Hi all..
From what I've read, conventional wisdom holds that crossover points should try to leave as much of the 150Hz-4KHz range as possible covered by a single driver, in order to gain coherence.
However, there is a gap around 1000-1500Hz where our ears have little directivity (interaural timing cues are most useful at low frequencies (especially <1KHz), whereas interaural amplitude difference cues are most useful at high frequencies (especially >4KHz), and neither is very effective around 1KHz-1.5KHz). Also, while our ears are fairly sensitive to level in this range, it is not nearly as bad as e.g. around 3-4KHz. And at this frequency, beaming is not nearly as much of an issue, hence the off-axis response should not differ much between the drivers.
It would seem that placing a very steep filter (4th order or higher) around 1250Hz could offer good imaging at the expense of little else.
Many tweeters, including e.g. the Stage Accompany ribbons, can be crossed over this low, if the crossover is steep. Notably, the Seas coax drivers, with their already excellent imaging, might be able to deal with this, since their 1200Hz resonance is well damped.
Opinions on this, or experiences with such an approach?
From what I've read, conventional wisdom holds that crossover points should try to leave as much of the 150Hz-4KHz range as possible covered by a single driver, in order to gain coherence.
However, there is a gap around 1000-1500Hz where our ears have little directivity (interaural timing cues are most useful at low frequencies (especially <1KHz), whereas interaural amplitude difference cues are most useful at high frequencies (especially >4KHz), and neither is very effective around 1KHz-1.5KHz). Also, while our ears are fairly sensitive to level in this range, it is not nearly as bad as e.g. around 3-4KHz. And at this frequency, beaming is not nearly as much of an issue, hence the off-axis response should not differ much between the drivers.
It would seem that placing a very steep filter (4th order or higher) around 1250Hz could offer good imaging at the expense of little else.
Many tweeters, including e.g. the Stage Accompany ribbons, can be crossed over this low, if the crossover is steep. Notably, the Seas coax drivers, with their already excellent imaging, might be able to deal with this, since their 1200Hz resonance is well damped.
Opinions on this, or experiences with such an approach?
You would really need an robust tweeter to cross this low. SL crosses the orion at about 1400Hz if I remember correctly, but it is all active and I'm sure very steep. Otherwise, you will drive the tweeter into areas where it will distort very easily, even with a well damped resonance peak. Is it possible with the correct tweeter, definitely, but I think a more realistic target would be the 1.5Khz to 2Khz range. I find my designs often end up just above this, from about 2k to 2.5k...things just seem to fall in place in that range.
angel,
Jon Marsh (http://www.htguide.com/forum/forumdisplay.php4?f=6) uses steep Cauer filters to implement crossovers at the frequencies you suggested. Surely this appraoch has benefits. Why not join there and discuss the matter with him? He is a prolific designer and is well respected.
Jon Marsh (http://www.htguide.com/forum/forumdisplay.php4?f=6) uses steep Cauer filters to implement crossovers at the frequencies you suggested. Surely this appraoch has benefits. Why not join there and discuss the matter with him? He is a prolific designer and is well respected.
The SA driver is meant to be croosed in that area and i had the opportunity to hear an SA monitor that was driven actively. It sounded very clean at an insanely high SPL so one can assume that the "tweeter" didn't have to struggle.
IMO if done right (which accounts for almost anything in engineering) a crossover frequency of 1 kHz can be as good as any other one. But you need to use suitable drivers.
Regards
Charles
IMO if done right (which accounts for almost anything in engineering) a crossover frequency of 1 kHz can be as good as any other one. But you need to use suitable drivers.
Regards
Charles
The function of localization you refer to is between the ears, there is nothing that indicates that this findings would have any relevance for crossing between two drivers in the same speaker.
It´s a similar "false" logic that suggest that the ears are most sensible to crossing at 3-5k only becasue the spl sensitivity of the ear is highest there. Again there is nothing that suggest that this would be the case.
/Peter
It´s a similar "false" logic that suggest that the ears are most sensible to crossing at 3-5k only becasue the spl sensitivity of the ear is highest there. Again there is nothing that suggest that this would be the case.
/Peter
Hi Graham, good stuff you are doing on the other side. I have never done a passive or Cauer in that region, just an active 4th order a la SL, but just a little bit lower at 1200, and indeed it works well with a Seas 27 TDFC. The Cauer topology should do much better, but I can endorse what you've said. Indeed, very good clarity. A reduction in energy storage I suppose.
