LawrenceH

Haha Stevie beat me to it!

[quote name='leosep' timestamp='1391789837' post='2361359'] any way to make them work? acceptable? i use an SX 4-strings presicion bass. [/quote] Haven't modelled them but all these drivers have claimed T/S parameters that are 'normal' for drivers usually bass guitar (although Fs of each is a little on the low side so may lose midbass efficiency but gain lower down) with respectable excursion capability. Can't see frequency response charts but the quoted -3dB values are fairly typical. However they are very cheap drivers, so if they work well in practice compared to 'well-known brands' then they represent a bargain. That's quite a big if! I would not be surprised if the production units showed a fair bit of variability from one to another, and the midrange response might be fairly ragged. Worth a go especially if you build with a pvc pipe port, that you can easily change the length of to suit tuning to an alternative driver if necessary.

[quote name='tm486' timestamp='1391766208' post='2360979'] Is there any risk with this? Will disconnecting the tweeter have any real effect on the impedance of the cab? [/quote] No, it will be fine. But you still have two different drivers sharing the same airspace, and the specs are not similar enough for you to get away with this without it causing issues regardless of the rattle. I would not want to run this cab at high power because you risk irreversibly damaging one or both drivers. In terms of important specs (your earlier question), I'd say Fs, Qts and Vas would all need to be close. You probably need to buy a matching OEM driver, or if the specs model ok in that box then a matching Celestion. If neither option is viable then either get a pair of drivers that do suit the cab, or just ditch the cab. Of course, if you can sort the rattle out and like the sound you're getting, you could just carry on as it is but expecting that it may or may not break at some point, and is definitely less reliable than a properly suited matched driver pair Even then there would still be the concern of the overall cab impedance dropping to a lower minimum, which is possible, and could make your amp unhappy. Also bear in mind the crossover even if functional, may be altered by the changed impedance curve.

Incidentally, that same issue of port flow means designing a compact box around the high excursion 8 and 10" drivers is difficult, if you want to make use of their full capability. You struggle to fit a long enough port in the box! Long ports are not without problems of their own either beyond mere size

[quote name='Musky' timestamp='1391723201' post='2360711'] That's a little odd as bass is perceived as more prominent as volume increases [/quote] Purely hypothetically, if port area were too small for the power levels being used then a relative loss of bass as volume increases is exactly what you'd expect. Port compression should start to kick in as airflow resistance increases, before onset of more obviously objectionable chuffing. This is something we have talked about a lot and would like to address empirically with the prototype. Simulations and anecdotal reports on air speed suggest that with long throw woofers, port size is usually inadequate and this is as much or more of a limiting factor than xmax.

[quote name='redstriper' timestamp='1391703519' post='2360426'] With the knowledge of the iron law, it shouldn't be too difficult to design a small lightweight cab that goes very deep, whilst needing a lot of power to drive it. And yet very few manufacturers provide such a thing to my knowledge, probably due to low demand - most bassists (not me) want high efficiency and extended treble response. [/quote] Part of the problem is finding suitable drivers for a 1- or 2-way design; dedicated bass guitar drivers is already a very niche market. The lower efficiency 'true subwoofer' PA drivers are not designed to run above ~120Hz so you get fairly horrible midrange responses or at the least, a design where directivity narrows very quickly starting around a few hundred Hz thanks in part to the large diameter voicecoils employed. These in turn will cross to a midbass driver to deal with ~100-2/3k, which is what is used for many bass cab designs. Whereas for your application you would want a driver capable of running ~30-2500Hz and with decent off-axis presentation. The Acme driver appears to be based around a Kappalite frame, but presumably they have worked on the soft parts to eliminate a lot of the midrange spike from the LF design, likely at the further expense of mid-range efficiency.

