Beymer SM212 issues

[JohnDaBass]

Has anyone experienced any quality or performance issues with these drivers?
I have blown one driver and I was wondering if anyone else has had similar issues.
Thanks for you feedback.
John DaBass

[Phil Starr]

That's bad luck, I've had no problems and they look to be nicely made. how were you using them? what cab, what amp any eq/fx?

[JohnDaBass]

Hi Phil
Gear details
cab in my DIY Mark 1
internal 245x425x540 external 566x440x300
vol 56.23lts
shelf port 540x35x230
Amp
Fender Rumble 500 head
settings
gain 7 o clock (minimum)
Bass 3 o clock
Low Mid 12 o clock - flat
High Mid 12 o clock - flat
Treble 12 o clock - flat
Master 9 o clock
No effects or pedals.
Guitar
Fender active PJ
Volume max
pan P pup solo
T M B all set middle position - flat
I hope this helps with throwing some light on the root cause of the speaker failiure.
The speaker is not dead (Voice coil open circuit) just very distorted with loud random 'clicking' noise from open A downwards.
I have no problems with my DIY mark 2 cab (the one you suggested adding the fourth port) now that it has four ports 66mm dia and 180mm long.
Brs John

[Phil Starr]

I can't see any reason why you would have blown this speaker, the cab is a good match to the speaker and excursion is pretty much OK down to nearly 40Hz even at the 350W your amp gives into 8ohms. You are using a little bass boost but that shouldn't have given you this problem with the amp you are using. Strictly speaking it would have been better to use a filter like the thumpinator to control subsonics but IMO there could well have been a manufacturing fault. If it is still inside the guarantee period I'd contact the seller and see what they offer.

[JohnDaBass]

Hi Phil,
Thank YOU for your analysis.The cab and speaker really sounded great but sadly the speaker is 6 weeks outside the 12 month warranty period. I plan just to buy another SM212 from Bluearan.
Thank you again for your continued help and support to all of us on Basschat!
I am sure that there are many on here who, like me go straight to any new posts from an Ol'Sage like you.
Thanks
John

[Phil Starr]

It might be worth asking about a re-cone. I'm pretty sure Beyma do kits for all their speakers and Blue Aran do have people who can do the job, it may be too expensive to make it worthwhile but you lose nothing by asking for a quote.

I wouldn't go to any posts of mine if I veer off the topic of speakers though

[stevie]

John, I think you'll find your cabinet is tuned too high. My calculations say you've tuned to around 60Hz. With that tuning, you'll be exceeding xmax at 40Hz with an input of 200 watts. As you have also applied bass boost, this figure could easily drop to 100 watts or less.

Tuning to our recommended 50 Hz will give you an extra 3dB at 40Hz, perhaps making bass boost unnecessary. The speaker will then also handle an input of 350 watts without exceeding xmax (at least in theory).

You might like to check the tuning frequency using the rice grain test. Use your good driver obviously. This works on the principle that driver movement is greatly reduced at the cabinet tuning frequency, because that's where the port is doing most of the work. Turn your speaker on its back and sprinkle a few grains of rice in the centre of the cone. Then go to this site (or something similar): <http://onlinetonegenerator.com/subwoofer.html>, play the frequencies and you will see the rice dancing up and down along with the movement of the cone. As you approach the tuning frequency, movement will slow down. The point at which the rice moves least is your tuning frequency, and this will be shown on your display.

Then get back to us.

PS Try this with your good cab with the round ports first. You should get a tuning frequency of 54Hz.

Edited September 29, 2016 by stevie

[JohnDaBass]

Hi Stevie,
Thank you for your contribution.
I will try the rice test on both Mk1 & Mk2 cabs with the same good speaker and post the results.
So am I correct in my understanding that because the port tuning frequency was too high I actually drove the speaker voice coil beyond it's allowable travel limit (Xmax). So damaging the speakers performance. I have to say that I was unware of the dangers of such a mismatch of port tuning and Xmax. I always thought that when the speaker got to its limit it would complain a bit and that would be the time to reduce the juice. It just goes to show how much us novices can learn from guys like you and Phil.
Thanks for your valuable help and experience.
John

[stevie]

I'd say it's likely you drove the speaker past its limits, but you'd need a post mortem of the driver itself to know for sure. If you have it reconed (a good idea!), the reconer will be able to tell you. The port provides valuable support for the speaker around the tuning frequency. To tune a bass guitar cab for maximum power handling your tuning frequency should be around 50 Hz. There are times when you might want to tune lower, but I wouldn't ever tune higher.

