High Order XOs

[daftcombo]

Am I the only one around here to think that the future will be made of active speakers with at least 96 dB / octave steep slopes as digital crossovers?

 

[617]

Am I the only one around here to think that the future will be made of active speakers with at least 96 dB / octave steep slopes as digital crossovers?

96db /octave doesn't give you much wiggle room for pattern matching between drivers. 24 db /octave is pretty standard.

 

[thewas]

I like the subtractive filter approach.

Interestingly my active motion feedback Philips loudspeakers from 1979 also use subtractive crossover filters.

 

[thewas]

Isn't the big downside of low orders is that the vertical directivity is really ugly?

Yes, unless they are coaxial drivers.

 

[Plcamp]

Interestingly my active motion feedback Philips loudspeakers from 1979 also use subtractive crossover filters.

I remember seeing a gent who investigated/made a subtractive analogue opamp crossover...but failed at higher order filters because the tolerance requirements tighten dramatically as order increases, and he realized that only after trying it.

On another note...Per above, I have my eye on coax drivers now. I have great trouble distinguishing what drivers will and won’t work well in open baffle, but the 10” eminence coax with a well chosen concentric compression driver might just be perfect, given I only need it to respond 250 (or higher) hz up (with dual 15” woofers supporting bass.) That crossover system will be interesting to design.

 

[puppet]

That paper refers to the xo examples as a 2nd order butterworth which should be 3db down. The examples are, in fact, a 2nd order Linkwitz-Riley as they're 6db down.

 

[BenB]

Here's something to consider regarding minimum phase and linear phase filters:

When you apply a minimum phase filter to a minimum phase device, you achieve a minimum phase result. This means that if you hit your target magnitude slopes, you have also attained your target phase characteristic.

When you apply a linear phase filter to a minimum phase device, you get something that is neither linear phase, nor minimum phase. In order to achieve the perfectly idealized linear phase result would require total compensation for the transfer function of the device to which the filter is applied (in our case, speaker drivers). It likely isn't necessary to perfectly achieve the idealized linear phase result. Once something is attenuated 40 dB, it doesn't have a big impact on the sound. It would be interesting to see a study on the impact of this, particularly for technologies that seek to achieve a particular result, like Keele-Horbach filters.

 

[puppet]

This might be an interesting read as well:
Zero Phase In Studio Monitors | audioXpress

 

[Deleted member 65]

My Gauder-Akustik Arcona speakers has this spec:

ARCONA 100
· 3-way floorstanding loudspeaker
· down-firing bass vented, high-/mid closed acoustically favourable cabinet
· symmetrized crossover with Mundorf parts
· ultrahigh slope crossover of 50 db/octave

 

[sigbergaudio]

You don't have to do all kinds of fancy things to achieve a linear speaker. Here's an active speaker we're currently developing. IIR DSP using assymetric 1.order filters for all crossovers combined with competent drivers. Note that the response in the low end isn't accurate since this is nearfield in a non-anechoic room. At least to our ears this results in a more natural sound and better crossover blend than ultrahigh slopes.

 

[UliBru]

That paper refers to the xo examples as a 2nd order butterworth which should be 3db down. The examples are, in fact, a 2nd order Linkwitz-Riley as they're 6db down.

Sorry for the confusion. It's now 15 years ago when I have written the paper.

I have created the XOs with the help of Audition function Effects - Scientific Filter - Butterworth 2nd order (this is also noted in the paper). And I have missed to check the resulting "Butterworth" for the -3 dB XO point.
Obviously the Audition function gives a wrong result. But it's my point, I have trusted Audition too much.

So here is a correction with proper Butterworth XOs:
The frequency responses and the sum look like

and the step response of the summed XOs is

This means that also the correct Butterworth XO of 2nd order does not change the content of the paper and its intention.