12" Cab Diary Continued

[Phil Starr]

Some of you will have noticed that I am (very slowly) trying to archive the BC designs so that people can go on building them. What has become apparent is that many of the parts have become unavailable though substitutes are always coming through as well. I'm going to tweak the designs as I go and one of the things I will do is move to only using standard building pipes as ports as the pre formed ones only seem to have short runs. The horns too have short lives it seems.

 

I'll double check but I think the Mk1 was very slightly bigger than the Mk2/3, Both nominally 50l but I allowed slightly more 'extra' space in the Mk1 to allow for extra intrusions into the cab. So long as you use the Mk1 ports in the Mk 1 cab and Mk2 ports with Mk2 cab it won't be an issue. The shape was a result of requests that the cab should take an old heavy iron 19" amp with no overhang. My intention is to do an 'easy build' version of Stevie's mk3 shape cab as a revision for the Mk1 and that will go up eventually. In the meantime you can build the Mk3 shaped cab without a horn if you want.

 

Retrofitting a horn has always been an option though you'll need a new baffle as I didn't leave enough space for the specified horn in the Mk1. The horn/crossover for the Celestion 1445 version of the Mk2 is still up on the thread and that was my favourite combination.

 

Stevie is our crossover expert but I don't think changing the cab will make a significant difference at the crossover point but changing the horn or compression driver will as he pays a lot of attention to anomalies here and is very careful about the matching of horn and driver . 

 

@Gottastopbuyinggear I'm not sure why you would want to build a Mk1 with a higher tuning? Stevie and I differed over the preferred tuning and it is possible to come up with a series of tunings that will work well each achieving different compromises. There's a lot of discussion about it in the original thread I believe. The effects are complex and affect power handling, excursion and the shape of the response well away from the tuning frequency. We did listening tests too before we settled on the recommended tuning. There's lots of good reasons for tweaking the tuning but it certainly isn't as simple as taking out a bit of bass by tuning higher. Let me know what you are trying to achieve and we can see what the options are, you might be better off reducing the size of the cab for example. There's a lot of psychoacoustics involved too, just adding the horn will make your cab sound less bass heavy.

[Gottastopbuyinggear]

46 minutes ago, Phil Starr said:

 

@Gottastopbuyinggear I'm not sure why you would want to build a Mk1 with a higher tuning? Stevie and I differed over the preferred tuning and it is possible to come up with a series of tunings that will work well each achieving different compromises. There's a lot of discussion about it in the original thread I believe. The effects are complex and affect power handling, excursion and the shape of the response well away from the tuning frequency. We did listening tests too before we settled on the recommended tuning. There's lots of good reasons for tweaking the tuning but it certainly isn't as simple as taking out a bit of bass by tuning higher. Let me know what you are trying to achieve and we can see what the options are, you might be better off reducing the size of the cab for example. There's a lot of psychoacoustics involved too, just adding the horn will make your cab sound less bass heavy.

I think ignorance is probably the issue here, @Phil Starr!   Again I’m casting my mind back a while so I may be remembering incorrectly, but I think I tried modelling the removal (or at least blocking) of one of the four ports in WinISD and it lowered the bass response and gave a bit of a low mid hump around the 100 to 130 Hz mark, which I thought would probably be a reasonably pleasing bump.  But we all know that a little knowledge can be a dangerous thing, and I could well be speaking out of my own rear port…!

 

There’s two things I thought I might be able to achieve - 1. decrease the low bass, as the cabs used together can be quite overwhelming, and 2. improve dispersion (?) to make it easier to hear myself when I’m standing very close to the cabs.  I could experiment with 1 pretty easily by just blocking a port in each cab.  2. will take a bit more work as I’ll need to make new baffles, but I built both cabs with removable baffles so it’s entirely achievable.

 

If reducing the volume of the cab turned out to be worth trying then what would be the lightest material I could introduce to take up some space?

 

Oh, and feel free to let me know just how much nonsense I’m talking!

