Which one is correct?
IEEE Xplore Abstract - Audibility of transient intermodulation distortion
M Petri-Larmi, M Otala, J Lammasniemi (1978) - Threshold of Audibility of Transient Intermodulation Distortion
Another link, but is down at the moment: http://www.aes.org/e-lib/browse.cfm?elib=2962
One odd thing engineers do which epidemiologists try to avoid is taking any study as being comprehensive and eternal. Studies, even when conducted with the best of controls, are subject to errors of samples, fraud, you name it.
One single study on any subject involving human perception should not be taken as eternal proof.
Best,
Erik
One single study on any subject involving human perception should not be taken as eternal proof.
Best,
Erik
And what should we care about? You fail to indicate a different idea of measurements. So one may infere that according to your statements... well.... basically all drivers are the same, as long as they push some air....
I found irritating coming into a thread a starting such off-topic discussion.
From my own subjective evaluation over the years based on
different loudspeaker units I have experimented with and
having in mind that listening level was never beyond 1W or
so, I have concluded that HD is nothing I should be concerned
about.
edit: I am awfully sorry to have irritated you, Kukulcan.
different loudspeaker units I have experimented with and
having in mind that listening level was never beyond 1W or
so, I have concluded that HD is nothing I should be concerned
about.
edit: I am awfully sorry to have irritated you, Kukulcan.
Last edited:
Lojzek is def one of the good guys on here for sure, and makes some great contributions.
What I've taken away from this and the various Accuton threads (even going so far as to translate some of the Eastern European build threads) is that the sound is very different to say scanspeak, a lot of it is down to personal taste. They have to be used within their limits to get the best out of them, and if so can reward with some if the most detailed reproduction available. Also best to go for the better motor models, cells etc (big ouch).
What I've taken away from this and the various Accuton threads (even going so far as to translate some of the Eastern European build threads) is that the sound is very different to say scanspeak, a lot of it is down to personal taste. They have to be used within their limits to get the best out of them, and if so can reward with some if the most detailed reproduction available. Also best to go for the better motor models, cells etc (big ouch).
I certainly never said that all of Accuton's drivers are lacklustre simply that (most) of the ferrite ones, that I've seen measurements of (this is rather easy as Accuton show distortion plots themselves) are poor. Ie the kind of distortion performance you'd find in a $30 driver.
This I find unacceptable. Accuton drivers cost serious amounts of money, yeah the underhung neo drivers are nice, but if I'm paying hundreds of dollars for a driver I want its motor to be designed to very high standards.
My own experience has taught me that distortion is audible, certainly if you take a driver whose motor generates third harmonics at around -40dB and you then compare it to one whose motor generates the third at around -60dB...
The main issue here is that Geddes' says not to bother with loudspeaker distortion as a metric one needs to use when trying to design loudspeakers for performance. The trouble with this statement is that he only uses quality drivers, for which that statement holds true. It's like saying I don't worry about distortion in loudspeakers because I only use SEAS Excel and ScanSpeak Revelator/Illuminator drivers. Well no duh, they all have excellent motors and perform to very high standards.
Where one needs to be concerned with distortion is if the overall quality of the drive unit is sub par to begin with. Sadly there are lots of drivers out there that do fall into this category.
Geddes uses high sensitivity, large SD drivers, that when placed into a home environment could never be pushed into a situation that would cause gross distortion (they are also expensive). Lots of us aren't playing that game though, lots of people like/have to build on a budget and lots of people have to build small speakers to fit in with what their partners find acceptable. When you're plumbing the depths of the budget market and are inherently going to be pushing your small speaker up to its limits, then you need to weed out the good from the bad.
This I find unacceptable. Accuton drivers cost serious amounts of money, yeah the underhung neo drivers are nice, but if I'm paying hundreds of dollars for a driver I want its motor to be designed to very high standards.
My own experience has taught me that distortion is audible, certainly if you take a driver whose motor generates third harmonics at around -40dB and you then compare it to one whose motor generates the third at around -60dB...
The main issue here is that Geddes' says not to bother with loudspeaker distortion as a metric one needs to use when trying to design loudspeakers for performance. The trouble with this statement is that he only uses quality drivers, for which that statement holds true. It's like saying I don't worry about distortion in loudspeakers because I only use SEAS Excel and ScanSpeak Revelator/Illuminator drivers. Well no duh, they all have excellent motors and perform to very high standards.
