135Hz Segmented Horn Midbass Build

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I have decided recently to build a full horn speaker pair, likely 3 or 4 way. As of current I have a pair of Seos24 horns to play with and I'll be using those with the Radian 1.4" 745PB CD, I will test this combo in the 600-18khz range initially to see how it sounds and how flat I can EQ it. If I don't like the top end then I may add a CD or other tweeter above it, but more on that later.

What a beast!

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I am also considering building some 18" JBL 40hz horns as well for the bottom end, we'll see.

I got some plans from John Inlow (he's been really great to work with!) for a 135hz horn that uses the B&C 12" 12PE32 midbass, I had to wrap my brain about how to build this thing and finally found a way to do it that I was comfortable with. Note a 12" compound sliding miter saw is a huge help.

Since this is the first segmented horn I've built, I decided to build one prototype just to test some of my build techniques and also to see how it sounds and what the FR looks like. Again I only built one and this is by no means a final build, based on what I learned on this one I will be building 2 more with changes his weekend.

First I started with the compression chamber, the driver sits in about 1-2 liters of airspace, crazy I know!

I started by ripping a piece of 5.5" wide stock with a 22degree angle on each side, basically a parallelogram. Then this piece goes in the chop saw, miter set to 22.5 degrees, I found if I can prop this piece up on the 22d angle then I can make the 22.5d cut and it automatically sets up the compound angle as well, which is around 43d

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By setting up a stop you ensure each piece is identically long, just flip the piece top to bottom with each cut and you only need 8. I can literally build an octagonal box up to 5.5" tall in a matter of minutes now.

I thought about how the hell to clamp these things and then I wondered if I could just tape them together...wala!

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Unfolded, just run a bead of glue down each crotch face, wrap it up and tape. I put a flat board on top with some weight on it on a flat surface just to keep it totally square. Using the miter saw its easy to cut the top "cap piece" out as well. I also did a flat octagonal flange which I glued to the bottom of the chamber as a mounting flange.

Now for the fun part, the actual horn! This is what I did on this first piece below, I will be making my final horns using a different technique (similar result) that is faster, easier and gives a little nicer result. Basically I'll make sections with the miter saw using the compound angle feature, since the saw can cut up to 13" wide I can just build each horn in segments.

First I traced out my sections and rough cut oversized versions. Then I made a template with some 1/2" plywood, I used this template to router flush cut each piece so they are all identical. Identical pieces are the key to making these horns!

Bottom flare

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Top flare

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Flush cutting the pieces

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Then since I had already cut the primary angle, I just needed to cut the compound angle which I did with the table saw, about 41d for the lower flare and 43 for the upper

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And boom!

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I'm skipping a few steps but here is basically where things ended up

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Hornresp modeled response

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Actual response, not bad!

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I am still breaking it in but wow is this efficient! Midbass is very fast and impactful like nothing I've ever heard, for fun I temporarily threw a DE250 and Seos12 in the mix and threw a 6db cap on it, not too bad! This is definitely a very lovable setup even w/o a sub, granted this is all hair left channel listening so far =)

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More to come soon, let me know your thoughts and if you have any questions!

Thanks,
Javad
 
I built a pair of John's 135hz mid-bass horns with the 8pe21's. They're so damn awesome, I had them in my living room, half painted for over a year.

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for the compression chamber I built them basically the same way you did, but used biscuits the second time I made them, and used pocket screws on the interior to mount them to the baffles:

A few pictures here too:

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It's a great design and I bet you will love it. It looks like you are well on your way to making a great pair of horns.

Cheers!
 
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Very cool stuff indeed!! Please keep the pics coming.

I have often thought about building a pair of the 135hz horns but the "audio" room
(i.e. basement in a very old house) is only 14'w x 18'l x7'h & I don't think I would have the extra space to add a tapped horn for 50-150hz duty. How big is your dedicated room?

Just wondering ... are you going use minidsp or something along similar lines for subwoofer integration below the 135hz horns?
 
that's a gorgeous build and nice graph - - do any of you horn guys think a 0.7 or so scale University Classic with 12pe32 would make it up to around 500? I should put my 12pe32 in my RCA-Fan derived horn to see if it will reach higher than a Community 12. RCA-Fan says "no" - that it will only tilt response upwards.
 
I thought Inlow's 135Hz horn used the 8" driver instead of the 12"?

BTW, why did you choose the 135Hz horn instead of the 100Hz? Just trying to understand your thought process.

Nice build as usual from you!


Hey, there is an 8" version too, what I built is a modified version of the 100hz 12", with slightly higher tuning it extends higher into the 800hz range and according to John is an overall better sounding design for audiophile listening over the 100hz version. I wanted the extra punch the 12" provides over the 8".

Thanks!
Javad
 
How big is your dedicated room?

Just wondering ... are you going use minidsp or something along similar lines for subwoofer integration below the 135hz horns?



It's a big room acoustically, it's open on one side to a hallway and the rest of the house, but the room itself is about 30x15'.

Yes will be using a miniDSP 4x10 to EQ, XO and time align everything.

Thanks!
Javad
 
I'm also building a bass reflex box for the 12" B&C 12PE32 so I can measure and listen to and compare to the horn, the port is also plug gable so I can test sealed as well. The enclosure is 1 cubic foot which models well for this midbass and tuned to 90hz.

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The port, 4" by about 1.5" tuned to 90hz

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Thanks,
Javad
 
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It's only down 5db to 800hz so with a little miniDSP EQ it should flatten right out. I plan on testing it and the radian horn xo in the 500-800hz range to see what I like best.

Thanks!
Javad

Very nice work, my friend! It'll be interesting to see the measurements with the second build. Also, how did you place the mic? Do the measurements flatten out over distance?

Thanks for taking the time to exhibit your project. I'm looking forward to seeing the completed system.

John Inlow
 
Very nice work, my friend! It'll be interesting to see the measurements with the second build. Also, how did you place the mic? Do the measurements flatten out over distance?



Thanks for taking the time to exhibit your project. I'm looking forward to seeing the completed system.



John Inlow



Thanks John! I'll do more measurements, I'll also post the response in the ported box, problem is the further info back the room starts interacting, im quite happy when things are in a 5db range essentially.

This was with the mic about 6" outside the horn exit.

Javad
 
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