so ive been on SSB for about three years now, mostly on 40 and 20m, and lately something has been bugging me about my transmitted audio. guys on the other end keep saying it sounds like im in a barrel or there's a low rumble underneath everything. my mic gain hasnt changed, speech processor is on like it always has been, but something shifted.

im running an IC-7300 into a Heil PR-40 through the boom arm. the mic element itself is probably fine but who knows. i did move the shack around a couple months ago and now the desk fan is closer to the mic. could be that but it seems like too obvious of a fix. anyway i started reading about proper SSB audio and realized i actually dont know that much about optimizing it beyond just plugging in and talking. like i know you want to keep ALC from hammering too hard and you should be somewhere around 50-75% of rated power but thats kind of the extent of my knowledge. anyone have a sort of rundown on what really makes SSB audio sound good vs bad? and also curious if anyone has had the barrel effect before and figured out what it was

the fan is almost certainly your culprit for the low rumble, i went through something similar and didnt figure it out for weeks because i convinced myself it had to be something complicated. PR-40 is a dynamic mic with decent rejection but it's not magic, get it away from the fan or point the fan somewhere else and see what happens first before you dig into anything else.

as for general SSB audio quality — a few things ive learned the hard way. your ALC should barely be moving on normal speech peaks, if its bouncing up constantly youre overdriving the front end and that causes all sorts of compression artifacts. on the 7300 specifically i found that setting the mic gain so the ALC indicator just kisses the top on loud syllables and then backing it off a hair gives cleaner audio than running it hotter and relying on the speech processor to do heavy lifting. the built in speech processor on that radio is decent but it works better when your baseline level is already good. also make sure your bass response isnt too high, SSB is a relatively narrow channel and all that low end just turns into mud over RF, most guys who sound really crisp are rolling off below 150hz or so whether they know it or not

yeah what he said about ALC is spot on. i used to think more ALC action meant more talk power but its really not how it works at all. you want the average modulation up, not the peaks slamming into limiting constantly.

one thing i'll add — have someone record your audio off air if you can, like ask a buddy to do a quick recording on his end. monitoring yourself on the radio's monitor function isnt the same as what actually comes out the other side after going through the TX chain. ive been surprised more than once at how different it sounds. theres apps that let you do SDR monitoring of your own signal too if you set up a second receiver, that's probably the most useful diagnostic tool ive found for audio stuff