Design Process

What follows is a simplification of the design process of our loudspeakers.

Drive Unit Selection
Numerous bass, mid-range and tweeter units were analysed before we found the optimum units for the 500 series.

Bass driver
The 503, 502 and 501 speakers employ a sophisticated isobaric loading technique which employs an additional internally mounted bass driver.

For a more detailed explanation of isobaric design, click here

An isobaric arrangement dramatically lowers the bass cut-off frequency and reduces the harmonic distortion when compared to a simple enclosure with a single driver.

Employing this technique with the 501 reduces the bass f -3dB cut-off frequency from 38Hz (using a single driver) to 23Hz (isobaric configuration). This reduction has a dramatic effect upon the quality of the musical presentation. For example, bass notes are ‘felt’ rather than just ‘heard’.

The design process begins by identifying a suitable bass driver(s) for the size of the enclosure.

The Thiele-Small parameters of each driver are measured and recorded using specialised calibrated equipment. For a detailed explanation of Thiele-Small parameters, click here

The driver is then run-in for a period of at least 24 hours. The Thiele-Small parameters are then re-measured and entered into our enclosure simulation software.

If the simulation results suggest that a bass driver is usable within our desired enclosure size, a test enclosure is constructed, and we measure the near field bass response to see if it meets the simulation result. If it does, then the driver is then measured for non-linear distortions. If the unit fails to meet our distortion specification, then it is rejected.

We then proceed to determine the optimum type, position and quantity of acoustic absorption material for the enclosure. In addition, we also determine the ideal position for our additional bitumen based damping panels and extensive bracing.

Our competitors do not use the isobaric loading technique, nor do they employ both acoustic absorption material and bitumen based damping panels.

Mid-range driver
The important criteria here are:

• Flatness and smoothness of response from 200Hz up-to 5kHz
• Very low non-linear distortions
• Minimal response difference between the on and off-axis response

We measure the anechoic frequency response both on and off axis, and if acceptable, we then measure the distortion with respect to frequency. If the unit fails to meet our stringent specification, then it is rejected.

We then proceed to determine the optimum type and quantity of damping material for the midrange enclosure.

Tweeter
We measure the flatness of response from 2kHz to beyond 20kHz. We do this both on and off axis. In addition, the non-linear distortions of the unit are measured with respect to frequency. Once again, if any of these results are unsatisfactory, the unit is deemed unsuitable.

Crossover Design
Once the drivers and the enclosure have been determined, a prototype sample of the finished cabinet is constructed.

The anechoic response of each driver’s acoustic magnitude and phase is measured whilst mounted in the enclosure. In addition, each driver’s electrical impedance magnitude and phase is measured. This data is then exported to sophisticated crossover design software with a built in component optimizer, which is able to determine the ideal values of components for the specified crossover frequencies and target response curve. We are able to determine the ideal crossover frequencies, since we have previously measured in the driver selection phase, the on and off-axis response and distortion.

We then build the computer optimized crossover and verify via acoustic anechoic measurement, that it performs as expected, both on and off axis.

Our crossovers are constructed with the:

• highest quality, high voltage, low tolerance polypropylene capacitors
• low resistance, low tolerance, high power inductors
• high stability, low tolerance, high power handling ceramic resistors.

Around 3kHz, our hearing is less sensitive to diffuse fields. However, recording microphones are not less sensitive to diffuse fields. The net result is that recorded music played over conventional loudspeakers in a domestic environment sounds harsh or ‘bright’ compared to the real event. We employ a psycho-acoustic filter to compensate for this. As a result, Hanbridge loudspeakers sound realistic instead of our competitors’ conventional, fatiguing ‘brightness’.