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Author Topic: Proper wiring of labs for 2 boxes per channel  (Read 3313 times)

Marty Bilecki

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Proper wiring of labs for 2 boxes per channel
« on: May 24, 2004, 10:59:42 pm »

 I'm lost as to properly wire a lab for 2 subs on 1 macro 5000 channel...  My thinking has 2 4 ohm speakers in parallel at 2 ohms per box...    Series wiring of 2 lab 12's inside 1 sub = 8 ohms and then 2 boxes is a 4 ohm load per channel....  What am I missing here??   I'm still lost after searhing the archives...  thanks in advance  Marty B  
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 Martin J. Bilecki
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Timmahh

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Re: Proper wiring of labs for 2 boxes per channel
« Reply #1 on: May 24, 2004, 11:26:28 pm »

1st,   the Lab Gen II driver is 6 ohm driver, NOT 8.  2 per box wired in parallel = a 3 ohm load per cabinet... if you put them both toghether in parellel to be run on one side of any amp, you ohm load is now 1.5... Most amps cannot take this ohm load.  That being said, some can.  I am unsure of the perticular crown your speaking of. but some crowns are rated to 1 ohm loads.  
If you truely wanted to use one side of an amp, ( i wouldnt do it ) to power a pair of labs, then you ll want to wire each cab internally parellel to see a 3 ohm load per cab, then wire both cabs together in series, therefore  your amp will now see a 6ohm load. again I wouldnt do it. check the speaker wire terminals with an ohm meter to be sure you have the rating your looking for...
I would wire both cabs normally, and power each with one side of the crown amp... then all is decent in lowsville!!!. but to each his own, maybe someone with more knowledge with this crown amp can give you the proper ohm capibilities of the amp...

That being said, I read somewhere in the archives that most amps see approximatly a 4-5 ohm load per cab, becuase of the freqs being used.   but its been a while since i read it, and things may be a bit different than my tired melon recalls.  Anyone else have input on this?
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Marty Bilecki

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Re: Proper wiring of labs for 2 boxes per channel
« Reply #2 on: May 24, 2004, 11:42:25 pm »

 thanks  I'll keep digging in.... All of the current inventory of lab 12's does not seem to be gen 2    
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 Martin J. Bilecki
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Marty Bilecki

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Re: Proper wiring of labs for 2 boxes per channel
« Reply #3 on: May 24, 2004, 11:56:46 pm »

 Me bad  I had 4 ohms per speaker in my head   6 is correct....

 But still 3 ohms per lab and 1.5 with 2 parallel

marty b
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 Martin J. Bilecki
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Sound Construction

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Re: Proper wiring of labs for 2 boxes per channel
« Reply #4 on: May 25, 2004, 01:11:27 am »

remember also that ohm draw is frequency dependant. the ohm rating of a driver was measured based on a specific frequency. (not displayed anywhere for the Lab12 that i can see) the lower the frequency the lower the ohm draw. this can very easily drive an amp into fractions of an ohm range when its driving a bunch of subwoofers.

I have gone so far as to wire my EAW sb528's (dual front loaded 18's) so that each of the drivers sees one side of a Crest CA9. Each side of the amp only sees 8ohms. Snappiest 18" subs i've ever heard. (higher impedence also results in faster transient response, or... tighter bass!) Anybody know how this principal would apply in a horn loaded sub like the Lab?
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Al Limberg

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Re: Proper wiring of labs for 2 boxes per channel
« Reply #5 on: May 25, 2004, 09:49:58 am »

Hi Marty,
First off, Eminence has never sold anything but GenII Lab12s. The 'GenI' was the original prototype made for Tom Danley to test the cabinet design.  After testing, Tom made a few changes in the parameters and the GenII was born.   As far as amp loading goes, I suspect different amps will react in different ways dependent on their performance.  As stated in other replies, 3 ohms is the nominal impedance and and is not necessarily representative of the load presented to the amp.  Impedance does vary with frequency and it also varies with the number of LabSubs stacked together.  A single cabinet will display a minimum impedance of the 3 ohm rated impedance with peaks well above 10 ohms.  As you approach the recommended number of Labs (ideally an array of 4 or even 6) the impedance curve becomes smoother and more consistant.  For the original subwoofer shootout, we ran 4 Labs off a QSC PL9.0 for hours on end with no problem whatsoever.  At various times during the day, we did the same with a Macro 3600 and a Crest 10001;  all performed just fine, altho there were audible differences in the sound that the entire group felt were noticeable. (Then again, perhaps it was mass hysteria - we'll have to read Bink's amp shootout results to judge Wink)   Judging from the impedance curve of a Lab cabinet versus others on the market and allowing for a little 'Kentucky windage', I would call the Lab a 4 or 5 ohm cabinet with a 3 ohm minimum.

HTH,
Al
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Sound Construction

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Re: Proper wiring of labs for 2 boxes per channel
« Reply #6 on: May 26, 2004, 01:26:13 am »

Hey Marty, I might be missing a few things in my understanding of impedence, help me out. The way I have learned it is if you put two 8ohm drivers on a single channel of an amp, you presen the amp with a 4ohm load. double that with a similarly loaded dual driver cabinet and the amp will see a 2ohm load based on the drivers nominal impedence. At frequencies lower than the one used to measure the drivers nominal impedence, the draw ohm draw on the amp lowers. The higher the ohm draw is on the amp the lower the wattage it will put out, but the more control it will have over the driver resulting in a tighter response from the cabinet.

Accoustic loading aside, is the above principal accurate. I've heard the results by comparing same cabinets and amps in different configs, but my understanding of the "why" could use some sharpening.

And then of course, beyond what you have already explained, how does this relate to the Labs?
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