12" Cab Diary Continued

[fftc]

Thanks guys. Mk1 sounds closer to my skill level.

I've said this before, but it's worth repeating. I think it's fantastic that you are all sharing your knowledge and experience on here, and as someone who is now a bit less clueless than I was before I read these threads I appreciate that.

Thanks for clarifying on the driver Steve. I mistakenly picked up somewhere that Mk2 had different driver.

[Chienmortbb]

[quote name='fftc' timestamp='1488568184' post='3250187']
Thanks guys. Mk1 sounds closer to my skill level.

I've said this before, but it's worth repeating. I think it's fantastic that you are all sharing your knowledge and experience on here, and as someone who is now a bit less clueless than I was before I read these threads I appreciate that.

Thanks for clarifying on the driver Steve. I mistakenly picked up somewhere that Mk2 had different driver.
[/quote]One of the reasons Phil chose the SM212 for the MK1, was its extend mid/upper range. Compared to most other drivers it is very good. However dispersion is similar to every 12" driver. The advantage of the Beyma SM212 over most 12" drivers is that the extended upper range gives more flexibility. It can be used as a single driver "system" (MK1) or as th[size=4]e woofer in a two or three way system that is both more "[/size][size=4]Hi-Fi" and has wider dispersion [/size][size=4]than[/size][size=4] most commercial and [/size][size=4]even[/size][size=4] boutique cabs. [/size]

[size=4]​I may be entering uncharted or even [/size]blameworthy[size=4] territory here but there are few 12" drivers [/size]better[size=4] suited to Bass Guitar than [/size]the[size=4] SM212 in a well designed cabinet. It would take too long to explain why, [/size]but[size=4] for example [/size]it has a better high end than the Kappalite 3012LF and a better low end and displacement than the Kappalite 3012HO. So why is it not used more often by manufacturers? Most boutique makers are in the USA, and Beyma are not well represented there. If you manufacture in the far east, Eminence have an OEM factory that provides drivers for silly money.

We all have to eat and the low hanging fruit is very attractive.

Edited March 3, 2017 by Chienmortbb

[Gottastopbuyinggear]

Having read Stevie's comments I took a look at the Faital Pro PR300 specs and tried some models with it in WinISD. I'm pretty green at this stuff so I could well be interpreting things incorrectly, but it looks to me like you can get a similar response to the Beyma in the Mk 1 cabinet from the Faital in a smaller cabinet (about 46L) tuned about 5 Hz higher. If so then this would mean the weight of the cab would be reduced a bit, and the weight of the horn offset by the lighter weight of the neo woofer.

The reason I've been looking at this is the possibility of a pretty lightweight single cab solution, and the Faital driver comes in 4 ohm as well as 8. From looking at things in WinISD I estimate I'm probably getting a maximum of about 5dB more from running two of the mark 1 cabs compared to just a single, and at similar overall power I'd get about 2.5 to 3dB more out of a single 4ohm Faital loaded cab compared to a single Mk1 cab. In the real world, that may or may not be noticeable, of course.

Apologies if this is going off at a slight tangent - I don't want to derail the thread but I find these threads are great for learning and firing the enthusiasm for trying stuff out. I've just been through 6V6's 1x12 build diary, and the What 12" driver thread that preceded it, and there's a huge amount of information there. Ive also revisited Beer of the bass's 1x12 build diary, so coupled with this thread I now want a Basschat Mk2, a lightweight 4 ohm cab with a similar frequency response, and a Beta 12a loaded cab to see if I like the character of that driver, as many seem to.

[stevie]

A system with the Faital Pro PR300 and P-Audio PHT-407N (both neo drivers) would reduce the weight of the cab noticably. I've not worked with the Faital Pro driver, but I would expect it to sound a bit more refined than the Beyma in the upper mids. However, it won't go as loud as the Beyma because its excursion is not as great. That's could be why a lot of people use two Bergantino CN112s.

The internal volume of this cab is approx. 50 litres. So reducing it to 46 is not going to reduce the weight much. As long as you maintain the baffle dimensions, you can reduce the depth if you want a smaller, lighter cab. The port would have to be recalculated, of course, and I wouldn't recommend going under 40 litres.