Actually I'd probably favour a smooth roll-off above all else, because they are easiest to integrate in a mix in my experience. I like the sound of sealed cabs in this respect. So for a reflex cab, a lower tuning if it reduces the shoulder in the response curve or pushes it out of bandwidth. I don't like a shelf with a sudden drop below tuning. Tuning for power handling makes perfect sense though and is what I've done in the past. btw acme's own measurement data is not in total agreement with the bass gear magazine measurement - I'm not sure how the tests differed but one shows what is presumably baffle-step-mediated increase in midrange sensitivity while the other does not. I find these cabs' design philosophy interesting, and am curious as to how this approach would differ in subjective terms from a similarly low-tuned but more sensitive driver, suitably eq-ed to reduce the midrange response to comparable levels.

There's a big difference between a thin nitro-type lacquer and a typical polyester/polyurethane job that you get on most modern basses. The former dries slowly and progressively shrinks to an extremely thin finish. The latter is catalysed, extremely hard and usually has substantial thickness. If we're talking about the Yamaha BB414 in the OP's profile picture, then I'd imagine that's poly of some description and would be massively surprised if working up the grades to 600 took you back to the wood. Just go gently with wet finishing paper, applying only very slight pressure (let the paper do the work), stop to check regularly, and it'll work out. Jumping straight to 600 will just mean it takes you longer to fully remove the scratches. Arguably, doing it that way means you get less even a sand so actually increase your chance of cutting through. Halfords sell suitable finish paper by the way - not the greatest longevity but good enough for this task IME

I agree with Hamfist. If you try and sand out scratches caused by 120 paper with 350+ you'll be at it for days, only eventually having to sand to a depth you'd get to with coarser stuff anyway. Sanding works best going gradually up through the grades. Even 120 doesn't take off enough to noticeably alter the neck depth in a single pass, main worry would be repeated passes on a single spot so follow advice above and keep pressure light and even across the full surface. As to final sanding grade, I've found that to be material-dependent but typically 1500 or even 2000 for decent gloss, ideally followed by a rubbing compound. 600 should take you to a smooth matt. Don't worry, this is an easy fix! PS 120 IS considered fine in most non-specialist/non-finish applications.

I've used that 18sound tweeter/horn combo in some stage monitors. It is a decent unit especially for the money. Still, adds a kilo or more and another 40-odd quid with extra crossover components. Could always start without and add at a later date if its absence was felt. Jim did you carpet your poplar ply? I've tried both Italian and Chinese and found both to be very soft, making a durable painted finish problematic compared to birch or generic far eastern hardwood

Sensitivity is important...BUT... the single number quoted by manufacturers is next to meaningless without context. What matters is the sensitivity at a given frequency, no good buying a '99dB' speaker where the spec refers to the 500-2000Hz region and it drops like a stone below this, just where you need the most power anyway. Modelling programs will tell you more about the lower range sensitivity. Worth getting into if you're going to replace a cab driver. The other side is that higher sensitivity drivers tend to have shorter voice coils (and lower power handing), so have a lower maximum output level with respect to bass frequencies, despite an initial higher sensitivity. They run out of headroom with less watts. It's all a trade-off. Having said that, there should be plenty of 15" drivers that would meet your criteria. To choose one, you need to model them based on T/S parameters to see if they're suitable in your box, and it helps if you have an idea of your preferred tonal profile and how this relates to a plot of frequency response. There are other factors too, but these are the best places to start.

Basschatters. You seem to be forgetting - the bass amp with the lights is a Peavey. A PEAVEY! Look at the Peavey logo, for Chrissake! When have their aesthetics ever targeted any sector other than that in the USA which wears naff 80s mullets? It is for this reason that I could score an all-valve high plate voltage 1u rack preamp for less than 50 quid, whereas if it didn't say 'Peavey' on the front in hairdressing scissor font and have a stupid double X in the name it would have cost me about 400 quid

[quote name='ebenezer' timestamp='1390642471' post='2347774'] looking at the graph,it seems to me the delta 12lf is, for the price, a cracking driver! (a recommended replacement for aggie cab). All this begs the question are we expecting too much from the humble 12 inch driver? [/quote] That's the danger with modelling graphs, they tell you nothing about soumd quality. The delta LF variants are straightforward pressed-steel chassis mid-woofers with moderate extension. Not bad, but nothing special either. But there is truth in what you say about what to expect from a single 12" driver. Two mediocre 12" units will very easily match or exceed what a very expensive one will do alone in terms of output capability, and it becomes a question of what your threshold for required peformance levels is- hence the 120dB approx goal for a single cab.

