Anyone build a bigger la scala with/for the 15pr400

[Bas Horneman]

I want to build a bass horn a la scala. But with the 15pr400 like Volti audio.

It (15pr400) mostly needs a bigger doghouse. So I was thinking 20 percent bigger la scala all round. Perhaps also with a bass reflex mod as well. As is now 'standard' on the AL6 model.

I guess I have to learn to use hornresp?

 

[Bas Horneman]

Alright — let’s calculate the new horn mouth area, throat area, and cutoff frequency when scaling up the La Scala by 20%.

📐 1. Assumptions about the original La Scala​

• Horn path length ≈ 2.6 m (102″)
• Mouth area ≈ 0.4 m² (4.3 ft² ≈ 24″×24″)
• Throat area ≈ 0.02 m² (about 3 in²)
• Cutoff frequency ≈ 104 Hz (theoretical)
  (This is derived from the mouth area.)

We scale everything by a factor of:

s = 1.20

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📐 2. New horn path length​

Already calculated:

2.6 \, m \times 1.20 = 3.12 \, m

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📐 3. New mouth area​

Area scales with the square of the linear scale:

A_\text{new} = A_\text{original} \times s^2

So:

0.4 \, m² \times (1.20)^2 ≈ 0.4 \times 1.44 ≈ 0.576 m²

≈ 0.576 m² ≈ 6.2 ft²
That’s about 30″ × 30″.

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📐 4. New throat area​

Similarly:

0.02 \, m² \times (1.20)^2 ≈ 0.0288 m²

≈ 0.0288 m² ≈ 44.7 cm² ≈ 6.9 in²

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📐 5. New cutoff frequency​

Horn cutoff frequency depends inversely on the mouth size.
The approximate formula is:

f_c ≈ \frac{c}{2\pi} \sqrt{\frac{\pi}{A_\text{mouth}}}

where (speed of sound).
If you scale the mouth area by , the cutoff scales as:

f_{c,\text{new}} = \frac{f_c}{s}

So:

104 Hz / 1.20 ≈ 87 Hz

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📋 Final Results:​

Parameter	Original	Scaled ×1.2
Horn path length	2.6 m (102″)	3.12 m (122.4″)
Mouth area	0.4 m²	0.576 m² (6.2 ft²)
Throat area	0.02 m²	0.0288 m²
Cutoff frequency	~104 Hz	~87 Hz

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✅ After scaling up the La Scala by 20%, you get:

• ~22″ longer path
• ~44% larger mouth and throat areas
• ~17 Hz lower cutoff frequency (~87 Hz instead of ~104 Hz)

If you’d like, I can also help you draft a table of new dimensions (height, width, depth) or even draw a scaled plan. Let me know!
ChatGPT...

 

[Bas Horneman]