First I will wish al the people here a fantastic, peacefull, healthy, musical, amplified (something forgotten?) 2013, we stil here after 21 december 2012.
Oke, I hav started the cardioid bas approach, well, I do like it because it looks that the sound has a sound like a horn does.
I have made a U frame and a panel with sleeves covered by cloth.
I did play a 30 hz tone, well very strange back in the chamber not much bass, but on front I did feel it very strong, but the hous don,t chake behind the box, but well from the front, so I have a first attemt who works, If I look to the impuls on the measurement it is 180 degree out of fase but sound is shifted? the bass is very good with such small box, I do use visaton wsp26s 10 inch woofers in a U frame two stacked above each other.
Measurements left is without a acoustical resistor, just a U-frame, right is with the acoustical filter.
oke, some thoughts of you maybe you see some strange things, maybe I miss something but the graph looks very good, Ooo yes there is a low pass filter on the box as you see on the graph
You might want to have a moderator move this to the subwoofer section, since you are using a cone driver.
That being said, to achieve a cardioid response with only acoustic resistance is difficult below 200Hz. You need lots of material. How thick is the material you are using? I would think you may need at least 6-8" of good absorptive material to get enough resistance for low bass resistance. What are the blue and red lines in the right graph. I think maybe those are with and without the resistor vent? We found that it takes at least 12" of Bonded Logic brand acoustical recycled cotton to do much down at 50Hz. Thanks for sharing.
Oke, happy newyear .
The red line is from the back, and the blue is form the front, the first with only blue line is a open u frame, two stacked, is not so important but you see the differends with the resistor...
I have a panel with sleeves first and then clotch of 2.5 mm thick, only clotch or cotton is not enough, a panel with sleeves first and the cotton on it..
the NAO site has something like that and so I thought I go try that also.
But I think a good horn is de best cardioid, I am not disapointed about the bas of this box, it can go to 30 hz for so small thing.
I have to deepen the box to 60 cm I have sleeves who give a 100 x sd, I do notice that the bass now is more on front and not back at the room anymore.
The graph is a sweep with a low pas filter on the bas speaker going down from 120 hz.
This site has something about it, the sleeves in the box I also did use for me on the back with a double u frame.
I do like open systems, so 4 18 inch woofers in a w frame looks good, but I do one at the time afcourse, the first are H frames who did really good.
if you look to the impuls graph section you see 180 degree faseshift, so it looks that the resistor do not work enough.
In above Impulse Responses, is time axis distance or milliseconds? What is strong reflection at t=35?
Resistor approach is difficult. I've gotten cardioid response by stacking monopole on top of 'U' frame dipole.
Premiss in Cardioid bass is highly flawed, certainly for domestic listening spaces. Group delay presentation only shows how temporally messed up listening space is.
Dumping about the same amount of energy into the room in slightly different ways doesn't improve matters much in listening area.
My cardioid setup has similar frequency response as yours prior to EQ:
And the group delay plot shows that temporal chaos is manifest:
Complex EQ is derived from response measurement, and is used as digital filter to restore order:
And the frequency response is likewise smoothed:
Same results are possible with just monopole or dipole.
The reflextion on t 35 is the room itslef and feedback of microphone, ringling of stuff in it while measuring, I have also a H frame here in the room my first project, I think that I do soon for 4 x 15 inch w frame, as test, with this bass get very relaxed and deep, but for now first the acoustical testing what is very interesting.
The H frame measurement with the same speakers wsp26s from visaton 19 hz res qts 0.34
Blue line, is back off the H frame, red line is front of the H frame and green is the acoustical resistance U frame.
I have before I did use the cloth damping panel make a panel with sleeves as a resistor
who I can put that cloth on 2.5 mm thick, and so more and more while measuring but first I have to make the u frame longer it is to short with 35 cm deepness.
The best way for cardioid is two closed boxes with the back against each other one speaker 180 degree out of fase and the use of a fase shift alpass bessel filter, or maybe just only one 12 db low pass filter and one 18 db low pass filter.
My idea about the cardioid is my small room, for a H fram she are a little to big, but if I do reorder the room I think that it is easy to do, setting the tv for the window part seeing the length of the room of 7 meters.
I have measure again now with a deeper u frame of 58 cm, and some more stuffing, but not more cloth in the acoustical filter, that I do doe later.
20 hz it is here, everything shakes even on low volume, but now i now that is not needed if you don,t play church organs.
red line is the back and the blue line is the front of the box with mike close to the conus.
so I learn more and more with playing.
Oke, noy I have put 4 sheets of cloth damping on the sleeved pannel.
And measure it, if I listen then at the back there is a little bass and on the front
a lot, oke, not proof for a cardioid I think.
The bas is very good, tight, punchy, and easy, fall of begins on 30 hz, that is very low I can let a candleflame fibrate on 25Hz even with low volume.
have tree programs tryed for measurement, just one I do like, holmimpulse I like arta and the best is true rta. Holmimpulse give a strange outcome in the lower bas region if mid and high are also connected, measruring with only bas give a much better result. true rta give a very acurate outcome.
The wild respons is from my room, just a little alignment of the mike, give a far other outcome, I have to measure in a dead room what I don,t have, only outdoors is possible but it rains here every day so.
I have stopped the leaking box, I have build a dipole a la linkwitz, this is small, and work better and special deeper bass, the woofers with a fs of 19 hz did not wel in a ripole less spl each watt.
so this tread can be locked.
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