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Lockdown Experiments
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doober View Drop Down
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    Posted: 03 June 2020 at 10:16pm
I've had plenty of spare time recently due to having no real work to do. Finally got around to trying a few ideas I've been thinking about for a while.

I had to use cheap nasty ply as it was all I could get, and will ultimately end up in a skip anyway. Drivers will be whatever I can find in the house or borrow from other boxes for now, I'm just testing the layout really.

The box uses 2 10", 2 6", 2 1"





Mid and HF horns are made from GRP. Unfortunately the local garage/ convenience shop only sells kits containing rather heavy mat, and doesn't have gelcoat, so they are a bit of mess...





I made the moulds for the horns from silicone poured into wooden patterns for the mid, and a plaster cast from an MDF pattern for the HF.



I later remade the mid horn moulds as they wouldn't flex enough, so I made some pre curved ones.
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dlyxover View Drop Down
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Points: 1507 		Post Options Post Options   Thanks (0) Thanks(0)   Quote dlyxover Quote  Post ReplyReply Direct Link To This Post Posted: 03 June 2020 at 11:39pm
awesome, be good to see it finished, loaded and some response plots

Smile
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JulianDA View Drop Down
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Points: 110 		Post Options Post Options   Thanks (0) Thanks(0)   Quote JulianDA Quote  Post ReplyReply Direct Link To This Post Posted: 03 June 2020 at 11:56pm
Thats some awesome DIY! And the idea to use silicone molds for the real curvy horns is nothing but genius. Thumbs up for that! Clap
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doober View Drop Down
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Points: 1118 		Post Options Post Options   Thanks (0) Thanks(0)   Quote doober Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2020 at 9:11pm
I made some rear chambers for the 10" drivers, using a cut down plastic plant pot for a mould. GRP is the obvious choice, but as an experiment I also made one from a Stella box, a magazine, and lots of PVA. It is much stronger than I thought it would be, but took nearly a whole day to make. The GRP one took less than 2 hours, and I expect this to be less in future as my fibre glassing skills hopefully improve.
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Points: 1258 		Post Options Post Options   Thanks (0) Thanks(0)   Quote chris_k Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2020 at 9:54pm
I remember when speakerplans was like this when i first joined. People posting build pics, experimenting.
Excellent stuff!
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doober View Drop Down
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Points: 1118 		Post Options Post Options   Thanks (0) Thanks(0)   Quote doober Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2020 at 9:56pm
I loaded the mid drivers, they came from some hifi speakers, I don't know the specs for them. The free air resonance was around 60Hz, a bit too low, so I sealed up the baskets with plastic and epoxy. This pushed the resonance up to around 500Hz. I have no idea where the mass roll off or inductance roll off will be.

I already have around 50 measurements, I won't put all of them up here!

First is around 1m from the front of the cab, on axis, no EQ or filters. The low end is better than expected, I can't do much about the top end until I get the proper drivers. The dip around 1.5kHz is worrying- crossover to the comp drivers needs to be higher than that.




Thinking the dip was caused by the open (both ends) hf horn between the 2 mid horns, I blocked the mouth of the hf horn with ply and plasticine. This is the result, an improvement.




Next I unblocked the hf, and blocked both lf horns with cardboard and gaffer tape. The dip returned, as expected, plus a bit more loss around 1kHz. Below 800Hz has flattened though.




Next obvious thing was to try blocking hf and lf, this gave me a new narrow dip above 1kHz.




The big question is how this will all change when all the drivers are in.
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JonB67 View Drop Down
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Points: 1373 		Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2020 at 10:04pm
Plasticine cardboard and gaffer tape? LOL

You're a legend, this is awesome and I'm subscribing to this thread. 
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odc04r View Drop Down
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Points: 5483 		Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2020 at 10:53pm
That's great stuff! Loving the creativity. Hell of an experiment, and the weirdest "adult toys" I have ever seen. At least I assume that's what the pink silicone is all about really?
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Noyzmunky View Drop Down
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fantastic.
my name is Inigo Montoya...you killed my father, prepare to die!.
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doober View Drop Down
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Points: 1118 		Post Options Post Options   Thanks (0) Thanks(0)   Quote doober Quote  Post ReplyReply Direct Link To This Post Posted: 05 June 2020 at 8:48pm
I put the other drivers in today. It was a bit tricky getting the lower compression driver bolts in.



Hopefully next week I'll get some more measurements done.
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Digbethdave View Drop Down
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Points: 405 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Digbethdave Quote  Post ReplyReply Direct Link To This Post Posted: 05 June 2020 at 9:03pm
Are the front baffles/guides asymmetric? 
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doober View Drop Down
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Originally posted by Digbethdave Digbethdave wrote:

Are the front baffles/guides asymmetric? 


Which bit? The ply horn mouth is 100 degrees, 50 left, 50 right.
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