there somewhere, and that is was something different, something alternative, and using the same number of letters as THAM, the result was - ROdin Alternative Resonator (...I never said it was really thought trough)

Less known fact, ROAR in Swedish means to entertain, having fun, by example:
Artisten roar publiken (The artist is entertaining the audience)
Or:
Han roar sig med att... (He's having fun doing...)

Now He's gone and added a Helmholtz resonator function to the ROAR... so where do you put the H, you won't be replacing the R that's for sure, and thank god there was not a Waveguide in his plans as well

I'll gladly hand over the task of finding a name for this one over to Johannes
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Old 3rd November 2018, 07:06 PM   #49
BP1Fanatic is offline BP1Fanatic  United States
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Lol!
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Old 11th January 2019, 02:38 PM   #50
bjohng is offline bjohng  United States
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"I am not done evaluating the first single driver version yet"

Are you still as enthusiastic and planning to try a 2 driver unit?

Maybe just satisfied with original 1 driver performance.

Conventional BR speakers do not work in my acoustically challenging room and I am one of those people who can instantly detect a ported speaker. If history is a guide I would need to build 2 units.

Two MCM 2421s in hand ready to go. Having said that there is no way I could tackle Hornresp to arrive at final dimensions.

Thanks.
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