A 108 (or perhaps two) will hopefully appear at some point. I have already built a pair of 110s, loosely documented on basschat somewhere, that might represent a suitable basis for a 110 cab design - however we would need to identify alternative drivers since the Celestions I used, although very good, have unfortunately become prohibitively expensive. Those who read or commented in the 'Ideal Cab' thread, those comments were taken on board - but note that the initial prototype will be focused on getting the basic design elements right. A lot of the requirements people had were to do with ergonomics which, although important, can often be incorporated with relatively minor adaptations at a later point at the cost of increasing complexity or budget. My feeling so far is that Phil, Stevie and I each come at this from slightly different angles, though they may well disagree? But my assessment is that Phil has pushed for a cab that prioritises as straightforward as possible construction and very solid performance on a budget, making the design as accessible as possible. Stevie (at least in his own designs) probably prioritises absolute sound quality above all else, using very nice drivers indeed. As for me I like to maximise portability, which, if it's not to significantly compromise sound quality, increases build complexity and often cost. We also each have slightly different tool sets. I understand Phil has a fairly good workshop for prototype construction and has a lot of experience as a joiner. Stevie has a decent testing rig and a range of commercial software that will allow us to test drivers, model, and (importantly) subsequently assess the cabinet. Meanwhile I have much cheaper measurement hardware and have used free software for my own designs, which may be of interest to those basschatters who would like to do their own thing without such a significant initial outlay. In particular, when it comes to a 2-way design, I have not seen any documentation of the crossover design process on basschat, which might well be of interest to other DIYers.

[quote name='Ed_S' timestamp='1390136931' post='2341773'] Hopefully just an oversight that'll be corrected. I'll only be really annoyed if it turns out to be a stopgap to cover a lack of neo speakers, and I end up being the owner of "one of those heavy ones from the end of 2013 production run". I was actually also considering trading a few bits in for a CMD-121P to simplify smaller gigs, but now I think I'll wait and see how this plays out. [/quote] Have it apart (carefully) and have a look at the woofer, post up a pic - plus, if you can see any bare plywood you can easily tell if it's poplar or not

Older markbass cabs were made using Italian poplar ply which is pretty much the lightest available - it was suggested on another thread that this is no longer the case

Dispersion is something I consider very important for gigs in smaller spaces, especially where the bass rig is covering both the stage and the audience. Any two-way designs in particular will bear this in mind. For single-woofer one- and two-way cabs used alone on the floor, the need for increased but controlled vertical dispersion changes design approach. Who needs to hear the bass rig, and where are they in relation to it? There is the issue of build complexity, and angled cabs add to this. I think initially we all want something that novice DIYers can have a go at, without it being too intimidating or requiring a big outlay on tools etc. But it may be possible to produce different variants once the basic design has been validated.

Thanks for the contributions everyone! Keep them coming. [quote name='discreet' timestamp='1389442187' post='2334152'] If you're going to work hard and designing, building and promoting the 'ideal' bass cab, won't you be exposing yourself to massive amounts of flak from fanboys, haters, losers, geeks, trolls, flamers, asreholes, fanboy haters, geek flamers, loser trolls, troll losers and... bass players? Edit: ...and flaming geek troll loser fanboy hater arsehole bass players..? [/quote] I think if we pretended it was going to be an 'ideal' cab that was all things to all people then yes absolutely! But what I hope we can achieve alongside the plans is a fairly up-front discussion of the design decisions and compromises. Ultimately it would be nice to present several variants depending on budget and particular priorities. But keeping it simple to start with as, at least initially, we will be working with drivers already in our possession. Already there are interesting issues being raised about low-end voicing. If people are talking about particular scenarios, it would also be useful to know what they'd be driving the cabs with.