Where one needs to be concerned with distortion is if the overall quality of the drive unit is sub par to begin with. Sadly there are lots of drivers out there that do fall into this category.
Geddes uses high sensitivity, large SD drivers, that when placed into a home environment could never be pushed into a situation that would cause gross distortion (they are also expensive). Lots of us aren't playing that game though, lots of people like/have to build on a budget and lots of people have to build small speakers to fit in with what their partners find acceptable. When you're plumbing the depths of the budget market and are inherently going to be pushing your small speaker up to its limits, then you need to weed out the good from the bad.
Thank you to you all for the last contribution, especially the interesting insights from 5th element.
I'm sorry for having been a bit rude about HD stuff, I just wanted to prevent a long off topic...
Now some updates.....
No, the central channel with the W18 is not ready yet, fortunately my limited budget pushed me to experiment with what I have, rather than buying and building new stuff, and it turns out to be a great luck...
I tried the Accutons in an open baffle configuration...
Let me start from the beginning, as I said before the two C158 were temporarily mounted in the cabinets of a pair of Yamaha S55, these cabinets are front reflex but I sealed them. I stuffed with tick needle felt and polyester fleece; as much as I could, wave-like but not pressed.
I still had the possibility to compare by real-time switching my new speaker with another S55 used as CC.
I already commented how better they were, especially about the clarity of the midrange.
A couple of days ago, listening to a harp, I had the impression of some "boxiness". It was not the typical whooom of cheap speakers, it was rather some resonance convolving with what is being played an instant later and creating a (very small) impression of reverberation, especially in the low midrange. Further investigation and comparison with the original S55 strenghtned my impression (even though I must say that the midrange of the original S55 is really poor and silly compared to the Accu).
so I thought, let's check which is the real sound of these mid-woofer. I removed the boxes leaving the drivers mounted on the original baffle.
I was right, there was reverberation, and the sound was just a bit harsh compared to now, in open-baffle mode. Oddly, sealing and stuffing the original S55 with their paper cones, does not produce edginess at all, which makes me think that cone material plays a role much more complicated than what is generally believed...
CeramicMan, who used to write here, is very expert about the Accutons and he precisely described what I heard in a post that, the first time I read it, sounded to me cryptic... below it's a "must read" for everyone interested in the Accutons and maybe in any hard cone driver:
http://www.diyaudio.com/forums/multi-way/41256-accuton-tweeters-mid-bass-match.html#post478055
"I think that good box design is very difficult with a ceramic midwoofer. Speakers with soft cones are flexible at midrange frequencies which allows the back-wave to quickly escape and mix with the sound you're supposed to hear. Because the cone is so lossy, the sounds inside the box don't have time to become resonant and the result is a mild boxy quality that's not too bad. The C94 (with its stiff cone and very high electrical stiffness: Qes=0.21) makes the box much less lossy, and keeps the back-wave inside the box for a much longer time. Unfortunately, this also means that the sound that does escape is much more resonant. Even though the "box" sound is at a much reduced level, its quality is insanely boxy, it's: boxiness^boxiness. Stuffing material such as polyester wool only does a fraction of the absorption that's needed. It can be a bit fatiguing, and gives the speakers a contradictory nature. It also gives the word "analytical" a bad name."
The most weird thing now is that I have even better bass!!! Fullier and with more impact. Ok, I set a target curve even more rolled-off, because it's pointless pushing hard a 6,25" driver on such a small baffle (25x37 cm).
Below the frequency response after EQ and room correction:
https://dl.dropboxusercontent.com/u/12111462/openbaffle.PNG
Very satisfying! I can't even imagine how better it could be with a very good tweeter. On the other hand bass may still improve a lot in terms of low-extension and less directionality due to strong lobing (remember? much Eq and small baffle..)
I think I will focus on building a nice and wider baffle, but I have to study a little bit... I'm intriguied by a U shape but curved (let's say like a Hyperbole) in order to increase the length (on the width dimension) of the baffle. But it's not easy to build... maybe many hyperboles should be cut, stacked and glued together. Space between the rear wall is also an issue..
I want to point out that I'm not a fan of the dipole itself, but now it's pretty clear to me that a dipole is at least a second- best, where the first-best is building an expensive and very big state-of-the-art cabinet able to effective deal with the backwave, which appears to produce very nasty effects on these thin ceramic cones.
