| planet10 |
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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| planet10 |
| And here are the drawings from which it was built... |
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| planet10 |
| 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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| planet10 |
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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| BassAwdyO |
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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| planet10 |
| quote: | Originally posted by BassAwdyO
You dont have any driver specs? |
Driver specs are in the pdfs....
dave |
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| pinkmouse |
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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| planet10 |
| 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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| SCD |
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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| mateo88 |
| 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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| jleaman |
| quote: | Originally posted by SCD
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. |
First he will probably Stuff the port : O ) next he should run them out side at a hi level to loosen them drivers up : O ) |
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| planet10 |
| quote: | Originally posted by SCD
Sooooo, you decided to show off some of my fine woodworking. |
Note to everyone -- Scott's (and Chris' for that matter) quick and nasty is typically better than my best....
(i can run circles around them both designing & drawing thou -- so it is a good symbiosis)
dave |
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| planet10 |
| quote: | Originally posted by jleaman
First he will probably Stuff the port : O ) next he should run them out side at a hi level to loosen them drivers up : O ) |
I'll be running them 24/7 once the XO is done, and i can move them off the HT setup.
dave |
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| SCD |
Well I never did get to hear them. I guess they must have potential or you would not be wasting time on them. Once we get a design worked out I can make up a real nice cabinet. I have a few furniture integration ideas that might be interesting. How about a set of short leg end tables.
On an off topic note:
I have just about finished my monblock amps I will send you a picture in the next few days. |
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| planet10 |
| quote: | Originally posted by mateo88
Would substituting a pair of those 8" MCM woofers work okay? Looks like a good plan for me if it will. |
Concept wise they should... actual box volume, and port size (if any) would likely be different
dave |
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| jleaman |
| well we got a amp we can use : O ) ill finnish the xover too..Bring it to me. |
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| jdybnis |
| How did these turn out Dave? I'm going to build a similar design. What box volume and tuning did you end up using? |
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| jleaman |
| I asked dave this morning as we were humping my stuff to my new place what a sutable t-line box would be for these apex 8" subs.. Has any one done a t-line for them ? |
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| planet10 |
| quote: | Originally posted by jdybnis
How did these turn out Dave? I'm going to build a similar design. What box volume and tuning did you end up using? |
Still in progress... i stuffed a handfull of poly into the port, and have been enjoying them in my HT.
Found out what was screwing up my MJK sims and will revist the TL for these (gotta do an extremis 1st thou)
dave |
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| jdybnis |
Thanks. Keep us up to date.
What kind of cross brace did you use between the two drivers? I'm thinking of epoxying a few hardwood dowels between the backs of the drivers. |
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| planet10 |
| quote: | Originally posted by jdybnis
What kind of cross brace did you use between the two drivers? I'm thinking of epoxying a few hardwood dowels between the backs of the drivers. |
The structural brace between all the side walls was notched so that the magnets butted up against it.
dave |
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| jdybnis |
| I'll give that a shot before I start messing with epoxying the drivers. |
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| GM |
Greets!
Just plugging the numbers into the ML-TQWT WS I get a T/S max flat with some peaking at Fb and another program calc's a bit high vent mach, so the need to 'stick a sock in it' is understandable. ;)
FWIW, last year I took a look at this driver for someone and came up with this T/S max flat Voigt style dual driver pipe, but if they built it I never heard back, so as always YMMV:
L = 54"
SO = 1.122"^2 (physically comes to a point)
SL = 130.452"^2
rp = 2.121" (for simmimg purposes, build using dual 3" dia.)
Lp = 13"
drivers down 35.38"
It sims somewhat better damped for its much greater Vb than the BR of course, but like any max flat alignment it may sound a bit 'one note' in-room with this low an Fb, so I recommend bottom firing and possibly some vent damping for it also if near a wall or corner.
GM |
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