doppler distortion
its not just easy to test for doppler distortion, its also easy to hear. Build a good single driver system and if you had 2 sin sources you can play 1 khz and 40 hz simultaneously and at a reasonable listening level you will definitly hear a warble sound in the 1khz now do the same with a normal 2 or 3 way system you will notice that its far less or none at all depending on the crossover points. Most people dont have 2 signal generators so you pick out music that has alot of low bass and clean vocals. The louder it is played the more of this effect you will hear and it is inversly proportional to the surface area of the cone.
its not just easy to test for doppler distortion, its also easy to hear. Build a good single driver system and if you had 2 sin sources you can play 1 khz and 40 hz simultaneously and at a reasonable listening level you will definitly hear a warble sound in the 1khz now do the same with a normal 2 or 3 way system you will notice that its far less or none at all depending on the crossover points. Most people dont have 2 signal generators so you pick out music that has alot of low bass and clean vocals. The louder it is played the more of this effect you will hear and it is inversly proportional to the surface area of the cone.
Re: doppler distortion
Konnichiwa,
But how do you know that you are hearing/measuring doppler distortion, not just simple intermodulation aused by the magent field non-linearity (or more preciesly the mudulation of BL and thus sensitivity with cone travel)?
So, no doppler distortion, just a not so well designed magnet field.
Sayonara
Konnichiwa,
eric180db said:
But how do you know that you are hearing/measuring doppler distortion, not just simple intermodulation aused by the magent field non-linearity (or more preciesly the mudulation of BL and thus sensitivity with cone travel)?
So, no doppler distortion, just a not so well designed magnet field.
Sayonara
imd nonlinearities
True there will be these components too but not to the extent of the doppler distortion and if you wanted to find out which is which you just look at the measured 1khz fundimental on an "o"-scope or even better on a 1/3 octave spectrum analyzer. The scope will show the wavelength changing with the low frequency component (an effect that will not happen with IMD or HD) the spectrum analyzer will actually show a flickering around the 1khz mark causing the next octave up and down to modulate. Before arguing try the experement for yourself and see if you can explain the results.
True there will be these components too but not to the extent of the doppler distortion and if you wanted to find out which is which you just look at the measured 1khz fundimental on an "o"-scope or even better on a 1/3 octave spectrum analyzer. The scope will show the wavelength changing with the low frequency component (an effect that will not happen with IMD or HD) the spectrum analyzer will actually show a flickering around the 1khz mark causing the next octave up and down to modulate. Before arguing try the experement for yourself and see if you can explain the results.
I am considering using a fullrange for HT. the fullrange will be supported by the LF out (subwoofer signal).
does the fullrange have to operate in the bass (below 100Hz) or is it ok to use a fullrange that is bandwidth limited. The reasons I ask this is that I am hoping to get by with a small box (10-12 liters) and that means a small driver (max 5"). and a small driver will not produce much below 100hz at any thing close to HT levels.
reasons for using fullrange
1. no need for XO design or XO losses
2. the box can be oriented verticaly or horizontally without worrying about polar response changes like one would in a MT.
right now I am leaning towards the JX92. Only I wonder if it's LF and HF response would be adequate for HT. How would one compate the sound of a small fullrange (so far I have only heard the Manger with 8" Vifa woofer, a large Fostex and the Lowther and that too only in audio mode not HT) to say that of a small 5" 2 way monitor?
another option is to use a wide range with a small woofer. like a Fostex FF85K with a Vifa PL 11WH, Seas CA11RCY, Audax HM100G0 and XO at about 400-600Hz. However most of these small woofers have response that is very good upto 3000Hz+. In that case does it make sense to use such a woofer with a small format tweeter like the Seas CT25AF or Vifa D26NC or Audax TM010?
lastly if one were to use a small wide range like the FF85K in a 1.5 way with a small 4" woofer (no XO on the woofer) there will be considerable overlap between say 500Hz and 5k. How would this affect the sound? The reaons for this is that a passive 1st order LP XO at 500hz would require a large cap that would be detrimental or expensive or both.
