Horizontal Directivity Question

[JCOAudio]

I'm building out a system in a new room (and I'm new to the hobby as well) and had a question about what type of horizontal directivity design is ideal. I was looking at March Audio Sointuva and Philharmonic BMR monitors as two ends of the spectrum.

From my understanding, the tradeoff between a tight and wide horizontal directivity is a better sweet spot vs a larger soundstage. Or, to quote from Erin's audio corner directly. "trading off soundstage width for focus/imaging precision." The other trade-off I'm struggling with more is the issue related to room intereference from a wide dispersion. In theory it makes sense, a wide dispersion means more waves interacting with the room and bouncing back on you. In practice, I'm not sure what that looks like. Here is my room:


I have a wide open entryway to the right side and left side, though I have glass doors that sit open on the left side. One is probably within that 90-80 degree angle of the speaker, but I understand that low frequencies are omni directional.

At the end of the day, what type of speaker should I look to pair with a room like this? I cannot audition either the Sointuva or the BMR monitors in person, so the subjective element is harder to test. This will mostly be used with a few people, not just one person listening.

 

[kemmler3D]

I'm building out a system in a new room (and I'm new to the hobby as well) and had a question about what type of horizontal directivity design is ideal. I was looking at March Audio Sointuva and Philharmonic BMR monitors as two ends of the spectrum.

From my understanding, the tradeoff between a tight and wide horizontal directivity is a better sweet spot vs a larger soundstage. Or, to quote from Erin's audio corner directly. "trading off soundstage width for focus/imaging precision." The other trade-off I'm struggling with more is the issue related to room intereference from a wide dispersion. In theory it makes sense, a wide dispersion means more waves interacting with the room and bouncing back on you. In practice, I'm not sure what that looks like. Here is my room:


I have a wide open entryway to the right side and left side, though I have glass doors that sit open on the left side. One is probably within that 90-80 degree angle of the speaker, but I understand that low frequencies are omni directional.

At the end of the day, what type of speaker should I look to pair with a room like this? I cannot audition either the Sointuva or the BMR monitors in person, so the subjective element is harder to test. This will mostly be used with a few people, not just one person listening.

Looks like your first reflection points will be open doors either way, so unbalanced reflections won't be as big a problem. So I think given the requirement for the wider sweet spot you should lean toward the BMRs. Just my opinion, I think both are great speakers.

 

[JCOAudio]

The diagram may be a bit unclear, but the doorway on the right side are pocket doors, so it is functionally an open space into the living room. On the left side, there is a french door on either side of the doorway, one in the corner and the other flat against that wall in the top left of the diagram. So there is only "door" on the left side of the room.

 

[kyuu]

Are the glass doors on the left limited to that 90-degree swing as indicated (and apparently hit one of the chairs?) or do they open further? If the latter, I don't think you'll have much trouble with a wide-dispersion speaker. If the former, that odd first reflection point seems to me like it will be adding fuel to may be an already acoustically challenging space. However it may or may not be an actual issue. Have you heard the difference between wide-dispersion and more narrow-dispersion speakers before? If you already have a preference one way or the other, you might be best off just running with that.

For what it's worth, I think most people prefer wider dispersion for the greater sense of "space" and "envelopment". Though of course if gnarly reflections become an issue, all bets are off.

 

[JCOAudio]

The doors sit entirely open nearly all the time. The free software just doesn't have an option for that. The one in the bottom left corner actually can't open all the way and is angled at about 45° because the built ins are too deep and the previous owner didn't think that through, but the door is behind the chair all the time.

 

[AnalogSteph]

Your biggest concerns may well be flor and ceiling reflections then (i.e. the vertical), assuming the open shelving is nice and cluttered / filled. Oh, and that'll be one tight stereo triangle either way, so some stereo expansion may be called for. Given that the required coverage is going to be maybe 30° horizontally, you can easily use speakers of relatively narrow dispersion without worry, maybe with a bit of toe-in.

BTW, I would file measurements to fractional inches under imperial punishment. Try calculating what half of 11' 11 5/8" is in a hurry.

Spoiler

Then try the same with 3.65 m.

 

[JCOAudio]

Your biggest concerns may well be flor and ceiling reflections then (i.e. the vertical), assuming the open shelving is nice and cluttered / filled. Oh, and that'll be one tight stereo triangle either way, so some stereo expansion may be called for. Given that the required coverage is going to be maybe 30° horizontally, you can easily use speakers of relatively narrow dispersion without worry, maybe with a bit of toe-in.

BTW, I would file measurements to fractional inches under imperial punishment. Try calculating what half of 11' 11 5/8" is in a hurry.

Spoiler

Then try the same with 3.65 m.

Oh I know, those measurements also are very much back of the napkin. I was just trying to put something together quickly. So it sounds like for a sitting position here with the two chairs, I'm actually fine with a narrow dispersion, but also given the open sides the very wide field would also be good. So this just draws back to the subjective preference of the tight imaging vs broad soundstage?

For a party, for instance, where you have people standing and milling around, both in this room and the adjoining room, how will those Philharmonics sound? I've heard the vertical directivity is actually quite poor, so they may actually end up being more fatiguing than something narrower? Or at that distance and use case does it not really matter?

 

[Duke]

I was looking at March Audio Sointuva and Philharmonic BMR monitors... From my understanding, the tradeoff between a tight and wide horizontal directivity is a better sweet spot vs a larger soundstage...

... for a sitting position here with the two chairs...

Of the two speakers you mention, imo the Sointuvas when set up for time/intensity trading will probably give you the best shot at having a good soundstage at both chairs.

