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Old 13th March 2011, 01:10 PM   #1
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Default whizzer and intelligibility ?

does a whizzer full range do better intelligibility than a non whizzer ?

I've always wondered about this.
Don't whizzers usually come in high, like 7khz ?


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Old 13th March 2011, 01:26 PM   #2
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I wouldn't like to speculate on the effects of intelligibility, but whizzer cones have an effect a lot lower than 7Khz, if you compare the response of the speaker with and without the whizzer cone, not just the frequencies where the whizzer is the sole source of sound.

Years ago I tested a Coral Flat 8A (8" driver with 160mm cone and 80mm horn shaped whizzer) with and without whizzer, and found the whizzer cone starts to have a large effect on the on and off axis response as low as 2.5Khz.

Specifically the presence of the whizzer cone reduced the on axis response from 2.5Khz to about 6Khz by nearly 3dB, but increased the (30 degree) off axis response by several dB, in other words the dispersion between 2.5Khz and 6Khz was greatly improved at the expense of some loss of on axis response.

However the on axis response without the whizzer actually had a +3dB shelf from 2.5Khz to 6Khz, which suggests the main cone of the driver was deliberately designed with an increased output in this range (probably due to decoupling rings) so that the response was balanced once the whizzer was in place.

Above 7Khz the response of the single main cone by itself disappeared rapidly, so above 7Khz the output is almost entirely the whizzer cone.

So technically the whizzer is only acting as a second separate cone above 7Khz, but between 2.5Khz and 7Khz it is still acting as a source of sound as well as a directivity modifier for the main cone, much like a phase plug would.

The improvement in dispersion is so great that at 4Khz without whizzer cone the 30 degree off axis response was 9dB down on the on axis response (severe beaming) while with the whizzer cone in place the 30 degree off axis response at 4Khz was only 1.8dB down from the on axis response...
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Last edited by DBMandrake; 13th March 2011 at 01:30 PM.
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Old 13th March 2011, 11:28 PM   #3
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I did an experiment with the Lowther DX55 several years ago. I progressively cut the whizzer down until it was no more. (Note that the DX55 whizzer is connected to the main cone and not the pole piece as in other designs.) Regarding "intelligibility", with the whizzer cut off, the music sounded less focused and dull but much easier to listen to for long periods of time. Where the whizzer comes in varies from design and size, but with the DX55 I reckon it was about 3-4kHz. So, hard to generalize about whizzers.

Having said the above and based on what I've heard I prefer whizzerless. However, my favorites are DX55 and Feastrex. But both are exceptions and are costly, and for under $300 or so I would definitely go with 3" whizzerless for offering single driver coherency.
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Old 14th March 2011, 02:17 AM   #4
freddi is offline freddi  United States
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here's the response, on, 30 degrees off and behind outdoors of a doped de-whizzered Fostex 164
Click the image to open in full size.
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Old 14th March 2011, 09:53 AM   #5
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Quote:
Originally Posted by DBMandrake View Post
I wouldn't like to speculate on the effects of intelligibility, but whizzer cones have an effect a lot lower than 7Khz, if you compare the response of the speaker with and without the whizzer cone, not just the frequencies where the whizzer is the sole source of sound.

Years ago I tested a Coral Flat 8A (8" driver with 160mm cone and 80mm horn shaped whizzer) with and without whizzer, and found the whizzer cone starts to have a large effect on the on and off axis response as low as 2.5Khz.

Specifically the presence of the whizzer cone reduced the on axis response from 2.5Khz to about 6Khz by nearly 3dB, but increased the (30 degree) off axis response by several dB, in other words the dispersion between 2.5Khz and 6Khz was greatly improved at the expense of some loss of on axis response.

However the on axis response without the whizzer actually had a +3dB shelf from 2.5Khz to 6Khz, which suggests the main cone of the driver was deliberately designed with an increased output in this range (probably due to decoupling rings) so that the response was balanced once the whizzer was in place.

Above 7Khz the response of the single main cone by itself disappeared rapidly, so above 7Khz the output is almost entirely the whizzer cone.

So technically the whizzer is only acting as a second separate cone above 7Khz, but between 2.5Khz and 7Khz it is still acting as a source of sound as well as a directivity modifier for the main cone, much like a phase plug would.

