Crossover - where

[Darek K]

minidsp
2+1 setup

Question is : is there a way to predict crossover ?

For now predicted graphs from REW.
Violet it is sub, magenta it is main speaker.

My plan is to "create" house curve using only Gain in minidsp in Output3 (Screenshot is from manual from minidsp page, not my setup)

And after creating crossover graph should look like this.

Is there any math knowledge where to create crossover and which slope to apply ?

If better way, insted of boosting sub gain, is to create low pass filter PEQ in input section please let me know.

Thank You

 

[DVDdoug]

I've never used the miniDSP...

Neither graph shows a crossover. There is a lot of overlap in both.

But I'd say anywhere between 50-80Hz. 80Hz seems to be almost a standard in AVRs.

24dB per octave is probably enough. The sharper the cut-offs, the less overlap (obviously) and that means there is less chance of strange phase/timing interactions. I assume the software will (automatically?) take care of any phase issues in the crossover region. I really don't know if the cut-offs can be too sharp but I don't think so as long as the DSP has enough processing power.

I am also assuming that you have access to a line-level signal to high-pass the main speakers.

 

[Devnull]

Put your measurements into MSO and let it do it's thing

 

[boxerfan88]

If in doubt, just use 80.

 

[Pareto Pragmatic]

If in doubt, just use 80.

I tried a lot, and now just go with 80.

Other than 80? I would try 60 or 65 or so, based on not much other than both are pretty smooth there. I doubt it will make a difference from 80, but maybe.

 

[dualazmak]

My post here would be of your reference and interest, I assume.
- Summary of critical factors in integration of subwoofer(s) and main woofers in our individual acoustic environments

 

[Keith_W]

Conventional advice is to high pass your main speakers and low pass your subs.

However, I have experimented with main speakers equalized down to 20Hz and low-passed subs only. The idea is that there are now two additional bass sources in your room (the main speakers) so it should give a flatter response over a wider area.

It isn't always necessary or better to high-pass your main speakers. You can try both and see which gives you a better result. Your main speakers seem to be able to go down to 30Hz, so this is something you could consider.

This is your sub's cone breakup frequency, about 170Hz. You want to low-pass your subs at least an octave below that. So ... about 80Hz.

 

[Darek K]

First, a note – this is my first consideration of speaker phase. I am newbe in this area.

I tried to imagine the operation of the subwoofer and main speaker diaphragms.

I assume that when both speakers have their diaphragms oscillating in the same direction (e.g., outward from the enclosure), the sound is amplified.

When tuning the subwoofer to the main speakers, it would be a good idea to eliminate the areas where the main speaker's diaphragm is pushed out and the sub's is pulled in.

If I'm reading the graph below (sub is blue) correctly, starting from a frequency of about 33 Hz, the diaphragms move in the same direction up to about 55 Hz. Above 55 Hz, the sub's diaphragm changes direction, and the main diaphragm continues as before.

So, it would be a good idea to cut off the frequencies above 55 Hz in the sub.
Am I thinking correctly?

 

[Keith_W]

What you see in your phase measurements are not measurements of the sub or the speakers. It is sub/speakers + room reflections, and it is very specific to where you took your measurement. The easiest way to check whether there will be phase cancellation between sub and speaker is to sum them (Trace Arithmetic A+B) or you could use the alignment tool.