New BassChat 8"Cab design

[Phil Starr]

I'm not familiar with this cab and frankly I don't believe some of the advertising nonsense about the resonator technology so I've kept away from offering too much advice. There is also good reason why most people don't use thin ply for cabs that live on the road and feet pulling out is something that really should not happen. I hope this was addressed in later versions.

 

Anyway you don't need to worry about covering the holes in an internal partition, the white damping material is more or less transparent to sound, some hifi cabs are completely filled with polyester wadding and even have it compressed they even use wool, mineral fibre or glass wool in cabs. 

 

Anyway from basic principles the wadding in the cab should either be fixed to panels or the cab should be stuffed in such a way that it stays in place. Loose wadding needs to be kept away from the ends of any ports where the hopefully trouser flapping volume will also flap loose wadding  If the wadding is meant to be fixed staples alon aren't really enough and I'd use some spray adhesive as well. Vent the cab after using the spray adhesive as the solvents might affect the speakers.

 

The pressure changes at the resonance of the cab can be quite high and it will find any weak spots and create a rattle or buzz. Buzzing is higher frequency than the fundamental of course. Buzzing could be any mating surfaces in the cab including the speaker drivers and the glue joints between panels. You can exagerate them with a 50hz signal (there are plenty of online signal generators) amplified to high volumes but they are hard to find because of course they have loud sound from the 50hz sinal to hide behind. Just because you have found one buzz it doesn't mean there aren't others.

 

That looks like a very standard switch on the back of the cab, you should be able to de-solder it and put in a new one or find a competent repair tech who can do it for you cheaper than a new panel.

 

Good luck

[rwillett]

On 13/10/2025 at 19:15, tauzero said:

After using the shitty house Orange 50W bass combo a couple of times at a local open mic (absolutely dreadful, the front end goes into clipping almost instantly even with the pad on), I thought I'd build one of these to pair either with a TC BAM200 or Tecamp Puma 900 to use there. Interestingly, a search on Ebay for the Fane Sovereign 225-8 gave various results with shipping costs being displayed but when I clicked on https://www.ebay.co.uk/itm/125957204831 it showed shipping as zero instead of a few quid, so that's the one. A trip to B&Q beckons - I think I'll eschew their free cutting service, the last time I took advantage of it didn't fill me with confidence. Looks like materials cost should come in at around £90 given that I have several speakers worth of drainpipe in the shed.

 

Just in case it helps, I'd be happy to print a port up for you to play with. This is a cross section of a 125mm port. The purple is the drain pipe (or whatever, it's simply there to show where it fits), the red is the flange that the pipe connects to.

 

It's all parameterised so I just made it 50mm as opposed to 125mm. It even has your name on it

 

I've added chamfers in but no idea if they help or not.

Rob

 

 

[Obrienp]

Thank you @Phil Starr for the advice.
 

Unfortunately, it looks like that DPDT switch (which, as you say is very standard) is attached to the PCB stuck on the back of the unit. I am not sure whether it will be within my capabilities to replace it. That PCB is mounted on a 50mm chunk of ply attached to the metal plate. Not sure why they did that. I assume it was to give it sufficient mass to resist vibration but it also protrudes a long way into the cabinet. I would have thought creating a long lever would make it amplify any movement in the plate.

 

One supplementary question: should there be any wadding in the back compartment of the cabinet; ie the space behind the internal baffle? Would it help reduce the resonance if I put some in? I would be careful not to block the port that is at the bottom of that compartment. At the moment the cabinet vibrates so much (when I hit Eb, E, F) that the amp starts to dance about on top.

 

Thank you for your forbearance. As must be obvious, this is far from my area of expertise.
 

 

[Pea Turgh]

Maybe some of the internal bracing was damaged when the foot incident occurred?  Sounds like more than a damping issue to me. Could send it to Alex for an assessment then claim on insurance?

[Obrienp]

9 minutes ago, Pea Turgh said:

Maybe some of the internal bracing was damaged when the foot incident occurred?  Sounds like more than a damping issue to me. Could send it to Alex for an assessment then claim on insurance?

Thank you for the suggestion. Fortunately, it was just a little damage to the ply where the feet were located: the two on the front side of the cab, so I was able to inspect it thoroughly when I removed the drivers. The only internal bracing is the internal baffle board assembly, as far as I could see. There is certainly nothing loose inside. I reinforced the area where the ply was damaged with some rectangles of 8mm ply, glued and stapled. I am pretty sure that is not moving and the buzzing is not coming from that area.
 

TBH this cab always vibrated a lot at volume. I guess that is what comes from the lightweight construction: 10mm ply throughout. I always put a non-slip mat on top when gigging it. The buzz is something I hadn’t noticed before but I haven’t used it for a while. I have been using my LFSys Monzas, which are made of thicker ply and don’t vibrate as much. Now I have heard the buzz, I can’t un-hear it. 
 

I probably do need to consult Alex but I wanted to get an impartial view first. Unfortunately, the cab isn’t insured and the incident with the feet happened a couple of years ago.

[tauzero]

2 hours ago, rwillett said:

 

Just in case it helps, I'd be happy to print a port up for you to play with. This is a cross section of a 125mm port. The purple is the drain pipe (or whatever, it's simply there to show where it fits), the red is the flange that the pipe connects to.

 

It's all parameterised so I just made it 50mm as opposed to 125mm. It even has your name on it

 

I've added chamfers in but no idea if they help or not.

Rob

 

 

 

Thanks, but I've used the drainpipe successfully in three speakers so far and I know my hole saw does the job for it. Oh, and it's Tau not Tao!