Heres what you want to try as part of any cab/combo test (may narrow down the buzz source) Do this with any existing rigs u have, may blow your mind...
Get any (many free) ap that plays a single tone. newer amps you can usually plug phone into a 1/8 aux. FX loop return is great with a 1/8-1/4 adapter. for some old stuff u can get 1/8-rca if needed.
So ap plays just a single note sine wave. Not at all like a bass, which produces a (often weak) fundamental and a cascade of higher and higher overtones.
Play a "safe" note, like E4 (aprox 320hz). Get it going loud. Now drop down octives (160 e3, 80e2, 40e1). You will also want to do this with A notes and B if.you have a 5 string.
When you get down to the "fundamental" b0 e1 a1, you may be horrified by what even "good" speakers actually produce. You may not even get a note or even sound, and the volume is going to be way down. The speaker may be flapping, and thats... just how it is on most rigs.
The good news: U wont want to believe this, but you dont "need" the lowest fundamentals. esprcially for B be happy if its doing (B1)60hz well, E is "ok" as long as speakers strong at 80hz(e2). If that speakers actually sounding good smooth and loud and no flap or rattle at 50(ish hz,, a1) thats actually an AMAZINGly good bass rig, but if not welll... a2 100ish hz wotks.
Whatever u have/get, learn where it starts to suck, then use a HiPassFilter(or tight ParametricEQ bands) to pretty much eliminate anything below that point. Then your rig will be louder and better sounding and not get damaged. You may be able to crank right up and groove on the open strings without farting.
Incredible but ("psychoacoustics") it will sound like bass guitar, even really fat tone bass if its got great low mids, inspite of no super lows.
Problem with used speakers is guy before probably just cranked the bass, and has beat the snot out of the drivers and cones. Cause I dont know if owners used HPF i am increasingly of the opinion that used bass cabs/combos are only worth a small % of new, and will not buy such unless it is stupidly cheap. Like 25% price, not generally what people offer. IMO bass cabs and combos used are generally "overvalued". There are obvious exceptions, especially for real high end stuff, but in the "value" matket not so much.
In this case as already pointed out, u could get new equivalent for not much more $, so frankly, its not worth it (and likely needs a new speaker $$$! if it is to sound good again). If u still even want to bother, offer em whats it really worth (like $50, cause a new driver is $100+++ and work) and when they turn u down, I pretty much guarantee its just sitting unsold a couple years later...