does the fullrange have to operate in the bass (below 100Hz) or is it ok to use a fullrange that is bandwidth limited. The reasons I ask this is that I am hoping to get by with a small box (10-12 liters) and that means a small driver (max 5"). and a small driver will not produce much below 100hz at any thing close to HT levels.
reasons for using fullrange
1. no need for XO design or XO losses
2. the box can be oriented verticaly or horizontally without worrying about polar response changes like one would in a MT.
right now I am leaning towards the JX92. Only I wonder if it's LF and HF response would be adequate for HT. How would one compate the sound of a small fullrange (so far I have only heard the Manger with 8" Vifa woofer, a large Fostex and the Lowther and that too only in audio mode not HT) to say that of a small 5" 2 way monitor?
another option is to use a wide range with a small woofer. like a Fostex FF85K with a Vifa PL 11WH, Seas CA11RCY, Audax HM100G0 and XO at about 400-600Hz. However most of these small woofers have response that is very good upto 3000Hz+. In that case does it make sense to use such a woofer with a small format tweeter like the Seas CT25AF or Vifa D26NC or Audax TM010?
lastly if one were to use a small wide range like the FF85K in a 1.5 way with a small 4" woofer (no XO on the woofer) there will be considerable overlap between say 500Hz and 5k. How would this affect the sound? The reaons for this is that a passive 1st order LP XO at 500hz would require a large cap that would be detrimental or expensive or both.
Re: imd nonlinearities
Konnichiwa,
You are right, they will be not to the extent of the doppler distortion, they will many times as high.
Will it? Sure?
Why don't you just stop repeating the same old fairytales?
http://sound.westhost.com/doppler.htm
Sayonara
Konnichiwa,
eric180db said:
You are right, they will be not to the extent of the doppler distortion, they will many times as high.
eric180db said:
Will it? Sure?
Why don't you just stop repeating the same old fairytales?
http://sound.westhost.com/doppler.htm
Sayonara
Re: imd nonlinearities
(JPK) Doppler distortion IS IM distortion. See my analysis at http://www.geocities.com/kreskovs/Doppler1.html and check some measured results at http://www.geocities.com/kreskovs/Doppler2.html
It is true that you can seperate motor induced IM and cone motion induced doppler (IM) but the analysis clears shows that Doppler distortion (cone motion generated) is identical to, and there fore is IM distortion. You won't see flickering on a spectrum analizer, just the fundamentals and the IM side bands. On a scope you will see the higher frequency "riding the wave" of the low frequnecy like a cork bobbing over ripples in a pond. The peaks in the high frequency will ride up and down and back and fourth as the low frequency modulates it.
eric180db said:
(JPK) Doppler distortion IS IM distortion. See my analysis at http://www.geocities.com/kreskovs/Doppler1.html and check some measured results at http://www.geocities.com/kreskovs/Doppler2.html
It is true that you can seperate motor induced IM and cone motion induced doppler (IM) but the analysis clears shows that Doppler distortion (cone motion generated) is identical to, and there fore is IM distortion. You won't see flickering on a spectrum analizer, just the fundamentals and the IM side bands. On a scope you will see the higher frequency "riding the wave" of the low frequnecy like a cork bobbing over ripples in a pond. The peaks in the high frequency will ride up and down and back and fourth as the low frequency modulates it.
John is, of course quite correct that Doppler distortion is real. We are all just so used to hearing it that we don't recognize it for what it is. SL also did an analysis along with measurements to confirm its accuracy.
http://www.linkwitzlab.com/frontiers.htm#J
http://www.linkwitzlab.com/images/graphics/doppler1.gif
Short formula for the magnitude (I originally derived this from John's stuff and SL's formulas agree.)
