You can simulate it with AkAbak. ... When I say "you", I mean someone like me or xrk971... 🙂
Maybe some day I'll toy with AkAbak. Getting my MA is a (slightly) higher priority for next few months than this hobby. In the meantime y'all can be "taken aback" by my nutty ideas 🙂
Normally when you use the same drivers in an array you expect them to take back some of the control, with each location playing its part. When the drivers are not in cooperation it is no longer a stamdard array.
I suppose if you wanted to match up the response differences between the lines, with a location for each that complements the room.. but it's just a theory. At least it suggests that a non standard line may not be 'incorrect'. Just outside the box.
There's no reason an array needs to be just a line, it can work horizontally too. Keele has some info on this somewhere on this page.
I suppose if you wanted to match up the response differences between the lines, with a location for each that complements the room.. but it's just a theory. At least it suggests that a non standard line may not be 'incorrect'. Just outside the box.
There's no reason an array needs to be just a line, it can work horizontally too. Keele has some info on this somewhere on this page.
For anyone who is interested in building one ("Dear Lord, why?" query the elders in this forum), here is a slightly more detailed of the build of the Marimba I:
Drivers: 9x "original" Bose 901 (CTS drivers or similar from "brand x" clone);
9x transmission lines made of free cardboard tube (from carpet store); each tube is cut to a length as follows (in cm.):
114, 104.5, 95, 85.5, 76, 71.25, 66.5, 61.75 and 57.
The (ir)rationale for these lengths is explaiend elsewhere.
The tubes are mounted vertically, longest at base and decreasing lengths, so that the nine drivers are in a line array. Any type of frame could be made. Mine was very simply (2) 2"x4"x8', cut in half, and therefore two pair of vertical supports. The base is expected to be a 4' of 2"x6". Each unit was assembled on its side using nothing but Gorilla Glue for connecting parts together. Looks like crap, oozes, but works very well, rarely comes apart yet can be disasembled and scraped off if needed.
It's entirely possible more parts will be added.
Electrical connections: I made each tube have its independent set of leads coming out the side. Many modes of hook-up are possible, but I intend to follow the Bose wring of 3 speakers in series ( = 24 ohm) and then parallel these ( = 8 ohm).
How will it work? No idea. I will report and even give some measure ments -- later.
Drivers: 9x "original" Bose 901 (CTS drivers or similar from "brand x" clone);
9x transmission lines made of free cardboard tube (from carpet store); each tube is cut to a length as follows (in cm.):
114, 104.5, 95, 85.5, 76, 71.25, 66.5, 61.75 and 57.
The (ir)rationale for these lengths is explaiend elsewhere.
The tubes are mounted vertically, longest at base and decreasing lengths, so that the nine drivers are in a line array. Any type of frame could be made. Mine was very simply (2) 2"x4"x8', cut in half, and therefore two pair of vertical supports. The base is expected to be a 4' of 2"x6". Each unit was assembled on its side using nothing but Gorilla Glue for connecting parts together. Looks like crap, oozes, but works very well, rarely comes apart yet can be disasembled and scraped off if needed.
It's entirely possible more parts will be added.
Electrical connections: I made each tube have its independent set of leads coming out the side. Many modes of hook-up are possible, but I intend to follow the Bose wring of 3 speakers in series ( = 24 ohm) and then parallel these ( = 8 ohm).
How will it work? No idea. I will report and even give some measure ments -- later.
Not half bad...
I ran a set of three full range sweeps this morning and the results are not too bad...
I get reasonably flat response down to maybe 72 Hz (-3 db) ... response is MOL flat to 2K and then falls off (that is normal for 901's with no EQ). This pretty good for a driver that has an fs of about 106 Hz.
Selected graphs below.
I ran a set of three full range sweeps this morning and the results are not too bad...
I get reasonably flat response down to maybe 72 Hz (-3 db) ... response is MOL flat to 2K and then falls off (that is normal for 901's with no EQ). This pretty good for a driver that has an fs of about 106 Hz.
Selected graphs below.
Attachments
Here is the horror itself 🙂
An externally hosted image should be here but it was not working when we last tested it.
A review, sort of...
Review of Soldermizer Technology Marimba Mark I
This is the first time that your review has had the opportunity to review a product from this new manufacturer. ST's produces, or as they like to say, "perepetrate" hand-built sound producing apparatus for the gullible public.
