New BassChat 8"Cab design

[djk]

1 minute ago, Phil Starr said:

Hi David, to keep the same tuning you only have to match the area of the round port and keep the same length. Those are the only two numbers that matter. I keep using the drainpipe because it's simpler for most people. if you can calculate pi r^2 that will be ok, but if you are forming a port then it would be better to make it slightly bigger to reduce potential wind noise in the port. I've had a look and something 8x5cm inside measurements and 11.4cm long would work. You can change the shape so long as you keep to 40cm^2 area

Phil, many thanks for the help, it's much appreciated.

 

As I said, for me as I have the ply and no drain pipe it might be simpler.

 

I've now loaded the driver into the cabinet as it is and at low volumes it sound great, although I only completed this today and have only had the chance to try it with my Ashdown Rootmaster 800 (at low volume). I'm ging to see how it sound with the TC Electronic amp later this week. Still waiting for the grill to arrive too.

 

I have a ruminate over which path to take regarding the port and let you know the results.

 

I really appreciate all the work and support you and the others involved in the development of the BC cabinets, thank you.

 

Regards

David

 

 

[Mottlefeeder]

37 minutes ago, Phil Starr said:

Hi David, to keep the same tuning you only have to match the area of the round port and keep the same length. Those are the only two numbers that matter. I keep using the drainpipe because it's simpler for most people. if you can calculate pi r^2 that will be ok, but if you are forming a port then it would be better to make it slightly bigger to reduce potential wind noise in the port. I've had a look and something 8x5cm inside measurements and 11.4cm long would work. You can change the shape so long as you keep to 40cm^2 area

Phil,

Just for my education: changing the port size changes the available internal volume of the cab - what sort of % change in cab volume would start to be audible / ring alarm bells for you?

(Another) David

[Phil Starr]

7 hours ago, Mottlefeeder said:

Phil,

Just for my education: changing the port size changes the available internal volume of the cab - what sort of % change in cab volume would start to be audible / ring alarm bells for you?

(Another) David

That's a great question and I had to think about the answer. Part of this is that I rely on experience, I've spent a lot of time building and modifying cabs. When I build pairs of cabs I'll often try modifications on one cab and then A/B them next to each other so you do get an instinct about small changes

 

The first thing is that the efffects are slight. First of all most of the 'sound' of the speakers is what goes on above 200Hz and the box modelling is about the response of the true low end below that frequency. The other David has tried the cab out as a sealed cab andit 'works' and it probably sounds OK, even though he will get 3db of boost of the low end with a port plus a lower roll of frequency.

 

Secondly the calculations give incredibly percise answers but in real life it's a bit messier. Manufacturing tolerances mean measured speakers vary and the published figures I use can't always be trusted. Thre are always air losses from a cab which are allowed for in the calculations but I use a 'standard' value of Ql=0.7 which is middle of the bell curve. Importantly I then build the cab so ay significant error would show up. I'ver no control over how accurately people build the cab so calculating port sizes to 3 decimal places doesn't make much sense. You can build the cab successfully even if you make small mistakes, which should be reassuring

 

Anyway I've looked at the responses with the same tuning and the box sizes increased and decreased by 10% but tuned to the same frequency.  This is the box you are all building with the Fane in blue. You can see that increasing the cab by 10% (red) gives you a bit more bass but reducing the cab 10% makes a smaller difference. The red trace gives 1db extra at 60Hz and you'd hear that with the cabs next to each other but only just. You wouldn't be able to detect the difference with the smaller cab in this case. This is a 2l shift in volume and the increase in port size is only 0.2l so insignificant. It looks like my instincts were good in this case, Phew

 

 

 

[rwillett]

Finally have finished all the routing for Speakon connectors and handles.

 

 

 

 

Sides, top and bottom already glued,  Now doing front and rear glueing and clamping.

 

 

 

Next steps tomorrow, let the glue cure overnight, a bit of filler (ahem), sanding down, put a 6mm curve on the edges with the router, two layers of smooth Armacab on all external surfaces, one top layer of textured Armacab but masking off any rebated areas, measure for black 3d printed corners, print them overnight as eight hours , assemble all and test for Sunday (hopefully). 

 

Edited Thursday at 21:45 by rwillett

[Mottlefeeder]

16 hours ago, Phil Starr said:

That's a great question and I had to think about the answer. Part of this is that I rely on experience, I've spent a lot of time building and modifying cabs. When I build pairs of cabs I'll often try modifications on one cab and then A/B them next to each other so you do get an instinct about small changes

 

The first thing is that the efffects are slight. First of all most of the 'sound' of the speakers is what goes on above 200Hz and the box modelling is about the response of the true low end below that frequency. The other David has tried the cab out as a sealed cab andit 'works' and it probably sounds OK, even though he will get 3db of boost of the low end with a port plus a lower roll of frequency.

