DIY PA Idea

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David Luscombe

Sophomore
Mar 24, 2011
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Hi All

So I have been given 4 x B&C 15ps100, 4 x B&C 15ps75, 4 x P Audio SN15mb and 2 x B&C DE45 on B&C ME20 horns. All these drivers are brand new still in boxs (YIPPEE).

I have made quite a lot of various boxs and so am confident in the building part. I have already decided to do this all active.

I immediatly thought that a set of 2 x 15 and horn tops using the the PAudio units for the low mids section and turn the rest of the B&C drivers into subs so that would be 4 x single 15 subs pe side.

Then I started thinking of ways to make the pa more PACK freindly for cars and the like and thought maybe i could cut the tops into separate boxs for each component which would allow the pack to be more flexible depending on vehicles being used for transport. Remebering this will be for a Pub Band, and also thought it may be more flexible for various gigs instead of always haveing to use the 2 x 15 boxs could only take 1 x 15 low mid and two subs aside if needed.

I am also curious as to what you all think of whether the Subs that i have loaded as a single frontloaded box would play together ok considering they are two different drivers.


Any thoughts suggestions and ideas welcome.

Cheers Dave
 
Re: DIY PA Idea

David Luscombe said:
I am also curious as to what you all think of whether the Subs that i have loaded as a single frontloaded box would play together ok considering they are two different drivers.
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Dave,

Assuming the boxes have near the same Fb, they will "play together" OK, but ideal boxes would be slightly different for either driver, as their TS parameters are different. The 15PS76 is slightly more sensitive and handles less power, turning the amp side powering them down a dB or two from the 15PS100 would get them close enough for rock and roll in pub land.

Art
 
Re: DIY PA Idea

Hi

Thanks for that Art.

So then what about the top boxs, instead of makeing them a 2 x 15 & horn in a single box, make a box for each component. Would this work or not?

Cheers
 
Re: DIY PA Idea

It would work, but I'd put the HF horn and a 15" in one box to save weight (and connectors) and get them as close as possible to each other (less comb filtering and diffraction problems).

With 2 x 15" subs below you probably will seldom need the second 15" for mid, but if you do it should be rolled off lower than the upper 15" anyway to sound cleaner (less comb filtering). The little B&C ME20 is going to need to be crossed above 1500 Hz, to get the 15" dispersion to match that high will require some side plates on the 15", probably slightly more restriction than on the 10" in the photo below.
 

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Re: DIY PA Idea

Art Welter said:
It would work, but I'd put the HF horn and a 15" in one box to save weight (and connectors) and get them as close as possible to each other (less comb filtering and diffraction problems).

With 2 x 15" subs below you probably will seldom need the second 15" for mid, but if you do it should be rolled off lower than the upper 15" anyway to sound cleaner (less comb filtering). The little B&C ME20 is going to need to be crossed above 1500 Hz, to get the 15" dispersion to match that high will require some side plates on the 15", probably slightly more restriction than on the 10" in the photo below.
Click to expand...


TOA had some 15/horn boxes years ago that used a slot to produce the right dispersion from a 15. I don't think they sold very well, because people thought the 15 "blocked off" inside the box....
 

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Re: DIY PA Idea

Hi,
Very cool ideas. Next question is, how do you decide how much of the winged bit do you use? And if anyone wishes to share some of the theory behind it I would love to learn a little about it.

Cheers
 
Re: DIY PA Idea

The "theory" is dispersion narrows when a driver's piston diameter is greater than the wavelength it reproduces (the reason tiny tweeters are used), the practice is you reduce the exit diameter width until the LF dispersion matches the HF horn's dispersion at the acoustic crossover.

Various shapes other than straight sides have also been employed to help deal with cone breakup, which makes for non-pistonic dispersion patterns. As Tim mentioned, the practice is not well received by consumers who listen with their eyes rather than ears.
 
Re: DIY PA Idea

ok so........ I've listed the drivers i have available, lets here what some other idead you guys would have using the drivers I have.