The Marimba I is the first in an envisioned line of speakers that ST plans to name after musical instruments. They chose "Marimba" due to the unconventional use of tubes behind each driver, much like the Mexican malleted instrument of the same name. But there the resmblance ends. Rather than wood, plastic or metal that higher manufacturers would use, ST scouts out old cardboard tubes that are left-overs at carpet dealers. These tubes, ST claims, have the "sonic smoothness" of the textile they previously were wrapped in. Particularly sought-after are those that were the core of Berber carpet, as wool is known to have exceptional audio properties.
In the same tradition of careless component selection, ST's employees (primarily day laborers sober enough to show up for work) are sent to scour local thrift shops and yard sales for authentic Bose 901 speakers. Not just any, but the originals having the coveted CTS drivers, long out of production. Rarely, NOS versions will surface from a collector but at $20-30 each, these are beyond the reach of the typical ST hiree. In a pinch, ST will use current production full range units but their superior specs, they claim, lack the tweet and blast that authentic CTS were known for.
The cabinet: as much respect as ST had for the late Dr. Bose and his hugely successful company, the Marimba I has little in common with the Bose 901 save using nine identical or similar drivers, but also vast EQ.
ST hit upon the apparently unique, or unwarranted, depending upon whom is condeming their latest product, idea of having a Direct/Directing [tm] vertical array of nine drivers closely spaced. Not just a line array, each driver also has a tube (quarter wave transmission line) behind it, tuned to a different frequency. While critics can validly claim that all but the "center" tube is mis-tuned (to maximize bass from the driver having an FS of approximately 106 Hz), ST decided to try and "fill the hole", which is the Achillie's Heel of QWT designs: the nulls at higher mutiples of the resonant frequency of each tube. ST believes that by having 4 tubes spanning the half octave below and above, respectively, that the peaks and nulls will be spread about and minimized.
Many minutes of design went into the planning for this reproducer. It was carefully assembled using the above materials, plus 16 feet of 2x4 for supports and 4' of 2x10 for a base. Gorilla Glue is applied liberally to keep stuff from moving about (although ST claims to have found the speaker works better if this adhesive stays out of the voice coil.)
Amazingly, ST's half-baked design appears to work. Initial testing shows reasonably flat response down to 71 Hz, substantially lower than a stock Bose 901. While not a true line source, ST's Direct/Defective [tm] rear sound wave is actually an unruly mix of out of phase frequencies. Like the Bose 901, this sound is intended to spread to the rear walls and rebound towards the listener.
Listening Tests.
Equipment break in. To test such an unsual speaker, equipment of comparable quality is needed. Your reviewer had to to pack up his Levinson and Madrigal electronics and inquire discreetly for more conventional equipment. Through his son, a herion addict in a punk band, he was able to borrow some Behringer electronics for the auditioning. In a pinch Pyle may also work.
Reviewer break-in. Prior to listening, your reviewer drank a "40" of malt liquor. A twelve pack of Natural Ice was in the fridge if additional protection was required.
Impressions:
Without EQ, the speaker clearly has lower bass than the 901 stock. However, the upper end is lacking, as is reasonable, in fact, the high roll off is identical to 901 box with no EQ.
With proper EQ however, is where the Marimba really begins to show its ordinariness. Many speakers are sensitive to placement, and the Marimba is no exception. Just being a line array demands a small sweet spot. However, the rear ports, which are in effect nine TL outputs, will combine unpredictably depending upon the room acoustics. Even small movements of a few inches dramatically change the timbre of the music. Perhaps this is to be expected, since in the case of one speaker set, there are nine in-phase signals vying to peak or null with nine more or less random signals and the results are very unpredictable.
Stereo imaging: not tested, as only a single Marimba exists currently.
Disposal: the Marima is made mostly of environmentally friendly material. It is best destroyed by burning. However, the Bose drivers contain lead (and Bose) and should be removed and handled as hazardous waste.
Review of Soldermizer Technology Marimba Mark I
This is the first time that your review has had the opportunity to review a product from this new manufacturer. ST's produces, or as they like to say, "perepetrate" hand-built sound producing apparatus for the gullible public.
The Marimba I is the first in an envisioned line of speakers that ST plans to name after musical instruments. They chose "Marimba" due to the unconventional use of tubes behind each driver, much like the Mexican malleted instrument of the same name. But there the resmblance ends. Rather than wood, plastic or metal that higher manufacturers would use, ST scouts out old cardboard tubes that are left-overs at carpet dealers. These tubes, ST claims, have the "sonic smoothness" of the textile they previously were wrapped in. Particularly sought-after are those that were the core of Berber carpet, as wool is known to have exceptional audio properties.