Linkwitz has successfully used many seas excel driver in open-baffle projects, so I could really start with the W18 plus maybe the seas DXT tweeter. DXT tweeter, with its wide dispersion is a perfect candidate for a central channel that guarantees good voices also off-axes. Furthermore I don't think that a CC needs to play extremely low bass, it just has to gergeously play midbass and midrange, in such case a dipole config is not not problematic with regards to bass.
I'm sorry for having been a bit rude about HD stuff, I just wanted to prevent a long off topic...
Now some updates.....
No, the central channel with the W18 is not ready yet, fortunately my limited budget pushed me to experiment with what I have, rather than buying and building new stuff, and it turns out to be a great luck...
I tried the Accutons in an open baffle configuration...
Let me start from the beginning, as I said before the two C158 were temporarily mounted in the cabinets of a pair of Yamaha S55, these cabinets are front reflex but I sealed them. I stuffed with tick needle felt and polyester fleece; as much as I could, wave-like but not pressed.
I still had the possibility to compare by real-time switching my new speaker with another S55 used as CC.
I already commented how better they were, especially about the clarity of the midrange.
A couple of days ago, listening to a harp, I had the impression of some "boxiness". It was not the typical whooom of cheap speakers, it was rather some resonance convolving with what is being played an instant later and creating a (very small) impression of reverberation, especially in the low midrange. Further investigation and comparison with the original S55 strenghtned my impression (even though I must say that the midrange of the original S55 is really poor and silly compared to the Accu).
so I thought, let's check which is the real sound of these mid-woofer. I removed the boxes leaving the drivers mounted on the original baffle.
I was right, there was reverberation, and the sound was just a bit harsh compared to now, in open-baffle mode. Oddly, sealing and stuffing the original S55 with their paper cones, does not produce edginess at all, which makes me think that cone material plays a role much more complicated than what is generally believed...
CeramicMan, who used to write here, is very expert about the Accutons and he precisely described what I heard in a post that, the first time I read it, sounded to me cryptic... below it's a "must read" for everyone interested in the Accutons and maybe in any hard cone driver:
http://www.diyaudio.com/forums/multi-way/41256-accuton-tweeters-mid-bass-match.html#post478055
"I think that good box design is very difficult with a ceramic midwoofer. Speakers with soft cones are flexible at midrange frequencies which allows the back-wave to quickly escape and mix with the sound you're supposed to hear. Because the cone is so lossy, the sounds inside the box don't have time to become resonant and the result is a mild boxy quality that's not too bad. The C94 (with its stiff cone and very high electrical stiffness: Qes=0.21) makes the box much less lossy, and keeps the back-wave inside the box for a much longer time. Unfortunately, this also means that the sound that does escape is much more resonant. Even though the "box" sound is at a much reduced level, its quality is insanely boxy, it's: boxiness^boxiness. Stuffing material such as polyester wool only does a fraction of the absorption that's needed. It can be a bit fatiguing, and gives the speakers a contradictory nature. It also gives the word "analytical" a bad name."
The most weird thing now is that I have even better bass!!! Fullier and with more impact. Ok, I set a target curve even more rolled-off, because it's pointless pushing hard a 6,25" driver on such a small baffle (25x37 cm).
Below the frequency response after EQ and room correction:
https://dl.dropboxusercontent.com/u/12111462/openbaffle.PNG
Very satisfying! I can't even imagine how better it could be with a very good tweeter. On the other hand bass may still improve a lot in terms of low-extension and less directionality due to strong lobing (remember? much Eq and small baffle..)
I think I will focus on building a nice and wider baffle, but I have to study a little bit... I'm intriguied by a U shape but curved (let's say like a Hyperbole) in order to increase the length (on the width dimension) of the baffle. But it's not easy to build... maybe many hyperboles should be cut, stacked and glued together. Space between the rear wall is also an issue..
I want to point out that I'm not a fan of the dipole itself, but now it's pretty clear to me that a dipole is at least a second- best, where the first-best is building an expensive and very big state-of-the-art cabinet able to effective deal with the backwave, which appears to produce very nasty effects on these thin ceramic cones.
Linkwitz has successfully used many seas excel driver in open-baffle projects, so I could really start with the W18 plus maybe the seas DXT tweeter. DXT tweeter, with its wide dispersion is a perfect candidate for a central channel that guarantees good voices also off-axes. Furthermore I don't think that a CC needs to play extremely low bass, it just has to gergeously play midbass and midrange, in such case a dipole config is not not problematic with regards to bass.
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