1x12" Cab Design Diary

[funkle]

Beyma SM212 specs - http://www.beyma.com/uploads/ftp/Fichas_Tecnicas/000000730.PDF

Interesting reading. The 98dB @ 1w/1m is an impressive figure. Not too heavy for a ferrite speaker. An apparently economical solution for a 2 or 3 way full range box. Vd of 382 cc and Xmax as you say 7mm.

I wonder if the Xmax of 7mm calculated in the same way that Eminence do their Xmax calculation?

The 3012LF, a high standard of comparison for Xmax in current bass cab drivers (apart from Alex Claber's proprietary 12" driver, where Vd is high - apparently 550cc - but we don't know how it is calculated) has bigger Xmax (9.1mm) and Vd (496cc) but much less efficiency at 1w/1m. I assume the 3012LF would really get going at higher power levels, and I note is rated for 450W RMS. Eminence specs - http://www.eminence.com/pdf/Kappalite_3012LF.pdf

I assume the Beyma SM212 is significantly cheaper than the 3012LF, and would lead to a simpler build? The Greenboy and Audiokinesis builds around the 3012LF are not cheap, I assume due to the extra parts, labour, crossovers, and additional drivers used to cover mid and higher ranges...

[Phil Starr]

That's the weight of one cab! we didn't set out to design a lightweight either.

X max is rated more conservatively than the Eminence speakers. The 3012LF isn't really suitable as a single driver for bass as it is designed as a woofer in a two way speaker and has no top end. The 3012HO is the one we considered. The Beyma is less than half the price in the UK. At the moment US speakers are fairly pricey over here. We felt the 3012HO didn't offer any significant advantage over the beyma except for a midrange hump which we thought would sound nice. We'll give details of alternate drivers in the final design. The Beta 12A-2 looks quite promising.

Remember we set out to create a 'simple to build' design and i may have said something along the lines of more VW Golf than Lamborghini.

Edited July 3, 2014 by Phil Starr

[funkle]

Thanks Phil. You are of course quite right about the 3012LF not being suitable without other drivers in there to cover the gap in freq response higher up. Interesting to know that Beyma rate Xmax more conservatively too.

Really interesting work. I think you have more than met your design brief. The value seems excellent.

IIRC the modified Faital 12PR300 in my Berg CN112 has an estimated Vd of 241cc and Xmax of 4.96mm - and that's using Faital's method of being a bit over generous in their calculation of Xmax. So your cheaper cab will definitely punch out more volume, and do it more evenly than my very voiced cabinet.

[LawrenceH]

Xmax is 8.8 calculated Faital-style. But it's all a bit academic beyond a certain point as different speakers will behave differently with large signals and this is hard to quantify in a single figure even with sophisticated Klippel-type analysers, better to use your ears.

I have said to Phil et al previously, that I think the response in the low-mids plays a big role in how people feel about a speaker, along with the shape/frequency of the resonance peak. Noticeably the Beyma charts show a dip around 300Hz, something I very commonly replicate by EQ as a sound engineer, since it's just a region where you get a lot of wooliness in real-world spaces, and it's also roughly the region where you get a scoop with e.g. Markbass VPF - removing some here often helps clean up or 'tighten' the sound. I will be interested to see if this element of the mf response chart is replicated in Phil's design. It could be a good thing for a lot of players in my opinion, but it'd be interesting to see how a player whose sound is very focused in this region felt about these cabs.

Another issue that's rarely touched on when people get focused on design using T-S-based simulator programs etc is the role of baffle step in the real-world frequency response, which is very problematic to deal with once speaker cabs exceed a certain size, since it becomes so intrinsic to the space. When is 'flat response' truly flat? It's easy to get too hung up about things like modest bumps eg in the midbass, whereas if you saw what any cab response looked like in-room from a particular listening position, you would just give up in disgust! Yet our ears adapt

[LukeFRC]

[Thunderpaws]

I want to build one of these. Have the carpentry skills and tools, have a streamliner 600 and a gb focus 210 cab...hopefully this would be a great partner. Look forward to the plans.....awesome work, knowledge and communication right here.

Edited July 9, 2014 by Thunderpaws

[LukeFRC]

[quote name='Phil Starr' timestamp='1404397522' post='2492291']
That's the weight of one cab! we didn't set out to design a lightweight either.