In the same tradition of careless component selection, ST's employees (primarily day laborers sober enough to show up for work) are sent to scour local thrift shops and yard sales for authentic Bose 901 speakers. Not just any, but the originals having the coveted CTS drivers, long out of production. Rarely, NOS versions will surface from a collector but at $20-30 each, these are beyond the reach of the typical ST hiree. In a pinch, ST will use current production full range units but their superior specs, they claim, lack the tweet and blast that authentic CTS were known for.
The cabinet: as much respect as ST had for the late Dr. Bose and his hugely successful company, the Marimba I has little in common with the Bose 901 save using nine identical or similar drivers, but also vast EQ.
ST hit upon the apparently unique, or unwarranted, depending upon whom is condeming their latest product, idea of having a Direct/Directing [tm] vertical array of nine drivers closely spaced. Not just a line array, each driver also has a tube (quarter wave transmission line) behind it, tuned to a different frequency. While critics can validly claim that all but the "center" tube is mis-tuned (to maximize bass from the driver having an FS of approximately 106 Hz), ST decided to try and "fill the hole", which is the Achillie's Heel of QWT designs: the nulls at higher mutiples of the resonant frequency of each tube. ST believes that by having 4 tubes spanning the half octave below and above, respectively, that the peaks and nulls will be spread about and minimized.
Many minutes of design went into the planning for this reproducer. It was carefully assembled using the above materials, plus 16 feet of 2x4 for supports and 4' of 2x10 for a base. Gorilla Glue is applied liberally to keep stuff from moving about (although ST claims to have found the speaker works better if this adhesive stays out of the voice coil.)
Amazingly, ST's half-baked design appears to work. Initial testing shows reasonably flat response down to 71 Hz, substantially lower than a stock Bose 901. While not a true line source, ST's Direct/Defective [tm] rear sound wave is actually an unruly mix of out of phase frequencies. Like the Bose 901, this sound is intended to spread to the rear walls and rebound towards the listener.
Listening Tests.
Equipment break in. To test such an unsual speaker, equipment of comparable quality is needed. Your reviewer had to to pack up his Levinson and Madrigal electronics and inquire discreetly for more conventional equipment. Through his son, a herion addict in a punk band, he was able to borrow some Behringer electronics for the auditioning. In a pinch Pyle may also work.
Reviewer break-in. Prior to listening, your reviewer drank a "40" of malt liquor. A twelve pack of Natural Ice was in the fridge if additional protection was required.
Impressions:
Without EQ, the speaker clearly has lower bass than the 901 stock. However, the upper end is lacking, as is reasonable, in fact, the high roll off is identical to 901 box with no EQ.
With proper EQ however, is where the Marimba really begins to show its ordinariness. Many speakers are sensitive to placement, and the Marimba is no exception. Just being a line array demands a small sweet spot. However, the rear ports, which are in effect nine TL outputs, will combine unpredictably depending upon the room acoustics. Even small movements of a few inches dramatically change the timbre of the music. Perhaps this is to be expected, since in the case of one speaker set, there are nine in-phase signals vying to peak or null with nine more or less random signals and the results are very unpredictable.
Stereo imaging: not tested, as only a single Marimba exists currently.
Disposal: the Marima is made mostly of environmentally friendly material. It is best destroyed by burning. However, the Bose drivers contain lead (and Bose) and should be removed and handled as hazardous waste.
I thought of something like this before, but it involved varying TL lengths with a driver, such that the cross sections summed to proper low freq loading of the single speaker. But quite frankly I don't know enough about it all to do anything with it, so i stick to my 3-ways.
Wesayso: If you say so 🙂 Realistically, I will play with the current 9-unit assemby for a while until I tire of it. I am more likely to build a 2nd 9-unit array and listen in stereo. After that who knows?
Also, for me a major problem in building a floor to ceiling array is that I have a sloping roof: shall the array be 8 feet or 13 feet high ?
