Guide to Bassoon RIBO Low “A” Extension

Any bassoon low A extension is an acoustic compromise – the bassoon is simply not built or tuned with the extra length in mind. A traditional cylindrical, thick-walled low A extension typically suffers from an incredibly stuffy low B in addition to significant tuning and timbre changes throughout the instrument’s range. 

While it is not possible to eliminate these drawbacks entirely, they can be significantly reduced. The RIBO Low A extension’s unique shape and thin-wall construction allow the instrument to speak with less resistance on low B and significantly lessens other acoustic changes. Furthermore, its light weight (under 20 grams) virtually eliminates balance or weight concerns.

RIBO Low "A" Extension for Bassoon Edmund Nielsen Woodwinds Store

SIZING
In order to better fit the wide variety of bassoons that exist today, the RIBO Low A extension is available in multiple sizes. Best results are usually attained according to the chart below:

Available Sizes ( Updated July 2026)
Small is designed to work with a bells 38mm in diameter.
Medium around 39mm bells
Large around 40mm

* – When in doubt, it’s better to err smaller.

ADJUSTMENT Each extension is provided with several layers of  tape which allow for fine adjustment in addition to helping create an airtight seal. To ensure the best possible fit, remove layers of tape until the extension can be placed and removed easily. Additional tape can also be added – for example, if it is desired to use the same extension on multiple bassoons with different size bells. However, the addition of a many layers of tape will eventually constrict the bore and reduce the benefits of the extension.

CARE AND HANDLING Due to its thin-walled construction, the RIBO Low A extension is susceptible to crushing if handled harshly. Make certain to adjust it properly (see above) so that undue force is not necessary to place it in or remove it from the bell. Store it in a box or other stiff-walled container when it is not in use, and take care not to sit on it.

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