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Walt's Stepped Horn

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darkmatter View Drop Down
Old Croc
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    Posted: 11 April 2008 at 1:31pm

Just wrote a massive post about this then it got deleted, aaaarrrgh.

I'll upload the pics later but they're not very exciting, my basement is dingy and it's a bit of a botched build so I didn't feel proud enough to take many pics.

I rebated the cab because I've never used power tools/a router before and I wanted to learn how. The dry fit was perfect, so I was feeling pretty confident, but then I used some scrap mdf for the bracing. Big mistake. 18mm mdf + one year in the basement = 19mm mdf. Put the whole build out slightly but it still worked okay because the rebates helped to keep it airtight.

So a couple of lessons learnt. Don't use 19mm instead of 18mm mdf! And when rebating, although tolerance can mean no headaches when you're doing the dry fit, as soon as you start gluing up 'tolerance' becomes 'error'. So I think I'll just go for a policy of striaghtforward accuracy in future.

Performance - very very impressed! It's just so effortless. Seems like a reflex tuned that low dies off a little just before low cut off, then when it reaches the port tuning it's audible. THe stepped horn just doesn't struggle in this area, something confirmed at low listening levels too. The music has a lower 'floor' when you've got the 30-40Hz content in there, which makes the overall sound much more complete to my ears, especially for certain dubstep tracks or the atmospherics in films where a goood quality mic has been used for the recording.

I'm using the Ciare driver, QSC PLX30002 bridged, tops are Adam A7 studio monitors, crossed at ~85Hz. Tops are delayed 30cm because they're slightly in front of the sub, don't know whether I should be adding an extra whole wavelength on to this i.e. 30cm + horn length?

Pics aren't exciting as I said but I'll stick a few up later. Main reason for posting this is to say thanks very much Walt for a brilliant design. Got a lot of inspiration from building it and I'll get a lot of use/annoyed neighbours from it too over the next few years.

 

For new builders:
- Wood screws - Stainless steel 4x40 (4mm diameter 40mm length) cross head wood screws. You'll need a 4mm drill bit for these, and a countersink (maybe 13mm) bit.
- Bolts - Stainless steel allen head M6 bolts, 40-50mm long.
- Tee Nuts - Stainless steel M6 tee nuts. You'll need a 7.5 drill bit to drill pilot holes. They go on the other side of the baffle than the driver.
^the above probably sounds obvious but it took me a while to find out this sort of sh*t!

p.s. make sure before gluing up the stepped horn that the brace next to the baffle will not obstruct bolts/tee nuts. almost made that mistake.

i've got google sketchup files for the stepped horn if anyone wants me to upload.

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Jake_Fielder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jake_Fielder Quote  Post ReplyReply Direct Link To This Post Posted: 11 April 2008 at 1:42pm
Yes please, upload the files, congrats on your build.
 
(is scetchup easy to use?)
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darkmatter View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darkmatter Quote  Post ReplyReply Direct Link To This Post Posted: 11 April 2008 at 1:50pm
sketchup is veeeerrry easy mate, you'll get to grips with it straight away, you seem to have a good eye for 3d space. it can really help to inspire you to get on with building when you see the mockup :) its made calculating volumes for the 12+1s i'm planning easier, and helped me avoid some very stupid mistakes with the stepped horn too!
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rich, ind.st View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rich, ind.st Quote  Post ReplyReply Direct Link To This Post Posted: 11 April 2008 at 2:25pm
i found a delay of 170ish pretty good with teh stepped horn, although its been a while since it was used so i'd reccomend that as a rough region to try...
music is god
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Jake_Fielder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jake_Fielder Quote  Post ReplyReply Direct Link To This Post Posted: 11 April 2008 at 2:25pm
ok cool, because i really need to graduate from using mspaint for my technical drawings! Embarrassed
 
 
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darkmatter View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darkmatter Quote  Post ReplyReply Direct Link To This Post Posted: 11 April 2008 at 3:59pm
Cheers Rich, 1.781m seems to be good, it's damn hard having hands on the volume and crossover point while sitting in my listening position and flicking polarity, I'm no octopus :P
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darkmatter View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darkmatter Quote  Post ReplyReply Direct Link To This Post Posted: 11 April 2008 at 4:39pm
Jake - only thing is sketchup won't calculate volumes for you. It can do cross sectional areas and you can go from there, or I guess you could export the file and import into a cracked autocad. I guess what I'm getting at is I don't think it's brilliant for refolding horns etc. There's no easy way to group objects and tell them how to behave when another connected object is stretched 10cm for example, so it's good for doing a mockup but more difficult when you want to have a quick play with the dimensions as you go along.

Pics...

Did plenty of dry fits to make sure I wasn't making stupid mistakes along the way:



Here you see I smoke too much - I thought the tee nuts went on the other side first of all so I routed little spaces round the driver cutout, then realized ten minutes later that this was completely unneccessary. Ah well :D


If you're routing 18mm rebates, get an 18mm bit. I used a 10mm straight cutter and had to do two cuts for each rebate to get the 18mm - loooong. Was too impatient to wait for an 18mm bit to arrive.


Air gaps? What air gaps!?


High quality wiring when I'm ere - maplins standard mains cable no less.


I didn't have any safety goggles so I innovated:



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Disco Stu View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Disco Stu Quote  Post ReplyReply Direct Link To This Post Posted: 11 April 2008 at 5:20pm
Do I spy some ADAM ARTs?
All you need to know is:
Sensitivity + Power Handling - Power Compression = Max Output

My acts:
www.myspace.com/thebowiexperience
www.myspace.com/scheisseelektronisches
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Contour View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Contour Quote  Post ReplyReply Direct Link To This Post Posted: 11 April 2008 at 10:35pm
Nice to hear you like the performance of the Stepped Horn. I was also impressed the first time I fired it up. Too bad it was a little to big for the room, so I had to sell it. The stepped horn is also an easy build, no strange angles to cut.
 
Best regards,
 
Walt
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Jake_Fielder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jake_Fielder Quote  Post ReplyReply Direct Link To This Post Posted: 14 April 2008 at 9:52am
I love the googles, safety first.
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darkmatter View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darkmatter Quote  Post ReplyReply Direct Link To This Post Posted: 14 April 2008 at 3:25pm


Sketchup file, can't guarantee correctness though!
http://members.lycos.co.uk/darkmatterdnb/WaltsSteppedHorn.skp
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darkmatter View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darkmatter Quote  Post ReplyReply Direct Link To This Post Posted: 14 April 2008 at 8:34pm
Originally posted by Disco Stu Disco Stu wrote:

Do I spy some ADAM ARTs?


Sorry I forgot to answer this! Yep, fell in love with them straight away, crystal clear and non fatiguing. Seemed almost too bright when I first got them but they've sweetened up nicely. They reveal the many flaws in my production, guess that's why I bought them thoughLOL
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