#1940456 - 05/10/08 11:12 PM
Clean Headroom with PLX3002 and Acme B2
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BenHack
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Hi Guys
I need some amp advice so here's the situation. I have a PLX3002 and an Avalon U5 driving an Acme B2. So that's 900 W into the cab. I get amazing tone but I'm running out of headroom. Most of my gigs are medium sized clubs but I can't always rely on PA support and have a loud drummer to contend with. I often run into headroom (clipping) problems when using effects or slapping.
So I was wondering what makes most sense. Buy another 4 ohm Acme B2 and run 900 w per side (like Alex did) or get 2 8 Ohm cabs and run them bridged at 3000w? Also just to make sure,should I be driving the power amp with the line or mic level from the U5? I love my tone but I don't want to blow anything up. Any help or advice is appreciated. Cheers
Ben
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#1940487 - 05/11/08 02:55 AM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: BenHack]
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DavidMPires
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Sorry I don't mean to hijack the thread, I have a B2 myself, what you mean by running out of headroom, I never understood that.
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#1940500 - 05/11/08 05:04 AM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: DavidMPires]
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BenHack
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I guess what I mean by running out of headroom is that I am overdriving the input to the poweramp with a heavy attack eg a pop. This causes the poweramp to deliver its full power to the speaker which results in a distorted sound that could lead to speaker damage. Perhaps this isn't the strict definition of 'running out of headroom'. I just know I don't want to blow my speakers up and I'm pretty sure I can get a lot more volume out of them somehow or other. Cheers
Ben
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#1940507 - 05/11/08 05:35 AM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: BenHack]
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Rocky MacDougall
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My limited knowledge of this subject leads me to believe that a speaker is capable, through its design, to produce a maximum SPL
(sound pressure level) and it needs a certain amount of power (wattage) to accomplish this. If you increase the power to the speaker, it can't produce more sound cleanly. The amount of power it can handle is limited by the amount of heat it can stand. Too much power = too much heat = speaker burnout.
I think, if it is more volume you need, than you need more speaker size, (another cabinet) The speaker needs the correct wattage supplied and the amp needs the proper load. It all has to be balanced. That is my limited knowledge on the subjuct. Maybe Alex can pick up on this thread.
Rocky
PS. I can't imagine that your present rig can't produce enough volume for a medium size venue. Your band must be HORRIBLY LOUD.
Edited by Rocky MacDougall (05/11/08 09:09 AM)
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#1940606 - 05/11/08 09:01 AM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: Rocky MacDougall]
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Big Daddy from Motown
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JUST TURN DOWN!!!
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#1940610 - 05/11/08 09:05 AM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: Big Daddy from Motown]
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jcadmus
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You might trying dialing back the output from the Avalon into the power amp, and boosting the power amp a bit.
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#1940682 - 05/11/08 12:12 PM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: jcadmus]
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Tom Capasso
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+1
If you really do need more sound, I think I'd buy another 4 ohm.
Tom
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#1940708 - 05/11/08 01:09 PM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: BenHack]
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C. Alexander C.
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Absolutely, if possible. Your drummer may play more quietly if you're quieter.
I often run into headroom (clipping) problems when using effects or slapping.
Power amp hitting the limiters is fine, but:
You might trying dialing back the output from the Avalon into the power amp, and boosting the power amp a bit.
if the clip limiters aren't lighting but you're getting distortion.
Also just to make sure,should I be driving the power amp with the line or mic level from the U5?
Either is fine but line level is louder.
+1
If you really do need more sound, I think I'd buy another 4 ohm.
Tom
Exactly. It'll make a BIG difference.
Alex
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#1940722 - 05/11/08 02:19 PM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: C. Alexander C.]
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BenHack
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Thanks for the replies guys.
Turning down is not an option. As I said I don't always have PA support and one of the most common requests from people in the audience (whose opinion I respect) is that bass needs to be louder. Personally I'd love to play much softer but this is the situation I find myself in.
To clarify what's happening. The clip lights are lighting up when I'm getting the distorted sound. I have the poweramp volume on maximum so unfortunately I cant turn the volume on the preamp down. I have thought that I'm simply trying to get too much out of 1 x 2 10 cab.
Alex, just so I understand this better. Why would adding another 4 ohm cab be preferable to having 2 8ohm cabs and bridging the poweramp?. Also how is is adding a 4 ohm cab able to increase volume? Thanks for all your help so far.
Ben
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#1940910 - 05/12/08 04:49 AM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: BenHack]
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Big Daddy from Motown
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Go for the second 4 ohm B2 if you really need to play that loud.
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#1940922 - 05/12/08 05:30 AM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: Big Daddy from Motown]
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Paul K
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I'm not surprised that one B2 isn't enough for a loud band in a medium sized club, with limited PA support. My B-1 alone wasn't enough for anything but jazz gigs; two wouldn't be enough for the gigs you're describing. You're clipping the amps 'cause Scotty can't give'er any more power without a new set of dilithium crystals. You're pumping 900 watts into a speaker that has a power handling limit of 350 watts RMS. After the first 350 watts, the sound doesn't get louder. It's a testament to these speakers that yours aren't already in shreds. Adding another B2 (Or B-2W) is the easier way to do it, as your amp has two channels. If that still doesn't do it, then swapping to 8 ohm cabinets would give you the ability to run four of them instead of two. Then you also need to buy a bigger van, and a jar of earplugs. My vote in this non-democracy is to try another 4 ohm cab first, 'cause then you can run some stereo effects; nothing is cooler than that. Borrow one first to see if it gives you enough decibels.
And IMHO, Getting a drummer to play softer is like trying to reason with my ex-wife. Logic in these situations is irrelevant.
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#1940959 - 05/12/08 06:54 AM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: BenHack]
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C. Alexander C.
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Alex, just so I understand this better. Why would adding another 4 ohm cab be preferable to having 2 8ohm cabs and bridging the poweramp?. Also how is is adding a 4 ohm cab able to increase volume?
Adding another cab will give you 3dB extra output from coupling and 3dB extra from the second channel of the power amp doubling your total power output. I can't see 1500W per B2 giving you any more output than 900W per B2 but it will increase the risk of blowing things. Remember to keep the clip limiter and 30Hz filter engaged. If you have your clip limiters engaged and you're hearing distortion when those LEDs flash, then it's your speakers distorting, not your amp - more power will not help, only more speakers will.
Alex
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#1941213 - 05/12/08 02:41 PM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: C. Alexander C.]
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BenHack
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Thanks Alex
More speakers it is then! I always have the limiter and the high pass filter on. I think I'm also going to try using the 50Hz filter to see if that makes any difference. To be honest I think it's using the envelope filter that causes a lot of the problems. Perhaps reducing power in the the low end of the sweep will help as well as getting another cab. Cheers
Ben
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#1941379 - 05/12/08 11:43 PM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: BenHack]
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C. Alexander C.
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I think I'm also going to try using the 50Hz filter to see if that makes any difference.
No, don't do that. The Acme's power handling between 30 and 50Hz is greater than that between 50 and 70Hz (due to the port taking the load as you go lower). I didn't realise that at first, tried the 50Hz filter when I was using heavy effects at very high volume, and the speakers really didn't like it.
Alex
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#1941384 - 05/13/08 12:47 AM
Re: Clean Headroom with PLX3002 and Acme B2
[Re: C. Alexander C.]
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BenHack
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Cool Alex. Thanks for the heads up before my rehearsal tonight.
I'm amazed at how much I still have to learn about all this stuff. It's great to know I can use the collective wisdom of all of you guys!. Cheers
Ben
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