Doppler distortion % = 0.91 * (max 1-way excursion in mm) * (highest freq in kilohertz)
An example, since we're talking full range drivers, say the max excursion is 1 mm and the highest F is 10kHz. The amplitude of the sidebands will be about 9% of the 10kHz tone or a bit over 20dB down. That's a pretty high distortion number and, in addition, you aren't going to get much bass out of a small driver only moving 1 mm.
http://www.linkwitzlab.com/frontiers.htm#J
http://www.linkwitzlab.com/images/graphics/doppler1.gif
Short formula for the magnitude (I originally derived this from John's stuff and SL's formulas agree.)
Doppler distortion % = 0.91 * (max 1-way excursion in mm) * (highest freq in kilohertz)
An example, since we're talking full range drivers, say the max excursion is 1 mm and the highest F is 10kHz. The amplitude of the sidebands will be about 9% of the 10kHz tone or a bit over 20dB down. That's a pretty high distortion number and, in addition, you aren't going to get much bass out of a small driver only moving 1 mm.
OK... we now know that there are problems associated with full-range drivers. We also know that they have advantages, primarily because there is no (or limited) need for additional components.
Then what is the problem with the following:
Use a full-range driver for the frequency range, say, 300 Hz to 6kHz
Use a 6" woofer below this, and a tweeter for the highs, wach with simple 1. order filters.
Funny phases from complex filters would be avoided, costs are reasonable, and there are no XO frequencies where it really hurts (where the ear is most sensitive).
I haven't build such one (haven't built ANY speakers yet, actually).
However, I would like to give it a try some day, and have found tons of information in this forum. Thus, I would like to have comments on this approach, hoping it's not too far off topic.
Jennice
Then what is the problem with the following:
Use a full-range driver for the frequency range, say, 300 Hz to 6kHz
Use a 6" woofer below this, and a tweeter for the highs, wach with simple 1. order filters.
Funny phases from complex filters would be avoided, costs are reasonable, and there are no XO frequencies where it really hurts (where the ear is most sensitive).
I haven't build such one (haven't built ANY speakers yet, actually).
However, I would like to give it a try some day, and have found tons of information in this forum. Thus, I would like to have comments on this approach, hoping it's not too far off topic.
Jennice
Jennice, I don't think that there's anything at all wrong with proceeding as you've suggested and it could make an excellent construction project for you.Jennice said:
I would tend to go a little higher than 6kHz, say 9kHz, particularly with 1st order crossovers, and perhaps take the lower crossover down a little for the same reason.
I would recommend either an open baffle approach or an 'egg' type enclosure for your main driver (but that's me).
I believe that you could end up with something way better than most of the commercial products out there.
Konnichiwa,
Problems have solutions....
The problem is that your first X-over is smack bang in the Formant Range of many instruments and your second in the middle of the upper harmonics.
Consider dropping the first X-Over as close to 100Hz (or lower) as power handling of the Fullrange Driver allows. Secondly, leave the Fullrange driver running "open top", with no lowpass. Select a Fullrange that rolls of nicely and supplement the top using a suitable high overtone reproducer (Supertweeter in Neo-Audio English).
I did that sort of thing back in the mid 1980's. I had a long going active speaker project that started like this:
Dual 8" Sealed Woofer Section
Singe 5" Fullrange (no Whizzer)
Single 1" Supronyl Dome tweeter
Starting point where Low Order X-Overs (active) at 250Hz/5KHz. Later versions left the Fullrange running without lowpass and with a suitable highpass and current feed on the Fullrange. Tweeter changed to Piezo (motorola) at around 10 - 12KHz with a steep Highpass slope. Woofers eventually went the Servo Way.
You know what? Afer a few years of incermental work on that system it was very good and in all "HiFi" terms whooped the butt of my "normal" speaker. But when it came to making music sound such that I wanted MORE I preferred my other speaker.
That had 2psc of Schulze KSP215 (8" Fullrange Drivers, with Whizzer) in a rather classically aligned vented box, a simple choke on one of the drivers cutting it out at higher frequencies (maybe 500Hz or so).