[LukeFRC]

I've read around this subject and the science behind it enough to know that the easiest way to a good result is finding some proven plans and following something when someone else has poured their time and expertise into! 

[Phil Starr]

Yes i remember gigging with the prototypes, they could be overwhelming  My drummer at the time once repeatedly asked me to turn it up, so I did, at the end of the first set he said 'I couldn't hear my effing snare drum'

 

covering one port won't be enough to make a real difference try going down to two. This is what it will do to frequency response

 

The trouble is that it also affects power handling and potentially port noise. this is power handling. 180W @70Hz isn't too bad but you need to know

 

[bassman7755]

8 hours ago, Phil Starr said:

Yes i remember gigging with the prototypes, they could be overwhelming  My drummer at the time once repeatedly asked me to turn it up, so I did, at the end of the first set he said 'I couldn't hear my effing snare drum'

 

covering one port won't be enough to make a real difference try going down to two. This is what it will do to frequency response

 

 

Surely if all you want is this minor EQ tweak then its better to achieve it earlier in the signal chain (pickup mix, instrument tone controls, an EQ effect, amp tone controls etc) - the speaker is surely the worst place to do it as your wasting power and efficiency. 

Edited October 29, 2021 by bassman7755

[JPJ]

I really fancy building a couple of the MkIII cabs but whilst I’m a proficient wood butcher, I wouldn’t trust myself to assemble the crossover without a fair chance of a spectacular failure.

So here’s a thought, if there is a fellow basschatter with the reverse skill set, I’d be up for bartering my time assembling a cab for you if you’d build two crossovers for me? Material costs to be covered by each party.

[Phil Starr]

16 hours ago, bassman7755 said:

 

 

Surely if all you want is this minor EQ tweak then its better to achieve it earlier in the signal chain (pickup mix, instrument tone controls, an EQ effect, amp tone controls etc) - the speaker is surely the worst place to do it as your wasting power and efficiency. 

I think it is a question of a design choice. You can design a flat response speaker and then use eq/modelling to get the sound you want and that is how the Mk3 was designed. Or you can decide to 'voice' the speaker to make a satisfying sound 'out of the box'. Different people prefer different approaches. I don't think it's about right or wrong, for me it is abut what works.

 

It isn't really about efficiency or wasting power. the blue line (higher tuning) shows an extra 2db at 100Hz and the red and extra 2db at 40Hz, so which is louder? They are both the same sensitivity for the majority of their response. I designed the MK1 to give a satisfying result for a first time builder and gigged it extensively to check that it worked in a band situation. 

 

The secondary aim of these threads is to de-mystify cab design, there are lots of these little tweaks in commercial designs where the compromises are made for you. When it comes to something simple like this where blocking a couple of ports lets you hear the difference at home and decide for yourself then it's a perfectly sensible thing to ask and try out. @Gottastopbuyinggear might well decide the decisions I took all those years ago weren't right for his needs today.

[JPJ]

I’ve read through the build threads and unless I’ve missed it, there’s one question I think hasn’t been answered. Is the physical proportions of a cab as important as the internal volume. Obviously, there are a few fixed dimensions (diameter of the speaker, length of the port) but other than these practical limitations will a short deep cabinet perform  differently to a taller but slimmer design?

[FirstBass]

So.... I was searching through my laptop last night and stumbled upon the attached

 

YES!

 

MK2 crossover and cab plans

 

Crossover options of either the P audio or Celestion HF element of the cab

 

I'm rather chuffed!

 

Hopefully there weren't any mods to the crossovers after I saved these

 

 

[Phil Starr]

18 hours ago, JPJ said:

I’ve read through the build threads and unless I’ve missed it, there’s one question I think hasn’t been answered. Is the physical proportions of a cab as important as the internal volume. Obviously, there are a few fixed dimensions (diameter of the speaker, length of the port) but other than these practical limitations will a short deep cabinet perform  differently to a taller but slimmer design?

Ok good question I'll give the answer in two parts.

