I stubbled upon this new speaker which is designed by Roger Russell, the designer of the Mac LAs, and his new speaker just uses 25 fullrange 3.5" drivers with EQ (901 like).
http://www.roger-russell.com/columns/columns.htm#single
He claims that combing in columns a myth. So whats the deal. How can so many people claim that combing effects are audible and detract from the performance and now a gentleman with lots of LA experience says its ill effects are corrected in our brains and not a concern. Can simple wiring techique and electronic manipulation eliminate it?
amt
http://www.roger-russell.com/columns/columns.htm#single
He claims that combing in columns a myth. So whats the deal. How can so many people claim that combing effects are audible and detract from the performance and now a gentleman with lots of LA experience says its ill effects are corrected in our brains and not a concern. Can simple wiring techique and electronic manipulation eliminate it?
amt
He's right to an extent. Again, it depends upon the specific circumstances.
Does lobing exist? Yes. It's inescapable unless you invent a new form of physics. Is is a problem? Usually. The drivers need to be closer together than 1 wavelength of the highest frequency they produce to avoid it in the audio band. The attenuation of HF when using FR or WB drivers alone is both audible and measureable, and has been shown innumerable times in both cases. You can (sometimes) bring it back into line with hefty Eq. Is the ripple, i.e. the peaks and dips in the response also audible? Depends how close together they are packed I suspect for psychoacoustic masking to kick in. Our hearing is amplitude based, so we will tend to focus on the peaks. If they're close together, and out of our most sensitive band, you might get away with it. But I wouldn't bet on it either 99.9% of the time. Jim Griffin, or resident line array guru can give some better views than I can thoughm so I'll leave the rest up to him, when he finds the thread, and any of our other array experts.
Does lobing exist? Yes. It's inescapable unless you invent a new form of physics. Is is a problem? Usually. The drivers need to be closer together than 1 wavelength of the highest frequency they produce to avoid it in the audio band. The attenuation of HF when using FR or WB drivers alone is both audible and measureable, and has been shown innumerable times in both cases. You can (sometimes) bring it back into line with hefty Eq. Is the ripple, i.e. the peaks and dips in the response also audible? Depends how close together they are packed I suspect for psychoacoustic masking to kick in. Our hearing is amplitude based, so we will tend to focus on the peaks. If they're close together, and out of our most sensitive band, you might get away with it. But I wouldn't bet on it either 99.9% of the time. Jim Griffin, or resident line array guru can give some better views than I can thoughm so I'll leave the rest up to him, when he finds the thread, and any of our other array experts.
His definition of comb filtering is right. It is the generalised definition for it. Your definition is then one possible variant of it.
But I don't buy his arguments on importance (or lack thereof) of comb-filtering. No one would say that room-reflections and the associated response aberrations are unimportant. Even though our ears are able to correct for some of these aberrations it reproduction is bettewr in some rooms than in others - period.
And just because these aberrations happen in a listening room anyway doesn't mean that they have to be produced at the source already.
Just like selling new cars with rust: "Ahhh .... don't care about it every car will start to rust one day ........ !"
Regards
Charles
But I don't buy his arguments on importance (or lack thereof) of comb-filtering. No one would say that room-reflections and the associated response aberrations are unimportant. Even though our ears are able to correct for some of these aberrations it reproduction is bettewr in some rooms than in others - period.
And just because these aberrations happen in a listening room anyway doesn't mean that they have to be produced at the source already.
Just like selling new cars with rust: "Ahhh .... don't care about it every car will start to rust one day ........ !"
Regards
Charles
In which case "combing" would also occur for a single driver.
I feel My definition is at odds with his and not a variant.
I have read our own guru Jim Griffins paper, so it appears to me a bit different.
Since both gentlemen have good credentials, it is must be that I have not fully grasped the line array fundamentals.
This is how I feel too. I must not really see the big picture. The problem is that the lure of a FR array is great - no crossovers with great efficiency and dynamics. Jim Griffin has done such indepth research, which is published, that I tend to regard him as the word on LAs. But designing products for McIntosh are pretty reasonable credentials too. Could it really be to just make a buck the easy way? Doesnt seem likely but I dont know. I sure would like to hear them.
