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12" Cab Diary Continued

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[quote name='Phil Starr' timestamp='1491296123' post='3271825']
!4 kg is good, my originals came out at around that without the horn and crossover, though my bracing internally was a bit agricultural (rushed for the last bass bash) and I used Baltic birch rather than poplar.
[/quote]

My Mk 1s in 18mm Poplar, with all panel to panel joins reinforced with 20mm square battens, are also about 14Kg, hence why I thought the Mk 2 in 15mm would possibly be lighter. I think I recall seeing an estimate earlier in this thread of up to 16Kg, but I may have made that up.

[quote name='Phil Starr' timestamp='1491296123' post='3271825']
Yes I'm looking at doing a 40litre version, possibly even smaller as I might do some prototyping with a bit of spare ply. Basically I find I always end up dialling in a hump at 100Hz and rolling off below 40 anyway, the response you'd get in an over small cab. That's fine with my Harke amp with a graphic but is proving harder with my Mark Bass amp. I'm wondering why I'm carrying extra wood to not quite get the sound I want.
[/quote]

Not the sound you want - now he tells us!

I'm still relatively inexperienced with all this (from a user point of view) so I'm quite keen to do a bit of experimentation to see how a different speaker would sound in the real world. I need to revisit the modelling to check but I did look at putting a Beta 12 in the Mk1 cab (partly to free up a Beyma for a Mk 2 build, and partly just for curiosity) which I think predicted a similar bump of 2 or 3dB around 110 Hz or so. Of course the Beta 12 does have a pretty big hump in the high mids, so overall I guess the sound would be substantially different.

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14Kg seems very good for the two-way cab. The cabs I built last year came out at 14Kg each, and that was with the lighter Beta 12s, no tweeter and 12mm birch ply.

[quote name='Gottastopbuyinggear' timestamp='1491309555' post='3272002']
I'm still relatively inexperienced with all this (from a user point of view) so I'm quite keen to do a bit of experimentation to see how a different speaker would sound in the real world. I need to revisit the modelling to check but I did look at putting a Beta 12 in the Mk1 cab (partly to free up a Beyma for a Mk 2 build, and partly just for curiosity) which I think predicted a similar bump of 2 or 3dB around 110 Hz or so. Of course the Beta 12 does have a pretty big hump in the high mids, so overall I guess the sound would be substantially different.
[/quote]

After using them for a while, I like what the voicing of the Beta 12 does for my bass guitar sound, though they are almost certainly less versatile than the cab developed in this thread. What they are very good at is getting an instantly pleasing tone and and a satisfying amount of volume from my 80-watt valve amp that has only bass and treble EQ (an application which may be a bit of a niche interest). If I take one out with the double bass where I'm aiming for a more natural tone I find that I'm fighting that upper mid response a bit, and I suspect the Beyma two-way design would fare a lot better there.

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[quote name='The Shrek' timestamp='1491233409' post='3271426']
Thanks Stevie. Guys I hope I am not being forward in asking this question. I would gladly pay upfront for the service if there are any of you basschat guys who would be prepared to build a proper crossover for my project. Just advise me on what speakers to buy to match the appropriate crossover build. I am in Northern Ireland so I will gladly pay for any excessive post and packing and any other costs.
[/quote]

Michael, I have so many projects on the go at the moment, I can't find the time to get to them. Designing the kind of crossover you're looking for means having the completed cabinet here and measuring it. Then designing the crossover in CAD, building it up to see if it works, and adjusting it so that it sounds right. Although some crossovers almost build themselves, it can often be a fairly time-consuming process, with three-ways being particularly demanding.

The cheap and cheerful way of integrating a 5" driver with a bass unit is just to stick a capacitor in front of it to roll it off at a relatively high frequency, say 1500Hz. I wouldn't be surprised if that's what Mark Bass have done with their latest three-way, although I'd be happy to be proved wrong. It will work, but I'm pretty sure you'd be better off with the two-way design described here.

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[quote name='Passinwind' timestamp='1491275795' post='3271728']
Personally, I really like the all dark look a lot, and never really liked plastic piping or trim of any kind except for corners, same as on basses for that matter.
[/quote]

You could well be right about this. It's difficult to judge from a photo.

