I am wondering if anyone could explain the principle behind why a larger driver seems to beam upper frequencies. I just want to understand technically what this effect comes from!
I have been playing with a Stephens Tru sonic FR120 full range driver (12") running with a 15" OB and I have enjoyed what it does in the midrange (sounds lovely, smooth and flat) but it beams the highs. It sort of gives the cupped hands effect...
It rolls off steeply at 10k, nothing much after that so I am looking for recommendations on filling in the top end (tweeter? supertweeter?)
Is this rolloff contributing to the beaming?? not sure...
I have been playing with a Stephens Tru sonic FR120 full range driver (12") running with a 15" OB and I have enjoyed what it does in the midrange (sounds lovely, smooth and flat) but it beams the highs. It sort of gives the cupped hands effect...
It rolls off steeply at 10k, nothing much after that so I am looking for recommendations on filling in the top end (tweeter? supertweeter?)
Is this rolloff contributing to the beaming?? not sure...
Attachments
I'm a little fuzzy on the "why", so I'll let a guru answer that part.
But these might help:
http://www.webervst.com/blocker.html
Cheers!
But these might help:
http://www.webervst.com/blocker.html
Cheers!
mrkahn said:
It rolls off steeply at 10k, nothing much after that so I am looking for recommendations on filling in the top end (tweeter? supertweeter?)
Is this rolloff contributing to the beaming?? not sure...
Only directly on axiss
If you listen off axiss it will roll off long before that
Im no expert, but beaming is loss of dispersion, which ofcourse is offaxiss, and could also be seen as a change in the polar response pattern
It would cause offaxiss phase issues
Its closely related to size
And shape and weight
Also size of voicecoil seems to be important
Voicecoil inductanse matters
Mind you, beaming and the unpleasant "shouting" is not the same thing...well, I dont think so, or maybe it is related
mrkahn said:I am wondering if anyone could explain the principle behind why a larger driver seems to beam upper frequencies. I just want to understand technically what this effect comes from!
As the frequency increases and the wave lengths shrink relative to the driver diameter, there's more phase difference in off-axis positions so they sum to lower magnitude than when in-phase.
For example, think about what happens when two points on the driver are half a wave length apart. If you were infinitely far from the speaker 90 degrees off-axis the sound would cancel completely.
FWIW... Beaming is mainly due to the size of the driver. The driver starts beaming when it's size becomes comparable to the wavelength of the frequency being radiated. That's why tweeters are small .
Shouting should be due to cone breakup or other mecahnisms where the response breaks up with narrow peaks that cause exaggeration of certain (usually) upper harmonics . Wide band resonance could be tamed but narrow band break up is hard to compensate or remove.
Shouting should be due to cone breakup or other mecahnisms where the response breaks up with narrow peaks that cause exaggeration of certain (usually) upper harmonics . Wide band resonance could be tamed but narrow band break up is hard to compensate or remove.
Re: Re: why do larger drivers beam upper frequencies?
Yes, sort of, no, no, notinitus said:
Its closely related to size
And shape and weight
Also size of voicecoil seems to be important
Voicecoil inductanse matters
That cylimder in front of the driver isn't going to help... you should champher the front of the holse so that the driver holes opens up at 45 degrees. Or front mount the mid-tweeter.
Highs start to beam at higher frequqcies because of combing effects. When the size of the driver is large compared to the wavelength and coming from all surfaces of the cone you get lots of varting path lengths hich cause cancellation. On axis path lenths are symettrical.
Similar to this:
dave
Highs start to beam at higher frequqcies because of combing effects. When the size of the driver is large compared to the wavelength and coming from all surfaces of the cone you get lots of varting path lengths hich cause cancellation. On axis path lenths are symettrical.
Similar to this:
dave
Thank you all for your knowledge and help!
It seems to me that a large fullrange has problems... since the FR120 rolls off the highs anyway, the best solution to all the problems it presents is to run a tweeter above the fullrange (so much for fullrange)
Not exactly what I wished for but to solve this drivers faults, I must not ask it to reproduce anything above ???hz
What a strange driver to manufacture as a fullrange huh? What are its ideal applications?
There is definitely an awful off axis rolloff... I will measure this weekend to see what it is.
You really have an opportunity to learn more from a problematic driver than an ideal one... I am having a blast!
It seems to me that a large fullrange has problems... since the FR120 rolls off the highs anyway, the best solution to all the problems it presents is to run a tweeter above the fullrange (so much for fullrange)
Not exactly what I wished for but to solve this drivers faults, I must not ask it to reproduce anything above ???hz
What a strange driver to manufacture as a fullrange huh? What are its ideal applications?
There is definitely an awful off axis rolloff... I will measure this weekend to see what it is.
You really have an opportunity to learn more from a problematic driver than an ideal one... I am having a blast!
There is no such thing as a 10 octave FR.
Keep on mind 2 things:
1/ back in the days when these were made, what was considered as required for high fidelity was something like 50-15k, They were happy to get the big drivers up to 12k or so.
2/ if you can get the XO high enuff (or low enuff) they become much less objectionable... in a situation like this you wouls use just a single cap.
dave
Keep on mind 2 things:
1/ back in the days when these were made, what was considered as required for high fidelity was something like 50-15k, They were happy to get the big drivers up to 12k or so.
2/ if you can get the XO high enuff (or low enuff) they become much less objectionable... in a situation like this you wouls use just a single cap.
dave
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