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Old 21st March 2014, 03:22 AM   #191
freddi is offline freddi  United States
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X - I've not measured Vas but its spec-ed at 2.7 cubic feet. 2mm xmax ain't much but maybe with enough - ?


Peerless approximate range on axis
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Peerless qts, fs without break-in
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w8-12t-12p published stuff

voice coil diameter = 1 inch
Resonant Frequency (Fs)43 HzDC Resistance (Re)10.9 ohms
Voice Coil Inductance (Le)1.93 mHMechanical Q (Qms)2.57
Electromagnetic Q (Qes)0.72Total Q (Qts)0.56
Compliance Equivalent Volume (Vas)2.7 ft.≥Maximum Linear Excursion (Xmax)2 mm

Last edited by freddi; 21st March 2014 at 03:25 AM.
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Old 21st March 2014, 05:55 AM   #192
freddi is offline freddi  United States
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btw X, can you see any potential advantages to this arrangement where there's a K-slot on either side of the baffle but one slot is inverted? (the front of each cone faces the beginning of the Karlson-slot)

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Old 21st March 2014, 11:20 AM   #193
xrk971 is online now xrk971  United States
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A K slot on either side of a W frame dipole sub huh? Well I know the width of a slot in the slot loaded dipole sub affects the peak height of the resonance freq (circa 250 Hz in the plot of FR in the sims above) of the a lot chamber. Maybe the smooths that out and requires less EQ? Interesting concept - how does it sound?
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Old 21st March 2014, 11:24 AM   #194
xrk971 is online now xrk971  United States
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Quote:
Originally Posted by Z transform View Post
With respect to the cutout size, the 14x21cm baffle that Rudolf tested (post #30 on page 3 of this thread) looks perfect, great directivity results:

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Rudolf's Directivity Results

But we should ask him what his baffle thickness was.

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The "tongue" is the shape remaining after the cutout

So I would suggest making the "tongue" 14x21cm (no use reinventing the wheel- Thanks Rudolf!), with the 21cm dimension from the top of the baffle to the bottom of the slot. The rounding of the "tongue" I showed was just an idea. The rectangle may be better. As for the cutout width, I think 2 inches would be minimum.

If Rudolf is listening: What was the thickness of the baffle and what is the vertical dimension to the center of the speaker?

Z
Z,
This "Tongue" baffle cutout is interesting - I will give it a try once I get a turntable to do measurements. As it is I move the mic tripod and that is a pain but works well as I don't have an anechoic chamber so rotating the speaker may affect measurements more vs mic movement? Although if I gate the effects of room interaction can be reduce as we are concerned more about 500 Hz on up.
Thanks for the tip on Rudolf's work. He is certainly a master of the OB.
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Old 21st March 2014, 01:38 PM   #195
Rudolf is online now Rudolf  Germany
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Quote:
Originally Posted by Z transform View Post
If Rudolf is listening: What was the thickness of the baffle and what is the vertical dimension to the center of the speaker?
This was just an experiment. The baffle was 4 mm plywood. Usually I use 16-18 mm plywood, but I wanted to avoid routing the driver cutout.
Even a 12 mm baffle would hardly have changed anything in that diagram.
Driver is mounted 15,5 cm from the bottom of the baffle. But don't worry about 2 or 3 cm more or less, if you keep the distance from the driver center to the baffle top fixed.
Quote:
Originally Posted by xrk971 View Post
Z,
As it is I move the mic tripod ... ... so rotating the speaker may affect measurements more vs mic movement?
Always keep the mic and the turntable at fixed positions in the room. Preferably as far from the walls as possible/sensible. The only part moving should be the rotation of the turntable. You can't avoid reflections from the walls. But those will only change their strength, but neither direction nor timing. Gating the measurement is your friend there.

Moving the speaker or the mic through the room will move them through the room modes. And gating helps absolutely nothing against room modes.
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Old 21st March 2014, 03:30 PM   #196
Rudolf is online now Rudolf  Germany
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Quote:
Originally Posted by Z transform View Post
As for the cutout width, I think 2 inches would be minimum.
I believe the gap has to be wider than a wavelength - or at least 1/2 of it. If it is narrower, it will be as effective as a cattle grid wrt an elephant walking by.

In that logic a 2" gap would disappear/close for anything lower than 5 kHz.
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Old 21st March 2014, 03:37 PM   #197
freddi is offline freddi  United States
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re: K-slot baffle sound = don't know. That experiment was done by "Icebear". I would expect it to be a bit funkier than a H-baffle. (?)
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Old 21st March 2014, 05:15 PM   #198
hajj is offline hajj  Lebanon
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Quote:
Originally Posted by Rudolf View Post
I believe the gap has to be wider than a wavelength - or at least 1/2 of it. If it is narrower, it will be as effective as a cattle grid wrt an elephant walking by.

In that logic a 2" gap would disappear/close for anything lower than 5 kHz.
Which would also mean that for it to be effective down to 500hz, it would have to be 34 cm (or approx 13.5 inches for the SI challenged ).
If that's the case, then the gap is only a viable option for tweeters...
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Old 21st March 2014, 05:41 PM   #199
xrk971 is online now xrk971  United States
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Sounds like the full range driver needs to be in a 5 inch wide baffle suspended on its own with no additional side baffle to get in the way. Which may mean than a 2-way will not work because the cutoff is now too high for the woofer to reach up to.
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Old 21st March 2014, 09:15 PM   #200
Rudolf is online now Rudolf  Germany
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Quote:
Originally Posted by xrk971 View Post
Which may mean than a 2-way will not work because the cutoff is now too high for the woofer to reach up to.
There are thousands of 2-ways in the "box" world where the "woofer" has to reach up to 2 kHz. And most owners of those boxes believe that it works.

All those wide baffle dipoles work in a certain way. They just are compromises with a different focus. You can have a nice dipol pattern, but then you might worry about difficult crossover points. Or you can have an easy crossover, but with a compromised dipole pattern. You can't optimise both at the same time with a 2-way dipole.
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