I've lost count of the number of times people on this site have said you can always hear a speaker complaining. I've never bought into that one. Anyway, you're welcome and please let us know what you find.

[Chienmortbb]

[quote name='stevie' timestamp='1475165972' post='3143683']
I'd say it's likely you drove the speaker past its limits, but you'd need a post mortem of the driver itself to know for sure. If you have it reconed (a good idea!), the reconer will be able to tell you. The port provides valuable support for the speaker around the tuning frequency. To tune a bass guitar cab for maximum power handling your tuning frequency should be around 50 Hz. There are times when you might want to tune lower, but I wouldn't ever tune higher.

I've lost count of the number of times people on this site have said you can always hear a speaker complaining. I've never bought into that one. Anyway, you're welcome and please let us know what you find.
[/quote]The problem is that the speaker complains when the voice coil bottoms. That is when the damage is done and there is no way back from there.

Stevie is right that a well designed/tuned cabinet will protect the speaker from most abuse. Remember though that like all speakers, Power Compression is your enemy.

Edited September 30, 2016 by Chienmortbb

[Phil Starr]

[quote name='stevie' timestamp='1475153984' post='3143501']
John, I think you'll find your cabinet is tuned too high. My calculations say you've tuned to around 60Hz. With that tuning, you'll be exceeding xmax at 40Hz with an input of 200 watts. As you have also applied bass boost, this figure could easily drop to 100 watts or less.


[/quote]

Hi Stevie, I got the same tuning frequency as you but wasn't too alarmed at excursion using WinISD. To assess damage potential I use Xlim rather than Xmax (for anyone else this is the physical limit of excursion rather than Xmax which is where the speaker starts to distort excessively) Beyma quote 27mm peak to peak for this or Xlim=13.5mm and I didn't think the speaker should be damaged at frequencies above 40Hz. It was close enough though that I didn't think bass boost was a good idea. What do you think?

For anyone reading this I'll try and explain, conventional bass controls often offer +/- 12 dB boost and cut at a stated frequency, say 100Hz. by turning the dial to 3 o'clock you might be boosting the level at 100Hz by 3dB (doubling the power at this level) but at the frequency goes down you boost the bass by increasing amounts. At 50Hz you might be demanding 6db of boost, 4x the power and even more maybe 12db of boost down at subsonic frequencies. So, even though you are only hearing a slight increase in 'bassiness' you might be asking your speaker to work four times as hard with frequencies you don't really want anyway.

Add in a ported cab, great down to the tuned frequencies but below the tuned frequency the ports just become holes and the speaker is effectively operating without a cab leaving the cone to move without a spring or shock absorber to limit its movement.

There is a solution though, use an electronic filter to stop any subsonics getting through to the amp. Something like a Thumpinator.



I'm with Stevie on relying on the idea that hearing a speaker 'farting out' is a safety measure. Playing music at high volumes means you really aren't likely to hear something that you might otherwise pick up on a test bench with a signal generator.

[stevie]

I wouldn't rely on Xlim too much, Phil. There is a myth going around that Xlim is the maximum excursion a driver can take before it gets damaged, but that's plain wrong. Xlim is a short-term physical limit that relates more to the suspension, cone and coil former rather than to the voice coil. When you go past xmax, power compression starts to kick in with a vengeance and you put power into the coil that has nowhere to go. The magnetic gap provides an important path for cooling the voice coil. Push the coil too far out of the gap, and it doesn't get cooled properly.

The voice coil can reach its thermal limit well before it reaches Xlim, as I'm sure many on this forum will testify. My guess is that this is what has happened here, but like anything else, it's impossible to be sure at a distance. If overheating is the cause, the voice coil will be discoloured.