I also regulary find myself coming back to systems where the main "wideband" or "fullrange" driver is run completely open (no HP, no LP). Even the EPOS ES14 and ES12 I liked, despite having a rather low rolloff point on the main driver, but that rolloff is purely mechanical.
Not sure what the lesson is, except that of "Suck & See".
Sayonara
Jennice said:
Problems have solutions....
Jennice said:
The problem is that your first X-over is smack bang in the Formant Range of many instruments and your second in the middle of the upper harmonics.
Consider dropping the first X-Over as close to 100Hz (or lower) as power handling of the Fullrange Driver allows. Secondly, leave the Fullrange driver running "open top", with no lowpass. Select a Fullrange that rolls of nicely and supplement the top using a suitable high overtone reproducer (Supertweeter in Neo-Audio English).
Jennice said:
I did that sort of thing back in the mid 1980's. I had a long going active speaker project that started like this:
Dual 8" Sealed Woofer Section
Singe 5" Fullrange (no Whizzer)
Single 1" Supronyl Dome tweeter
Starting point where Low Order X-Overs (active) at 250Hz/5KHz. Later versions left the Fullrange running without lowpass and with a suitable highpass and current feed on the Fullrange. Tweeter changed to Piezo (motorola) at around 10 - 12KHz with a steep Highpass slope. Woofers eventually went the Servo Way.
You know what? Afer a few years of incermental work on that system it was very good and in all "HiFi" terms whooped the butt of my "normal" speaker. But when it came to making music sound such that I wanted MORE I preferred my other speaker.
That had 2psc of Schulze KSP215 (8" Fullrange Drivers, with Whizzer) in a rather classically aligned vented box, a simple choke on one of the drivers cutting it out at higher frequencies (maybe 500Hz or so).
I also regulary find myself coming back to systems where the main "wideband" or "fullrange" driver is run completely open (no HP, no LP). Even the EPOS ES14 and ES12 I liked, despite having a rather low rolloff point on the main driver, but that rolloff is purely mechanical.
Not sure what the lesson is, except that of "Suck & See".
Sayonara
Kuei Yang Wang said:
1) What's the formant range (first XO)?
2) The middle of ther upper harmonics... you mean that there's lot's of mucic information there, so I should select a different frequency?
What's a whizzer?
You mean that it was technically good, but almost boringly neutral?
The wide-band would probably be the Vifa TG9WD10-04, one of the few fullrange drivers I know where I can buy. What do you think of it? (data sheet link:
http://www.d-s-t.com/vifa/data/tg9wd-10-04c.htm )
It sounds temptingly simple to rrun a full-range without HP filter, and letting it mechanically roll offf at the low end, but I fear it will seriously be limiting the power handling of the final speaker. After all, it will have to play loud at times, and my concern is that the membrane will be shot across the room
As an alternative, I think I know where to purchase Visaton drivers. Does anyone know about these?
Jennice
Kuei Yang Wang said:
I was looking to do this for a HT-cum-audio system but ran into one more suspicion.
say we use a fullrange like the Jordan JX92 which can be XOed below 100hz and still handle 20W (13dbW) to produce about 100db/1m/100Hz.
put a TL/MLTL/Dipole woofer below 100hz.
so far so good...
if one is to add a tweeter about 8/10k (I was recomended the Hiquphon or Fountek) for the "final octave" and run the fulrange with a LP wont there be some polar interference?
another option is to use a widerange that does not HF help (like the Fostex FF85K) but usually such fullranges cant go much below 300hz which means that one has XO to a small woofer (4-6") and then to a larger woofer below 100hz. I dont like 2 passive XO points so close. I suspect they would interfere unless the system was biamped or triamped. of course one can sacrifice HT requirements of LF and use a pair of 8" instead.