A PE project used smaller drivers and HF problems were evident but apparently not a huge problem. Maybe electronic correction of some sort is the key.
http://www.partsexpress.com/projectshowcase/Kuze3201/Kuze3201.html
amt
A PE project used smaller drivers and HF problems were evident but apparently not a huge problem. Maybe electronic correction of some sort is the key.
http://www.partsexpress.com/projectshowcase/Kuze3201/Kuze3201.html
amt
He is correct, room influences can cause comb filtering, but general usage is to describe the effects of interfering point sources like speaker arrays. He needs to define his terminology better.
I agree, I really don't go with the principle that you can cure time domain problems by tweaking frequency response.
planet10 said:
I agree, I really don't go with the principle that you can cure time domain problems by tweaking frequency response.
pinkmouse said:
Dude, I guess we all just don't "get" it
It wouldn't be the first time a revolutionary audio designer is frustrated by waiting for his target audience to catch up to the revised laws of physics as He sees them.
- What happens to the contour function of the EQ if you custom order a pair shorter than the stock 89"? Maybe he had some help from Bob Carver on the specs for the EQ - "quantum level temporal corrector" :
We proudly announce a circuit that's not only smart enough to know what you need to hear, regardless of room acoustics or amplifier performance characteristics; but thanks to the patented optional neural implant chip, what you actually are hearing, thereby allowing an unprecedented degree of audio perfection. Of course that may sound revolutionary, but I've got all the math right here. ( Just remember to activate the standby mode when warming your tea in the microwave, we wouldn't want a repeat of that unfortunate Philadelphia incident)
(and yes, I'll not insult you by forgetting to pretend to respect you in the morning) ,
But seriously folks, these things could quite possibly sound very nice indeed, and for only $16,000 per pair .
(did I mention some of the physics sounds like voodoo snake oil?)
I've only used cheapie 4" drivers that fall off sharply above 11khz. All of the arrays I built had at least 12 drivers. Comb filtering is definitely audible using slow tone sweeps as ripples in response. With only 2 drivers the comb effect is obvious and results in the deep null, however, with many drivers in the array there are many different distances to your ears. To me the sonic effect of the individual nulls averaging together, since they occur over many frequencies, is just an attenuation of the high frequencies. My drivers don't go high enough to just EQ up the high end, so I fill in with a tweeter, but I don't see any reason why EQ'g up the response wouldn't work well.
I do have a problem with the imaging claim, because unless you use power tapering, as suggested by Dr. Griffin, I clearly hear sound from the top and bottom drivers since their sound reaches the ear last.
I do have a problem with the imaging claim, because unless you use power tapering, as suggested by Dr. Griffin, I clearly hear sound from the top and bottom drivers since their sound reaches the ear last.
Whether or Not Comb Lines are a Myth
I’m not going to agree as Roger Russell suggests that comb filtering (or comb lines) are a myth but let me describe the effect in more detail. In my opinion Roger goes too far in claiming that comb lines aren’t an issue for line arrays.
I’ll talk first about the horizontal plane comb lining and later address the more important vertical plane. Line arrays and point source speakers will have essentially the same comb lining or filtering characteristics in their horizontal planes so what Russell’s horizontal axis comments are essentially valid. We have very acute ability to discern sounds in the horizontal plane and it is mostly due to head shadowing of our ears. So sounds that arrive from different directions (different times) are easier to discriminate. Furthermore, horizontal axis reflections from room related surfaces (mainly sidewalls) are handled by the Haas or precedence effect in which the ear/brain system plays a role in the first 35 milliseconds or so. The direct or first arrival sound trumps the secondary or reflected sounds for either the line source or point source.
The situation in the vertical plane is different compared to the horizontal plane. With a line array you have significantly different path lengths between the drivers to the listener's ears from those at the end of the array vs. those in the center of the array. The center to center separation between drivers comes into play in the vertical plane. But in the vertical plane our ability to localize sound is significantly less as ears/brain cues (no head shadowing) are more limited. The Haas or precedence effect will also help to integrate sounds in the vertical plane. You can conclude that comb lines are less discernable in the vertical plane than they are in the horizontal plane.
Near field arrays radiate their energy some differently vs. point sources so their vertical radiation characteristics will differ vs. shorter line arrays. In the near field sound energy radiates outward from the source parallel to the floor and ceiling planes. You can stand or squat in front of near field array and the sound will follow you as you move up or down in front of the array. Hence, there is little spreading of the sound so few reflections occur from the ceiling and floor. Essentially, you hear sound from the wavefront as you listen and move up and down. The specific conditions for near field radiation are detailed in my white paper. Those conditions include a specific height of the array and maintaining a center to center separation between drivers less than one wavelength at the highest frequency of operation.
