12" Cab Diary Continued

[Chienmortbb]

Well another trip over to Casterbridge (Dorchester) Stevie and I (well Stevie really) compared my cab, fitted with the Beyma SM212, Celestion Compression attached to a P Audio horn with the Prototype MK2 cabinet fitted with an Eminence Kappalite 3012LF and a Celestion 6" mid range driver.

Firstly we put some recorded bass guitar through both cabinets. We were both surprised how different they sounded. Initially the impression was that the Kappalite went a bit lower and the SM212 went a bit higher. However you cannot trust your ears. When we measured the response, the low end was very similar. At the lower end around 50Hz there was very little in it but the 3012LF had a tad more low end but not much. However the mids showed a dip in the response of the 3012LF of around 2dB from 150Hz . So our ears interpreted the lack of mids as more prominent bass.

For bass guitar both were excellent, although with music through them the SM212 plus Celestion Comp driver was superb. It's measured response would shame most hifi speakers being fairly flat from about 55Hz to 20KHz. Of course the Kappalite is well over 1Kg lighter than the Beyma so all things being equal the cabinet will also be lighter. It will also handle more power than the Beyma although how much louder it can go is debatable. I was persuaded to build the Mk2 after hearing a full range 12" cabinet of Stevie's that had a Deltalite (I think) in it. Whilst the Deltalite cab did not go as low as either of those tested today, it proved, along with the BC 1x12 MK1 that a single 12 can make a great bass cabinet.

Stevie was going to build a 3 way speaker and he told me he did prototype it before building the 12/6 but as the placement of the drivers was determined by the dimensions of the baffle, it was far from ideal and sounded no better or maybe worse than two way the 12" plus horn I built. I should add the caveat that today's lesson is that you cannot design a cab on paper and you can only compare cabs when A/B ing them.

One of the best things about this whole process is that I have learnt a lot about speaker design. Having the measuring gear at Stevie's meant we could check our ideas and those of others and prove, or disprove, theories and ideas. The basic idea of a low cost relatively light weight cabinet has been achieved even if the cost was higher than I imagined. The cost? About £250-£300 for the materials for mine.

The weight? 15.3Kg (34lbs).

The next test is Saturday when it will have a 250W amp driving it at a gig.

Edited May 11, 2017 by Chienmortbb

[stevie]

Just to expand on that report a bit, the two cabs we compared were identical apart from a slight difference in the tuning. Below 100Hz both drivers measured exactly the same. The Kappalite remained flat from 100Hz up, however, while the Beyma kept rising to about 200Hz where it flattened off at a level a few dBs higher than the Eminence. So although the Beyma and the Eminence extended equally low in the bass, it sounded like the Kappalite went lower and was fatter because the upper bass wasn't as prominent. That certainly wasn't obvious just listening to them.

The other thing we noticed, which we didn't have time to pursue, was that the Kappalite system actually sounded a bit louder than the Beyma system on bass guitar, even though the measurements showed that it wasn't. I suspect that could be connected with the off-axis performance of the 6" midrange driver.

[Phil Starr]

Great work guys, I really wish I could have been there.

Subjective loudness is such a tricky thing, I think we tend to pick out the loudest sounds and they dominate our perception of loudness, so anything with a flat response is going to sound quieter even if it measures the same. One persons loud is another persons 'shouty'. IME if you use the same piece of recorded music through speakers and something in the recording sets off even a small resonance in an A to B test then that cab will sound louder. Change the recording and the difference disappears. That's where your measurements add so much.



At some time I'd love to bring across the Mk1 to compare and I've also got a 2 way design built with the Beyma and a P-Audio BM-D440 compression driver. As soon as I get time I want to have a try at something using the 4x3" line source Faital drivers.

[RichardH]

[quote name='stevie' timestamp='1488720793' post='3251242']
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.

......

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.
[/quote]

Been having a good old read through this thread. Out of interest I overlaid the published frequency responses of the Beyma and Faital drivers over each other. A lot of similarities, though the Faital seems to have a bit more further up the frequency range.


...and here is the 407 vs the 407N




Not sure how much interest there is out there for the lightweight option of the neo drivers mentioned above, as there's no point in people putting the time into crossover design if there's no takers, but it's certainly tickled my interest....

At the risk of derailing the thread, I'm currently using a Genz Neox 212T, and find it a bit of a big old beast to lug around sometimes - hence the interest in a 2 cab solution. I know what has been said earlier in the thread about not stacking a pair of these 1x12s, but I wonder if as a second cab one where to use a non tweeter version upside down (so the 12" drivers are in close proximity) might work better than "just" plonking them on top of each other.

