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Old 25th November 2011, 02:13 AM   #1
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Default Tang Band Xmax

I just wanted to get a sense from Tang Band driver users out there about the rated Xmax of these drivers as opposed to their real-world excursion limits.

The reason that I am asking is because have a pair of 3" Tang Bands (my first and only pair of Tang Bands so far) and I am amazed to see them go way, way beyond their excursion limit while maintaining excellent sound quality. To be more specific, I have the W3-881SI which have an Xmax of 0.5mm listed. Based on my experience with these drivers, I have to say it almost seems like a mistake in the specs; it seems more like it should be 0.5cm.

Since I was home sick all day, I decided to perform an experiment. I intentionally ran these drivers well beyond 0.5mm excursion for the entire day today. When I say well beyond, I mean to say between 3mm and 4mm with bass peaks pushing them further out, perhaps to 5mm. I normally wouldn't do this, but these things cost me peanuts and I am a curious person by nature.

The result: Nice deep bass, no ill effects. Some of you may have seen the video of me running some Leonard Cohen through these drivers. At that time I had assumed that I was pushing the drivers near their limit. Well, I can say with confidence that I pushed them beyond that excursion all day today and heard nothing but smooth sound. No warble, no slap, no crunch, nothing.

I have briefly pushed them to the point were they became less coherent, when the bass began to disrupt the fidelity of the midrange, but the excursion was simply ridiculous by that point and I did not want to see what happened next Even that little test didn't seem to have any lasting consequences. I am listening to them right now and they are working away on some smooth, low bass from a Jack Johnson track. I continue to be amazed...

Anyone else have a similar experience with any of the Tang Bands (or any other drivers, for that matter?) Anyone care to offer an explanation as to how this is possible? Could it actually be a mistake in the specs?

Last edited by cogitech; 25th November 2011 at 02:18 AM.
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Old 25th November 2011, 08:13 AM   #2
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I think Xmax is defined as the zone where the motor has full control over the cone, in other words the place where the magnetic field has a grip on the moving parts so that other specifications are still in line. However, the driver may work fine outside that range, just a little differently than in the "comfort zone". Xmech is a related spec that states the physical excursion limits of the driver, where something whacks into something else. Between Xmax and Xmech there is a territory to explore Surely it's different between different drivers.
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Old 25th November 2011, 03:59 PM   #3
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Quote:
Originally Posted by kristleifur View Post
I think Xmax is defined as the zone where the motor has full control over the cone, in other words the place where the magnetic field has a grip on the moving parts so that other specifications are still in line. However, the driver may work fine outside that range, just a little differently than in the "comfort zone". Xmech is a related spec that states the physical excursion limits of the driver, where something whacks into something else. Between Xmax and Xmech there is a territory to explore Surely it's different between different drivers.
Thanks for your response.

Yes, I have read some of the debate about Xmax/Xmech surrounding a popular brand of driver, so I am aware that these terms are open to some interpretation (or at least the application of said terms is not entirely agreed upon).

So, it only follows that each individual type of driver must be evaluated in the real world with these parameters in mind (if they are provided) but that the parameters themselves are not "absolutes". With some drivers (such as the ones in question) it is possible that there is ample room to "explore" as you so aptly stated it , but with other drivers, that exploration could quickly result in damage (ie. IF Xmech < Xmax THEN ).

Going forward I will let the price of the drivers (much more than listed specs) determine just how much I will "explore" the excursion

Last edited by cogitech; 25th November 2011 at 04:07 PM.
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Old 25th November 2011, 07:11 PM   #4
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The tangband, with its tiny linear excursion, is one of the reasons why I think that all manufactures should provide an Xmech figure. As you've found out, with such a tiny amount of linear excursion (xmax) the rest of the moving parts are quite capable of operating significantly above this without causing any apparent harm to the driver. How far beyond xmax you don't know though, so it's guess work.

In this case the xmax figure would be a useful design parameter to use for say in a three way (when designing the cabinet and highpass) for keeping everything low distortion (within xmax) for normal listening levels. But you would also know (if Xmech were provided) that the driver can safely operate out to say +-3mm without any undue harm, this allowing for transient peaks perhaps in classical music, or for the times when you want to watch a movie.

As explained before normal hifi drivers tend to have say 25-50% more excursion capability, beyond their linear xmax, before you will cause any damage to the driver. This typically results in drivers having say 5mm of xmax but 7-8mm of Xmech. Designers expect this, but as the xmax figures are always reasonably high, you never tend to run into problems with exceeding xmax unless you're wanting the driver to do something it isn't intended for.

