3.5 way speaker design, should I put the woofers together? - Page 2 - diyAudio
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Old 15th June 2012, 01:38 PM   #11
system7 is offline system7  United Kingdom
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Visaton use a separate chamber for the woofer and bafflestep correction sub-woofer in the 3.5 way Symphonie. I'd guess they have their reasons.

The Casablanca III is a bit closer to your particular crossover points. Both would be worth exploring with Visaton's excellent BoxSim program. I found some very good results using the W300S 12" unit with their G 50 FFL dome midrange. The bigger driver is more efficient at around an impressive 90dB and has better phase alignment on a second order filter.

Of course, if you design for wallmounting bookshelf style, you can dump the second woofer anyway.
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Old 15th June 2012, 02:13 PM   #12
fpitas is offline fpitas  United States
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Visaton may have had their reasons, but the JBL Everest puts both in the same chamber:

http://www.jblsynthesis.com/download...66000%20HR.pdf

See illustration on page 13.
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Old 15th June 2012, 10:56 PM   #13
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re"you should really isolate the woofer from the mid.' - no, this is not necessary in a 2.5 way
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Old 15th June 2012, 11:01 PM   #14
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by Alvis View Post
A single box is a poor effort, you should really isolate the woofer from the mid.
passive radiator ?
Alvis, its not a midrange driver

its a 2.5way principle converted to 3.5way
do you know what a 2.5way is
or else, time to look it up
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Old 15th June 2012, 11:08 PM   #15
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by Boscoe View Post
In all honesty I think this speaker will most probably turn into a mess
not easy at all, no
and why 3.5way and not 'just' plain 3way

a lot of effort with such small drivers
may I ask, why ?

question is whether the mid dome is doing any good all, over a 'plain 2.5way design
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Old 16th June 2012, 12:16 AM   #16
sreten is online now sreten  United Kingdom
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Quote:
Originally Posted by Alvis View Post

I guarantee you will have midrange coming out the woofer despite the multiple crossovers.
Hi,

Quite frankly you have no idea what you are talking about and cannot
guarantee anything, if you understand the original question, if you don't .....

rgds, sreten.

There is no good reason to separate 0.5 way drivers in reality.
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Last edited by sreten; 16th June 2012 at 12:19 AM.
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Old 16th June 2012, 03:11 AM   #17
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And I agree with Sreten & Pete on this one although if it was me I would be using a bigger woofer for the .5. I have always liked the sound and "Big bass" of the early Japanese BIG boxes that used this design ( and they used crappy small cone high-mids and tweeters )
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Old 16th June 2012, 12:22 PM   #18
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Of course you agree with srten, he is the local authority?

I think perhaps Tinitus and Srten need an education in physics, not wishfull thinking.

When you have both woofers doing a bass compression, the mid will not be able to overcome these distortions, the power used for bass is higher, the surface area is doubles, so are the bass producing motors.

In a single driver the mid rides up and down on the woofer, aside from a little doppler effect, this more or less works, because the woofer moves in and out to from electrical signals creating the mid, the speaker is dictating the pressure responses.

Now when you add a second woofer, with no mid range riding along, this does not work well.
When both woofers compress, the air pressure rises and distorts the mid.
When the woofers move out, the vacuum created distorts the mid range.

The mid simply cannot move in it's proper range of motion with all that pressure modulation going on.

I promise.
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Old 16th June 2012, 01:10 PM   #19
system7 is offline system7  United Kingdom
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We will doubtless descend into the usual depressing diyaudio spat if this line is further pursued. I will steer us in a slightly different productive direction.

The thing to know about midrange domes is that they are VERY EFFICIENT and have dispersion to die for!

Click the image to open in full size.

They integrate BEAUTIFULLY with woofers and tweeters, but you may need to double up smaller drivers in the conventional way to match on efficiency.

I did an appraisal of the legendary Celestion Ditton 66 and AR-3A speakers, both of which use 12" bass and a dome:

Click the image to open in full size.

I just used the Visaton Casablanca III 2nd order design and optimised it for different woofers. Interestingly, the big 10" and 12" woofers aligned best on phase and efficiency (90dB!) where small woofers struggled, and celestion's third order tweeter filter aligned very well around 10kHz, but less so at lower frequencies. Truly an interesting study. I really want a dome midrange. Superb what you can do with one.
Attached Images
File Type: jpg Celestion_Ditton_66_XO.JPG (69.3 KB, 135 views)
File Type: jpg Celestion_Ditton66_Appraisal_SecondOrderFR.JPG (63.3 KB, 132 views)
File Type: jpg Celestion_Ditton66_Appraisal_SecondOrderPhase.JPG (57.0 KB, 129 views)
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Last edited by system7; 16th June 2012 at 01:23 PM. Reason: Added dispersion graph
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Old 16th June 2012, 01:29 PM   #20
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Quote:
Originally Posted by Alvis View Post
Of course you agree with srten, he is the local authority?

I think perhaps Tinitus and Srten need an education in physics, not wishfull thinking.

When you have both woofers doing a bass compression, the mid will not be able to overcome these distortions, the power used for bass is higher, the surface area is doubles, so are the bass producing motors.

In a single driver the mid rides up and down on the woofer, aside from a little doppler effect, this more or less works, because the woofer moves in and out to from electrical signals creating the mid, the speaker is dictating the pressure responses.

Now when you add a second woofer, with no mid range riding along, this does not work well.
When both woofers compress, the air pressure rises and distorts the mid.
When the woofers move out, the vacuum created distorts the mid range.

The mid simply cannot move in it's proper range of motion with all that pressure modulation going on.

I promise.
I'm sorry, but this simply isn't so.

You could use the same argument to "show" that a midbass in a small cabinet would also have modulation issues in the midrange.

Remember each bass driver would "see" half the cabinet volume, as, being identical, they'll each pressurise their own half of the cabinet exactly.
Imagine there is a dividing wall between the two chambers. When the woofers move, they each press on the wall. They have moved the same amount and occupy an equal volume of air to each other, so the pressure on the dividing wall must be the same on both sides. The forces cancel exactly and there's no movement of the wall because of this.
So if the wall does not experience any net force, why bother with it?

Doing without will yield the same results (so long as the cabinet is otherwise mechanically braced).

Chris

Last edited by chris661; 16th June 2012 at 01:32 PM.
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