Edited May 21, 2017 by RichardH

[Gottastopbuyinggear]

I modelled the Faital driver in that box after modelling the 4 ohm version but it came out looking pretty bad. It could be my lack of knowledge, though, so I'd be interested to see the results if someone with a little more expertise tried modelling it - it's possible I made a mess of entering the parameters into WinISD.

[Phil Starr]

[quote name='RichardH' timestamp='1495359826' post='3303170']
Been having a good old read through this thread. Out of interest I overlaid the published frequency responses of the Beyma and Faital drivers over each other. A lot of similarities, though the Faital seems to have a bit more further up the frequency range.


...and here is the 407 vs the 407N




Not sure how much interest there is out there for the lightweight option of the neo drivers mentioned above, as there's no point in people putting the time into crossover design if there's no takers, but it's certainly tickled my interest....

At the risk of derailing the thread, I'm currently using a Genz Neox 212T, and find it a bit of a big old beast to lug around sometimes - hence the interest in a 2 cab solution. I know what has been said earlier in the thread about not stacking a pair of these 1x12s, but I wonder if as a second cab one where to use a non tweeter version upside down (so the 12" drivers are in close proximity) might work better than "just" plonking them on top of each other.
[/quote]

That's an interesting bit of work Richard, thanks for sharing it. The tonal balance will clearly be different for the two speakers. One persons 'a bit more high up' is another persons 'a bit less low down'. If you were using a single driver then I personally prefer a bit of emphasis in the 1-2kHz area, but the design brief was to have a flat response which is why I went for the Beyma. There's anything up to a 6dB difference in sensitivity between the two drivers so you'd absolutely hear the difference.

I've a personal little interest/belief and that is that the smaller lumps and dips in response have the potential to affect the voicing quite dramatically. There are two points on your graph I'd pick out, at 680Hz the Beyma dips and the Faital peaks. If you play a note which excites that frequency then one speaker is going to emphasise the note and the other is going to very slightly de-emphasise it. In other words the speaker itself is going to add to the voicing of any bass run around that point. Over time you may even get to anticipate it in your playing. The other point is at 2kHz where the position is reversed and the Beyma peaks, there are loads of others too.

Having two horns widely spaced is going to do things to the dispersion of a speaker with some 'interesting' comb filter effects. I have however in the past used a couple of PA cabs with the Beyma and some P-Audio Horns as my bass speakers and they did sound very good, both for me and the audience. More recently at the SW Bass Bash we tried the Mk2 tweetered speaker on top of the MK1 and it did sound very impressive, although the listening conditions weren't ideal. If I wanted to design a modular 2x12 I think that's the path I'd go down. You'd have plenty of power handling/output low down and a single horn raised up dealing with the top end with the possibility of using either cab on it's own.

As to using the Faital neo units, well that becomes a different design. The Beyma is fairly light and the Basschat Mk1 is an easy one hand lift. The design spec for that cab was for something cheap and simple to build that would compete with mid range commercial units. Saving an extra 3kg or whatever it works out at would be a worthwhile exercise but Stevie and I are amateurs so we have to think about which projects we are going to pay for next. If you decide to go ahead with a lightweight design I'll happily contribute ideas and I'm pretty sure everyone else will contribute too.

[Phil Starr]

[quote name='Gottastopbuyinggear' timestamp='1495402768' post='3303538']
I modelled the Faital driver in that box after modelling the 4 ohm version but it came out looking pretty bad. It could be my lack of knowledge, though, so I'd be interested to see the results if someone with a little more expertise tried modelling it - it's possible I made a mess of entering the parameters into WinISD.
[/quote]

If I get time this evening I'll have a look. Still struggling with a Whitesnake bass line though.

[RichardH]

[quote name='Phil Starr' timestamp='1495437641' post='3303615']
Having two horns widely spaced is going to do things to the dispersion of a speaker with some 'interesting' comb filter effects. I have however in the past used a couple of PA cabs with the Beyma and some P-Audio Horns as my bass speakers and they did sound very good, both for me and the audience. More recently at the SW Bass Bash we tried the Mk2 tweetered speaker on top of the MK1 and it did sound very impressive, although the listening conditions weren't ideal. If I wanted to design a modular 2x12 I think that's the path I'd go down. You'd have plenty of power handling/output low down and a single horn raised up dealing with the top end with the possibility of using either cab on it's own.
[/quote]
That's kind of why I was thinking that the bottom cab could be used upside down - so the two 12" drivers were in closer proximity. Good idea re the mk1 + mk2 combo.

