What DIY reflex cabs for 3012ho?

[richrips]

Hi All,

A few years ago I built 2 BFM Jack 12 cabs. I've been pretty happy with them, but as I live in a small house and am constantly having to pack them away and load them in the car, their weight is becoming a bit of an issue. It also seems that the horn-like design loses some clarity/detail/immediacy from the sound, but trades this off with good sensitivity and dispersion. Seeing as I don't really need the sensitivity or dispersion whilst playing small cornish pubs at medium volume, I'm drawn to the idea of more traditional reflex boxes that can be made of lightweight, low/dual density ply. I have looked at the fearless designs and they seem pretty good. I have 2 Eminence Kappalite 3012HO drivers in the Jacks which I intend to re-use. Here's my ideal bass cab description:

-Uses 3012HO drivers
-Simple reflex design
-Tall and thin to get the sound up off the deck to where I can here something similar to the audience
-Useable with piezo tweeters to avoid the need for crossovers.

Are there any plans (preferably free) out there that tick all these boxes? I appreciate that the 3012HO has relatively strong mids relative to lows, so a cab design that may level this issue somewhat would be cool, if possible. I run a Mac so WinISD is not playing ball.

...Then I'm going to stain the finished cabs in translucent blue, maybe with glitter clear-cote.

Any suggested plans much appreciated.

Many thanks,

Rich

[6v6]

I assume you've seen the [url="http://www.eminence.com/pdf/Kappalite_3012HO_cab.pdf"]designs provided by eminence[/url]?

If possible I'd have another crack at getting WinISD working - I ran it under a windows emulator on Linux, so I guess you may be able to do the same on a mac.

[richrips]

Hi 6v6,

No I hadn't seen those actually. The "Large vented cabinet" seems like it has a decent bass response with smoothish mids. Couple of questions:

-Can I put one rectangular vent instead of the three round vents as long as I keep their corss sectional area and length the same?
-Does it matter how I distribute the volume of the cab (what shape the cab is)?

Cheers,
Rich

[bertbass]

Have you seen the new simplexx cabs by BFM? Might be worth a go.

[richrips]

Hi Bert,

Yes I saw those. I may yet end up buying plans for them. Has there been a simplexx vs fearless comparison? Anyone built the eminence box to spec?

Cheers,

Rich

[bertbass]

BFM has got a forum for them here, http://billfitzmaurice.info/forum/viewforum.php

[richrips]

Hi all,

I've spent quite a bit of time on the BFM forum, T£££bass, etc and am still curious to know if anyone can answer these particular questions:

-Has anyone built the large Eminence box they provide spec for that utilises the 3012ho?
-Does the shape of a port make a difference? Does square sound like round as long as the area and length are the same?
-Will building my cabs taller and narrower affect the sound relative to shorter and fatter?
-When building a 2x12, is the volume simply twice that of a 1x12?

Anyone who has built reflex cabs using the 3012ho, I would be interested to hear from you!

Many thanks,

Rich

[LawrenceH]

-Has anyone built the large Eminence box they provide spec for that utilises the 3012ho?
I haven't, but IMO 100 litres internal volume is too big for a 12" cab, and considerably bigger than the Jack 12 you are looking to replace. That speaker should work nicely with about 40 to 60 litres internal volume from what I remember.

-Does the shape of a port make a difference? Does square sound like round as long as the area and length are the same?

Shape doesn't make a difference to tuning at low power, it can make a difference at high power as some shapes direct airflow more efficiently. Having said that, a rectangle will work just fine as long as it has a decent cross-sectional area and isn't excessively narrow. BUT, if the inside end of the port is continuous with the inside of the box, then the effective length of the port is slightly longer and the shelf of the port needs to be slightly shorter to compensate for this end effect.

-Will building my cabs taller and narrower affect the sound relative to shorter and fatter?
A bit, but not so you'd notice much on bass guitar as long as you avoid a cube, especially if you put some absorption in to damp internal standing waves, something that's a good idea in any case. The biggest difference is probably going to be due to any impact shape has on driver placement relative to your ear.

-When building a 2x12, is the volume simply twice that of a 1x12?
Yes, if we're talking about internal volume.

[richrips]

Hi Lawrence,

Thanks for such concise answers! Interesting that Eminence offer such a range of speaker sizes for one driver. I wonder if anyone out there has built the big one for bass. Does seem like a large volume. I'm not sure the 3012HO is a particularly good choice for a single driver plus tweeter reflex cab. I may have to sell my whole rig and look elsewhere. Maybe the 3012LF or a different high power neo driver with a smoother response across a broad frequency range.

