Basic Crossover / DSP settings for La Scala?

[Robbie010]

I have taken the plunge and bought Hypex NCORE FA123 DSP plate amps for my clone La Scala........... However, I am an absolute DSP newbie.

 

I have taken some Umik measurements of the in-room response, but I would welcome any guidance / pointers on the basic DSP settings I should implement.

 

 This is the basic graph with a Psychoacoustic smoothing applied:

 

 

I would welcome any pointers on where to start here, however, please keep it simple........

 

I was initially going to follow the guide below on setting-up a basic 3 way crossover with my specific plate amp, but I would really appreciate input from anyone who has advice.

 

https://www.diyaudio.com/forums/class-d/333733-setting-fusion-amp-3-step-step.html 

 

Are there any pre-set filters that I could use?

 

Also, I see a lot about "house curves" if anyone can enlighten me?

[Chris A]

I think this will help you dial in the SPL response using REW's EQ facility:

 

 

...and this will help to set the relative time delay of the HF channels:

 

 

There is one more part that can help (how to eliminate phase delays across the crossover interference bands), but that can wait until the above tasks are done and everything else is dialed in.

 

Chris

[Chris A]

14 hours ago, Robbie010 said:

Also, I see a lot about "house curves" if anyone can enlighten me?

House curving for home hi-fi is basically an issue that you get into with loudspeakers having direct radiating drivers, especially those loudspeakers that deliberately bounce acoustic energy off the walls, ceiling and floor just around the loudspeaker (something that muddles the soundstage imaging--like Bose loudspeakers do). Fully horn-loaded loudspeakers like La Scalas, Belles, Khorns and Jubilees are best set up with flat response on-axis, but with the microphone measuring at 1 metre in front the loudspeaker, centered on the midrange/high frequency horn.  Just toe-in the horn-loaded loudspeakers toward your listening position, and make sure that there are no acoustic reflectors between the loudspeakers (like bare equipment racks full of hard objects, or even fireplace hearths and masonry, etc.).  Then you will have a tonally balanced loudspeaker that images extremely well in-room.

 

Floyd Toole talks about the difference between measuring at your listening position vs. the close field at 1 m.  He points out that the response on-axis at 1 m should be flat, but the response at the listening position will be attenuated downward vs. increasing frequency, like the listening window and early reflections curves shown below:

 

 

The above graph talks about the "power response" of the loudspeaker.  This is nothing but the integrated off-axis response of the loudspeaker, i.e., how well the loudspeaker paints the room with acoustic energy when you're not on the loudspeaker's center axis horizontally. 

 

The directivity index, above, tells you the ratio of the on-axis response to the far off-axis response (as if you placed an omnidirectional loudspeaker in the same place as your loudspeaker and took the same measurements, then divided your loudspeaker's power response by the omnidirectional loudspeaker's performance. 

 

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So the bottom line is: measure at 1m from the (La Scala-based) loudspeaker and dial-in the EQ for flat response, then everything else will take care of itself.  With full-range controlled directivity loudspeakers (like your La Scala bass-bin + horn loaded HF loudspeakers) this will produce the right response in-room. 

 

When you see downward-sloped SPL curves vs. frequency, this is usually what happens when you're using loudspeakers that don't have controlled directivity vs. frequency, and must be EQed differently, because your hearing is not only listening to the direct arrivals from the loudspeaker, but also early reflections (which are generally not desirable for hi-fi loudspeakers, unless you have non-critical listening needs).  It's those early reflections that cause the human hearing system to perceive that those frequencies are too loud, and so you use downward-sloping SPL response curves to subconsciously compensate for all those early reflections. 

 

[The above is actually a more simplified discussion of why people use house curves in home hi-fi listening rooms.  It's not really a simple subject once you start down the path to correcting for loudspeakers that splash their energy all over the nearby objects around the room (direct radiating drivers--including woofers). Most people wind up having to use custom house curves to correct for those early reflections in those instances.]

 

Chris