Attach anything (speaker) to top tube / crossbar?

Hi, I am a very casual cyclist and I have a Trek Navigator 3.0. I know there are some small and bike specific speakers like the boom bottle and a bunch of others. But I like better sound than that, and I recently bought the Sony srs-btx300. I mounted it on top of my bike bag in the back on a rack. It's secure enough, but I realized all the good sound is behind me. The speaker is pretty big relatively, but not too big. I think the perfect spot to mount it would be on the top tube / crossbar. But I can't find any brackets or clamps or mounts that can attach anything to the top tube of the bike and keep it up, I've only seen tiny bags hanging below. Has anyone used/seen any kind of an attachment that would allow me to put something on top of the crossbar and prevent it from flipping?

 

Try a handlebar bag.

 

The handlebar bag won't work for me, I already have 2 lights, bell, etc on the handlebars, it's crowded. The perfect sport for it would be on top of the top tube. If I could just figure out how to attach it.

 

You may want to consider the feasibility of a handlebar with either ZERO RISE or to opt for the other extreme with a BMX handlebar which will have an additional, horizontal cross brace ...

• that is, you lose a lot of lateral real estate due to the bends in the bar which a zero rise handlebar will not have

FYI. A few months ago, someone posted pics of a custom head tube spacer which he had fabricated which had a stub welded onto it so that he could mount a light which he could not angle properly on his handlebar (I thought he could have solved the specific problem in a much easier way, but he had his preference for his solution).

BTW. Have you considered moving one-or-both lights to your fork?

Fork mounted lights were not uncommon in the distant past ...

 

I looked at the dimensions of that thing -

13 1/2 inches x 4 5/8 inches x 2 3/8 inches

I don't know how that could be put on the top tube without hitting your knees on it. I am also concerned that being mounted directly on the frame would result in premature death of the electronics from shock and vibe. Also water and sweat dripping on it wouldn't be good. I also seriously doubt that there is much "boom" from the tiny speakers.

Those concerns aside, you should be able to fashion some sort of mount using foam rubber or high density urethane foam and some zip ties.

To keep the mount from rotating you can use friction tape under the zip ties and also tie the mount to the stack underneath or over the stem. Search "bicycle top tube bag" for ideas.