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Author Topic: Back to Speakers! And so it begins... again! Madisound BK-16 Fostex fe166 kit.  (Read 37266 times)

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arnaud

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Re: Back to Speakers!!! And so it begins... again
« Reply #50 on: March 10, 2013, 01:57:31 AM »

Now I have no excuse not to try a simulation of the horn loading effect!

http://www.madisound.com/pdf/fostexcabs/Fostex%20BK16%20Cabinet.pdf
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arnaud

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Re: Back to Speakers!!! And so it begins... again
« Reply #51 on: March 10, 2013, 10:35:35 PM »

There you go, had a little fun simulating these and here's what I got for a start  :)p1. Note that these are for bare wall enclosure (what's the thickness of the stuffing you use marv and where is it located about?), no room reflections apart from floor (speaker elevation ~10cm), no speaker cone modes (just a planar surface with free air resonance at about 50Hz), assumed perfectly rigid enclosure.

This is the A-weight SPL at about 1.5m in front and to the side of the speaker (at ~80 cm height), the black curve shows the speaker pretty much unbaffled:


Marv, as you suggested (can't beat DIY guys to figure these things out before the engineers lol), at least some of the resonances in bass/mid-bass region at due to the horn loading, here are some contour plots of SPL at ~80Hz, 140Hz, 235Hz, 315Hz. That could help to decide on favored glasswool placement (note that without glass wool it probably sounds nasty with the horn mouth output as much if not more energy than the cone itself at these frequencies):





Finally, here's some SPL contour plot outside the enclosure at 1.1kHz to get an idea of the directivity pattern (includes floor reflections):

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Marvey

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Re: Back to Speakers!!! And so it begins... again
« Reply #52 on: March 11, 2013, 05:11:56 AM »

Wow, excellent! You have finally made something useful with all those colors.  :P

I deleted the 1/6 octave measurement on right speaker (the one located further from any walls), but I can tell you the following:
  • Notable peaks were measured at 85Hz, 150Hz, 250Hz, and 1.7kHz. The simulation is incredibly close for the bass. The calculated theoretical peaks past the cloud region past 300Hz tend not to be strongly seen in the real world - I am not sure why - I've noted this goes for open baffle designs as well.
  • Stuffing only in the area behind and the small crevice directly below the driver. Too much stuffing takes away from the dynamics of the speaker.
  • The speakers on are stands, elevated about 10cm above the floor.
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fishski13

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Re: Back to Speakers!!! And so it begins... again
« Reply #53 on: March 11, 2013, 05:21:21 AM »

Dave D./planet-10 of frugalhorn recommends CAT5, especially single runs of 24awg if you want to increase the output impedance of the amp a skosh to help tame any peaky upper-mids and add a little warmth in the mid-bass.
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ultrabike

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Re: Back to Speakers!!! And so it begins... again
« Reply #54 on: March 11, 2013, 06:43:52 AM »

This is what I found about the frugalhorns (dimensions starting on page 4):
http://www.p10hifi.net/FH/downloads/frugel-hornMk3-1v0-250212.pdf

(In response to this by Arnaud)
« Last Edit: March 11, 2013, 06:49:33 AM by ultrabike »
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Marvey

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Re: Back to Speakers!!! And so it begins... again
« Reply #55 on: March 11, 2013, 07:48:22 AM »

Applied the final fourth coat of Tung oil today, after burnishing with steel wool. (Sanded each in-between coat with 400grit sandpaper). Polished with rags. Last step will be to apply oil/wax for a final hand polish. My crappy low light slightly OOF pictures don't do the finish justice. Tung oil is not quite like lacquer. Instead, the oil hardens into a resin that is more into the wood rather than over it. This process probably takes a lot more effort than the old Japanese folks high on fumes working on the TH900.

The right speaker baffle has a more interesting grain pattern than the left. The panels reflect light differently depending upon the angle. The stands are the same wood, but not treated yet.

EQ settings tell me a supertweeter should solve a few things, if I can integrate it the right way.
« Last Edit: March 12, 2013, 12:16:29 AM by purrin »
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Hroðulf

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Re: Back to Speakers!!! And so it begins... again
« Reply #56 on: March 11, 2013, 08:19:59 AM »

All this speaker talk makes think twice about planning a KGSSHV as this years main audio project.

Btw, what about genre bandwidth with a wide-bander? I'm actually thinking of building a 3 way floorstander.
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arnaud

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Re: Back to Speakers!!! And so it begins... again
« Reply #57 on: March 11, 2013, 08:50:00 AM »

Wow, excellent! You have finally made something useful with all those colors.  :P

I deleted the 1/6 octave measurement on right speaker (the one located further from any walls), but I can tell you the following:
  • Notable peaks were measured at 85Hz, 150Hz, 250Hz, and 1.7kHz. The simulation is incredibly close for the bass. The calculated theoretical peaks past the cloud region past 300Hz tend not to be strongly seen in the real world - I am not sure why - I've noted this goes for open baffle designs as well.
  • Stuffing only in the area behind and the small crevice directly below the driver. Too much stuffing takes away from the dynamics of the speaker.
  • The speakers on are stands, elevated about 10cm above the floor.

Marv, thanks for the comments, indeed the speaker simulation feels much more rewarding than headphones because you can get sensible results with pretty much just a geometry amd basic driver mechanical properties. For headphones, it is so much trickier and without real material data and other physical properties, it's just a crap shoot to be anywhere close to real results (still is extremely valuable to get a handle on the physics though and key parameters, I learned a great doing stat diy simulations).

For the resonance at 1.7kHz, I wonder if it may be the first cone breakup? It's rather flexible fiber cone it appears so I wouldn't surprised to start seeing these from the midrange up. I could also investigate that further with a more detailed cone model (really just used a rigid piston with tuned Fs and arbitrary damping in the stuff I posted above because I was mainly after the horns resonances).

It could get even more interesting actually... If can convert the geometry to a parametric model, then an optimiser would automatically search for the optimal geometry to reach a particular target. It would take some effort on my side to setup the optimization, but that could be rewarding!
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Anaxilus.

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Re: Back to Speakers!!! And so it begins... again
« Reply #58 on: March 11, 2013, 08:51:13 AM »

Nice!  Worked out well.

The exposed plywood edges and contrast bugs me though.
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Marvey

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Re: Back to Speakers!!! And so it begins... again
« Reply #59 on: March 12, 2013, 11:58:00 PM »

EQ settings
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