Karaoke Forums

I'm trying to help a friend rig up his sound equipment and have a couple questions.

He has a laptop, a Mackie passive mixer, a two-channel crossover, a two-channel maximizer, a pair of two-channel amps, two mains and two subs and wants to run in mono.

I was thinking of using a stereo to mono adapter out of his laptop and into the left channel of the mixer, and then to his crossover and then to his maximizer, and then splitting to both channels of one of his amps, and then out to the mains.

Then using another stereo to mono adapter out of his laptop into the right channel of his mixer, and then to his crossover, and then to his maximizer, and then splitting to both channels of the other of his amps and then out to the subs.

Basically I'm thinking of using the left mixer channel for mono mains and the right mixer channel for mono subs.

Does anyone see a problem with this? Is there a better way to use both sides of both his amps coming out of a single two-channel crossover? I don't know anything about bridging amps. Is that something that I should try? And if so, how do I do that?

Marty, what kind of crossover is it? If it's a stereo in, stereo out unit then you can do what you want and you'll end up with a configuration that is very similar to what is often called AUX-fed subs in pro-audio. You will be able to adjust the top-to-sub mix by using the PAN knobs.

I suggest you plug the laptop L/R outputs into two different mono channel strips. This will ensure that you don't lose content in stereo recordings. Stereo has been around for long enough that a lot of recorded music has instruments or vocals primarily in one channel or the other for at least part of the songs. If you just drop the right channel from the laptop you might occasionally regret it.

Note that a PA with stereo tops can be especially useful for karaoke. Since you have amateur singers who may walk out in front of the PA with their microphones, you can pan their input away from the speaker they are standing in front of so they won't cause feedback. Since your friend already has all the tools to run his system in stereo, I suggest doing that instead. I bet the crossover has a 2x3 mode. There is no reason to run the subs in stereo of course.

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Jeff Wheeler, moonlight DJ/KJ

Marty, honestly I'd love to get more details about the specific equipment involved as there are different options based on what models and such you have. The Mackie mixer may be capable of sending a mono mix in a couple of different ways depending on which one it is. Also some crossovers offer an ability to take a L and R signal and sum them into a mono output. Others you'd provide a single mono input and they'd output both the L&R signals. Additionally, some amplifiers have capability to run parallel mono (different from bridging) and that would be another possible solution.

So there are a number of different ways you could possibly do this. The number and type of options vary based on what equipment you've got. And certainly finding you the best option would require more details. Can you get us some additional information (model numbers)?

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DJ Tony
Let It Rip Karaoke

Okay, here we go... My friend just called me and gave me all the model numbers...

The mixer is a Mackie 802-VLZ3

The crossover is a VBX 223XL 2-way stereo/3-way mono

The maximzer is an FR2500

The amps are:
Mackie FR2500
Crown XLS 402

The mains are a pair of Peavey 215

The subs are a pair of Harbinger HX 118S


Thank you for any advice y'all can give me to do this up right.

Marty

Eww ok, lots of fun to play with here, unfortunately your options are somewhat limited. Here's what I would suggest as the easiest way to get what he's looking for. Get a 1/8" TRS to Dual 1/4" TS Y Cable to connect the laptop to the mixer. Connect the 1/4 ends to the "Mono L" inputs on the two stereo channels (5/6 and 7/8 ) of the mixer (This effectively converts each to a mono channel). Now leave the pan control for both of those channels panned to center. That will give you the same summed signal going to both the L and R output of the mixer. From here you can connect everything else as if it were a stereo signal coming out of the mixer. Run the mixer output to the maximizer (I'm not aware of one with the model number FR2500 so I assume it's something else). Then run that to the crossover which you configure for 2-way stereo operation, you don't need to use the mono-subbing for the low frequency on that cross-over, leave that in stereo too. Follow suit with everything else, connecting everything as if it were a stereo signal and you're all set. Your patching at the mixer is what will make it a mono output.

