Mark,
As 5th Element points out Xmax being less than Xmech problems aren't typically encountered.
In fact, your speakers are so far the first ones I have heard of with this problem in the 40 odd years spent doing enclosure design, listening to a wide variety of speakers and reading thousands of specification sheets.
That said, I am very familiar with stress cracks in aluminum diaphragms.
Rather than try to come up with a new parameter name for the stress cracks your cones are subject to at around half of Xmax, and some smaller fraction of the Xmech figure as normally defined, you could simply include a statement like this below the specifications (which should be included with the speaker):
“Caution: Although the Alpair 10 Xmax specification of 8.5 mm is accurate, and insures low distortion on occasional peaks, the cone may develop stress cracks if allowed to operate in this range continuously.
We recommend a maximum of 4 mm one way excursion, 8 mm (5/16 inch) peak to peak for long term use.”
That statement would satisfy those that actually bother reading the specification sheet, and clarify the unusual nature of the driver's mechanical limitations.
Art Welter
Hi Art,
Did similar to your suggested statement a few months back. Floated it on the forum, got panned for being un-measurable (impractical) by numerous Diyers. That's when me and Matsubara san started re-developing rear suspensions as a possible technical solution/alternative (putting the brakes on near X max).
Thx
Mark.
Strange to me that DIYers find something like what Art is saying impractical. Xmax is a commonly used figure. When I design a can I use the ts params and check power input with xmax. Simple enough. Now knowing what I know, for your drivers I'll do the same, but with only 4mm. No one is saying use a pair of calipers on an active woofer. That's just silly. The users who don't understand this are probably not designing the cab.
Putting the brakes on before the driver breaks is a good idea ;^).
I find it laughable that people think high tech accelerometers or laser devices are needed to measure excursion.
I have explained in dozens of posts that persistence of vision actually makes it quite easy to measure cone excursion, even easier if a paint or ink dot is put on the cone.
Anybody not blind can easily see the difference between 8 mm and 17 mm excursion on a 100 mm driver.
Anybody that dismisses measuring excursion as being un-measurable (impractical) has not attempted it, you can dismiss their dismissal.
You could print a little ruler directly on the spec sheet included with the driver with a peak to peak "safe zone" of up to 8mm in blue, and a red "danger zone", and even a black Xmech black zone.
Your PDF says:
"If you see the cone of the speakers making large movements, immediately turn the volume down."
If I had not been reading this thread, I would have assumed "large movements" to be movements in excess of Xmax.
You need to be far more specific in your specifications or reasonable, educated purchasers of your product (who have not read your warnings here) will continue to break them, even if you do manage to put the brakes on the suspension.
Art
I was not recommending that anyone actually does that. I was making a point that you could easily detail a specific regime for breaking in your drivers that wouldn't be ambiguous, in the way that 'play x type of music at low levels for the first 100 hours' is.
You could go so far as providing a file that can be used for the first break in period of 24 hours, then another file for the 2nd etc. If you include a 50hz test tone along with these then you can say, play the 50hz test tone and make sure the voltage across the drivers terminals when the driver is in free air is = 0.5Vrms. Then you know and they know that they are going to be playing the break in file at the correct volume. And why 50hz? Because most cheap crappy multimeters should be able to measure AC reasonably accurately at 50hz.
Quite frankly I'm surprised that you seem to think that what I recommended would damage your drivers. The voltage figures were picked directly after simulating with one of your drivers in what would be close to a free air environment and were always quite a bit below Xmax.
If you're implying that your drivers are that fragile then I think it absolutely necessary that you provide files and details on how exactly how to break them in.
Simply playing a 100hz test tone @ 1Vrms = less then 1mm of excursion peak to peak and should not damage the driver. The 40hz test tone @ 1Vrms would give ~1.7mm peak to peak excursion and the final one - 40hz @ 2Vrms would give ~3.5mm peak to peak excursion. Are you trying to tell me that your driver would be harmed by doing such a thing? If so then I think you need to redesign them.
I think Art hit the nail on the head when he said
No one has any problems with the way you're doing things, it's just that your comments regarding excursion in the datasheets or on line are always extremely vague and open to many different forms of interpretation.
Saying that you've tried providing more concrete figures and that it created more problems then it solved is plain nonsense. If people are asking you because they don't know what it means then I do not think you are in any way out of place by simply replying, "if you don't know what it means, then please go learn and find out".
It is not your job as a transducer designer to teach people loudspeaker basics. Just because you're easily contactable doesn't change this either.
I suppose you could add in at the bottom of every spec sheet, if you don't know how to calculate the excursion demands/requirements of a driver vs drive level when in a suitable box, then go and download for free winISD Pro and educate yourself.
