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Lab horn USB crossover and general advice

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Category: General
Forum Name: Advanced Discussion
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URL: https://forum.speakerplans.com/forum_posts.asp?TID=98149
Printed Date: 29 March 2024 at 12:40pm
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Topic: Lab horn USB crossover and general advice
Posted By: Kieranearth
Subject: Lab horn USB crossover and general advice
Date Posted: 26 March 2017 at 2:01pm
Right I've just prurchased 5 lab horns(eminiamce lab loaded), 2 USBs with celestion Ftr's, and a turbo tms4. I've got a couple questions. Basically at the moment I want to use 4 labs one USB and get some different tops to go on top (recommendations would be handy), so am I right thinkikg that I should cross the labs from 30-80 and the USBs 80-180) or the drop from the tops. I'm also not sure how the impudence would work, they are 6oms drivers wired in parallel so that's 3ohms a cab and could wire them in series parallel to an amp to get a 3ohms load 2 cabs a channel. Is that correct? And will most amps run 3ohms? Should probably add that I'm probably going to get 8 or 12 labs in total to sit under the 2 USBs, what would be good for the top end?
Thanks



Replies:
Posted By: snowflake
Date Posted: 26 March 2017 at 7:12pm
tms4 doesn't need subs and kicks below it. forget about the USBs.

labs are designed to be a four ohm box - impedance is greater than the dc resistance.


Posted By: Mark James
Date Posted: 26 March 2017 at 10:54pm
series parralel would be 6 ohm load not taking into account what the horn may add.
so youd have between 6<8 ohms if you series parralel 2 cabs [4 drivers series parralel]
30-80 labs and 80-180 with the usb would be about right I should think.....
if your going to ha ve 8 labs you will need more than 2 usb i would think
as for tops..... flood light ? seems a combo people have been using a fair bit.....



-------------
me so horny me love you long throw
horn loaded for her pleasure


Posted By: Kieranearth
Date Posted: 26 March 2017 at 11:14pm
yes the tms4 are full range but I am going to get some dedicated tops to match the power of the bottom end. The USBs are 2000rms a cab so I don't think I'll need more, and on the tops I was thinking xtro's


Posted By: Kieranearth
Date Posted: 26 March 2017 at 11:17pm
What do you mean labs are designed to be a 4 ohm box? How could this be when the drivers are 6ohm and there are two In the cab?


Posted By: toastyghost
Date Posted: 27 March 2017 at 12:08am
Nominal impedance of a driver in free air is not the same as that driver loaded in a box. It's also a curve that varies with frequency not a fixed number. You should ideally measure the impedance plot of a loaded box. It isn't hard to do with REW and a resistor there's a guide here even


Posted By: Kieranearth
Date Posted: 27 March 2017 at 12:35am
I understand that the impemdence will be different loaded into the box, I don't quite understand what you mean there working out the Impendance plot but if you could link me to the post I'd appriecate that and can then educate myself. Been looked for the specs of the cabs loaded on ProSoundWeb but I just can't seem to find any.
Thanks for your advice,


Posted By: toastyghost
Date Posted: 27 March 2017 at 12:49am
There's some simulations here
http://audioroundtable.com/PiSpeakers/messages/17389.html" rel="nofollow - http://audioroundtable.com/PiSpeakers/messages/17389.html


Posted By: Kieranearth
Date Posted: 27 March 2017 at 2:53am
Thanks mate I apreachate that, I'll have to look into it all when I've got a bit of time.


Posted By: snowflake
Date Posted: 27 March 2017 at 1:11pm
"What do you mean labs are designed to be a 4 ohm box?"

literally that. the lab horn was designed by Tom Danley with input from people at ProSoundWeb. They wanted a 4ohm nominal impedance box, the horn and driver paramaters (including Re) were then calculated to give a 4 ohm box, and then Eminence were asked to produce a driver with those specs.

Re is not the same as impedance whether driver is in a box or not.

http://leachlegacy.ece.gatech.edu/papers/HornPaper/HornPaper.pdf" rel="nofollow - http://leachlegacy.ece.gatech.edu/papers/HornPaper/HornPaper.pdf


Posted By: Kieranearth
Date Posted: 27 March 2017 at 6:46pm
Thanks i didn't realise the cab could make such a difference in resistance but I've saved that paper thanks.


Posted By: gen0me
Date Posted: 27 March 2017 at 8:49pm
Sorry to disappoint you.

Thats from above page simulation.


Posted By: snowflake
Date Posted: 27 March 2017 at 11:28pm
it's designed to be used in stacks of six which raises the impedance minimum slightly. most speakers have minimum impedance dips below the nominal impedance. the labhorn impedance is high enough to treat the box as a 4 ohm load for amplifiers in the band of operation 28Hz-100Hz.

that Tom Danley isn't a wally Wink


Posted By: gen0me
Date Posted: 28 March 2017 at 5:10am
Thats why I pasted imp curve for 4. To lose all doubts. This horn gets even worse than usually. It has second valley so low.
Didnt read it all but impedance in horns just has this valleys. And they are worse than in brs or open air. Its just not true!
I recommend 3 speakers on 2ohm channel.


Posted By: snowflake
Date Posted: 28 March 2017 at 8:53am
how could a driver possibly have lower impedance loaded in a box than in free air?

as someone who has built and operated labhorns (as well as reading all the design process documentation and the Marshall Leach paper) this is not a real problem. they operate as 4R boxes.


Posted By: tv00
Date Posted: 28 March 2017 at 9:25am
BPH also has this, a stack of 6 of mine are above 2 ohm impedance from 34-160hz


-------------
www.facebook.com/babysoundsystem


Posted By: gen0me
Date Posted: 28 March 2017 at 6:12pm
Originally posted by snowflake snowflake wrote:

how could a driver possibly have lower impedance loaded in a box than in free air?

Originally posted by gen0me gen0me wrote:




2ยท2.27ohm<5ohm
You can clearly see on documentation (http://www.eminence.com/pdf/LAB_12.pdf) that free air impedance is higher than 5 ohm


Posted By: snowflake
Date Posted: 29 March 2017 at 8:05pm
well you are comparing apples and pears. simulate the lab12 driver in free air in hornresp and you will see it gives a minimum impedance of 4.33 ohms - less than the 5.26 ohms per driver when loaded on the horn. maybe that graph is wrong, or scale is in dbohms rather than ohms or something


Posted By: gen0me
Date Posted: 29 March 2017 at 11:38pm

Right. Looks like they added something in measurements...Ouch
Nice one!Embarrassed



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