A 4-ohm PR300 is a special order - so it's not really a goer for that reason alone. If there's enough interest in a lightweight system with this combination of (8-ohm) drivers, I don't mind designing the crossover as long as somebody lends me the drivers.

You can fit a Beta 12a or virtually any other "full-range" bass guitar speaker to this cabinet without any problem. They will all work. What you can't do is use the tweeter without first redesigning the crossover.

[Gottastopbuyinggear]

[quote name='stevie' timestamp='1488720793' post='3251242']
I don't mind designing the crossover as long as somebody lends me the drivers.
[/quote]

If we were talking about both drivers being 8 ohm then would the crossover need to be any different from the one you've already designed? I could understand it being different for a 4 ohm woofer.

[Chienmortbb]

I have just arrived home after visiting Stevie and hearing the cabinet with the with the Celestion compression driver. This time I also took my TC Electronic BC212 for comparison. The BC212 uses two Eminence 12 drivers together with a good Eminence compression driver. The Basschat 1X12 MK2+ uses a good Celestion Compression Driver and P-Audio Horn in place of the P-Audio Tweeter that Stevie has already described.

I won't bore you with tecnicalities but suffice too say that the BC MK2 with custom crossover and the Celestion HF unit/P-Audio Horn walked all over the TC BC212 in every way. It was louder, it had more lows, it had real mids, it was smooth. Whether you were playing bass guitar or bass and piano the sound was chalk and cheese. In comparison the BC was harsh. Stevie and I both have test disks that have some basic bass guitar record without any processing and that is what we used to listen to the cabinets. That way we take the variables out of the equation. No variations in technique, no differences in equipment.

Initially we tried the TC Electronic BC212 before I heard the new design. We both agreed it sounded OK. Then we played the same content through the MK2 BC 1x12. I had heard the Mk 2 before with the P-Audio tweeter and it was great but this time we had a reference. It may not have been a boutique bass cab but at a retail price of £400 new, the BC212 was a fair comparison.

I should say that the original MK1 design was a good one. If you are looking for 1x12 without a tweeter, you probably won't find a good one that costs less that 3 times the price. When Phil chose the BM212 from Beyma he found a winner. Is it perfect? No it is heavy compared to some of the neodymium 12s out there but its all round performance is hard to match. Excursion close to the Eminence 3012LF but half the price and with more useable mids/highs. The original design goal Phil set was to produce a cabinet that could produce 120dB SPL and have a reasonable top end ,so as to compete with Animal (Animal is the codename for a heavy drummer). The MK1 did just that.

Without losing any of that, the Mk2 design, whether using the P-Audio Tweeter or the Celestion Compression Driver, retains all that and adds the dispersion at mid-high frequencies that a 12" driver cannot do alone. It should also be said that a good crossover was the secret ingredient (I would say great but Stevie would blush). Add that and you have a small cabinet that is hard to beat even with a commercial 2x12. The secret is the dispersion. I am 6ft+ and even standing next to the cabinet, almost on top of it, I can hear myself. Many stacks are purchased purely so that the musician can here themselves on stage. Others are purchased because the single cab cannot "shift enough air. I suspect we will not have either problem with this cabinet.

When I first met Stevie he demonstrated a (modified) Roland cab with a 1x12 tweeter that was properly crossed over and had added bracing/damping. We compared it to the MK1 and while we both agreed the MK1 had a better low frequency response, the extra that came from the Roland shocked me. It was what persuaded me to have a two way design. Today we compared that same Roland Cab with the BC 1x12 and it sounded flat by comparison. I have to thank Stevie, despite the fact that he has cost me money on what was supposed to be a budget cabinet build. I don't think I could buy a single cab solution, as well engineered, as this for the money I can afford to pay. That is a slight fib as I was going to build two, until I was convinced that one would do the job.

I will effuse no more but I am going to build my cab in time for the South West Bass Bash on April 2nd, so anyone going is invited to try it and comment. I will also be playing through it at the Beer Festival in Bournemouth on the 16th April.