If a full range driver is designed and comes out having a tiny tiny xmax, like this tangband one, then you've got a situation where Xmech is considerably larger perhaps then xmax and in reality this area needs to be used effectively to make the most of the driver. It would be nice to know what Xmech in this case actually is, but we are not told!
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Old 25th November 2011, 09:07 PM   #5
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Originally Posted by 5th element View Post
If a full range driver is designed and comes out having a tiny tiny xmax, like this tangband one, then you've got a situation where Xmech is considerably larger perhaps then xmax and in reality this area needs to be used effectively to make the most of the driver. It would be nice to know what Xmech in this case actually is, but we are not told!
I agree 100%.

If I was to judge the usefulness of this driver based on specs alone, I certainly would not have attempted to put it into a 13.3 litre cabinet tuned in the hi 40s to low 50s and run the exursion way beyond Xmax. I believe that I am making the most of this driver by doing so based on the specific goals/criteria that I had in mind.

This is not to say that the intention is to always use the drivers well beyond the specs, but it does allow me to really enhance the bass (either with EQ, "loudness" control, or a simple bass knob) while maintaining an "easy listening" SPL. They are truly "full range" in this application.

In a way I am glad I am so ignorant of these specs and of speaker design in general. I think it allows me to see that this hobby/passion/obsession/ is as much of an art as it is a science.

Last edited by cogitech; 25th November 2011 at 09:20 PM.
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Old 25th November 2011, 09:54 PM   #6
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is as much of an art as it is a science
I Wouldn't go that far. Once upon a time things were more art then science, but then clever people came along and changed that. One such person is Martin King who decided to figure out exactly what was going on in funky MLTL type enclosures. No doubt this is/was a rather complicated process of comparing old simulated predictions for TLs and ported cabinets and then building and measuring many variations that combined the two to eventually come up with the design equations that will now accurately simulate how a given MLTL design will perform.

What once was more of an art has now become science.

Most of loudspeaker design is now well established science and the art aspect of it, imo, is managing to come up with visually attractive packages that manage to satisfy being extremely well designed too (and without too many compromises).
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Old 25th November 2011, 10:46 PM   #7
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Quote:
Originally Posted by 5th element View Post
I Wouldn't go that far. Once upon a time things were more art then science, but then clever people came along and changed that. One such person is Martin King who decided to figure out exactly what was going on in funky MLTL type enclosures. No doubt this is/was a rather complicated process of comparing old simulated predictions for TLs and ported cabinets and then building and measuring many variations that combined the two to eventually come up with the design equations that will now accurately simulate how a given MLTL design will perform.

What once was more of an art has now become science.

Most of loudspeaker design is now well established science and the art aspect of it, imo, is managing to come up with visually attractive packages that manage to satisfy being extremely well designed too (and without too many compromises).
Well, what I mean is that the "pure science" approach would have guided me away from the design that I ended up with (or completely dismissed it). If I had been "educated" about the science behind this, I might not have thrown caution to the wind and taken a chance with these drivers in this type of box. I had a vision in mind with respect to the physical dimensions and the practical usage of the loudspeakers and I had a pair of drivers and some simple tools. In a matter of a few very enjoyable hours, I successfully realized that vision, and it seems to me that the process was as much art as it was science. Perhaps more luck than anything else. If the drivers had blown the first time I exceeded Xmax, I would certainly be singing a different tune

I do not know enough about Martin King et. al. to be any sort of judge of their work, except that I am a direct beneficiary of such work since building my Planet-10 microTowers. I followed the plans as precisely as possible, used much higher quality materials, cut no corners, etc. This was way more science than art (except perhaps in my finishing work) and the speakers sound incredible. Considerably better than my own creation, to be sure. Yet, my little "nanoTowers" are very pleasing speakers and are much more than the sum of their parts (IMO).

So, the question remains; how much can we really say about the application of a driver based on a parameter such as Xmax? The scientific approach would seem to say "well, if we plug these numbers into our software, we see that we will get such and such excursion at such and such frequency and power input, therefore..." whereas the artistic approach seems to say "I don't care, let's just build it and see what happens".

The second approach is far more appealing with inexpensive components.
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Old 25th November 2011, 11:12 PM   #8
18Hurts is offline 18Hurts  United States
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I have some Tangband 3" drivers from the Logitech Z5500 system

Built surround sound speakers out of them (4 per enclosure) and was surprised how much they could put out running full range. Considering the people that buy that system and blast it--I figure TB just under rated the Xmax or has a huge Xmech to keep the speakers intact.

Xmech would be a great spec to know--some drivers when used as subwoofers will hit Xmax at 90 watts but Xmech is at 290 watts (LAB12?) when tuned to infrasonic frequencies. To match an amplifier, I'd use a 200 watt amp instead of a 100 watt to gain the headroom although it would generally not be driven that hard.

I can understand why manufacturers don't provide Xmech--because some folks would design their enclosure to run on the edge of destruction and increase warranty issues. As a manufacturer, the Xmech is a safety so they won't be "at fault" when a person makes a box with air leaks.

