audioresearch
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- Jul 15, 2023
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I still have speaker design software Leap 4.5 and measurement hardware/software MLSSA both of which I haven't used in about 20 years but in the future, I plan to re-design my loudspeaker system and am curious to know the best, most complete design software/hardware to use to get the best results in designing a speaker, especially the woofer portion.
If I remember correctly, I could feed Fs, Qms, Qes, Xmax. cone area which I think is Sd, and max allowed continuous input power to driver, the volume of the speaker cabinet, and the length/diameter of the port tube (for a bass reflex design) and the location(s) of the drivers and ports on the cabinet and the continuous power level I wished to use to drive the speaker to Leap 4.5 and Leap 4.5 would then give me output graphs including total power radiated. When I last did this, it may have been before spinorama and so I used total radiated power. I fully believe in the work of Floyd Toole and spinorama and so I would prefer to be able to measure it and incorporate its results into whatever design/measurement software/hardware that is recommended for me to use.
I currently have four cabinets. Each is about 42" x 21" x 11" and each contains an Eminence 18" woofer, 4 midranges arrayed vertically, and a Vifa tweeter and two ports(bass reflex). I designed this to sell as a product and sold a few dozen. I picked an 18" woofer because I thought it would impress customers (and it most certainly did) and I picked one with a strong magnet. I then used Leap 4.5 to select the best length and width of the port tubes for the bass reflex design. I equalized the entire system similar to what is done in the Bose 901. In fact, I came up with a way to copy the Bose 901 frequency response into my system by designing my equalizer so that my speaker output with my equalizer being used had very close to the same frequency response as the 901 had with its equalizer being used. I simply figured that Bose would have gotten the frequency response right and so I copied his. My procedure worked because I demoed my system to customers up against a Bose 901 and none of my customers could tell my speaker's sound apart from that of the 901 except when I cranked up the power, my system would play so loud with unobjectionable distortion that one could not even tell if the 901 was even playing or not.
My favorite demo to my customers was to play a video tape I made at an air show of a Harrier Jump Jet hovering about 100' from me with an spl meter I put into the picture showing a 125db spl and I then played that same video and the audio through my system I was demonstrating to potential customers at 135db which sounds to the ear twice as loud as the real jet. We all wore ear protectors that were used at rifle ranges and even at those sound levels, nobody could hear any distortion.
My system seems to fall off in response at about 35 to 40 Hz.
I hired an acoustics professor to design a subwoofer to go lower. He did that using Akabak in the early 2000s. The system he built for me goes noticeably lower in the bass than my system. I believe his system starting audibly falling off at about 10Hz lower than my system and I could easily hear that difference. His cabinet was maybe about 20% larger in volume than mine and two 12" woofer were used and it was also a ported design.
So, now for my personal use, I'm thinking of redesigning my speakers but this time picking the woofer that will give me the lowest audible bass within acceptable distortion limits rather than just using the "flashiest" woofer I could find for the purpose of selling speakers. So, I'm open to another 18" woofer, or one or two 15" woofers or 12" woofer, whatever works best and I'm open to the bass reflex design or a sealed design or a bandpass design for the bass or whatever works best.
I'm thinking of using 2 pairs of the original Bose 901 systems I already own. Yes, I most certainly have to clean some corrosion off internal 901 wiring and replace one or two drivers with some from a parts 901 for these to once again work fine, but I know just how to do that and where the weak points are that need to be addressed.
It is my tentative plan to put one 901 behind each of my speaker cabinets and let the 901s bounce their sound of the back wall as they are intended to do. For the forward facing midranges, I will continue to use the 4 midranges in each of my speaker cabinets (the forward facing drivers in the 901s will be blocked because the 901s will be only an inch or two behind my speaker cabinets).
Every so often, I would blow a tweeter in my speakers and so this time around, I plan to eliminate the tweeters and adjust the equalizer so that the 901s plus all the midranges in my speakers (total of 16 midranges in my speakers) will not only output midrange sound, but also the higher frequency sound just like the 901 does.
It is my hope that this way I get the huge spacious 901 sound, I eliminate tweeter blowouts, and that I can crank up the volume if I so desire (and sometimes I do) to a level that will make each of my eardrums meet somewhere inside my head and I will also offload much of the low bass from the 901s (their Achilles heel) onto my speakers that are very efficient mostly due to their large cabinet size and their large woofers and thus eliminate the low bass 901 distortion.
The amplifier I use is a Peavey PV2000 which should output somewhere between 1400 and 2000 watts into this combined system and with the efficiency of my large speakers, this will put out in my listening room spl levels similar to what a huge Hollywood movie theater such as the Pacific Cinerama Dome used to do.
Some may ask why I like Bose so let me tell you. In the mid 60s, I often went over to MIT where nobody would complain if I just walked up to a computer and put programs into it and ran them. In those days, virtually nobody else had computers. On one of those computers, I heard students/staff playing digital music in 1965 and also playing a video game called Spacewars. I later found out about Professor Bose and heard that he used that very computer, if I remember right, to process the room response using an impulse response measurement in the room and then ran a convolution on the computer to remove what the room did to the sound of his first speaker, the Bose 2201.