 

Secondly the calculations give incredibly percise answers but in real life it's a bit messier. Manufacturing tolerances mean measured speakers vary and the published figures I use can't always be trusted. Thre are always air losses from a cab which are allowed for in the calculations but I use a 'standard' value of Ql=0.7 which is middle of the bell curve. Importantly I then build the cab so ay significant error would show up. I'ver no control over how accurately people build the cab so calculating port sizes to 3 decimal places doesn't make much sense. You can build the cab successfully even if you make small mistakes, which should be reassuring

 

Anyway I've looked at the responses with the same tuning and the box sizes increased and decreased by 10% but tuned to the same frequency.  This is the box you are all building with the Fane in blue. You can see that increasing the cab by 10% (red) gives you a bit more bass but reducing the cab 10% makes a smaller difference. The red trace gives 1db extra at 60Hz and you'd hear that with the cabs next to each other but only just. You wouldn't be able to detect the difference with the smaller cab in this case. This is a 2l shift in volume and the increase in port size is only 0.2l so insignificant. It looks like my instincts were good in this case, Phew

 

 

 

Thanks for the clarification. I shall stop trying to calculate the difference in volume caused by the port wall increasing from 2mm to 12mm!

David

[Phil Starr]

9 hours ago, Mottlefeeder said:

Thanks for the clarification. I shall stop trying to calculate the difference in volume caused by the port wall increasing from 2mm to 12mm!

David

I'm an unreformed fiddler, nothing I ever do get's finished. I always have mods I want to try. In this case I thnk you could set a limit/tolerace of 2% of cab volume and be perfectly safe and maybe 10% would be liveable with.

 

There's always more mods I want to add so I'm finding publishing designs and seeing them live on as a stable design a new experience. I decided early on that designs had to be built and tested before publishing and nowadays I have to refer back to my own designs on BassChat to answer questions

[djk]

On 29/01/2026 at 08:00, Phil Starr said:

That's a great question and I had to think about the answer. Part of this is that I rely on experience, I've spent a lot of time building and modifying cabs. When I build pairs of cabs I'll often try modifications on one cab and then A/B them next to each other so you do get an instinct about small changes

 

The first thing is that the efffects are slight. First of all most of the 'sound' of the speakers is what goes on above 200Hz and the box modelling is about the response of the true low end below that frequency. The other David has tried the cab out as a sealed cab andit 'works' and it probably sounds OK, even though he will get 3db of boost of the low end with a port plus a lower roll of frequency.

 

Secondly the calculations give incredibly percise answers but in real life it's a bit messier. Manufacturing tolerances mean measured speakers vary and the published figures I use can't always be trusted. Thre are always air losses from a cab which are allowed for in the calculations but I use a 'standard' value of Ql=0.7 which is middle of the bell curve. Importantly I then build the cab so ay significant error would show up. I'ver no control over how accurately people build the cab so calculating port sizes to 3 decimal places doesn't make much sense. You can build the cab successfully even if you make small mistakes, which should be reassuring

 

Anyway I've looked at the responses with the same tuning and the box sizes increased and decreased by 10% but tuned to the same frequency.  This is the box you are all building with the Fane in blue. You can see that increasing the cab by 10% (red) gives you a bit more bass but reducing the cab 10% makes a smaller difference. The red trace gives 1db extra at 60Hz and you'd hear that with the cabs next to each other but only just. You wouldn't be able to detect the difference with the smaller cab in this case. This is a 2l shift in volume and the increase in port size is only 0.2l so insignificant. It looks like my instincts were good in this case, Phew

 

 

 

 

On 29/01/2026 at 08:00, Phil Starr said:

That's a great question and I had to think about the answer. Part of this is that I rely on experience, I've spent a lot of time building and modifying cabs. When I build pairs of cabs I'll often try modifications on one cab and then A/B them next to each other so you do get an instinct about small changes

 

The first thing is that the efffects are slight. First of all most of the 'sound' of the speakers is what goes on above 200Hz and the box modelling is about the response of the true low end below that frequency. The other David has tried the cab out as a sealed cab andit 'works' and it probably sounds OK, even though he will get 3db of boost of the low end with a port plus a lower roll of frequency.

 

Secondly the calculations give incredibly percise answers but in real life it's a bit messier. Manufacturing tolerances mean measured speakers vary and the published figures I use can't always be trusted. Thre are always air losses from a cab which are allowed for in the calculations but I use a 'standard' value of Ql=0.7 which is middle of the bell curve. Importantly I then build the cab so ay significant error would show up. I'ver no control over how accurately people build the cab so calculating port sizes to 3 decimal places doesn't make much sense. You can build the cab successfully even if you make small mistakes, which should be reassuring

 

Anyway I've looked at the responses with the same tuning and the box sizes increased and decreased by 10% but tuned to the same frequency.  This is the box you are all building with the Fane in blue. You can see that increasing the cab by 10% (red) gives you a bit more bass but reducing the cab 10% makes a smaller difference. The red trace gives 1db extra at 60Hz and you'd hear that with the cabs next to each other but only just. You wouldn't be able to detect the difference with the smaller cab in this case. This is a 2l shift in volume and the increase in port size is only 0.2l so insignificant. It looks like my instincts were good in this case, Phew

 

 

 

Phil, just to confirm, yes it does sound OK as a closed cabinet, however I do thing that is does lack a little "bottom end". I've only been able to try it in the dinning room so far, will be taking it to a jam session on Sunday, and while it does shake the chandelier even at low volume the port will make a difference. Hopefully I'll add the port in the next week or so and will let you know.