Oh and as to the definition of Xmech. Whether or not you agree with what's written on wikipedia is besides the point. Of the manufactures that I've seen describing the parameter it is always implied that this is the maximum travel you can take the driver through before damage will occur, it is often called different things. Interestingly SEAS, Scanspeak, Beyma, 18Sound, Precision Devices, Eminence, etc all list a parameter that would be described as Xmech. Eminence even go so far as to explain what this means (what they call Xlim) in their section on Understanding Loudspeaker Data | Eminence Speaker. Now you're not going to tell me that all of them are wrong are you?
Bumped backplate, wider surround and a progressive spider would go a long way to get the Xdestruction more in line with the Xmax. But that would drive up the price, and I don't know what the market will bear. Plus, a wider surround might have an unwanted weight panelty, etc. And even if you did that, in the end, something else, like the VC, would give the ghost when people don't use drivers within their enveloppe. No loudspeaker manufacturer can protect himself from that.
Listing Xmax figures is tricky, I fully agree with Mark on that. Also, because who on this forum has a strobe setup to reliably measure the X on their driver? Providing a specification that no-one can put to any use is pointless.
Having followed a number of threads on applications for Mark's drivers, my guestimate is that most problems are not caused by the drivers, but by the enclosures. Folded horns etc. provide in their working region good acoustic coupling between the driver and the air, restraining cone movement, but below their cut off frequency, the driver becomes 'free floating'. Only two options here: 1) limit power, or 2) filter out the low frequencies that the loudspeaker cannot produce anyways.
Amplifiers used to have a 'rumble' filter that could be used to that end, but no longer so.
Listing Xmax figures is tricky, I fully agree with Mark on that. Also, because who on this forum has a strobe setup to reliably measure the X on their driver? Providing a specification that no-one can put to any use is pointless.
Having followed a number of threads on applications for Mark's drivers, my guestimate is that most problems are not caused by the drivers, but by the enclosures. Folded horns etc. provide in their working region good acoustic coupling between the driver and the air, restraining cone movement, but below their cut off frequency, the driver becomes 'free floating'. Only two options here: 1) limit power, or 2) filter out the low frequencies that the loudspeaker cannot produce anyways.
Amplifiers used to have a 'rumble' filter that could be used to that end, but no longer so.
1 - Quite frankly I'm surprised that you seem to think that what I recommended would damage your drivers. The voltage figures were picked directly after simulating with one of your drivers in what would be close to a free air environment and were always quite a bit below Xmax. If you're implying that your drivers are that fragile then I think it absolutely necessary that you provide files and details on how exactly how to break them in.
2 - Saying that you've tried providing more concrete figures and that it created more problems then it solved is plain nonsense. If people are asking you because they don't know what it means then I do not think you are in any way out of place by simply replying, "if you don't know what it means, then please go learn and find out".
3 - It is not your job as a transducer designer to teach people loudspeaker basics. Just because you're easily contactable doesn't change this either.
4 - Oh and as to the definition of Xmech. Whether or not you agree with what's written on wikipedia is besides the point. Of the manufactures that I've seen describing the parameter it is always implied that this is the maximum travel you can take the driver through before damage will occur, it is often called different things. Interestingly SEAS, Scanspeak, Beyma, 18Sound, Precision Devices, Eminence, etc all list a parameter that would be described as Xmech. Eminence even go so far as to explain what this means (what they call Xlim) in their section on Understanding Loudspeaker Data | Eminence Speaker. Now you're not going to tell me that all of them are wrong are you?
Hi 5th,
I'm surprised by some of these comments, wide of the mark. Dealing with your main comments in numbered order.
1 - I think you be have the makings of driver designer, but you'll need to focus on component manufacture and operation. Its taken me 12 years+ so far (ouch). The primary objective when running-in a driver is to use variable load to the prevent a fixed or semi-elastic mechanical memory formation within the suspensions. This is particularly important for most synthetic rear suspensions, cotton suspensions are slightly less critical. Partly why many makers use Klippel or similar variable load test signal generating equipment rather than solely relying on fixed input tests. Apologies for not explaining this in my last post, although I have covered this is other posts over the years.
Regarding failure rates generally, the dealers tell me I'm in the lower-middle of the basket of domestic DIY driver makers, that is a lower than average return on failed drivers. Thats more or less where I'd expect Markaudio drivers to be. The last two years, our net return rate is 2.1% of sale, that ain't bad for low load drivers as this includes things like drivers damaged in transit etc.
2 - Its not me you need to convince. Take a look at some of the previous posts on this thread. Not everyone thinks the way you and Art do. Quoting you "if you don't know what it means, then please go learn and find out". I fear this is a bit too brutal for many Diyers and customers.
3 - Now you're telling me job? Diyer's ask me to comment (as per thread starter), I do my best to contribute to the debate. But I'll decide what my job's about thanks all the same!
