LawrenceH

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

The vanderkleys are 600w aes each right? They should cope with the 1602 at least as well as the BF vintage, and might need it more too as they're probably a little lighter in the bass end.

-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.

I thought they were neo, based on a deltalite chassis? Could be wrong. If I'm not then the Deltalite 2510 is the off-the-shelf equivalent and might not be a terrible match for that isobaric cab, it does need a big box in normal circumstances. But it's quite possible Orange are using a custom variant. I'm afraid the deltalite is very expensive these days (and IMO not worth it)

Just looking through that talkbass thread, see it was a toss-up between the celestion and the deltalite. Fwiw I have both and despite what the thread implies, the Celestion is a better driver IMO. It will certainly drive a lot harder before running out of steam

Funnily enough that Celestion is the model I chose when building my own 110 cabs, as about the most suitable lightweight 10" driver on the market at the time for bass guitar. It has proven a very capable little driver, unfortunately retail price has pretty much doubled since I got them. There still aren't many 10"ers out there that are as suited to compact lightweight bass cabs IMO

95% of the clever stuff in a reflex cab designed for bass guitar is in the actual drive unit. Many of the compromises in the cabinets themselves are more-or-less duplicated between designs either for cost reasons, or because they have chosen common sonic priorities (eg increased midbass efficiency over 'true' bass, compact footprint, historically less worried about coloured midrange reproduction). PA driver design has probably led the way because that's the big market for improved high-power thermal/mechanical performance - as Luke says, once new drivers have come to market from the PA side, so the most suitable for bass guitar are then adopted in a range of designs. This seems especially true of the American designs since nearly all of them depend on Eminence as far as I can tell. Also consider that driver manufacturers like to use essentially the same magnet/voicecoil designs across multiple driver sizes. For a 2.5 to 3" coil the 10-15" range is sensible with 12" sitting nicely in the middle, so probably easiest to make work as a design with the usual cone/suspension materials. Another aspect is the shift in preferred voicings for bass guitar to include more mid/high content. The off-axis presentation of a 'typical' 12" driver compared to a typical 15" is improved in quite a critical range (1-2kHz), while modern improved drive unit excursion/handling and, importantly, higher power amps, mean the efficiency loss is more than compensated in comparison to older designs. [size=4]It's interesting that Eminence and Celestion are among the few driver manufacturers with dedicated ranges for bass guitar. Celestion in particular have taken an interesting approach with decidedly old-school thump-y, coloured voicings, analogous to the dedicated electric guitar drivers which would also be unsuitable for PA. I'd also say some of the Eminence 'PA' drivers are probably better suited to bass guitar than high-end PA![/size] One thing that I'll repeat from another thread...it is relatively easy and cheap to come up with a 212 cab that will cover most gig situations adequately and I believe many of the 'boutique' 212s to be overkill in terms of pure volume capability. It is far more difficult and expensive to get there with a 112 and still requires a pretty nice (ie expensive) driver, even with a 115.

[quote name='chrismuzz' timestamp='1392236238' post='2366382'] My old Markbass 104HF was poplar ply. It was solid as a rock, but did sound a bit boomy. Maybe that's why they changed to MDF? [/quote] I think it's more likely because MDF is much, much cheaper. Not a bad material per se but still needs bracing to control the lower order modes, and it does tend to weigh a ton as mentioned! I don't like it for gear that's meant to be portable. Studio monitors where weight doesn't matter, then it makes more sense.

[quote name='EddyGlee' timestamp='1392211882' post='2365975'] Ply requires much more bracing to achieve same rigidity. [/quote] This is wrong. MDF probably has a slight damping advantage, but decent ply is stiffer.

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.