Beyma SM212

[Phil Starr]

As some of you will know we specified this speaker as the basis of the Basschat 1x12 cab and the Mk 2 version with a Celestion Tweeter. The SM212 has since been discontinued but I have contacted Beyma to see if they might make a short OEM run. They aren't interested but they do have 35 SM212's still in stock in Spain, they forwarded me to Blue Aran who have a shipment about to leave the Spanish factory in a couple of days. If anyone is interested it might be worth placing an order. Contact Blue Aran directly or let me know here and I will get back to them.

 

It's a lovely driver and ideal as the basis of a bass cab. Excursion or Xmax is exceptional at this price bracket meaning this speaker handles low frequencies exceptionally well. The designs for both cabs are available here on the BassChat website.

[FirstBass]

I can't understand why they discontinued this speaker

 

It's a beauty!

[Phil Starr]

It is, nicely made and the spec is spot on for a portable bass speaker. 

[FirstBass]

id be keen on one as a spare

[parker_knoll]

Beyma 12LX60V2 has similar curves but much higher power handling and is £60 more expensive. I haven't heard it so not sure of its character in the mids. 

 

http://www.bluearan.co.uk/index.php?id=BMA12LX60V28

[Phil Starr]

On 07/02/2022 at 01:01, parker_knoll said:

Beyma 12LX60V2 has similar curves but much higher power handling and is £60 more expensive. I haven't heard it so not sure of its character in the mids. 

 

http://www.bluearan.co.uk/index.php?id=BMA12LX60V28

It's always good to look but they are very different beasts. The giveaway is the power handling this one has a 4" voice coil and it's that bigger coil that increases the ability to dissipate heat. It has a much heavier cone which is also stiffer so it doesn't reproduce high frequencies. It is designed for bass frequencies only and for a very small cabinet. VAS is only 40l versus 150l for the SM212. Xmax is calculated differently for the two drivers and is actually almost the same, there are three methods commonly used for measuring Xmax and beyma has joined the rest of the manufacturers in moving from the least flattering to the most flattering measurement. 

 

It's a nice speaker but designed for deep bass only, Xdamage is huge. It'd make a compact sub for PA or possibly for duties in a multi-way PA speaker.

[parker_knoll]

Thanks for your wisdom, Phil. 

 

I have actually found a dealer in London who claims to have SM212s in stock but is a bit vague about pricing. I'll go and see him in a week or so. 

 

How about the Sovereign Pro 12-300 as something close?

[Phil Starr]

Are you going to use it as a single driver for bass guitar? 

 

It has a slightly bigger magnet and good efficiency. The frequency response has a slight lift at the top end which is likely to sound quite nice with bass, I'd expect it to sound a bit livelier than the SM212. On the downside the excursion isn't so great as the SM212. This speaker is middling rather than exceptional in that area. For a pub gig one of these would work pretty well but you might need a second for bigger gigs. At £65 the price at Blue Aran is good. The best replacement we've found is the Faital Pro 320. That's a lovely speaker and lightweight but it's a neo and much more expensive, but not much more than the other Beyma so maybe within your budget. You could also look at the Beyma 12CMV2 which i've actually tried in our cabs and sounds quite good too, it's just had a price hike though.

[Phil Starr]

Good news for anyone who wants to use the Beyma SM212, Blue Aran have just had a delivery of 33 speakers. I'm not sure if this is the last 33 in Europe all now in the UK or if BA have persuaded Beyma to make a small run of speakers. Either way if you are thinking of building one of our Mk1 or Mk2 designs I would consider securing the drivers now, they may not be available later. I'll put up some links later and get back here if I get more information from Blue Aran.

 

I've also been looking at a design for a small PA sub using this speaker, I can put that up if people are interested.

Edited February 11, 2022 by Phil Starr

[FirstBass]

A sub you say???? oh..... how very timely

 

Yes please!

 

Still my fave driver.... Can't believe theyre discontinuing them ☹️

 

 

 

[Balcro]

If price isn't the deciding factor, then I recall this from a US web-site.