Here's my design (Orion variant) which uses a waveguide loaded XT19 XO'd at 1.3k LR8
http://photos.yahoo.com/ph//my_photos
http://photos.yahoo.com/ph//my_photos
Attachments
![a2e9[1].jpg](/community/data/attachments/28/28575-483a6c0ef910e294804da2ebaffed7cd.jpg)
Pan said:
If you are familiar with the neural network model that is used to model this, it has some relevance. Also, unless you have headphones, the same signal is going to arrive at both ears with a difference in level and timing. Even with a single source.
Similarly, I think using a transconductance output with a lowpass on the input and a lowpassed voltage feedback to transition to voltage drive around 1250Hz would improve fidelity and imaging. The main issues with feedback, such as high order harmonics and phase turn become less relevant at high frequencies, due to the natural lack of phase sensitivity at these frequencies, as well as the harmonics ending up in a very insensitive region that is poorly covered by resonators and nerve cells. The main issues with low feedback, such as poor damping and level consistency, become less important at low frequencies, due to poor level sensitivity and level resolution, as well as harmonics due to current drive being lower.
I did not mean to imply that.
angel said:
With the right drivers - like a good low distortion high sensitivity 10 and a suitable treble driver (I like the large Heils) and a good 4th order active network you can obtain coherancy of reproduction that can blow you away. In other words I have had excellent results crossing over 1-1.5K. The larger ribbons will work here too but they give up too much in dynamics and shear output for my tastes. I also like to just run the 10 down to 200-250 cycles and actively cross over to a good high sensitivity low distortion 15 for the bass.
Re: Re: Crossovers in the 1KHz region
That is what I suspected. How large drivers can you cross over to the tweeter? I'd think the limit is about 13", based on the off-axis response.
Do you find the SA8535 to have inadequate dynamics and sheer output (by which I assume you mean effective SPL at listening position)? Considering how it can deliver as much as 137dB(IIRC) at 1m, that makes me wonder..
I do agree, though, that sometimes you need a lot of power to really achieve high fidelity. For example, some rifle shots are louder than regular systems are able to reproduce, etc..
You mention crossing over at 200-250 Hz... in this range, the ear should be fairly insensitive to amplitude, but very sensitive to phase. What are your experiences in this regard?
Magnetar said:
That is what I suspected. How large drivers can you cross over to the tweeter? I'd think the limit is about 13", based on the off-axis response.
Do you find the SA8535 to have inadequate dynamics and sheer output (by which I assume you mean effective SPL at listening position)? Considering how it can deliver as much as 137dB(IIRC) at 1m, that makes me wonder..
I do agree, though, that sometimes you need a lot of power to really achieve high fidelity. For example, some rifle shots are louder than regular systems are able to reproduce, etc..
You mention crossing over at 200-250 Hz... in this range, the ear should be fairly insensitive to amplitude, but very sensitive to phase. What are your experiences in this regard?
Re: Re: Re: Crossovers in the 1KHz region
Originally posted by angel [/i]
That is what I suspected. How large drivers can you cross over to the tweeter? I'd think the limit is about 13", based on the off-axis response.
A 15 - even one with a curvalinear cone with good on axis response to 5K - does not do the disappearing act nearly as well. I suppose it's do to the narrowing of the radiation of the large driver and it's altered reflected/off axis non-linear response. I have a pair that measures nearly flat to 5K and I think they sound best crossed below 500 Hz. The 16's I've used aren't a whole lot better. I think an 8 or 10 is the way to go. I choose the 10's because I have so many of them here to play with.
Do you find the SA8535 to have inadequate dynamics and sheer output (by which I assume you mean effective SPL at listening position)? Considering how it can deliver as much as 137dB(IIRC) at 1m, that makes me wonder..
I do agree, though, that sometimes you need a lot of power to really achieve high fidelity. For example, some rifle shots are louder than regular systems are able to reproduce, etc..
You mention crossing over at 200-250 Hz... in this range, the ear should be fairly insensitive to amplitude, but very sensitive to phase. What are your experiences in this regard?
That particular ribbon (aren't they a planar that have a fan cooled coil?) probably is an exeption. I mean the Arum Cantus, Raven, Philips, suspended type ribbons. They are too fragile and tend to sound compressed or break when asked to reproduce loud 1-2K sounds.
Surely a gunshot facsimile signal into the Heils crossed with a 4th - 8th order network would require several hundred (maybe thousands) of watts to sound real.
