Takenaka Multiflare speaker build: results - diyAudio
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Old 16th February 2009, 04:54 PM   #1
schro20 is offline schro20  United States
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Default Takenaka Multiflare speaker build: results

I though some here might be interested in the Multiflare designs of Mr. Takenaka. Let's start with a picture of the final project:

Click the image to open in full size.

and a closeup (I just love those cones...)

Click the image to open in full size.

I got intrigued by the spiral loudspeaker ideas of Mr. Takenaka some time ago (http://www3.ocn.ne.jp/~hanbei/eng-intro.html). After acquiring some of the drivers he used, in particular the PARC Audio DCU-F101W
Click the image to open in full size.

I went about and built the HMF-160
Click the image to open in full size.
(though I changed the measurements to work with 3/4in wood).

This is what he calls the Multiflare design and has evolved quite a bit from the original spiral ideas.

Well, they sound fantastic! The drivers are extremely nice and the box works very well too. They are clear and transparent. No tendency to boom. Of course they are small, so they can only go so loud (plenty for the bedroom where they are now). The bass coming out is astounding. Of course it's limited given the size, but for that size it does incredibly well. I have not yet played with any filters and there are some issues with the high frequencies. Here are some ARTA measurements. First the impedance plot:
Click the image to open in full size.

The lower bump on the left is due to the port on the back. I am not sure what to make of the tiny bump to the right of the main resonance...

Step response looks great (small amount of overshoot, so not critically damped; worth correcting for?)
Click the image to open in full size.
(sorry about the phase inversion)

Finally the frequency response (it doesn't have absolute calibration, so pay no attention to the absolute SPL numbers...) both gated and ungated at 50cm out
Click the image to open in full size.

As you can see there is a serious problem peaking at 12kHz (the bump goes from 8 to 16kHz at a good 8dB). There is also the gentle rise in the gated response (though this may have to do with gating itself). Ignoring the bumps on the combined response measurement it looks reasonably flat starting at about 80Hz.

If anyone has any thoughts/suggestions on possible correction networks to tame this... I'd be very interested. I have a Behringer DEQ and figured I will do some simulations first to see what makes the most sense.

All in all though I am very impressed with this design straight out from the gate.

For more images and also some more ARTA measurements check out http://picasaweb.google.com/schro20/...eat=directlink

Peter
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Old 16th February 2009, 05:49 PM   #2
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Pretty

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Old 16th February 2009, 08:19 PM   #3
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Now there is about the finest example of baffle step I've seen lately. Starts at 600Hz ends at 300Hz. Apply 4dB of BSC and you are flat to 80Hz. It's hard to tell what is going on below 100Hz because of all of the room interaction.

There is very little rising response. The big peak at the top shouldn't be much of a problem. It is probably only on axis and a little toe-in will fix it. I would worry about the peak at 3kHz. This will make to speaker somewhat forward. I would much rather see a shallow dip here (BBC dip). Perhaps you can notch it out?


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Old 16th February 2009, 08:47 PM   #4
schro20 is offline schro20  United States
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Default baffle step: baffled!

Quote:
Originally posted by Bob Brines
Now there is about the finest example of baffle step I've seen lately. Starts at 600Hz ends at 300Hz. Apply 4dB of BSC and you are flat to 80Hz.
Dear Bob,

how can you tell? What sort of feature are you looking at in the graph that makes you say this?

When you say "4dB of BSC" what corner frequency? The baffle width is 16.5cm. Standard formulas I can find suggest f_3 to be 700Hz. The other dimension is longer suggesting that f_3 might be lower in practice which meshes well with what you say. I just wonder how you see it in the graph...

peter
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Old 17th February 2009, 12:26 AM   #5
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Peter,

Do this: Run a trend line from 100-300Hz. Now run a trend line from 1kHz to 8kHz ignoring the 3K bump. Finally, run a trend line through the slope between them. You have defined the BS in your real life case.

OK, I only looked at our graph for a minute or so. Do the above and tell me what the F3 point is.

Bob
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Old 17th February 2009, 01:47 AM   #6
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Like this Bob?

dave
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Old 17th February 2009, 03:03 AM   #7
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Yes, that's the idea. I trended the transition a little flatter, which would hav put F3 a bit higher, but eyeball is eyeball.

Bob
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Old 17th February 2009, 01:39 PM   #8
schro20 is offline schro20  United States
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Quote:
Originally posted by Bob Brines
Yes, that's the idea. I trended the transition a little flatter, which would hav put F3 a bit higher, but eyeball is eyeball
Yes, me too. I get the point though. I guess that's why one has to experiment a bit. Luckily that's easy to do.

Will report back when I have some experiments under my belt.

Peter
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Old 17th February 2009, 02:10 PM   #9
chops is offline chops  United States
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I love this design... Decent sized enclosure, simple, clean, straight to the point. Great wood working skills too I might add.
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Old 17th February 2009, 03:20 PM   #10
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Quote:
Originally posted by Bob Brines
Yes, that's the idea. I trended the transition a little flatter, which would hav put F3 a bit higher, but eyeball is eyeball.
For the transition line, i drew a 6 dB/octave fall-off and then placed it.

dave
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