Here's a useful diagram showing xmax and xlim: [url="http://www.subwoofer-builder.com/xmax.htm"]http://www.subwoofer...er.com/xmax.htm[/url]

Edited September 30, 2016 by stevie

[Phil Starr]

I wonder if anyone has any statistical data on the failure modes of high power loudspeakers. I've certainly seen lots of burnt out coils in the dim and distant past and also speakers where the coil former has clearly made contact with the back of the magnet structure but few damaged mid/bass drivers recently apart from some older Eminence drivers where the aluminium coils have separated from the leadout wires I haven't had a speaker failure for a long time.

[stevie]

It seems to be a common problem with DJs. Otherwise, I agree: it's not as common as it used to be.

[JohnDaBass]

Hi All,
I have checked the tuning frequency of both Mk1 & Mk2 cabs using the online tone generator and grains of rice.
I have also rechecked all the as built internal dimensions and actual port aperture sizes.

John DaBass DIY Mark 1 cab [attachment=229022:JDB_Mk1.jpg]
cab is 12mm ply with an 18mm baffle set back 35mm from port mouth.
Internal 235 x 545 x 430
Volume = 55Ltrs
Port 33 x 475 x 230 ( port area is 156 sq Cm or equivalent to a 140mm diameter round port)
Measured tuning frequency = 51Hz
The simple www.linearteam.dk calculator estimates that the tuning frequency should be around 50Hz
This is the cab that the Beymer SM212 may have been damaged.

John DaBass DIY Mark 2 cab[attachment=229023:JDB_Mk2.jpg]
cab is 18mm ply
Internal 245 x 494 x 445
Volume = 53.86 Ltrs
Ports four ports 66mm Diameter 180mm long
Measured tuning frequency = 61Hz
The simple www.linearteam.dk calculator estimates that the tuning frequency should be around 58Hz
If I increase the port length to 230mm the tuning frequency should be close to 52Hz
There has been no issues with the Beymer SM212 in this cab.

I apologise to everyone as perhaps I should have started this post in the Build Diaries thread.

[stevie]

Fascinating!

John, I just re-entered the numbers in your last post into my software and get 57Hz for the slot port, which is still quite a bit off. My software is actually deducting volume for the port and the driver, which should make it more accurate, but there's obviously something wrong that I can't quite figure out yet.

I did the same with cab no. 2 and get 55Hz compared with your measured 61Hz. That's also rather disappointing. Bassbox Pro is usually spot-on with round ports, as we found when we meaured Phil's prototypes. When I have a bit more time, I'll have a fiddle with WINisd, although I believe Phil uses WINisd and he got the same figures as I did in our earlier calculations.

I really like your side-ported version, by the way, as it leaves space for an optional tweeter or midrange driver. Phil originally built a slot ported cab, but with the ports at the end of the box. We discarded that because of a nasty standing wave that was not present in the box with round ports. We assumed at the time that this was because the slot port had made the internal dimensions square .

This thread would indeed make a useful addition to the Cab Diary. Maybe one of the mods could pick it up and stick it on the end.

[Edit] I would just add that your measurements demolish my theory that cab mis-tuning was the cause of your damaged driver.

Edited October 1, 2016 by stevie

[Phil Starr]

Actually the published tuning in the design diary weren't the port dimensions calculated by WinISD they are the ones we tested at Stevie's which were tuned fairly accurately in practice but not quite as calculated. (I confess I'd been fiddling with them and hadn't put them back to where they were supposed to be )

I've got the plots up in front of me and a higher tuning actually reduces excursion, but only by a tiny amount. Without knowing the exact way they were being used I still think bad luck with a slightly out of spec unit might be part of the problem. We'll probably never know unless you choose to get it re-coned and ask Blue Aran or whoever does it to tell you what they think when they take it apart.

I think once you calculate the volume displaced by the speaker and the port volumes you are going to find both cabs quite close to 50l.

