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Old 5th March 2005, 09:22 PM   #1
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Default help tuning push-push ApexJr super 8 woofer

I was frustrated getting reasonable results out of the MJK worksheets (i will revist that at some point) so we went ahead and threw together a push-push bass reflex based on the Super 8 4th order on Steve's site.

All i can measure is the impedance curve -- but i'm sure to someone more familiar with BR the shape of those 2 humps tell a lot... any suggestions on optimizing the tuning?

dave
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Old 5th March 2005, 09:23 PM   #2
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And here are the drawings from which it was built...
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Old 5th March 2005, 09:33 PM   #3
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And what it actually looks like -- only the finest scraps were used...including recycled venerred particle board from some old speaker, 40-yr old plywood, the top from a console hifi, and part of a rejected table top with inlaid marquetry (currently the back of the speaker (i think i'll move the terminals to the face you see).
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Old 5th March 2005, 09:34 PM   #4
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I think these speakers have potential... currently hooked up as an HT woofer only using the XO out of the decoder, each driver driven by a channel of a Don Stenton Signature SS amp (50W/channel).

Starting to break them in -- Frank Zappa's Baby Snakes DVD on ATM.

Once i remove the base i'll play a bit with port stuffing (i'm much more comfortable with aperiodic).

The HT Processor doesn't have enuff adjustment to turn them down enuff... i'll be breadboarding up some XOs to see what we can do to improve on that.

dave
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Old 8th March 2005, 04:09 AM   #5
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You dont have any driver specs? What a shame...

that bottom firing port is a bit strange, I would imagine the way it is configured like that makes the effective port longer than just the part that goes inside the box.
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Old 8th March 2005, 05:05 AM   #6
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Quote:
Originally posted by BassAwdyO
You dont have any driver specs?
Driver specs are in the pdfs....

dave
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Old 8th March 2005, 09:02 AM   #7
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Hmm, I can see why Chris never lets you loose on the woodwork!

Well, it looks like you nailed the alignment fairly well, the well smoothed first peak being very indicative of the higher order alignment. The second peak is a little wide, but that is probably due to slight differences in the drivers blurring the curve.


Is that impedance curve calibrated, or just relative?

That looks very like a good HT sub for the money, I would be a bit wary using it as a music sub, though, the group delay is "interesting", though I have seen worse.

So, when is Jason going to build your mic pre, so we can see some frequency measurements?
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Old 8th March 2005, 06:17 PM   #8
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Quote:
Originally posted by pinkmouse
Is that impedance curve calibrated, or just relative?
calibrated. I'm using Fuzzmeasure for OS X.

Quote:
That looks very like a good HT sub for the money, I would be a bit wary using it as a music sub, though, the group delay is "interesting", though I have seen worse.
It is all i can use it for at the moment due to XO issues. Jason came out to assemble the new XO on breadboard on Sunday, but ended up watching cooking shows instead. He wanted to do it so i left it for him... i'll do it myself now.

Quote:
So, when is Jason going to build your mic pre, so we can see some frequency measurements?
It is sitting in a box all assembled... have to assemble the mic wand & test it... the new 1.2 beta of Fuzzmeasure has a whack of updates, but all have to do with measuring so i am eagar to see what it does.

dave
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Old 8th March 2005, 09:40 PM   #9
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Default Fine Woodworking?

Sooooo, you decided to show off some of my fine woodworking. I must say you got the photo from a good angle. I am glad it is just a prototype. Maybe a can of black paint will bring the best out of that fine looking box I made? All in all it was an hour or two well spent. Besides I was just going to burn the wood anyway.

I am sure you will figure out how to make sound better than it looks. Then we can show off a nicer cabinet.
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Old 8th March 2005, 09:57 PM   #10
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Would substituting a pair of those 8" MCM woofers work okay? Looks like a good plan for me if it will.
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