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Old 1st March 2013, 11:07 PM   #21
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I used John Kreskovsky's U-Frame worksheet to compare the polar response of a midrange in a sealed box versus a U-Frame. Details here:

DIYMA Car Audio Forum - View Single Post - Improve Your Soundstage for $2

Sorry about the link to another forum, but I'm working on a car install right now and I think I might try cardioids for it.

Some things I noticed:

1) I was shocked at how small the enclosures can be. Even a cardioid that's small enough to fit in your hand had six decibels of rejection at 800hz
2) There seems to be some good reasons to use small enclosures for midrange cardioids, because of the peak in response that occurs at one quarter wavelength. So basically you 'push' the peak higher in frequency, and get cardioid radiation in the lower midrange, which transitions to dipole as you go lower in frequency

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Old 2nd March 2013, 10:44 AM   #22
graaf is offline graaf  Poland
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Quote:
Originally Posted by lolo View Post
Graaf, let's not be too fussy
who? me fussy???

it's just that ...when it walks like a duck, it quacks like a duck, it looks like a kind of a duck...

...then it must be a duck!
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Old 2nd March 2013, 01:14 PM   #23
keyser is offline keyser  Netherlands
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Patrick Baterman, I can't find anything about the Vanderstien speakers online. I also tried Vandersteen, but I couldn't find any dipoles. Do you have some more information?

With respect to the tilted cardioid enclosure, I think it might be a good idea. The floor reflection is generally the earliest and possibly also the most detrimental with respect to coloration. Decreasing its level relative to the direct sound will decrease its effect. The downside is that the ceiling reflection becomes stronger - but the advantage of a weaker floor reflection may well outweigh the disadvantage of a stronger ceiling reflection.

What I don't get about the Gradient is its side-firing woofer. Definitely makes for a more attractive (slim) looking speaker, but I think it is detrimental for the sound quality. Not a choice I would have made. If the small footprint is important (which I understand), I'd rather use a couple more smaller front-firing woofers, perhaps in a U-frame.
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Old 2nd March 2013, 01:20 PM   #24
Elias is offline Elias  Finland
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Originally Posted by keyser View Post
What I don't get about the Gradient is its side-firing woofer.

I believe the rotated dipole design comes from the philosophy the speaker is allowed to be placed against the front wall. This is a major thing in small european apartments.

Edit: Also the midrange cardioid speaks for this philosophy (no sound is radiated to wall behind the speaker)


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Old 2nd March 2013, 01:44 PM   #25
Rudolf is offline Rudolf  Germany
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Bass crossover of the Helsinki is 200 Hz. This should be completely in the modal region for smaller rooms. For the excitation of room modes it shouldn't matter much, if the dipoles are toed out 45° or toed in 45°.

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Old 18th November 2013, 01:47 PM   #26
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There *is* one interesting effect of having the dipole driver rotated 90 degrees:

1) When you rotate the dipole, you're listening in the null between the front and the back
2) In theory, the null is infinitely deep. In reality, the null is something like 10-20dB. Let's call it 15dB for the sake of argument
3) This means that when the ON AXIS sound is flat, the off-axis sound is 'bassier'

You can see it in the polars; note the rise below 300hz:

Click the image to open in full size.

I wonder if this might allow the designer to deliver a sound that has some 'kick' without it sounding too bass heavy. IE, it might sound bass heavy if you're off axis, but on axis it sounds good.
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Old 18th November 2013, 05:24 PM   #27
Juhazi is offline Juhazi  Finland
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Gradient helsinki is supposed to be placed near front wall and toed in liberately (45¤). Then bass is reflected from the front wall.

Here is original manual http://www.gradient.fi/Gradient/Down...I%20manual.pdf

Helsinki is a very exceptional speaker and it's bass is very sensitive to placement.
Gradient Revolution has dipole bass that can be rotated Revolution
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