New BassChat 8"Cab design

[Chienmortbb]

2 hours ago, Phil Starr said:

3 hours ago, Chienmortbb said:

 

I was thinking that the random bass playing from the hall was louder than I was for some of the time

Random may be too kind for some of our playing...

[Phil Starr]

Snatched a few minutes to finish the cab build from the bass bash. A few minor faults caused by rushing things as I was talking  but nothing a bit of filler won't sort . Hopefully it can be filled and painted this weekend.

 

[DGBass]

@Phil Starr, I see your cab build has what looks like cross bracing inside between the top and side panels. I didn't see this on the original build diagram. Is this a late revision and if so, were they just glued in place and do the two braces connect where they cross? What wood did you use for the braces? Cheers, DG.

[Phil Starr]

1 hour ago, DGBass said:

@Phil Starr, I see your cab build has what looks like cross bracing inside between the top and side panels. I didn't see this on the original build diagram. Is this a late revision and if so, were they just glued in place and do the two braces connect where they cross? What wood did you use for the braces? Cheers, DG.

Well spotted, the original cab which was cube shaped had no braces and that is what we have tested. It's a simple matter to cross brace the panels and I had some off-cuts which were exctly the same dimensions as the panels. The ones in the photograph are just a tight push fit and i will stick them in when I fit the speaker. I'll do a final write up of the build and discuss bracing and damping the cab there. If you are going ahead with the build before I reach that point then simple cross bracing like this is almost impossible to get 'wrong'

Edited October 26, 2024 by Phil Starr

[Phil Starr]

Better pic tomorrow but it's painted and working

[Chienmortbb]

Nice work Phil. 

[bremen]

On 26/10/2024 at 17:34, Phil Starr said:

Well spotted, the original cab which was cube shaped had no braces and that is what we have tested. It's a simple matter to cross brace the panels and I had some off-cuts which were exctly the same dimensions as the panels. The ones in the photograph are just a tight push fit and i will stick them in when I fit the speaker. I'll do a final write up of the build and discuss bracing and damping the cab there. If you are going ahead with the build before I reach that point then simple cross bracing like this is almost impossible to get 'wrong'

Top tip: rout a 6mm slot into the panels. Fill with foaming flooring adhesive

 

https://amzn.eu/d/frLAMMw

 

5.5mm ply bracing then fits snugly and is going nowhere.

 

 

[Chienmortbb]

5 minutes ago, bremen said:

Top tip: rout a 6mm slot into the panels. Fill with foaming flooring adhesive

 

https://amzn.eu/d/frLAMMw

 

5.5mm ply bracing then fits snugly and is going nowhere.

 

 

Are you suggesting this purely for the bracing? Most builders stoped using that type of adhesive for cabinet edges some time ago. 

[Phil Starr]

On the subject of bracing: I eventually settled on a single horizontal brace placed centrally in the side panels. The vertical brace was too close to the port and placing it off centre didn't really add to damping the panel resonance. Placing the horizontal brace centrally shifted the resonance up an octave as you'd expect but on a simple tap test reduced the resonace considerably in volume. The cab sounded fine with no bracing too but the cross brace was a simple addition so I left it in

[bremen]

On 28/10/2024 at 09:06, Chienmortbb said:

Are you suggesting this purely for the bracing? Most builders stoped using that type of adhesive for cabinet edges some time ago. 

Yes. It's probably not as strong as pva but it holds the bracing nicely in a slot.

[nekomatic]

I've just received a delivery from Blue Aran, so watch this space for a build!

 

edit: under way!

Edited January 23 by nekomatic
link to build thread

[Chienmortbb]

On 11/07/2023 at 21:27, Phil Starr said:

John provided the grille so I don't know where it came from.

I have only just noticed this, it was the original grille from the After 8 Combo. It now has a new grille that I will photograph later. Bought from SGS Metals on EBay.  I will also link to that later. SGS will cut to size. 

[tauzero]

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.

[Stub Mandrel]

2 hours ago, 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 once tried out a bass through a Crush 50, at any volume could only get overdriven tones whatever I did.

 

Later, when I was older and wiser I discovered the 'blend' control effectively pans from a clean channel to a dirt channel. If it's been left dialled to the dirty side, you'll get exactly the symptoms you describe. 

 

 

[tauzero]

2 hours ago, Stub Mandrel said:

 

I once tried out a bass through a Crush 50, at any volume could only get overdriven tones whatever I did.

 

Later, when I was older and wiser I discovered the 'blend' control effectively pans from a clean channel to a dirt channel. If it's been left dialled to the dirty side, you'll get exactly the symptoms you describe. 

 

Ta. I'll give that a whirl in ten days when I'm back there (probably won't have completed the cab by then anyway).

[tauzero]

@Phil Starr, does the cab need some acoustic wadding?

[Phil Starr]

14 hours ago, tauzero said:

@Phil Starr, does the cab need some acoustic wadding?

Do you know I can't remember what I put inside, it's a cab I built live at the SW bass bash last year and 'finished' off with a coat of Tuff Cab when I got home. It still lacks a grille. I'll have a look inside when I get time.

