12" Cab Diary Continued

[Phil Starr]

On 20/05/2021 at 21:02, funkydoug said:

Thanks  Stevie.  

I'm tempted to ask why it is so component specific, 

 

Stevie is the expert on crossovers but at the simplest level speakers are all different, none of them have completely flat responses and the mechanical and electrical characteristics of each speaker are different too. Adding a horn flare loads the speakers changing the load on the speaker and this changes thigs too. The horn will also have it's own frequency response. Even at the easiest level most horns are louder than bass units but never by the same amounts, so you have to sort that out too.

I've used generic crossover designs and used simple design theory to calculate crossover component values. It works in that you split the signal between the drivers bass goes through the bass speaker and treble through the horn but it is only a starting point. the sound in the crossover region is rarely good. I then (theoretically anyway) do a lot of fiddling, unwinding coils or adding turns and messing with resistor and capacitor values with repeated listening tests to get it as clean as I can subjectively. Stevie does it by measurement and years of experience and his crossovers sound better than mine.

[Phil Starr]

On 21/05/2021 at 13:39, sergelebasse75 said:

Thanks a lot chienmortbb Stevie Phil and all the people involved, now i already have woofer and tweeter, Next step, inductors!😃

Hi Serge, Stevie is shy about this but I'm not as I have no financial interest. I also know how difficult it is to source inductors of the right values and power handling.

He sells inductors on Evil Bay including winding custom values. I hope I'm not breaking any BassChat rules by putting this up but here is the link 133768834024 | eBay that's for the 10" driver but all the other inductors are available.

[stevie]

😁 Just a little sideline of mine..... As I have all the equipment and the know-how, I help speaker builders out by custom winding hard-to-find inductors at very reasonable rates. It's not going to make me rich, but it's very satisfying.

[sergelebasse75]

And that s an offer, Phil, that I cant deny, if you could do this for me, I would thank you so much. Just pm me with details, if you prefer so method or another. It will be fine for me.

[FirstBass]

Hi

I'd like to build V3 of this cab for use with an SM212 (not too bothered about weight and I already have 2 of them) and the latest HF driver

Could anyone point me in the direction of the crossover for this combination? 

I'm ok with the building part, but crossovers confuse me...

Any assistance would be appreciated

[nekomatic]

The crossover for the Beyma is a few posts up on this thread

I believe this is technically the Mark 2 version of the cab, while Mark 3 is the one with the Faital Pro LF and a more expensive Celestion HF driver.

Stevie has just sorted me out with the components for this crossover at a very reasonable price so if you want to build one too I would highly recommend asking him. 

The thing you may have an issue with is getting hold of the PH-170 horn - nobody in the UK has them in stock before September...

 

[Chienmortbb]

I have a spare PH170 horn and  the Compression driver CDX1-1445 as used with the crossover I posted on the last page. PM me if interested.

Edited June 8, 2021 by Chienmortbb

[osborne900]

Somewhat late to this party but, hopefully, about to get my hands on one of these cabs unfinished shortly. I’m wondering if going to the Faital 12FH500 would confer any advantage over the 12PR320 aside from the obvious better power handling. I’ll be using it with a TC BH800 which, running into 8 ohms, should give me a bit of a margin. Also, it seems the PH170 flare is not available at present so, are there any alternatives that fit in the hole.

Many thanks for a brilliant project.

[stevie]

The 12FH500 is a very nice driver - I've got some 12FH520s in my workshop. It sounds a bit leaner in the bass than the 12PR320 but it's very well defined. Unfortunately, its midrange response is different, which means it would need a crossover redesign to get the best out of it.

It's a shame there's such a delay with the horns. If I'd known, I'd have specified something that's more readily available. The horn's integral to the design, I'm afraid. Fitting another horn is possible but would also require a different crossover.

 

[osborne900]

Thanks for your thoughts @stevie. I’m not sure I’m going to need the tweeter as I find an 8pr200 plenty bright enough for me which rolls off around the same point (ish)and I’m missing my top octave anyway (getting old). That being said, if I do add the tweeter when the flares become available it will be a sight easier if I use the 12PR320. The frame on the FH5*0 units looks gorgeous as well not the you ever see it once installed and really shouldn’t be a consideration but who doesn’t love the look so a sexy chassis. Food for thought.

[nekomatic]

Glad to see I’m not the only fan of a well proportioned chassis 😁

[Triumph_Rock]

Hi guys, late to the party,

I'm looking at building my first cab. I can no longer see the photos or plans posted upto page 3.

Does anybody still have the plans? And could post them here or send me them by pm?

 

[stevie]

The PDF plans are attached to the first post in the thread. Unfortunately, we lost all the photos of the initial builds but I reposted all the later ones showing the cabinet build process in detail. Also, check out funkle's build thread, which also contains useful info.

[stevie]

On 16/07/2021 at 22:13, osborne900 said:

Thanks for your thoughts @stevie. I’m not sure I’m going to need the tweeter as I find an 8pr200 plenty bright enough for me which rolls off around the same point (ish)and I’m missing my top octave anyway (getting old). 

It's worth repeating that the on-axis frequency response of the bass driver, whether it's a 12 or an 8, is less relevant than you might think because you hardly ever listen to a bass cab directly on-axis.

When you're standing above or to the side of a cab, the midrange and HF frequencies are greatly attenuated. The horn in this design crosses over at 2kHz (more than an octave lower than most commercial designs) to compensate for this and allow you to hear those mid and high frequencies clearly - even when you're above and to the side of the cab.

Also, if you're playing without PA support, what your audience hears is not the on-axis sound from your cab but the 'power response' or the sum total of the speaker's radiated output. This is why live bass often sounds dark and murky with no energy even if a cab has a tweeter.

