I decided to take some measurements on some of my LMS ultra drivers, as they did not seem to be reaching the advertised excursion levels.
With the driver free air, I was able to see that on the inward stroke, it would easily hit the spider support which is just over 1.5" from the cone. However, on the outward stroke, I was not seeing much more than 1.25" of excursion.
Is the stroke just non linear at this range?
My measurement system was crude, but fairly effective. I set a measuring tape on a fixed surface and aimed it towards the center of the driver. I then took a pencil with a soft eraser and marked it, so that I could see where on the measuring tape the pencil would touch the cone when the sub wasn't moving. I set it up so that it was at 3" on the tape. Next, I played a low frequency test tone so that I could hear the cone was tapping on the spider support. I slowly moved the pencil, eraser side first, towards the moving cone to see where it would impact. From these tests, I was unable to see outward excursion of over 1.25"
xmax on this driver is listed at 38mm with xmech being just slightly beyond that.
Quote:
Originally Posted by notnyt /forum/post/21820308
If my measurements are correct, it would have at least been nice to have accurate published specs to work off of when designing the enclosures. Granted, I can't really complain, these drivers are rarely pushed that hard, but for the price the specs could at least be accurate
Yeah that does suck Not! Would you run these without a xover if they wouldnt bottom out? I guess a smaller box would have been nice but you didnt change much of the box design from the mal build anyway did you? I remember you having to cut some bracing that was making contact.
They're the same boxes from my mal build with bracing adjustments. I don't know if I would change the enclosures much, or just go with a different driver like a 21" or something. Either way, it's just kind of disheartening.
if the case is that they will only 32mm outward travel, it would seem that there are a few other drivers that equal that. Mark had his UXL on the scope and I'm pretty sure it measured 3" P to P.
Rarely do I see any specs meet quoted and that goes for any commodity. Does any auto ever give a person city mileage? Xmax is now the go to spec or byword for one upsmanship in sales, as were max power ratings twenty years ago.
The TC Sounds video states almost 3.6" of throw which makes it 90mm or 45 mm xmech. Even if it's only 42mm close enough, but 32mm would give you a linear of 64mm which is only 2/3's of rated. I suppose I would have a major problem with that.
Quote:
Originally Posted by notnyt /forum/post/21820499
They're the same boxes from my mal build with bracing adjustments. I don't know if I would change the enclosures much, or just go with a different driver like a 21" or something. Either way, it's just kind of disheartening.
Sure are lots of guys having less than ideal experiences with these drivers; doing so @ $300-$400 ea. is one thing, but at this price point it is absolutely unacceptable. I was saving for 4 of these units, but perhaps I'll look to Mach V or elsewhere as others are suggesting.
Any way we can pool our resources and reboot the Mael-X!!!
Quote:
Originally Posted by 04FLHRCI /forum/post/21821434
Sure are lots of guys having less than ideal experiences with these drivers; doing so @ $300-$400 ea. is one thing, but at this price point it is absolutely unacceptable. I was saving for 4 of these units, but perhaps I'll look to Mach V or elsewhere as others are suggesting.
Any way we can pool our resources and reboot the Mael-X!!!
You know that a lot of the parts used to make all of these drivers are fairly common or comparable right? If you look at enough drivers from enough places it becomes obvious. For example surrounds. You have the large half rolls and the high rolls in foam and rubber. Or you might have the large triple roll accordian style. Those are what is most common on 18's. The surround on a Fi 18 is functionally the same as the one on the UXL, or RE Audio SX, Mal-X, or PSI recone, Xcon. I'm sure the manufacturers would say otherwise but whatever. The foam high roll surround on a Zv3 isn't going to perform any different from that the rubber one on a LMS so if the LMS does get surround limited to however many XXmm out by the high roll surround then so will basically any other driver using that style of surround including the Zv3. In case you were wondering the answer is no...the large half rolls don't seem to provide any more stroke before getting tight and also reduce SD btw.
Xmech is not usually limited by the coil bottoming in the motor anymore. It is usually the bottom spider triple joint cracking into the top of the gap or motor. Other times there are limitations in suspension stroke, slack in the leads, or cone to spider spacer. There are a large variety of spiders available but there are 3 frames that are the most common for long throw 18's and 15's. You have your 6 spoke (4 for 15's) like on a Mal-X your TC Ti basket which is now showing up in a lot of other drivers and your 12 spoke. There are others but these are most common. Drivers built on the same basket will usually have similar Xmech because the clearance from the spider to the top of the motor will be similar.
I guess the point of all of this is that is the surround is limiting one driver do not expect another using similar components to be any better. It will be limited the same way. If two drivers using the same frame are being compared they likely have similar xmech unless there is a limitation somewhere else.
