Sim of 3-driver SSS
I am trying to get a better understanding of how the resistor and capacitor values in the psychoacoustic filter affects the polar response so that I can set the values with some semblance of analysis rather than guessing. Akabak cannot model the side wall reflections so this is really just to understand what the sound field looks like from the speaker in open space. I can turn reflections on but that is only back wall and floor - no sides.
The simulation is for a 3-driver (Vifa TC9FD) SSS with 45 deg side-firing drivers and bottom mounted reflex port. I wired the psychoacoustic filter as I have it built currently with 5 ohm and 4 uF capacitor. The sim assumes the signal is evenly divided by driving both the right and left channels in parallel, the matrix circuitry takes over from there to feed into the single center driver and bleeding some power off through the RC filter.
Here is the frequency response of the individual drivers and port (right, center, port):
Here is the frequency response at 0 deg on-axis (total - black, front -red, side - green):
Here is the frequency response at 45 deg off-axis (total - black, front - red, right side - green):
As you can see, the port output indicates there may be leakage at higher frequencies (which probably will not be as bad in reality as there is foam lining and stuffing inside the box to absorb much of that).
Here is the polar response (100 Hz, 1 kHz, 3kHz):
Here is the impedance of the system (for a 3 x 6.3 ohm driver system it appears to be a nominally 10 ohm total impedance):
Here is the cone displacement:
What I am seeing is that the middle driver has about double the excursion of the sides and this probably indicates it would be a good thing to have another driver in the middle channel (for a 4 driver system as Nagaoka had it) to keep all driver cone displacements under control.
Here is the impulse response:
I think that the IR oscillations are due to the fact that I don't have the box properly damped in the simulation. Decreasing the Q really cleans up the oscillations.
So the point of this was to give me a tool to play with the values of the psyhoacoustic filter. If I set the capacitor value to 10 uF, the polar plot looks like this:
Here is the response with the psychoacoustic filter bypassed (all current going through center channel):
All the lobing present in the polars indicates that this speaker is not for near field use - you will hear what is essentially large scale comb filtering effects as you move your head about or walk about near the speaker. However, in a suitable room with sidewalls that reflect those lobes and re-form them to a central image farther away, I think the sound will be more uniform and the apparent sweet spot will be larger.
The next thing to explore is the angle of the side firing drivers (90 deg, maybe even backwards?).
I am trying to get a better understanding of how the resistor and capacitor values in the psychoacoustic filter affects the polar response so that I can set the values with some semblance of analysis rather than guessing. Akabak cannot model the side wall reflections so this is really just to understand what the sound field looks like from the speaker in open space. I can turn reflections on but that is only back wall and floor - no sides.
The simulation is for a 3-driver (Vifa TC9FD) SSS with 45 deg side-firing drivers and bottom mounted reflex port. I wired the psychoacoustic filter as I have it built currently with 5 ohm and 4 uF capacitor. The sim assumes the signal is evenly divided by driving both the right and left channels in parallel, the matrix circuitry takes over from there to feed into the single center driver and bleeding some power off through the RC filter.
Here is the frequency response of the individual drivers and port (right, center, port):
Here is the frequency response at 0 deg on-axis (total - black, front -red, side - green):
Here is the frequency response at 45 deg off-axis (total - black, front - red, right side - green):
As you can see, the port output indicates there may be leakage at higher frequencies (which probably will not be as bad in reality as there is foam lining and stuffing inside the box to absorb much of that).
Here is the polar response (100 Hz, 1 kHz, 3kHz):
Here is the impedance of the system (for a 3 x 6.3 ohm driver system it appears to be a nominally 10 ohm total impedance):
Here is the cone displacement:
What I am seeing is that the middle driver has about double the excursion of the sides and this probably indicates it would be a good thing to have another driver in the middle channel (for a 4 driver system as Nagaoka had it) to keep all driver cone displacements under control.
Here is the impulse response:
I think that the IR oscillations are due to the fact that I don't have the box properly damped in the simulation. Decreasing the Q really cleans up the oscillations.
So the point of this was to give me a tool to play with the values of the psyhoacoustic filter. If I set the capacitor value to 10 uF, the polar plot looks like this:
Here is the response with the psychoacoustic filter bypassed (all current going through center channel):
All the lobing present in the polars indicates that this speaker is not for near field use - you will hear what is essentially large scale comb filtering effects as you move your head about or walk about near the speaker. However, in a suitable room with sidewalls that reflect those lobes and re-form them to a central image farther away, I think the sound will be more uniform and the apparent sweet spot will be larger.
The next thing to explore is the angle of the side firing drivers (90 deg, maybe even backwards?).
Attachments
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4-driver SSS sim
In seeing that the excursion of the middle driver was so much higher than the left and right, I added a 4th driver in the sim so that the two center channels are now in parallel. This helps a lot as the cone excursion is now identical for all 4 drivers. I have turned on wall and floor reflections with the speaker mounted flush to the back wall and driver centerline at 48 in above the floor.
