So here it is.
This thread will deal with the design of a full range speaker system that will, as nearly as possible, reproduce a square wave.
<font color="#ff0000">First, I would like to say that this thread will be totally intolerant of off -the-subject issues. I will report to a moderator anyone who goes of into never, never land. I started this thread and I'll be damned if I'll let anyone screw it up.</font>
The criteria, as I see it, are as follows:
1. Must be done with off the shelf dynamic drivers. NO horns may be involved.
2. Must be done with analog only techniques. NO digital filters.
3. Must be practical for DIY.
4. May be bi or tri-amped.
5. Should reproduce a 30Hz square wave.
6. Assumed is a 20Khz 2nd or 4th order roll-off.
7. First arrival times are the issue. No consideration should be given to room interactions. That is to say, we are looking at an anechoic response of a single system.
8. Recognized attributes of a speaker system must be maintained. That is to say, low distortion, decent power handling, etc.
I make the following suggestions as per my own ideas and some previous input from the other square wave thread. Remember, this is only a starting point.
1. The system is a 3 way.
2. The mid range speakers should be 6 or 8 Tangband W4-654S in a vertical curved array with the focal point at the listening distance.<a href="http://www.partsexpress.com/pe/showdetl.cfm?&User_ID=8184019&St=9404&St2=-44059799&St3=61944947&DS_ID=3&Product_ID=117926&DID=7"> Link to speaker specs. </a> I challenge anyone to find a mid-range driver more suitable than this. I believe that 2 midrange drivers used in a MTM configuration might be preferable but I don't think that drivers with sufficient power handling AND the requisite high frequency response are available. <u>Suggestions welcome.</u>
3. The woofer should be sealed with a Qts of .7 and have an F3 of about 30Hz.
4. The selected tweeter should have the lowest resonant frequency possible and be a ferrofluid 1" dome. <u>Suggestions needed.</u>
5. This first part of the challenge should be the mid/tweet crossover and the success can be shown with a 500Hz square wave. I favor the subtractive or difference type crossover.
6. It is preferable that the system is physically time aligned to allow the potential use of passive crossovers rather than use active all pass networks.
Time for some input. And, again, if you can't stay on topic, please don't post.
This thread will deal with the design of a full range speaker system that will, as nearly as possible, reproduce a square wave.
<font color="#ff0000">First, I would like to say that this thread will be totally intolerant of off -the-subject issues. I will report to a moderator anyone who goes of into never, never land. I started this thread and I'll be damned if I'll let anyone screw it up.</font>
The criteria, as I see it, are as follows:
1. Must be done with off the shelf dynamic drivers. NO horns may be involved.
2. Must be done with analog only techniques. NO digital filters.
3. Must be practical for DIY.
4. May be bi or tri-amped.
5. Should reproduce a 30Hz square wave.
6. Assumed is a 20Khz 2nd or 4th order roll-off.
7. First arrival times are the issue. No consideration should be given to room interactions. That is to say, we are looking at an anechoic response of a single system.
8. Recognized attributes of a speaker system must be maintained. That is to say, low distortion, decent power handling, etc.
I make the following suggestions as per my own ideas and some previous input from the other square wave thread. Remember, this is only a starting point.
1. The system is a 3 way.
2. The mid range speakers should be 6 or 8 Tangband W4-654S in a vertical curved array with the focal point at the listening distance.<a href="http://www.partsexpress.com/pe/showdetl.cfm?&User_ID=8184019&St=9404&St2=-44059799&St3=61944947&DS_ID=3&Product_ID=117926&DID=7"> Link to speaker specs. </a> I challenge anyone to find a mid-range driver more suitable than this. I believe that 2 midrange drivers used in a MTM configuration might be preferable but I don't think that drivers with sufficient power handling AND the requisite high frequency response are available. <u>Suggestions welcome.</u>
3. The woofer should be sealed with a Qts of .7 and have an F3 of about 30Hz.
4. The selected tweeter should have the lowest resonant frequency possible and be a ferrofluid 1" dome. <u>Suggestions needed.</u>
5. This first part of the challenge should be the mid/tweet crossover and the success can be shown with a 500Hz square wave. I favor the subtractive or difference type crossover.
6. It is preferable that the system is physically time aligned to allow the potential use of passive crossovers rather than use active all pass networks.