X max is rated more conservatively than the Eminence speakers. The 3012LF isn't really suitable as a single driver for bass as it is designed as a woofer in a two way speaker and has no top end. The 3012HO is the one we considered. [b]The Beyma is less than half the price in the UK[/b].[b] At the moment US speakers are fairly pricey over here.[/b] We felt the 3012HO didn't offer any significant advantage over the beyma except for a midrange hump which we thought would sound nice. We'll give details of alternate drivers in the final design. The Beta 12A-2 looks quite promising.

Remember we set out to create a 'simple to build' design and i may have said something along the lines of more VW Golf than Lamborghini.
[/quote] this is the bit that has been on my mind and thinking about. I was kinda thinking about building something based around a 3012, either a HO equipped Simplexx or a LF equipped Fearful. One of the things that holds me back is that not knowing massively what I'm looking at but looking around I can see that the US stuff is more expensive than the european stuff.

[LukeFRC]

So this weekend's observation - and I don't know where else to put it so I'll stick it here...

Played bass at a wedding service this sunday, keys/vox/guitar/bass set up.
Well the church we played at has quite a substantial (abet not the newest) PA system set up in it, including big subs.... and quite sensibly in the situation where you get lots of different bass players of different exp used a preamp straight into the desk and then a monitor for the bass player.
Worked quite well - nice bass sound.

Anyway, as I'm setting down I notice the preamp has a switch on giving me a 12dB high pass filter at 80Hz. And it sounded ok!
It made me think about how our rig can/ or can't produce the low end.... and the effect it has.

[Phil Starr]

Hi Luke, probably worth a new thread but firstly churches are often designed for great bass sound in mind, those 32' organ pipes need space to work in and big spaces move all the walls back so removing reflections away from the directly radiated sound. I think this came up in an older thread once, 'how can I get the lovely sound I got in the church'.

There's always been a difference between having good low end response and lots of bass. We are rubbish at hearing really deep bass and most of what we hear is higher harmonics. the first harmonic for bottom E is 83Hz so your filter leaves most of the crucial stuff in. In return you lose a lot of room resonances and your speakers working well within their comfort zone with the coil staying well inside the magnet field keeping everything else cleaner and more accurate. There are lots of successful bass speakers that don't have much deep bass. The classic Ampeg for example.

[Ghost_Bass]

When using an amp with graphic or parametric EQ i always cut everything below 80Hz. Even on the mixer i use the 75Hz HPF on my bass channel. No point in muddying the band's sound with unaudible thump (at least for the kind of music i play, definetly not dub ).

[LukeFRC]

Which, aside from the church related issue is fascinating when it comes to looking at bass amplification- and probably why I wasn't feeling too short changed in my bottom end playing through a HK dart wedge with a -3db point at about 80Hz ... Slightly OT but for me is an eye opener in terms of the compromises in speaker design

[Bill Fitzmaurice]

[quote name='LukeFRC' timestamp='1405894438' post='2506329']I notice the preamp has a switch on giving me a 12dB high pass filter at 80Hz. And it sounded ok!
It made me think about how our rig can/ or can't produce the low end.... and the effect it has.
[/quote]That filter compensates for the difference in response between an electric bass cab and a PA with subs. 80Hz is a bit high, 60Hz would be better. When you go to a concert with big PA and bass that's all boom and rumble with no definition, or for that matter even pitch, it's because the soundman has no clue what electric bass is supposed to sound like, nor how to use his PA kit to get it. By the same token one shouldn't go after an electric bass rig with flat response to 30Hz. If you get it you'll probably regret it.

[fleabag]

[quote name='Bill Fitzmaurice' timestamp='1405944887' post='2506737']
By the same token one shouldn't go after an electric bass rig with flat response to 30Hz. If you get it you'll probably regret it.
[/quote]

Even if you use 5 or 6 string bass ?

[funkle]

[quote name='fleabag' timestamp='1405945301' post='2506748']
Even if you use 5 or 6 string bass ?
[/quote]

I experimented recently with using recording software and EQ through monitors and good headphones to cut out everything below certain frequencies, to see if my perception of bass was significantly altered by trimming low frequencies, and if so, at what point.