[stevie]

I've re-checked one cabinet that I have here with a slot port, and my software is 100% accurate compared with the impedance measurement. I also recalculated the Cab Diary speaker and it's only 2Hz away from what we actually measured. Just for information, really, as what matters is the actual measurements on the cabinet.

[Chienmortbb]

Stevie's point about power compression may be close to the mark. Beyma are or were the only major manufacturer to publish power compression curves and from memory even at 100W many of their drivers have 3dB compression, going up to almost 6dB at rated power. If you try to turn up to compensate and/or the driver is slightly out of spec....

Of course power compression happens with continuous power.

[Guest bassman7755]

[quote name='JohnDaBass' timestamp='1475162763' post='3143630']
Hi Stevie,
Thank you for your contribution.
I will try the rice test on both Mk1 & Mk2 cabs with the same good speaker and post the results.
So am I correct in my understanding that because the port tuning frequency was too high I actually drove the speaker voice coil beyond it's allowable travel limit (Xmax). So damaging the speakers performance. I have to say that I was unware of the dangers of such a mismatch of port tuning and Xmax. I always thought that when the speaker got to its limit it would complain a bit and that would be the time to reduce the juice. It just goes to show how much us novices can learn from guys like you and Phil.
Thanks for your valuable help and experience.
John
[/quote]

You can also look out for subsonics, and I mean literally "look" since your eyes begin to resolve discrete in and out movement of the cone (as opposed to it just become a little blurred) at somewhere around 25 hz. If you can see the cone moving then thats means you pumping energy into the speaker that wont resolve as sound and is doing nothing other than making your speaker and amp work hard and potentially damaging the speaker.

[Guest bassman7755]

[quote name='Phil Starr' timestamp='1475222752' post='3144067']
For anyone reading this I'll try and explain, conventional bass controls often offer +/- 12 dB boost and cut at a stated frequency, say 100Hz. by turning the dial to 3 o'clock you might be boosting the level at 100Hz by 3dB (doubling the power at this level) but at the frequency goes down you boost the bass by increasing amounts. At 50Hz you might be demanding 6db of boost, 4x the power and even more maybe 12db of boost down at subsonic frequencies. So, even though you are only hearing a slight increase in 'bassiness' you might be asking your speaker to work four times as hard with frequencies you don't really want anyway.

Add in a ported cab, great down to the tuned frequencies but below the tuned frequency the ports just become holes and the speaker is effectively operating without a cab leaving the cone to move without a spring or shock absorber to limit its movement.

There is a solution though, use an electronic filter to stop any subsonics getting through to the amp. Something like a Thumpinator.
[/quote]

+1 definitely very important to use bass boost in conjunction with some sort of HPF, some bass amp do have HPFs built in but I wish this was a more openly published spec like it is for PA amps.

[JohnDaBass]

Here's the response from Bluearan following my email to request a returns authorisation for them to retest the defective Beymer SM212.

[color="#000000"]Hello Mr Evans,

I am sorry to hear that the speaker has developed a fault. If the cabinet is tuned to 51Hz and the bass is played at low E, which would be 41.2Hz, then the speaker will be running below the tuning frequency of the box, meaning that the driver becomes effectively unloaded. When this happens the driver can over-excurt and hit the back stop of the driver which would account for the cracking sound of the driver.
You can return the driver for inspection at the following address, but if the driver has over-excurted then this would not be covered by the warranty.[/color]

[color="#000000"]I am not sure whether i[/color]t's worth the cost of shipping the unit back for retest only to find that Bluearan conclude that it is not a manufacturing defect and so will not be replaced.
Probably best just to buy new?

[Phil Starr]

Hi John, I'm not sure excurted is a word

Anyway I'd message them back to ask if they could re-cone the speaker back to original and what that might cost. If it is cheaper than a new speaker then it would be worth doing as all the important bits will be new with just the magnet and frame saved from the original, and you'll get some sort of guarantee. Finding out what had gone wrong would be a bonus too.

You could conceivably argue that you did not exceed the excursion limits and use the WinISD plots as evidence but it would be hard to prove either way what happened in terms of how much 41Hz fundamental reached your speaker.

