K-55 Replacement.  The New A-55G Driver

Update 8-11-2021

Today we are announcing the A-55G/2 driver. With some further finessing of the diaphragm, John Allen worked with the manufacturer to further enhance and improve the original A-55G with even lower distortion. With the manufacturing changes and challenges, the pricing for these new and improved drivers will be $450/pair plus shipping.

Here is the flyer from John Allen announcing the new driver: 

New A-55-G 2

Here is a trace showing this new driver in comparison to the Atlas PD-5VH (Also known as K-55X):

PD-5VH vs A-55G-2

This new A-55G/2 is a great improvement over any other replacement drivers that are available for these speakers that use the 1 3/8 thread and we are excited to be able to get them out to folks.

This new driver can be used to replace the Klipsch K-55X, K-55V, K-55M, K-51V and also the midrange drivers for the KLF-20 and KLF-30.  Can also be used to replace the K-57H drivers that have the 1 3/8 thread.  We are happy to announce that we are going to be allowed to market this remarkable new midrange driver to the public.



This new driver is a product of John Allen of High Performance Stereo who has been working on this project for 10 years and spent $150,000 on it’s development.  John’s goal was to build the best midrange driver he could build to use in the application the K-55 driver is used in.  His model as the best that has been produced in the past was the two piece phase plug version of the K-55V that was only built for about a year around 1982.  I agree that the two piece phase plug version of the K-55V was the best of the group of drivers we have had so far, and I believe this new driver, the A-55G is even better than that one.

Until the A-55G became available, the only driver available in current production is the Atlas PD-5VH also known as the Klipsch K-55X.  The A-55G has better frequency response and lower distortion and should offer improved performance compared any of the drivers produced in the past or in current production.

Quoting John Allen:

"Not only does the A-55-G feature a smoother frequency response and wider bandwidth, it also has lower distortion than any other driver of its type. It can only be described as a stunning achievement in loudspeaker technology. We are calling it the Stradivarius of midrange compression drivers."

Frequency Response  of the A-55G on the Klipsch K-401 horn +or- 3db from 300hz to 6khz.

driver x smoothed

Al Klappenberger of ALK Engineering has run a distortion test on the A-55G compared to the reference two piece phase plug version of the K-55V.  He got a total harmonic distortion of 1.58 percent on the K-55V which is a very good reading.  However the new A-55G driver came in with a THD or only 1% which is excellent.  That is a 4db improvement in THD compared to the already very good two piece phase plug K-55V.


The following plot is of the current production Klipsch K-55X (Atlas PD-5VH) vs the A-55G frequency response.  Both tested on the same K-401 horn.  I woud say the frequency response of the K-55V is about +or- 4db from 300hz to about 5.5khz or we could say +or- 6db from 300hz to 6khz.  With the frequency response of the A-55G at +or-3db from 300hz to 6khz.

pd-5 vs driver x smoothed

B & K Sound, 1925 East Gum Log Rd. Russellville, AR, 72802 phone-479-967-1542