AFA phase vs frequency at 200 Hz I really haven't measured or thought too much about that. I do like using a sealed woofer with much higher bandwith past 200 and a midrange with bandwith below 200 crossed with a 4th order electronic crossover over one where the woofer or mid is near it's limits at the crossover point. Seems most cones run into problems with phase when approaching the resonance point and even worse when stuck in a double hump reflex box.
Originally posted by angel [/i]
That is what I suspected. How large drivers can you cross over to the tweeter? I'd think the limit is about 13", based on the off-axis response.
A 15 - even one with a curvalinear cone with good on axis response to 5K - does not do the disappearing act nearly as well. I suppose it's do to the narrowing of the radiation of the large driver and it's altered reflected/off axis non-linear response. I have a pair that measures nearly flat to 5K and I think they sound best crossed below 500 Hz. The 16's I've used aren't a whole lot better. I think an 8 or 10 is the way to go. I choose the 10's because I have so many of them here to play with.
Do you find the SA8535 to have inadequate dynamics and sheer output (by which I assume you mean effective SPL at listening position)? Considering how it can deliver as much as 137dB(IIRC) at 1m, that makes me wonder..
I do agree, though, that sometimes you need a lot of power to really achieve high fidelity. For example, some rifle shots are louder than regular systems are able to reproduce, etc..
You mention crossing over at 200-250 Hz... in this range, the ear should be fairly insensitive to amplitude, but very sensitive to phase. What are your experiences in this regard?
That particular ribbon (aren't they a planar that have a fan cooled coil?) probably is an exeption. I mean the Arum Cantus, Raven, Philips, suspended type ribbons. They are too fragile and tend to sound compressed or break when asked to reproduce loud 1-2K sounds.
Surely a gunshot facsimile signal into the Heils crossed with a 4th - 8th order network would require several hundred (maybe thousands) of watts to sound real.
AFA phase vs frequency at 200 Hz I really haven't measured or thought too much about that. I do like using a sealed woofer with much higher bandwith past 200 and a midrange with bandwith below 200 crossed with a 4th order electronic crossover over one where the woofer or mid is near it's limits at the crossover point. Seems most cones run into problems with phase when approaching the resonance point and even worse when stuck in a double hump reflex box.
Re: Re: Re: Re: Crossovers in the 1KHz region
Are there any particular coaxial drivers you have had good experiences with?
I'm considering the Seas coaxial drivers, but they are limited to 8"..
That is as I assumed. They can reach over 120dB without fan cooling and without a waveguide.
Probably. The SA8535 can do 1KW; 2KW if fan cooled.
Magnetar said:
Are there any particular coaxial drivers you have had good experiences with?
I'm considering the Seas coaxial drivers, but they are limited to 8"..
That is as I assumed. They can reach over 120dB without fan cooling and without a waveguide.
Probably. The SA8535 can do 1KW; 2KW if fan cooled.
Re: Re: Re: Re: Re: Crossovers in the 1KHz region
I have some early Altec 604-8G's that are pretty good within there limitations (soft bass, non-linear treble, beaming upper mids) - many people swear by them. They are pretty sensitive at around 100 db with a watt and are nearly fullrange in the bass. Compared to a good quad amped high efficiency four way they sound like toys. I've heard the early Tannoy Gold 15's in corner cabinets driven by large Mac mono amps and they appear to be a bit more linear in the mids. I really don't know of any good fullrange coaxials in production today - maybe something (a 12 or 15") from Tannoy?
The little SEAS would make a good high passed satellite for low level listening I suppose.
angel said:
I have some early Altec 604-8G's that are pretty good within there limitations (soft bass, non-linear treble, beaming upper mids) - many people swear by them. They are pretty sensitive at around 100 db with a watt and are nearly fullrange in the bass. Compared to a good quad amped high efficiency four way they sound like toys. I've heard the early Tannoy Gold 15's in corner cabinets driven by large Mac mono amps and they appear to be a bit more linear in the mids. I really don't know of any good fullrange coaxials in production today - maybe something (a 12 or 15") from Tannoy?
The little SEAS would make a good high passed satellite for low level listening I suppose.
Considering that many tweeters have resonance frequencies of 500 Hz or so, you would think that crossovers around 1,000 Hz would be common.
Near the resonance point of any speaker, you have transient overshoot, etc, not to mention impedance issues, (except maybe for aperiodic designs).
But these concerns disappear an octave above the resonance frequency, and 1,000 Hz to 1,200 Hz is certainly that.
I think the reason commercial manufacturers rarely do it is that they are concerned about too much power going to the tweeter if it is crossed over at 1,000 Hz.