This was with a 5 string Modulus Q5 as the tester.

As others will have predicted or known already, cutting out everything with shelving EQ and a steep slope below 30Hz caused no difference to me in bass tone at all (less rumble and low freq crap though, e.g. from hitting fingers on strings). Below 40 Hz - bass still sounded good. Cut off at 50Hz - still sounded good to me. Somewhere around the upper 50s the B string got thinner if I put the shelving point there.

In a live environment I have to cut bass if near wall, corner, etc, and use a HPF or the bass knob on the amp.

So, the question of 'how low do you need to go?' for me is upper 50's through headphones/monitors, and a bit higher using a HPF live, depending upon the room. You wouldn't even need to go that low for a 4 string.

It has helped me to consider further what I want out of a cabinet.

I'm currently trying out one of Duke's Audiokinesis Thunderchild TC112AFv2 (8 ohm) cabs - first cab I have tried with this woofer. From the charts, in the correct box, the 3012LF has enough low end content and has a high Xmax (so you can EQ in more if you want). I have found myself wondering if the 3012LF may even put out too much low end for many indoor venues. The Audiokinesis seems to me well designed in that though they now use a 3012LF stock woofer, Duke specifically aims for -3db around the first harmonic of low B, and I think the cab has a gentle roll off below that point. If you plug the ports on his cabs, the -3db moves a fair bit higher. He also does a lot of work with the crossover to get a smooth on and off axis response. Of course, using the 3012LF in the slightly smaller box size (than e.g. a Fearless F112), he sacrifices sensitivity, though if you have the watts I think you can get it back to some degree through the high Xmax. Still playing with it to figure out its capabilities.

In the studio last week, the Thunderchild put out a ton of bass, and I couldn't get it to fart out even when diming the amp controls (Streamliner 900). I did scare myself by turning up the bass knob ludicrously high on my amp and watching the cone travel much further than I have ever seen...even with my old Acmes. I turned that knob back down pretty sharpish. I guess you can have too much low end content.

It does all seem about the compromises. I'm still learning about all of them. Happy to take corrections if I have made any errors in the above

Pete

[LawrenceH]

Worth remembering that set points for filters are typically -3dB (or even -6). So even if you hear a difference with (say) an 80Hz filter, it's probably as much to do with the signal at 80Hz and up being attenuated rather than below this. Steeper filters allow you to cut lower but can be harder to integrate than shallow slopes, unless it's a true subsonic filter like those built into power amps.

[Bill Fitzmaurice]

[quote name='fleabag' timestamp='1405945301' post='2506748']
Even if you use 5 or 6 string bass ?
[/quote]The f3 of a Fridge is 58Hz, it doesn't seem to bother most five and six string players.

[Phil Starr]

[quote name='Bill Fitzmaurice' timestamp='1405944887' post='2506737']
That filter compensates for the difference in response between an electric bass cab and a PA with subs. 80Hz is a bit high, 60Hz would be better. When you go to a concert with big PA and bass that's all boom and rumble with no definition, or for that matter even pitch, it's because the soundman has no clue what electric bass is supposed to sound like, nor how to use his PA kit to get it. By the same token one shouldn't go after an electric bass rig with flat response to 30Hz. If you get it you'll probably regret it.
[/quote]
[quote name='fleabag' timestamp='1405945301' post='2506748']
Even if you use 5 or 6 string bass ?
[/quote]
[quote name='funkle' timestamp='1405948354' post='2506798']
I experimented recently with using recording software and EQ through monitors and good headphones to cut out everything below certain frequencies, to see if my perception of bass was significantly altered by trimming low frequencies, and if so, at what point.


As others will have predicted or known already, cutting out everything with shelving EQ and a steep slope below 30Hz caused no difference to me in bass tone at all (less rumble and low freq crap though, e.g. from hitting fingers on strings). Below 40 Hz - bass still sounded good. Cut off at 50Hz - still sounded good to me. Somewhere around the upper 50s the B string got thinner if I put the shelving point there.

So, the question of 'how low do you need to go?' for me is upper 50's through headphones/monitors, and a bit higher using a HPF live, depending upon the room. You wouldn't even need to go that low for a 4 string.

It has helped me to consider further what I want out of a cabinet.

