So is the consensus here that the tweeter on the outside works best?

I think that would be a true statement. Not only from just spit-balling and giving it a try (made a very significant improvement for me..like a new set of speakers-change), but also from all the quantitative analysis above.  Having the mids on the outside just makes optimal tuning more difficult. 

I’ve been living (happy as a clam) since last August with the mids on the outside as the speakers still sounded terrific, but..live and learn. 

@nogaps 

What  an inspirational series of posts, mind boggling!!!

I will be experimenting for sure, but are the dimensions to my speakers, in metric if you don’t mind: distance between speakers : 260 cm; distance to listener : 300 cm. 
 

I crunched numbers for a living, once upon a time. I've worked in most unit and coordinate systems out there, at one time or another. Metric is fine. I'll figure it out in the morning and get back to you. 

@ledoux1238 

Here you go.  I'll make two posts with different results as you say your between speaker distance is 260cm. I would think the calculation will be the most accurate if the between speaker distance was on-center on the panel face.  I'm guessing(?) your 260cm refers to the distance between the inside edges of the speaker. With the speakers(including trim) being about 13 inches (33cm) wide, the second post I'll make adds 33cm to your 260cm  to arrive at what I think may be your on-center distance between speakers. 

OK..this response is for 260cm on-center between speakers. 

ChatGPT question on listening triangle of 260cm x 300cm:

ok, i have a different room where I need toe-in angles. The distance between the speakers is 260cm (on center). The distance from the speaker face to the listener is 300cm. Please give the result in the same format as your last response above. Also please give the resulting toe-in angles in degrees and radians. 

Answer:

Perfect—same method, new room. Let’s run it cleanly.

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🧠 Your new geometry

• Speaker spacing = 260 cm

• Listening distance = 300 cm

• Half-spacing = 130 cm

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📐 1. Toe-in for axes crossing at your head (on-axis)

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🎯 RESULT

👉 23.4° (0.408 rad) toe-in = speakers aimed directly at your head

This is your reference point.

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🧠 Context (same physics as before)

• Your spacing vs distance is wider relative to listening distance than your previous room

• So:

  • Toe-in angle is smaller

  • But lobe sensitivity (~7° at 10 kHz) still applies

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🔵 2. Axes crossing behind your head

Reduce toe-in slightly:

Practical range:

👉 20°–22°
👉 0.35–0.38 rad

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What happens here

• Slightly off-axis to midrange

• Tweeter dominates a bit more

Result:

• smoother

• less comb filtering

• but:

  • softer center image

  • reduced vocal density

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🟢 3. Axes crossing in front of your head

Increase toe-in beyond 23.4°:

Optimal range:

👉 25°–28°
👉 0.44–0.49 rad

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Why this works

• Moves you out of 10 kHz null zones (~±7° spacing)

• Better aligns:

  • midrange beam

  • interference main lobe

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🎯 Your exact “target zone”

👉 Best starting point: ~26° toe-in
👉 ≈ 0.45 rad

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🎧 Fine-tuning window

• Adjust in ~1° increments

• Sweet spot likely:

👉 25°–27°
👉 0.44–0.47 rad

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🧠 What you’ll hear when it’s right

• Dense, locked center image

• Smooth but present treble

• No “hole” in upper mids

• Speaker disappears

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📊 Summary

 

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🧾 Final answer

👉 Calculated toe-in (on-axis): 23.4° (0.408 rad)
👉 Optimal real-world toe-in: ~26° (≈0.45 rad)

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