Cheers,

R

[LawrenceH]

I think it's a decent choice. Bung it in 50 litres, tune around 50-55hz and it'll work better than most 112 cabs out there. You could always tame the rising upper-mid response with a simple high-pass filter, either a single inductor, or inductor plus cap would easily give enough flexibility to cross to a tweeter smoothly

[Phil Starr]

Hi, how soon do you intend building this? We are working on a design for a 50l cab which will match this driver, slightly derailed because I joined a new band and have 25 new songs to learn. This will be a free design for anyone to copy. The 3012HO is an excellent driver. http://basschat.co.uk/topic/227904-1x12-cab-design-diary/

You might find this interesting too http://basschat.co.uk/topic/200152-1x12-diy-cab-build/

If you go onto the eminence site you will see that the large cab has worse power handling than the more compact cab and they recommend using it with reduced power. This is a feature of all reflex designs not of this particular speaker. I really wouldn't go any bigger than about 70l nd we ended up going for 50l as a good compromise.

[richrips]

Hi Phil and Lawrence,

I've been following both those threads in the background actually, very interesting stuff.

Lawrence, I like your suggestion of some kind of high pass filter. ideally this would just flatten the mid hump to a more reasonable level rather than shelve suddenly. I don't know how to go about designing that so any suggestions would be welcome. Would this HPF effectively be a power sump for mid frequencies? Would making the box bigger reduce mid-output similarly (albeit with a reduction in overall power-handling) ?

My current Jack 12s have an external volume (the overall cubic exterior shape) of 116 litres each. I haven't found them too problematic to move around, but as a lot of that volume is taken up by the throat/horn I agree with you that 100L may be pushing it volume-wise in a simpler reflex design.

My current design ideas are:
-Build the cab narrow (say 40cm)
-Use 9mm dual density Ply (hardwood outer laminates, softwood inner laminates)
-Brace carefully (bracing requirements should be reduced using a narrow design as the maximum distance from any edge will be reduced on each panel
-Use round ports (this seems to be a lighter weight option relative to a large, braced, wooden, shelf type port. Also it removes the "inside edge" issue that Lawrence mentions above.
-The port length for deepest reasonable tuning (before the power-handling drops dramatically) will then determine the front-to-back depth of the box.
-Tweeter to be mounted at the very top of the box, centrally. Thinking about a decent piezo.
-3012HO Woofer to be mounted the nearest reasonable distance below tweeter as possible to keep all sources up where they can be heard clearly.
-Possibly smoothing HPF on the woofer only to reduce mid hump.

What do you think?

R

Edited March 6, 2014 by richrips

[Phil Starr]

Hi Rich, there's a lot of questions there

I'll try and deal with the woodworking ones first. If you do go for a 50-60l cab then it is quite small and you don't have much flexibility with shape. For example with a 30cm driver and a 10cm horn plus enough wood left to be strong enough to fix to you have a 50cm high cab and you want it 40cm wide. this means that for a 60l cab it will only be 30cm deep. This compromises the port as it can only really be 20cm long or it gets too close to the rear panel. If you want to tune deep then you need to restrict the port width or bend the port which introduces more problems. If you use a narrow port it doesn't need to be so long but can suffer wind noises at high levels. If you use a deeper cab you end up with a square front and an almost cubical cab where all the panels resonate at the same frequency. In practice you will come back to the 30x40x50 shape or thereabouts.

Now the horn/tweeter. Firstly there are no decent piezo tweeters in reality, I've tried quite a range over the years and they do a job but with limited success. The old Motorola's which most of the currently available ones base their designs on were as good as anything the current Chinese mass produced ones are fairly poor and production in Europe and the States has ceased as far as I know. They'll colour in a bit of high end fizz and that's it really.

9mm ply really is very flimsy for making a high powered cabinet, The only way to stop it resonating and transmitting sound is to use extensive bracing. The bracing could easily end up weighing the same as the rest of the cabinet and adds a lot to the complexity of building the cab. I know it is very trendy in these pages to go for rigid, lightweight designs but it takes a lot of development to get it right, it may make sense for commercial builders with CNC routers and design budgets but don't knock the intrinsic properties of 3/4" ply.

Secondly, why do you want a horn? Most of the stuff you want to hear from a bass ends at 4-5000Hz. A lot of horns don't cut in until this level, so are irrelevant to the sound, all they'll add in is string noise. If you want a real 'hi fi' accurate sound then you want something that covers the 1-5kHz range. Something like a PA horn. I sometimes use my PA speakers for bass and it does sound nice, The horns in these crossover at 1.6kHz. If I wanted a cleaner bass sound designed in I'd probably go for a 6" driver or smaller to provide the 1-5kHz range. If I was designing with a wide frequency horn or a mid range driver like this in mind I probably would go for a 'proper' LF driver but the 3012HO is a capable driver and as you have them I'd definitely try them first.

