ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1] 2  All   Go Down

Author Topic: Lab Sub help  (Read 3424 times)

Travis.Riddle

  • Newbie
  • *
  • Offline Offline
  • Posts: 4
Lab Sub help
« on: February 17, 2018, 05:19:06 pm »

OK so I have been scouring the forum for a few days looking at all the drawings and specs. I am a Technical Director for a large church part time and I have been a carpenter my whole life. I want to build my first set of labs but I want to do it correctly. Is there anyone close to the East Texas area that way want to assist me in this endeavor that has previous experience?
Logged

Roland Clarke

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 741
Re: Lab Sub help
« Reply #1 on: February 18, 2018, 04:39:57 am »

OK so I have been scouring the forum for a few days looking at all the drawings and specs. I am a Technical Director for a large church part time and I have been a carpenter my whole life. I want to build my first set of labs but I want to do it correctly. Is there anyone close to the East Texas area that way want to assist me in this endeavor that has previous experience?

There is a link to the complete documentation above.  If you’ve been a carpenter all your life you should have no difficulty as many amateurs have managed successful builds.
Logged

Phil Graham

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 66
Re: Lab Sub help
« Reply #2 on: February 19, 2018, 09:09:50 am »

OK so I have been scouring the forum for a few days looking at all the drawings and specs. I am a Technical Director for a large church part time and I have been a carpenter my whole life...

Travis,

As Roland mentioned, documentation is above.

That said, a lot has changed since the original LAB sub in the world of drivers, and the LABs are a lot of work and size relative to the output levels.

If you want a fairly high complexity build with much better performance in the same vein, there is a guy named Art Welter, who I assume is still around here, that has a re-entrant horn design.

Otherwise comparatively simple vented boxes may be the way to go.

What are you hoping to achieve in the end?
Logged

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1515
Re: Lab Sub help
« Reply #3 on: February 19, 2018, 07:12:57 pm »

If you want a fairly high complexity build with much better performance in the same vein, there is a guy named Art Welter, who I assume is still around here, that has a re-entrant horn design.
Yeah Phil, still around here ;^). Hope all is well with you and yours!
Back when I was your age (and years younger...), a "re-entrant horn" was specifically (and only) used as a common name for a folded "PA" horn used for "speech" frequencies. A "re-entrant horn" typically used a thread-on compression driver, though later versions often built the compression driver in to the horn assembly itself.

My Keystone Sub design, which you are likely referencing above, is now commonly known as a Tapped Horn. The TH is a folded horn which has one side of the driver located near the throat and the other near the mouth, and has no sealed compression chamber.

This type of horn goes back at least as far as 1955 (William E.Glen "Acoustic Horn Assembly" patent #2,765,864) though the designation of "TH" was made by Tom Danley, who updated and began to commercialize the concept and then donated the LabSub FLH (folded Front Loaded Horn with sealed compression chamber) design here back around the turn of the century.

Cheers,
Art
Logged

Rick Powell

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 764
Re: Lab Sub help
« Reply #4 on: February 19, 2018, 09:26:29 pm »

I wouldn’t call the Keystone a complex build. Lots less pieces than the LAB sub, and not much harder to build than a vented box. And it weighs a lot less than a LAB sub, too.
Logged

Chris Grimshaw

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1038
  • Sheffield, UK
    • Grimshaw Audio
Re: Lab Sub help
« Reply #5 on: February 20, 2018, 03:42:17 am »

I wouldn’t call the Keystone a complex build. Lots less pieces than the LAB sub, and not much harder to build than a vented box. And it weighs a lot less than a LAB sub, too.

... And loaded with the recommended B&C driver, would likely show much better performance under long-term high-power conditions.
THs get the driver's motor right next to the air flow, which really helps power compression. The LABSub has the drivers (which aren't great at thermal management to start with) in small sealed chambers so all the heat pretty much just stays there.

