The SUB3

The SUB3 is a sub-woofer designed to work with the Chartwell LS3/5 and LS3/5A from Graham Audio, but it is also applicable to other designs of similar sensitivity and impedance. Designed by Derek Hughes, it employs a novel bass loading technique to achieve extension down to 35Hz in a compact enclosure.

They are supplied in pairs, and are designed to be placed near to the rear wall, while the main loudspeakers remain in their usual 'free space' position. Output is via the front-facing reflex port.

There are connections on the rear for the input from the amplifier and output to the main speakers. There is also provision for feet or spikes to be fitted to the base of the cabinet. Being passive, there are no controls to misadjust - the system is designed to be "plug and play".

The crossover uses high quality components, including air-cored inductors for zero saturation distortion and polypropylene capacitors. The system crosses over at 100Hz, and in doing so, relieves the LS3/5 or LS3/5A of energy frequencies below this point. This will allow the system to reach greater replay volumes, providing there are adequate reserves in the amplifier used.


System 4th order bandpass
Finish Real wood veneer
Dimensions (w/h/d) 30cm by 30cm by 34cm
Frequency response 35Hz to 100Hz
Nominal impedance
Sensitivity 84dB SPL (2.83V, 1m)
Recommended amplifier power 30 to 80 watts unclipped programme
Connections Gold-plated binding posts


  • Hi-Fi Advice - July 2020

    “Between the LS3/5’s and the LS3/5A’s, I think some people will perceive the newly made 5’s as more natural or organic while other people will prefer the more widely known 5A’s relatively more neutral and linear midrange delivery. Personally, I’m still on the fence and switching from one pair to the other remains a matter of adjusting. The technical perfectionist in me prefers the LS3/5A’s more neutral midrange while the music lover in me is more passionate about the LS3/5’s fuller and richer midrange. I say: just listen for yourself! ...Naturally, the bass goes substantially deeper and also feels more solid. But the biggest surprise for me is how flawlessly the subs pair with the monitors. The crossover point is clearly well-chosen and the transition absolutely inaudible. Tonally, the woofers are also an ideal match. This is the great benefit of using same-brand speakers that are made for each other. You get a natural synergy that you don’t get quite as easily (or at all) when adding a universal subwoofer. ...The case for the SUB3 subwoofers is not at all ambiguous. They simply provide what one hopes from subwoofers but rarely gets: a meaningful extension of the speakers’ bass range in a seamless and wholly synergistic manner.”

    Hi-Fi Advice - July 2020