Bose was just so far ahead of anyone else, it was simply mindboggling. In my opinion, what he did to other audio designers was like what Klaatu did to Professor Barnhardt in "The Day the Earth Stood Still". I heard Bose's first speaker, the 2201, in Bose's MIT lab in 1966 playing music directly from a master tape he made himself of the Boston Pops playing at Tanglewood. The sound was beyond good and made the AR3-A speakers I owned sound very un-lifelike.
Later, he came out with the 901 not because the 2201 was bad, but because it was so large & expensive and because its required corner placement was such a drawback, that not many of them sold.
The 901 totally eliminated crossovers which are the source of colorations and which don't deal well when drivers heat up and the voice coil resistance increases (correct me if you think that these days this may no longer be a problem). I was told that the driver resonance was purposely made high so that more of the low bass curve would be below it for the reason that the response curve below resonance was very smooth and could thus be equalized to be super flat. Bose also designed the speaker to have flat power radiation vs frequency which per his research was an improvement over only flat on-axis response (plus, the anechoic chambers that other manufacturers used are not really anechoic in the low bass region and so who can trust their on-axis response curves in the low bass?). The 901 clearly had a much larger more true-to-life sound than other speakers on most music material because it bounced most of its sound off the back and side walls of the room.
Plus, I simply trusted Bose. I audited his MIT acoustics course and he really knew his stuff inside out and he carried on the work of some of the best previous audio engineers such as Harry Olson and Leo Beranek, legends in the field. I also saw some of the results of his psycho-acoustic testing to scientifically determine if phase differences were audible and to determine exactly what levels of what kind of distortion were audible and over which frequency ranges-some of these results were very surprising.
The funny thing is that some people think that Bose would not give out specs because he was trying to cheat customers but in fact, he did not give out specs for the opposite reason, namely, that the specs being used by speaker company marketing departments were bs and the use of those specs in fact was what was cheating customers.
Another result I learned from Bose was that for typical music, listeners can't tell if frequencies over somewhere between 12KHz and 14Khz are totally removed or not due to masking. The original experimenter never botherd to see just where in the 12Khz to 14Khz range was the exact demarcation and that is why this is stated as a range..
I really like the work that Amir and Erin's Audio Corner have done testing speakers including the 901 and applying Klippel/Spinorama/etc and would like to try to use these techniques at some point in time when I re-design my own system which will probably begin in about one to two years from now. It certainly sounds to me that Spinorama is better than only adjusting for flat total power radiation vs frequency.
Please give me advice on what software/hardware to use for design & measurement and what workflow to use and please feel free to give comments & opinions-I'm sure I'll get some.
If I remember correctly, I could feed Fs, Qms, Qes, Xmax. cone area which I think is Sd, and max allowed continuous input power to driver, the volume of the speaker cabinet, and the length/diameter of the port tube (for a bass reflex design) and the location(s) of the drivers and ports on the cabinet and the continuous power level I wished to use to drive the speaker to Leap 4.5 and Leap 4.5 would then give me output graphs including total power radiated. When I last did this, it may have been before spinorama and so I used total radiated power. I fully believe in the work of Floyd Toole and spinorama and so I would prefer to be able to measure it and incorporate its results into whatever design/measurement software/hardware that is recommended for me to use.
I currently have four cabinets. Each is about 42" x 21" x 11" and each contains an Eminence 18" woofer, 4 midranges arrayed vertically, and a Vifa tweeter and two ports(bass reflex). I designed this to sell as a product and sold a few dozen. I picked an 18" woofer because I thought it would impress customers (and it most certainly did) and I picked one with a strong magnet. I then used Leap 4.5 to select the best length and width of the port tubes for the bass reflex design. I equalized the entire system similar to what is done in the Bose 901. In fact, I came up with a way to copy the Bose 901 frequency response into my system by designing my equalizer so that my speaker output with my equalizer being used had very close to the same frequency response as the 901 had with its equalizer being used. I simply figured that Bose would have gotten the frequency response right and so I copied his. My procedure worked because I demoed my system to customers up against a Bose 901 and none of my customers could tell my speaker's sound apart from that of the 901 except when I cranked up the power, my system would play so loud with unobjectionable distortion that one could not even tell if the 901 was even playing or not.
My favorite demo to my customers was to play a video tape I made at an air show of a Harrier Jump Jet hovering about 100' from me with an spl meter I put into the picture showing a 125db spl and I then played that same video and the audio through my system I was demonstrating to potential customers at 135db which sounds to the ear twice as loud as the real jet. We all wore ear protectors that were used at rifle ranges and even at those sound levels, nobody could hear any distortion.
My system seems to fall off in response at about 35 to 40 Hz.
I hired an acoustics professor to design a subwoofer to go lower. He did that using Akabak in the early 2000s. The system he built for me goes noticeably lower in the bass than my system. I believe his system starting audibly falling off at about 10Hz lower than my system and I could easily hear that difference. His cabinet was maybe about 20% larger in volume than mine and two 12" woofer were used and it was also a ported design.
