LE14h-3

[Dr.db]

Does anyone know the excursion capabilities of the LE14H-3 woofers?
How much is x-max and x-mech?
I´ve read the technical reference´s from Techbot but couldn´t find anything...

Btw, has the older LE14H the same specs concerning excursion?


Thanks a lot,
Olaf

[RMC]

Hi Olaf,

I didn't have more success than you when looking at all the LE 14 info that I have.

I know we are missing part of the equation but as a general guideline only consider the following:

LE 14 H, VC length .630 in., Xmax 8.38 mm

LE 14 H-1, VC length .750 in., Xmax 8.5 mm

LE 14 H-3, VC length .780 in., Xmax ?

LE 14 H-4, VC length .780 in., Xmax ?

To play it safe I would tend to stay within the 8.5 mm Xmax number for the LE 14 H-1

This logic is based on the general woofer excursion formula for Xmax = (length of coil - height of gap) / 2. Again, I know we are missing height of gap, so as they say we have to play this by ear... Hoping this may be of some help to you.

Regards,

Richard

[Dr.db]

Hi Richard,

thanks a lot for your great info´s!

I´m just wondering how much x-mech could be?
The surround doesn´t look like it supports exessive excursion... And I expect the LE14H-3 to "bottom out" like the 2235h when driven hard because there isn´t much clearance after linear x-max...

Regards,
Olaf

[Ian Mackenzie]

The LE14-3 spec sheet is located in the transducer data forum in reference section
Gap 0.28 inch

[RMC]

Hi Olaf,

RE: "I´m just wondering how much x-mech could be?" and "there isn´t much clearance after linear x-max..."

Over the years i've seen, read and kept a hell of a lot of woofer data sheets, and keep looking at some more these days from Eminence, among others from Europe and US manufacturers. This has showed me the difference between the Xmax number and the Xmech (or Xlim) number can be anywhere on the map...

Sometimes there is a large difference between those two numbers and sometimes the difference is small. The clearance after linear excursion varies so much from one driver to another that I would not even make a guess on it.

This is to say it is just too risky for me to attempt an Xmech or Xlim number or even a "rule of thumb" here. Since I'm looking at some Eminence woofers now here's a few examples of those Xmax/Xlim differences: 4/8 mm; 6.7/15.5; 4.2/8; 3.2/10.9; 7.2/16; 8.52/15.7; 9.1/14.5. And this is NOT a scientific sample but just a few of those I have in my laptop.

As can be seen from the above, sometimes Xlim is double or so Xmax, sometime triple or so, sometime just about 50% more. And I have seen proportions of less than these... Xlim is usually more than Xmax, however by how much is anyone's guess I assume.

Finally, many manufacturers provide an Xmax number, but not necessarily an Xlim figure...

Regards,

Richard

[Dr.db]

The LE14-3 spec sheet is located in the transducer data forum in reference section
Gap 0.28 inch

I´m sorry, but please tell me what´s the conclusion of that? I´m not familiar with the technical backround...

Can you tell what´s the maximum excursion before damage?


@Richard: On some drivers it really differs a lot.

[Ian Mackenzie]

We don’t know that but attempting to use the driver beyond the Xmax is not recommended.

The longevity of the suspension components will be reduced.

You need to look at either more drivers or a different driver if you are thinking in those terms. l am unsure why you are asking this type of information if your not at all familiar with the technical background?

This is why there are numerous different woofers available on the planet ��!

[RMC]

Hi Olaf,

RE: "And I expect the LE14H-3 to "bottom out" like the 2235h when driven hard because there isn´t much clearance after linear x-max..."

Your indication above regarding 2235H seems to be right according to the document attached (Xmax 8.5 mm and Xmech 11 mm) which isn't a lot of loose between the two numbers. This also confirms what I wrote in post # 5 about the difference that can be large (as in my previous post) or can be quite small (as in 2235H), plus that numbers can be anywhere on the map... If my memory is correct, I'm 90% sure that attached document is from Giskard and I did take it on this site but can't remember from which thread.

As for your expectation that LE 14H-3 would bottom out like 2235H I cannot say about that.