[JohnDaBass]

Here is the response from Blue Aran

From: Blue Aran
Hello Mr Evans,

Our technical department has tested the speaker and has not been able to locate any issue with the speaker. Looking at the original fault report, you have stated that you are using the speaker in a cabinet tuned to 51Hz and playing low E on a bass guitar on it. This would put the cabinet into an unloaded state which may result in the cone over excurting and the voice coil former hitting the back plate of the driver. This would account for the load cracking noise when this note is played. This would not be covered by warranty as it would count as using the speaker outside of the design parameters. The only way to confirm if the voice coil former had hit the back plate would be to remove the cone which is a destructive test.

Regards
Michael Tootill
I replied


Dear Michael,
Thank you for your email.
1. I note with interest that your Technical department, having tested the speaker, was unable to find the fault mode as the device passed the test regime. It therefore follows that when the speaker was initially dispatched to me the fault mode must have been present since your Technical department tested, and passed, the speaker prior to shipment. Clearly this suggests that there was some manufacturing defect present which was not manifest and caught during the Blue Aran test at Goods inward receiving and again at the test when the unit was dispatched to me. I therefore propose that the speaker unit be returned to Beymer for their Quality Control department to analyse the root cause of the manufacturing fault mode. I am sure you would agree with me that if defects are not able to be detected with the current Blue Aran Test system the Test system should be reviewed and improved to trap defects from leaving Blue Aran. Similarly the supply chain Test strategy should be capable of blocking defects from entering each successive step in the chain.
2. When the parameters of the SM212 and the cabinet design details are modelled in WiniSD the tuned frequency of 51Hz the results do not concur with your earlier assertion that the speaker would be operating outside its specified Xmax range (27mm peak to peak). At 41Hz ( low E) only 25% of the fundamental frequency is presented to the speaker.
3. As a remedy may I propose that you return the speaker unit to Beymer under the Trading Terms and Conditions between Blue Aran and Beymer, for them to analyse the fault mode and provide advice on improving your Test strategy to trap such defects leaking through in the future. This would protect Blue Aran from accepting defective speakers from vendors and improve your customer confidence level in your products. In the meantime I propose that you replace the SM212 and reimburse the shipping costs I have incurred to date.
Regards
John Evans 

Yesterday I recieved this email stating that the Beymer SMS 212 is NOT suitable for bass guitar!!

Thank you for your email regarding the Beyma SM212, please accept my apologies for the slightly delayed response this is due to us being particularly busy this time of year and there has simply been insufficient time to deal with the level of enquiries we have recently received.

With regard to your points.

All products leaving the Beyma factory are subject to strict QC controls, and they work to ISO9001 specification. It is extremely rare for any defective product to leave the Beyma factory, I believe in 8 years of selling Beyma, we have only ever once encountered a product which had a very minor manufacturing defect which was quickly identified and remedied.

The issues to which you are referring are not due to a manufacturing defect.

I believe that some of this has been mentioned previously, but I will try to explain it more clearly.

Firstly, this product has never been advertised as, nor have we recommended it for us in applications for Bass Guitars. This is primarily a PA/Studio speaker designed to be used as part of a 2 or 3 way speaker system.

Your box is tuned to approx 50 Hz, but you are trying to reproduce sounds lower than this in frequency. It would be normal to have a high pass filter just below tuning frequency, (say 45-48Hz) to reduce any sound below these frequencies. If you want to get lower frequencies, your box needs to be tuned to say 40-44Hz. The purpose of a reflex enclosure is to extend the bass response lower than you would get in a sealed enclosure, but you generally do not want to try to reproduce frequencies below the tuning frequency, UNLESS they are very carefully controlled and managed, with a suitable compressor/limiter in place to manage the levels.

Below tuning frequency of the box, you get a problem known as unloading, in brief, it means you can drive the speaker too hard with much less power than you think.