[LawrenceH]

Hi Rich,
Typo on my part... of course I meant low-pass filter! Changing box size will have no significant effect on mid-frequencies, at least not in the way you hope. But a filter that cuts off really suddenly is harder/more expensive to achieve anyway, the good news is a simple one- or two-component filter should achieve what you want. Designing this accurately requires the impedance curve and frequency curve of your driver. Measurement of impedance can be done quite simply, google 'impedance jig' and look for the one that's just a few resistors and uses your soundcard. And/or you can trace manufacturer's curves using free software, though measurement is obviously the best way. Either way you can then use software like Passive Crossover Designer (also free, need excel to run) to design the filter. Alternatively, a rough-and-ready improvement could just be achieved by ear and guesstimating based on the published curves and standard calculators, especially with a single inductor. Might have to try a few different values (or get a deliberately high value one and unwind until it gets where you want). Yes, the low-pass would just burn off the lost output as heat. Need to use a decent quality inductor for best results.

Designing a crossover to a horn does require measurement data to get right. Having said that, quite a lot of cabs seem to have been designed with total disregard for the 'ideal' procedure and they often sound fine in this context! You can get very anal about it but so many bass guitar cabs are nowhere near flat but work well enough in practice (eg your Jacks) But as Phil says, you may find even with a gentle LPF that you don't really need a tweeter. An inductor alone only attenuates at 6dB/octave so you should still get quite useful extension to 3 or 4kHz despite dragging down the mid peak, which is centred around 2.5kHz.

Agree with Phil on the piezos, I have not had good experiences. I bought a whole set of the BFM-recommended ones from Leland in the US, and they all sounded p***-awful in my opinion regardless of crossover and regardless of how many were being used in that crazy glued-together 'array'. Plus I've never heard a cab loaded with a piezo that I didn't think was harsh in the midrange and 'grainy', for want of a better word, throughout the treble. Btw the original Barefaced Midget design as far as I can see used the 3012HO crossed to an Eminence APT80, which only kicks in around 3.5kHz. I'm not sure but I imagine this might have been with either a very simple low-pass on the woofer, or none at all, just rolling in around 4kHz where the woofer naturally starts to tail off rapidly. Not perfect but a lot of people seem very happy with theirs. Again Phil's point about using a decent PA compression driver/horn is absolutely right, but it is a rather expensive option as well as complicated to design properly, so I'd be strongly tempted to start without and maybe try the APT80 before going for anything more complex.

I am on the fence regarding the use of very thin woods, at least for bass guitar. I'm coming round to the view that Phil and Stevie have on using thick and heavy stuff for premium sound quality. On the other hand, if you have built a Jack 12 then decent bracing will not be any more complex by comparison, and IMO there are weight savings that can be made without noticeably degrading sound quality in this application. I actually built some monitors from (admittedly bloody heavy) 9mm birch and they are the nicest sounding pro-audio cabs I own, by virtue of their decent drivers and the fact I spent a lot of time and effort on the crossover. If they were made from 18mm material they might sound even better, but then I would barely be able to lift them! One thing, decent poplar core with a different facing wood is not something I've been able to come by in DIY quantities so if you know a source then I'd be very interested

[richrips]

Hi Phil and Lawrence,

Thanks for getting back to me with some useful replies! All this has me wondering if am am maybe better selling the Jacks as-is and investing in a couple of 3012LF's for 2 deepish small cabs or one 3015LF and a small high mid driver for one larger full range cab (like a Fearless 15/6, but again taller). I am somewhat concerned that the throw on a 15 may mean that I wouldn't get a clear sound in your typical cornish pub...

I agree with your ideas for the 3012HO's with that tweeter. The other tweeter I've heard good things about is:

http://www.bluearan.co.uk/index.php?id=MON100190

How does that compare to the APT80?

I don't think I need absolutely tonnes of SPL due to small venue size, but I do want depth as I play a mix of reggae and funk mostly.

Hopefully land on the best option soonish, thanks for your help thus far. Fascinating stuff.

