A useful little diagram for understanding spinoramas

[napilopez]

When I was first wrapping my head around spinoramas, I had some trouble understanding the balance between the audibility of direct sound, early reflections, and sound power. I think this simple image from section 10.3 of the book really helped things click.

Most of us know that the higher the frequency, the more the direct sound matters, but I thought this made the balance of things more intuitive. Obviously, the balance will also be different for listening in the nearfield, where direct sound will take precedence over a larger range of frequencies. The above diagram reflects both the typical radiation patterns of speakers and typical absorption patterns of rooms.

Just something I thought I'd share that might make it a bit easier to interpret on and off-axis data as Amir starts measuring speakers and more people pay attention to speaker measurements.

 

[daftcombo]

Thanks, I didn't think about relating the sound power to bass.

 

[flipflop]

"typical domestic room or home theater"
Wouldn't these two rooms be hugely different if the latter is made competently?

 

[napilopez]

"typical domestic room or home theater"
Wouldn't these two rooms be hugely different if the latter is made competently?

What do you mean by competently?

Unless the home theater is absolutely massive (as in, the size of a regular theater), it still falls under the "small room acoustics" umbrella, I believe. The sound signature might be different in a treated home theater, but the distribution of sound components should still be roughly the same.

 

[Krunok]

What do you mean by competently?

Unless the home theater is absolutely massive (as in, the size of a regular theater), it still falls under the "small room acoustics" umbrella, I believe. The sound signature might be different in a treated home theater, but the distribution of sound components should still be roughly the same.

Heavilly treated home theater/room can easilly push distribution of those 3 factors toward typical cinema scenario.

 

[flipflop]

What do you mean by competently?

I mean everything that goes into creating a home theater: dealing with room acoustics, choosing the right shape and dimensions for the room, etc.

Unless the home theater is absolutely massive (as in, the size of a regular theater), it still falls under the "small room acoustics" umbrella, I believe. The sound signature might be different in a treated home theater, but the distribution of sound components should still be roughly the same.

So the size of the room is the only thing that matters for the distribution?

 

[napilopez]

You're both right - I was thinking more of of a home theater with some light wall treatment and furnishings.

Of course, if you treated your HT enough that it became an anechoic chamber, you would change the distribution of sound components.

But those graphs are based on typical setups. Most people don't treat their rooms and homes *that* much.

The difference discussed in the cinema graph here is more about the fact that such venues are so large that you get few 'early' reflections.

 

[Krunok]

The difference discussed in the cinema graph here is more about the fact that such venues are so large that you get few 'early' reflections.

I agree, but typical cinema is also heavilly treated.

 

[fredoamigo]

didn't I see this painting on the first edition of the book I own?

 

[pozz]

didn't I see this painting on the first edition of the book I own?

The first and third editions of Toole's book are very different. The second edition IIRC is the same as the first, and only called that due to the publisher's error.

 

[abdo123]

@napilopez

sorry for reviving this thread but damn this is some quality content right here.

for people who happen to have been blessed by having their speakers measured by the NFS, what would be the best method to apply speaker correction in this case?

I know the Olive score (PIR) encapsulate all three, should we just stick to optimizing speakers to obtain the highest PIR?

or maybe we can use the graph to draw 'boundaries' and every section of the FR curve is corrected via its most contributing factor?

 

[MZKM]

@napilopez

sorry for reviving this thread but damn this is some quality content right here.

for people who happen to have been blessed by having their speakers measured by the NFS, what would be the best method to apply speaker correction in this case?

I know the Olive score (PIR) encapsulate all three, should we just stick to optimizing speakers to obtain the highest PIR?

or maybe we can use the graph to draw 'boundaries' and every section of the FR curve is corrected via its most contributing factor?

I would take everything into consideration.

If on-axis is flat but PIR is wonky, you don’t want to make the latter look great by sacrificing the on-axis.

As for adjusting the PIR, I would suggest trying to maintain the general slope of the line, meaning if there is a dip then fill it in but don’t go changing how slanted it is in general.

If you see a resonance (bump in response across all lines) then tame those.

 

[abdo123]

I would take everything into consideration.

If on-axis is flat but PIR is wonky, you don’t want to make the latter look great by sacrificing the on-axis.

As for adjusting the PIR, I would suggest trying to maintain the general slope of the line, meaning if there is a dip then fill it in but don’t go changing how slanted it is in general.

I really want to try optimize for sound power / power index up to 400Hz like this graph is suggesting and see whether that would give better performance (far-field) than optimizing for PIR at these frequencies.

 

[Sancus]

Below ~500hz you should be EQing based on your in-room measurements anyway, EQing based on the anechoic measurements is pointless.

Above that, you have to be careful doing any EQ at all, unless there are fairly large flaws(>2-3dB). Anything less than that may even make things worse, because unit to unit variation can be substantial especially in tweeters, and there is also measurement margin of error to consider.

IMO the idea of using a bunch of low magnitude filters to optimize the score, as some posts suggest, is not good advice in general.

 

[Pio2001]

These diagrams look a bit strange to me.

Below 500 Hz, what I get is the behaviour of the room, and it has nothing to do with the sound power of my speakers.
Between 2000 and 8000 Hz, however, what I measure at the listening position is exactly the sound power of my speakers.