Originally Posted by malnutrian
Just wondering if I should go with a 8 or 10 inches subwoofer.
I am trying to install KEF Ci160QS that are in-wall speakers. Not sure if 10 inches would cause too much base, or if 8 inches would suffice.
Unfortunately the above question suggests a lot of misunderstandings about both speakers and subwoofers.
First off, congratulations on choosing an in-wall speaker that looks pretty nice on paper. I have long had a pair of Q15s, and appreciate the theoretical advantages of coaxial speakers.
The first problem with your question is the implied idea that you can tell how much bass a subwoofer generates based on the diameter of its driver and that larger diameter drivers necessarily generate more bass.
In fact a well-implemented subwoofer does what you want it to do within useful limits. You have several effective adjustments on your AVR for controlling it.
The idea that larger subwoofers necessarily generate more bass is wrong because how much bass the subwoofer generates is up to you. I suspect that your real fear is that your subwoofer will have boomy bass, and the answer to that fear is counter-intuitive: Generally, boomy bass is due to subwoofers that lack sufficient bass extension or deep bass capability.
The important parameter for subwoofer performance is bass extension, or how deep or low the deepest or lowest frequencies in the music or movie can go and still be effectively reproduced. That is not necessarily a function of the diameter of the woofer driver. It is very possible and even not uncommon for a 8 inch driver to put out more bass than a 10 inch driver.
You see the effectively of a subwoofer driver is dependent on how much air it can move in a well-controlled and accurate manner. All things being equal a larger woofer driver can move more air, but all other things are rarely equal. One can find 8 inch drivers with linear operation over distances ranging from nust a few mm to maybe a dozen or more mm. Thus an 8 inch driver with 12 mm linear travel and outperform a 10 inch driver with 3 mm linear travel.
Another serious issue is that the bass response of open back wall-mounted speakers like the one you seem to have chosen is very dependent on how it is installed.
So, your question can't really be answered well as it is currently written.