If, when music is playing, you take the controls of an equalizer and boost the frequencies from 200 Hz to 800 Hz, you will hear a large increase in the general volume of the music.
If you boost from 1,200 Hz to 4,000 Hz, the volume level of the music will not seem to rise nearly so much. And boosting the bands higher than 3,000 Hz results in even less rise in the general volume.
From which we may conclude, that most of the music is centered between 200 Hz and 800 Hz, at least in regards to higher frequencies.
When a designer crosses over at 2,000 or 2,500 Hz, he is making sure the tweeter is only playing the frequency bands that are likely to be reduced in volume from the 200 Hz to 800 Hz midband. That gives him a margin of safety as far as blown tweeters go.
When he moves the crossover point down to 1,000 Hz to 1,200 Hz, he exposes the tweeter to more of the high volume band. The closer the crossover point gets to 200 Hz to 800 Hz, the louder the volume gets, in most music.
Fortunately, as the speaker builders here have demonstrated, the tweeters apparently can take it. But they are only building their loudspeakers for their own personal listening. If they were building a run of 5,000 units, for instance, I would think that moving the crossover point downward will result in a lot more blown tweeters to deal with than a crossover point of 2,500 will produce.
I'm not saying a majority of units will blow the tweeter. I'm sure most of them won't. But the rate of tweeter failure is likely to go up the farther the crossover point goes down, and eat into the profit picture.
that is why it is probably not done commercially. On the other hand, what the designers for their systems at home might be another matter....
Near the resonance point of any speaker, you have transient overshoot, etc, not to mention impedance issues, (except maybe for aperiodic designs).
But these concerns disappear an octave above the resonance frequency, and 1,000 Hz to 1,200 Hz is certainly that.
I think the reason commercial manufacturers rarely do it is that they are concerned about too much power going to the tweeter if it is crossed over at 1,000 Hz.
If, when music is playing, you take the controls of an equalizer and boost the frequencies from 200 Hz to 800 Hz, you will hear a large increase in the general volume of the music.
If you boost from 1,200 Hz to 4,000 Hz, the volume level of the music will not seem to rise nearly so much. And boosting the bands higher than 3,000 Hz results in even less rise in the general volume.
From which we may conclude, that most of the music is centered between 200 Hz and 800 Hz, at least in regards to higher frequencies.
When a designer crosses over at 2,000 or 2,500 Hz, he is making sure the tweeter is only playing the frequency bands that are likely to be reduced in volume from the 200 Hz to 800 Hz midband. That gives him a margin of safety as far as blown tweeters go.
When he moves the crossover point down to 1,000 Hz to 1,200 Hz, he exposes the tweeter to more of the high volume band. The closer the crossover point gets to 200 Hz to 800 Hz, the louder the volume gets, in most music.
Fortunately, as the speaker builders here have demonstrated, the tweeters apparently can take it. But they are only building their loudspeakers for their own personal listening. If they were building a run of 5,000 units, for instance, I would think that moving the crossover point downward will result in a lot more blown tweeters to deal with than a crossover point of 2,500 will produce.
I'm not saying a majority of units will blow the tweeter. I'm sure most of them won't. But the rate of tweeter failure is likely to go up the farther the crossover point goes down, and eat into the profit picture.
that is why it is probably not done commercially. On the other hand, what the designers for their systems at home might be another matter....
If crossing over at 1,000 Hz to 2,000 Hz results in a better sound, and I suspect it might, a variation of the 2 1/2 way system suggests itself.
Instead of using two woofers, one of which fades off below the crossover point, use two tweeters, one of which fades off above the crossover point.
In other words, set up two tweeters above the woofer. One tweeter-the one closest to the rim of the bass/mid-goes from 1,000 Hz on up. Let's call this the primary tweeter.
The secondary tweeter-the one above the first tweeter-goes from 1,000 Hz to 2,000 Hz, then gradually rolls off from there.
Advantages? Suppose we have a six inch bass/mid and two one inch tweeters, 2 inches across at the faceplate.
Using a pair of tweeters, at the crossover frequncy of 1,000 Hz, the center to center spacing will be 5 inches, less than half of the crossover wavelength. It would only be 4 inches for a single tweeter.
However, somewhere around 5,000 Hz or so we might see lobing effects between the tweeter pair. So the top tweeter-the one not near the bass/mid rim-should be rolled off well before then.
But in the 1,000 Hz to 2,000 Hz range, there is the topmost tweeter, operating full force, helping out the primary tweeter both excursion wise and power dissipation wise. Then the secondary tweeter gradually disappears as it is no longer needed.