"Time/intensity trading" is where the speakers are toed-in aggressively such that their axes criss-cross in front of the listening area. Let me try to explain why I think this setup geometry would work well in your situation:

The ear/brain system determines the location of a sound source largely by two mechanisms: Arrival time, and intensity. With normal speakers and a normal set-up geometry (little or no toe-in), for the listener in the left-hand chair, the output from the left-hand speaker arrives first (obviously), and it is also louder (partially because of proximity but also because that location is on-axis of the near speaker, or nearly so, AND pretty far off-axis of the far speaker). Since both localization mechanisms favor the near speaker, the sound images, and in particular the center vocalist, will be pulled strongly towards the left-hand speaker. Same thing for the right-hand chair location.

By using aggressive toe-in, perhaps 45 degrees, such that the speaker axes criss-cross in front of the listening area, given suitable speakers we can make a worthwhile improvement in this situation: The near speaker obviously still "wins" arrival time, but now the far speaker "wins" intensity! This is because the off-centerline listener is on-axis (or very nearly so) of the far speaker and is quite far off-axis of the near speaker, so the far speaker is actually LOUDER in the frequency region that matters most for localization. Thus the two localization mechanisms - arrival time and intensity - offset one another somewhat. You still have a good soundstage with an enjoyable spread of the instrument locations even from your two off-centerline listening locations, with the center vocalist now being in between the speakers rather than pulled strongly to the near side. This will work better with some recordings than with others, and initial setup will probably involve some trial-and-error.

The SECRET to a time/intensity trading configuration working well is this: The output from the near speaker must fall off RAPIDLY and SMOOTHLY as we move further and further off-axis. Most speakers do not have this characteristic. The Sointuvas look to me like they may work well with a time/intensity trading set-up geometry, but I would suggest asking the manufacturer if he recommends it.

Best of luck to you.

 

[Flaesh]

Time/intensity trading

The layout of the room doesn't seem very suitable(?)

Here is my room:

 

[Duke]

The layout of the room doesn't seem very suitable(?)

I'm assuming he has some leeway in speaker positioning. If the speakers could be moved forward and spread a bit wider apart, I think it could work.

And it that's not feasible, well I'd still be inclined to ask March Audio for their opinion.

 

[janbth]

By using aggressive toe-in, perhaps 45 degrees, such that the speaker axes criss-cross in front of the listening area, given suitable speakers we can make a worthwhile improvement in this situation: The near speaker obviously still "wins" arrival time, but now the far speaker "wins" intensity! This is because the off-centerline listener is on-axis (or very nearly so) of the far speaker and is quite far off-axis of the near speaker, so the far speaker is actually LOUDER in the frequency region that matters most for localization. Thus the two localization mechanisms - arrival time and intensity - offset one another somewhat. You still have a good soundstage with an enjoyable spread of the instrument locations even from your two off-centerline listening locations, with the center vocalist now being in between the speakers rather than pulled strongly to the near side. This will work better with some recordings than with others, and initial setup will probably involve some trial-and-error.

This is interesting. I have Sointuva AWGs myself, and an asymmetric setup with almost no horizontal reflections. I will experiment with toe-in to see what happens. One question that comes to mind: The frequency response of the speakers at an angle slopes a bit downwards towards the high frequencies, while on-axis it is quite flat. Won't this mean that speaker L and speaker R has a different "sound", and so - potentially - ruin the stereo effect?

 

[Flaesh]

Won't this mean that speaker L and speaker R has a different "sound"

Why? In any case, the speakers are installed symmetrically.

 

[Duke]

This is interesting. I have Sointuva AWGs myself, and an asymmetric setup with almost no horizontal reflections. I will experiment with toe-in to see what happens. One question that comes to mind: The frequency response of the speakers at an angle slopes a bit downwards towards the high frequencies, while on-axis it is quite flat. Won't this mean that speaker L and speaker R has a different "sound", and so - potentially - ruin the stereo effect?

I don't know, it depends on the specifics, but imo it's worth a try.

Ime time/intensity trading works best if the waveguide's output falls off uniformly as we move off-axis, so that the frequency response is pretty much the same but the loudness is decreased.

At this link you will find on- and off-axis data for the GedLee Summa, a fairly large speaker which was designed with time/intensity trading in mind:

GedLee LLC

Ime time/intensity works well with a constant-directivity waveguide as small as 10" in diameter, but I haven't tried it with anything smaller than that.

 

[janbth]

Why? In any case, the speakers are installed symmetrically.

What I have in mind is a non-symmetrical setup. So one speaker is further away than the other, with the far speaker pointing directly at the listener and the near speaker is at an angle. The far speaker then is flat, while the near one has a downward sloping - or tilted - spectrum.

 

[janbth]

I don't know, it depends on the specifics, but imo it's worth a try.

Ime time/intensity trading works best if the waveguide's output falls off uniformly as we move off-axis, so that the frequency response is pretty much the same but the loudness is decreased.

At this link you will find on- and off-axis data for the GedLee Summa, a fairly large speaker which was designed with time/intensity trading in mind:

GedLee LLC

Ime time/intensity works well with a constant-directivity waveguide as small as 10" in diameter, but I haven't tried it with anything smaller than that.

Thanks for the link. It seems that the Summa has some exceptional directivity properties, and is flat even when angled. That’s not the case for the Sointuva, which has more like a tilted spectrum at an angle. But I wonder if this still would be psychoacoustically «acceptable» (in lack of a better term). I will play around with angling my speakers as soon as I have the time.