Here is the new cone displacement:
This is the frequency response at 0 deg (on axis):
This is the frequency response at 45 deg off axis:
Here is the polar response:
In seeing that the excursion of the middle driver was so much higher than the left and right, I added a 4th driver in the sim so that the two center channels are now in parallel. This helps a lot as the cone excursion is now identical for all 4 drivers. I have turned on wall and floor reflections with the speaker mounted flush to the back wall and driver centerline at 48 in above the floor.
Here is the new cone displacement:
This is the frequency response at 0 deg (on axis):
This is the frequency response at 45 deg off axis:
Here is the polar response:
Attachments
Measurement of SSS
Mic at 1 meter away, speaker 2 in from back wall at 50 in above ground sitting on top of amplifier deck (which may be causing bounce dip).
0 deg, 30 deg, 45 deg. The response in the mid to high freq is pretty flat and bass reaches 70 Hz as predicted. The +10 dB peak at 150 hz may be a problem though - not sure what it is caused by. Also, no BSC needed as predicted.
A decent sounding speaker actually.
Mic at 1 meter away, speaker 2 in from back wall at 50 in above ground sitting on top of amplifier deck (which may be causing bounce dip).
0 deg, 30 deg, 45 deg. The response in the mid to high freq is pretty flat and bass reaches 70 Hz as predicted. The +10 dB peak at 150 hz may be a problem though - not sure what it is caused by. Also, no BSC needed as predicted.
A decent sounding speaker actually.
Attachments
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nice work.
makes sence that you need 2 drivers (center) ............
Otherwise if 1 driver is firing at you, it would be doing the same excursion as 2 drivers (signals left and right going through it).
In post 2, can we assume the left/right are the center 2 and the L+r and L-R are firing off center ?
Wouldn't that be a completely different sounding animal than summing the signal to mono going through the center 2 drivers ?
Norman
makes sence that you need 2 drivers (center) ............
Otherwise if 1 driver is firing at you, it would be doing the same excursion as 2 drivers (signals left and right going through it).
In post 2, can we assume the left/right are the center 2 and the L+r and L-R are firing off center ?
Wouldn't that be a completely different sounding animal than summing the signal to mono going through the center 2 drivers ?
Norman
Yes, I think the sound characteristics of the Nagaoka MX-1 is going to be very different than the matrix suggested by Elias (which is how I am doing it). Elias has some sims of the matrix effect so I am more inclined to go with what has some plots of how the beam steering of the sound can be effected with the current setup. They are different though as you suggest. I am surprised by how uniform the polar response is at the three measured positions. The peaks due to the HF leakage out of the port did not happen as I predicted given enough foam lining the interior walls and a small amount of polyfill directly behind drivers.
And yes, L+R and L-R are the side firing drivers.
And yes, L+R and L-R are the side firing drivers.
Danerius,
I have thought about the same thing of using a 6.5 in woofer for the middle channel. This way the whole excursion thing and bass can be handled better. The psychoacoustic filter would just be natural HF falloff of woofer which hits 3.5khz naturally. You would need to isolate chamber for left and right from middle. Maybe make left and right sealed.
Tyimo,
Extra woofer could be done separately as a FAST or like idea above with woofer on central channel.
Esgigt,
Yes, Blanda bowls of any small sealed speaker can be used like this to try out first. I did similar thing with my Karlsonators and a Nautaloss. Home theater satellite cube speakers also are a good candidate.
I have thought about the same thing of using a 6.5 in woofer for the middle channel. This way the whole excursion thing and bass can be handled better. The psychoacoustic filter would just be natural HF falloff of woofer which hits 3.5khz naturally. You would need to isolate chamber for left and right from middle. Maybe make left and right sealed.
Tyimo,
Extra woofer could be done separately as a FAST or like idea above with woofer on central channel.
Esgigt,
Yes, Blanda bowls of any small sealed speaker can be used like this to try out first. I did similar thing with my Karlsonators and a Nautaloss. Home theater satellite cube speakers also are a good candidate.
As a FAST, I would be using separate amplifier and active XO so you could do either stereo woofer or just a single sub with either dual voice coils, or mix L+R into single sub.
If you want to tie woofer to the central channel in parallel it will need a passive XO (probably nothing more than a fat coil like 20 mH and a 2nd order high pass for the two full range drivers).
If you want to tie woofer to the central channel in parallel it will need a passive XO (probably nothing more than a fat coil like 20 mH and a 2nd order high pass for the two full range drivers).
I keep being intrigued by the concept discussed here, but know I don't have a proper space to set this up on anything but a temporary basis, at least for now.
Using fullrange drivers is an obvious, easy and simple solution. I was thinking the small ApexJr Vifa 4" coaxial might be fun too. The main difference would be in the much wider beamwidth in the treble region, since a 0.75" tweeter is on there. Would this be an issue with regard to the proper working of a 45° matrix speaker? Maybe Elias' initial 90° scheme would be a better choice for these?