 

[osborne900]

On 19/07/2021 at 11:30, stevie said:

It's worth repeating that the on-axis frequency response of the bass driver, whether it's a 12 or an 8, is less relevant than you might think because you hardly ever listen to a bass cab directly on-axis.

When you're standing above or to the side of a cab, the midrange and HF frequencies are greatly attenuated. The horn in this design crosses over at 2kHz (more than an octave lower than most commercial designs) to compensate for this and allow you to hear those mid and high frequencies clearly - even when you're above and to the side of the cab.

Also, if you're playing without PA support, what your audience hears is not the on-axis sound from your cab but the 'power response' or the sum total of the speaker's radiated output. This is why live bass often sounds dark and murky with no energy even if a cab has a tweeter.

 

Good point, well made. Even though I find the 8pr200 adequately bright for my cloth ears, off axis the 12pr320 rolls off an octave earlier. I imagine even I might notice that. I’ll keep my eye out for a ph170.

[Phil Starr]

[Chienmortbb]

On 20/05/2021 at 20:13, stevie said:

1mm or 1.2 mm for the bass inductor.  .7 or .8mm for the .5mH value and .6mm for the 1.1mH value inductor, although thicker wire won't do any harm if your choice is limited. Resistors should ideally be 20W. I'd also double up on the resistors in the LF circuit, i.e. 2 x 2.2 ohms for extra power handling. Don't bother with esoteric capacitors. They're a waste of money IMO. But do use film type caps and not electrolytics.

I agree about the esoteric caps.

[FirstBass]

I know this is going back in time a fair bit, but....

 

Does anyone have the crossover details of the SM212 + PHT407 version of the cabinet please? (Mk2 I believe)

 

I have 2 of each unit and would like to make use of them, but can't see the crossover image

 

I'd appreciate any help

 

Jon

 

[stevie]

I'll have a look and let you know what I can find. I'm currently under pressure with work deadlines, but somebody else might have the circuit. 

[Gottastopbuyinggear]

That was a very timely question as I was thinking about asking the same thing.  Also, was the Mk 2 the same internal volume as the Mk 1?

 

The reason for the interest and question is that I built and still gig two of the Mk 1 cabs, but feel the need to add a tweeter in one of them to help with my own hearing of the bass when I’m standing very close to the cabs, which I often am in the pubs etc. that we play.  Casting my mind back a few years I *think* (though I’m not entirely sure) that the Mk 2 might have been the same internal volume but with slightly different overall dimensions, and likewise *think* that I worked out that I could fit the SM212, tweeter and manrose pipe based port in the Mk 1 front panel footprint.

 

And there’s a third question, too - if I wanted to adjust the port dimensions to tune the cab a bit higher then would that  cause any problem based on the crossover design… always assuming there’s still a record of it somewhere…

 

Hope that all makes sense - I’m one or two glasses of a rather nice Malbec in…

[Stub Mandrel]

I'm visualising a cab with a single 10" or 12" speaker and an angled section on top with a 5" speaker beaming the mid-range at the player's head.

[JohnDaBass]

13 hours ago, Gottastopbuyinggear said:

 *think* that I worked out that I could fit the SM212, tweeter and manrose pipe based port in the Mk 1 front panel footprint.

Hope that all makes sense - I’m one or two glasses of a rather nice Malbec in…

Yup!! That makes a lot of sense.

One of my Mk1 SM212 cabs has a removable baffle so cutting a new baffle would be straightforward to include the Manrose port and additional horn.

[StickyDBRmf]

So I just read Barefaced website and it seems the speakers they produce would eliminate the need for mids and tweeters. Now I know more than I need and still don't know what a decent amp/speaker set-up would be for a Chapman Stick, that happens to play a lot of bass notes consecutively, unless I'm playing in the higher range, with or without distortion. (Have any of you read the Barefaced website?)

[LukeFRC]

43 minutes ago, StickyDBRmf said:

So I just read Barefaced website and it seems the speakers they produce would eliminate the need for mids and tweeters. 

Now I know Alex is really really passionate about what is probably some of the best basscabs on the market... but the presence of the Big Baby and Big twin in their lineup would suggest even he would use a horn  on some cabs. 
Someone will be on to explain better but I think it's down to dispersion.... 

[Chienmortbb]

16 hours ago, LukeFRC said:

Now I know Alex is really really passionate about what is probably some of the best basscabs on the market... but the presence of the Big Baby and Big twin in their lineup would suggest even he would use a horn  on some cabs. 
Someone will be on to explain better but I think it's down to dispersion.... 

Yes for instance there is little above 1KHz off axis on a 12 even though the spec suggests otherwise. Even with an extended on axis response, there is often a nasty effect where the cone starts to behave in an erratic manner (often called cone breakup). 

 

You can clearly see this effect on the link to th graph for an Eminence Keappalite 3012 LF.

 

 

We are looking at the peak at approx 1.7KHz. The one thing this graph does not show is the OFF AXIS response.

 

This Beyma 12" response, shows the 45 degree off axis response dotted:

 

So at 2 KHz the output is 8-10dB down compared to the output from 200Hz to 1KHz. Incidentally the driver(s) in a single cabinet on the floor will be about 45 degrees from your ears if you are 1-2m in front of it. So it is not only the audience to your left and right that are losing out on your lovely tone.

 

Smaller speakers have better OFF AXIS responses as can be seen by the frequency response graph for the Beyma 6CVM2.

 

 

At 2KHz the fall is "only" 4dB and there is output much higher up the spectrum. @Phil Starr recently built a 6" cab loaded with a Fane 6" driver that was well received at the recent South West Bass Bash.

 

Edited October 29, 2021 by Chienmortbb