Honnichiwa,
The range where the FORMANTS (that is the first few overtones of the fundamental notes) reside. They are called formant as they "form" the tone. Maybe you wish to study some theory of musical insytrument sound prior to building speakers?
Not quite. What I am saying is that either X-Over you suggested is in the middle of ranges critical to the percieved tone. Change the diaphragm material, mess with the phase and the like and life gets interesting.
As said, all this is basic musical/acoustial theory.
A small second inner cone used on some fullrange speaker sto extend the high requrncy range and to give wider diepsersion oat high frequecies. Please goole for more.
Yes, but also lacking coherence.
That would mean you have chosen a unacceptable fullrange driver.
Sayonara
Jennice said:
The range where the FORMANTS (that is the first few overtones of the fundamental notes) reside. They are called formant as they "form" the tone. Maybe you wish to study some theory of musical insytrument sound prior to building speakers?
Jennice said:
Not quite. What I am saying is that either X-Over you suggested is in the middle of ranges critical to the percieved tone. Change the diaphragm material, mess with the phase and the like and life gets interesting.
As said, all this is basic musical/acoustial theory.
Jennice said:
A small second inner cone used on some fullrange speaker sto extend the high requrncy range and to give wider diepsersion oat high frequecies. Please goole for more.
Jennice said:
Yes, but also lacking coherence.
Jennice said:
That would mean you have chosen a unacceptable fullrange driver.
Sayonara
to revive an old thread...
I've been experimenting with a Fostex FF85K crossed over to two 15's circa 300 hz w/ 4th order slopes.
I'm running the whole thing OB, hence the two 15s per side. I have the 15s EQd flat to close to 20 and they're still barely moving. God bless big pro drivers.
I've spent a lot of time trying different crossover points and slopes. I've ended up with 4th order since I'm running the Fostex only an octave above Fs. It's moving within a small fraction of its available xmax (they really move in and out running them full range, fun to watch).
I'm not set on 300, but in terms of being nonobtrusive it's a good choice. If you run the speaker with the top turned off, you can tell there's not a whole lot detail below 300. I was really worried about cutting the male voice roughly in half, but our lack of sensitivity below 300 predominates. Yes, the fundamentals are shifting between the Fostex and the big drivers, but it's not distracting. It's only noticeable, to me, because I'm specifically looking for it.
I've tested any type of music you can imagine - and there is some IM/breakup with complex music. Interestingly, higher crossover points (300 - 1000) don't seem to alleviate it. But it's at quite high levels (and in mono, which means one driver doing double duty).
Higher crossover points are intrusive tonally in comparison. It's immediately obvious and the sound is worse for it. Of course, all of my favorite manufactured speakers are crossed over in points I wouldn't - but in this speaker there's no comparison. Keep it out of that critical band.
I've also swapped in a Vifa Midbass/Tweeter combo (but not their highest quality stuff) and that lack of coherence is immediately noticeable as well.
The bass? Man, that's a whole other story. Anyone who complains about dipole power needs to use bigger drivers. Are dipoles modal? Yes, not nearly as much as omnis - but we alreay knew that. Do they shake and rattle things if you want them to? Yes, no problem. I know the net pressure change in the room is 0, but everything shakes anyway.
That Fostex is a charmer. It's not a very small full range. It's a very natural sounding tweeter that goes really, really low. Don't underestimate it.
I've been experimenting with a Fostex FF85K crossed over to two 15's circa 300 hz w/ 4th order slopes.
I'm running the whole thing OB, hence the two 15s per side. I have the 15s EQd flat to close to 20 and they're still barely moving. God bless big pro drivers.
I've spent a lot of time trying different crossover points and slopes. I've ended up with 4th order since I'm running the Fostex only an octave above Fs. It's moving within a small fraction of its available xmax (they really move in and out running them full range, fun to watch).
