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Author Topic: newbie question for powering a pair of labs in a single cabinet for a Home Theater  (Read 5356 times)

Al

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I'm a newbie to the lab 12 but not to speakers or electronics in general...

I am considering a single cabinet(dual driver) system to fill out the bass for a home theater application.

What kind of setup is normally used to power the 2 drivers in a signal cabinet? i.e. A mono amplifier connected to both speakers in parallel, a pair of amplifiers each driving a single speaker in phase with the other...?

Would a 500w sub amplifier (such as available from Parts Express) work for these in this environment, or could I get away with a discreet 120w(RMS)/ch stereo amp...

The theater room is 16x26 feet so I would expect that the efficiency of the horn loaded enclosure would make for modest power requirements.

Thanks for your input and views!

Al
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Al

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Re: newbie question for powering a pair of labs in a single cabinet
« Reply #1 on: September 06, 2004, 11:02:04 am »

Hey guy's this is a genuine question, any takers?

Al
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Mac Kerr

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Re: newbie question for powering a pair of labs in a single cabinet
« Reply #2 on: September 06, 2004, 12:38:55 pm »

You don't mention if the speaker cabinet you are intending to build is in fact the LAB Sub that this forum relates to. the Lab12 driver was developed to work in this particular horn enclosure. The power handling may suffer if used in an enclosure that does not properly load the driver. The normal way to power these drivers is 2 of them on an amp channel, or i per amp channel. Because of the low impedance of the driver it is not wise to have more than 2 on an amp channel. Even with only 2 per channel you must have an amp capable of driving low impedance loads. A normal Hi-Fi type amp would not normally be capable of this.

Mac
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kevinnemrava

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Re: newbie question for powering a pair of labs in a single cabinet
« Reply #3 on: September 06, 2004, 12:40:52 pm »

some time is takes some time to get solution to question.


well first off most of the guys here are useing them for live sound.

HOWEVER I can't remeber who, but someone is use 2 labs, and SPL stuff to build a home theater. looks to be very promising.

Due to the horn design the effecency is way up there, so power wise, I would think 500 watts for home theater would be fine. you can power them how ever you want, how ever I would be carefull to make sure that you amp is reasonabley flat, sometimes "consumer" amps real start to tank in the low end.

one thing that may or may not work for you is to look in your local used "bargin finder" and see if there are any cheap Pro level amps.


Also I imagine you know this but you can really later teh sound of the sub basedon where you place it in the room , so put some thought in to that.

Kevin Nemrava
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Al

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Re: newbie question for powering a pair of labs in a single cabinet
« Reply #4 on: September 06, 2004, 01:03:36 pm »

Thanks, now we are off to a start! I know that most applications here are for live sound, but there is plenty of mention of home use too.  Smile

As for the enclosure, I planned to build the horn enclosure as profiled on ths forum.

As for placement in the room, that is very flexible at this point as I am building it with the home theater in mind and speaker placement (and screen) are the reason this room is being built, no compromises should be necessary!

I apologize for the lack of information in the original post, I have all of the details in my mind and I forget to share them when I type out the questions.

So, now back to driving these guys, given that there are 2 drivers in a single cabinet, each with a nominal 8 ohm impedance: For a home theater application would the best setup be a single amp channel for each driver? And should each driver see the same relative signal (i.e. in phase mono) or ?
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Mike MacWillie

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the LAB12's are actually 6 ohm drivers.. so if you use a single chanel amp, you're going to need one that's stable to atleast 3 ohms. THat's not too common for a home audio amp..
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Al

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Michael M wrote on Mon, 06 September 2004 11:04

the LAB12's are actually 6 ohm drivers.. so if you use a single chanel amp, you're going to need one that's stable to atleast 3 ohms. THat's not too common for a home audio amp..


So your suggesting that the drivers get wired in parallel, rather then one driver per channel?
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Mike MacWillie

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I was suggesting that you can go either way. If you parallel them, you will need an amp capable of driving a 3 ohm load. If you run one driver per chanel, then most any home amp will do.  
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Al

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Michael M wrote on Mon, 06 September 2004 13:51

I was suggesting that you can go either way. If you parallel them, you will need an amp capable of driving a 3 ohm load. If you run one driver per chanel, then most any home amp will do.  



That's good news! I have a 120w/ch stereo amp that I would like to try with this setup, either that or buy a couple of dedicated sub amplifiers...(i.e. Parts Express)

So my other question was about what signal to send to the pair of speakers?

Would you supply a mono signal to both, in phase or an in phase signal to one and out of phase to the other?

Al
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Mike MacWillie

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You'd send the same signal to both drivers.
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Dave Rickard

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Also consider the problem of delay due to the length of the horn.  In live sound, you delay the tops to match the subs.  The PE amps won't delay the tops like a DSP crossover.  

I would post a question on the PE tech talk page about a 3 ohm load.  Direct your question to Darren.

daver
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Dave
Yorkville dealer

"The wrong piece of gear, at the right price, is still the wrong piece of gear."

"If you don't have good stuff at each end of the signal chain, (mics and speakers) what you use in between is just turd polish."--Dave Dermont

Al

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daver wrote on Thu, 09 September 2004 21:33

Also consider the problem of delay due to the length of the horn.  In live sound, you delay the tops to match the subs.  The PE amps won't delay the tops like a DSP crossover.  

I would post a question on the PE tech talk page about a 3 ohm load.  Direct your question to Darren.

daver


As for the load, I think that I would stick to one driver per channel.

Delay, Hmmmm, I'l have to see if the DSP section I have will allow or compensate for the delay out of a horn loaded sub.

Any idea what kind of delay time we are talking about?

Al
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Phil Pope

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you should delay the tops about 8ms.  alternatively if you have no delay section you could have your crossover point at about 130Hz (c/horn length, 340m/s / 2.8m).  This would mean that although the signal from the subs is not in time with the tops it is exactly one wavelength out at the crossover frequency and therefore still in phase at the frequencies where there is output from both speakers.  You may just be able to detect that the subs are slightly behind the tops but at least you will not have a dip in response at the crossover frequency.

Phil
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Tim Padrick

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If I were using LABs in a home situation, I'd use a Crown K1 or K2, which ever I could find at the right price on eBay.  For PA, I'd use a Bridged K2 per box, or a stereo CE4000 (one chennel per driver).

Dave Junius

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I believe that your answer is yes. You would not want to wire up the drivers in the push-pull method that many car-audio iso-baric bandpass boxes are built with speakers in a clamshell configuration.

Dave in ATL
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