Maybe Tangband does what Cerwin Vega does (or used to), under rate Xmax with a large Xmech? My Cerwin 15's (pro woofers) move a lot farther than their 4.5mm Xmax would indicate although the accordion surround will tend to limit stroke at very high levels.
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Old 25th November 2011, 11:17 PM   #9
sreten is offline sreten  United Kingdom
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Hi,,

Numbers hardly ever tell the real story, unless you understand them.

Here we have a underhung voicecoil, but by only 1mm, probably
around 7mm long in a 8mm gap. Xmech is generally useless.

Given the above and the resulting BL curve versus excursion, its
fair to say excursion causes graceful bass overload, the more
excursion the more distortion up to the unusable point.

What you can say about the above is it probably works well up
to about 50% of the coil in the gap, giving +/- 4mm or so.

Halving BL changes all the small signal parameters, and a design
to work well pushed, needs to take this into account, most don't.

rgds, sreten.
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Old 25th November 2011, 11:39 PM   #10
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Quote:
Originally Posted by cogitech View Post
Well, what I mean is that the "pure science" approach would have guided me away from the design that I ended up with (or completely dismissed it). If I had been "educated" about the science behind this, I might not have thrown caution to the wind and taken a chance with these drivers in this type of box.
Indeed I assumed that's what you were meaning before, but even though something works, I wouldn't assume it's the best just because it happened to be pleasing the first time round.

Your vision created the style of the box and then your enthusiasm ended up creating the loudspeaker that you now have today. Nothing can be said that will take away from that accomplishment, however, the cabinet could also be easily incorporated extremely successfully into a more 'optimum' alignment for this driver.

As you've built such a large cabinet it does indeed offer room for experimentation if you so desire. I cannot tell you that other alignments will sound better in your room, only that the theory shows a strong preference for a different arrangement then you've currently got.

If the long narrow aspect of the cabinet happens to lower the tuning frequency by a certain % due to some MLTL loading, then this, in my opinion, necessitates some impedance measurements to make sure that your simulations match the real world.

If I were in your position I would start by measuring the impedance to check where the tuning frequency lies. After having done so I'd want to experiment with a higher port tuning (measured tuning) of around 80hz and then heavily stuff the boxes and see how that sounds. Theory predicts it should sound better, although it might not have quite the same extension as you've got now.

The next thing I'd want to try, is again, heavily stuffing the enclosure, but filling the bottom of it with sand so that the net internal volume was significantly less ~4-5 litres and again going for a real measured tuning of around 80hz. Filling the bottom of the cabinet with sand should also greatly aid in the stability of such a tall/narrow cabinet.

I would do this because I would be curious, first of all to know how the simulated predictions match up with the real world and then to which one I prefer with regards to sound quality. This should theoretically educate me about the limitations of my design software, how perhaps a very tall and thin enclosure impacts on the tuning frequency of a ported cabinet with the port close to the bottom and then towards what type of alignments I prefer.

Of course if the cabinet showed significant TL loading, I'd want to try plugging up the port at the bottom and putting the port mid way up the cabinet to see if it had any change on the tuning frequency.

Quote:
Originally Posted by cogitech View Post
So, the question remains; how much can we really say about the application of a driver based on a parameter such as Xmax? The scientific approach would seem to say "well, if we plug these numbers into our software, we see that we will get such and such excursion at such and such frequency and power input, therefore..." whereas the artistic approach seems to say "I don't care, let's just build it and see what happens".

The second approach is far more appealing with inexpensive components.
Regardless of how expensive the components are you still have to build a box and this requires some considerable effort. This is the thing I want to minimise the chances of getting wrong.

We can say a great deal towards the application of a driver based on its Xmax, but more importantly we can quite simply state that it will sound worse when operating at greater physical excursion. All drivers become less linear as excursion increases, even if xmax isn't exceeded. The rate at which they lose linearity shoots up however when you exceed rated xmax.

This isn't your point though and when taken as a whole it basically states.

Quote:
how much can we really say about the application of a driver based on it's parameters
Well without them we can say nothing about it, because we now know nothing. With them though we can start to say a great deal.

I have no arguments against a built it and find out approach but the 'finding out' is the important bit. If you did indeed know nothing about a driver, then putting it into an application and measuring how it behaves would be a good way of finding out a lot about it. Simply building and then doing nothing except listening wouldn't tell you a whole lot. If it sounded crap you'd need to measure to figure out why, otherwise you'd be prone to repeating the same thing again. Just because something initially sounds pleasing doesn't mean you should stop there, that is unless you're perfectly happy with what you've got. But experience tells me that if there is room for experimentation at the possibility of improving things, at some point, I am going to want to try.
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