RE: 0.28 GAP With regards to the Gap mentioned in post #4, I plugged that number in the traditional Xmax equation mentioned in post # 2: .780 - .28 = .5 /2 = .25 inch or 6.35 mm, which doesn't appear consistent with the other versions of LE14 (excl. A) for which we have an official number: LE14H 8.38 mm and LE14H-1 8.5 mm.

On the other hand, I have a May 1988 JBL doc. about gap gauge service procedure (see attached on 2nd page) where .057 is the number given for "all low frequency transducers with 4-inch voice coils". For the sake of it, I plugged that number in the Xmax equation to see what it would give: .780 - .057 = .723 / 2 = .3615 in. or 9.18 mm, which is a closer number to the 8.5 mm mentioned above for H-1. The H-3 version's voice coil is a bit longer (.780) than version H-1 (.750) so could that explain the former's bit higher Xmax here (< 1 mm) naturally if the gap height remains the same?

The above-mentioned 1988 doc. covers for sure at least three versions of LE14, the A, H (1979) and H-1 (1982). The H-3 and H-4 versions were issued in 2000 and 2007, so after the document. Could it still be applicable? The case remains open i guess...

RE: @Richard: On some drivers it really differs a lot.

Yes, it does and its difficult to predict since the Xlim number differences from Xmax are all over the map...

For my part, I indicated right from the start I had no more success than you in finding a definitive Xlim answer. However, I've been trying hard to find peripheral info that MAY get us there or be of some help to you... Regards,

Richard

P.S. Problem attaching files I will re-try later.

[RMC]

JBL Gap Gauge Service Procedure and Usage Guide (1988)[1].pdf

[Dr.db]

@Ian:
Actually it´s very simple why I came up with this question. I have owned 2235h´s in the past and 99% of the time everything was under control, but once a year a certain track caused the 2235 to bottom at the same level. That´s why I changed to TAD 1603, it has about the same linear xmax but a much higher xmech (maximum excursion before damage). The TAD has never bottomed out!
JBL 2235H: 8,5mm (xmax) and 11,0mm (xmech)
TAD 1603: 8,0mm (xmax) and 18,0mm (xmech)

I´m absolutly not purposing to run the LE14h-3 beyond xmax on a daily basis, why should I?
But it could happen eventually... And it would be nice to know if the woofer would bottom out or have a enough clearance in such a situation.


@RMC:
I believe we have to wait until someone with specific backround informations shimes in, but thanks so far!

[Ian Mackenzie]

Okay

It would have been made more sense if you explained why you making the question up front.

However, you need to demonstrate the facts about your comparison such as the tuning frequency , box volume , vent dimensions, power input ect in each case. Do you use a subsonic high pass filter?

The comparison is too general to draw any real conclusions.

The mass control ring may limit excursion.

By today standards the 2235H Xmax is not really a sub woofer meaning the Xmax is too small compared to a sub driver with 13 or 19 mm Xmax

[Dr.db]

Both woofers had been in the original box-sizes with the specific tuning. JBL 2235 was in 5cu.ft and TAD 1603 in 6cu.ft enclosure while testing... I was using a subsonic and was within the power limits. But I don´t want to start a discussion about these specific woofers, it was just helping me to illustrate my question.

My feeling is that the LE14H-3 probably has 8mm linear xmax and maybe 10-11mm xmech, but that´s just a guess.

[Dr.db]

For the record l have never heard the mechanical limit of a 2231-2235H in 37 years with a 450 Watt rms power amp.

Ok, I must have made some kind of mistake!

[Ian Mackenzie]

If a power amp clips then you are far more likely to hit the wall in terms of Mech X max.

These days I used an 800 watt rms power amp.

I recommend 6 db headroom on your bass amp which is easy these days.
But you really don't want to be anywhere near or beyond redlining the driver on Xmax.
If you are you are asking too much of the driver. The BL curve and everything goes to hell.

[RMC]

Hi Olaf,

RE: "The mass control ring may limit excursion." (Post # 11)

According to Giskard's table in post # 9, the 2234H "(2235H with mass ring removed)" has the SAME Xmax and Xmech numbers as the 2235H, so the mass ring doesn't appear to be part of the explanation here. Regards,

Richard