[quote name='Beer of the Bass' timestamp='1389454141' post='2334345'] -Something genuinely tiny for small rooms, practicing or as a personal monitor would be very cool, like a high quality 1x8". I could certainly use something like that for double bass in my acoustic project. [/quote] Funny you should say that... watch this space!

As far as I'm aware Eminence don't do a 6" driver that's at all suitable for bass, certainly not in the same league as the expensive B&C models. Before you drop what would be a lot of money on some B&C drivers, it'd be worth checking that the OEM ones in your combo are actually the same as the ones available - those ones linked above are ceramics and relatively heavy. Does the minimark use those or something more akin to the neo versions here? http://www.bcspeakers.com/products/lf-driver-neo/6-5/6ndl38 They might even have a cheaper OEM-only model in which case it gets more complicated. A vertical 4x6 would be a nice rig but not a cheap way of getting to that sound level! Bear in mind also that Markbass seem to have updated the minimark to a 2x8 - might ultimately be a better way to go? From 6 to 8 inches is a lot more cone area. I'd also want to be sure that, if using a rack case, it was up to scratch as a speaker cab.

[quote name='Beer of the Bass' timestamp='1388585945' post='2323660'] I had one of the Eminence Kappa 15A in a cab, which I think is the same driver as the Orange uses. I wonder if you may have trouble finding a modern neo-driver cab with the same response, as the Kappa 15 is quite coloured sounding. It has a massive peak just below 2KHz then rolls off steeply above that, which makes it quite bright and aggressive sounding but in an old-fashioned lo-fi manner IMO. [/quote] Eminence Basslite C2515, has a very similarly horrendous response to the Kappa 15A! http://www.eminence.com/pdf/Basslite_C2515.pdf

[quote name='6v6' timestamp='1388341119' post='2320988'] If you're going to make a statement like that, it would be quite helpful if you qualified it by saying which drivers you do think are as good as it gets [/quote] I'm not sure this is the thread for this but I'd happily discuss it more over PM. As with the tools, there is a price differential with drivers between the US and the UK that makes the Eminence more attractive over there than they are here, in my opinion.

[quote name='mrtcat' timestamp='1388236155' post='2319756'] All ill add is that if you build a BFM cab properly and follow bill's eq advice properly you won't be disappointed. [/quote] Except I did all that and was. These simplexx designs will surely work as well as any other based around these drivers. However, I don't think these drivers are as good as it gets any more

[quote name='stevie' timestamp='1386852799' post='2305332'] To my knowledge, I've never criticised BF's designs. I think, BoB, you're getting me mixed up with Lawrence, who built some Jacks and was less than impressed. But I'm sure some people will be very happy with these new designs. [/quote] I have been critical but I've tried to be balanced - the Jacks I built were very good for a certain type of electric bass sound with excellent low-mid clarity, but unusable for PA IMO regardless of EQ, with piezo option at least. One thing worth bearing in mind when sizing up the BFM designs as a novice is that the build prices just don't translate to the UK, unfortunately (same applies to any DIY design). Especially true if buying tools - the cheap stuff you get here really is unusably awful, but in the US the equivalent price range seems to be much more acceptable quality and their pro stuff is less than half the price it is here. I had a lot of fun with demonically possessed circular saws, in particular...

[quote name='stevie' timestamp='1387487457' post='2312685'] I couldn't agree more! The 1-2kHz region is absolutely crucial to the sound of the bass guitar (as the recording experts will no doubt confirm). Yet when we play live, most bass cabs are unable to reproduce that area properly. I'm a great believer in having a separate midrange driver to take care of the upper mids. [/quote] Funnily enough I've just been tweaking exactly this region in a mix. But Ive flip-flopped on midrange drivers and now I think I favour two-way, only using nicer comp drivers that go adequately low not to leave a big dispersion hole. I actually like the 1-2kHz region from a nice 10 or 12" PA driver for bass. I've got several Celestion drivers and they all sound really good in this region IMO.