(see here  -   https://audioxpress.com/news/New-Beyma-WR-Family-of-Low-Frequency-Drivers
WR for cast frames, WRS for pressed steel.

 

They're currently about £120 in the UK
The CMV2's are around £80.

 

It's taken 5+ years to phase out the SM series.
Perhaps Phil can cast his critical eye over the specs for a "compare & contrast" opinion.

[Phil Starr]

On 11/02/2022 at 16:41, Balcro said:

Perhaps Phil can cast his critical eye over the specs for a "compare & contrast" opinion.

Unable to resist a challenge.

I can see what Beyma have done but from a bass players point of view they haven't done us many favours. Essentially this is a completely new speaker and is a bit more 'specialist' than the all rounder the SM212 was. Basically they have fitted a bigger magnet and a larger diameter voice coil. The coil is shorter in the 'new' speaker and the magnet gap bigger and that has reduced Xmax but the power handling, which is rated thermally because the bigger diameter coil can radiate more heat. However the SM212 can shift more air 453cm rather than 334cm (wshat happened to the mathematical notation) which means more of the power is available. This is both speakers in a 50l cab with the SM212 in blue. You can see the extra 50W power handling on the flat lines but around the port frequencies the SM212 is clearly a 'winner'

 

 

You can how this affects the sound levels produced this is the maximum sound levels with 300W into both speakers.

 

 

By using a bigger magnet the magnetic forces are greater in the WR12  Qts is much lower and BL is higher. This creates new gains for the new design but also some losses. The new speaker will operate happily in a smaller cab. for a classically flat response it only needs to be in a 30l cab. the SM212 needs a 100l cab. I've chosen to model them in a 50l cab to make a 'fair' comparison. All this extra magnetic force will damp the movement of the cone. As the cone moves the coil in a magnetic field it induces a current in the coil opposite to the current coming from the amp. The stronger the movement and the stronger the field the more this happens so low Qts speakers tend to roll off the bass. Lots of other things come into play but you can see this in the frequency response. Again I've modelled this in the same 50litre cab for comparison. the last graph I promise  You can see that the SM212 in blue shows that the 50l cab is a bit small and the magenet a bit weaker so the bass is slightly underdamped and has a peak. For the new speaker the reverse is true and you get an over damped response and a slow roll off from 200Hz. The -3db point is 80 Hz and down to 50Hz the SM212 has more bass. This is reversed below 60hz and at 40hz you get 3db greater output from the new design. However that is at low power because of the higher maximum displacement shown in the second graph the actual maximum bass clearly favours the old SM212

 

 

So is the new speaker better?  I would say that at the price (big magnets aren't cheap) I'd have gone for a longer coil and a lower Qts, though that has all sorts of knock on implications for the rest of the design. The old SM212 hit a real sweet spot offering still outstanding excursion, power handling, efficiency and other positive features. The new speaker is better suited to a smaller box, both speakers have well controlled cone break up in the higher frequencies but for me Beyma have missed the mark slightly and there are other options. At the price of the SM212 in the UK it was a great speaker. 

 

 

 

 

[parker_knoll]

Thanks, Phil. I received my SM212 from Blue Aran yesterday. It's going in a 115l box along with a JBL E120 to handle highs and mids, so it's a 2x12, but the other 12" is in its own little 15l box-inside-a-box. I'm biamping so I'll try a few crossover points, but may install a passive crossover in time. 

 

I am also considering a 1x12 sub in the future so would love to see the plans. Also, in that context something that works in a <50l box will be ideal and it only needs to be good up to about 200Hz in my case. 

Edited February 16, 2022 by parker_knoll

[Phil Starr]

Ha ha I shouldn't mention ideas so easily, now I think I've accidentally committed to designing something to  get the best out of a 212 as a sub.

 

It's really tough to design a small sub and less than 50l is problematic. To get something with a small box to have a predictable response you need to compensate for the reduced air mass with a low Q/big magnet driver. That leads to problems with a shelving response as detailed above. You also have to look at the moving mass of the driver and compliance and the knock on effects of all of this affect Vas and so on. It's where  the SM212 hit a sweet spot of great all round driver.