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This a fairly flexible design. Builders have the choice of a two-way with an inexpensive tweeter, a two-way with a proper compression driver, or a one-way with the Beyma 12" speaker on its own.

However, the cabinet as it stands will work with any 12" driver specified for bass guitar - the Eminence bass 12s, including the Beta, all the current bass guitar speakers from Celestion, the Faital Pro 12PR300 and others that I've not even thought about. However, you can't expect the crossover and HF units to work with these other drivers.

Edited by stevie

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[quote name='stevie' timestamp='1491322428' post='3272117']
You could well be right about this. It's difficult to judge from a photo.
[/quote]

It is difficult to judge that way, for sure. But there's also no accounting for taste, and to me a huge benefit of DIY'ing is that we get at least potentially to make things look the way we like them to.

BTW, I'd like to see some more discussion on DIY coil winding, and even more so on properly potting or otherwise binding the finished coils.

Edited by Passinwind

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[quote name='The Shrek' timestamp='1491233409' post='3271426']
Thanks Stevie. Guys I hope I am not being forward in asking this question. I would gladly pay upfront for the service if there are any of you basschat guys who would be prepared to build a proper crossover for my project. Just advise me on what speakers to buy to match the appropriate crossover build. I am in Northern Ireland so I will gladly pay for any excessive post and packing and any other costs.

Michael
[/quote]
Hi Michael, though it won't be fully optimised for your particular drivers you can always use a bog standard crossover circuit instead of just a capacitor to protect the 5" unit from the bass (and most of the power). The simplest would be a 1st order crossover to gradually remove the higher frequencies from the bass unit but a better way would be a 2nd order design Which has a quicker cut off for both speakers at the crossover point. You can get the basic calculations done here https://www.diyaudioandvideo.com/Calculator/SpeakerCrossover/ Go for the Butterworth for 1st order or the Linkwitz-Riley for the 2nd order.

It'll only work if your speakers are more or less the same sensitivity.

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[quote name='Gottastopbuyinggear' timestamp='1491309555' post='3272002']

Not the sound you want - now he tells us!

I'm still relatively inexperienced with all this (from a user point of view) so I'm quite keen to do a bit of experimentation to see how a different speaker would sound in the real world. I need to revisit the modelling to check but I did look at putting a Beta 12 in the Mk1 cab (partly to free up a Beyma for a Mk 2 build, and partly just for curiosity) which I think predicted a similar bump of 2 or 3dB around 110 Hz or so. Of course the Beta 12 does have a pretty big hump in the high mids, so overall I guess the sound would be substantially different.
[/quote]
Sorry ;)

It's a long time ago now but the design was specced by people on here, who wanted a neutral/flat response and lots of lovely bass in a compact cab, it wouldn't have been my choice but it does mean you can eq in the response you want, as I have been doing. I've had some mild teasing because what I've ended up with is pretty much the response of a Beta 12 in a small box drawn permanently onto my graphic. I'm not a sophisticated bass player :)

Stevie is taking the next logical step, adding the horn and driver and tweaking the crossover means the response is flat all the way up as far as a bass is concerned and you can pretty much dial in what you want, all with less distortion and more controlled dispersion of the sound

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[quote name='Phil Starr' timestamp='1491337619' post='3272299']
Hi Michael, though it won't be fully optimised for your particular drivers you can always use a bog standard crossover circuit instead of just a capacitor to protect the 5" unit from the bass (and most of the power). The simplest would be a 1st order crossover to gradually remove the higher frequencies from the bass unit but a better way would be a 2nd order design Which has a quicker cut off for both speakers at the crossover point. You can get the basic calculations done here [url="https://www.diyaudioandvideo.com/Calculator/SpeakerCrossover/"]https://www.diyaudio...eakerCrossover/[/url] Go for the Butterworth for 1st order or the Linkwitz-Riley for the 2nd order.