Time for some input. And, again, if you can't stay on topic, please don't post.
tweeter the lowest Fs I kow is of the SS 9900 at 500Hz. but you want a tweeter with ferrofluid why?
otherwise I can recomend the Morel MDT33. it can handle power (and since 1990 the coils are replaceable from the face plate).
woofer
10" SS 8565 in 2 cu. ft.
Focal 10" (there are many).
regards
navin
otherwise I can recomend the Morel MDT33. it can handle power (and since 1990 the coils are replaceable from the face plate).
woofer
10" SS 8565 in 2 cu. ft.
Focal 10" (there are many).
regards
navin
Hi Bill,
Very nice. Here are some initial thoughts/suggestions/questions.
The Tangbangs look great. 8 drivers will allow series/parallel hookup for an 8Ohm nominal load. More drivers will also help to minimize IM with the wide bandwidth.
Maybe a Quasi-MTM configuration with 4 TB's up and 4 TB's down.
Crossover to the tweeter above 5kHz to maximize the mid-range bandwidth, isolate the fundamentals in the mid-range, and minimize time delays of the crossover (90 degrees at 6kHz is a smaller time delay then 90 degrees at 3kHz).
Maybe a ribbon tweeter for its resistive loading (just a thought)
Why the low resonance in the tweeter?
Still Think'in.
Rodd Yamas***a
Very nice. Here are some initial thoughts/suggestions/questions.
The Tangbangs look great. 8 drivers will allow series/parallel hookup for an 8Ohm nominal load. More drivers will also help to minimize IM with the wide bandwidth.
Maybe a Quasi-MTM configuration with 4 TB's up and 4 TB's down.
Crossover to the tweeter above 5kHz to maximize the mid-range bandwidth, isolate the fundamentals in the mid-range, and minimize time delays of the crossover (90 degrees at 6kHz is a smaller time delay then 90 degrees at 3kHz).
Maybe a ribbon tweeter for its resistive loading (just a thought)
Why the low resonance in the tweeter?
Still Think'in.
Rodd Yamas***a
Bill Fitzpatrick said:
Perhaps as per the previous thread this should say a 30Hz square wave passed thru a 30-20kHz bandpass filter.
This is pretty head-in-a-vise restrictive (and realistically totally impractical). A single mid/full-range in the middle would make it a lot more sense and make the goal of a square wave easier. Something like a Jordan JX92 would be a good choice.
Butterworth is maximally flat amplitude, wouldn't it be better to have a maximally flat time alignment? Bessel (Q=0.578) gives the flattest phase.
practical, but restrictive. They aren't often considered, but there are some pretty good cone tweeters (Jordan JX53). Ferrofluid means flatter impedance response at the resonance making a simplier XO possible.
That only works if it is active. Requires that the acoustic centres line up -- ideally vertically & horizontally
dave
navin said:
The lowest Fs in a T that i know about is the PEARL PR-2 tweeter with an Fs of 150 Hz -- unobtainum thou.
The low resonance and ferrofluid are both preferrable due to the (likely) 1st order XOs required to maintain time coherency (the active subtractive XO would give a 2nd order on one half -- 3rd order is also doable but the bump on the bottom of the derived half starts getting kinda big). phase_accurate's stacked concept or the subtractive XO with time delay would be required for steeper XO, but that eliminates any passive XO.
dave
Another criteria for the tweeter is that it should have a very small mounting profile, so that interdriver distance can be minimized and if a step gets involved for physical alignment we have maximum versatility (ie a pod like on the B&W nautilus).
Another thing that should be thrown into the pot, is that if the T is behind the mid acoustically (ie a co-axially mounted tweeter), this can, in some cases, be time compensated by a high order bessel -- passive or active.
dave
Another thing that should be thrown into the pot, is that if the T is behind the mid acoustically (ie a co-axially mounted tweeter), this can, in some cases, be time compensated by a high order bessel -- passive or active.
dave
it all depends on what SPL the 30Hz square wave will be at.
one way to get a tweeter with a small front is to take an existinng tweeter with NDfeB magent and remove the face plate or take a car tweeter (Vifa D26NC can be used).
I have see a ss 9900 modfied with to fit too but that is a lot of work.