Rich

[LawrenceH]

I've not used that Monacor but at ten quid I'd not expect miracles! The apt80 is not amazing but good enough in this application though you will have a slight off-axis hole crossing that high. I'd stick with the 3012ho's since you have them. Designing a crossover for the lf variant is annoying and necessarily more expensive, with a more expensive midrange driver requirement to boot. Unless you like clank and no upper-mid articulation, then you could run it alone. In a given box there's not much benefit to the Lf in terms of bass output until you hit the power limits of the HO, which is going to be bloody loud. They can take a lot so if your amp has the juice just design a cab for smooth bass roll off then crank the bass in the amp if necessary. If you know the eq characteristics of the amp you can even tailor the cab to suit

[Phil Starr]

The Monacor is designed to crossover at 5kHz so you couldn't use it with the 3012lf unless you wanted a hole in the response.

I'm not a puritan about thin walled cabs by the way, I can see advantages with a rigid cab but the weight advantage isn't all it's cracked up to be. Alex Claber has stated that weight saving isn't his main reason for building cabs that way. What I'm sceptical about is that the difference between a well made lightly braced conventional cab and an equally well made thinner walled and heavily braced cab is that apparent in a gig situation. Since the weight saving is minimal and the complexity of build greatly increased I question how far it is worth it. A reasonably well braced 12mm cab might be worth thinking about too. One day I'l get round to building two cabs and do some A/B testing. Incidentally I have a 15" Deltalite in a 3/4" cab and the total weight is only 18kg, your cab will be smaller and lighter.

Having modeled the 3012HO as part of our design process I think it would make a great cab on its own, though a single one in a West Country pub might well let the higher frequencies bypass you, two together would probably be OK.

The sound is going to be very different from the Jacks even though you are using the same speakers, because of their design the Jacks have a 10dB difference in levels between the horn output at 300Hz and the reflex output at 100Hz and this colours the sound. the reflexes won't be as loud but the bass is going to be the same as the mids so the balance will sound deeper subjectively.

One thing occurs to me, you really aren't too far away. We are looking for a 3012 to trial as part of our design, if you came up to Somerset for the day anytime it would be simple enough to clamp one of your speakers into a cab and for you to try it, if the sound is one you like the dicision is made. Ideally we'd like to run some tests at the time but this could be fairly flexible. I've got a couple of 50l cabs here.

Edited March 7, 2014 by Phil Starr

[richrips]

Hi Guys,

Thanks again for the input. Now I'm intrigued to hear what a 3012ho sounds like in regular reflex box. I'd be keen for nearer 70L to get a bit of bass extension for slightly reduced power handling/efficiency. The APT80 sounds like the tweeter of choice in that case. As for build material, The Jack's, made from 12mm Birch ply and this feels extremely stiff, but isn't light weight. I'm on the lookout for some ply with light inner laminates and tough outer laminates. Can anyone suggest a source in the south west?

I'd love to bring a Jack up to Somerset and spend a day trying speakers in different cabs. Unfortunately my car is dying and I'm loathed to venture far from Falmouth until I have replaced it.

If I can get some ply, I'll happily put together a suitable cab and make some comparisons.

Cheers,

Rich

[LawrenceH]

Your best bet for composite might be the Chinese hardwood-faced ply, that's often with a lighter core, if you can find some of ok internal quality. Southern Timber in Newton Abbot carry this with poplar in the core but I've not used it myself - will try and get over there myself at some point to check it out, may well be void-y and low ply. Should be nice and cheap though. Probably someone closer to you carries it?
Trago also near Newton carry decent hardwood-throughout ply that's still a fair bit lighter than birch and has a decent number of plies, minimal voiding IME, I don't know if the Cornish branches carries sheet material but might be worth a look? The only Cornish supplier I've used myself was Timber Depot in Saltash but unfortunately they've closed down.

[6v6]

You've got some great responses here!

FWIW I deliberated over the wood choice for a while and in the end I went with 15mm birch, which is relatively heavy but very strong and stiff.

Seems a reasonable compromise as it meant I needed very little internal bracing, and I did without battens on the corners (biscuit joints + screws, which I recommend as an extremely easy way to make strong joints if, like me, you're not a super-skilled woodworker).

I can probably weigh the cab later if you like, but it's an easy lift despite the relatively heavy ply and the relatively heavy ceramic driver. I've gigged it quite a lot now, and it's solid with no issues at all due to resonance etc.

My advice is just get stuck in - find a way to get winISD working (old laptop kicking around running windows or a windows emulator?) or use an existing design, forget about the tweeter unless you're sure you need it - IMO just keep things simple, and get the box working right, you can always add a tweeter later (I decided I didn't need to).

