LawrenceH

I still think the limits imposed by the shape of the LF transfer function on the bass end are being ignored, or at least not given much priority. The only practical way of making eg a Vanderkley sound like an Acme in the bass would be with DSP filtering, regardless of xmax/power limitations, because the EQ on even quite a flexible amp won't be able to sufficiently compensate for the difference in cabs to give a similar overall roll-off curve. This is another reason to think carefully about tuning in the 40Hz versus the 50Hz regions, since tuning lower can give a curve that is easier to EQ within the range you actually care about using the EQ controls found on a typical amp (eg 12dB/oct shelving filters for the bass).

Worth remembering that set points for filters are typically -3dB (or even -6). So even if you hear a difference with (say) an 80Hz filter, it's probably as much to do with the signal at 80Hz and up being attenuated rather than below this. Steeper filters allow you to cut lower but can be harder to integrate than shallow slopes, unless it's a true subsonic filter like those built into power amps.

Not familiar with that model of Laney and can't see the pic well enough to tell, but a lot of those mixer/amps are mono, if that's the case here then a 8 ohm plus 5.5ohm would drop you below the minimum and overheating would be a real possibility. If the amp is stereo then ignore this irrelevant contribution!

What they should do, right, is build the micro amp into the speaker cab itself. I'm a genius! Patent office here I come...

This 'hybrid resonator' description is as clear as mud. Puts me right off when a manufacturer goes all marketing-speak. If it's a low-tuned ported cab why not say it? Or if it's something else like a passive radiator then why not say that? Or if it is something like a hybrid port/ transmission line (ie a system where standing waves are not minimised) then say that, though that would be ironic given what I remember of Alex's previous contributions to threads on TL speakers for bass guitar. There is a bigger irony in the evolution of barefaced products back toward the higher qts-style midbass bump, since that was exactly the type of sound so roundly derided when BF first started. But it is a good sound

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.