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Thread: DIY 4520 bass horn build

  1. #1
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    DIY 4520 bass horn build

    Im building a pair of jbl 4520 bass horns. This will be my second speaker project and my first from the ground up build. Im not too versed in carpentry so Im taking my time. Im also only using mdf since nice plywood is expensive. Plus since im not to good at carpentry Im going to trash some wood. Ill feel better about trashing cheaper mdf this some high dollar plywood. I should be done with the first horn soon. All depend on how much energy I have left after work at night. I finished the frame for the first horn. Drew out the plans on the inside of one of the sides then transfered it to the other side by drilling hole through it at verious points. I had the other side clamped underneath that side. Then I just played connect the dots.

    I used one side for painting a chassis so thats why theres the black spot on it. These will either be painted or maybe veneered. Havent thought that far ahead. I have a pair of gpa 416-8b driver that Im going to try in them first. But Im not setteld on that yet. I only decided to build the 4520 for the longer horn path. I really didnt need 2 woofers. I might just center the woofers in them and just us one.

    Ya I know crappy cellphone camera.


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    Nick

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    Senior Member Lee in Montreal's Avatar
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    Hmmm... I smell a single JBL 2240H driver for pipe organ music. fs of 30Hz and a Qts of 0.23 and quite able to sustain considerable power. Plenty on eBay for $140.00 with original JBL cones. And make that cabe a few inches narrower for a single 18" That will help with WAF...

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    Well a subwoofer is the next project. I wasn't going to use any jbl drivers though. I was going to stick 2 Dayton 15" dvc sub woofers in a 7 or 8 cuft box and tune the port for 20 Hz. There 90 db sensitivity. I was going to feed 250 watts to each woofer. 125 per voice coil. Then sit back until the police arrive, or my house tears itself apart. I did the math. At max excursion they would be moving 21 liters of air. . That enough to rattle a few teeth out. Who needs fiber in your diet when you can hit the brown note with your home stereo.

    Sorry couldn't help it.

    Quote Originally Posted by Lee in Montreal View Post
    Hmmm... I smell a single JBL 2240H driver for pipe organ music. fs of 30Hz and a Qts of 0.23 and quite able to sustain considerable power. Plenty on eBay for $140.00 with original JBL cones. And make that cabe a few inches narrower for a single 18" That will help with WAF...

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    Got a little work done last night. It was my own idea to put strips on the sides that hold the pieces of the horn flare in place. And something I can shoot a few brads through to hold it in place as the glue dries. Not much but its progress. Im hoping to have one cabinet done this weekend. Hopefully,


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    Cut the internal panels for horn number 1 today. Hope to put it together tomorrow and post some photos.

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    Senior Member Mike F's Avatar
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    Shouldn't the baffle be recessed or are you building a narrower version?

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    Quote Originally Posted by Mike F View Post
    Shouldn't the baffle be recessed or are you building a narrower version?

    Good call. Yep its not a exact copy. Its only 24" wide so I moved the baffle to the front. I was originally going to have it on the outside. But I figured this way is better. Its going to be used for home use so those few inches helps. It minimised the risk of me cramming a corner of it into a wall while I'm moving it. I don't want to gave to do any painting when I'm done.

    As I'm sure you can tell, I'm no carpenter. I'm quite happy that I've gotten this far. We'll see how I feel after the first ones built.

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    Senior Member Lee in Montreal's Avatar
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    The recessed front panel has two purposes in my opinion. The first one is to protect the woofers by the surrounding frame. That also allow to esthetically blend in purposefull reinforcing ribs on the sides and bottom of the mouth to keep them from vibrating.

    http://www.audioheritage.org/images/jbl/photos/pro-speakers/d55050.jpg

    http://www.lajazz.us/audio/JBL-4520/JBL-4520_001.jpg

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    I'm probably going to use a piece of trim around the edge. Like the mister Carl Huff mentioned in #52 in your waldorf thread. By the way, that was the hard discussion to make. Build a waldorf/ imperial or the 4520. I decided on the 4520 for size reasons. But this is my first start from scratch build. So maybe the imperial will be next.

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    Ive got the first cabinet put together. The picture is without the back on. Put that on the next day. Just a little more to do. Got to cut the holes for the drives and a jack plate. I think Ill put the where jbl did. On top.

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    This is as of last night. Put the driver in to chect fit and to see how it would look. I have to solder wires to the terminal plate. I used the same spot jbl did and put the on top of the cabinet. Ill do a little testing before I start to paint it with hammer tone black.

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    Tested the horn out. Seems to stay loaded down to 33hz. I was driving them with a 250 watt and. Its was crazy loud. I could feel it in my chest. It was making the stuff in my garage make all sorts of crazy noise. All and all not bad. I'll try it with a smaller amp to see how it performs tomorrow. Then I'll start to paint it.

    Nick

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    Well I didn't buy a table saw. I found a option that takes up less real estate. I bought a porter cable circ saw and a attachable fence made by kreg. Its called rip cut.


    It has a 24 inch capacity so it can do anything on a sheet of plywood.

    Nick

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    Quote Originally Posted by NickH View Post
    Well I didn't buy a table saw. I found a option that takes up less real estate. I bought a porter cable circ saw and a attachable fence made by kreg. Its called rip cut.


    It has a 24 inch capacity so it can do anything on a sheet of plywood.

    Nick
    Hey Nick,

    Let us know how that Rip-Cut guide works. Sounds like something I could use to make all the cuts on the wood for my Onken's. Cheers!

    Willy

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    Quote Originally Posted by intercity125 View Post
    Hey Nick,

    Let us know how that Rip-Cut guide works. Sounds like something I could use to make all the cuts on the wood for my Onken's. Cheers!

    Willy

    Hey Willy,

    I got a porter cable saw. A 5600rpm one with a mag housing and a cast shoe. Its a nice saw. First one I've ever bought. Figured its more of a need owning a house and all. I put together the rip cut. Its pretty simple. Doesn't cost that much either. 36 bucks at Lowe's. I didn't have a chance to test it though. Its a little tricky getting it on my saw. I imagine it would have been easier with a stamped shoe saw. I have my fathers old saw so maybe I'll make it a dedicated saw for it. Its an old craftsman 7" heavy but good. That is if it hasn't been thrown out.

    Anyway I brought down one of my 2380's with a 2445 on it down and hooked it up with a cross over off a 4638th. Played all sorts of stuff through it. I was getting SPL levels of a little over 120 db and it sounded amazing. Didn't have a tweeter one it but I could hardly tell. I don't think I ever maxed out the amp. Didn't hear any signs of distress. Well at least from the speakers. The house was a rock'en though. Now I'm prepping it for paint. Don't think I'm putting a toe kick on it.

    I'm very happy with those parts express woofers though. For being 75 a pop you can't beat them.

    Nick

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