4.7 Cu ft too big for LE14A ?

[LE15-Thumper]

Old JBL kits a-la- Lancer 101 . Big cabs from Barzalay. 4,7 cu Ft. Port is 4.75 dia by 13" long. Tuned ok ? Suggestions ?

[GordonW]

Wow, that is kinda big. You could actually put TWO LE14s into EACH 4.7 cubic foot cabinet, and they wouldn't complain about it!

However, that alignment isn't too bad... it's definitely a major EBS-style alignment, with about a 25 Hz port tuning. Kinda a shallow roll-off starting at about 100 Hz, but only down like 4 dB at 28 Hz. Lots of low bass extension, if not a whole lot of relative output down there, compared to a smaller box...

Regards,
Gordon.

[4313B]

Just for reference you can see JBL's recommendation for the old LE14A courtesy of Bo's scan - http://www.lansingheritage.org/image...ans/page09.jpg

[Earl K]

Interesting - I'd never looked at that before

Suggestions ?

- You didn't mention if this 4.75" duct was round or square. ( ??? )

- I wouldn't force an old le14a with it's short coil ( .6" ) into a system alignment that is underdamped. That box size implies a system alignment with a Q(tc) of .458 ( according to my software ). These type of underdamped alignments are asking for trouble (IME ) due to most peoples expectations of getting maximum spl from their woofers . The le14a is only rated for 100 watts. That large box, with that low a tuning, will over-excursion the voice-coil - after about 70 real watts are dumped into the system.

With these old drivers and their heavily worn suspension systems - I wouldn't go larger than a system tuning of .5 Q(tc) . This sort of box tuning is known as being "Critically Aligined" .


This alignment yields a box size of @ 3.4 cu' ( 96.8 litres ). I'd tune it to 30 hz with one 3" Ø duct that is 4" long . This gives a theoritical 3db down point of around 35hz. It still has a great looking curve that when combined with some room gain will give fabulous bass.

One can always decrease a boxes internal volume by simply occupying some of its space. Sand filled plastic bottles has been a good suggestion .

[4313B]

That large box with that low a tuning will over-excursion the voice-coil

True, ~ 25 watts maximum input at ~ 32 Hz with that low of a tuning in that large of a box. The old LE14A can handle maximum rated input when tuned as low as 35 Hz. Tuned lower than that, power handling sags rapidly.

[Earl K]

True, ~ 25 watts maximum input at ~ 32 Hz with that low of a tuning in that large of a box.

Interesting,,, my MacSpeakerz displays this power limitation occuring at around 37hz . The same curve also suggests holding the maximum wattage to 70 watts . I'll post the SIMS sometime today. I have to hook up a small network to port over the screen captures since that software only runs successfully on an older computer.

[4313B]

I was thinking about running those old JBL recommendations and posting them just for grins. We can compare results if desired. I've got Winspeakerz too.

[Earl K]

We can compare results if desired. I've got Winspeakerz too.

Okay, I'm interested in doing some comparisons . I'll set up the network this morning and then come back online .

EDIT at about noon 2/9/05

Here's a simulation mostly focussed on excursion.

( Hopefully this image file type will register .
Nope, a TIFF image won't load - back to the drawing board )

[Robh3606]

I run my Le-14A "Subs" in 4 cu. Ft tuned to 31Hz using WinIsd. Two 3" ports. I was worried about them keeping up with my mains with the sensitivity differences and there limited X-Max. They are powered with the Parts Express plate amps so I quess they get about 150 watts each.They really surprised the me!! I have never heard them bottom or loose it even at some rather nutty levels. I think if you keep them where they are not asked to do large excursions they can really do a great job. With room gain I am good to about 25Hz before it falls off the cliff. If you do go that big a box don't tune them too low. Keep it up high like Earl is saying. You won't be disapointed.


Rob

[4313B]

Here's what I get running the four old JBL recommended enclosures and tunings in Bass Box 6 Pro with typical fill and no volume displacements for driver, duct, bracing.

[4313B]

The sharper the knee in the amplitude response graph, the poorer the transient response. This can be seen in the group delay graph. Sharp changes in group delay are considered undesirable. I recall some people thinking that anything lower than 25 ms around 20 Hz is "good enough". Naturally it's subjective and dependent on source. The old B380 and B460 assisted alignments are examples of very high group delay (> 40 ms at ~ 26 Hz) and some people definitely do not care for them, especially for classical listening. For explosions and other such things found on Laserdiscs and DVD's they are quite fine. Anyway, whatever...

[LE15-Thumper]

You didn't mention if this 4.75" duct was round or square. ( ??? )

Round ports

What is EBS tuning ?

And yes, I get pretty good extension from them, but they "slap" easily. If someone has a better tuning suggestion, I would love to try it. Someone mentioned two Woofs in this box ?
What would I have to do with the ports ?

I think these boxes were designed before T/S parameters became the norm.

[4313B]

What would I have to do with the ports ?

Cut the ports down to something like 8.25" and see if that helps a bit.

Someone mentioned two Woofs in this box ?

Put your two SUB1500's in it, brace it like hell and seal it tight.

What is EBS tuning ?

Extended Bass Shelf. Think JBL Model 4315 Studio Monitor.

[LE15-Thumper]

Cut the ports down to something like 8.25" and see if that helps a bit.
Put your two SUB1500's in it, brace it like hell and seal it tight.
Extended Bass Shelf. Think JBL Model 4315 Studio Monitor.

2.35 cu feet per Sub1500 ? Isn't that a bit small ?

[4313B]

Isn't that a bit small ?

I wouldn't know about such things.

How come you are messing around with these old LE14A's anyway?
eBay 'em and make 'em someone else's problem.