4 - Wiki, I'm a bit surprised their researcher didn't qualify their X-Mech reference. Its not representative of the bulk of the quoted driver specs. Quoting Eminence is a mis-leading reference. Pro Audio is possibly the only part of driver making industry that some might quote a mechanical limitation specifically for the safe operation of drivers. As far as I can see, even in that part of the industry, Eminence is primarily the exception, rather than the rule. I (and some other members) recognise the operational distinction. You choose to differ on this issue.
This is the "Full Range" forum. Audax, Dayton, Fostex, Eton, Fertin, Feasterex, Fountek, Hi-Vi, Morel, Peerles, Tangbang, Wavecor and more, are the likely typical makers that Diyers on this forum have familiarity. These makers don't quote the figs you want or offer direct/specific advice relating to X-Mech.
Most would agree that Fostex has been the predominant maker in Full Range for the 1/2 century. I couldn't find any mention of X-Mech. But I did find this reference on their international site, which appears to be the nearest to the issue:
INPUT POWER
Indication of input power may be for both 'maximum allowable input power' and 'rated input power', or for either one of them. The fact that they are given different definitions makes it necessary to confirm that such figures are adequate for your intended application.
(1) MAXIMUM ALLOWABLE INPUT POWER
This term defines the maximum input power which can be momentarily applied to the driver. However, note must be taken that such power is a measurement of certain individual frequencies, and thus, not allowed for every frequency point. To be safe, input power defined using the term 'Music' should be considered, in that it indicates peak input power encountered during reproduction of a general music source. In no sense do input values mean that no sound will be produced unless such power is input, nor may drivers be damaged unless the output power of an amplifier is lower than the input value. Under ordinary listening conditions in homes, the possibility of excessive power being input will be rare even with an amplifier having output capability of up to several hundred watts, except under extraordinary conditions. Apart from occasions for PA purposes or where drivers are driven for experimental purposes, input values may be regarded as certain guidelines for enjoyable reproduction of Hi-Fi sound in homes.
(2) RATED INPUT POWER
This value represents the upper limit of the power which may be continuously input into drivers. It must be noted, however, that, as with the maximum allowable input power, such values are effective only for certain selected frequencies, not for the entire audio spectrum. Nor, does it mean that such value can be input if the frequency of interest is constant, as for some special purposes such as measurement or experiment purposes. Continuous input of a single frequency should be interpreted as if the driver load is substantial and very burdensome.
Please feel free to lobby these makers, and the bulk of the rest of the industry to do it your way. I see no meeting of minds on this issue. You're using me as a soft target when the issue is much broader than 1 small maker.
Mark.
Last edited:
From what I understand Marks drivers are being damaged by the edges of the cones deforming or tearing, as a direct result, presumably, of being 'pulled' in the wrong direction too strongly by the surround. I am not a transducer designer so I cannot say what all of the issues would be of increasing the surround size. I suppose one solution might be to thicken the very outside edge of the cone to reinforce it so it resists being bent/torn, but then again that might fly in the face of what people want these drivers to do, especially as people are asking for more sensitivity and that would act to lower it.
Well none of us actually measure the excursion of our drivers when in use, we simulate how the driver will respond given the environment it is placed in and then calculate the maximum safe voltage that can be applied for a given frequency so that the excursion limitations of the driver aren't exceeded. With modern digital media, with 0dB representing the maximum signal level, it is quite easy to determine the maximum position you can set on the volume control so as not to exceed the drivers maximum excursion at any given frequency. Obviously a driver such as these should be high passed so as not to try and reproduce frequencies they cannot, as that would otherwise result in a very limited maximum volume if the driver were to try and reproduce something around 20hz.
It's funny you should say that because briefly I've been trying out different enclosures for the CHR70 and from my perspective the only 'normal' type of cabinet that you should use with one is sealed. They don't appear to fit that well into ported enclosures and they unload at pretty high frequencies too resulting in wasted excursion on frequencies the driver cannot produce - A sure fire way to damage the driver if you want to drive it with pop/rnb style stuff.
One configuration they appear to work very well in is a simple sealed box of 10 litres with an electrical high pass @ 100hz with a filter Q of 0.7. Like this they practically fall into an acoustic LWR 4th order roll off at 80hz, perfect for partnering with a small sub.
It also bears mentioning that even in that configuration, at certain frequencies the driver will most like experience damaging levels of excursion perhaps (7.5mm peak to peak @ 80hz, is that safe?) when driven with the maximum rated input power of 20 watts. Given all of that and considering most people probably don't high pass them, I am not surprised that people end up damaging them.
I am not using you as a soft target Mark, at least not intentionally.
If I have something wrong then I really don't mind being corrected, I am after all here to learn as much as the next guy is.