It'll only work if your speakers are more or less the same sensitivity.
[/quote]

With a first order cap you'll be somewhere in the ballpark and it will sort of work. Once you add a coil to the circuit, the results could be disastrous unless you know what you're doing. I really wouldn't.

In fact, using a crossover calculator is doomed to failure because they work on the assumption that you have a flat impedance curve on all your drivers, that they have a flat and extended frequency response and are time aligned. None of which is ever the case.

Edited by stevie

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[quote name='Passinwind' timestamp='1491324646' post='3272148']
BTW, I'd like to see some more discussion on DIY coil winding, and even more so on properly potting or otherwise binding the finished coils.
[/quote]

We're a bit nerdy on here, but I don't think we're *that* nerdy. :)

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[quote name='stevie' timestamp='1491339689' post='3272320']
We're a bit nerdy on here, but I don't think we're *that* nerdy. :)
[/quote]

Pity.

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[quote name='stevie' timestamp='1491339689' post='3272320']
We're a bit nerdy on here, but I don't think we're *that* nerdy. :)
[/quote]

Co-incidentally, I was reading about winding DIY inductors for the midrange EQ in an Ampeg style preamp earlier, so I'm not entirely sure about that...

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[quote name='stevie' timestamp='1491339089' post='3272314']
With a first order cap you'll be somewhere in the ballpark and it will sort of work. Once you add a coil to the circuit, the results could be disastrous unless you know what you're doing. I really wouldn't.

In fact, using a crossover calculator is doomed to failure because they work on the assumption that you have a flat impedance curve on all your drivers, that they have a flat and extended frequency response and are time aligned. None of which is ever the case.
[/quote]

We'll have to disagree here I think. First of all we are talking about an instrument speaker. Michael might not get a flat frequency response, if that is what he is aiming for, but it could still sound quite good, and be better than his single driver.

By going for a 2-way crossover you are trading some anomalies which you mention for the genuine problem that with no roll off of the bass you will have two drivers that will be radiating the same frequencies at different levels and from different points creating all sorts of comb filtering and other reinforcement and phase problems.

Most of my experience in designing crossovers has been in hi fi cabs, where if anything sound is more critical. I've never really been a fan of complex crossovers, adding components in the form of notch filters and so on never exactly match the frequency anomalies of the drivers and introduce problems of their own. My own preference in listening tests has always been for 2nd order crossovers with the minimum of components, though I only ever use drivers that are more or less flat in the octave on the far side of the crossover point. If Michael chooses the drivers wisely a 2 way crossover might work well. So might a single capacitor high pass filter.

Passive crossovers are never perfect but I wouldn't want to put Michael off from trying, just as long as he understands he won't know what his design will sound like until it is built.

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Well, at the risk of boring people to death, I can tell you what little I know. I have an electrically powered winding machine, quite ancient, but it's a proper winding machine with an electronic counter and cutoff. So it's not really DIY and I've used it in the past to produce thousands of coils for commercial speakers.

As far as potting is concerned, I use the same air-drying lacquer you would use to finish your pine chest of drawers. I apply it to the outside of the coil. It only penetrates through a few windings but works well enough to prevent unwinding when you're handling the coil, which is the aim. The bobbin keeps the rest of the coil held tightly together.

That's always been good enough for me, although there are better ways of doing it. The most popular is to use enamelled wire coated with a temperature sensitive adhesive. You wind your coil and pass a large electrical current through the coil to heat it up and glue the windings together. You need to do that if you don't use a bobbin. Then there is vacuum dipping, where the coil is suspended in a tank of varnish and a vacuum applied. The coils are then transferred to an oven to bake.

None of this is DIY though. I'd certainly advocate using wood varnish for your occasional DIY coils.

Edited by stevie

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When the original 1x12 Design Diary was spec'd it was for a single driver 12" cab that was capable of keeping up with a loud drummer (120dB SPL). It was to be wide enough to take a rack mount amp with no overhang and was to be easy to build. Phil and Stevie achieved this with the MK1.