[quote name='Phil Starr' timestamp='1495437641' post='3303615']
As to using the Faital neo units, well that becomes a different design. The Beyma is fairly light and the Basschat Mk1 is an easy one hand lift. The design spec for that cab was for something cheap and simple to build that would compete with mid range commercial units. Saving an extra 3kg or whatever it works out at would be a worthwhile exercise but Stevie and I are amateurs so we have to think about which projects we are going to pay for next. If you decide to go ahead with a lightweight design I'll happily contribute ideas and I'm pretty sure everyone else will contribute too.
[/quote]
Yes, you're right, it does move away from the intial brief - don't want to distract the thread. It was the comment earlier on that the cab as specified would take other drivers, including the Faital that got me wondering. I am tempted to try the lightweight route using a cab of this sort of dimensions, as WinISD seems to show it looking happy enough in that volume. It's the crossover that I have no experience of working with.

[quote name='Phil Starr' timestamp='1495437761' post='3303617']
If I get time this evening I'll have a look. Still struggling with a Whitesnake bass line though.
[/quote]
Tricksy little things, aren't they....

[Chienmortbb]

I looked at the 407N as it is a lot lighter but the response at the low end is not as good as the 407 ferrite it would have needed a crossover frequency above 2KHz.

[RichardH]

Yes, that shows in those graphs doesn't it..... but it looks like the the PR300 has more above 2K than the Beyma - though it drops off at 2K and below at the 45 degree angle, so there might end up being a dip if the xover was above 2K.

[geoffbyrne]

Hope not to derail.....

I have a Beyma 212 - but am totally hopeless with tools. Anyone building these cabs for money?

G.

[Phil Starr]

[quote name='geoffbyrne' timestamp='1495907223' post='3307512']
Hope not to derail.....

I have a Beyma 212 - but am totally hopeless with tools. Anyone building these cabs for money?

G.
[/quote]

It isn't too difficult to build these if you get the panels cut to size for you. If you can use a screwdriver the Mk1 pretty much assembles itself. B&Q will usually cut the panels and a smaller timber merchant will usually help. Some might even offer to cut the holes in the baffle for you.

[Thunderpaws]

[quote name='stevie' timestamp='1486548855' post='3232603']
Yes, one big port, Luke. The idea is to minimise friction and turbulence within the port; the less friction, the less chuffing and compression. It's not so critical with large cabs, or general purpose PA cabs for voice, but with small, high powered bass cabs like this one, optimising the porting makes a *huge* difference to the output produced by the port - and reduces distortion audibly. A single round port is simply the best solution for minimising friction.

They're called flared ports, MoonBass. I have a selection of them here, including some very nice Precision Ports 4" ones. Unfortunately, availability is a bit of a problem in the UK, but they do work really well. I considered using the Precisions, but their external diameter is about 18cm and there wasn't enough room on the baffle. Also, a single flared 4" port wasn't going to be long enough to tune the cab to the target frequency. The performance of the 5" we are using is equivalent to a flared 4" port. The ideal would be a 5" flared port on the back of the cab, but nobody makes one.

If somebody could use a 3D printer to make some flared port ends cheaply, that would make me very happy. It seems like an ideal job for a 3D printer.
[/quote]

[Thunderpaws]

I'm a teacher with access to a 3 D printer. Send me some sketches with dimensions and I'll see what it produces.

[geoffbyrne]

[quote name='Phil Starr' timestamp='1495957347' post='3307702']
It isn't too difficult to build these if you get the panels cut to size for you. If you can use a screwdriver the Mk1 pretty much assembles itself. B&Q will usually cut the panels and a smaller timber merchant will usually help. Some might even offer to cut the holes in the baffle for you.
[/quote]

....or, could someone suggest a complimentary port to cut in an Ashdown Mibass 12" cab so the Beyma works properly? I think the porting is the problem, the cab isn't 'breating' smoothly at low frequencies.

G.

Edited May 31, 2017 by geoffbyrne

[Chienmortbb]

[quote name='geoffbyrne' timestamp='1495907223' post='3307512']
Hope not to derail.....

I have a Beyma 212 - but am totally hopeless with tools. Anyone building these cabs for money?

G.
[/quote]As Phil says it is not difficult and if you look at the first post there are very detailed plans. I have now built 2. The size is such that you get two cabs from a 1220 x 2440 sheet of ply. If you only build one cab it will be expensive. The poplar ply we used was 15 mm and the cost approx £50 per cabinet or £100 for two.