Presumably if 'memory' were to form in the suspensions then the driver would sit off centre after the memory had formed. A sine wave should send the suspension through one direction then repeat the process in completely the opposite direction, so you'd figure any memory created from the out stroke would be removed by the in stroke, I guess you're saying this is not the case or am I missing the point? Regardless of that though if sine waves aren't a good idea for running in your drivers, I did say that you could provide your own sound files for the effective running in of your drivers and only use a brief sine wave to set the level at which to run them in at.
Why is that? I see DIY primarily as a learning experience with benefits. This is the part where doing it yourself comes in, you don't do it yourself if you're incompetent or ignorant. You might start out with the idea whilst being ignorant but because you want to do it yourself you teach yourself the required skills to accomplish the job successfully. In this case learning how to simulate drivers in boxes in free computer programs. From what I've read about your drivers, learning a little about excursion and how to predict/design around it would seem critical to maximising the performance of their designs.
I'm saying that if you provide the specs and the DIYers don't know what to do with them, then it isn't your job to teach it to them. Removing a spec or an xmax recommendation from a datasheet, because people ask because they don't know what to do with them, doesn't solve the problem, it just ignores it. And then like Art said, if you're knowledgeable and see the datasheets you see an xmax figure and you then design a loudspeaker system around that figure and end up damaging your driver.
I'd say they are in fine company along with the other pro audio manufactures I mentioned, unless that wasn't your point.
And this is where you've hit the nail on the head. An industry or situation or set of circumstances where it is necessary to define mechanical limitations so as to prevent damage where it is important. The pro arena is different in this regard vs the majority of typical consumer audio drive units manufactured. However your drivers aren't typical and this is the point. Of the manufactures you mentioned...
I bet that almost all of them can be used at their rated xmax without damage occurring. Your drivers however cannot. This is where your drivers and the pro world meet. In the pro world it is necessary for the loudspeaker designers to know exactly where the limitations of the drive units lie so nothing becomes damaged. The same is true for your drivers, as the xmax parameter quoted in your datasheets is not representative of a realistic safe repeatable excursion, how are people supposed to know how hard they can drive them? It is necessary for you to define an Xmech type parameter so people stand the best chance of keeping their drivers undamaged.
If the majority of DIYers don't know what to do with an Xmech figure this isn't a good reason to omit it from a datasheet. And the fact that lots of other loudspeaker manufactures don't quote the figure isn't any defence of your position either. They provide an Xmax figure, a useful xmax figure and you know that you aren't going to damage their drivers if you use them within the rated xmax.
You however don't provide any solid figure for safe excursion, xmax is clearly isn't it, but what is?
Yes, but you wont break any of their drivers running them at their rated xmax.
If I have something wrong then I really don't mind being corrected, I am after all here to learn as much as the next guy is.
Presumably if 'memory' were to form in the suspensions then the driver would sit off centre after the memory had formed. A sine wave should send the suspension through one direction then repeat the process in completely the opposite direction, so you'd figure any memory created from the out stroke would be removed by the in stroke, I guess you're saying this is not the case or am I missing the point? Regardless of that though if sine waves aren't a good idea for running in your drivers, I did say that you could provide your own sound files for the effective running in of your drivers and only use a brief sine wave to set the level at which to run them in at.
Why is that? I see DIY primarily as a learning experience with benefits. This is the part where doing it yourself comes in, you don't do it yourself if you're incompetent or ignorant. You might start out with the idea whilst being ignorant but because you want to do it yourself you teach yourself the required skills to accomplish the job successfully. In this case learning how to simulate drivers in boxes in free computer programs. From what I've read about your drivers, learning a little about excursion and how to predict/design around it would seem critical to maximising the performance of their designs.
I'm saying that if you provide the specs and the DIYers don't know what to do with them, then it isn't your job to teach it to them. Removing a spec or an xmax recommendation from a datasheet, because people ask because they don't know what to do with them, doesn't solve the problem, it just ignores it. And then like Art said, if you're knowledgeable and see the datasheets you see an xmax figure and you then design a loudspeaker system around that figure and end up damaging your driver.
I'd say they are in fine company along with the other pro audio manufactures I mentioned, unless that wasn't your point.
And this is where you've hit the nail on the head. An industry or situation or set of circumstances where it is necessary to define mechanical limitations so as to prevent damage where it is important. The pro arena is different in this regard vs the majority of typical consumer audio drive units manufactured. However your drivers aren't typical and this is the point. Of the manufactures you mentioned...
I bet that almost all of them can be used at their rated xmax without damage occurring. Your drivers however cannot. This is where your drivers and the pro world meet. In the pro world it is necessary for the loudspeaker designers to know exactly where the limitations of the drive units lie so nothing becomes damaged. The same is true for your drivers, as the xmax parameter quoted in your datasheets is not representative of a realistic safe repeatable excursion, how are people supposed to know how hard they can drive them? It is necessary for you to define an Xmech type parameter so people stand the best chance of keeping their drivers undamaged.