Copied from https://en.wikipedia.org/wiki/Bass_reflex



...at frequencies below 'tuning', the port unloads the cone and allows it to move much as if the speaker were not in an enclosure at all. This means the speaker can be driven past safe mechanical limits at frequencies below the tuning frequency with much less power than in an equivalently sized sealed enclosure. For this reason, high-powered systems using a bass reflex design are often protected by a filter that removes signals below a certain frequency


With regard to WinISD, it is important to be aware that this is modelling/simulation software intended as a design tool to help with cabinet design. To finalise any design you need to take real world measurements, and have a good understanding of all the relevant physics. You cant force the speaker and cabinet to behave the way you want it to just because WinISD says so. The results from WinISD may not necessarily be 100% accurate, especially when it comes to using a speaker in an unloaded state which it is not designed to do.

Ive had a very quick look at this on WinISD, and I can see the cone excursion increases massively below 50 Hz, and at 42Hz you are well into the realms of an uncontrolled cone.

The Xmax of this drive unit is 8.25mm, that is the maximum linear excursion in one direction (forwards or backward) before the cone begins to behave in a non-linear fashion.

Xdamage is 27mm peak to peak, that it a maximum of 13.5mm in one direction before the voice coil could become damaged due to over excursion.

Given that at 42 Hz you are effectively using the driver as if it's not in a cabinet, allowing uncontrolled excursion, and you do not appear to have anything in place such as a high pass filter or limiter to prevent excess power at these frequencies, it would be very easy to reach 13.5mm – particularly with the dynamics of a live musical instrument where peak power can easily be four times the average power, and peak excursion increasing accordingly.

Your description of the 'cracking' sound is in keeping with the voice coil former hitting the back plate of the driver, and it is likely now that some damage has occurred to the voice coil former. The only way we can confirm whether damage has occurred would be to cut the cone and voice coil out for inspection. Since this is still a working unit, this is a bad idea, as it would turn it into a non-working unit.

To summarise, this is not really the correct speaker for your application, and the combination of incorrectly tuned cabinet for this driver means that excessive excursion can and will occur on low bass notes.

The only way to remedy your problem is to ensure you have a correctly tuned cabinet, with a suitably selected driver for your application, and appropriate limiters and high pass filters in place to correctly control the speaker

So no help then!

[Phil Starr]

Hi John, I need to get off and do some work so I'll revisit this later, there's a lot of information here. It looks like your SM212 is still working, so that is good. If that is the case then Blue Aran are right, it isn't worth cutting it open. I'd thought it had stopped working.

All the guff about winISD is disappointing. I've seen the same nonsense when Skidder blew his Eminence 3015 Kappalite a few years back. Win ISD just uses Small's equations to describe the cone movements, they can't seriously be arguing that the science is all wrong.

The stuff about not being suitable for bass but for PA is also nonsense. What do they think goes through a PA? Clearly they are denying the possibility of using a bass through PA or the existence of bass in recorded music!

They are also wrong about the SM212, it is a general purpose driver, Beyma also make the SM112 which is the dedicated PA bass driver. In their English language material they do not talk much about applications and neither critically do Blue Aran. In any case the physics don't lie.

They do have a case however about using a bass without a HPF. It's something we have mentioned and true of most commercial units too, in fact it's an issue with all ported cabs and not much discussed. At 40Hz and 300W your cab will not exceed 13.5 mm excursion. At 30Hz and 300/w it will, the speaker isn't indestructible. In any case you shouldn't use the speaker beyond xmax for extended periods and the 13.5mm figure really is an absolute limit. The 25% figure comes from TKS I think and is a good rule of thumb, it doesn't mean you personally use your bass in exactly that way.

I'm concerned about Blue Aran's attitude, which may be down to one over zealous employee of course. I think they are trying to browbeat you, and not engaging helpfully, and this is the second time I have seen this. You may well have been using the speaker outside of the parameters of safe operation, we may never know exactly. They may have good grounds for saying that it isn't their responsibility but some of their assertions are untrue and their tone is certainly aggressive and unhelpful.

Last time they came on here and did engage a little. It would be useful to know if they are a company with the highest standards we can recommend. I need to go back and look at all of your details.

I feel a little responsible for this and if necessary I might need to tweak the design or add some more advice to stop it happening to anyone else.

Edited December 5, 2016 by Phil Starr