Something stirs in the Undergrowth

Dedicated to those large boxes at one end of the room
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Ray P
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Re: Something stirs in the Undergrowth

Post by Ray P » Tue May 28, 2019 10:28 pm

IslandPink wrote:
Tue May 28, 2019 9:46 pm
Everyone was surprised what was uncovered !
Maybe you should have had a metal detectorist check you over first, just in case there any hoardes of roman coins or the like secreted within...

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Wed Jun 05, 2019 7:15 pm

Well, new hearing and some re-alignment on OB's from Owston, I forge ahead.
I did some calc for the cap size in the Quasar crossover on Monday . Then I went home and put in approx. 40uF instead of the 56uF. Things got worse. Then I tried 100uF . That was fuller but not quite right .
Then I sat down and carefully looked at the roll-off of the PM6C, the roll-off of the FX120, and did a spice model including the L-pad around the Supravox and the 16R for two FX120 drivers.
Armed with that, tonight, I tried 56uF+20uF - this is much better. I will try 85uF too.

I think I made a wrong turning on this by not re-evaluating the cap size after applying the different attenuation method on the bass driver. I was just hoping the 56uF would be OK.
Now need to decide what to use for 20 or 30uF extra that will fit inside the crossover boxes... hmmm...
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Fri Jun 14, 2019 8:35 pm

Sounding like 56+30uF is the better of the two. More upper bass tone, and the soundstage is more solid and natural. I have just ordered some 22 & 33uF bipolar Mundorf caps from HFC to see if they're good enough ( they are small enough to fit in the box with the EVO oils ) , otherwise will have to bodge later to enlarge the boxes for more PP/oil.
Anyway, feeling happier with the whole thing now.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Sat Jul 27, 2019 9:24 pm

Nice to have wood stacked up in the hall again - feels right.
Kornett_parts.JPG
This is the next phase of 'Plan A'. Given that 'Plan B' is more or less finished, and operational.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Sun Jul 28, 2019 10:43 pm

More :
Kornett_parts1.JPG
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

SimonC
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Re: Something stirs in the Undergrowth

Post by SimonC » Mon Jul 29, 2019 8:15 am

IslandPink wrote:
Sun Jul 28, 2019 10:43 pm
More :

Kornett_parts1.JPG
:D :D :D :D :D

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Ali Tait
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Re: Something stirs in the Undergrowth

Post by Ali Tait » Mon Jul 29, 2019 8:48 am

Can you guess what it is yet? :D
Image[/img]

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Mon Jul 29, 2019 10:37 am

Exactly .
Double horn. Two drivers.
http://www.hm-moreart.de/101.htm
Build - one - using 5" drivers - for evaluation.
FE126eN loaned by Nick for front, 5FE120 Faital for rear.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Sun Aug 04, 2019 9:42 pm

More progress, either side of a mother visit -
Double_progress2.JPG
Double_progress3.JPG
Can't stop doing this neatly, now I have the experience. The big conical cutter with the roller on the end is a hoot.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Ray P
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Re: Something stirs in the Undergrowth

Post by Ray P » Mon Aug 05, 2019 11:28 pm

Saw this and thought of you for some reason Mark...

https://www.diyaudio.com/forums/multi-w ... packs.html

Max N
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Re: Something stirs in the Undergrowth

Post by Max N » Tue Aug 06, 2019 1:12 am

Very nice handiwork there

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Sat Aug 10, 2019 4:09 pm

Just spent about an hour puzzling over dimensions here, with a ruler and calculator. Something doesn't work out.
http://www.hm-moreart.de/101.htm
( Page 2 )
The horizontal dimensions around the bottom bends of the two horn paths ( the 53, 43, 48, 67 and the 125mm end pieces ) ultimately have an error of about 5mm when you draw everything out on the wood. Very annoying. I have had to split the difference of error into the 53mm and 43mm dimensions.
Not the first time I've had to double check things.
Weather not helping either, but I have enough variety of activities to keep me busy indoors as well as outdoors.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

izzy wizzy
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Re: Something stirs in the Undergrowth

Post by izzy wizzy » Sat Aug 10, 2019 4:32 pm

You've probably looked at this but there seem to be some angles involved in those bends so are some of these measurements involving diagonals and that's where your 5mm is when translated to flat bits of wood?

Cheers,
Stephen

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Sat Aug 10, 2019 4:57 pm

I have had a very good look at it. The panel at the back ( front face of the rear horn mouth ) is about 5.5°, so that one is in the calc coming up from the bottom panel. Elsewhere the corrections are things like the cosine of 1.5° which is so close to 1.0 , it does nothing.
Anyway, it has all been drawn out on the side panel accurately with the 13mm and 18mm thicknesses all respected as close as possible. I also measured my birch ply, and it IS 18mm !
So I do think there are errors. I have already had to correct some piece lengths by up to 3mm from the listed parts. None of this will affect the acoustic behaviour of the horn much, given the wavelength at 300Hz, where the horn tails off, but it's more about getting all the wood to fit together and be airtight.
It's not as difficult as the last horn project I did, that's for sure !
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Sun Aug 11, 2019 6:39 pm

IslandPink wrote:
Sat Aug 10, 2019 4:57 pm
I also measured my birch ply, and it IS 18mm !
:oops: Well I measured it again, and it's 17.5mm ... so this accounts for 2mm out of the 6mm discrepancy.

Meanwhile more progress. Have to call a temporary halt now, owing to visitors next weekend !
Double_more.JPG
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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