So, now for my personal use, I'm thinking of redesigning my speakers but this time picking the woofer that will give me the lowest audible bass within acceptable distortion limits rather than just using the "flashiest" woofer I could find for the purpose of selling speakers. So, I'm open to another 18" woofer, or one or two 15" woofers or 12" woofer, whatever works best and I'm open to the bass reflex design or a sealed design or a bandpass design for the bass or whatever works best.
I'm thinking of using 2 pairs of the original Bose 901 systems I already own. Yes, I most certainly have to clean some corrosion off internal 901 wiring and replace one or two drivers with some from a parts 901 for these to once again work fine, but I know just how to do that and where the weak points are that need to be addressed.
It is my tentative plan to put one 901 behind each of my speaker cabinets and let the 901s bounce their sound of the back wall as they are intended to do. For the forward facing midranges, I will continue to use the 4 midranges in each of my speaker cabinets (the forward facing drivers in the 901s will be blocked because the 901s will be only an inch or two behind my speaker cabinets).
Every so often, I would blow a tweeter in my speakers and so this time around, I plan to eliminate the tweeters and adjust the equalizer so that the 901s plus all the midranges in my speakers (total of 16 midranges in my speakers) will not only output midrange sound, but also the higher frequency sound just like the 901 does.
It is my hope that this way I get the huge spacious 901 sound, I eliminate tweeter blowouts, and that I can crank up the volume if I so desire (and sometimes I do) to a level that will make each of my eardrums meet somewhere inside my head and I will also offload much of the low bass from the 901s (their Achilles heel) onto my speakers that are very efficient mostly due to their large cabinet size and their large woofers and thus eliminate the low bass 901 distortion.
The amplifier I use is a Peavey PV2000 which should output somewhere between 1400 and 2000 watts into this combined system and with the efficiency of my large speakers, this will put out in my listening room spl levels similar to what a huge Hollywood movie theater such as the Pacific Cinerama Dome used to do.
Some may ask why I like Bose so let me tell you. In the mid 60s, I often went over to MIT where nobody would complain if I just walked up to a computer and put programs into it and ran them. In those days, virtually nobody else had computers. On one of those computers, I heard students/staff playing digital music in 1965 and also playing a video game called Spacewars. I later found out about Professor Bose and heard that he used that very computer, if I remember right, to process the room response using an impulse response measurement in the room and then ran a convolution on the computer to remove what the room did to the sound of his first speaker, the Bose 2201.
Bose was just so far ahead of anyone else, it was simply mindboggling. In my opinion, what he did to other audio designers was like what Klaatu did to Professor Barnhardt in "The Day the Earth Stood Still". I heard Bose's first speaker, the 2201, in Bose's MIT lab in 1966 playing music directly from a master tape he made himself of the Boston Pops playing at Tanglewood. The sound was beyond good and made the AR3-A speakers I owned sound very un-lifelike.
Later, he came out with the 901 not because the 2201 was bad, but because it was so large & expensive and because its required corner placement was such a drawback, that not many of them sold.
The 901 totally eliminated crossovers which are the source of colorations and which don't deal well when drivers heat up and the voice coil resistance increases (correct me if you think that these days this may no longer be a problem). I was told that the driver resonance was purposely made high so that more of the low bass curve would be below it for the reason that the response curve below resonance was very smooth and could thus be equalized to be super flat. Bose also designed the speaker to have flat power radiation vs frequency which per his research was an improvement over only flat on-axis response (plus, the anechoic chambers that other manufacturers used are not really anechoic in the low bass region and so who can trust their on-axis response curves in the low bass?). The 901 clearly had a much larger more true-to-life sound than other speakers on most music material because it bounced most of its sound off the back and side walls of the room.
Plus, I simply trusted Bose. I audited his MIT acoustics course and he really knew his stuff inside out and he carried on the work of some of the best previous audio engineers such as Harry Olson and Leo Beranek, legends in the field. I also saw some of the results of his psycho-acoustic testing to scientifically determine if phase differences were audible and to determine exactly what levels of what kind of distortion were audible and over which frequency ranges-some of these results were very surprising.
The funny thing is that some people think that Bose would not give out specs because he was trying to cheat customers but in fact, he did not give out specs for the opposite reason, namely, that the specs being used by speaker company marketing departments were bs and the use of those specs in fact was what was cheating customers.
Another result I learned from Bose was that for typical music, listeners can't tell if frequencies over somewhere between 12KHz and 14Khz are totally removed or not due to masking. The original experimenter never botherd to see just where in the 12Khz to 14Khz range was the exact demarcation and that is why this is stated as a range..
I really like the work that Amir and Erin's Audio Corner have done testing speakers including the 901 and applying Klippel/Spinorama/etc and would like to try to use these techniques at some point in time when I re-design my own system which will probably begin in about one to two years from now. It certainly sounds to me that Spinorama is better than only adjusting for flat total power radiation vs frequency.
Please give me advice on what software/hardware to use for design & measurement and what workflow to use and please feel free to give comments & opinions-I'm sure I'll get some.