Personally if you have the 3012HO's already, I don't see the point in investing £££s in more drivers immediately, might as well build one box with what you have and see how it sounds. You can always refit it to the Jack and sell it later if you want something different

[discreet]

I've got two Jack 12s with Kappalite 3012HOs in, too. They're not so much heavy (mine are 18kg each), just awkward to carry - particularly as I fitted handles on the top for a retro look... Some gigs/rehearsals needed a one-cab solution so I bought a 4ohm Schroeder1212L, which I'm very happy with. I'd be very interested to know how your 3012HOs fare in a non-BFM cab, though.

[discreet]

[quote name='richrips' timestamp='1393500312' post='2381005']
...I'm going to stain the finished cabs in translucent blue, maybe with glitter clear-cote.
[/quote]

And we'll need to see pics as well, obviously.

[richrips]

Ha Cheers guys, Indeed this thread is rather fruitful to say the least!

6v6, what cab did you build with what outer dimensions? The 12mm I used on the jacks seems very stiff indeed, but I can see benefits to thicker ply if the panels are bigger.

I have a background making surfboards and latest tech on those is to have very low density foam cores, a higher density foam outer, then glass/epoxy skin with carbon where you really want stiffness. This is what's driving my idea of having ply with tough/stiff outer layers and low density inner layers. If thicker ply (say 15mm) with a very light core and tough hardwood outer exists, I'd be interested to see how its weight compares to say 12mm birch.

I also work as a biologist and we recently had 100 nestboxes built of this stuff:

http://www.ecosheet.com/

Data sheet:

http://www.ecosheet.com/files/8513/6681/5676/Ecosheet_Specification_Sheet_v5.pdf

Good stiffness thanks to the moulding process which produces solid outer walls and a more open interior structure. Weight is similar to ply of same thickness.

Cheers,

Rich

[6v6]

[quote name='richrips' timestamp='1394536973' post='2392310']
Ha Cheers guys, Indeed this thread is rather fruitful to say the least!

6v6, what cab did you build with what outer dimensions? The 12mm I used on the jacks seems very stiff indeed, but I can see benefits to thicker ply if the panels are bigger.

[/quote]

The spreadsheet in post #15 of [url="http://basschat.co.uk/topic/200152-1x12-diy-cab-build/"]my build thread[/url] provides dimensions (I'd have to check if they were the final iteration but they look about right). It's a pretty standard 1x12 cab, probably on the large size of average for a 1x12.

If you used a different jointing method and some bracing I expect 12mm birch would be OK, but I wanted to keep the construction (particularly all the joints) as simple as possible so used 15mm as a compromise, 18mm seemed excessive for this type of box and I didn't want it too heavy.

[size=4][quote name='richrips' timestamp='1394536973' post='2392310'][/size]
I have a background making surfboards and latest tech on those is to have very low density foam cores, a higher density foam outer, then glass/epoxy skin with carbon where you really want stiffness. This is what's driving my idea of having ply with tough/stiff outer layers and low density inner layers. If thicker ply (say 15mm) with a very light core and tough hardwood outer exists, I'd be interested to see how its weight compares to say 12mm birch.
[/quote]

I'm not an expert, but IMHO you'd want to think carefully about what jointing method you use if you choose a ply with a very low-density core. If you use one of the simpler methods (glue/screw butt joints or biscuits) the joint will surely be much weaker, since the screw/biscuit will be going into really soft wood? Some of the cheap far-eastern ply I've used would probably fall to bits very quickly if you used the method I used on my cab with the void-free birch.

I guess you can reinforce the whole thing with battens on the corners to get around that but I chose to avoid that as it's all extra weight and uses up internal volume.

[LawrenceH]

[quote name='6v6' timestamp='1394574368' post='2392994']
I'm not an expert, but IMHO you'd want to think carefully about what jointing method you use if you choose a ply with a very low-density core. If you use one of the simpler methods (glue/screw butt joints or biscuits) the joint will surely be much weaker, since the screw/biscuit will be going into really soft wood? Some of the cheap far-eastern ply I've used would probably fall to bits very quickly if you used the method I used on my cab with the void-free birch.
[/quote]

I've found lightweight poplar fine with both butt and dado joints, glued and screwed, but it was essentially void free. Stuff with large voids in is problematic for finishing and I wouldn't trust it to behave structurally/sonically, I used some horrible far-eastern stuff for a prototype and it was a pain.

Foam composite strenght is totally reliant on not having significant voids (and on good bonding of the skin to the low density inner material), I'd have thought those concerns would still apply to a large degree with ply. There are some great builds on talkbass and elsewhere using foamcore, if you have the skills and tooling already then perhaps you could consider having a go?