A few comments on Roger Russell’s full range driver line array are that the vertical spacing between the 3.5” diameter drivers indicates that comb lining will start happening above 3874 Hz (one wavelength spacing). The reality is that the amplitude response of his array will be uneven and start to decline above that frequency. Now you can use an equalizer as Russell does to help flatten out the amplitude so that the overall response will be close to acceptable. He does have decreased sensitivity of our ears working for him as you move into the 10-20 kHz region per the Fletcher-Munson curves. Plus as we age our higher frequency hearing starts to diminish so for us older guys this may help cover sound issues in this upper range. My comment on Russell’s array is that I suspect that you will hear ‘phasey’ sound as you move off axis and around the room for music with higher frequency content.
For what it is worth the Darren Kuzma’s 32 driver line array at:
http://www.partsexpress.com/projectshowcase/Kuze3201/Kuze3201.html
in the Parts Express Project Showcase demonstrates what one would have with drivers that are spaced 2.125” c-t-c. Note how Darren’s array shows significant decline of the amplitude response vs. frequency (see the unequalized and equalized plots in his report). An array with 3.5” spacing will have even lower frequency onset of amplitude response roll off.
Now let us take Russell’s no comb lining myth to the limit via using larger drivers or move the drivers even further apart in the array. I suspect that you will quickly hear even more frequency response shortcomings regardless of any equalization. It is not a design approach what I would advise one to pursue.
I’m not going to agree as Roger Russell suggests that comb filtering (or comb lines) are a myth but let me describe the effect in more detail. In my opinion Roger goes too far in claiming that comb lines aren’t an issue for line arrays.
I’ll talk first about the horizontal plane comb lining and later address the more important vertical plane. Line arrays and point source speakers will have essentially the same comb lining or filtering characteristics in their horizontal planes so what Russell’s horizontal axis comments are essentially valid. We have very acute ability to discern sounds in the horizontal plane and it is mostly due to head shadowing of our ears. So sounds that arrive from different directions (different times) are easier to discriminate. Furthermore, horizontal axis reflections from room related surfaces (mainly sidewalls) are handled by the Haas or precedence effect in which the ear/brain system plays a role in the first 35 milliseconds or so. The direct or first arrival sound trumps the secondary or reflected sounds for either the line source or point source.
The situation in the vertical plane is different compared to the horizontal plane. With a line array you have significantly different path lengths between the drivers to the listener's ears from those at the end of the array vs. those in the center of the array. The center to center separation between drivers comes into play in the vertical plane. But in the vertical plane our ability to localize sound is significantly less as ears/brain cues (no head shadowing) are more limited. The Haas or precedence effect will also help to integrate sounds in the vertical plane. You can conclude that comb lines are less discernable in the vertical plane than they are in the horizontal plane.
Near field arrays radiate their energy some differently vs. point sources so their vertical radiation characteristics will differ vs. shorter line arrays. In the near field sound energy radiates outward from the source parallel to the floor and ceiling planes. You can stand or squat in front of near field array and the sound will follow you as you move up or down in front of the array. Hence, there is little spreading of the sound so few reflections occur from the ceiling and floor. Essentially, you hear sound from the wavefront as you listen and move up and down. The specific conditions for near field radiation are detailed in my white paper. Those conditions include a specific height of the array and maintaining a center to center separation between drivers less than one wavelength at the highest frequency of operation.
A few comments on Roger Russell’s full range driver line array are that the vertical spacing between the 3.5” diameter drivers indicates that comb lining will start happening above 3874 Hz (one wavelength spacing). The reality is that the amplitude response of his array will be uneven and start to decline above that frequency. Now you can use an equalizer as Russell does to help flatten out the amplitude so that the overall response will be close to acceptable. He does have decreased sensitivity of our ears working for him as you move into the 10-20 kHz region per the Fletcher-Munson curves. Plus as we age our higher frequency hearing starts to diminish so for us older guys this may help cover sound issues in this upper range. My comment on Russell’s array is that I suspect that you will hear ‘phasey’ sound as you move off axis and around the room for music with higher frequency content.