Edited March 5, 2017 by Chienmortbb

[Chienmortbb]

[quote name='Gottastopbuyinggear' timestamp='1488737304' post='3251419']
If we were talking about both drivers being 8 ohm then would the crossover need to be any different from the one you've already designed? I could understand it being different for a 4 ohm woofer.
[/quote]A quality crossover will include components that take into account the performance and specifications of the woofer as well as the mid range/high frequency units. This is the part that most manufacturers skip. You can see from Stevie's drawing in post 47(reposted below) the specific components that are used for the Beyma SM212 with the P-Audio Tweeter. A different woofer will require different components. The crossover using the Celestion Compression Horn is more complicated.

Edited March 5, 2017 by Chienmortbb

[Gottastopbuyinggear]

Aha. I was never very good at analogue electronics when I did my degree the best part of 30 years ago, I've forgotten almost all of what I did understand in the intervening period, and I'm probably not going to dust off my copy of Horrowitz and Hill now...

However, a short answer to satisfy my curiosity on this would be really good - I can see something that looks like a 2nd order crossover there, but there's obviously some other stuff going on. A quick Google suggests that's impedance stabilisation on the tweeter? Presumably it's things like that which many manufacturers are skipping? What's with the other resistors - just attenuation?

[stevie]

It is actually a Linkwitz-Riley 4th order crossover, although you can't tell from the circuit. The components roll the drivers off at the crossover point, adjust the phase of each driver and also change their frequency response outside the crossover area. The zobel on the tweeter that you noticed is there to modify the tweeter's frequency response rather than its impedance, although it does both. The resistors in this circuit have a dual function: attenuation and either damping of peaks or modifying the slope of the frequency curve.

It might look simple, but it isn't.

Oh, and Chienmortbb is quite right: if you change one or more of the drivers you need a new crossover.

[Edit: something Phil just brought up reminds me that the 24dB L/R is just on the LF section of the crossover. The HF is 18dB Butterworth. If you want to know more about this stuff, The Loudspeaker Cookbook is a good place to start.]

Edited March 7, 2017 by stevie

[stevie]

[quote name='Gottastopbuyinggear' timestamp='1488808346' post='3251910']
Presumably it's things like that which many manufacturers are skipping? What's with the other resistors - just attenuation?
[/quote]

From those commercial speakers that I've seen, there are virtually no manufacturers fitting a proper crossover at all - with one or two notable exceptions, I must add. The usual practice, as with the TC Electronics cab we looked at yesterday, is just to fit a simple filter to roll the tweeter off so that it doesn't blow up. I'm convinced this is why so many players don't believe in tweeters and switch them off most of the time.

There's no doubt in my mind that a properly implemented HF unit makes a huge difference to the definition of the bass both for the player and the audience, even if - like me - you play a P Bass with flats.

[stevie]

[quote name='Beer of the Bass' timestamp='1488541755' post='3249793']
That's a pleasingly clear set of drawings, and it looks like you should be able to get a pair of them out of a standard sized sheet of ply too. Is there a typo in the side panel size though? It looks like it says 510mm while the baffle and back are 540mm, or is it a combination of the image resolution and me not having my glasses on?
[/quote]

I've double checked and the side panels should be 540mm. Well spotted!

[Gottastopbuyinggear]

Well as it happens, Stevie, I do play a P bass with flats!

Before I set off on my Mk1 builds last year I started a thread about considering a 2x10 build. It wasn't long before I was convinced that the best thing to do would be to go with the original Basschat 1x12 design, which was just emerging at that time. I have a suspicion that I'll soon end up abandoning my recent thoughts of a lightweight neo based build and just go with the Mk2 design this time around.

I was going to stop asking questions, though another one popped into my head almost as soon as I posted, to which I think I already have the answer. Presumably combining a Mk2 and a Mk1 cab isn't going to present any problems with a 4th order crossover as there's effectively no phase difference, but there would be phase issues with a 1st, 2nd or 3rd order crossover? I wonder whether commercial manufacturers who offer both tweeter and non-tweeter versions of cabs address this, as you do hear of people pairing a non-tweeter and tweetered cab quite frequently.