I bought a Beyma SM212 fully intending to build the MK1 but Beyma revised the specs on the SM212 (for the better) so I asked Stevie, who has the measuring gear, if he would like to check it. It turned out that Beyma had been turning out drivers that were better than the original published spec and that my driver and Phil's were almost identical. Beyma had just revised the specification to match the real performance of the driver.

While I was with Stevie that first time, he pulled out a small cab fitted with an OEM version of the Deltalite 12" and a properly designed crossover and tweeter. The low end was nowhere near as good as the MK1 but the midd and top were so clear. I was persuaded to go the MK2 route.

He convinced me that a good horn and compression driver could improve dispersion so that I could hear myself even with a small cab on the floor on a pub stage.

I love an old school hump (that looks so wrong in print) but I have always thought that flat speakers and a good EQ is the way to go rather than a "voiced" cabinet.

I had been in conversation with Passinwind regarding pre-amps and the design he came up with has a really flexible EQ that can dial in an old school response or just about anything else I want. All with a really low noise figure (virtually no hiss). I had hoped to get my DIY amp ready for the Bash on Sunday but illness and the late arrival of some components ruined that. I will get the amp finished in the next week or two then I will have a complete rig I built myself. Of course I will post pictures on here as soon as it is finished.


The think is there is no right or wrong, it is a personal thing. Phil's idea of a smaller cab creating a low mid peak is as valid as the "HiFi" cab. The choice is yours.

Edited by Chienmortbb

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[quote name='Chienmortbb' timestamp='1491380414' post='3272501']


The think is there is no right or wrong, it is a personal thing. Phil's idea of a smaller cab creating a low mid peak is as valid as the "HiFi" cab. The choice is yours.
[/quote]

There's no disagreement between us all about this, before the Mk1 I had the Beyma's in a couple of PA cabs with some really meaty horns crossed over at 1600Hz. They gave me the best sound I've ever had with a bass and that's what inspired me to try them with the horns disconnected, and ultimately led to the design of the Mk1.

The reason for wanting to do a small cab is really only because I can't stop fiddling with designs to see where they can be pushed. If it is successful we'll have the basis for a lightweight version giving home builders another option, if it isn't successful then you'll know not to go there.

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Sorry guys but I am way out of my depth. I will have to opt for the most basic and simple way to get a 12" and a 5" in one cab. I really enjoy the box building part, but the techy stuff makes me want to slash my wrists.

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[quote name='The Shrek' timestamp='1491404552' post='3272772']
MY HEAD HURTS... ����
[/quote]

:lol:

I know how you feel!

:scratch_one-s_head:

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[quote name='fftc' timestamp='1491409860' post='3272831']


:lol:

I know how you feel!

:scratch_one-s_head:
[/quote]I fully understand as Phil and Stevie have far more knowledge than me and have put me right several times over the years when I have had that dangerous thing "a little knowledge". What this exercise has taught me though is that many, no most, commercial builders, whether boutique or major players, North American or European are not experts in the design of speaker cabinets. That may be harsh, it may be they don't know much about speaker design, just like me. It has reinforced the fact that the amp and speaker are two parts of the same system and so must be spec'd together. Most importantly it has shown that a box with a big speaker in is not of itself a good bass cabinet.

I also know that over the past four years since Phil, Stevie and others started the design of the MK1 and that morphed into the MK2 in its variants, everyone involved has learnt a lot. What I have learnt is that many brands I respected have lost some of my respect as I now know how they cut corners. I have learnt the compromises they make for the sake of hitting a price point. How getting the smallest, lightest compromises sound quality. BUT that sound may be sound you are looking for so don' t believe the marketing or even other bassists as everyone has a bias.

That bias may come from believing the marketing blurb or liking or hating the aesthetics. It is silly I know but I would rather run down Poole High Street naked than use Markbass. It is irrational but there you go. In contrast I owned a monster Orange staggered 4x12 guitar cab in the early '70s. I still dream about that cab. Go figure then think about your own prejudices.

Like Phil I have another speaker project in mind but that will have to wait. I have the amp to finish and many other projects. In the meantime I will take my cab to as many Bass Bashes as I can get to so you can hear it for yourself. Oh and don't forget that there is no such thing as a stupid question, there are only stupid answers.