For what it is worth the Darren Kuzma’s 32 driver line array at:
http://www.partsexpress.com/projectshowcase/Kuze3201/Kuze3201.html
in the Parts Express Project Showcase demonstrates what one would have with drivers that are spaced 2.125” c-t-c. Note how Darren’s array shows significant decline of the amplitude response vs. frequency (see the unequalized and equalized plots in his report). An array with 3.5” spacing will have even lower frequency onset of amplitude response roll off.
Now let us take Russell’s no comb lining myth to the limit via using larger drivers or move the drivers even further apart in the array. I suspect that you will quickly hear even more frequency response shortcomings regardless of any equalization. It is not a design approach what I would advise one to pursue.
Hey ChrisB calling ya on this one.....
I just noticed this thread the other day and was intent to follow it along as I have a soft spot for line source speakers. I have to say Chris that your attitude could stand a serious adjustment at the service centre. To start I hardly think that Roger has you and yours in mind as a target audience for his new speaker. Sceondly while I do not know Roger personally I do know of his track record as well as some of the company that he worked for. I believe that Roger has as they say forgotten more about speaker designs than you may hope to know. Some sort of respect is due the man. You can disagree all you want but I find your sneer and geer response verging on offensive. Given that this is a diy forum and that this man is a professional with an impressive track record I should think that any of us here would welcome the chance to learn from an old hand who spent more than a little while on the corner making more than just a few bucks in the speaker game. When you can brag a track record as successful as Roger's then you might feel that you can take such an attitude but that still would not make such behaviour right. I am getting off the box now and I hope to hear a kinder discourse. Regards Moray James.
I just noticed this thread the other day and was intent to follow it along as I have a soft spot for line source speakers. I have to say Chris that your attitude could stand a serious adjustment at the service centre. To start I hardly think that Roger has you and yours in mind as a target audience for his new speaker. Sceondly while I do not know Roger personally I do know of his track record as well as some of the company that he worked for. I believe that Roger has as they say forgotten more about speaker designs than you may hope to know. Some sort of respect is due the man. You can disagree all you want but I find your sneer and geer response verging on offensive. Given that this is a diy forum and that this man is a professional with an impressive track record I should think that any of us here would welcome the chance to learn from an old hand who spent more than a little while on the corner making more than just a few bucks in the speaker game. When you can brag a track record as successful as Roger's then you might feel that you can take such an attitude but that still would not make such behaviour right. I am getting off the box now and I hope to hear a kinder discourse. Regards Moray James.
our experience
Jordan full range driver thread
I have both 4 driver and 9 driver Jordan line arrays playing here (I WON'T be doing a 32 driver version). We had previously had some discussion about the issues of full range in a line array in the linked thread. The chart shows unEQ'd versus EQ'd in our room. Whilst I can hear mild combing with a pure tone, it just isn't bothersome while listening to music. I've heard worse combing with much deeper and sharper nulls with other speakers that weren't line arrays and that speaker too had enough redeeming qualities to make the combing a non-issue. Is it perhaps the nature of the combing that determines if it offends?
Since we do have products on display here, we have a steady stream of ears passing through, and not once has anyone noticed combing effects. Most comment on the smoothness and tone of the line arrays and almost all comments are positive.
Rather than being a spoiler, I accept this aspect of full range line array design as a tradeoff against some very strong attributes, just like every other speaker system we have.
Interesting discussion.
Brian
Jordan full range driver thread
I have both 4 driver and 9 driver Jordan line arrays playing here (I WON'T be doing a 32 driver version). We had previously had some discussion about the issues of full range in a line array in the linked thread. The chart shows unEQ'd versus EQ'd in our room. Whilst I can hear mild combing with a pure tone, it just isn't bothersome while listening to music. I've heard worse combing with much deeper and sharper nulls with other speakers that weren't line arrays and that speaker too had enough redeeming qualities to make the combing a non-issue. Is it perhaps the nature of the combing that determines if it offends?
Since we do have products on display here, we have a steady stream of ears passing through, and not once has anyone noticed combing effects. Most comment on the smoothness and tone of the line arrays and almost all comments are positive.
Rather than being a spoiler, I accept this aspect of full range line array design as a tradeoff against some very strong attributes, just like every other speaker system we have.
Interesting discussion.
Brian
I don't know about these things. I really don't. Roger is no fool, I'm sure no-one here is suggesting that he is, though he clearly works in his own way. Fair enough of course. But the laws of physics don't change, as Jim points out. The Jordans might work because their arrays are pretty short -more far-field than near I wonder? For the rest, I'll wait until I see some accurate measurements.
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