Lab 12 hitting xlim ? - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 5th September 2014, 04:48 PM   #1
mark100 is offline mark100  United States
diyAudio Member
 
Join Date: Dec 2010
Default Lab 12 hitting xlim ?

I've been trying to find a Labhorn's peak power handling edge by slamming a drum recording through it.

The edge seems to be when I get a loud clunk/knock out of the Lab 12s

I have a fast min/max voltmeter saying this happens at around 148v PEAK.
A little below that, no problem...
So I know where to back off...

But what I don't get is what makes the clunk/knock.
I have a lab12 torn apart and the suspension doesn't seem like it could ever move in or out enough to let the voice coil or anything else, hit anything.....

I guess I don't have a clue what happens at xlim.....(22mm according to eminence)

Thanks in advance, Mark
  Reply With Quote
Old 5th September 2014, 06:07 PM   #2
NEO Dan is offline NEO Dan  United States
diyAudio Member
 
NEO Dan's Avatar
 
Join Date: Jun 2008
Location: N.E. Ohio
I'll give you a clue; it starts with a clunk and ends in $ilence...
__________________
Regards,
Dan
  Reply With Quote
Old 5th September 2014, 06:17 PM   #3
diyAudio Member
 
Join Date: Nov 2005
In all designs i've ever seen the end of xlim (near published value or not) is when the coil former slams into the inside of the T plate. May as well be advised that running just below that effect will likely lead to highly accelerated suspension wear. Better to design for at least 3db below "clunk", not just a couple volts. If you don't mind the severe compression, distortion, and continuous driver replacement you'll be fine at 148vp at whatever frequency.

Last edited by Andrew Eckhardt; 5th September 2014 at 06:23 PM.
  Reply With Quote
Old 5th September 2014, 07:59 PM   #4
mark100 is offline mark100  United States
diyAudio Member
 
Join Date: Dec 2010
hmmm.....$ilence not golden !

"In all designs i've ever seen the end of xlim (near published value or not) is when the coil former slams into the inside of the T plate. May as well be advised that running just below that effect will likely lead to highly accelerated suspension wear. Better to design for at least 3db below "clunk", not just a couple volts. If you don't mind the severe compression, distortion, and continuous driver replacement you'll be fine at 148vp at whatever frequency."

Thx Andrew. Makes sense.

What gets me, is in measuring how the coil sits in the magnet, it looks like the coil would have to go about 5mm beyond the given 22mm xlim, to strike the plate!

148vpeak must be so crazy hard on the drivers. Can't afford this...

But it certainly doesn't sound compressed right below clunk....in fact a single kick drum stroke sounds about as real as I've heard (when the mains are matched right).
It sounds Wow right until clunk

Since I can't really hear distortion or compression on an impulse signal like this, is their a way to know when, or measure, that I'm pushing past xmax?

Will REW or Smaart show this?
  Reply With Quote
Old 5th September 2014, 08:09 PM   #5
sine143 is offline sine143  United States
diyAudio Member
 
Join Date: May 2010
labhorn drivers wired series or parallel?

If you set a peak limiter below "clunk" (about 100 v for a series wired labhorn) then basically you'll have a little red light that tells you "hey, we'd be smashing the backplate right now if I wasnt here, so um... turn down mkay?"
  Reply With Quote
Old 5th September 2014, 08:42 PM   #6
diyAudio Member
 
Join Date: Nov 2005
Quote:
Originally Posted by mark100 View Post
hmmm.....$ilence not golden !

What gets me, is in measuring how the coil sits in the magnet, it looks like the coil would have to go about 5mm beyond the given 22mm xlim, to strike the plate!
Good. It would be a rotten deal for interference to start 5mm below the datasheet limit. Tends to indicate that if you design below Xmax you're gonna have a good time, and that you're getting the driver you're buying. Not all drivers are actually linear out to the Xmax edges, but you Should be able to demand continuous running to that point without unreasonable wear. For this reason, Xmax spec is very handy for design. Xlim /Xmech just tells you when you're going to be buying new drivers right away.

Last edited by Andrew Eckhardt; 5th September 2014 at 08:46 PM.
  Reply With Quote
Old 5th September 2014, 08:43 PM   #7
mark100 is offline mark100  United States
diyAudio Member
 
Join Date: Dec 2010
Quote:
Originally Posted by sine143 View Post
labhorn drivers wired series or parallel?

If you set a peak limiter below "clunk" (about 100 v for a series wired labhorn) then basically you'll have a little red light that tells you "hey, we'd be smashing the backplate right now if I wasnt here, so um... turn down mkay?"
drivers are in parallel, or with an individual amp on each driver.
in either case, the amp(s) are plx 3402 in bridge mode, so I know i'm pushing the heck out of the drivers.

I'm really just trying to learn how to get the most that I can from the labhorns.
I'm willing to destroy one set of drivers if I have to; but i have 4 labhorns and can't afford not to know where the common sense (and not so common sense impulse edge is before I wail on all four.

Continuous stress seems easier to hear, certainly to measure, than a drum type impulse stress....

Last edited by mark100; 5th September 2014 at 08:47 PM.
  Reply With Quote
Old 5th September 2014, 09:11 PM   #8
diyAudio Member
 
chris661's Avatar
 
Join Date: Feb 2008
Location: Sheffield
Blog Entries: 8
You've been hitting Lab12s with 148v peaks?
Ouch. That's nearly 2kW (taking rms voltage) per driver.

I'd set your peak limiter for 140v peak out of the amplifier, which would allow some clearance for differences between drivers. Then, if possible, an rms limiter at 6-8dB below that, which should mean the drivers will stand long sustained bass notes.

Something to consider, though: "clunk" voltage at with one cabinet isn't the same as when there's 4 cabinets - FLHs load each other.. Kinda.

Chris
  Reply With Quote
Old 5th September 2014, 09:20 PM   #9
sine143 is offline sine143  United States
diyAudio Member
 
Join Date: May 2010
holy crap.... with the drivers in parallel, I wouldnt want to hit it with more than... 80v HA. 50v sustained sine can roast the coils easillllly.
  Reply With Quote
Old 5th September 2014, 09:31 PM   #10
diyAudio Member
 
oldmanaudio's Avatar
 
Join Date: Jan 2010
Location: P.A.
Why?
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Lab 12 Domino DFLH weltersys Subwoofers 16 21st September 2013 07:25 AM
Eminence Lab 12 Business running123 Subwoofers 3 12th December 2011 09:40 PM
emience lab 12 in india??????? sekhar Subwoofers 4 30th November 2010 07:43 AM
Lab 12's ? FlipC Subwoofers 0 1st October 2009 10:03 PM
amts and lab 12 motu Multi-Way 3 27th March 2005 08:29 AM


New To Site? Need Help?

All times are GMT. The time now is 11:20 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2