If the majority of DIYers don't know what to do with an Xmech figure this isn't a good reason to omit it from a datasheet. And the fact that lots of other loudspeaker manufactures don't quote the figure isn't any defence of your position either. They provide an Xmax figure, a useful xmax figure and you know that you aren't going to damage their drivers if you use them within the rated xmax.
You however don't provide any solid figure for safe excursion, xmax is clearly isn't it, but what is?
Yes, but you wont break any of their drivers running them at their rated xmax.
Very interesting,
Most drivers have the weak point in the suspension--not the cone when dealing with Xmax. Other drivers have issues dealing with the voice coil--MA drivers weak point is the CONE which makes sense to me.
Why? Because Aluminum breaks--the nature of the beast. It is lighter by volume than titanium so for the lightest things possible--aluminum is king. Sure, it has the durability of a potato chip but you know that going in. Look at racing bicycle frames--the steel or titanium ones have a lifetime warranty...aluminum is 3 to 7 years. Aluminum bicycle rims last 10 to 15 years--and crack but such is life. Want to really break an aluminum rim? Anodize it, scratch it up with the rim brakes (creates stress risers) and buy a new rim after 5 years or so.
Look at springs--steel or titanium since they can flex within specs for years--decades and as long as you don't exceed the stress specs--very durable. There is a reason they don't make aluminum springs--they will break since the material does not like to be flexed--it fails and it is not a question of if but of when.
So the MA cones get stress fractures running at Xmax--not hard to understand why--the cones are the lightest possible to get the frequency response and are made of aluminum. The generous Xmax allows them to do something FRs traditionally can't do--real bass response but you have to pay to play--aluminum breaks.
JBL figured that out in the 1970's--their compression drivers all failed after a period of time from stress fractures. They switched to titanium since they have the flex durability over long periods. True, the marketing people spewed the "titanium sound" but it was to eliminate aluminum stress failures.
I've beat the !@#$! out of my paper coned 15" Cerwin Vega woofers over the years--they now are my HT subwoofer at the age of 21 years old. No aluminum cones, no foam surrounds--paper and fabric.
Maybe Mark can make a "bass head" version of the Alpair with kevlar added to paper cones? It will change the signature sound of the Alpairs but would be marketed for the "Xmax" compressed music folks as an alternative. The aluminum version could be the "audiophile" version with the special paper cone for the folks that need Xmax with higher powered SS amplifiers?
Most drivers have the weak point in the suspension--not the cone when dealing with Xmax. Other drivers have issues dealing with the voice coil--MA drivers weak point is the CONE which makes sense to me.
Why? Because Aluminum breaks--the nature of the beast. It is lighter by volume than titanium so for the lightest things possible--aluminum is king. Sure, it has the durability of a potato chip but you know that going in. Look at racing bicycle frames--the steel or titanium ones have a lifetime warranty...aluminum is 3 to 7 years. Aluminum bicycle rims last 10 to 15 years--and crack but such is life. Want to really break an aluminum rim? Anodize it, scratch it up with the rim brakes (creates stress risers) and buy a new rim after 5 years or so.
Look at springs--steel or titanium since they can flex within specs for years--decades and as long as you don't exceed the stress specs--very durable. There is a reason they don't make aluminum springs--they will break since the material does not like to be flexed--it fails and it is not a question of if but of when.
So the MA cones get stress fractures running at Xmax--not hard to understand why--the cones are the lightest possible to get the frequency response and are made of aluminum. The generous Xmax allows them to do something FRs traditionally can't do--real bass response but you have to pay to play--aluminum breaks.
JBL figured that out in the 1970's--their compression drivers all failed after a period of time from stress fractures. They switched to titanium since they have the flex durability over long periods. True, the marketing people spewed the "titanium sound" but it was to eliminate aluminum stress failures.
I've beat the !@#$! out of my paper coned 15" Cerwin Vega woofers over the years--they now are my HT subwoofer at the age of 21 years old.
No aluminum cones, no foam surrounds--paper and fabric. Maybe Mark can make a "bass head" version of the Alpair with kevlar added to paper cones? It will change the signature sound of the Alpairs but would be marketed for the "Xmax" compressed music folks as an alternative. The aluminum version could be the "audiophile" version with the special paper cone for the folks that need Xmax with higher powered SS amplifiers?
Hi 5th, Guys,
5th, appreciate you first comment in you last post; And your contributions. They are interesting but you've made many assertions that are incorrect. You need more knowledge on driver design and construction to avoid some of traps. Your thinking is far too geared towards constant inputs when drivers load are primarily non-linear for bulk of musical reproduction.
You've made allot of inferences, some of which are below the belt, without foundation. This one in particular, quoted from you last post: "I bet that almost all of them can be used at their rated xmax without damage occurring." Its potentially mis-leading to other members. I hope other members will note my item 2 reply below.
