More than one local guys just tried to brainwash me while facing a bunch of high-end midbass we shoulda choose those giant linear xmax stuff (actually sd*xmax) of course at the same time we can't ignore those mms, fs which we often discuss.
So I've spent several months including many without-sleep-nights just trying to look the xmax up as much as possible.
Tired, just tired.
And the result is, some of the Scan Illuminator have extra xmax which is kinda scary (18WU/8741T00 & 4741T00), just wanna know, did you guys well, have any experience with these two drivers (sub question: sq relates with xmax)?
So I've spent several months including many without-sleep-nights just trying to look the xmax up as much as possible.
Tired, just tired.
And the result is, some of the Scan Illuminator have extra xmax which is kinda scary (18WU/8741T00 & 4741T00), just wanna know, did you guys well, have any experience with these two drivers (sub question: sq relates with xmax)?
Xmax and sound quality (or rather, linearity) cannot be directly correlated. There can be many design trade-offs needed to alter a motor design to achieve higher Xmax. For instance, simply increasing the voice coil length in the overhung motor design will increase Xmax but will make Le(x) (how the coil inductance changes with excursion) vary more, therefore causing higher intermodulation distortion in the upper midrange and lower treble of a 5-8" woofer, even when operating well below xmax. Therefore if a higher xmax is not required such as in a dedicated midrange driver which does not have to deal with bass frequencies, shortening the voice coil can improve the midrange such as SB Acoustics did with their Satori midrange drivers (e.g. MR13P vs MW13P).
If the magnetic gap is longer (due to a larger or more novel magnetic design) then you can fit a longer coil and achieve higher xmax without causing excessive distortion. This is one of the many reasons why subwoofers have bigger magnets/motors.
The 'knee' in non-linear distortion that occurs as xmax is exceeded will be different for every motor design as well. Generally underhung designs tend to distort harshly as xmax is exceeded while overhung designs are more forgiving however it also depends on how the magnetic gap has been designed - arrangement and geometry of pole piece, top plate, magnet etc. For that reason you can't be sure that one woofer with 5mm xmax will distort more than another woofer with 6mm xmax when you ask 8mm excursion of both of them. For the same reason, you can't be sure that either one will be more linear than the other when you ask 3mm excursion of them either. The only way to know is to measure the distortion in a test setup.
There is also the issue of mechanical excursion of the soft parts - for these not to introduce their own non-linear distortion under high excursion the spider and surround need to be suitably redesigned (made bigger) as well and this has design trade offs as well. For instance there is not much point having a motor with 10mm xmax if the spider and surround lock up hard at 5mm.
For what it's worth the 18W/8531G (6.5mm xmax) produces lower non-linear distortion than the 18WU/8741T00 (9mm xmax) at the volume that Zaph Audio tested it Zaph|Audio
If the magnetic gap is longer (due to a larger or more novel magnetic design) then you can fit a longer coil and achieve higher xmax without causing excessive distortion. This is one of the many reasons why subwoofers have bigger magnets/motors.
The 'knee' in non-linear distortion that occurs as xmax is exceeded will be different for every motor design as well. Generally underhung designs tend to distort harshly as xmax is exceeded while overhung designs are more forgiving however it also depends on how the magnetic gap has been designed - arrangement and geometry of pole piece, top plate, magnet etc. For that reason you can't be sure that one woofer with 5mm xmax will distort more than another woofer with 6mm xmax when you ask 8mm excursion of both of them. For the same reason, you can't be sure that either one will be more linear than the other when you ask 3mm excursion of them either. The only way to know is to measure the distortion in a test setup.
There is also the issue of mechanical excursion of the soft parts - for these not to introduce their own non-linear distortion under high excursion the spider and surround need to be suitably redesigned (made bigger) as well and this has design trade offs as well. For instance there is not much point having a motor with 10mm xmax if the spider and surround lock up hard at 5mm.