I'm not set on 300, but in terms of being nonobtrusive it's a good choice. If you run the speaker with the top turned off, you can tell there's not a whole lot detail below 300. I was really worried about cutting the male voice roughly in half, but our lack of sensitivity below 300 predominates. Yes, the fundamentals are shifting between the Fostex and the big drivers, but it's not distracting. It's only noticeable, to me, because I'm specifically looking for it.
I've tested any type of music you can imagine - and there is some IM/breakup with complex music. Interestingly, higher crossover points (300 - 1000) don't seem to alleviate it. But it's at quite high levels (and in mono, which means one driver doing double duty).
Higher crossover points are intrusive tonally in comparison. It's immediately obvious and the sound is worse for it. Of course, all of my favorite manufactured speakers are crossed over in points I wouldn't - but in this speaker there's no comparison. Keep it out of that critical band.
I've also swapped in a Vifa Midbass/Tweeter combo (but not their highest quality stuff) and that lack of coherence is immediately noticeable as well.
The bass? Man, that's a whole other story. Anyone who complains about dipole power needs to use bigger drivers. Are dipoles modal? Yes, not nearly as much as omnis - but we alreay knew that. Do they shake and rattle things if you want them to? Yes, no problem. I know the net pressure change in the room is 0, but everything shakes anyway.
That Fostex is a charmer. It's not a very small full range. It's a very natural sounding tweeter that goes really, really low. Don't underestimate it.
Re: to revive an old thread...
How does it compare to others (Tangband W3xxx, Jordan JX6, Veravox 3, etc...) fullranges? I would suspect that the Veravox might be closest to it.
m@ said:That Fostex is a charmer. It's not a very small full range. It's a very natural sounding tweeter that goes really, really low. Don't underestimate it.
How does it compare to others (Tangband W3xxx, Jordan JX6, Veravox 3, etc...) fullranges? I would suspect that the Veravox might be closest to it.
small full range
No idea actually. When I first had the idea I stumbled across the Fostex. I haven't tried anything else.
For me, the criteria is that its top end is comparable to a dome tweeter (full extension, good off axis) and it can reach down comfortably sub 500 hz. I would guess all of those drivers qualify, but I haven't looked into them.
It seems that there has to be some form of decoupling between the center 'tweeter' section and the larger cone. The Fostex seems to do a good job of this with some type of lossy material connecting the 'dome' dust cap and the cone. They've also done a lot of work on the surround, apparently to give it a large xmax while keeping everything as linear as possible. The frame is stamped, but everything else seems to have been given a lot of thought. It's a lot of driver for 30$.
The only question lingering is whether or not there is a lack of dynamics in the lower midrange (compared to the incredible dynamics in the bass). That's the only area where the design is pushing its limits, so I'm wondering if it could be improved. I have yet to do adequate testing to set the EQ and crossover flat, so I'll hold judgement until then.
I have tried filling in the midbass with a different, larger driver, but there is a lack of coherence as the upper XO point then has to be 500 - 600 or higher.
No idea actually. When I first had the idea I stumbled across the Fostex. I haven't tried anything else.
For me, the criteria is that its top end is comparable to a dome tweeter (full extension, good off axis) and it can reach down comfortably sub 500 hz. I would guess all of those drivers qualify, but I haven't looked into them.
It seems that there has to be some form of decoupling between the center 'tweeter' section and the larger cone. The Fostex seems to do a good job of this with some type of lossy material connecting the 'dome' dust cap and the cone. They've also done a lot of work on the surround, apparently to give it a large xmax while keeping everything as linear as possible. The frame is stamped, but everything else seems to have been given a lot of thought. It's a lot of driver for 30$.
The only question lingering is whether or not there is a lack of dynamics in the lower midrange (compared to the incredible dynamics in the bass). That's the only area where the design is pushing its limits, so I'm wondering if it could be improved. I have yet to do adequate testing to set the EQ and crossover flat, so I'll hold judgement until then.
I have tried filling in the midbass with a different, larger driver, but there is a lack of coherence as the upper XO point then has to be 500 - 600 or higher.
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