But I like it when guys try. I'm on record for actively encouraging Diyers to do what I've done; Become driver designers and makers. We collectively shouldn't leave it all to the big maker boys.
--------
Guys,
I'll have to make this my last post, cos this thread's eaten so much time that I need for all the other jobs currently on my "to do" list. So all I can do summarise the current situation as best I can:
1 - I appreciate that my designs don't direct fit into a typical Full-Range configurations i.e they have a linear long throw coupled with low mass, requiring more operational care than some other Full-Rangers. I've never made any secret of this, I've done allot to highlight this situation.
2 - This bit's important:
For most makes of Full-Range drivers, they won't sustain operational integrity when run at X-max for long peroids. For the 2 years, I've been working guys (Matsubara san, Father designer of the FE series), Taniguchi san, past lead designer for JBL, Sony et.al and Kitagowa San, chief quality control Manager Foster Corp. Together they've got a 100+ years of driver design/build experience between them. We collectively know that that the bulk of light load wide-band-Full-Range drivers won't operate safely if driven very close to, or at their quoted X-max on constant/heavier regular loads. You can decide if me and my colleagues have the greater driver knowledge and operational experience, or member 5th, on this particular issue.
-------------------
Trying to use X-mech as some sort of standard is a long way off. The bulk of the industry doesn't apply this type of measure for the purposes of safe limit operation. There are too many operational variables influencing the driver to make reliable data.
For the bulk of applications (despite 5th's continuous assertions), Markaudio drivers work fine. I don't have ten's or hundred's of guys beating on my door with broken drivers in their hands. Please see my previous recent posts. From BR's, vented, MLTL's, Damped Air Coupled to Horns, Sealed etc, etc., there's lots of Markaudio drivers in these box types doing their work.
I do accept that better illustrating the operational description of X is proving challenging. I've stuck with this thread in the hope that some progress and agreement would be made, or a bright new idea will emerge. This issue has been knocking around in the forum for the past year.
Cheers
Mark.
5th, appreciate you first comment in you last post; And your contributions. They are interesting but you've made many assertions that are incorrect. You need more knowledge on driver design and construction to avoid some of traps. Your thinking is far too geared towards constant inputs when drivers load are primarily non-linear for bulk of musical reproduction.
You've made allot of inferences, some of which are below the belt, without foundation. This one in particular, quoted from you last post: "I bet that almost all of them can be used at their rated xmax without damage occurring." Its potentially mis-leading to other members. I hope other members will note my item 2 reply below.
But I like it when guys try. I'm on record for actively encouraging Diyers to do what I've done; Become driver designers and makers. We collectively shouldn't leave it all to the big maker boys.
--------
Guys,
I'll have to make this my last post, cos this thread's eaten so much time that I need for all the other jobs currently on my "to do" list. So all I can do summarise the current situation as best I can:
1 - I appreciate that my designs don't direct fit into a typical Full-Range configurations i.e they have a linear long throw coupled with low mass, requiring more operational care than some other Full-Rangers. I've never made any secret of this, I've done allot to highlight this situation.
2 - This bit's important:
For most makes of Full-Range drivers, they won't sustain operational integrity when run at X-max for long peroids. For the 2 years, I've been working guys (Matsubara san, Father designer of the FE series), Taniguchi san, past lead designer for JBL, Sony et.al and Kitagowa San, chief quality control Manager Foster Corp. Together they've got a 100+ years of driver design/build experience between them. We collectively know that that the bulk of light load wide-band-Full-Range drivers won't operate safely if driven very close to, or at their quoted X-max on constant/heavier regular loads. You can decide if me and my colleagues have the greater driver knowledge and operational experience, or member 5th, on this particular issue.
-------------------
Trying to use X-mech as some sort of standard is a long way off. The bulk of the industry doesn't apply this type of measure for the purposes of safe limit operation. There are too many operational variables influencing the driver to make reliable data.
For the bulk of applications (despite 5th's continuous assertions), Markaudio drivers work fine. I don't have ten's or hundred's of guys beating on my door with broken drivers in their hands. Please see my previous recent posts. From BR's, vented, MLTL's, Damped Air Coupled to Horns, Sealed etc, etc., there's lots of Markaudio drivers in these box types doing their work.
I do accept that better illustrating the operational description of X is proving challenging. I've stuck with this thread in the hope that some progress and agreement would be made, or a bright new idea will emerge. This issue has been knocking around in the forum for the past year.
Cheers
Mark.
Last edited:
I'll wager MA's won't either using Fostex's 1 mm or less Xmax ratings, so with this sort of comparison mentality and factoring in some others thoughts/concerns, seems to me it's in MA's best interest overall as a manufacturer to list a 1 mm Xmax and use its measured 10% distortion Xmax as Xlim to CYA themselves warranty wise at least until some design revision
GM
Actually I wasn't referring simply to their full range drivers, of the manufactures you quoted the bulk of their drivers aren't full range and some of them don't even produce full range drivers, so I figured you were meaning all of their catalogue.
