While reading your post this morning my wife actually came up to me and asked, could you put a very sharp point on this pencil, and handed me a pencil and sharpener, spooky or what 😱
She has this thing about sharp pencils, it's got to be sharp!
Steve.
I am about to re-read G A Briggs book on Loudspeaker 5th edition 1958.
Its been a few years since I last read this book ,its full of great ideas and a joy to read, such enthusiasm.
I don't remember anything in the book about sound boards though.
But I do remember something in the book about a free edged cone speaker from about 1930 that he was very impressed with,(a free resonating cone?)
Sounds familiar?
Steve.
Its been a few years since I last read this book ,its full of great ideas and a joy to read, such enthusiasm.
I don't remember anything in the book about sound boards though.
But I do remember something in the book about a free edged cone speaker from about 1930 that he was very impressed with,(a free resonating cone?)
Sounds familiar?
Steve.
Comments on the sub....The most interesting part of Ammos product is the triangular down-firing woofer box, rather than the glass sheet protruding above, when I think about it more and more. True, the up-firing two actuators/transducers firmly touching 4mm glass sheet became the subject of interest due to our DML interest here, so few experiments with up-firing transducer with different materials. Sony, by the way, showed that a top closed glass (or similar) tube gives omni sound with at least 3 up-firing actuators under the edge. Two actuators connected to two stereo channels gave quite full room filling sound when a tall drinking glass was held tightly over them at opposite edges. I placed a heavy book over the drinking glass, so I can take my hands of it, so walk around. Well, anyone who has two actuators can do this experiment. Tall drinking glasses and heavy books are normally available.
Now, as I mentioned above, the triangular down-firing woofer box became the subject of interest. You see, instead of "actuators" there could be two smallish tweeters placed just under the open groove, and that triangular box becomes a speaker. The space below the tweeters can be sealed so whatever back sound would only go through the curved bass-reflex tube.
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That woofer is a cleverly-hidden series-tuned double-manifold bandpass design (I think Bose held the patent for it until a decade or so ago.)
In effect, the cone is firing into two tuned chambers. The back side of the woofer feeds into the pyramid on top, which is one chamber. And looking at the size of that port, I'd assume it's probably tuned to the lower cut-off frequency (20Hz is very ambitious metinks.) The face of the woofer fires into another tuned chamber which consists of the space between the "feet." That space—the chamber between the the feet and formed by the baffle, the feet and whatever surface it rests on—will be tuned to the upper cut-off frequency (200Hz.)
I built a similar downward-firing 15" double-chamber sub-woofer in the 1990's, also with the lower chamber defined by the feet and the surface it rests on.
Here's a basic schematic. The lower port (firing to the right) is formed by the spaces between the feet of the Ammos system.
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Did you show your wife the photo of the grinding wheel and pencil when it happened? I bet she'd be like: Now that's what I'm talkin' about!
My wife bought this perspex frame some years ago to hold the grandchildrens drawings.
I'm not that keen on the sound of perspex, but have always thought this frame could easily be converted into a computer speaker or TV surround sound speaker.
I would have tried this by now, except my wife would probably notice it is missing and give me ear ache ☹️
But I thought some might find this interesting for an easy project.
Steve.
I'm not that keen on the sound of perspex, but have always thought this frame could easily be converted into a computer speaker or TV surround sound speaker.
I would have tried this by now, except my wife would probably notice it is missing and give me ear ache ☹️
But I thought some might find this interesting for an easy project.
Steve.
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So when I made my ported downfiring subs each with four feet, I inadvertently made a double manifold bandpass system...omg.. 😱...😜
Chdsl.
Thank you very much for the book link.
Quite a bit is lifted from my Loudspeaker book.
And I noticed while quickly browsing through, that on page 175 there is a drawing of an acoustic resonator, which is so close to a dml panel design.
If only he had use a different material without holes.
Steve.
Thank you very much for the book link.
Quite a bit is lifted from my Loudspeaker book.
And I noticed while quickly browsing through, that on page 175 there is a drawing of an acoustic resonator, which is so close to a dml panel design.
If only he had use a different material without holes.
Steve.
If you can dismantle a old photo frame, you'd get 2 or 3 mm glass panel, would you try that, the normal way and up-firing touching the edge? You'd have to hold the panel very tightly over the exciter/actuator.
I do like them ;-) but folded or otherwise, transmission lines make a physical impression.
Since I came across Nelson Pass's El Pipe O, I always scan construction sites in Manhattan to see if I can pick up a couple of sonotubes.
They would most likes get followed by divorce papers, but a man can dream.
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Taking anything as encouragement, I subtly and quietly placed a pair of DML TV surround speakers on the back wall of my listening home theater room.
I have an old Hypex FA123 - its companion (long out of warranty) has failed ;-( I've started to repurpose it into a new case | form-factor to drive these.
The new configuration uses a pair of 12" heat sinks from Heatsink USA (that I had tucked away) as sides, most of the face plate of the FA123 as a bottom, and rearranges the input DSP | DAC module. Overkill for its use. I'd just as soon simplify this amp build|reconfiguration to just use the Hypex stereo NC-MP122 board with only analogue inputs, but not certain I can get the little bits and info I need to make it work.
This new amp configuration will hide neatly in the cabinet below the window.
DMLs + Class D amps make "secret sound" possible.