Scroll down roughly halfway:
Speaker Stuff
Using fullrange drivers is an obvious, easy and simple solution. I was thinking the small ApexJr Vifa 4" coaxial might be fun too. The main difference would be in the much wider beamwidth in the treble region, since a 0.75" tweeter is on there. Would this be an issue with regard to the proper working of a 45° matrix speaker? Maybe Elias' initial 90° scheme would be a better choice for these?
Scroll down roughly halfway:
Speaker Stuff
IG81,
If you have a couple of small sealed boxes you can try this out - independently variable angles on the side firing units. I think the Apex Jr Vifa coaxials would be a great choice - I don't think the wider beam width of the tweeter is an issue here. Give it a test and if you like it, make a single box like I did. It is an easy test to do.
If you have a couple of small sealed boxes you can try this out - independently variable angles on the side firing units. I think the Apex Jr Vifa coaxials would be a great choice - I don't think the wider beam width of the tweeter is an issue here. Give it a test and if you like it, make a single box like I did. It is an easy test to do.
Sounds cool
And also. Arent roofs generally a lot less unobstructed than walls. Ive heard these speakers in various incarnations and theyve always sounded great. Maybe I should get one and rewire it to Matrix Stereo sonab OA-14 floorstanding, upward-firing speakers - Audio Asylum Trader
Regards /Bo
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Those Sonabs look really cool - you may be on to something with sort of aiming them sideways and up at the ceiling. The Sonab's tweeters are side and front firing only. I suppose some mid bass is up firing too. I am intrigued by the whole concept because I think I could make one with the drivers I have on hand. Although qnty 4 Vifa TC9's would be overkill. Maybe get some $3 2-inch tweeters and arrange it in the similar array as the Sonab and use my $5 polycone 6.5-in woofer aimed up at an angle. I would leave all the wires coming out the back like a telephone switchboard and use banana plug cables as jumpers to dial in the matrix I like to experiment. Would need a big coil for the woofer low pass though. In a pinch maybe use an old power transformer I have lying around? With foam core I have the ability to sculpt the base in a nice rounded fluid like shape. Maybe semi airfoil like. The top would be a truncated pyramid with the woofer on the top roof and the 4 tweeters angled out and up at say 45 deg. It would look pretty cool. Internally, the tweeters will be sealed back chambers and the main chamber would be divided to form a tapered mass loaded TL with a vent at the bottom and the 6.5in driver at about midpoint. In a 30in tall cabinet (height of FC) this should reach circa 35 Hz easily. Can be a lot of fun.
Hi guys
I have four 16-ohm 2" x 3.5" drivers I can play with (see pic below). The problem is that they will not go lower than about 200Hz, so they will need some bass support. I do not have four bass drivers at hand right now- all I have is a pair of 4" full-range (car audio) drivers that I can use. Will it work if I put the 2" x 3.5" drivers in the four-driver array, and then connect the two woofers in standard stereo on a flat baffle below them? These are the only units I have to hand right now to play with.
Thanks,
Deon
Here is a pic of a driver similar to the ones I have:
I have four 16-ohm 2" x 3.5" drivers I can play with (see pic below). The problem is that they will not go lower than about 200Hz, so they will need some bass support. I do not have four bass drivers at hand right now- all I have is a pair of 4" full-range (car audio) drivers that I can use. Will it work if I put the 2" x 3.5" drivers in the four-driver array, and then connect the two woofers in standard stereo on a flat baffle below them? These are the only units I have to hand right now to play with.
Thanks,
Deon
Here is a pic of a driver similar to the ones I have:
An externally hosted image should be here but it was not working when we last tested it.
Hi guys
Considering the rectangular shape of these drivers, that allows three possible layouts. The first option is the standard layout. Option 2 one places the L and R drivers on the front next to each other. Option 3 is the same as Option 1, but the drivers are places sideways. The only problem with this option is that the off-axis dispersion might become problematic. Here are drawings on the three possible layouts. Which would be best?
Option 1 - Standard layout:
Option 2: L & R side-by-side:
Option 3: like Option 1, but drivers are sideways:
Thanks,
Deon
Considering the rectangular shape of these drivers, that allows three possible layouts. The first option is the standard layout. Option 2 one places the L and R drivers on the front next to each other. Option 3 is the same as Option 1, but the drivers are places sideways. The only problem with this option is that the off-axis dispersion might become problematic. Here are drawings on the three possible layouts. Which would be best?
Option 1 - Standard layout:
An externally hosted image should be here but it was not working when we last tested it.
Option 2: L & R side-by-side:
An externally hosted image should be here but it was not working when we last tested it.
Option 3: like Option 1, but drivers are sideways:
An externally hosted image should be here but it was not working when we last tested it.
Thanks,
Deon