WMTMW with a D26NC and 2 Tangaband Mids and 2 6/8/10" woofers should do.
one way to get a tweeter with a small front is to take an existinng tweeter with NDfeB magent and remove the face plate or take a car tweeter (Vifa D26NC can be used).
I have see a ss 9900 modfied with to fit too but that is a lot of work.
WMTMW with a D26NC and 2 Tangaband Mids and 2 6/8/10" woofers should do.
Hi Bill
Maybe you should also specify how much "tilt" you would allow on the top and bottom of the 30 Hz square-wave sice this is definitely depandant on the lower cutoff frequency and vice-versa.
Even for a very relaxed spec a lower cutoff frequency of less than 20 Hz would be necessary.
I would by no means want to say that such a low cutoff frequency would be a bad thing to have, far from that !!!
But it wouldn't be easy to achieve !
Another thing that has to be specified is how much tolerance regarding the amplitude response you would allow.
I will post some more info that could be useful for the "wideband-midrange people" within the active subtractive thread.
Regards
Charles
Maybe you should also specify how much "tilt" you would allow on the top and bottom of the 30 Hz square-wave sice this is definitely depandant on the lower cutoff frequency and vice-versa.
Even for a very relaxed spec a lower cutoff frequency of less than 20 Hz would be necessary.
I would by no means want to say that such a low cutoff frequency would be a bad thing to have, far from that !!!
But it wouldn't be easy to achieve !
Another thing that has to be specified is how much tolerance regarding the amplitude response you would allow.
I will post some more info that could be useful for the "wideband-midrange people" within the active subtractive thread.
Regards
Charles
If someone has a better idea than a scope and a mic, I'm ready to listen.
As I see it this will be a out of doors test either, maybe both, buried face up in the ground and/or a high platform. And, obviously, the mic must be at the focal point not some arbitrary 1 meter. Where did that come from anyway?
-3db at 20Hz should be no problem. I'm thinking +/-3db on the amplitude response.
"Head in the vise restrictive". A good point to bring up with a vertical array. Horizontally there is no problem of course. Vertically, well . . . we all do our critical listening sitting down and the focal point can be selected by the individual builder to suit his listening height and distance. With the proper choice or mid/tweet crossover frequency I don't see any more of a problem than with a MTM. And, in terms of room power response it will be fine also. So if you're standing in the kitchen fixin' one of those delicious burnt weenie sandwiches, you may not be able to experience square wave nirvana but everything will still be excellent.
As I see it this will be a out of doors test either, maybe both, buried face up in the ground and/or a high platform. And, obviously, the mic must be at the focal point not some arbitrary 1 meter. Where did that come from anyway?
-3db at 20Hz should be no problem. I'm thinking +/-3db on the amplitude response.
"Head in the vise restrictive". A good point to bring up with a vertical array. Horizontally there is no problem of course. Vertically, well . . . we all do our critical listening sitting down and the focal point can be selected by the individual builder to suit his listening height and distance. With the proper choice or mid/tweet crossover frequency I don't see any more of a problem than with a MTM. And, in terms of room power response it will be fine also. So if you're standing in the kitchen fixin' one of those delicious burnt weenie sandwiches, you may not be able to experience square wave nirvana but everything will still be excellent.
well I meant that the output from a mic when fed a perfect audio square wave would be pretty far from a square wave, wouldn't it? Wouldnt it tend to round off your verticals ??
And I didnt htink you could put a scope on the output snce it seems like you have to use multiple drivers to produce the wave, and each driver is behind crossover components?
If you feed the speaker a perfect square wave, and scope it, and the speaker is ading distortion, would the scope still see a perfect square wave or would the distortion be evident?
And I didnt htink you could put a scope on the output snce it seems like you have to use multiple drivers to produce the wave, and each driver is behind crossover components?
If you feed the speaker a perfect square wave, and scope it, and the speaker is ading distortion, would the scope still see a perfect square wave or would the distortion be evident?
The square wave can't be perfectly square for two main reasons; the chosen tweeter is going to have a rolloff somewhere between 20K-30K and the woofer is going to have a low frequency limit. The mic will have limits as well. These can be modeled to obtain a picture of the target. This target is the bandwidth limited square wave previously mentioned.
Distortion products will not be significant for this experiment.
