ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  
Pages: 1 [2] 3 4 5   Go Down

Author Topic: Push pull configuration for LAB Horn?  (Read 18225 times)

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 9010
Re: Push pull configuration for LAB Horn?Cooling question?
« Reply #10 on: July 31, 2007, 07:59:27 am »

Now that we are back on the cooling plug issue-again- what happens on the outdoor shows in the summer with a hot sun shinning on the plates?  Don't they get pretty hot just sitting there-therefore putting heat back INTO the driver with the driver acting as a heat sink for the cooling plug?

Of course if they are protected from the sun by say another cabinet, then how well do they radiate the heat by not having accesss to open air, therefore reducing the effectivness.

Were the tests done with the plugs covered up with another cabinet or laying on the ground, and not just standing out in free air?
Logged
For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

peter.golde

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 252
Re: Push pull configuration for LAB Horn?Cooling question?
« Reply #11 on: July 31, 2007, 09:42:36 am »

Ivan Beaver wrote on Tue, 31 July 2007 07:59

Now that we are back on the cooling plug issue-again- what happens on the outdoor shows in the summer with a hot sun shinning on the plates?  Don't they get pretty hot just sitting there-therefore putting heat back INTO the driver with the driver acting as a heat sink for the cooling plug?

Of course if they are protected from the sun by say another cabinet, then how well do they radiate the heat by not having accesss to open air, therefore reducing the effectivness.

Were the tests done with the plugs covered up with another cabinet or laying on the ground, and not just standing out in free air?


Interesting points about reverse heat sinking in the sun, something to think about. I lost a horn sub driver playing outside due to high winds into the horn mouth, the high air pressure at the horn mouth created very high pressure at the driver, and shattered the cone. Like reverse Bernoulli effect.
Logged
"You can't be a real country unless you have a beer and an airline. It helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer" - Frank Zappa

John Roberts {JR}

  • Newbie
  • *
  • Offline Offline
  • Posts: 0
Re: Push pull configuration for LAB Horn?Cooling question?
« Reply #12 on: July 31, 2007, 10:13:13 am »

Ivan Beaver wrote on Tue, 31 July 2007 06:59

Now that we are back on the cooling plug issue-again- what happens on the outdoor shows in the summer with a hot sun shinning on the plates?  Don't they get pretty hot just sitting there-therefore putting heat back INTO the driver with the driver acting as a heat sink for the cooling plug?

Of course if they are protected from the sun by say another cabinet, then how well do they radiate the heat by not having accesss to open air, therefore reducing the effectivness.

Were the tests done with the plugs covered up with another cabinet or laying on the ground, and not just standing out in free air?


What do you mean "we"....

Your comments are a consideration for any external heat sink, but I suspect we'll get a much longer answer.

JR
Logged
 https://www.resotune.com/


Tune it, or don't play it...
-----

Wayne Parham

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 302
Re: Push pull configuration for LAB Horn?Cooling question?
« Reply #13 on: July 31, 2007, 10:44:23 am »


Ivan Beaver wrote on Tue, 31 July 2007 06:59

Now that we are back on the cooling plug issue-again- what happens on the outdoor shows in the summer with a hot sun shinning on the plates?


We recommend a denim flap be placed over plates exposed to direct sunlight.  It can be snapped in place, and it works perfectly.  This information is included in the documentation that comes with the horns, kits and plan requests.

There is enough surface area on the plate that no real airflow is required to dissipate heat wicked out of the motor core.  But you definitely don't want sunlight heating the plates.
Logged
Wayne Parham
π Speakers
PiSpeakers.com

Wayne Parham

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 302
Re: Push pull configuration for LAB Horn?
« Reply #14 on: July 31, 2007, 11:01:52 am »


Wicking heat out of the motor core is something that has caught the attention of several loudspeaker manufacturers.  It is very effective.  In my opinion, it is as important as gap venting.