Don't get me wrong, I love these drivers. There really isn't much competition for them at all in this range. As Ricci said, most drivers share many of the same parts, so there isn't going to be too big of a variation. However, when you're picking what to build, and you're using supplied specs to calculate something that should be straight forward such as available displacement, it makes a big deal when one of the specs are off by so much. At the time, I don't think there were any 21"s out that I would have considered. Now there is (sort of) the ftw-21. The B&C 21 is also a monster of a driver but it doesn't quite seem suited to low low content. However, for less than half the price, I could have went with double the number of high end 15" drivers and come out ahead on displacement. Some people also mentioned the XXX 18, but it is fairly inefficient and suffers from power compression as per Ricci's testing, so I would not choose it. There is more to bass than just the super low stuff. This is all theoretical, and I'm just rambling at this point. These drivers are great, and I love my setup.
Not still has 'the' system, and the LMS is 'the' driver, but the reported problems (at an increasing rate) and variance are not acceptable for ~$1k USD driver.
You guys aren't buying $200 Fi drivers here, this is supposed to be the best the industry has to offer.
Just sharing my thoughts, I haven't dropped any coin on LMS' yet...
Quote:
Originally Posted by 04FLHRCI /forum/post/0
Not still has 'the' system, and the LMS is 'the' driver, but the reported problems (at an increasing rate) and variance are not acceptable for ~$1k USD driver.
You guys aren't buying $200 Fi drivers here, this is supposed to be the best the industry has to offer.
Just sharing my thoughts, I haven't dropped any coin on LMS' yet...
Rob, you do realize that the difference between 32 mm and 38 mm in an 18" driver is about 1.5dB at 10 Hz, that is IF it's clean at rated X-max, which it never is, right?
The max CEA Ilk got from the LMS at 12.5 Hz in 200L was 97dB. At 38 mm it should have given 102dB. It could have been that the amp was at its limits, but I don't think that was the case because the same situation exists with all drivers tested, regardless of the amp used.
You know you're gettin' everything those drivers have to offer when you want it, so I wouldn't (and I never do in my systems either) sweat the dB you're missing on paper.
Josh, this might be a nifty little extra for your DB site. Use a piston excursion calculator to predict output at 'x' Hz and match that against what really happens. You can reverse calc and find the actual throw from the test.
Only thing to remember is that the calculator uses the Sd, so it would be wise to measure the actual drivers Sd before the calc (and to check that against Manufacturer's sD spec).
Yes, I realize the db difference is small, but that isn't necessarily the point. The point is the numbers being thrown around and advertised for the driver don't line up with reality. At $900 a driver, that's kind of sad. As mentioned earlier, in the video they mention 3.6" of throw. In reality, it's more like 2.5"
Quote:
Originally Posted by notnyt /forum/post/21823026
Yes, I realize the db difference is small, but that isn't necessarily the point. The point is the numbers being thrown around and advertised for the driver don't line up with reality. At $900 a driver, that's kind of sad. As mentioned earlier, in the video they mention 3.6" of throw. In reality, it's more like 2.5"
I asked Thilo about this issue earlier this year. I will paraphrase what he said:
He said he made some measurements on a late production unit.The point at which the cone hits the spider is 40mm one way, but that also happens to be the point at which the coil has left the gap half-way, so the driver will be in its range where the distortion is definitely higher than 3%, so it's already beyond its useful range. He said they could have gotten a few more millimeters of excursion, but it would have sacrificed the stability of the voicecoil a bit, since increased distance between spiders prevents voicecoil rocking, so it's a tradeoff.
Still it would be good to see someone else take some additional measurements of this.
$900 is Maserati pricing. It should be a statement piece with specifications accurate to 2 decimal places. Proof is in the pudding, and performance does speak for itself, but at this price point there should be no questions.
Quote:
Originally Posted by djarchow /forum/post/21823068
I asked Thilo about this issue earlier this year. I will paraphrase what he said:
He said he made some measurements on a late production unit.The point at which the cone hits the spider is 40mm one way, but that also happens to be the point at which the coil has left the gap half-way, so the driver will be in its range where the distortion is definitely higher than 3%, so it's already beyond its useful range. He said they could have gotten a few more millimeters of excursion, but it would have sacrificed the stability of the voicecoil a bit, since increased distance between spiders prevents voicecoil rocking, so it's a tradeoff.
Still it would be good to see someone else take some additional measurements of this.
Even if the back travel is limited to 40mm, the forward excursion only seems to be able to move 32mm, while the cone is hitting the spider on the inward stroke.
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
AVS Forum
34M posts
1.5M members
Since 1999
A forum community dedicated to home theater owners and enthusiasts. Come join the discussion about home audio/video, TVs, projectors, screens, receivers, speakers, projects, DIY’s, product reviews, accessories, classifieds, and more!