Interestingly though of the full range drivers that most of them produce, the aluminium coned drivers tend to have a higher moving mass to SD
ratio then some of your drivers do (I am assuming this is cone related), so would inherently be more durable. And most of them have significantly lower Xmax parameters too.
Fostex drivers have midget xmax figures and paper cones, if you're saying that they would fail when driven at less then 1mm one way then again I'd be surprised. I think you're making some sweeping statements with regards to full range drivers and I admit that I am too. There are probably lots of them that will survive at rated xmax and then again there are probably some that wont.
Now as you've mentioned ,lots of manufactures don't provide an Xmech parameter. Of those that do it would appear that they are using it as a red tape keep out zone.
As far as I am concerned every manufacturer should provide you with an Xmech parameter, the fact that a lot of them don't isn't a huge concern because like I said, most drivers can be run at operational Xmax without damage occurring. Now lets say some of the drivers cannot be run at Xmax, but the manufacturers don't quote an Xmech parameter. I think this is inherently bad and misleading, but hey maybe it goes on more then I thought. Still, just because others aren't quoting Xmech under these circumstances, doesn't mean that you should choose to join them too.
The fact is simple, 1- the xmax figures you quote don't accurately convey anything regarding the safe operating excursion area for your drivers. 2- People are damaging your drivers from over excursion.
Just from those two points alone it would seem that a recommended maximum allowable repeatable excursion parameter would be beneficial in your datasheets.
There really is nothing more to it then that. If you know from experience that something like the CHR70 won't enjoy being repeatedly driven to 4mm peak to peak (2mm one way) then just say so in the data sheets.
Currently all you say is
Which to an experienced loudspeaker designer (but not perhaps acquainted with your full range drivers) would mean, look at the xmax parameter and if you're still within it then you're safe. Except you wouldn't be, again from my perspective this somewhat necessitates some kind of maximum repeatable excursion guide, even if it is just a safe guesstimate.
I'd be willing to bet that this method is applied by far fewer DIYers than you imagine. I'd also be willing to wager a large sum of money that the vast majority of DIYers simply install the drivers, put on some music that they like and then listen at reasonable volumes while the drivers burn in. Then, once they start sounding sweet, they start to take the volume a little louder and then rely on common sense and intuition to prevent excessive excursion and possible damage.
Furthermore, I do not think a high-pass filter is "obvious" at all. Certainly it should be used if one plans to consistently power the driver at the bleeding edge while relying on a woofer for low end. However, I do believe this situation is the exception, not the rule.
Case in point; not only do I have no high-pass on my MA EL70s, I EQ the signal to enhance the bass frequencies (and the top end), not supress them. So, technically I am doing exactly the opposite of what you consider "obvious", however I can still easily maintain a consistent, clean, distortion-free 85-87dB SPL in my living room, with deep, rich, fast bass down into the high 30s to low 40s. Expecting any more than this from 4x 20-watt, 4" full-range drivers does not seem reasonable to me, so I stop there. I have taken it louder briefly, but the excursion did seem excessive (but still not as bad as the excursion displayed in the video Mark referred us to), and I honestly rarely have a need for much beyond about 82db SPL, so it is pointless to push it just to "see if I can".
Last edited:
My "idiot proof" idea for near field monitoring was to use the MA Alpair 12's for their huge Xmax, low Fs and high power handling (for an FR) and run them with a T-amp at 10 watts into their 8 ohm load. After break-in, I assumed they would never suffer reliability problems no matter what 10 watts of signal went to them. Would a sealed box with the MA drivers be better since it limits Xmax at low frequencies or would it be worse since it increases the stress on the cone from the increasing air pressure?
I like the idea of full range with a USB DAC T-amp but other people will test them out with occasional clipping and they would be horrified if they cracked the cones. Am I being too paranoid or will this cause cone failure with drum solos and "electronic sound"?
I'll wait for Mark to publish "safe Xmax" figures for his drivers then simulate in various boxes until I can find the proper setup for reliability reasons.
I like the idea of full range with a USB DAC T-amp but other people will test them out with occasional clipping and they would be horrified if they cracked the cones. Am I being too paranoid or will this cause cone failure with drum solos and "electronic sound"?
I'll wait for Mark to publish "safe Xmax" figures for his drivers then simulate in various boxes until I can find the proper setup for reliability reasons.
When driving an Alpair 12 to clipping at near-field, hearing damage would be a greater risk than driver damage, IMO. Again, this is based on my experience with EL70 (which are less capable than Alpair 12). At near field, my ears begin to suffer long before the driver does.
Last edited:
I don't find this surprising if they are building a proven design, such as some of Zaph's builds. But if the DIYer is going to design the cabinet themselves then they should really be doing it computer aided with some design software. I mean this is easy to use stuff and most importantly free.
