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Author Topic: Converting passive cabs to active  (Read 3457 times)

Vic Turner

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Converting passive cabs to active
« on: April 22, 2004, 11:21:10 PM »

We are currently upgrading our cabs. We like the YamahaS115IV club series 15's w/ Emenence speakers. The price is right, 500RMS won't break our bank to get an amp to power it and still has a good punch for small to midsize venues. But it's a passive cab. My question is first off can you run an active X over into a passive cab? How would you modify a cab from passive to active and still allow the cab to be daisy chained to be ran at 4ohms? And can this cab be used like that, does anyone foresee any problems? Thanks
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Tim Padrick

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Re: Converting passive cabs to active
« Reply #1 on: April 23, 2004, 05:40:10 AM »

To convert the speaker to active, the crossover must be completely disconnected from the input and from the drivers.  If anything is left connected, it will load the amplifiers in an undesireable manner.

The speaker should be converted from 1/4" to Speakon NL4s when going active.  This prevents it from being connected wrongly during setup, and allows easier daisy chaining (although it would be better to run separate cables from the amp rack to each cabinet.  (And 1/4" just suck.)

Modding the cabinets and tuning the active crossover is not a project for the inexperienced.  I'd use the cabinets passive - they sound pretty good - a little lacking in the upper mids, but pretty good.  Use one side of a PLX3402 or RMX4050 to drive them, and use the other side for monitors or a sub.  (Or, you could drive them with a bridged PLX1202, PLX1602, or RMX1450.)

If you are going to be using subs right away, look into the JBL MP412, it's a very nice sounding box.

Vic Turner

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Re: Converting passive cabs to active
« Reply #2 on: April 23, 2004, 03:51:35 PM »

Thanks TimmyP,

So just to make sure we can run a X over into a passive cab no prob right? So what you are saying is that it really isn't worth it to convert that cab to a Bi amped beast, would the sound be any improved? Why would it be better to run seperate cables from the amp rack to the speakers? We have Behrenger1800 18's now and a Nady 2400 for our subs. Thanks again.
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Vic Turner

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Re: Converting passive cabs to active
« Reply #3 on: April 23, 2004, 07:23:46 PM »

I should also mention, we are purchasing a Dbx Driverack X over. This is why we are wanting to Bi amp our system.
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Andy Peters

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Re: Converting passive cabs to active
« Reply #4 on: April 24, 2004, 04:32:31 PM »

[quote title=Motown wrote on Fri, 23 April 2004 12:51]So just to make sure we can run a X over into a passive cab no prob right? So what you are saying is that it really isn't worth it to convert that cab to a Bi amped beast, would the sound be any improved?

I read your post the following way, and I apologize if I'm getting it wrong.  Seems to me that you want to feed your power amp's output into your active crossover INPUT, and then take the active crossover's outputs and run them to the cabinet.

I realize that the questions I'm about to ask are somewhat ridiculous, but I think they need to be asked:

Do you realize that you CANNOT simply run the active crossover output into the biamped cabinet's input?

You do realize that to power your biamped cabinets, you need TWO power amps, one for each driver in the cabinet?  You also need a third power amp for your subs.

Quote:

 Why would it be better to run seperate cables from the amp rack to the speakers?


Well, a practical reason is that if the cable from the amplifier output to the first cabinet in the daisy chain were to fail, then ALL of the cabinets turn off.  If you have a separate home run for each cabinet, then losing one of these home runs doesn't kill every speaker on the chain.

In reality, however, the daisy chain is just fine -- you don't need as much cable, and how often does a speaker cable get disconnected, anyways?  Consider also the case where somebody runs over the speaker cable with a truck, or something -- it's likely that all wires bundled together will be damaged, or perhaps one wire will get cut, and cause a short, which causes the amp to shut down, so you STILL lose all cabinets on that amp channel.

There may be some tweaky answers having to do with amplifier damping factor and other esoterica, but suffice it to say the daisy chain works fine, as long as you don't exceed the amp's maximum loading.

--a
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Bill Horn

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Re: Converting passive cabs to active
« Reply #5 on: April 25, 2004, 12:03:14 PM »

In my opinion, I'd keep bi-amping the tops an option for later, but you've got too many other things to do getting your PA together to consider it now.

I think getting rid of passive crossovers, even in club cabs, is a good idea if they're being used at anything above moderate volume levels. The harshness associated with pushing 1" HF drivrs is diminished considerably when passive components are removed. We're currently using four tops consisting of Eminence Delta 15's and PSD-2002's for drivers, and when we went active the difference was very audible. I've done this several times in the past with other cabs, and never been sorry. All advice from TimmyP and Andy Peters apply...use NL-4 Speakons and have someone help set it up if you're unsure af what you're doing.
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Vic Turner

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Re: Converting passive cabs to active
« Reply #6 on: April 26, 2004, 07:53:31 PM »

Thanks gentleman,

Yes, I am aware of those things you mentioned Andy. Bill you just reinforced our decision. It's going to be sweet when we are done. We always make things harder on ourselves, but I think it's worth doing if it sounds better. I know our audiance will enjoy it. Thanks again everyone, I may you help when I get all this stuff and we start putting it all together. You guys rock!
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