I feel your pain. I've been there, and done that, about 30 years ago with my first big bass head and cab. It's very frustrating to not know exactly how to get the best out of your rig because you haven't been exposed to enough knowledge to really have a good solid control over your EQ.
If you're going to play any instrument in an ensemble format, you're going to have to learn a bit about EQ ranges and where they go. It doesn't hurt for you to know where the typical frequency ranges are of other instruments, either, whether they are in neighboring frequencies or far away. Oftentimes I've been in bands that are being mixed by someone who has little or no clue about anything frequency related, much less about compression, equalization, phase issues, etc.
This chart might help you get a better visual on where different instruments typically live in the frequency spectrum, and how you can work within your EQ to better hear your bass. Now, this is only a STARTING point, and not the be-all and end-all of your whole band's sound. Some bands have bass players whose bass you simply cannot feel, and others have bass players whose bass you can definitely feel, but never get to really hear because they lack midrange detail, often by their own design. It's just a matter of what you really want out of your bass.
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Specific to your SVT350, I'd set your bass to 0, put your UltraMid to 0 and your treble to 0. Turn your graphic EQ on, and pull your 40hz and 80 hz down just a bit, push up a tiny bit at 150 and a bit more at 300, 600 and the rest stay flat. Play your bass with your band playing, and listen to what you like and don't like about that.
From there, if you need more lows (also called "weight" or "heft"), bring up your 80hz first, 40hz only if pushing at 80 doesn't get you the frequency you want (like if you don't feel the floor vibrate like you want it to). Remember, your 40hz slider is more felt than heard. If you need more mid highs to define your upper register, add in a LITTLE bit of 900 first, and if it's still not enough, gently bring in your 600hz. Above 900, you're beginning to run into the space of the guitar fairly substantially. You want to support the guitar's tone as if it was piggy-backed on your bass' tone. So if you bring up anything above 900hz, do it sparingly, and with the understanding that you might be muddying up the main area where the guitars make a living in terms of definition.
If you want string detail, or fret grind detail, bring in your 2K a bit for general detail, or your 5K for a bit more crispness. Again, take care to listen to what's going on there, because those ranges are the attack for the kick, toms and snare. So try to balance it all out.
Once you're established there, and you like how it sounds with your band, I'd use your rotary EQ to shelf things high or low, in order to add in or remove any overall room characteristics from a very general standpoint. Remember, your controls are centered at 50 hz on your bass rotary knob, and 5k on your treble rotary knob, and your Ultramid will scoop your midrange to the left (remove your mid high detail) or build it up to the right. Use this sparingly and in a general fashion only. This is for overall flavor only, and not to fix room acoustic issues.
If you find yourself playing in hard-to-control rooms, you'll need to use your graphic EQ to remove frequencies that are resonating heavily in the room. The reason is, structurally, any room resonates at certain frequencies, so feeding it MORE of a frequency or LESS of a frequency can be good or bad, depending on the overall blend. For bass, you'll find these frequencies are either boomy (250hz. and lower) or honking (250-1K). As you're playing, identify generally where that boom or honk is happening, or maybe isn't happening, and adjust your sliders up or down from there. One rule to remember, a little is a lot. So adjust as little as necessary to get the job done, and if you don't hear a change in the frequency you thought was the issue, but it back to where it was, and move to the next one. Eventually you'll be familiar enough with how it sounds and you'll say, "OK, I think I need to cut/boost a bit at 150/80/1K 2K etc."
Hope that helps.
Thanks again!!