Iharmonic of low B, and I think the cab has a gentle roll off below that point. If you plug the ports on his cabs, the -3db moves a fair bit higher. He also does a lot of work with the crossover to get a smooth on and off axis response. Of course, using the 3012LF in the slightly smaller box size (than e.g. a Fearless F112), he sacrifices sensitivity, though if you have the watts I think you can get it back to some degree through the high Xmax. Still playing with it to figure out its capabilities.

It does all seem about the compromises. I'm still learning about all of them. Happy to take corrections if I have made any errors in the above
Pete
[/quote]

And I was worried about going off topic! I was really interested in Bill's comments as he has a lot of experience in this area. for any designer there are two questions. How low does it go and what does it do when you get there? One of the big unknowns is who is going to use the cab and how are they going to use it. In general I prefer to have a reasonably flat response with a bit of deep bass and then control it with eq. and I'd like to leave the decisions to the user, The reality if you look at the graphic on my amp is that I dial in the response you'd get from a load of cheap 10's rammed into an undersized box so I'd probably play and sound the same if i bought a cheap 4x10.

We looked at the response down to 30Hz in our design just to see what it would do under worse case conditions as far as excursion is concerned, we'd like to avoid people with 5 strings popping cones. We knew straight away that this speaker would give a lot more output between 40-90Hz in a bigger box but this would make it an impractical design for carrying. We still haven't decided whether to go for a 40hz tuning or a 50hz tuning and will have to do some listening tests to see what works best. the lower tuning promises better control of excursion at extreme conditions but we're not sure it will add anything to the sound, for the reasons you are giving.

Anything from the speaker with a wavelength close to the room dimensions usually creates problems in a gig. In addition we hear very little of those frequencies because of the way our ears work http://en.wikipedia.org/wiki/Equal-loudness_contour .We can easily lose 20dB between 100Hz and 40Hz.

the other observation is that using the prototypes in a gig I've already had problems with extreme bass off these cabs, you really do need some roll off.

finally speaker design is the art of the possible. No one wants to cart a half tonne cab around and speaker manufacturers aren't going to offer a range of speakers which nobody is going to use so most of the speakers we model have very similar frequency responses in the end.

[funkle]

Hah, yes, sorry about the lengthy post I made. I hope it was relevant though - mainly in regards the choices you have to make as a designer (How low? How efficient? How big a box?) and the trade-offs which are inherent to those choices.

Bill, Alex, Dave Green, Andy Lewis, Roger Baer, Duke LeJeune, etc already have worked out their own compromises with the newer drivers - it seems like to buy a cab you haven't been able to hear first you have to work out what the compromises are and what the designer intended.

I have a question. Does high Xmax (with high power handling, thermal and mechanical) + sufficient power compensate for low efficiency of a woofer? I'm thinking of e.g. the 3012LF vs the 3012HO here...

[LukeFRC]

[quote name='Phil Starr' timestamp='1405951839' post='2506847']
And I was worried about going off topic!
[/quote] sorry! Though I do find the discussion interesting - it's good to understand the hows and whys of how things work.
Also makes it easier to understand bass gear and the cab you're designing in relation to other gear (PA world mainly where they publish data) and other bass cabs.

[Phil Starr]

[quote name='funkle' timestamp='1405963650' post='2507016']
Hah, yes, sorry about the lengthy post I made. I hope it was relevant though - mainly in regards the choices you have to make as a designer (How low? How efficient? How big a box?) and the trade-offs which are inherent to those choices.

Bill, Alex, Dave Green, Andy Lewis, Roger Baer, Duke LeJeune, etc already have worked out their own compromises with the newer drivers - it seems like to buy a cab you haven't been able to hear first you have to work out what the compromises are and what the designer intended.

I have a question. Does high Xmax (with high power handling, thermal and mechanical) + sufficient power compensate for low efficiency of a woofer? I'm thinking of e.g. the 3012LF vs the 3012HO here...
[/quote]

That's not how I would go about choosing between these two. they are designed for entirely different uses. The HO has pretty impressive Xmax anyway and a frequwncy response at the top end that makes it usable on its own as a bass driver. The LF really has to be used with another driver and the associated crossover, and I'd crossover below 1kHz probably because it has a nasty resonance peak at about 1.8k.

