Introduction to designing crossovers without measurement

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#24
nice reading! it has made me rethink the idea of a zobel on my current project, and possibly a bit of experimentation, just when i thought id wrapped it all up!

Re pink noise......Weems' suggests something similar IIRC, FM radio tuned into white noise, in mono mode. thats the way i check polys, as well as tweak individual tweeter levels, and to centre stereo image location.

Great little post. boxsim and a zobel awaits me!
 
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#25
Other methods...

I know Dave Dal Farra has a method without measuring, as well as Paul Carmody and myself.

DDF:
http://www.audio.claub.net/Simple Loudspeaker Design ver2.pdf

Paul:
Simulated Measurements - undefinition

My no-measuring recommendations:
Some optimization criteria... and some tips... - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com
Tips, Volume 2- The setup!! - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com
"Tips! Volume 3"... - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com
Tips! Volume 3, Section B.. Series Xovers.... - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com
'Tips! Volume 4', minimizing, evaluating, and rechecking a simulation... - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com

Allen- well stated, and well thought out.

Later,
Wolf
 
#27
Thank you for putting this together. For someone such as myself at the beginner level this will be a great deal of help especially since some of the other tutorials that I've seen tended to go over my head. My whole problem wasn't so much that I didn't understand the various components it's was more about not knowing what to use, why, and where based on the driver.
 
#28
Baffle-step response can be flatted out by glueing sound-absorbing foam to the so narrow made baffle as is possible ,the transient response improves as well ,so does sweet-spot and polar patterns,see interference and diffraction under my name for picture
 
#29
I'm starting to...get it

AllenB,

I am new to DIY and my learning curve is starting to get some traction with your clear explanations. I have avoided the software because I did not get the "what is going on and why." You have greatly helped in explaining it.

Thanks, Steve
 
#32
eric beek said:
Baffle-step response can be flatted out by glueing sound-absorbing foam to the so narrow made baffle as is possible ,the transient response improves as well ,so does sweet-spot and polar patterns,see interference and diffraction under my name for picture
Click to expand...

While attaching foam near the edge of the baffle can reduce the ripples in the response (particularly on-axis) caused by baffle edge diffraction, the basic baffle step shift in response of 6dB will always remain regardless of the type of damping material used. All you're doing is getting a little bit closer to the theoretical smooth 6dB shelf response of a sphere, with less overshoot than you might otherwise get with a rectangular baffle.

I'm sure you know that, but some people reading could possibly mistake your comments to suggest that somehow the basic 6dB shift was being reduced, reducing the need for baffle step correction, which isn't the case.

With typical edge radii of front baffles I'd also suggest that foam is only effective above about 2Khz or so, and only at frequencies where the active driver has wide enough (180 degree) dispersion to illuminate the baffle in the first place.

For a midrange driver you would probably get more reduction of baffle diffraction ripples (especially below 2Khz) by simply offsetting the driver a bit, and for a tweeter (which is where the foam would be most effective) you can more or less eliminate baffle diffraction by using a tweeter incorporating a waveguide - on many such designs little or no signal is radiated at right angles along the plane of the baffle so there is nothing to diffract from the cabinet edges at those frequencies.

Whether there is any worthwhile effect depends entirely on the directivity of the drivers - small drivers with very wide dispersion may see a significant improvement, larger and/or directivity controlled drivers won't see any useful improvement in my experience.

Certainly worth trying though.
 
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#38
If we consider the resistor that is used for attenuating the tweeter (Rs) and the tweeter itself (if we call it Rtweeter for the moment), the total signal voltage (Vtotal) will be found across the series combination of Rs and Rtweeter. The voltage across Rtweeter (Vtweeter) can be found by
Code: 
                     R[sub]tweeter[/sub]
V[sub]tweeter[/sub] = V[sub]total[/sub] x -------------
                   R[sub]s[/sub] + R[sub]tweeter[/sub]

The attenuation will be

Code: 
            R[sub]tweeter[/sub]
20 x log( ------------ )
          R[sub]s[/sub] + R[sub]tweeter[/sub]
 
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#39
Thanks for answering, but why are you taking the ratio of tweeter and total and expressed it as dB? I thought by reducing 1 dB in the context you are referring to the spl of the tweeter? or is it the ratio of voltage between the tweeter and total?
 
#40
Reducing the voltage (relative to the total) will bring the tweeter down and it can be expressed in dB. A halving of voltage will reduce the level by 6dB, which amounts to one quarter of the power. This is because the halving of voltage will also halve the current that flows from it.
 
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