 

The volume of the cab is very important as it has frequency dependant elements and non-frequency dependant effects. It acts as a mass on the back of the cone, a spring and a sponge and that is in any speaker cab. In a ported there is the added complication as it acts as part of a tuned couplet with the port. The conventional theory on speaker design changes all these things into resistive, capacitative and indictive elements and crunches all the elements of the cab and the driver to balance them all out into a workable cab. The volume and the tuning of the cab have all been calculated to match the speakers we use and then we've built and tried them to make sure they meet the specs we started out to achieve. The shape of this volume matters far less than the volume and tuning, the differences caused by shape will be less noticeable and some will be below our ability to detect them.

 

The real issue with changing the shape of the cab are resonances. It's quite possible for a resonating panel to put out as much sound as the speaker and you can both hear and measure resonances. There are also resonances in the air of the cab and in the port itself. The frequency of the resonances are set by the dimensions of the panels, their flexibility and their masses. If you are sticking to plywood as in all our designs then it's only the dimensions of the panels that are changing so you'll be shifting the resonances upwards with smaller dimensions and down with longer ones. The worst thing you can do is to repeat dimensions so panels all resonate at the same time. The worst shape is a cube and the ideal is one which sticks to the golden ratio (roughly 1.6:1)

 

The advantage of using a ready made design like ours is that a lot of this work is done for you. In the later designs cab resonances have been looked at and bracing suggested where needed. The joy of a self build however is that you can personalise your  build and let's face it there are only a limited number of options open to you if everything is to fit in. You'd probably have to be very unlucky to hit a truly awful resonance and so long as you know to look you can always find the resonances with your fingertips and knowing about them gives you the chance to deal with them by bracing the panel concerned.

[The fasting showman]

Hi Phil,

Given that I'm currently building the 30l cab I find myself on the wrong thread, however the answer may be relevant to both 30 & 50 litres; is the Faital 12 FE300 a suitable speaker as a replacement / substitute for either of the Beymas? Apologies if the answer is a few pages back on the thread.

Due to them being on order I can't obtain a 12cmv2 at present, I fear I may have to save up for a Faital Pro 12!

 

Many thanks,

Martin

[nekomatic]

On 31/10/2021 at 08:57, carnabass said:

MK2 crossover and cab plans

 

Crossover options of either the P audio or Celestion HF element of the cab

 

I'm rather chuffed!

 

Hopefully there weren't any mods to the crossovers after I saved these

 

Well… I don't know about the P Audio HF but the circuit you've posted for the Celestion HF is not the same as the one @Chienmortbb posted a couple of pages ago…

 

I'm sure they'll both work though (I hope, because I'm in the middle of building the latter one!)

[Phil Starr]

3 hours ago, The fasting showman said:

Hi Phil,

Given that I'm currently building the 30l cab I find myself on the wrong thread, however the answer may be relevant to both 30 & 50 litres; is the Faital 12 FE300 a suitable speaker as a replacement / substitute for either of the Beymas? Apologies if the answer is a few pages back on the thread.

Due to them being on order I can't obtain a 12cmv2 at present, I fear I may have to save up for a Faital Pro 12!

 

Many thanks,

Martin

Hi Martin, I haven't modelled either the Faital Pro 300 or the 320 in the 30l cab. I'll have a look sometime in the next couple of days and let you know what I think. I did look at the m both in another context and concluded that as a single driver I preferred the look of the top end response of the 320. Anyway Until it's been modelled I'll keep my powder dry. I'll also look to see if there are any other cost effective alternatives.

[The fasting showman]

52 minutes ago, Phil Starr said:

Hi Martin, I haven't modelled either the Faital Pro 300 or the 320 in the 30l cab. I'll have a look sometime in the next couple of days and let you know what I think. I did look at the m both in another context and concluded that as a single driver I preferred the look of the top end response of the 320. Anyway Until it's been modelled I'll keep my powder dry. I'll also look to see if there are any other cost effective alternatives.