[stevie]

The crossover type doesn't really matter. I'd treat the MkII cab as a standalone solution, as it should be loud enough for just about any semi-pro gig and it is flat response when placed on the floor. If you put another one underneath it, it will be bass heavy. Plus, unless you use a crossover on the bottom one, you will get destructive interference at higher frequencies because there will be phase problems due to the distance between the bass/mid drivers.

I'm not sure that commercial manufacturers really think about this. Most of them just want to shift boxes, which is fair enough. All of the small bass cabs I have heard have been very "middy" and bass light. However, adding a second one gives you 3dB of lift where the two drivers are 1/4 or less wavelengths apart, i.e. at the bass end. This makes the overall sound "fatter" and is, I suspect, why some people say that two cabs are better than one (and also why a lot of cabs sound better with the mids pulled back on the amp). The manufacturers are happy with this situation because they get to sell two cabs.

If you really need a 212 box, it should be designed as a 212, IMO. Think of it like this. You have an expensive pair of monitors in your recording studio, a pair of ATCs, let's say - a three-way design, carefully engineered and built to be one of the world's most accurate monitors. Do you think that adding another box containing a second bass driver is a good idea? And if by some strange magic you were to improve the sound of that ATC simply by doing this, what would that tell you about the ATC monitor?

I wasn't going to post anything controversial on this thread, as I didn't want to distract too much from the DIY content. But you did ask!

[Gottastopbuyinggear]

[quote name='stevie' timestamp='1488877310' post='3252491']
I wasn't going to post anything controversial on this thread, as I didn't want to distract too much from the DIY content. But you did ask!
[/quote]

Nothing controversial there at all, I think. I'm pretty sure that a single Mk II will be more than enough for my needs, and I fully understand the reasons why the commercial box shifters design and build to particular price points, etc.

I don't want to distract any more, either - I'm eager to see the design details for the Celestion driver version, and how you get on with the Poplar ply build, so I'd better let you get on with it!

But thanks again to you guys for taking the time to post these threads - they're entertaining in themselves, and it's hugely satisfying when you take the knowledge and actually build something from them.

As for the theory, there comes a point when you have to accept that there's

[stevie]

Well it's nice to see at least a flicker of interest in the higher end version . I wasn't going to bother, but I'll post the details and the measurements and crossover circuit diagram later in the week. We still have a few details to clarify about the tweeter version.

[LukeFRC]

[quote name='stevie' timestamp='1488893478' post='3252696']
Well it's nice to see at least a flicker of interest in the higher end version . I wasn't going to bother, but I'll post the details and the measurements and crossover circuit diagram later in the week. We still have a few details to clarify about the tweeter version.
[/quote] Im interested but "where's the other version gone eh? Hurry up guys" come over as a wee bit rude!

[stevie]

Well thanks for that, Luke.

[6v6]

I'm interested and planning to build one of these, crossover details would be great as I've not had time to try modelling it (was planning to have a play in LTspice but an overview would be most helpful, my EE skills are rusty!).

FWIW I think the question about combining Mk1 and Mk2 cabs was a good one, and I appreciate the clarification as I was wondering the same thing.

[Chienmortbb]

As Im said earlier it wa my plan to build two cabinets but Stevie convinced me that one would be enough. The Beyma SM 212 has a massive excursions of 8.3mm as I remember, only beaten by the Eminence Kappalite 3012LF. However on the Kappalite, the "LF" is the clue, it really is just a woofer and would probably need a more sophisticated crossover and/or a mid range driver and maybe a tweeter as used by Greenboy in his FEARfull and FEARless models. See [url="https://scontent-lht6-1.xx.fbcdn.net/v/t1.0-0/q89/p480x480/10906135_1021323607896101_2539545370011067118_n.jpg?oh=8b07b3a72c11ec2bf6773bf25a063e1a&oe=59707441"]HERE[/url] [size=4]Then the cabinet would be bigger, heavier and a lot more expensive. [/size]
=

Edited March 7, 2017 by Chienmortbb

[stevie]

The Beyma goes lower than most. Here's a simulated comparison of the Beyma in our 50 litre cab with the Kappalite in a larger (60-litre) cab tuned lower (45Hz). The Eminence has the edge at 40Hz, but the Beyma is a couple of dBs louder above 100Hz. There's not a great deal in it really. The excursion of the two drivers is comparable. The Eminence scores on power handling, as it has a 3" coil and it is also 1kg lighter. On the other hand, it costs more than twice as much and needs a midrange driver.

