Hi, thanks!
The MAF was kind of a mind experiment, I wanted to see whether there is some controversy or some obstacle that prevents it from being able to work. It was quite fun to discover that such a simple device is actually on hand for virtually anyone who is able to handle scissors, pliers and a tube of glue.
It addresses this article:
"A cabinet of reduced size with better low-frequency performance Wireless World, February 1956." http://www.ejjordan.co.uk/PDFs/A-Cabinet-of-Reduced-Size-with-Better-Low-Frequency-Performance.pdf
From: E.J.Jordan Designs - book & articles design & consultancy
And this is the ARU:
The OB project is a one that I follow, not vice versa. I only set the goal and after that I go after the design. The goal is 20 hz on not less than -3db. I have achieved 20 hz @ -1.8 db and 18 hz@ -3 db with the Dayton in the big bass cabinet and 112 db from 19.5 hz on. This is medium stuffed 200L tuned to 19 hz. If you ask me, I would go for 4 15's per side 😀 but the space allows only for one big cabinet per side. I chose the Daytons for their ability to go low effortlessly. - see the attached measured T/S, taken after 72 hours of break in.
First big challenge became the crossover, I wanted passive @ 70-100 hz, but it introduced enormous anomalies in the SPL vs frequency response. Anyway, crossover is another story.
Then it was the OB, it sings beautifully, no anomalies around crossover or whatsoever, it even goes so low, that it is actually a fullrange system on it's own. But it betrayed me on the high frequencies. The Tangband is notorious for it's lack of refinement in the last octave (10 to 20 khz), I initially intended to mend that with the small 2 inch paper HF drivers (eight per side). But those although having very sweet sound in the last octave, were not able to supply the required SPL, they never got over 86-87 db/w/m (this is four firing forward) and the system in not less than 88-90 db efficient. And on top of that, finding decent crossover solution between the TB and the HF drivers was a real pain.
Now I consider a Fostex or a Jordan instead the TB and an omnidirectional super tweeter. A more efficient extended range driver would allow me to wire the two 12 woofers (although they serve as a midbass-midrange, they have an Fs of 25-30 hz) in series for 16 ohm impedance (better damping) and 91 dm/w/m while removing the 3.3 ohm resistor from the crossover which leads to better damping too.
Or I could leave the 12's in parallel for 97 db/w/m and put a compression driver in between thus loosing the dipole action above 1.5 khz.
Another problem is the 0.75 mh inductance of the TB, it's too much. The Zobel network that is required for a LR-2@1255 hz to work properly uses a bigger capacitor than the one in the crossover, this robs high frequencies further and reduces efficiency. - I could use any advice on this.
Anyway, max SPL is not a target, 112 db is enough for me and as it seems the system will use two amplifiers, so the different efficiency will not be a problem.
As for the vacuum cleaner powered air meter, a prototype is coming 😀 stay tuned 😀
Best regards.
The MAF was kind of a mind experiment, I wanted to see whether there is some controversy or some obstacle that prevents it from being able to work. It was quite fun to discover that such a simple device is actually on hand for virtually anyone who is able to handle scissors, pliers and a tube of glue.
It addresses this article:
"A cabinet of reduced size with better low-frequency performance Wireless World, February 1956." http://www.ejjordan.co.uk/PDFs/A-Cabinet-of-Reduced-Size-with-Better-Low-Frequency-Performance.pdf
From: E.J.Jordan Designs - book & articles design & consultancy
And this is the ARU:
An externally hosted image should be here but it was not working when we last tested it.
The OB project is a one that I follow, not vice versa. I only set the goal and after that I go after the design. The goal is 20 hz on not less than -3db. I have achieved 20 hz @ -1.8 db and 18 hz@ -3 db with the Dayton in the big bass cabinet and 112 db from 19.5 hz on. This is medium stuffed 200L tuned to 19 hz. If you ask me, I would go for 4 15's per side 😀 but the space allows only for one big cabinet per side. I chose the Daytons for their ability to go low effortlessly. - see the attached measured T/S, taken after 72 hours of break in.
First big challenge became the crossover, I wanted passive @ 70-100 hz, but it introduced enormous anomalies in the SPL vs frequency response. Anyway, crossover is another story.
Then it was the OB, it sings beautifully, no anomalies around crossover or whatsoever, it even goes so low, that it is actually a fullrange system on it's own. But it betrayed me on the high frequencies. The Tangband is notorious for it's lack of refinement in the last octave (10 to 20 khz), I initially intended to mend that with the small 2 inch paper HF drivers (eight per side). But those although having very sweet sound in the last octave, were not able to supply the required SPL, they never got over 86-87 db/w/m (this is four firing forward) and the system in not less than 88-90 db efficient. And on top of that, finding decent crossover solution between the TB and the HF drivers was a real pain.
Now I consider a Fostex or a Jordan instead the TB and an omnidirectional super tweeter. A more efficient extended range driver would allow me to wire the two 12 woofers (although they serve as a midbass-midrange, they have an Fs of 25-30 hz) in series for 16 ohm impedance (better damping) and 91 dm/w/m while removing the 3.3 ohm resistor from the crossover which leads to better damping too.
Or I could leave the 12's in parallel for 97 db/w/m and put a compression driver in between thus loosing the dipole action above 1.5 khz.
Another problem is the 0.75 mh inductance of the TB, it's too much. The Zobel network that is required for a LR-2@1255 hz to work properly uses a bigger capacitor than the one in the crossover, this robs high frequencies further and reduces efficiency. - I could use any advice on this.
Anyway, max SPL is not a target, 112 db is enough for me and as it seems the system will use two amplifiers, so the different efficiency will not be a problem.
As for the vacuum cleaner powered air meter, a prototype is coming 😀 stay tuned 😀
Best regards.
Attachments
Hi to all, it's been a while since my last post.
So to end that one thread that I consider prototyping, here are a few photos of all the pieces in one place.
I will start a new thread for the finished thing and it's crossover.
The drawing is over four years old and it actually came in a dream, I got up and put it to paper. Although it is not god's deed, but rather the conclusion of allot of reading and thinking. I read Linkwitz and Martin King for days before that and was thinking of a way to have acoustical source that is really independant of the room and especially in the midrange. It was on my mind just it didn't want to go out in the evening 🙂
So here it is, wide baffle with three open edges, 4 way, super tweeted and subwoofered 16 Hz to 200 KHz.
It does not have a "18, because those "15's were the only 0.28 Qts 16.6 Hz Fs drivers I found. The boxes allow "18's and I have a router so if one day I come across decent "18's...
I listened to the tops standing on the sides only without the subs for half a year and they sound great. I took some measurements too.
I am very proud! And please consider I am attorney at law 🙂
So to end that one thread that I consider prototyping, here are a few photos of all the pieces in one place.
I will start a new thread for the finished thing and it's crossover.
The drawing is over four years old and it actually came in a dream, I got up and put it to paper. Although it is not god's deed, but rather the conclusion of allot of reading and thinking. I read Linkwitz and Martin King for days before that and was thinking of a way to have acoustical source that is really independant of the room and especially in the midrange. It was on my mind just it didn't want to go out in the evening 🙂
So here it is, wide baffle with three open edges, 4 way, super tweeted and subwoofered 16 Hz to 200 KHz.
It does not have a "18, because those "15's were the only 0.28 Qts 16.6 Hz Fs drivers I found. The boxes allow "18's and I have a router so if one day I come across decent "18's...
I listened to the tops standing on the sides only without the subs for half a year and they sound great. I took some measurements too.
I am very proud! And please consider I am attorney at law 🙂
Attachments
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