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Why are coaxials so rare?

thewas

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I‘m sorry I should have said wide bandwidth anechoic room.
In that case you are right, large sized (and thus also large bandwidth) anechoic chambers are quite rare, altough some use large semi anechoic chambers which can be used with ground plane method

KEF-Reference-1-copy14.jpg


Source of image: https://www.fidelity-online.de/kef-reference-1-messungen/
 

sarumbear

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The better Geithains though at their 3-ways like 901K and 921K where just the woofer is partially covered by the "tweeter-mid-bridge" and due to the large wavelengths transmitted by the woofer doesn't cause as many problems as on their 2-ways.

RL901K-Perspektive_V1.png
What problems do you mean? Here is what manufacturer published for their 2-way passive model.

 

voodooless

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But not for the Geithains we were talking about where the 5" mid driver is crossed much lower.
Indeed. I suspect that setup works much better. Still there are some resonances to take care of, as well as the effects from the edges of the faceplate.

The BMS you can also make work.. it’s a 900 euro part, so it better bring you a useful speaker ;)
 

thewas

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What problems do you mean? Here is what manufacturer published for their 2-way passive model.

That at a range up to 2.5 kHz which their 2-way crossover a "bridge" over the midwoofer will cause measurable diffraction effects which would be clearly seen at a full spinorama and not just two smoothed manufacturer curves.
 

sarumbear

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That at a range up to 2.5 kHz which their 2-way crossover a "bridge" over the midwoofer will cause measurable diffraction effects which would be clearly seen at a full spinorama and not just two smoothed manufacturer curves.
If you have seen measurements that refute the manufacturer please share with us. Implying that a manufacturer is lying is not a nice thing to say on a forum. Besides, i cannot see much smoothing in their curves than expected. Link above.

A74E1590-40D8-4DB1-A092-C39E5BE575B7.png
 

thewas

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If you have seen measurements that refute the manufacturer please share with us. Implying that a manufacturer is lying is not a nice thing to say on a forum. Besides, i cannot see much smoothing in their curves than expected. Link above.

View attachment 161256
Don't turn around my words, I didn't imply they are lying but said that just those 2 curves don't really reveal the problems of that "bridge" over a mid woofer crossed at 2,5 kHz. Also they have obviously some kind of usual smoothing from most loudspeaker manufacturers (would guess around 1/6-1/12 octave) when you compare them to unsmoothed measurements here for example of @amirm, @hardisj and @napilopez
 

sarumbear

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Don't turn around my words, I didn't imply they are lying but said that just those 2 curves don't really reveal the problems of that "bridge" over a mid woofer crossed at 2,5 kHz. Also they have obviously some kind of usual smoothing from most loudspeaker manufacturers (would guess around 1/6 octave) when you compare them to all unsmoothed measurements here for example of @amirm, @hardisj and @napilopez
Whats different in a spinerama? It us just another way showing the frequency range on and of off-axis. Besides, it is also smoothed. You cannot use an unsmoothed chart when testing with a sine wave.

Manufacturer shows the FR of on axis and 45 off-axis. They fallow each other in the range you expect to see problems. Do you expect peaks that are less than 1/6 octave wide suddenly appear? Why would they?
 

Sancus

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Besides, i cannot see much smoothing in their curves than expected. Link above.

Really? This looks quite smoothed to me. I would expect a Klippel run on this speaker to reveal some issues. I could be wrong of course, but I really don't think manufacturer measurements should *ever* be trusted until verified by a 3rd party, preferably across multiple models.

Always default to not trusting manufacturers -- only a tiny handful have proven worthy of any trust. This whole forum is based on the fact that most manufacturers cannot be trusted to do the right thing without third party enforcement/verification.
 

JWAmerica

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I like the concept, but that bridge on the 901k is obscuring way too much of the woofer, causing reflections and diffraction. You don't even see that in lo-fi car audio.
 

thewas

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Manufacturer shows the FR of on axis and 45 off-axis. They fallow each other in the range you expect to see problems. Do you expect peaks that are less than 1/6 octave wide suddenly appear? Why would they?
If you place an obstacle in front of the driver which has similar dimension to the magnitude of the radiated wavelength you get reflections and diffraction creating secondary radiation sources and discontinuities in the radiation. https://heissmann-acoustics.de/en/kantendiffraktion-sekundaerschallquellen-treiberanordnun/

The above 0° and 45° are EQed as a compromise in the passive crossover but even there it is already obvious that the directivity is far from perfect having a big step above 3 kHz:

1635139633271.png


Unfortunately the only Geithain loudspeaker with detailed 3-party measurements are 3-ways but even there you see the discontinuities of the pure driver responses

9441-SPK-580x434.jpg


which need some significant EQing even in their passband

9441-FIL-580x442.jpg


and not perfect radiation patterns

9441-hor-580x357.jpg


ME804K_Lin_SPLdeg.png


ME804K_Lin_SPLdegF.png


Sources of above measurements:

This doesn't mean that I don't like Geithain loudspeakers, they have excellent tuning and their 3-way 901K and 921K are some of the nicest sounding loudspeakers I have ever heard, but still physics cannot be ignored, there is a reason that companies like Genelec and KEF do a huge effort to design their coaxial drivers instead of just placing a "tweeter bridge" in front of the mid driver.
 
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sarumbear

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Really? This looks quite smoothed to me. I would expect a Klippel run on this speaker to reveal some issues. I could be wrong of course, but I really don't think manufacturer measurements should *ever* be trusted until verified by a 3rd party, preferably across multiple models.

Always default to not trusting manufacturers -- only a tiny handful have proven worthy of any trust. This whole forum is based on the fact that most manufacturers cannot be trusted to do the right thing without third party enforcement/verification.
What a horrible way to live!
 

sarumbear

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I like the concept, but that bridge on the 901k is obscuring way too much of the woofer, causing reflections and diffraction. You don't even see that in lo-fi car audio.
Yet another "enthusiast" who knows more than an established manufacturer trusted by the industry.
 

aac

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I like the concept, but that bridge on the 901k is obscuring way too much of the woofer, causing reflections and diffraction. You don't even see that in lo-fi car audio.
What about genelec "the ones" speakers then?
 

sarumbear

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If you place an obstacle in front of the driver which has similar dimension to the magnitude of the radiated wavelength you get reflections and diffraction creating secondary radiation sources and discontinuities in the radiation. https://heissmann-acoustics.de/en/kantendiffraktion-sekundaerschallquellen-treiberanordnun/

The above 0° and 45° are EQed as a compromise in the passive crossover but even there it is already obvious that the directivity is far from perfect having a big step above 3 kHz:

View attachment 161295

Unfortunately the only Geithain loudspeaker with detailed 3-party measurements are 3-ways but even there you see the discontinuities of the pure driver responses

9441-SPK-580x434.jpg


which need some significant EQing even in their passband

9441-FIL-580x442.jpg


and not perfect radiation patterns

9441-hor-580x357.jpg


ME804K_Lin_SPLdeg.png


ME804K_Lin_SPLdegF.png


Sources of above measurements:

This doesn't mean that I don't like Geithain loudspeakers, they have excellent tuning and their 3-way 901K and 921K are some of the nicest sounding loudspeakers I have ever heard, but still physics cannot be ignored, there is a reason that companies like Genelec and KEF do a huge effort to design their coaxial drivers instead of just placing a "tweeter bridge" in front of the mid driver.
1) At 1kHz wavelength is 34cm. Why would a 4cm bridge (1/9 octave) have a major effect on the emitted signal?

2) Show me a standard layout speaker that has better directivity.
 

voodooless

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What about genelec "the ones" speakers then?
 
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