Maybe there is a lot I havent thought about!!
cheers
 
Re: DIY PA Idea

David Luscombe said:
ok so........ I've listed the drivers i have available, lets here what some other idead you guys would have using the drivers I have.
Click to expand...

Well I can outline my process for you:
You will need 1) a two channel sound card 2) a V-I box from LinearX or someone else 3) a microphone 4) any two channel measurement software like REW.

1) Make the box that will work for the situation about the size predicted by a simulation. (don't ask me about this)
1a) Normally this is just choosing the correct volume and pushing the two sources as close as possible.
2) Make a port kit for the box, depending on size, in either half or 1in increments.
3) Mount the drivers in the box as a two way and measure on axis response and then impedance.
3a) Things don't look right then adjust drivers. Ie I will make a new LF driver first to better match the HF. Next, I will choose a new HF.
4) Use the port kit to adjust ports until the cabinet is tuned correctly. For me this is over damped slightly. As things will become under as they heat up.
5) Make Bi-amp DSP settings for the enclosure and test the polar pattern.
5a) Fix any issues with the cabinet discovered in polar measurements.
6) I'm done unless it's going to be passive and then I start at (2) again after I make a network.

P.S. I would never make a 15" and 1" exit driver. Find a good size appropriate mid speaker to go with the tops ;-)
 
Re: DIY PA Idea

Hi David, I don't put my horns in boxes. I mount them on a frame I suspend from the lows.
This way, I am not dependent on the boxes to get my horns in the air, and I don't have a box around the horn.
I save a lot of weight this way. And I have a lot of flexibility on where I point my horns.
 
Re: DIY PA Idea

Mark, that is a great reply and thank you for sharing, I just now have to pick up the pieces of my brain of the floor and put it back together and get my head around it.

Art, that is a great idea. Any chance if photos of how your rig looks when you do this??

In the ideal world I would love to get some different mid drivers and not use the 15, but that won't happen so I am stuck with what I have.

Keep the ideas coming!!!

Cheers
 
Re: DIY PA Idea

Tim Weaver said:
I think he was replying to Jack Arnott's idea that he leaves his horns naked.

What the OP doesn't know is the size of Jack's horns. The OP is working with a little 90x60 1" entry horn flare. Leaving this out of the box and flying it up high will do him no good at all....
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Yep Tim, you got it all in one. I did have a feeling that Jacks horns may have been bigger than I have.

Also I get the feeling I am going to have to spend some money on this. Oh well let see what that brings (the mrs is gonna hate me LOL)!!!
 
Re: DIY PA Idea

David Luscombe said:
Yep Tim, you got it all in one. I did have a feeling that Jacks horns may have been bigger than I have.

Also I get the feeling I am going to have to spend some money on this. Oh well let see what that brings (the mrs is gonna hate me LOL)!!!
Click to expand...

If you sell the Paudio 15's you could buy some mids. Then use the PS75's in the tops and the PS100's in the subs. For 1 stack a side this could be a decent PA.

A better move would be to sell the Paudio drivers and the PS75's. Buy a pair of mids, and a 4 18's of some kind. You'd have a dual 18, with a dual 15 three-way top. Quad amped with a dsp it would be great for a club.
 
Re: DIY PA Idea

David Luscombe said:
Yep Tim, you got it all in one. I did have a feeling that Jacks horns may have been bigger than I have.

Also I get the feeling I am going to have to spend some money on this.
Click to expand...
There are literally thousands of good sounding 15/1" exit horn combinations around dating back over 70 years, but they don't use tiny HF horns.

Your B&C DE45 one inch drivers using larger horns (which you could build or buy for very little money) can be crossed low enough to work well with a 15".
 
Re: DIY PA Idea

Ok so, I didnt really think some of this through and as it turns out I love Tims idea of the 3 way tri amp box.

I am thinking that maybe I can sell the P Audio Drivers and buy a nice set of 1inch mids (maybe B&C to go with the rest), use the Ps75's as the 15 in the top box and use the PS100,s as subs and work my way up to a bigger sub at some point.

Is this a more sensible idea?? Any pitfalls I am not thinking of. And yes the packing idea has gone out the window as well LOL!!!

cheers
 
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