Res07njc: your idea sounds like a variation of what is discussed in this thread (where I got the idea to try multiple independent but identical drivers in each its own TL).
http://www.diyaudio.com/forums/full-range/263354-dual-triple-tuning-tl-horn-bad-idea.html
Nor do I know enough about it, it makes common sense that multiple joined air columns driven by a single source will resonate somehow, but beyond that I don't know the math (nor care). I can't believe that my "Marimba" idea is all original, just new to me 😀
I like playing at the hobby of speaker building as well as writing about it. Sometimes it's a good idea to ignore the experts and find out for yourself. They can be (rarely) wrong.
Silly stereo glossary for today:
On-axis: when you are directly facing the front of the speaker (0 degrees);
Off-axis: describes the frequency response off to the sides of the speaker, usually a drop off in the high frequencies;
Abraxas: you are listening to a 1970 Carlos Santana album 🙂
Also, for me a major problem in building a floor to ceiling array is that I have a sloping roof: shall the array be 8 feet or 13 feet high ?
Res07njc: your idea sounds like a variation of what is discussed in this thread (where I got the idea to try multiple independent but identical drivers in each its own TL).
http://www.diyaudio.com/forums/full-range/263354-dual-triple-tuning-tl-horn-bad-idea.html
Nor do I know enough about it, it makes common sense that multiple joined air columns driven by a single source will resonate somehow, but beyond that I don't know the math (nor care). I can't believe that my "Marimba" idea is all original, just new to me 😀
I like playing at the hobby of speaker building as well as writing about it. Sometimes it's a good idea to ignore the experts and find out for yourself. They can be (rarely) wrong.
Silly stereo glossary for today:
On-axis: when you are directly facing the front of the speaker (0 degrees);
Off-axis: describes the frequency response off to the sides of the speaker, usually a drop off in the high frequencies;
Abraxas: you are listening to a 1970 Carlos Santana album 🙂
Why deny it?
Please Sir, may I have some salt in the wound? Here, I'll pull the knife out for you 😱
Yes, just average (let's be optimistic!) On the upside, here are some positive aspects of what I am doing:
Using very cheap and easy to work with materials, I can construct a a prototype of a speaker idea I have. If it fails, I have lost perhaps $50 in materials and several hours of tinkering time. Traditional speaker builder would insist on using $20,000 worth of wood shop equipment, carpentry skills the average hobbyist lacks and CAD designed three-dimensional building plans that would be the envy of Chinese puzzle box creators 😀
The last bit is not entirely faceitious: in the admittedly improbable event that I create a workable prototype, then the design can be turned over to the craftsmen who can build a $2,000 cabinet out of teak, walnut and ivory
Please Sir, may I have some salt in the wound? Here, I'll pull the knife out for you 😱
Yes, just average (let's be optimistic!) On the upside, here are some positive aspects of what I am doing:
Using very cheap and easy to work with materials, I can construct a a prototype of a speaker idea I have. If it fails, I have lost perhaps $50 in materials and several hours of tinkering time. Traditional speaker builder would insist on using $20,000 worth of wood shop equipment, carpentry skills the average hobbyist lacks and CAD designed three-dimensional building plans that would be the envy of Chinese puzzle box creators 😀
The last bit is not entirely faceitious: in the admittedly improbable event that I create a workable prototype, then the design can be turned over to the craftsmen who can build a $2,000 cabinet out of teak, walnut and ivory
Basic speaker testing using REW...pointers?
If I am unable or unwilling to build a quality speaker and I have much evidence against me 🙁
How about doing some basic speaker tests? If nothing else, for this present exercise, how about comparisons of the Marimba vs. its nearest competitor (no, not the toilet, but a Bose 901 series II)?
I have a PC + REW + mic and know the basics of REW. I am new to impedance testing but it has value too, although I'm not totally understanding of it.
If I am unable or unwilling to build a quality speaker and I have much evidence against me 🙁
How about doing some basic speaker tests? If nothing else, for this present exercise, how about comparisons of the Marimba vs. its nearest competitor (no, not the toilet, but a Bose 901 series II)?
I have a PC + REW + mic and know the basics of REW. I am new to impedance testing but it has value too, although I'm not totally understanding of it.
It's a commercial product ... kinda ...
While googling myself in the privacy of my own living room
I found
warren gregoire and associates - micro transmission line speaker system
While not exactly what I am playing with, if the claims are true, it's an interesting concept and mentions that it can be used in a line array. Anybody have any experience with these?
As usual, I have no commercial interest in this company and have no profit motive in providing the URL. Now, if I can make an inferior DIY version of their product, we can talk!
