New design for small floorstanding speakers with the widest possible frequency response | post-ideas.com

Here is a design concept for loudspeakers that transmit linearly from 20 Hz to 40 kHz and are no wider than 200 mm and no higher than 1000 mm.

Designing loudspeakers with linear frequency response from 20 Hz to 40 kHz and physical constraints of 200 mm width and 1000 mm height is a high-end and demanding challenge, especially since:

* 20 Hz reproduction at high fidelity generally requires large enclosures.
* 40 kHz extension demands highly capable tweeters (typically ribbon, AMT, or beryllium dome types).
* Linear response implies a flat ±1–2 dB deviation across the entire range, which is tough to achieve in real rooms.

Below is a feasible design concept within those constraints.

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Physical Constraints

* Max Dimensions:

* Width: ≤ 200 mm
* Height: ≤ 1000 mm
* Depth: Not limited (we’ll assume \~300–400 mm for optimal internal volume)

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Driver Selection and Layout

1. Tweeter – Extended High-Frequency Performance

* Type: Air Motion Transformer (AMT) or ribbon tweeter
* Specs:

* Frequency range: 2.5 kHz – 40 kHz+
* Example: Mundorf AMT U.Series / RAAL 70-20XR
* Mounting: Vertically aligned at ear height (\~900 mm from floor)

2. Midrange – Accuracy and Dispersion

* Type: 3.5" to 5.5" midrange
* Specs:

* Frequency range: \~200 Hz – 2.5 kHz
* Example: Scan-Speak 12M Revelator or SB Acoustics Satori MW13

3. Woofer(s) – Deep Bass Reproduction

* Type: 6.5" – 8" long-throw woofers, possibly multiple in series/paralleled
* Specs:

* Frequency range: \~20 Hz – 200 Hz
* Example: SEAS L26ROY, SB Acoustics SB29NRX75-6
* Configuration:

* Dual 6.5" or 8" woofers in a vented or transmission line cabinet

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Enclosure Design

Type: Hybrid

* Cabinet Sections:

* Sealed mid/tweeter chamber
* Vented or transmission line lower chamber for bass
* Volume Target:

* Woofers: \~40–60 liters
* Material: 18–25 mm MDF or birch ply with internal bracing

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Crossover Design

3-Way Active or Passive

* Recommended: Active DSP-based crossover (e.g., miniDSP SHD, Hypex FusionAmp)
* Crossover Points:

* Woofer to mid: \~200 Hz (4th-order LR)
* Mid to tweeter: \~2.5–3 kHz (4th-order LR)
* Features:

* Time alignment
* Room EQ
* Phase correction

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Expected Performance

| Metric | Target |
| --------------- | -------------------------------- |
| Frequency Range | 20 Hz – 40 kHz (±2 dB in-room) |
| Sensitivity | \~85–90 dB/2.83V/m |
| Max SPL | 100–105 dB @ 1m |
| Impedance | 4–8 ohms nominal |
| Directivity | Controlled horizontal dispersion |

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Optional Enhancements

* Sub-bass reinforcement: Add passive radiator or dedicated subwoofer to handle 20–30 Hz cleanly
* Waveguide: Integrate tweeter waveguide to control dispersion and improve phase alignment
* Baffle Shaping: Curved or chamfered edges to reduce diffraction

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Summary Bill of Materials (BOM)

| Component | Example |
| --------- | ------------------------------------------- |
| Tweeter | RAAL 70-20XR (\~\$500) |
| Midrange | Scan-Speak 12M Revelator (\~\$300) |
| Woofers | SEAS L26ROY ×2 (\~\$400 each) |
| DSP Amp | Hypex FA123 (\~\$800) |
| Cabinet | Custom MDF with bracing (\~\$300 materials) |

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To determine the exact crossover values for your loudspeakers (3-way with ribbon tweeter, midrange, and dual woofers), we must first establish:

System Configuration Overview

* Drivers:

* Ribbon Tweeter: likely suited for > 3.5 kHz.
* Midrange Driver: handles \~300 Hz – 3.5 kHz.
* Dual Woofers: optimized for \~20 Hz – 300 Hz.
* Nominal Impedance (assumption unless specified): 8 ohms.
* Target Crossover Frequencies:

* Low-pass (woofer → mid): 300 Hz
* High-pass (mid → tweeter): 3.5 kHz

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Final Crossover Component Values (Rounded to standard E12 values):

| Section | Driver | Frequency | Impedance | Capacitor (µF) | Inductor (mH) |
| ------------- | ------- | --------- | --------- | -------------- | ------------- |
| Woofer → Mid | Woofer | 300 Hz | 8 Ω | 47 µF | 3.0 mH |
| Woofer → Mid | Mid | 300 Hz | 8 Ω | 47 µF | 3.0 mH |
| Mid → Tweeter | Mid | 3.5 kHz | 8 Ω | 4.0 µF | 0.27 mH |
| Mid → Tweeter | Tweeter | 3.5 kHz | 4 Ω | 8.2 µF | 0.13 mH |

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