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Old 8th May 2008, 05:01 PM   #1
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Default Whizzerless Pioneer B20?

Has anyone measured the frequency response of these drivers sans whizzer. The graph provided by Parts Express shows some nasty dips past 5khz, I'm assuming caused by the whizzer.
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Old 8th May 2008, 05:31 PM   #2
badman is offline badman  United States
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I've been thinking about this cone as an interesting candidate for acoustical filtering. Since there's been so much work with adding a coax tweeter on a phase plug, why not(edit) cover the cone with some light absorbent felt to reduce the influence of horn loading the tweet.

One could conceivably tame the top end sufficiently to be happy with just the acoustical rolloff, so eliminate both the hornloading of the tweet via the fullrange cone, but also the ugly high end stuff. This would obviously include removing the phase plug (ack, I meant whizzer! edit).

Some people have put serrated edges on whizzers, but that's a bandaid for outdated whizzercone tech. Another bandaid for whizzers is to lightly stuff some absorbent material (dacron) between whizzer and main cone, to damp the whizzer and soak up any energy reflected between the whizz and main cone.
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Old 9th May 2008, 04:45 AM   #3
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That's basically what I was talking about; since most people are removing the dome and installing the phase plug, why have a whizzer? I always thought the whizzer was there to hornload the dome/dustcap - I never thought the whizzer acted as a tweeter.

I've eliminated the whizzer from some Ratshack 1354's to good effect, as well performing the hole-in-dome mod - yes this reduces the treble response, but made a big improvement in the upper mids.

I'd like to know what the response curve looked like just for the sake of knowing where to tie in a tweeter. The specs on the Pioneer B20s boast a response out to 17khz, but from what others have posted, that's very unrealistic. Seeing the response gragh over at PE suggests everyone has a hard time with those ugly peaks and dips past 5Khz.
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Old 9th May 2008, 01:56 PM   #4
GM is offline GM  United States
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If I'm following ya'll, what you want to do is damp the whizzer's bell modes that are designed in to offset losses due to industrial style speaker grills in PA apps and/or the typically high absorption coefficient of a vehicle's interior, so for HIFI apps, knead it between your fingers to reduce its stiffness to personal 'taste'. If over time you want to add some/all of it back, (multi) coat them as required with the cheapest, 'max hold' hairspray you can find.

GM
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Old 9th May 2008, 03:00 PM   #5
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How drastically would kneeding the wizzer till soft change the measured FR?

I wonder how the stock vs soft vs stiffened wizzer B20 would measure differently?

Fortunately it sounds good, as is, to me with just a piezo rolled in. I like the look of the ragged response curve. I think it's cool.

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Old 9th May 2008, 03:08 PM   #6
pjanda1 is offline pjanda1  United States
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Quote:
Originally posted by GM
If I'm following ya'll, what you want to do is damp the whizzer's bell modes that are designed in to offset losses due to industrial style speaker grills in PA apps and/or the typically high absorption coefficient of a vehicle's interior, so for HIFI apps, knead it between your fingers to reduce its stiffness to personal 'taste'. If over time you want to add some/all of it back, (multi) coat them as required with the cheapest, 'max hold' hairspray you can find.

GM
Interesting. Are you suggesting that a lossy, sort of pliant whizzer would be better? Even those designed for hi-fi apps (the new Seas fullrange comes to mind), appear to be shaped to be as stiff as possible. I've always wondered about my Hemp Acoustics whizzer, which is comparatively straighter (though still curved) and less stiff than the shape more commonly seen, like on my RS 40-1285D (to which the Seas appears more similar).

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Old 9th May 2008, 07:21 PM   #7
Kensai is offline Kensai  United States
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I don't know about whizzerless, but I have solved my small, niggling doubts about the EnABLed B20s. Its so obvious that its kind of embarrassing to admit. I had been using them OB before they got the P10 treatment, and then popped them right back in after. Detail and clarity were phenomenal, but I was getting weird sorts of "vortex" feeling moments and bits of sound suckout, mostly in the near field, but since they are my office speakers, that's where I am 95% of the time I'm using them. The reason? The EnABLing was only applied to the face, not the back, so the front and back wave were much more different than alike after the treatment, and their interaction was what caused the anomalies I was hearing. I swapped them into the sealed cabinets in the living room (like I had always intended to, eventually), and now they sound like the living room rig with a touch more bass, and a nice, open soundstage that blows the entire front off my living room with the right source.

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Old 9th May 2008, 08:13 PM   #8
GM is offline GM  United States
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Quote:
Originally posted by Godzilla
How drastically would kneeding the wizzer till soft change the measured FR?
Well, it's been years now since I did it and can't currently measure them again, but just propping them up on the floor, the OEM unit is very harsh to my ears while the kneaded one sounds much smoother and not so extended. It definitely needs a super tweeter. Anyway, the kneaded one is pretty soft, more like heavy cloth than starched paper.

GM
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Old 9th May 2008, 08:24 PM   #9
GM is offline GM  United States
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Quote:
Originally posted by pjanda1

Are you suggesting that a lossy, sort of pliant whizzer would be better?
Better to me in the case of B20s, most old RS 'FR' drivers and their ilk. Again though, you should only do it enough to suit your ears, which may mean just working the edge of the whizzer to damp its bell modes a bit.

That said, you can go in the other direction and use the cheap hairspray or super thinned shellac on the main cone to stiffen it up to sound more like the whizzer.

WRT whizzered HIFI drivers, obviously, if it sounds fine as is, then don't fix what ain't broken........

GM
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