 

Thanks again for everything

David 

[Phil Starr]

The port will add noticeably more bass. I hope you will be happy with it. For the jam session see if you can get the cab in a corner and the bass will be reinforced by the room.

[FirstBass]

I fitted a slightly larger port on mine.

 

Cab size was slightly increased to compensate for the larger port and multitude of bracing. 

 

I tuned the port to frequency using the rattly rice on the cone technique.

 

The bass output of this cab is quite surprising! Especially with corner placement as Phil says. 

 

I've got the bits to knock a second up. I think it'd make a very transportable/practical/ cute/funny/great sounding rig for "sensible" practices and gigs. 

 

Maybe four? I have a 2 ohm stable amp 😁

[tauzero]

8 hours ago, FirstBass said:

I've got the bits to knock a second up. I think it'd make a very transportable/practical/ cute/funny/great sounding rig for "sensible" practices and gigs. 

 

Maybe four? I have a 2 ohm stable amp 😁

 

Two 1x8s and a 2x8 for playing Wembley stadium?

[rwillett]

Finally got most of the second cab finished, its nicknamed Goth as its very, very black. It still needs a grill but that next weeks work and I was keen to see how it sounded in a stack, it maybe a small one (where have I heard that before) but it's still one speaker cabinet on top of the other. Checked it sounds OK on its own, stacked it on and the tried to fit the cheapo NL4 SpeakOn -> SpeakOn cable a friend gave me. 

 

The dammed cable won't fit in the Speakon sockets I have. I have just checked with Blue Arran and the order says NL4 sockets https://www.bluearan.co.uk/index.php?id=TUFF87182NU, the cable given to me has four metal plates inside the plastic tube but I can't twist the cable to fit at all. The centre prong in the NL2 is almost a half moon, whilst the cheap NL4 cable is most of a circle. 

 

@Chienmortbb made me two 1/4" Jack -> NL2 cables, a short one and a slightly shorter one and they fit into the NL4 sockets easily and smoothly.   The cheap cable feels bloody awful and cheap. 

 

Not sure if my problem is that I have NL4 sockets in a single speaker cab AND/OR I have a crap NL4 cable ( @Chienmortbb's cable works fine) or I have missed the point completely and it's something else. Each speaker works fine on it's own with Johns cable's. I just can't join the cables together. 

 

All and any suggestions welcomed. Once I get it working and I have the grill, I'll post pictures.

 

Thanks

 

Rob

 

 

 

 

[3below]

Not sure what is going on but I have had problems with speakon copy plugs.  Genuine Neutrik plugs & sockets work perfectly. 

[rwillett]

1 minute ago, 3below said:

Not sure what is going on but I have had problems with speakon copy plugs.  Genuine Neutrik plugs & sockets work perfectly. 

I suspect you are right. The spring tag on the cheapo one feels horrid, the Neutrik feels far nicer. 

 

I suspect @Chienmortbb might be getting another order soon. 

[Stub Mandrel]

1 hour ago, rwillett said:

Finally got most of the second cab finished, its nicknamed Goth as its very, very black. It still needs a grill but that next weeks work and I was keen to see how it sounded in a stack, it maybe a small one (where have I heard that before) but it's still one speaker cabinet on top of the other. Checked it sounds OK on its own, stacked it on and the tried to fit the cheapo NL4 SpeakOn -> SpeakOn cable a friend gave me. 

 

The dammed cable won't fit in the Speakon sockets I have. I have just checked with Blue Arran and the order says NL4 sockets https://www.bluearan.co.uk/index.php?id=TUFF87182NU, the cable given to me has four metal plates inside the plastic tube but I can't twist the cable to fit at all. The centre prong in the NL2 is almost a half moon, whilst the cheap NL4 cable is most of a circle. 

 

@Chienmortbb made me two 1/4" Jack -> NL2 cables, a short one and a slightly shorter one and they fit into the NL4 sockets easily and smoothly.   The cheap cable feels bloody awful and cheap. 

 

Not sure if my problem is that I have NL4 sockets in a single speaker cab AND/OR I have a crap NL4 cable ( @Chienmortbb's cable works fine) or I have missed the point completely and it's something else. Each speaker works fine on it's own with Johns cable's. I just can't join the cables together. 

 

All and any suggestions welcomed. Once I get it working and I have the grill, I'll post pictures.

 

Thanks

 

Rob

 

 

 

 

 

"NL2 Speakon cables (2-pole) are compatible with both NL2 and NL4 panel jacks, while NL4 cables (4-pole) only fit NL4 jacks, creating a one-way compatibility. A 2-pole plug works in a 4-pole socket because it uses the 1+ and 1- contacts, but a 4-pole plug is physically too large for a 2-pole socket."