I assume he's planning to use the Crown to drive the Peavey full range cabinets and the FR2500 to drive the subs? That would be by far the best matching of amp to speakers given what he's got.

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DJ Tony
Let It Rip Karaoke

ok, sounds simple enough. Couple questions to clarify though...

Which inputs do I use on the crossover?

What is the best way to connect the single crossover to the pair of amps as each amp has inputs for two channels?

Connect your Left channel output to the Channel 1 input on the crossover and your Right channel output to the Channel 2 input on the crossover. Connect the High outputs from Channels 1 and 2 on the crossover to the Left and Right inputs on the Crown amp (Peavey 2-Ways). Connect the Low ouputs from Channels 1 and 2 on the crossover to the Left and Right inputs on the Mackie amp (Subs).

Like I said, connect it all like it's in stereo (as descirbed above). If you connect to the mixer the way I described earlier and set it as specified, the mixer will be providing a mono output via the Left and Right outputs.

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DJ Tony
Let It Rip Karaoke

Thanks for the help Rip! System sounds much better now. Only thing is that I notice that for the subs and the mains to sound like an equal mix, I have to turn the subs gain all the way up and the mains gain about a quarter of the way up. That's with the subs on the Mackie and the mains on the Crown. I thought about switching them, but first checked the specifications and see that the Mackie is the bigger amp and so I guess I should leave it as it is. What do you think?

Yeah I definitely would not switch them. Personally I'd be looking for a larger amp for both the Peavey's and the subs. Both could handle much more than what the current amps are pumping in to them. However, given what you've got, having the FR2500 run the subs is the best option.

One thing you might want to check is where is the crossover point set to right now. With the combination of those subs and the 3 speaker cabinets, I'd set it somewhere between 80 and 100Hz. If it's set too high or too low that could affect the performance you're getting.

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DJ Tony
Let It Rip Karaoke

I've got it set right around 100. Any higher and I start to hear hints of voice in the subs which I don't like. Also, the club my firned owns isn't very big at all so I think the amps will be just about right.

Actually I would have summed the sub from the crossover to a mono & bridged the sub amp (FR2500) to both 18's.

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LIKE Lonman on Facebook - Lonman Productions Karaoke & my main site via my profile!

The subs are 8 ohm subs, wire them in parallel and then bridge them on an amp and the amp is only going to be seeing 2 ohms. The FR2500 is not designed for a 2ohm bridged configuration. Might it handle it, maybe. Does the manufacturer recommend, specify or support that config, no they do not.

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DJ Tony
Let It Rip Karaoke

Wiring 2 8 ohm subs in parallel will yield a 4 ohm load which the amp is more than capable.

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LIKE Lonman on Facebook - Lonman Productions Karaoke & my main site via my profile!

Right if they were on a single channel. When you bridge an amp, that also halves the impedence so your 4 ohm parallel load just became a 2 ohm load.

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DJ Tony
Let It Rip Karaoke

If you put 2 8 ohm speakers bridged to one amp, that is a 4 ohm load. The bridged output of the amp sees that load as 4 ohms if both 8 ohm speakers are tied together. If it was only 1 8 ohm speaker it is 8 ohms, 2 8 ohm speakers yield a 4 ohm load.

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LIKE Lonman on Facebook - Lonman Productions Karaoke & my main site via my profile!

Well this can be done really simple. But unfortunatly the xls 402 only handles an 8 ohm load in bridge mono.

You definatly want to use the mackie for the subs and crown for the tops. With a crosssover point of 100hz your tops should keep up just fine.

Also couple the subs together in the middle of your setup.


(Speaker)----------------------{sub}{sub}-------------------------------(Speaker)

Use audio physics to your advantage. You can get a little more "boom" from the subs if you tuck them next to a wall, or better yet, in a nice right angle corner. That will reflect the sound more where you want it, instead of the sub radiating in all directions.

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Dave's not here.

Another option it to simply put the two subs together rather than at separate locations.

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DJ Tony
Let It Rip Karaoke