 

I think a <50l sub is going to involve compromises. A high cut off point, gradual roll off or reduced efficiency, it might work better with a smaller drive unit for example if box size and portability is the crucial factor. At this point you are designing a system not just a sub.

 

The original 50l SM212 design was created by Basschatters asking for as much low bass output as possible from a truly portable speaker but which would cover the full range of a bass without a tweeter. As such it's most of the way to being a sub design. Maybe we could start another thread if you want a teeny tiny sub design, it might be an interesting challenge.

 

I'm using DSP now in developing designs, so much quicker and easier than building passive crossovers and as you say you can retro fit something passive if it becomes a go-to cab.

[Balcro]

On 16/02/2022 at 13:57, parker_knoll said:

Thanks, Phil. I received my SM212 from Blue Aran yesterday. It's going in a 115l box along with a JBL E120 to handle highs and mids, so it's a 2x12, but the other 12" is in its own little 15l box-inside-a-box. I'm biamping so I'll try a few crossover points, but may install a passive crossover in time. 

 

I am also considering a 1x12 sub in the future so would love to see the plans. Also, in that context something that works in a <50l box will be ideal and it only needs to be good up to about 200Hz in my case. 

 

Some interesting tables and notes here on the JBL E-120
https://jblpro.com/en/site_elements/jbl-professional-enclosure-guide

1.5cu.ft = 42 Litres.

 

* See the note at the bottom of page.2

*This is an old document hence the comments about adding more ducts, somewhat imprecise by today's standards.

* Don't use fibreglass!

 

OMG it's efficient!!
https://usspeaker.com/JBL e120-1.htm

Edited February 21, 2022 by Balcro

[FirstBass]

@Phil Starr - i cant wait to see it!

 

I've been checking daily 😅

[Phil Starr]

Looks like you might have to wait a bit, I've been trying to upload some stuff but it seems I've broken BassChat

 

Temporary limit on attachment upload sizes - Site News - Basschat

 

Edited February 22, 2022 by Phil Starr

[Phil Starr]

OK this has uploaded. These are the responses of the SM212 in three cabs. The blue is 30l, green is the 50l BassChat Mk1 design and the red is a maximally flat design of 110l. You can clearly see the smaller the cab the less bass, though the blue30l cab is actually louder than the others at 120Hz the loss of thee bottom octave 40-80Hz is obvious.

 

So now it is over to you to decide what you want. You can't really hear the frequencies below 50Hz very well and in small enclosed spaces they just make everything sound muddy by exciting room resonances. Most important to hearing bass well are the harmonics with 80-160Hz giving us the impression of bass which is why you think you can hear bass from a small radio speaker.

 

It is perfectly possible to use the 50l cab here as a sub in a deliberately limited system. With a slight tweak of the tuning it will go down to 50Hz(-3db) and give you a slight boost at 100hz. Output will be 122db max which equated to what most manufacturers are describing as 128db. Obviously you'll be missing about half an octave of deep bass but that's going to affect any keyboards or kick/floor tom more than bass guitar where you'll hardly notice it. In a small venue you'd probably want to filter those frequencies out anyway.

 

However the possibility is there to exploit a bit more of the SM212's potential by increasing the cab volume and getting a response between the 50 and 110l cab. Keeping the profile of the cab and increasing the depth by 20cm will give you a significant improvement in deep bass response.

 

[FirstBass]

i'm leaning towards 80L nett tuned to 45hz

 

Not huge to transport, but a decent response

 

I reckon one of these would be good for pub gigs

 

Now - how to calculate a shelf port... 

 

Thanks for the info Phil

[Phil Starr]

7 hours ago, GlamBass74 said:

i'm leaning towards 80L nett tuned to 45hz

 

Not huge to transport, but a decent response

 

I reckon one of these would be good for pub gigs

 

Now - how to calculate a shelf port... 

 

Thanks for the info Phil

Well done, I'd come to exactly the same conclusion 110l is just too big to be a mini-sub but 80l is still manageable size wise but gives you a potentially flat(-3db) response down to 50Hz which was my target.