A circular array would be OK if you think in terms of a one dimensional sweet spot but it doesn't have any advantages so I would say it's not worth considering.
jackinnj: That would be one of those black box tricks where you get a flat frequency response output under sine wave conditions but it sound like ****. Fortunately that's not what we would be doing. Anyway, the resulting system has to pass other standard tests as well; impulse, step, waterfall, group delay, etc. Oh, it's got to sound good too!
Right now, my workbench is in disarray due to some remodeling so I haven't begun to breadboard anything. But, there are some interesting possibilites floating around in my mind on the active filter end of things.
It would be great if someone could suggest a tweeter with low resonace and ferrofluid at a reasonable price.
Distortion products will not be significant for this experiment.
A circular array would be OK if you think in terms of a one dimensional sweet spot but it doesn't have any advantages so I would say it's not worth considering.
jackinnj: That would be one of those black box tricks where you get a flat frequency response output under sine wave conditions but it sound like ****. Fortunately that's not what we would be doing. Anyway, the resulting system has to pass other standard tests as well; impulse, step, waterfall, group delay, etc. Oh, it's got to sound good too!
Right now, my workbench is in disarray due to some remodeling so I haven't begun to breadboard anything. But, there are some interesting possibilites floating around in my mind on the active filter end of things.
It would be great if someone could suggest a tweeter with low resonace and ferrofluid at a reasonable price.
The low resonance is essential because otherwise the tweeters acoustical phase (time if You prefer) response would srew up the desired crossover behavier by interacting with the crossover response at the Mid/Tweeter point. IMHO the resonance should be at least 10 times (>3 octaves) away from the crossing point. The more the better.
Here some 1" dome tweeters that might be suitable
Ferrofluid:
Scan Speak D2905/930000; fres= 650Hz
Scan Speak D2905/950000; fres= 550Hz
Seas Excel T25CF001; fres= 650Hz
Thiel C23; fres= 500Hz (Ceramic diaphragm)
Non-Ferrofluid:
Vifa XT25TG30-04; Ringradiator; fres= 500Hz
Scan Speak D2905/970000; fres= 500Hz
Scan Speak D2905/990000; fres= 500Hz
Scan Speak R2904/700000; Ringradiator; fres= 520Hz (extremly expensive)
Unfortunately all of this drivers unless the Vifa Ringradiator (but it has no ferrofluid) are quite expensive but I don`t know any other which might be suitable also (unless perhaps a few ribbons which are even more expensive).
The only other way to go as I see it would be to electronically equalize (Linkwitz circuit) the resonance of a cheaper driver to lower frequencies. This also would have the benefit that the high Xover point restriction could be weakened somewhat and that it could be changed to maybe 3,5kHz (depending of the final highpass slope of course) or so what again would have positive influence regarding lobing in multidriver midrange configurations (arrays) .
Otherwise, as the upper Xover point has to be around 5kHz very likely due to the mentioned restriction, Ferrofluid may not be absolutely neccessary IMHO.
Me too thinks that such a long line array for the midrange might cause troubles since due to the neccessary relatively high Xover point and the required flat slopes there may be serious lobing effects which extremly restrict the vertical listener position. From such an configuration I expect huge frequency deviations (and of course changes of the shape of the "square" as well) only when the vertical position is changed by very few centimeters (You`ll need two different chairs for two listeners of different height).
A Jordan JX92 indeed might be one of the very few choices for a MT configuration and if it sounds as excellent as the other Jordans (I only know the JX53) it would be hard to overcome (quality) soundwise (but I have to admit I don`t know the Tangbands) .
Also an option could be the Jordan JX62 in an MTM configuration or maybe even MMTMM if higher SPL is desired.
I´m aware that we can`t always get everything what we want at one time and that there are to make compromises and that on axis reponse is the number 1 issue here but excessive bad vertical off axis behaviour due to lobing could spoil the "square wave" approuch to some extend though IMHO. Therefore by all means I believe that a MT or in case of multiple midrange driver configurations a MTM or MMTMM arrangement will give more freedom regarding vertical lobing effects in this design.
Let them float yet and into here Bill
Maybe some of us can contribute something useful.
Square-waves and microphones:
Even though microphones are not perfect (in fact nothing in sound recording and reproduction is), good ones might introduce less temporal deviations than loudspeakers since they are very small FR transducers.
