Getting my amp signal to powered speaker??

The Thump 15A manual (here https://mackie.com/sites/default/fi...NUALS/Owners_Manuals/Thump12A_Thump15A_OM.pdf) shows that it can accept a wide range of input signals from low level signals like mic and instrument level to high level (unpowered) signals like mixing board outputs. Spend some time reading the manual to get an understanding of what it can do. To use your BG250 208 with the Thump 15A, you would need a mic cable connected from the balanced out on your amp to an input on the 15A.

If you don't have a manual for your amp, here's one: http://downloads.music-group.com/so...electronic_bh250_bg250-208_manual_english.pdf

Can you take your bass and amp to a local music store to ask if you can try it with some powered speakers they have on display? They might even have a 15A you can try before you buy.

I'd also suggest describing the real world music setting you're experiencing that makes you want to get a 15A. The collective experience on this board might have a better (and far cheaper and far lighter) solution for you. Come back here with your questions. Good luck.

 

Without commenting on the appropriateness or desirability of doing what you're trying to do, I'll offer this: the BG-250's XLR balanced out is (approximately) line level, so it should be able to drive a line-level input of a powered speaker without a problem. If the powered speaker uses a 1/4"-TRS line-input connector, which I think is likely the case, then you'd need a female XLR-to-male TRS adaptor cable. On the Mackie stuff, I think the XLR part of the combo input connectors are only mic level, so you can't use a regular old XLR mic cable to do the interface -- you'd overdrive the mic input on the powered speaker. So you'll need that adaptor; they're available on-line.

 

I would use a DI box. Plug your bass into the DI. Send one 1/4” out to your amp and one XLR mic cable out to the Thump.

The thumps are very boomy. The name is not just marketing.

This way you can EQ the two separately rather than just sending the amp eq and making it louder.

This is how a lot of soundtechs get bass signal. Most amps have an XLR DI out these days though.

I prefer this when we have PA support since I can tweak my amp and turn it up a little without affecting the mix.

 

Using a direct box and going into the mic input will also work, but isn't really called for. The amp DI out is switchable pre or post EQ, and the powered speaker has EQ as well. OP isn't trying get an input into a PA system, he's trying to put together his own awesome rig of doom from some odd bits and pieces. Rock on... I guess. OP: I dang sure would try to audition this kludge before laying out my hard-earned frog-skins...it might not be the sort of aural nirvana you're imagining.

 

Nothing.
What you are looking at are Portable PA Top Boxes, made to be placed on top of pole stands at head level. They preform some lows but mostly mid and highs pretty good for a portable unit.

Sounds good, deep bass and cheap. Sorry you can only pick two.
Part of Hofmann's Iron Law. Click>Josef Anton Hofmann - Wikipedia

Again remember these are PA Top Boxes, there is a reason PA's use Subwoofers.

 

Just run a cable from the balanced output on the back of the amp to the input of the powered speaker. Start with the volume low on the powered speaker, and then bring it up until you get the desired balance of sound with that of the amp.

 

Many wanting more power, just need more power on lows.
Powered subs usually include a crossover, so you can try to run the line out into a powered sub. And if you need more top end add a powered coming off the sub.
Do the same thing @lunarpollen pointed, start off with volume low on the sub.

 

If you have a "headphone out/di out/send" on that head, you can run that straight into it no problem.

 

Without mentioning any specific brands, you can buy a new 500 watt powered sub for $350 that will work with your existing gear. Please understand that 500 watts in a subwoofer will add some low end to your rig. In medium to large size rooms, it will probably not achieve what I think you are seeking. Is there a system in a nightclub in your local area that sounds good to you? Ask the owner how much power the subs in the system have. Low end that people describe as "sub" requires large amounts of power as a proportion of total system power, and it goes up very fast as the size of the room increases.