A 2 1/2 way system using tweeters instead of woofers.
I have not really tried this approach, just suggesting it. I'm sure it has been done already by somebody. It would seem to be one way to get the benefits of a low crossover point while avoiding the dangers of doing so.
Instead of using two woofers, one of which fades off below the crossover point, use two tweeters, one of which fades off above the crossover point.
In other words, set up two tweeters above the woofer. One tweeter-the one closest to the rim of the bass/mid-goes from 1,000 Hz on up. Let's call this the primary tweeter.
The secondary tweeter-the one above the first tweeter-goes from 1,000 Hz to 2,000 Hz, then gradually rolls off from there.
Advantages? Suppose we have a six inch bass/mid and two one inch tweeters, 2 inches across at the faceplate.
Using a pair of tweeters, at the crossover frequncy of 1,000 Hz, the center to center spacing will be 5 inches, less than half of the crossover wavelength. It would only be 4 inches for a single tweeter.
However, somewhere around 5,000 Hz or so we might see lobing effects between the tweeter pair. So the top tweeter-the one not near the bass/mid rim-should be rolled off well before then.
But in the 1,000 Hz to 2,000 Hz range, there is the topmost tweeter, operating full force, helping out the primary tweeter both excursion wise and power dissipation wise. Then the secondary tweeter gradually disappears as it is no longer needed.
A 2 1/2 way system using tweeters instead of woofers.
I have not really tried this approach, just suggesting it. I'm sure it has been done already by somebody. It would seem to be one way to get the benefits of a low crossover point while avoiding the dangers of doing so.
The problem is, there's really no difference between two tweeters in a "2.5" way scenario as described above, and a true 3-way system with a midrange and tweeter, from a lobing standpoint. The "overlap" range between the two tweeters at the point one of them rolls off and leaves the other, will be no different than using a midrange and a tweeter, with the same order crossover slopes.
In essence, if you're going to do this, why not use a midrange that can handle far more dynamic energy than a tweeter, for the "helper" driver?
My thoughts, are that a horn- or waveguide-loaded tweeter has significant advantages in this scheme... the waveguide "beefs up" the output of the tweeter in its lowest octave/octaves, making it possible to roll off the electrical input FAR higher than if the tweeter is located on a flat baffle. This is how Tannoy manages to make a 1" dome handle 1.4Khz without immediately blowing up. Sure, you CAN ultimately blow up a Tannoy dual-concentric tweeter driver... but you REALLY have to be CRANKING it to do so. I work at a Tannoy dealer, and I can count on one hand, the number of replacement tweeter elements for DC drivers, that we've EVER had to order, over the last 10 years...
As for the maximum cone diameter- I personally, wouldn't use anything bigger than as 12" up to 1.5KHz, and preferably, nothing bigger than a 10". I find an 8" driver to be the "sweet spot"... yes, it usually needs a subwoofer or ".5"-driver woofer to help handle the bottom end, but the midrange is amazing...
Regards,
Gordon.
In essence, if you're going to do this, why not use a midrange that can handle far more dynamic energy than a tweeter, for the "helper" driver?
My thoughts, are that a horn- or waveguide-loaded tweeter has significant advantages in this scheme... the waveguide "beefs up" the output of the tweeter in its lowest octave/octaves, making it possible to roll off the electrical input FAR higher than if the tweeter is located on a flat baffle. This is how Tannoy manages to make a 1" dome handle 1.4Khz without immediately blowing up. Sure, you CAN ultimately blow up a Tannoy dual-concentric tweeter driver... but you REALLY have to be CRANKING it to do so. I work at a Tannoy dealer, and I can count on one hand, the number of replacement tweeter elements for DC drivers, that we've EVER had to order, over the last 10 years...
As for the maximum cone diameter- I personally, wouldn't use anything bigger than as 12" up to 1.5KHz, and preferably, nothing bigger than a 10". I find an 8" driver to be the "sweet spot"... yes, it usually needs a subwoofer or ".5"-driver woofer to help handle the bottom end, but the midrange is amazing...
Regards,
Gordon.
GordonW said:
Well, simpler crossover, for one. One cap on the secondary tweeter for the low-pass filter, basically.
However, making my proposal somewhat less desirable is the realization that while there are a few 2" faceplate tweeters on the market, there are few if any with resonance frequencies of 500 Hz or so. Most of those 500 Hz resonance tweeters have 4" faceplates, which worsens the lobing situation.
Still could be done, though.
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