 

If you're using winisd then you need to start looking at the tuning frequency, I found 40hz gives the flattest response with the slowest roll off but have a look at the power handling which improves a lot in the 50-100Hz range if you tune to 50hz. That's also reflected in the maximum output graphs. Tuning to 50Hz does mean there is a 1db hump and 45Hz looks a great compromise tuning on just the frequency response but excursion limited power means that response won't be available when running at high levels. That could bring on reliability problems but is much more likely to introduce distortion. 

 

On that basis I'd go for a 50Hz tuning, it's probably going to make little difference in practice as you rarely get to full power levels and the speaker still has a bit of safety margin beyond xmax. There is very little fundamental in bass guitar so it is only drums that will be likely to demand those high levels of output. Frankly I would always put a limiter/compression on drum mics anyway. I also don't think you'd notice the 1db hump in practice. This is an area where the designers choice comes in but have a look before you start making sawdust and see what you think.

 

The port calculations are simple in winisd, just change the shape of the port to square put the full width of the cab in as one of the dimensions and away you go. You need to look at 'rear port velocity'; that's just a winisd quirk, you can put the port anywhere but it is calculated as rear port. Try and get the port velocity at all frequencies  down to 50Hz below 17m/sec. Above this speed you'll get probable wind noise from the port. You need a larger port for a PA sub than a bass speaker as you are going to assume it will have to handle full bass output down to the design lowest frequency. As I've said you can get away with smaller ports for bass guitar which doesn't have a lot of fundamental. I found a 35cmx7cm port achieved this.

 

Lastly shape; it's worth making the cab quite squat. the cab is likely to be supporting the tops so a bigger footprint makes for a more stable base. it also allows for a longer port which you'll need to avoid wind noise. Getting the speaker close to the ground will also give you reinforcement up to higher frequencies. With an instrument speaker a taller cab is better as it can improve the amount of mids reaching your ears when you are close to the cab on-stage.

 

Good luck, you are pretty much there with the design. The bad news is that you now share my addiction to speakers

 

[FirstBass]

Hi

 

Thanks for the great reply

 

I've started doing some CAD work to see what's viable

 

I've always found with WinISD that the port calculations seem to come out longer than actually required after the infamous rice test (love the simplicity of that idea)

 

This is with both round port and shelf ports. I'm starting to think i'm doing something wrong. 

 

I will definitely look into the tuning aspect of the enclosure a bit more.

 

One of these bridged through an ancient (and heavy!) PV900 with the low cut engaged might be rather pleasant

 

Cheers!

 

 

 

 

 

 

 

 

[Phil Starr]

I've also found that. So if you are doing something wrong then it's more than just you  There are a number of reasons, the TS parameters can be hard to measure and there are manufacturing spreads but one of the problems is that there are other parameters of the speaker and cabinet that aren't accounted for in the calculations like QL the damping/quality factor due to leakage in the cab and inherent to the speaker. We have double checked most of the published BassChat designs and @stevie measured the TS parameters himself. Even so the WinISD port length is just a starting point for us. It's one reason we haven't gone for shelf ports where changing the length is more of a problem than just cutting a few different lengths of drainpipe.

[Phil Starr]

OK, I thought WinISD ought to have a way of programming QL and it does. 

 

Select 'Box' on the menu bottom left and click on 'advanced'. Default on mIne is set to QL=10. Vance Dickason in the Design Cookbook has Ql=7 as median with values of Ql=3 and 15 as low and high. I've always assumed Ql =7 would be the default. As I said I've never bothered to measure Ql and only regard WinISD  as a way of getting close and then something that will need tweaking.

[parker_knoll]

If you want a small sub speaker I can recommend the Lavoce SSF122 and its 10" equivalent SSF102. Work great in about 60l but they are inefficient of course.

 

ANOTHER QUESTION: are there any 10"s that approach the SM212 in performance?

[parker_knoll]

On 21/02/2022 at 16:25, Balcro said:

OMG it's efficient!!
https://usspeaker.com/JBL e120-1.htm

 

Yup. I'm using a Fostex attenuator to match it to the SM212. I'm hoping to assemble it all this weekend so I'll let you know how it sounds.