Chris
Logged
Sheffield-based sound engineering.
www.grimshawaudio.com

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 19979
  • Wichita, Kansas USA
Re: Lab Sub help
« Reply #6 on: February 20, 2018, 03:23:10 pm »

... And loaded with the recommended B&C driver, would likely show much better performance under long-term high-power conditions.
THs get the driver's motor right next to the air flow, which really helps power compression. The LABSub has the drivers (which aren't great at thermal management to start with) in small sealed chambers so all the heat pretty much just stays there.

Chris

At the NYC Sub Shootout in 2007 we heard a Franken-LAB (same mouth area, slightly shallower construction -a transport requirement for the owner- and NO speaker access covers).  It wasn't as compromised as most of us thought it would be but I don't think we did a TEF sweep because of the modified design.  The amount of heat generated during our listening was obvious without the covers.

Two days of listening to subs without tops to "reference" was actually quite revealing.  Our audition & gray matter processing infers and integrates a lot of things in full range listening that are perceived very differently when auditioning individual pass bands.
Logged
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Mark Wilkinson

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 862
Re: Lab Sub help
« Reply #7 on: February 20, 2018, 08:03:00 pm »

At the NYC Sub Shootout in 2007 we heard a Franken-LAB (same mouth area, slightly shallower construction -a transport requirement for the owner- and NO speaker access covers).  It wasn't as compromised as most of us thought it would be but I don't think we did a TEF sweep because of the modified design.  The amount of heat generated during our listening was obvious without the covers.

Two days of listening to subs without tops to "reference" was actually quite revealing.  Our audition & gray matter processing infers and integrates a lot of things in full range listening that are perceived very differently when auditioning individual pass bands.

That is funny !!!
Some guy actually built labhorns with NO rear covers  ?  Wow.. and they still made OK sound...wow..

Who knows what impedance that made.... at any freq...could have been near toaster oven Rdc, thru whole range lol...or not?

I really don't know what to make about labhorns vs today's offerings.
I built 4 by the original plans, pretty carefully. 
When i test them against the modern subs I have, orbitshifters, and a pair of DIY BMS 18"s,  it's hard not to give the labsubs the nod.  Against the OS, Labs are 3db more efficient, have smoother response, and go a little lower. But the OS does handle at least twice the power. Against the BMS 18"s, the labs are more efficient, but otherwise the pair of BMS rules.
Then I look at another highely regarded alternative, the TH-118. Doesn't seem any more efficient than the labsub, however, like the OS, it handles twice the power.  But phase is mixed up...inherent to tapped horns I think...

I've heard about the heating/compression problem with labhorns, but i didn't see any of that on a handful of gigs with them last summer. 
Maybe folks either pound them past reason, cause they stay clean sounding, or use a too high a freq low pass filter. Impedance says they will burn up quicker used over 95Hz than below I think.....
I wish i could get a true read on the heating prob, if there is one...

Because I'm in the middle of re-plotting subs.  Just built a boatload of mid-high capability, and need to build/buy subs to catch up.

I might actually end up building more labhorns,

 ...or building some DIY TH's or keystones,...or building more of the single BMS 18" BR's I that i REALLY like, .....or maybe even  buying TH-118s or OS's for resale value.
 
I need to get to at least an 8-10 labsub rig...will  restart from scratch if need be..damnit :)

Logged

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 8763
  • Atlanta GA
Re: Lab Sub help
« Reply #8 on: February 20, 2018, 09:01:52 pm »

That is funny !!!
Some guy actually built labhorns with NO rear covers  ?  Wow.. and they still made OK sound...wow..


Well they did "kinda" have covers.

The covers were just speaker carpet over the holes.

Better than nothing-but not much.
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Mark Wilkinson

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 862
Re: Lab Sub help
« Reply #9 on: February 21, 2018, 09:21:37 am »

Well they did "kinda" have covers.

The covers were just speaker carpet over the holes.

Better than nothing-but not much.

Maybe the guy was really precocious.....I mean, he sort of invented a "tapped (lab)horn"  ;D
Logged
Pages: [1] 2  All   Go Up
 


Page created in 0.037 seconds with 21 queries.