Heat radiated from the voice coil builds up in the core and is not effectively removed by venting.  It increases thermal compression, shifts electro-mechanical parameters and weakens the voice coil adhesive, often eventually causing failure.

In the example Josh gave above, (4) LABhorns without cooling plugs verses (3) 12Pi basshorns with cooling plugs, the cooling plugs give the 12Pi's the edge.  Four horns provide 2.5dB more output than three, but cooling plugs more than double the power handling, which is a 3dB increase.  Both systems will be in power compression at maximum power but the system without cooling plugs enters compression sooner and its effects are more severe.  Further, the system without cooling plugs is more prone to failure, and will likely melt the voice coil adhesive at extended sustained high power levels.  So the 12Pi has a clear advantage.
Logged
Wayne Parham
π Speakers
PiSpeakers.com

Tom Danley

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 500
Re: Push pull configuration for LAB Horn?
« Reply #15 on: July 31, 2007, 03:35:24 pm »

Hi Wayne
At the risk of triggering even more promotional posts, I hesitate to reply,  guessing (based on past exchanges) you will not read with a mind towards understanding but only towards crafting another torrent of such replies.

I found it interesting you chose to respond so extensively to the poster who’s first hand experience with both, led him to say   “I've owned both and i would take the LABs any day. They are smaller, put out the same SPL (Honestly can't notice a difference) and they are cheaper to make.”

Well lets see what the jist is here, I mean aside from his feelings that you try to talk him out of in several following posts.

The Lab IS the truck pack size the group (Here) picked and has the low cutoff the group (Here) picked.
Get the picture, it IS the size it is because that is what people wanted, it also has the low cutoff it has for the same reason and for use in a group.
I did not pick these things and it was not because I was limited to the driver at hand, I derived the parameters, specified the driver remember.

You (at the same point in time) argued against the idea of the heavy / strong driver on the AA forums.

Later, you find the LAB sub approach actually does work, but has fatal flaws that can be resolved simply by throwing away one of the main criteria and make it bigger.
You take the driver made for this job, take the same folding arrangement (with more kinks than needed) and increase its cubic Volume.
You find with the increased size at one Watt you can get what, a dB more in some places, dang, that is like… radical dude.

With your plugs you claim to raise the power handing 225%
You might have been able to find a condition where this might be true, to suggest that this is true in use with music or in general use is disingenuous as I would bet you did not measure the electro acoustic efficiency of a group of labs to a group of Pi’s or under power with music in actual use.
You larger compliance volume (which I see you have addressed with a retro fit filler plug) did smooth the response for one box, at the cost of more excursion for a given power.

Under the right conditions, your plugs would help too, but so do the aluminum plates already used in the lab sub, those get hot too.       Unlike your plugs, there was no claim made about how much the unusual aluminum cover plates helped, only that they do a little compared to wood.
While the aluminum cover plates transfer heat out of the chamber and driver, to the out side world, that is conditional on how they are used and most sound folks know you can still blow a driver even with a cool magnet
The more dynamic the source, the less likely the magnet temperature will reflect the instantaneous VC temp.
Heck, on most of my Tapped horns, the drivers are fully out in the open, mounted  “where the air is really moving” but I don’t claim any increase in PHC over normal.

So far as the push pull part, it is generally not considered worth the effort and other things are so much stronger factors in measured results.
In particular, the lab sub’s “strong heavy driver” in a small back volume (ala Servodrive alignment) which at the time was fully contrary to the “W bin” light cone / big volume horn lore of the day, when combined with a linear motor, produces much less distortion and much more acoustic power than those “old school” horn driver alignments.

Here too, I would bet you did not actually measure a group of LABs side by side with your Pi’s.  You might well be pleased with how low in distortion your Pi’s measure, but so are the owners of the Labs subs, they are also lower than most everything out there.