I should have clarified the situation a little because that was perhaps misleading. If you simulate boxes with the drivers you see that it is 'obvious', given the limited real world excursion, that they are going to require a highpass if you want to make sure you don't damage them. Sure most music doesn't have a lot of content in it that would pose a threat that low, but in lieu of this thread I'm erring on the side of caution.
The EL70 is a paper coned unit and as far as I am aware the cracking/splitting deformed cones are only the aluminium ones due to the materials properties.
Either way a small full range driver isn't going to give you 'proper' bass down that low no matter how much you EQ it. And even if it ended up flat to 40hz in room with some output down to 30, the distortion down that low would be rather high indeed. What type of cabinet are you using them in anyway?
This is somewhat besides the point though. That point being that without a figure quoted for a safe repeatable excursion, you're guessing as to what the driver can realistically cope with. When designing loudspeaker systems I don't like having to guess at what a parameter as crucial as a safe level of excursion might be. Maybe I am in the minority and by that logic every loudspeaker manufacturer providing drivers to the general public should stop quoting xmax figures because hey, most DIYers don't bother using them
Judging from what Mark said in post #51, you may have a long wait, as he stands by the Xmax figures, but says less than half of that figure is safe.
A clipped amp can put out up to 3 dB more power than rated, so even with a 10 watt amp it probably would be possible to exceed half of Xmax even with a sealed cabinet, and would be quite easy to do with a ported cabinet.
Clipping is most likely to occur down low, where the driver has the least output and our ears are less sensitive to distortion.
Your question "Would a sealed box with the MA drivers be better since it limits Xmax at low frequencies or would it be worse since it increases the stress on the cone from the increasing air pressure?" is good, but a sealed box limits excursion, not Xmax, which is a fixed parameter.
My suggestion is to measure excursion with pink noise at the level you normally listen to music at, if excursion is within about 1/2 of what the Mark Allen Xmax figure is, the speaker should hang in there.
I suggest pink noise rather than music because it has all frequencies present, while the wide variations in music and mastering makes it hard to arrive at a "safe" level, many old reliable recordings have little content below 50 Hz, while I am often surprised at how much sub 30 Hz level many current "benign" artists have in their recordings.
Art
IIRC, I read somewhere that MA doesn't recommend horn loading his drivers for ?? reason. If true, then it seems to me that a small sealed cab would be no less potentially harmful, so all things considered, some form of ~aperiodic loading [leaky sealed] is the only small cab option which ideally will be simmed at whatever the desired amp or driver power rating is to ensure it doesn't exceed its Xmax/whatever.
GM
I am under the assumption that there are far more DIYers taking proven designs and building them rather than doing their own designs from the ground up. Perhaps this assumption is wrong, but it is based on what I have seen in this forum so far, especially here in the full range forum (not so much the case over in the sub-woofer forum, where many more members seem to be delving into enclosure design, using the software, etc.)
As I said, you can ensure that you won't damage them by listening at reasonable volume. "Reasonable" is considered by many to be subjective, however I would wager that there is a vast majority of listeners who would agree on what "reasonable" is and also agree that at reasonable volume, these full-rangers will not be damaged (whether high-passed or not).
I am aware of this and I have to admit that I have no experience with MA metal-coned drivers. However, I am still confident that my definition of reasonable volume (which I think is in line with the majority of listeners) would not put the CHR-70 at risk. This is just subjective opinion, but I am right far more often than I am wrong about these things. The fact that only a select few people are damaging Mark's drivers might have something to do with this hunch of mine.
You'd be surprised. I know I was (and still am). I have 2x EL70 in the Planet-10 "microTower" design ("Howard Castle" variant). The amount of bass leaves many searching for the invisible sub. Would a sub do better ultra-low-end? Certainly. Is it necessary with the microTowers? For many (from what I have gathered), the answer is "no", but these are also people who can agree on what "reasonable" volume levels are.
This is somewhat besides the point though. That point being that without a figure quoted for a safe repeatable excursion, you're guessing as to what the driver can realistically cope with. When designing loudspeaker systems I don't like having to guess at what a parameter as crucial as a safe level of excursion might be. Maybe I am in the minority and by that logic every loudspeaker manufacturer providing drivers to the general public should stop quoting xmax figures because hey, most DIYers don't bother using them
Well, I am not a designer of loudspeakers, but I do not feel as though I am "guessing' about the excursion of my EL70s. I can observe it directly while listening to music, and I somehow just know what Mark means in his (admittedly vague) warning about "large movements". It is also quite evident that many, many fantastic speakers have been designed around Mark's drivers despite that fact that he does not list Xmech.
So it seems that it is a minority of designers who require this spec to design a speaker and it is a minority of listeners who are damaging the drivers. Perhaps both of these minority groups have the same definition of "reasonable volume"?
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.