Meanwhile, I ran sweeps on the individual drivers of the Marimba and have at least three drivers that don't meet even my low standards. So further testing on hold until I swap these out.
While googling myself in the privacy of my own living room
I found
warren gregoire and associates - micro transmission line speaker system
While not exactly what I am playing with, if the claims are true, it's an interesting concept and mentions that it can be used in a line array. Anybody have any experience with these?
As usual, I have no commercial interest in this company and have no profit motive in providing the URL. Now, if I can make an inferior DIY version of their product, we can talk!
Meanwhile, I ran sweeps on the individual drivers of the Marimba and have at least three drivers that don't meet even my low standards. So further testing on hold until I swap these out.
Why built this? There are no specs given outside of Fs at 150 (yawn). The person behind the design has an oddly incorrect interpretation of acoustics. Dynamic capability would be limited. Band limited >150Hz power rating for a 4unit line is probably no more than 20w. He either refuses to publish some basic measurements or is not technically capable of it. Odd behaviour for someone trying to sell one little speaker en mass.While googling myself in the privacy of my own living room
I found
warren gregoire and associates - micro transmission line speaker system
While not exactly what I am playing with, if the claims are true, it's an interesting concept and mentions that it can be used in a line array. Anybody have any experience with these?
As usual, I have no commercial interest in this company and have no profit motive in providing the URL. Now, if I can make an inferior DIY version of their product, we can talk!
Btw using a tl for a midrange tunnel is not new. They do have their quirks like dampening the resonances and clearance from the port to the nearest boundry. Ample clearance is required. Have heard a few and placement seems to favor nearly the same as an ob speaker.
The secret of my success
I looked at Gregoire's web site some more and I think he is in New Zealand. Since the manufacturer is unnamed, who knows?
"Transmission Line" is one of those terms that (in acoustics) should be clear but isn't. Originally it meant the goal of absorbing the entire back wave (usually what is tried when a mid range is involved.) If it's a "pipe" (quarter wave resonator) or a variant, as many authors would call it, it then has the goal of making some use of the back wave usually for bass (duh!)
Meanwhile, the sloppy mods on the Marimba continue. I'm painting it is shades of white and blue to match my tiles (and the paint stains on the floor blend in easier).
To no one's surprise, at least three of the nine initial drivers were "bad". Other than the one I fried by too much signal, after removal the reason was clear (or more precisely, yellow and opaque): some of the Gorilla Glue had gotten on the back side of the cones. It is actually possible to remove most of it and (maybe) the driver is re-usable. Not the one that I ripped or poked holes in the cone though
Here is a photo of a younger Soldermizer showing his custom technique of readying himself for designing or constructing:
I looked at Gregoire's web site some more and I think he is in New Zealand. Since the manufacturer is unnamed, who knows?
"Transmission Line" is one of those terms that (in acoustics) should be clear but isn't. Originally it meant the goal of absorbing the entire back wave (usually what is tried when a mid range is involved.) If it's a "pipe" (quarter wave resonator) or a variant, as many authors would call it, it then has the goal of making some use of the back wave usually for bass (duh!)
Meanwhile, the sloppy mods on the Marimba continue. I'm painting it is shades of white and blue to match my tiles (and the paint stains on the floor blend in easier).
To no one's surprise, at least three of the nine initial drivers were "bad". Other than the one I fried by too much signal, after removal the reason was clear (or more precisely, yellow and opaque): some of the Gorilla Glue had gotten on the back side of the cones. It is actually possible to remove most of it and (maybe) the driver is re-usable. Not the one that I ripped or poked holes in the cone though
Here is a photo of a younger Soldermizer showing his custom technique of readying himself for designing or constructing:
Attachments
Yet another stupid word play!
I have been using one Bose 901 cabinet (actually the clone I bought last year) as a seat in front of my audio PC. It occurs to me that it is a "stool" in the sense of being seating; another meaning of the word "stool" is often used by Boseophobes to refer to the quality of said product. 😀
If my language skills equalled my speaker building prowess, I'd be illiterate 🙂
I have been using one Bose 901 cabinet (actually the clone I bought last year) as a seat in front of my audio PC. It occurs to me that it is a "stool" in the sense of being seating; another meaning of the word "stool" is often used by Boseophobes to refer to the quality of said product. 😀
If my language skills equalled my speaker building prowess, I'd be illiterate 🙂
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