I.e. their step response will never look as bad as the step response of a conventional multiway speaker where the responses of all the different frequency-range's drivers arrive one after each other. So a good microphone will be a valid piece of test equipment to see the improvement in square-wave response over a conventional multiway speaker.
Midrange arrays:
Why not try what has already been done: The outer drivers are taken back in level by an additional lowpass filter in the frequency range where lobing starts to be a problem. The delay, introduced by this lowpass, can help the arrangement to behave like a point source. This has already been done with some ESLs to reduce lobing by arranging the stators in segments that are driven seperately. I was also able to listen to a small Swiss-made active speaker where they did the same (It was a WWTWW arrangement). Where the cone area is needed most (at the lower end) all drivers are working together. The upper response drop might be equalised actively.
I know that this adds complexity so I would first start with two FR drivers in the midrange (MTM) and try such tricks afterwards.
Regards
Charles
Even though microphones are not perfect (in fact nothing in sound recording and reproduction is), good ones might introduce less temporal deviations than loudspeakers since they are very small FR transducers.
I.e. their step response will never look as bad as the step response of a conventional multiway speaker where the responses of all the different frequency-range's drivers arrive one after each other. So a good microphone will be a valid piece of test equipment to see the improvement in square-wave response over a conventional multiway speaker.
Midrange arrays:
Why not try what has already been done: The outer drivers are taken back in level by an additional lowpass filter in the frequency range where lobing starts to be a problem. The delay, introduced by this lowpass, can help the arrangement to behave like a point source. This has already been done with some ESLs to reduce lobing by arranging the stators in segments that are driven seperately. I was also able to listen to a small Swiss-made active speaker where they did the same (It was a WWTWW arrangement). Where the cone area is needed most (at the lower end) all drivers are working together. The upper response drop might be equalised actively.
I know that this adds complexity so I would first start with two FR drivers in the midrange (MTM) and try such tricks afterwards.
Regards
Charles
phase_accurate:
Good point on the array.
I have yet to build and listen to a curved array but it might offer a solution should the lobing be unacceptable.
Right now I'm finishing up a woofer project that is tied to the structure of the house. I've always had excellent results from bolting down woofers but this time, as confirmed by a frequency sweep, a nearby gas fireplace is being exited at several frequencies. I'm going to have to get into it and find the offending areas.
When that's done I'll make a curved array of probably 8 or 12 small Tangbands per channel and see if my ears are happy with it. I have been considering an additional driver with a larger voice coil on the rear of the array to eliminate the need for step response equalization. Anyone have any thoughts on this?
Good point on the array.
I have yet to build and listen to a curved array but it might offer a solution should the lobing be unacceptable.
Right now I'm finishing up a woofer project that is tied to the structure of the house. I've always had excellent results from bolting down woofers but this time, as confirmed by a frequency sweep, a nearby gas fireplace is being exited at several frequencies. I'm going to have to get into it and find the offending areas.
When that's done I'll make a curved array of probably 8 or 12 small Tangbands per channel and see if my ears are happy with it. I have been considering an additional driver with a larger voice coil on the rear of the array to eliminate the need for step response equalization. Anyone have any thoughts on this?
Hi Bill,
How about a tall diamond shaped baffle. Narrow at the top and bottom and wide in the middle. Conceptually, this can be combined with Phase-Accurate’s approach of using passive equalization on some of the mid drivers. Instead of a lo-pass on the top and bottom drivers, you progressively step the level down (with resistors only) as you move from the top and bottom toward the center. The diamond shaped baffle will spread the baffle step over a much broader range, and the progressive drop in level will provide compensation for the drivers most affected by the baffle step. You also get away from the lo-pass phase shift.
What do ya think?
Rodd Yamas***a
How about a tall diamond shaped baffle. Narrow at the top and bottom and wide in the middle. Conceptually, this can be combined with Phase-Accurate’s approach of using passive equalization on some of the mid drivers. Instead of a lo-pass on the top and bottom drivers, you progressively step the level down (with resistors only) as you move from the top and bottom toward the center. The diamond shaped baffle will spread the baffle step over a much broader range, and the progressive drop in level will provide compensation for the drivers most affected by the baffle step. You also get away from the lo-pass phase shift.
What do ya think?
Rodd Yamas***a
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