For what it's worth the 18W/8531G (6.5mm xmax) produces lower non-linear distortion than the 18WU/8741T00 (9mm xmax) at the volume that Zaph Audio tested it Zaph|Audio
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If you're just looking for tons of xmax, look for stuff with XBL^2 motors. The Adire Extremis is a good example with 13mm one-way xmax: Extremis 6.8 Midwoofer by Adire Audio®
I believe ADI owns the XBL IP these days: Advanced Transducer Development
I believe ADI owns the XBL IP these days: Advanced Transducer Development
If you are trying to reproduce lots of bass then you need lots of volume displacement. How you get that displacement doesn't matter, lots of xmax or lots of surface area. People usually build to a target specification though and size their drivers as is necessary.
There are some mid/bass drive units out there with rather high xmax figures and if you are constrained by design choices such that the high xmax driver makes the most sense, then you go with it.
Given that this is mainly concerning two ways, with overall system design, I would always prefer to go the route of small sub + mid/bass driver without the high xmax. Then you can choose your mid/bass for its midrange performance rather than how it copes with bass.
There is nothing wrong with the Illumintor range and their massive xmax figures. The revelator series before them though tended to have better measured performance. If you need the xmax then you go Illuminator. If you don't then you pick something else.
There are some mid/bass drive units out there with rather high xmax figures and if you are constrained by design choices such that the high xmax driver makes the most sense, then you go with it.
Given that this is mainly concerning two ways, with overall system design, I would always prefer to go the route of small sub + mid/bass driver without the high xmax. Then you can choose your mid/bass for its midrange performance rather than how it copes with bass.
There is nothing wrong with the Illumintor range and their massive xmax figures. The revelator series before them though tended to have better measured performance. If you need the xmax then you go Illuminator. If you don't then you pick something else.
Just look at the performance in the graphs on this site: http://medleysmusings.com/ss18wu4741/
Look at the flat top on the BL curve and Kms graph. A lot of work went into designing these monsters to really do as advertised. Meaning the woofer really is capable to perform very linear over their impressive xmax figures.
Look at the flat top on the BL curve and Kms graph. A lot of work went into designing these monsters to really do as advertised. Meaning the woofer really is capable to perform very linear over their impressive xmax figures.
No, I for one, don't really need any Xmax nowhere near that figure.
The only 6,5" SS unit I wish to own is this one. The price isn't as
exorbitant as others are. Yeah, I know I'm stuck in the past times.
All of my needs boils down to a 10W/8 ohm amp and 83dB/1m/2,83V
speaker sensitivity.
The only 6,5" SS unit I wish to own is this one. The price isn't as
exorbitant as others are. Yeah, I know I'm stuck in the past times.
All of my needs boils down to a 10W/8 ohm amp and 83dB/1m/2,83V
speaker sensitivity.
Attachments
Thank you, guys. Regarding of bass, someone recently told me something about linear/non-linear distortion, a paradox. I don't know it's true or not. Here's what he said:
Well, using one 12" sub, what you get is more non-linear distortion compared with using two, but, the size of the cabinet will be unavoidably bigger if we choose two 12", and human ear is insensitive to non-linear distortion but pretty sensitive to linear distortion. The bigger the cabinet becomes, the linear distortion becomes higher. Like a zero-sum game (is it?), hard to choose a balanced option.
Well, using one 12" sub, what you get is more non-linear distortion compared with using two, but, the size of the cabinet will be unavoidably bigger if we choose two 12", and human ear is insensitive to non-linear distortion but pretty sensitive to linear distortion. The bigger the cabinet becomes, the linear distortion becomes higher. Like a zero-sum game (is it?), hard to choose a balanced option.
anji,
oops, my English teacher would have given me the look,
you know, the non approving one. I should have written
" I wish I owned". So, I don't have it. I can still recommend
a cabinet volume and baffle measures, or maybe you could
do the same playing with a simulator.
oops, my English teacher would have given me the look,
you know, the non approving one. I should have written
" I wish I owned". So, I don't have it. I can still recommend
a cabinet volume and baffle measures, or maybe you could
do the same playing with a simulator.
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btw, I have a question, I thought linear excursion (p-p) = voice coil height - height of gap (or vice versa if underhung), if so, SS 18 cm should be 12 cm....
mtoc
I'd have to have a better source than that. 🙂 I've never heard that before. 2 woofers sharing a cabinet space that is twice as big should only reduce distortion due to a reduction in excursion.