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[quote name='The Shrek' timestamp='1491409735' post='3272829']
Sorry guys but I am way out of my depth. I will have to opt for the most basic and simple way to get a 12" and a 5" in one cab. I really enjoy the box building part, but the techy stuff makes me want to slash my wrists.
[/quote]

Michael, just try a 12uF cap (polypropylene is best) in series with the 5" driver. I'm guessing you're going to be using the Faital Pro 5, as I don't know any others. Don't forget to give it its own cabinet of between 1 and and 1.5 litres and fill it with wadding.

As it is likely to be louder than the 12, you'll probably need an L-pad attenuator to quieten it down a bit. Get a 100W one, wire it according to the instructions and set the level by ear. Connect the 12" speaker directly to the input.

I can't make it any simpler than that. But I still think you'd be better off building one of the designs in this thread. :unsure:

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I'd like to say a big public thank-you to John, aka Chienmortbb, for his invaluable help in getting this project together. Not only did he build and supply the prototype cab for me to work with, but he also supplied the drivers. And he burned the candle at both ends to get a working system together (just) in time for the SW Bass Bash. I hope you DIY builders appreciate the effort he has made on your behalf.

I did promise you some measurements on this second system, but what with the last-minute rush to get John's cab ready for the SW Bass Bash, I forgot to save a full set of measurements. I did save a normal frequency response measurement, however, and you can see it below. All the off-axis measurements looked good and the impedance didn't dip below 7.3 ohms - I just didn't save any.

The response curve is at a distance of 2 metres. It's impressively flat, thanks to a couple of non-obvious tricks in the crossover and the fact that the horn mates well with the compression driver.

[IMG]http://i64.tinypic.com/208zh5h.jpg[/IMG]

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I have been playing at home through the cab since the bash although yesterday I filled the screw holes with dowels and re-painted the cab, pictures below.

I said to Phil at the bash, the first thing I noticed was how poor my technique was, there is no hiding place. Over the days since I have tried to improve my technique and I am loving the sound. The cabinet shows how good my old HH amp was for its time. It has a fully parametric Mid control. allowing me to dial in just what I want. I can get a wide variety of sounds. A modern. slightly smaller version of the amp would be great. I am hoping my self build amp does something similar as the EQ is similar (but quieter).

The great thing is that if I use the Parametric to get an "old school" peak around 100-200Hz it sounds right, not "old school with a tweeter". That makes sense when you think of it. When you are DI'd through FOH, the speakers are full range. just like when you hear recorded bass on a good HiFi system. Phil mentioned how nice the notes at the dusty end sounded at the bash. That has changed how I play, when I am noodling, I am often at the dusty end (it ain't so dusty anymore) letting those high notes ring.

Sadly my next gig is a month away so unless I hire a rehearsal room, I cannot try it too loud. I might frighten the natives and take it to open mic night this week.

Pictures:

1. The screws were removed and replaced with dowels. Once dry the top and edges were sanded, ready for being re-TuffCabed.




2. The edges look much better although in future I would just use dowels, or maybe even small battens, and a proper dowelling jig as it was a lot more work this way. It is strange how the pictures show up imperfections well. The join between the top and side is almost invisible to the naked eye and the irregular finish is hardly noticeable. Next put the corners back on and attache the handle. I also need to have the [email protected] out as it is held in by wood screws and I have the TEE nuts to make a good safe fix.


When I weighed the cabinet I could not find my luggage sales and my bathroom scales were fancy ones that will only work when you stood on them. So I had to weigh myself (13st 9Lbs since you ask and as I am over 6ft, the beer belly does not count). Then I stood on again holding the cabinet. I am not convinced it was accurate so I will try it again with the luggage sales when the handle is on.

Edited by Chienmortbb

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[quote name='Phil Starr' timestamp='1491671138' post='3274704']
Congratulations Stevie, that's impressive. You have to try it with vocals :)
[/quote]

Thanks Phil. It sounds really nice with vocals, Phil. Like a very good floor monitor.

By the way, I located some more measurements of this system, which I will post as soon as I can.

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