LawrenceH

Xmax is 8.8 calculated Faital-style. But it's all a bit academic beyond a certain point as different speakers will behave differently with large signals and this is hard to quantify in a single figure even with sophisticated Klippel-type analysers, better to use your ears. I have said to Phil et al previously, that I think the response in the low-mids plays a big role in how people feel about a speaker, along with the shape/frequency of the resonance peak. Noticeably the Beyma charts show a dip around 300Hz, something I very commonly replicate by EQ as a sound engineer, since it's just a region where you get a lot of wooliness in real-world spaces, and it's also roughly the region where you get a scoop with e.g. Markbass VPF - removing some here often helps clean up or 'tighten' the sound. I will be interested to see if this element of the mf response chart is replicated in Phil's design. It could be a good thing for a lot of players in my opinion, but it'd be interesting to see how a player whose sound is very focused in this region felt about these cabs. Another issue that's rarely touched on when people get focused on design using T-S-based simulator programs etc is the role of baffle step in the real-world frequency response, which is very problematic to deal with once speaker cabs exceed a certain size, since it becomes so intrinsic to the space. When is 'flat response' truly flat? It's easy to get too hung up about things like modest bumps eg in the midbass, whereas if you saw what any cab response looked like in-room from a particular listening position, you would just give up in disgust! Yet our ears adapt

I think Phil's point earlier, that modern speakers are actually less efficient, is very significant not just in terms of the issue of why we seem to need 'more watts' these days, but for the implications this has for the sound of modern bass guitar.

If you've got it in a ported cab already try stopping up the ports and see how you like the sound - Phil's right about the roll off but with micro amps packing hundreds of watts, you can just boost the bass to compensate and it might give you a good practice cab. That speaker should take it. The good thing about this approach is it's free, quick and fully reversible

If you want more overall volume, but not necessarily more true bass, then I'd think about using as big a diameter driver as you can cram into whatever box size is suitable for your transport needs, ie moving from 8" to a high-sensitivity 10" (or to 2x8" if the slimmer form-factor makes it more convenient). Bigger radiating driver area makes more of a difference than just increasing the wattage input but keeping the driver the same.

For electric bass, the 'natural'/'reference'/'typical' sound is arguably a recorded signal, direct into a nice channel strip complete with HPF and various sources of dynamic compression/limiting at tracking, (and tape), mixing and mastering stages, then back out through hifi speakers (with further LF rolloff) or (more recently) headphones. It definitely doesn't exactly correspond with the the electrical output from the pickups at any rate! Bass guitar gives a very musically-pleasing sound through my sealed stage monitors, the -3/-6 points on those must be pretty high. I am becoming more and more of a fan of the gradual rolloff even at the expense of overall midbass levels.

As alluded to already, volume pots themselves also contribute to perceived brightness through the height of the peak at resonance, as opposed to capacitance loading which alters frequency of that peak. For absolute max top end not only should you bypass the tone control but also the volume pots (wire pickups straight to output jack). If that's still not enough then you need to look elsewhere in the signal chain

The other issue is how much power you're driving them with? Limited power with typical low frequency roll off of a valve head means woofer excursion and thermal rating is often less of a concern than solid state - especially with such a large cone area. Gives you more options

From memory there are or were some Celestion neo drivers with very suitable specs, in their green label range for bass guitar. Finding them at a good price may be an issue.

[quote name='Beer of the Bass' timestamp='1399754309' post='2447404'] Well, drifting off-topic, I liked playing through your BB2/Gen 2 Compact combination at the gig last night! It seems like the BB2 is really clear and even in the upper mids/treble region - it's all there without giving the impression of having gaps or peaks in the response. Also, with just a small tweak of the Markbass VLE knob, I was happy with the sound of my fuzz, which is rare for a tweetered cab. Although I don't know how you had the attenuator set - maybe it was switched off? [/quote] Looks like a Faital tweeter/horn combo in those cabs, and if I'm right about which model is probably the best ever put into a commercial bass cab, and significantly better than a lot of PA cabs too until you get to the middle of the market. I'd hope the implementation is good as well - Alex's claimed off-axis response suggests it is. Most bass cabs with tweeters have nasty peaks around the roll-on frequency (accompanied by distortion) so you get a harsh upper-mid spike, often preceded by a dip. This gets worse if there's a woofer with badly damped break-up spike, e.g. most Eminence. A crossover with enough components to deal with that and give a smooth transition to the tweeter is very expensive! The better ones will have an ok tweeter, and avoid significant peaks around tweeter resonance, so fine for bass in many applications - but put voice through them and compare to a proper, 'real' professional PA cab, you will hear the deficiencies. To give an idea of relative cost, the PA cabs I am just finishing off at the moment are costing me over £100 in tweeter/horn components, and over £50 in crossover components, [i]per cab[/i]! And that design is a compromise on cost grounds...