 

I've a particular set of views on waddding which is itself a complex and controversial issue in the design of hi-fi cabs. Go and read Colloms: High Performance Loudspeakers if you want to come out more confused than you went in. I generally favour using a fairly dense wadding stuck to the panels which reduces internal reflections within the cab and can also damp panel resonances. I'm thinking thick carpet felt or mineral loaded plastic foams here. the problem is extra weight which you don't want in a portable cab. I also use the white polyester stuffing you see in commecial cabs and which I rescue/repurpose from old pillows and duvets; such a skinflint  I tend to staple this in to break up standing waves inside the cab so it fixed in the middle of the cab not hard against the panels. You need to make sure it doesn't end up covering the end of the vents in a ported cab though. 

 

If I have time I tend to use an iterative process of trial and error. If I hear a resonance or see it on a frequency response I'll see if I can kill it with wadding and i'll liten to the cab with and without wadding to see which I prefer. I have to confess to not having done this with this cab. Sorry 🫣

[tauzero]

So using my default of needled felt would be a reasonable thing to do?

[Stub Mandrel]

I once added a port to a small combo I made, using the cut and try a card tube method.  This improved it.

 

I felt the wadding was a bit dense and started pulling bits out of the port.

 

By the time I had pulled all the wadding I could get to out of the hole,  it sounded much better.

 

Not sure this is of any use, except to say don't be afraid to experiment. 

 

[RhythmJunky]

2 hours ago, Stub Mandrel said:

I once added a port to a small combo I made, using the cut and try a card tube method.  This improved it.

 

I felt the wadding was a bit dense and started pulling bits out of the port.

 

By the time I had pulled all the wadding I could get to out of the hole,  it sounded much better.

 

Not sure this is of any use, except to say don't be afraid to experiment. 

 

Cool little combo. What size drivers are those ?

[Phil Starr]

3 hours ago, tauzero said:

So using my default of needled felt would be a reasonable thing to do?

I guess, looking up needled felt leads me to think that there is a huge range of materials here with quite a range of densities and compression so it must be a mechanically variable material. That's a posh way of saying I'm not sure   If yours is a dense material you could save some weight by only putting it on three surfaces opposite each other, the back, one side and either top or bottom. If you were with happy minimal damping then just putting something on the back would be most effective.

[tauzero]

26 minutes ago, Phil Starr said:

I guess, looking up needled felt leads me to think that there is a huge range of materials here with quite a range of densities and compression so it must be a mechanically variable material. That's a posh way of saying I'm not sure   If yours is a dense material you could save some weight by only putting it on three surfaces opposite each other, the back, one side and either top or bottom. If you were with happy minimal damping then just putting something on the back would be most effective.

 

This is the stuff - the Nova Pad https://www.ebay.co.uk/itm/162935948623?var=464180501111 which I've used on the BC112Mk3, the micro cab, and the Plenty cab.

[Stub Mandrel]

2 hours ago, RhythmJunky said:

Cool little combo. What size drivers are those ?

 

3" O think! pjb eat yer heart out!

[Obrienp]

I hope this isn’t hijacking this thread but the conversation by @Phil Starr and others about internal acoustic damping is very timely for me as I am trying to sort out a few little issues with my Barefaced Two10S, which has caused me to remove the drivers at one point and notice the internal damping material.

 

I took the drivers out as I was implementing a long term fix to the anchoring of the feet on the long side of the cab (horizontal position). One had been torn out and another bent at an angle (over enthusiastic helper at a gig). I did a temporary fix with filler but the screws had started to work themselves free recently. On inspection the thin ply had been weakened around the screw holes, so I decided to use threaded captive nuts and reinforce the two damaged areas internally with rectangles of 8mm ply (glued and stapled).

 

In the process I noticed that the white damping material appeared to have come away from where it had been stapled (staples still there but material scrunched up). I put it back where it had obviously been and re-stapled it. This formed a lining on four sides against the internal baffle board but not on the speaker baffle. It covered the slots in the internal baffle board. Is this correct? Strikes me it must be restricting the flow of air into the reflex chamber in the back of the cab. Should it be like that?

 

On reassembly (with new speaker mounting bolts), I tested it with a Mark Bass LM111 500 with gain at 12 o’clock and EQ the same, filters off and master at about 11. I immediately noticed there appeared to be a distinct resonance around Eb, E, F accompanied by a sympathetic buzzing from somewhere on the cab. I eventually tracked this down to the switch plate on the back. The retaining screws weren’t that tight and couldn’t get proper purchase in the 10mm ply, so I eventually resorted to T-nuts and hex bolts, plus rubber draft excluder to make a gasket. This improved things a bit but did not eliminate the buzz. It really is in sympathy with the cab’s resonance around E: high pitched on a high E and low when I play open E. I think it is actually coming from the DPDT switch itself and that is probably something I need to seek advice from Alex about (new unit is around £120 😱, well that is what the switch conversion kit costs). 
 

All the above said, I noticed that there is no damping material in the back compartment of the cab. I am just wondering if putting some in might damp down the resonance around E, or will it just mess up the function of the reflex and port?

Apologies, if I should be posting this in a different thread. 
 

incidentally, I am interested in making my own little low wattage cab like the BC 8” cab but I want to embed my HB GPA-100 power amp in it somehow, without it overheating (convection cooling). More of that later, when I have sorted out the Two10.

[Chienmortbb]

I am sure others would speak either more authoritative voices but I don’t think wadding will help with low resonances.