Knowles Sugar Cube Speaker 15 x 11 x 4mm


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The Knowles 15x11x4mm Sugar Cube speaker, the best model railway small cube speaker available on the market!

Available with a 3, 4, 5, 6, 7, 8 or 9mm high enclosure or with no enclosure. Simply peal away the self adhesive for the sticky gasket to attach to your enclosure of choice.

0.5W – 8 Ohm output

This speaker will suit sound decoders from ESU, ZIMO, Digitrax, NCE, Soundtraxx, Doehler & Haass, CT Elektronik etc.

Having used and installed dozens of speakers from various sources, I have found that ‘Sugar Cube’ speakers (15x11mm cube style speaker drivers) can greatly vary in quality, which can greatly affect the sound produced inside of a model. There are hundreds of retailers selling ‘Sugar Cube’ speakers with images of particular speaker drivers, but often I’ve found these to be inaccurate to what actually arrives in the package.

The 15 x 11 x 4mm Knowles sugar cube speaker formed the industry standard for ‘Sugar Cube’ speakers around a decade ago, however as they are no longer in production, many manufacturers are turning to the 15x11mm speaker driver offerings of other manufacturers. Out of all 15x11mm speakers offered on the market, I have found the Knowles 15x11mm driver to produce the best overall sound, particularly with low-end bass frequencies, as well as clarity and volume. Many competitor 15x11mm speakers lack the low-end bass frequency response of the Knowles 15x11mm driver, which is shown in the following frequency response diagrams:

Knowles 15x11mm driver

Soberton ‘SP-1511S-5’ driver

Whilst the Soberton driver was tested in free air as opposed to the Knowles driver with a 1cm3 baffle, and whilst the Soberton speaker is tested at 0.5W as opposed to the Knowles driver at 0.35W,  it is clear that the Knowles driver can achieve higher decibels (dB) in the lower frequencies; e.g. a max of 81dB at 300Hz vs. 77dB at 300Hz. At it’s max output of 0.5W this would no doubt be a greater difference in dB. Science aside, I have compared both of these speakers in practice, with the same enclosure/baffle, sound decoder, sound file, sound decoder & sound decoder settings. The Knowles driver noticeably outperformed the Soberton driver, and even more noticeably outperformed other cheaper 15x11mm drivers offered by companies such as CUI.

Some concluding notes. I am not suggesting that the Knowles 15x11mm driver is the best speaker driver to use for all model railway applications, regardless of available space inside of a model, scale of model… All I have found is that out of all available 15x11mm speaker drivers that I have used, the Knowles 15x11mm speaker driver I have found to be clearly best. I have also used smaller and larger speaker drivers (12x8mm, 13x18mm, amongst others), these have produced different results, the larger drivers generally tending to well outperform 15x11mm drivers.

At the end of the day, all speaker drivers are usable, and all speaker drivers I have purchased or used myself have been acceptable, however the overall quality will vary.



Additional information

Enclosure Height (in addition to height of speaker)

None, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm


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