That's great Phil, much appreciated. 

[Chienmortbb]

6 hours ago, nekomatic said:

 

Well… I don't know about the P Audio HF but the circuit you've posted for the Celestion HF is not the same as the one @Chienmortbb posted a couple of pages ago…

 

I'm sure they'll both work though (I hope, because I'm in the middle of building the latter one!)

I would need to have a look at both some time but mine was redrawn from the original hand drawn diagram from @stevie. There may have been small changes after that. I seem to remember that any changes were very small. @stevieis a perfectionist and the chnages would probably not be noticeable in real life.

Edited November 1, 2021 by Chienmortbb

[Phil Starr]

12 hours ago, The fasting showman said:

That's great Phil, much appreciated. 

OK I've had a quick look. This is the  two Faital's the 12PR300 (green) and the 12Pr320(purple) in the 30l cab with the 12CMV2(red) for comparison. The box is quite small for pretty much any 12" speaker so they all show a hump above 100Hz. The 12PR300 has the flattest response and the Beyma has the biggest hump and is about 1db louder below 100Hz than the others, that's just noticeable. the 2db hump centred on 120Hz is very noticeable and some people like it. The flatter response of the 300 is nice, it will mean it is going to sound cleaner and will take to eq more easily. They aren't terribly different, the bass response is determined by the size or the box which is fairly extreme or a 12. however they all pass my test o the -3db point being below 80Hz meaning they will all give a decent response of the crucial 2nd harmonics of a four string.

 

[Phil Starr]

I ran one other speaker the Fane 12-300 Pro because it is on special offer at the moment, and in stock at Blue Aran £64.88. At this point I need to know what you want,  is cost the driving factor? Is light weight more important? Do you prefer an old school coloured sound or is clean more important? What are you going to use the speaker for, mainly practice or regular gigging once that returns? How powerful is your amp? 

 

This is the Fane (solid line) compared with the 12PR300.

 

[The fasting showman]

5 hours ago, Phil Starr said:

I ran one other speaker the Fane 12-300 Pro because it is on special offer at the moment, and in stock at Blue Aran £64.88. At this point I need to know what you want,  is cost the driving factor? Is light weight more important? Do you prefer an old school coloured sound or is clean more important? What are you going to use the speaker for, mainly practice or regular gigging once that returns? How powerful is your amp? 

 

This is the Fane (solid line) compared with the 12PR300.

 

Many thanks Phil, that's great. The cab will be used at pub gigs with a pop / soul covers band I have recently joined, electronic drums, decent PA with a sub, guitar DI'd through a Helix. I have been using my DIY 1x10 cab (Basslite 2010), my head is a Gallien Krueger 700RBii which is about 300w into 8 ohms. My bigger band/ swankier gig setup is a GK neo 2x12 but those gigs are few and far between!

I play a G&L 5 string or an old Fender with flats, nothing really much below 100 hz ( that's why the GK stuff appeals to me if I'm honest) I prefer a fast sound to a sound that swells or blooms if that makes sense. I tend to raise a cab physically to where I can hear it rather than cranking the dials too much. The Faital pro12pr 300 is looking a contender!

Cheers, Martin

[Phil Starr]

How far have you got with the build? The port/s will need a bit of adjustment for this speaker. 

 

I think the 12PR300 is a good choice for this cab, normally I'd say spend teh extra for the 12PR320 but it really needs a bigger cab to get the best out of it. The only thing you really lose is that the excursion on the 300 isn't as good. You'll end up with a really lightweight portable cab though.

 

One thought though is that I think Stevie's 2-way BC112T mk3 might suit you best of all, maybe even making the GK redundant. It's not the extra top end of the tweeter but the smoothness of the midrange response that you might like. If you went with the 320 you could use that in the new cab. However the 300 in the small cab promises a really lightweight portable solution.

 

 

[The fasting showman]

9 minutes ago, Phil Starr said:

How far have you got with the build? The port/s will need a bit of adjustment for this speaker. 