Blue = Beyma Orange = Eminence

Edited March 7, 2017 by stevie

[Passinwind]

[quote name='Chienmortbb' timestamp='1488904253' post='3252805']
As Im said earlier it wa my plan to build two cabinets but Stevie convinced me that one would be enough. The Beyma SM 212 has a massive excursions of 8.3mm as I remember, only beaten by the Eminence Kappalite 3012LF. However on the Kappalite, the "LF" is the clue, it really is just a woofer and would probably need a more sophisticated crossover and/or a mid range driver and maybe a tweeter as used by Greenboy in his FEARfull and FEARless models. See [url="https://scontent-lht6-1.xx.fbcdn.net/v/t1.0-0/q89/p480x480/10906135_1021323607896101_2539545370011067118_n.jpg?oh=8b07b3a72c11ec2bf6773bf25a063e1a&oe=59707441"]HERE[/url] [size=4]Then the cabinet would be bigger, heavier and a lot more expensive. [/size]
[/quote]

There are some pretty nice sounding commercial cabs using the 3012LF (edited from 3015LF) that weigh around 25 pounds and are not too large, but yeah, not all that inexpensive at $650 in the US before shipping.

Edited March 8, 2017 by Passinwind

[Chienmortbb]

[quote name='Passinwind' timestamp='1488917770' post='3252962']
There are some pretty nice sounding commercial cabs using the 3015LF that weigh around 25 pounds and are not too large, but yeah, not all that inexpensive at $650 in the US before shipping.
[/quote]We normally assume an exchange rate of £1=$1 especially when it applies to US made products imported to the UK so £650 actually equates to just short of $800. Do those cabs with 15s have mid range and HF drivers too Charlie?

[Passinwind]

[quote name='Chienmortbb' timestamp='1488929050' post='3253087']
We normally assume an exchange rate of £1=$1 especially when it applies to US made products imported to the UK so £650 actually equates to just short of $800. Do those cabs with 15s have mid range and HF drivers too Charlie?
[/quote]

Oops, meant the 3012LF. The one I'm thinking of has a single 3" mid driver for the 12" loaded one. We can get finally get dozens of Beyma drivers quite easily over here these days, but not the one you guys are using. It probably wouldn't be too hard to special order through the primary US dealer though, but I doubt it'd be any cheaper than the 3012LF.

[Phil Starr]

[quote name='Passinwind' timestamp='1488940368' post='3253126']
Oops, meant the 3012LF. The one I'm thinking of has a single 3" mid driver for the 12" loaded one. We can get finally get dozens of Beyma drivers quite easily over here these days, but not the one you guys are using. It probably wouldn't be too hard to special order through the primary US dealer though, but I doubt it'd be any cheaper than the 3012LF.
[/quote]
It might be worth checking the price of the SM212 but if I was based in the US I'd probably have looked at a different driver myself, if there is no cost benefit then there are other drivers to use. I believe Eminence are cheaper over there too, which would further tip me towards choosing one of their offerings. It's the balance of cost to performance that makes the Beyma such an obvious choice here and it was always crying out to be part of a two way design. In fact I originally chose it for my PA speaker, but you gotta try it with your bass haven't you?

[Chienmortbb]

[quote name='Passinwind' timestamp='1488940368' post='3253126']
Oops, meant the 3012LF. The one I'm thinking of has a single 3" mid driver for the 12" loaded one. We can get finally get dozens of Beyma drivers quite easily over here these days, but not the one you guys are using. It probably wouldn't be too hard to special order through the primary US dealer though, but I doubt it'd be any cheaper than the 3012LF.
[/quote]I think this is the real point. The 3012LF would have been the speaker of choice it were 40/50% cheaper over here it would be a good basis for a 1x 12 plus midrange design. It would not work as well as the Beyma in a single 12 configuration like the BC Mk1.

Edited March 10, 2017 by Chienmortbb