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Multi-Way Conventional loudspeakers with crossovers

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Old 20th April 2018, 02:26 PM   #381
3ll3d00d is offline 3ll3d00d  United Kingdom
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This is the mid and the cd on the horn taken with a ~4ms window at 1m on axis

Does it look as expected?

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Old 20th April 2018, 05:07 PM   #382
bwaslo is offline bwaslo  United States
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A little difficult to say - your 4ms window is going to have odd effects at the low end of the midrange (4ms means you can tell basically nothing below 250Hz, and only vaguely below about 500Hz). You may need to measure closer if your reflections are coming in too soon, and/or use a 'frequency dependent window' to get a somewhat useful though still approximate idea.

Also, without being on a baffle things will behave differently -- the horn is too small to do anything much at below 700Hz, so baffle effects will still be evident, in particular "baffle step". Here's what my drivers looked like, on the baffle, probably closer (and evidently with smoothing, maybe 1/3 octave.... didn't record what it was exactly). These are at different angles, highest ones will be on-axis.

SS Driver Curves.png

That said, I think you're in the ballpark (the bump near the upper end of the midrange was a bit of a challenge for the crossover design).
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Last edited by bwaslo; 20th April 2018 at 05:10 PM.
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Old 20th April 2018, 10:47 PM   #383
3ll3d00d is offline 3ll3d00d  United Kingdom
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thanks

yeah I played with different windows and the peaks remained so I thought I'd put that graph up there as I suspect it will take me the best part of a month (in elapsed time) to the box together
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Old 21st April 2018, 04:17 AM   #384
bwaslo is offline bwaslo  United States
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If the peak remains (much beyond what's in my graph), you might consider taking out some of the filler if you can -- more front volume will reduce the top end. Maybe against intuition, narrowing up the channel from cone to port holes can do similar. I wouldn't do that until you've got these on a baffle, though (cardboard can be good for a mock-up baffle)
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Old 30th April 2018, 02:30 PM   #385
Hrmmf is offline Hrmmf  Denmark
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Quote:
Originally Posted by bwaslo View Post
Here is how the midrange mounts to the waveguide. The flat mounting plate board is glued on, and sealed with, epoxy putty. I'll have cutting diagrams and dimensions, as well as hole drilling info in some later posts.
Click the image to open in full size.
Hi Art,

Would you reveal which epoxy putty you are using and does it do both: glue and seal?
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Old 30th April 2018, 05:32 PM   #386
bwaslo is offline bwaslo  United States
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J-b Weld 2 oz. Epoxy Putty with Temp. Range of Up to 300 Degrees F, Gray Model: 8267-S
JBWeld Epoxy Stick, or I've used other brands including Harbor Freight 's cheaper version. Attaches and seals
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Old 1st May 2018, 06:28 AM   #387
Hrmmf is offline Hrmmf  Denmark
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Thanks Art
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Old 6th May 2018, 09:23 PM   #388
3ll3d00d is offline 3ll3d00d  United Kingdom
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I made good progress on my first one this weekend. Your instructions are really clear, precise and well thought out, thanks for writing them up.

baffle.jpg

frame.jpg

One question re the woofer mounting, you drill through the baffle and screw from the front. Is it completely impractical to just screw into the rear and not drill all the way through? It feels like it should be doable (to not go all the way through) though that might be because I haven't got the baffle and sides on yet.

FWIW (re the instructions) the one bit that wasn't crystal clear was the woofer cutouts though I think is largely a function of having to translate to metric and use different size bits. The reason being the the outline of the cutout is not marked on the diagram though obviously you can calculate this from the specified drill bit diameter.
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Old 6th May 2018, 10:07 PM   #389
bwaslo is offline bwaslo  United States
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Quote:
Originally Posted by 3ll3d00d View Post
Is it completely impractical to just screw into the rear and not drill all the way through?
Well, you could do that before gluing the baffle onto the box, but if you ever needed to remove or replace the woofer you'd be in trouble..... It's already pretty tight in there even to just get your hands in for putting the nuts onto the screws. I don't see it being possible to get a screwdriver in to drive screws from the back.

For the woofer cutout, I guess you mean the oval output port shape? It's not at all critical, just make sure it isn't wide enough to break the seal between inside of box and outside, and leaves enough wood above it for the waveguide to mount. It's a path for air pressure to pass through, vertically centered close to the waveguide edge - not really a 'tuned' area.
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Old 7th May 2018, 09:11 AM   #390
3ll3d00d is offline 3ll3d00d  United Kingdom
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Quote:
Originally Posted by bwaslo View Post
Well, you could do that before gluing the baffle onto the box, but if you ever needed to remove or replace the woofer you'd be in trouble..... It's already pretty tight in there even to just get your hands in for putting the nuts onto the screws. I don't see it being possible to get a screwdriver in to drive screws from the back.
I was thinking of attempting to use a butterfly wing screw so I could tighten them by hand alone or perhaps something like Flexible Drill Bit Screwdriver Connectors 300mm Flexible Shaft Soft Shaft Bit Extension Screwdriver Universal Holder Connecting Link Bits Plastic Black Metal Flexible Hex Shank Extension Flex Electric Drill Extention Bit Holder Connect Rod: Amazon.co.uk: DIY & Tools
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