 

I think the 12PR300 is a good choice for this cab, normally I'd say spend teh extra for the 12PR320 but it really needs a bigger cab to get the best out of it. The only thing you really lose is that the excursion on the 300 isn't as good. You'll end up with a really lightweight portable cab though.

 

One thought though is that I think Stevie's 2-way BC112T mk3 might suit you best of all, maybe even making the GK redundant. It's not the extra top end of the tweeter but the smoothness of the midrange response that you might like. If you went with the 320 you could use that in the new cab. However the 300 in the small cab promises a really lightweight portable solution.

 

 

Hi Phil, all woodwork done...I was a coward and bought Monacor MBR 70 telescopic ports, 66mm internal. There seems to be plenty of pr12 300s available so that's reassuring that you are happy with the recommendation.

Many thanks,

Martin

 

[Phil Starr]

That's great, the whole point of a self build for me is that you can take control and customise. To get that response I raised the tuning to 55Hz so with two ports you need them to be around 15.5 cm

[stevie]

On 31/10/2021 at 08:57, carnabass said:

So.... I was searching through my laptop last night and stumbled upon the attached

 

YES!

 

MK2 crossover and cab plans

 

Crossover options of either the P audio or Celestion HF element of the cab

 

I'm rather chuffed!

 

Hopefully there weren't any mods to the crossovers after I saved these

 

 

 

Thanks, Jon. That's very useful.

 

The cab drawings are of the very early prototypes and were revised later. The spruce ply I used for that first prototype was quite resonant and needed a lot of bracing. Later ones were better, allowing me to remove some of the bracing. 

 

I can't recall for sure now, but chances are that the crossover for the MkII with compression driver is the first one I did and published. The circuit I gave to Chienmortbb is likely to be a simplified version (using fewer components). Both will work.

[stevie]

On 29/10/2021 at 14:56, LukeFRC said:

I've read around this subject and the science behind it enough to know that the easiest way to a good result is finding some proven plans and following something when someone else has poured their time and expertise into! 

 

You're not wrong, Luke.

[stevie]

On 30/10/2021 at 17:35, JPJ said:

I’ve read through the build threads and unless I’ve missed it, there’s one question I think hasn’t been answered. Is the physical proportions of a cab as important as the internal volume. Obviously, there are a few fixed dimensions (diameter of the speaker, length of the port) but other than these practical limitations will a short deep cabinet perform  differently to a taller but slimmer design?

 

Interesting question, and the answer is simple. 

 

With the MkIII specifically, the front baffle size and shape was dictated by the parts I wanted to use. I was toying at the time with using an RCF H100 horn and made sure the cab would be tall enough for it to fit. It was then just a matter of calculating the front-to-back dimension based on the total volume I wanted. And then making sure the vent would fit without coming too close to the back of the cab or needing a bend. It worked out well and resulted in a relatively slim cabinet that is easy to carry with a single handle.  

 

There are some theoretical differences between a tall, slim cab and a squat, deep one, but the taller one scores IMO by having the tweeter further from the ground and nearer to your ears. 

Edited November 4, 2021 by stevie

[The fasting showman]

On 02/11/2021 at 21:56, Phil Starr said:

That's great, the whole point of a self build for me is that you can take control and customise. To get that response I raised the tuning to 55Hz so with two ports you need them to be around 15.5 cm

Hi Phil, the Faital Pro PR12 300 arrived today and it sounds great from what I can tell at home, very balanced sound across the neck and will be ideal for pub gigs where you've got the speaker firing into your back on a cramped stage (stage if you are lucky). I've still got some faffing to do with finishing off but I'll PM you the pics when sorted. It's an epic Covid related, toolbox stuck at the house of my Covid stricken boss, a £23 6ft x 2ft 12mm ply hyperbolic paraboloid from Wickes, hand cut panels with that saw you use to cut the end off a tube of silicon...but we got there in the end! Thanks for a great design, Martin