The improvement in dispersion is so great that at 4Khz without whizzer cone the 30 degree off axis response was 9dB down on the on axis response (severe beaming) while with the whizzer cone in place the 30 degree off axis response at 4Khz was only 1.8dB down from the on axis response...
Great information thanks for sharing. I am not sure if I should be contributing but anyway. To me it seems a whizzer is a engineering compromise for increased bandwidth and dispersion from a singer driver. That comes at the price of phase and weird resonant anomaly's. From my experience of listening to vintage drivers with and without. I never actually find satisfaction with whizzers. But I keep buying vintage drivers with whizzers. I try to keep a open mind.

I do wonder if they don't so much engineer a hump in the response to compensate for the addition of the whizzer. More likely like all drivers have a peak in the midrange where the driver efficiency peaks. And the whizzer is a solution to this. Dual field coils might be another solution. Or inductive circuits that have recently been used.

All so possible most full range drivers originally where never really designed for on axis listening where the phase inversion issues might be most annoying. A lot of whizzer coned full-rangers where designed for off axis listening. Whether they be for floor mounted radios or hifi speakers or pa speakers. I think I enjoy whizzers the most in this application. Less critical listening.

I read about the much loved Phillips 9710m driver. Has a huge mid range peak but possibly mounted on a reflex box mounted low to the floor the response in room maybe quiet even. I am not sure if they where ever intended for back loaded horns but I will attach some rare and old Phillips enclosure designs that we all might find interesting. Well the first two are. Not sure about the third. I hope this isn't too of topic but they are rare and hard to find or they where for me. I thought it would good to put them out more.

Latterly I am trying 5 to 6 inch drivers without whizzers after reading advice for another member. That a more even response can be expected.
Attached Images
File Type: jpg 9710 box A5.jpg (183.5 KB, 731 views)
File Type: jpg omnihorn.jpg (189.6 KB, 712 views)
File Type: jpg Philips-AD5200-AD4200-Open-Baffle-Plans.jpg (118.2 KB, 711 views)
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Old 14th March 2011, 12:50 PM   #6
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Default more on topic

Whizzer distortion

This is a similar thread with info. Interesting it mentions the reasons for the foam on my axiom 301,s Interestingly. My 301 have amazing treble I think. Admittedly I have ruined them with dammer. If I had it over I would never modify such a classic driver in this way whether it improved them or not. There peaky on axis in the upper mid making them flawed but the treble is so pure. I have to try them OB it might change there character totally.

This subject is on my mind presently. As I am having trouble understanding what people say on my bedroom home theater set up. So I pushing forward with new horn speakers trying to obtain better speech intelligibility. My hearing is not so good and digital satellite TV is not so good either.

Last edited by fatbattery; 14th March 2011 at 12:56 PM. Reason: some thoughts
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Old 14th March 2011, 12:52 PM   #7
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yes, thanks for the heads up.

Reminds me on the jordans (or the audience a3's) with a slight climbing response. Ted recommended sitting off axis.
I've wanted to try my a10, off axis it was commented as good from a German review. It has a scary climb of 10db from 1-2khz then stays there (similar to the 206e).

I forgot about whizzers helping dipersion. Most 8" lose directivity above 2khz.

I've been closely looking at the w8-1808 driver...........

Norman

Last edited by norman bates; 14th March 2011 at 12:55 PM.
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Old 14th March 2011, 01:26 PM   #8
IG81 is offline IG81  Canada
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Quote:
Originally Posted by fatbattery View Post
Great information thanks for sharing. I am not sure if I should be contributing but anyway. To me it seems a whizzer is a engineering compromise for increased bandwidth and dispersion from a singer driver. That comes at the price of phase and weird resonant anomaly's. From my experience of listening to vintage drivers with and without. I never actually find satisfaction with whizzers. But I keep buying vintage drivers with whizzers. I try to keep a open mind.

I do wonder if they don't so much engineer a hump in the response to compensate for the addition of the whizzer. More likely like all drivers have a peak in the midrange where the driver efficiency peaks. And the whizzer is a solution to this. Dual field coils might be another solution. Or inductive circuits that have recently been used.

All so possible most full range drivers originally where never really designed for on axis listening where the phase inversion issues might be most annoying. A lot of whizzer coned full-rangers where designed for off axis listening. Whether they be for floor mounted radios or hifi speakers or pa speakers. I think I enjoy whizzers the most in this application. Less critical listening.