Lastly since your spinning your pitch off the lab sub as the main reference, build, instrument and (fairly) measure a few side by side.
Even better, to get an actual perspective, compare it and yours to the big money / big loudspeaker names people have been buying for the last 10 years.
In addition to something cool to build, instead of more W bins,  part of the point of the lab sub project was to expose how lame some “well-respected” and costly products actually were, a fact only visible when measured or exposed in side by sides.
While the Lab sub is a mature project now and there are many new subwoofers out there, it still holds up very well.

Cheers,
Tom Danley

Logged

Wayne Parham

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 302
Re: Push pull configuration for LAB Horn?
« Reply #16 on: July 31, 2007, 04:50:43 pm »


Josh said the 12Pi was slightly louder than the LABhorn and that he was happy with its performance.  But he also said he prefered LABhorns because they were easier to build, smaller and cheaper.  He went on to say he preferred JBL SRX-728S dual 18's to LABhorns.  That's fair;  He is doing indoor gigs.

The 12Pi basshorn has been extensively tested and it does exactly what I say it does.  It's not like it is just some hypothetical design on paper.

I posted to clarify a few things, because I though Josh's initial comments gave the wrong picture of some technical details.  There's no need to rehash;  My comments are shown above in this thread.

The cooling plug is something that can be added to LABhorns.  That way they can benefit from improved cooling just the same as the 12Pi's.  People can make their own or they can buy them.  Without a cooling plug, there is no conduction path to the access plate so it is ineffective as a heat sink.  The whole point of discussing things like this here is so people can learn things to take advantage of and make their sound systems better.

The LABhorn size was chosen by the group, and so had a size contraint.  That's fine.  I wasn't involved with that and have no complaint.  I also have no complaint with the driver chosen.  The whole issue of heavy verses light cones or Keele verses Leech is an argument you have had with others.

My argument with you regarding the LABhorn was with your suggestion to use it well under cutoff for hifi systems.  I said that if you use a 30Hz basshorn down to 16Hz, you're really just making a distortion amplifier.  At 16Hz, a LABhorn is unloaded and is just a direct radiator in an undersized sealed box.  The fundamental isn't loud at all because neither the sealed rear chamber or the horn pathway are tuned for it.  But the second and third harmonic is presented to the horn and amplified by it.

If the LABhorn used push-pull drive, that would help a lot to reduce distortion below cutoff.  I don't know that I would suggest using it below cutoff for other reasons, but at least you would have the distortion cancelling effects provided by the push-pull configuration.

By the way, will you be bringing any subwoofers to the Prosound Shootout in October?  We'd hate to miss you there a third year.
Logged
Wayne Parham
π Speakers
PiSpeakers.com

Josh Billings

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 949
    • http://www.mindboxmedia.com/soundsystem
Re: Push pull configuration for LAB Horn?
« Reply #17 on: July 31, 2007, 07:04:53 pm »

I'd really love to see some TH-115s & Original LAB Subwoofers against the 12pis actually Smile

-Josh
Logged

Pascal Pincosy

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 978
Re: Push pull configuration for LAB Horn?
« Reply #18 on: July 31, 2007, 07:08:37 pm »

Josh Billings wrote on Wed, 01 August 2007 00:04

I'd really love to see some TH-115s & Original LAB Subwoofers against the 12pis actually Smile

-Josh


+1

Pascal
Logged
Know:Audio
--------------------------------
US Distributor: Trabes/MG Srl
Speaker Lifts-Truss-Roof Systems

Wayne Parham

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 302
Re: Push pull configuration for LAB Horn?
« Reply #19 on: July 31, 2007, 09:14:40 pm »


Josh Billings wrote on Tue, 31 July 2007 18:04

I'd really love to see some TH-115s & Original LAB Subwoofers against the 12pis actually Smile

-Josh


Me too.

Honestly, it should be a very nice time.  A bunch of winners come to these things and a great time is had by all.  Pretty much all the gear represented is great and the people there are super good folks.
Logged
Wayne Parham
π Speakers
PiSpeakers.com

Pages: 1 [2] 3 4 5   Go Up
 

Page created in 0.078 seconds with 21 queries.