I am planning to build a combo version so if [size=4]we can get two other people interested, I will buy some ply and dry fit the cabinets, cut the holes and then send them out to you for easy assembly. That means just [/size]glueing [size=4] [/size]and[size=4] screwing the [/size]cabinets[size=4] together[/size]

[Chienmortbb]

[quote name='geoffbyrne' timestamp='1496148395' post='3309115'] ....or, could someone suggest a comlimentary port to cut in an Ashdown Mibass 12" cab so the Beyma works properly? I think the porting is the problem, the cab isn't 'breating' smoothly at low frequencies. G. [/quote]Geoff is it this one?

[geoffbyrne]

[quote name='Chienmortbb' timestamp='1496150533' post='3309139']
Geoff is it this one?


[/quote]Yup!

[Phil Starr]

Hi Geoff, I had a quick look at the Ashdown and I don't see why it wouldn't sound at least OK with the Beyma. It looks to be a similar sized cab to ours and I'm guessing tuned within the ranges we tried.

If you could measure the depth of the port I could look at it properly for you.

What exactly do you mean by "it isn't breathing smoothly at low frequencies"?

[geoffbyrne]

If I pluck a low B and let it ring, I hear it 'fluttering'. The original driver was farting out badly at any decent volume (EQ flat) so I thought I'd try a Beyma in it. Big improvement but, as I said, there's still this 'flutter' that to my uneducated ear sounds like the air pushing & pulling through the ports. (Chuffing?) I was wondering if an exta round port at the back would improve matters? What measurements do you need, Phil?

G.

[geoffbyrne]

[quote name='Chienmortbb' timestamp='1496150269' post='3309137']
As Phil says it is not difficult and if you look at the first post there are very detailed plans. I have now built 2. The size is such that you get two cabs from a 1220 x 2440 sheet of ply. If you only build one cab it will be expensive. The poplar ply we used was 15 mm and the cost approx £50 per cabinet or £100 for two.




I am planning to build a combo version so if [size=4]we can get two other people interested, I will buy some ply and dry fit the cabinets, cut the holes and then send them out to you for easy assembly. That means just [/size]glueing and[size=4] screwing the [/size]cabinets[size=4] together[/size]
[/quote]

If therer isn't an easy answer to the Ashdown, then I'd be interested in this.

G.

[Phil Starr]

[quote name='geoffbyrne' timestamp='1496255984' post='3310022']
If I pluck a low B and let it ring, I hear it 'fluttering'. The original driver was farting out badly at any decent volume (EQ flat) so I thought I'd try a Beyma in it. Big improvement but, as I said, there's still this 'flutter' that to my uneducated ear sounds like the air pushing & pulling through the ports. (Chuffing?) I was wondering if an exta round port at the back would improve matters? What measurements do you need, Phil?

G.
[/quote]

I want to calculate the tuning frequency of the cab, I have the dimensions of the cab from Ashdown's ads but I need to know how long the port is.

It could be chuffing or it could be something loose in the cab. It's very hard to be certain without hearing the cab. It might be worth a quick look to check if any stuffing in the cab is loose or there is anything moving around near the port, like the cabinet covering. It's an outside chance but worth a check. The Beyma will probably shift more air than the original driver so chuffing is certainly a possibility.

You can't just add a port, that will completely change the tuning of the cab. You'd need to considerably modify the cab if you need a bigger port, possible but it might be easier to build a new cab, and cheaper if you sell on the Ashdown which will lose most of it's value if no longer original.

Low B at full power is always going to be a challenge for a single 12" speaker but let me have the depth of the port and i'll have a think.

[geoffbyrne]

OK I'll try to measure it up this afternoon. It's an 'L' shaped port - it goes all the way back and turns up about 3cm in the vertical, but I'll take the speaker out & measure it.

G.

[Phil Starr]

I can do a rough calculation based on that but I need the exact width and height of the port as well as the length to get it right. Check for anything loose whist you are looking

[geoffbyrne]

[quote name='Phil Starr' timestamp='1496311369' post='3310376']
I can do a rough calculation based on that but I need the exact width and height of the port as well as the length to get it right. Check for anything loose whist you are looking
[/quote]

OK. Been in there & stapled down any loose edges on the wadding - there were one or two.

Measurements (Internal):

Front Horizontal Section:

Width : 363mm
Height : 45mm
Depth : 345mm

There are x2 10mm wide support bars running front to back.

Rear Vertical Section :

Width : 363mm
Height : 45mm
Depth : 190mm

There are x2 10mm wide support bars.

Total Depth = 535mm

G.

Edited June 2, 2017 by geoffbyrne