Making it a little longer will initially put the wood under tension, which will act to further stiffen the panel, but after a while the tension element will be lost so it has no benefit over a brace that's exactly the right length - unless the brace is long enough to put a significant curve into the panel in which case there is a geometric stiffening effect (like an arch) but this is separate to the tension/stress element. Regarding brace orientation, from previous posts BFM and I think Phil favour the dowel approach but I'm not convinced it's sufficient on a thin-walled full-range cabinet because there will be multiple vibrational modes where the brace sits at a null, or where opposing panel attachment points are vibrating in phase, cases where sufficiently stiff axial braces ought to be more effective. But it'll be interesting to see in practice what effect different schemes have, I suspect outcome is going to be very material- and application-dependent.

I'm assuming that what's referred to as tension bracing means just that, panels are placed under tension which has the effect of greatly increasing stiffness, like a strung bow. But wood gradually loses tension like this over time (hence why bows are stored unstrung).

The point with unbraced 12mm is to get unacceptable results and see what needs to be done to get them acceptable, if that makes sense. Tension bracing is a flawed concept with wood because of viscoelastic creep - it won't keep the tension over extended time periods

Markbass f1 is essentially flat and clean output, secondhand these are quite cheap. It's not going to get much smaller than that even if you leave out the pre section, so all I'd care about was that the amp didn't colour the sound.

[quote name='Beer of the Bass' timestamp='1396448797' post='2413784'] Could it be the valve power amp being affected by the impedance curve of a ported cab (which increases either side of the porting frequency) when driven hard? I've heard of this as a potential issue with valve amps and modern cabs, but have no idea what it would sound like. [/quote] Aye, that's exactly what I was wondering

[quote name='mcnach' timestamp='1396443507' post='2413680'] what? [/quote] Hmm, impedance issues? But it could be (without hearing it) an issue with using a compression driver crossed lower than usual for a bass cab, I'd assume they're crossed around 2-2.5k in the BF. Distortion through compression drivers can sound a bit nasty, especially at the bottom of their range. Cone speakers are often more forgiving, subjectively speaking

Think I've said before that a twin 12" cab with that much power is probably overkill for 90% of users. Given how much Barefaced promote carefully-designed directivity as a feature then it ought to be clearly audible up close, maybe those Faital tractrix horns are not so good for this application. One thing, if it truly is a 'hifi' cab then I guess a relative lack of cone distortion could cause issues for some. I've noticed psychoacoustic placement of vocal monitors is often easier when they're a bit sh*ttier, the better ones can just envelope you with sound but still not be as easy to place. Most bass cabs produce a fair amount of distortion in the mid/upper mid range, this can be a useful part of the sound.

Gotoh Resolite GB640? It's the 'other' Fender footprint shape though.

[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?

Great result - glad it worked out! Previous incarnations of these Markbass units were the first compact combos I heard that just blew me away in terms of the sound... time has moved on but I still rate those highly. Curious about the drivers in them if they're not B&C any more, especially as B&C produced some lower-cost steel basket woofers a couple of years ago that looked like they were designed for bass guitar. I know Marco has said on the other thread that the T/S specs are the same, but there's a lot more to a good driver than that. Still, if it sounds good then it is good...

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.

My Markbass records fine from DI also. Plus, any hiss that's still apparent through the speaker with the master volume down is not happening in the main preamp section (ie it is happening post-DI). Not familiar with the interface but would using an instrument-level input not add stacks of extra gain?

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

I'd have the tweeter out, take it out of circuit and check the resistance across the terminals with a multimeter. If it's dead then you'll need a new diaphragm or replacement tweeter unit. If it's not I'd check the continuity of the wiring and then move to the high pass side of the crossover, and/or attenuator.

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

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