Then i'd be modelling the LF response in my target size of cab, as we've just been discussing anything below 50Hz could just be an embarrassment of riches in a real room, but it would depend upon how it was going to be used.

WinISD or any of the other modelling software is going to tell you about what excursion you will get at what power and what the maximum output is so all these would come into it before I made a final choice. For instance we decided that we wanted something that gave us 120dB over most of the pass band and would handle 300W down to 50Hz staying within Xlim down to 40Hz. If the speaker does all those they were good enough irrespective of price and efficiency and we could look at other things like their price and top end response. The Beyma we chose wasn't in the end significantly different from the 3012HO to make it worth spending the extra, both fitted our criteria. If we were in the States where the Beyma is an expensive import and the Eminence cheaper we might have said the lightweight of the HO was worth having.

[Bill Fitzmaurice]

[quote name='funkle' timestamp='1405963650' post='2507016']. Does high Xmax (with high power handling, thermal and mechanical) + sufficient power compensate for low efficiency of a woofer? I'm thinking of e.g. the 3012LF vs the 3012HO here...
[/quote]You should not choose between those two based on that criteria. Use the LF if you either don't desire much midrange or if you have a separate midrange driver, and you need the lower frequency response that the LF is capable of in a cab of sufficient size.

Edited July 21, 2014 by Bill Fitzmaurice

[funkle]

Thanks Bill and Phil. Interesting to know the 3012HO mainly lost out on cost/accessibility. Again, the Beyma seems like good value, and you have been very specific in your criteria.

I wrote a whole spiel, then realised from the Eminence charts the HO is lighter in the lows than the LF, and that they look to be designed for different jobs.

Again, I'll ask though - in general - if you have a woofer which suits the job in hand, and enough power to drive it with, and it can take the power thermally and mechanically, but it isn't efficient, can applying extra power provide the extra volume to match another woofer with lower Xmax but higher efficiency?

I shall call this the 'Acme' question, given they are inefficent but have high Xmax (though Xdamage isn't apparently much higher than that...)

[LukeFRC]

funkle - I'm not sure what you're asking- can you make up for speaker inefficiency with higher Xmax and more power? ..... you used ACME for years - surely you'll have an idea more than most!

[Phil Starr]

Again I'd kind of come at it from a different angle partly because you are really asking about the design of the drivers. For a given magnet size you can make the speaker go deeper by giving it a heavier cone. You can make it louder by making it lighter or by giving it a short voice coil which sits neatly inside the magnet gap. If you want a high sound level and lots of bass you need a long coil so that some part of the coil stays inside the magnet all the time. This is inefficient because at any one time only part of the coil is doing any useful work.

40 years ago amps were expensive and mainly low powered, you got round this by using very efficient speakers and sacrificing Xmax and deep bass. If you wanted to increase the volume you used more speakers, hence the 8x10, or a big complex cab.

Cheap amps make it sensible to use less efficient speakers with long excursions making up for fewer speakers, however there is a limit. The speaker coil is still fairly fragile with thin copper wire and it doesn't cool well trapped inside the magnet so there is always an upper limit to the power a speaker can handle 450W for the 3" coil of the kappalite and 300W ish for a 2"coil. So yes, you can trade efficiency for 'better bass' with more power being the cost but only within limits.

[funkle]

Luke, the Acmes were the first proper cabs I started to pay attention to. I had a Trace Elliot 15" combo before that and later on a Flite 4x10", then the Acmes, which I didn't understand well enough when I bought them. The Acmes I owned for 5 years and didn't do much comparing. So until fairly recently (last year or two) I didn't feel I had a huge amount of understanding/comparisons to judge by. Still learning.

IMO the Acmes could be pushed hard with power. I didn't feel pushing them harder made them hugely louder once you started applying bigger power. The B2 was definitely beaten in volume by e.g. the Vanderkley 112MNT, but was waaay deeper.

I don't know Xmax of Acme 10" driver or 112MNT 12" driver. Assuming the former was higher than the latter, IMO higher Xmax did not make up for inefficiency. But that would not be the only difference to consider between those cabs. And whilst we are on the subject it's difficult to compare Xmax between speaker manufacturers anyway as they seem to use different yardsticks. So, I'm trying to figure out if my experience is more generalisable or not.