I read about the much loved Phillips 9710m driver. Has a huge mid range peak but possibly mounted on a reflex box mounted low to the floor the response in room maybe quiet even. I am not sure if they where ever intended for back loaded horns but I will attach some rare and old Phillips enclosure designs that we all might find interesting. Well the first two are. Not sure about the third. I hope this isn't too of topic but they are rare and hard to find or they where for me. I thought it would good to put them out more.

Latterly I am trying 5 to 6 inch drivers without whizzers after reading advice for another member. That a more even response can be expected.
Thanks for the plans!

Troels Gravesen analysed the 9710 in depth on his website, including a whizzer-ectomy.

Philips 9710/

Scroll down to near the bottom for the comparative FR plot.

IG
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Old 14th March 2011, 02:06 PM   #9
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Quote:
Originally Posted by norman bates View Post

I forgot about whizzers helping dipersion. Most 8" lose directivity above 2khz.

I've been closely looking at the w8-1808 driver...........

Norman
Here are some measurements I took of a modified Coral Flat 8A about 8 years ago. From memory taken at about 1 metre with the speaker and mic about 0.7m off the floor.

They are slow sine swept narrow band "warts and all" measurements with no 1/3 octave smoothing, windowing or other niceties, and taken indoors mounted non-flush on a fairly crude baffle, so there are both baffle diffraction effects and floor bounce effects in the measurement.

In particular the notches at 650Hz and 1500Hz are floor bounce cancellation and should be ignored, however the notch at about 2.6Khz is an actual notch in driver response due to an "ill advised" un-removable modification, which is another story...

Red is on axis, purple 15 degrees off axis, blue 30 degrees, cyan 45 degrees.

What I find interesting is that despite being an 8" driver the 30 degree off axis response is good to at least 4Khz - about twice what you'd expect from a single 8" cone, so the whizzer really is making a difference. At 45 degrees there is a large drop off.

I did similar measurements on a de-whizzered version of the driver as I mentioned in my previous post, unfortunately I either didn't save them or I've lost them

On axis response from 3Khz to 8Khz (the usual problem range for whizzer cone drivers of this size) is remarkably flat. The peaks around 10-12Khz are resonances of the aluminium dome dust cap, and go away if that is removed.

The notch at 2.6Khz is due the relative phase shift between the two cones, and in their original state the drivers only had a small benign dip in this region, however after coating the whizzer cone with a rubber and carbon compound the notch formed. It is audible, and adds a slight nasally sound.

Moral of the story, DON'T coat the whizzer cone with anything...at least on Coral drivers...on the other hand, applying a similar coating to both sides of the main cone considerably improved the flatness of the response from 3-8Khz over the original, which was somewhat peaky.

I also experimented with small foam adhesive strips stuck to the rear of the main cone near the perimeter, and this made a big improvement both to these drivers and a pair of Flat 8 Mk 2. Unlike coating mods the foam strips are easily removable, if you don't leave them on for months.... after that they do tend to bond fairly securely - 8 years later they are well and truly stuck and could only be removed by slicing them off.

I'll post more graphs in following posts...
Attached Images
File Type: jpg Spectrum 14032011 125216 p.m..jpg (244.5 KB, 688 views)
File Type: jpg Spectrum 14032011 125225 p.m..jpg (241.5 KB, 111 views)
File Type: jpg Spectrum 14032011 125235 p.m..jpg (254.5 KB, 107 views)
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Last edited by DBMandrake; 14th March 2011 at 02:10 PM.
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Old 14th March 2011, 02:06 PM   #10
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great article, thanks.
not what I expected, but makes sense.

I think the flat 8" has better dispersion than the deeper funnel cones nowadays.

My friend at work wants to play with the grs repalcement for the b20, but ghost in a tweet 6db above 5khz on a diy phase plug.
Godzilla didn't like it (grs), too scratchy (mixture of goo to paper off).

Too bad, if you advertise it as a replacement, I'd expect same cone / magnet / surround.

That whizzer vibrating can really fight with the cone causing + and minus frequencies.
I've always liked a bit of poly fill down where whizzer attachs to the cone on b20.

Norman

Last edited by norman bates; 14th March 2011 at 02:15 PM.
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