It should be the same, but less portable, as having 2 separate woofer cabinets.
However, using 2 separate subs allows you to fill in room modes when placed asymetrically, so no, even with a modest change in distortion, the null fill-in will far outweigh distortion. Of course, this should be complemented by bass traps and EQ as needed.
There's also a terrible myth that larger speakers have more distortion in the bass, which is nonsense. The larger drivers are more linear and have more powerful motors. They move air in low frequencies much more easily. 2 x 10" drivers have about the same effective surface area as a single 12" I think, so the myth of using lots of small drivers because they are faster and have less distortion than larger drivers for bass is rubbish..
I'd have to have a better source than that. 🙂 I've never heard that before. 2 woofers sharing a cabinet space that is twice as big should only reduce distortion due to a reduction in excursion.
It should be the same, but less portable, as having 2 separate woofer cabinets.
However, using 2 separate subs allows you to fill in room modes when placed asymetrically, so no, even with a modest change in distortion, the null fill-in will far outweigh distortion. Of course, this should be complemented by bass traps and EQ as needed.
There's also a terrible myth that larger speakers have more distortion in the bass, which is nonsense. The larger drivers are more linear and have more powerful motors. They move air in low frequencies much more easily. 2 x 10" drivers have about the same effective surface area as a single 12" I think, so the myth of using lots of small drivers because they are faster and have less distortion than larger drivers for bass is rubbish..
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Hey Mtoc....
By the way, I misread. I have the Revelator version of those woofers, not the Illuminators which are magnificent and $100 cheaper. Amazing full, warm bass. I'm tempted by the Illuminator, and I think Troels has at least one project with them where he goes over just how spectacular the motor is.
Still, despite the great looking magnet no one else would see, and better motor, the Illuminators are too rich for my blood. 🙂 I may very well have made the last loudspeakers I want to actually sit and listen to.
Best,
Erik
By the way, I misread. I have the Revelator version of those woofers, not the Illuminators which are magnificent and $100 cheaper. Amazing full, warm bass. I'm tempted by the Illuminator, and I think Troels has at least one project with them where he goes over just how spectacular the motor is.
Still, despite the great looking magnet no one else would see, and better motor, the Illuminators are too rich for my blood. 🙂 I may very well have made the last loudspeakers I want to actually sit and listen to.
Best,
Erik
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Better at what though?
The only thing the pretty Illuminators have over the good ol' Revs' is linear excursion.
Hi 5th,
I don't know enough about electro-magnetics, I was calling them "better" because Gravesen says the motor does everything right.
From a listening perspective, I'm already very very happy. 🙂
Best,
Erik
I don't know enough about electro-magnetics, I was calling them "better" because Gravesen says the motor does everything right.
From a listening perspective, I'm already very very happy. 🙂
Best,
Erik
What do you mean you don't know enough about it. You know
that the higher the rpm, the less it will last and finally it'll
blow itself into the oblivion. 🙂
Manufacturers play on people's most sensitive region, vanity.
Heavens forbid you don't have enough power output reserves
and spl when your friends arrive to your birthday party.
edit: Have you ever seen a Top Gear (British) episode when there were
sports cars tested on a track course, I think Ferrari, Lamborghini,
Audi R8 and alike were loaded with a very small amount of gasoline
and the goal was to measure the fuel consumption. In short IIRC,
Ferrari had 160 litres/100km, Audi 80 litres/100 km and so on...
These were driven really hard. I don't think any manufacturer would
gladly publish that kind of data.
that the higher the rpm, the less it will last and finally it'll
blow itself into the oblivion. 🙂
Manufacturers play on people's most sensitive region, vanity.
Heavens forbid you don't have enough power output reserves
and spl when your friends arrive to your birthday party.
edit: Have you ever seen a Top Gear (British) episode when there were
sports cars tested on a track course, I think Ferrari, Lamborghini,
Audi R8 and alike were loaded with a very small amount of gasoline
and the goal was to measure the fuel consumption. In short IIRC,
Ferrari had 160 litres/100km, Audi 80 litres/100 km and so on...
These were driven really hard. I don't think any manufacturer would
gladly publish that kind of data.
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