Oh no! Another lightweight speaker cabinet build...

[LawrenceH]

I have been intending to do this for ages, but up here in Edinburgh I don't have suitable tools or space. However I'm off to the parents' for Christmas so will finally get a chance to build these - a pair of ultra-portable 1x10" speaker cabinets to go with my nice and light Markbass F1 head. A lot of the basic design decisions have been made, but further input from the helpful people on here will be very gratefully received, particularly in relation to finish, internal acoustic lining and hardware.

(Disclaimer!) the design brief is fairly specific to my needs, and I'm hoping the end result will suit ME better than excellent commercial offerings from eg Barefaced and EAD on here. I'm in no way trying to rival their products as I have neither the knowledge nor resources!

Driver choice: Rather than follow the sensible herd and build a design based around Eminence drivers (despite having 4 deltalite II 10s kicking around!) I have gone for the Celestion NTR2520D which I picked up at the very reasonable new price of £160 for a pair. Am I mad, or just stupid?! Hopefully neither, since I've bought them already...but why?

- First, all else being equal I prefer two 1x10s to a single 1x12. There is a minor advantage in terms of single driver dispersion characteristics but far more importantly, although two together will weigh more than a single 1x12, quite often I won't need more than one - especially for rehearsals which I typically reach by bike! Plus at the light weight we're talking about, it's actually form factor that will make more of a difference to me and two smaller boxes are preferable.

- Second, performance. Based on spec a pair of the Celestions will at least equal the Eminence 3012HO in the low-end and in my specific set-up should slightly better it, since I'll get the full 500 watts out of the F1 running at 4 ohms versus 300 at 8 (and this still won't exceed thermal rating). In fact there is no real advantage for me to be gained by going to a 3012LF plus separate mid, which with the crossover would incur a significant weight and price penalty (though sound very smooth). The Celestions have a nominal Xmax of 4mm BUT as mentioned in other threads, this is based on the traditional conservative calculated method rather than measured. More importantly to me, Celestion have confirmed that Xmech is an impressive 13mm with suspension braking kicking in at 10mm (very audible farting-out). This compares favourably to other 10" drivers (Xmech on the Deltalite II 2510s is 8mm). In the absence of Klippel distortion measurements (which according to B&C are rather ambiguous anyway) I'm going with a practical Xmax of 6mm for my sims, using (Hc-Hg)/2 + Hg/4 as Alex suggests on his site. In any case it's a bass cab, not a hi-fi . The other main advantage to the Celestion is that it should give a rather more balanced frequency response, many of the Eminence drivers tend to have quite an extreme on-axis peak between 2 and 3k. This can give a nice voicing to a bass guitar but it depends what you're after and how it interacts with the pickup resonance peaks of a particular bass. I'd rather get the voicing from the choice of bass/pickups and EQ if necessary. The Celestions extend up to about 5k on-axis and lack that big spike. This is why I've chosen the 2520D over the 2520E, which trades upper-end sensitivity for a longer voicecoil (and hence greater Xmax). If I were to build with a tweeter I'd consider using a decent waveguide-mounted comp driver crossed low with steep filters, at 2k or so, and then I'd use the 2520Es, but for weight and cost I'm going for a 1-driver solution. A quick note, there are other 10" drivers out there from the likes of Ciare, Faital and B&C that look very capable but they are generally more expensive and significantly heavier, with the performance benefits irrelevant when powering them with a single 500 watt amp.

Cab size and tuning: I'm playing 4-string jazzes and always use standard tunings so I really don't care about performance below 42Hz (string thump aside). Cab tuning tends to be a trade-off in terms of mid-bass versus low bass volume and excursion. The lower you tune, the more excursion and less volume around that important first harmonic (80-100Hz), which on a jazz is typically stronger than the fundamental. In a small box as well, too low a tuning requires very long ports to get sufficient area. Playing around I've gone for ~35 litres tuned between 50 and 55 Hz. This models well with the Celestion and avoids that exaggerated hump around 100-120 that you typically see on small cabs that are designed to sound 'deep' at low volume, which I personally don't like. The size is a good balance between bass-response, portability and excursion capability giving ~55Hz @ -3dB and 42 @ -10dB. It's no fEarful but it should have some decent poke.

Construction: I've found a supplier for poplar ply at a better price than I've seen elsewhere, which might be useful to anyone else contemplating a build [url="http://www.timberdepots.com/index.php"]http://www.timberdepots.com/index.php[/url] For some reason I was actually charged less than list by the very helpful guy in the Saltash branch, and 2 full sheets of their quality 12mm poplar are now sitting in my dad's garage which should cover a few more builds after this! To save the good stuff I will probably build a prototype using nasty B&Q ply. This'll be good to test bracing schemes if nothing else! I want to use a shelf port to take advantage of the extra bracing, and benefit from the reduced length typically required compared to tube ports, but it does make calculating the length required a bit more complicated. I'm also currently thinking I'll go against convention and convenience and mount the driver from behind the baffle. Not without disadvantages but I have my reasons...

Finishing and hardware: This is where I'm most unsure. I've used a UK-sourced Duratex-alike substance before and been less than impressed, perhaps there's a knack to applying it. I got a quote from a local company that spray polyurea for lining horse boxes etc (line-x type stuff) but for just two boxes as a one-off they'd charge £100 (it gets much cheaper for more cabs) and from what I understand the added weight is actually quite significant. I think this is probably the finish David Perry uses for his EAD cabs and it's incredibly tough stuff, but I'm not sure I want to spend that much only to add nearly a kilo to each cab. Currently I'm wondering about carpet or vinyl for either a retro look or something a bit more 'unique'. I'd also like to incorporate a tilt function and am undecided as to the best way of implementing this, but more on that closer to the time. Finally, I'm not sure on grille material. High void % aluminium is probably the best option for weight v strength but I can't find a UK supplier.

Edited November 27, 2011 by LawrenceH

[LawrenceH]

This is going to be a bit of a slow build thread, since I can't get started til Christmas, but here are some box sims from WinISD comparing the performance of a pair of NTR10s (blue) to a pair of Deltalite 10s and a single 3012HO or 3012LF all in the same overall box volume, tuned to 52Hz. Note that excursion charts are plotted for 500 watts input which the 8 ohm single drivers wouldn't see and it exceeds their thermal limits in any case. Similarly max spl chart ignores the fact that I couldn't put more than 300w into the 12" drivers with my F1.
[attachment=94046:maxspl.JPG] [attachment=94047:cone-ex.JPG] [attachment=94048:transferfunc.JPG]

Edited November 27, 2011 by LawrenceH

[soopercrip]

This is a link to alocal Hull based aluminium supplier I used to trade with. [url="http://www.eltheringtongroup.co.uk/"]http://www.eltheringtongroup.co.uk/[/url]
Dont know if they stock the punched grille stuff your looking for, but they have always been helpful and might point you where to go.
These are another local ali company but never used them, again they might know a source.
[url="http://www.aalco.co.uk/"]http://www.aalco.co.uk/[/url]

Andy

[LawrenceH]

[quote name='soopercrip' timestamp='1322422803' post='1450720']
This is a link to alocal Hull based aluminium supplier I used to trade with. [url="http://www.eltheringtongroup.co.uk/"]http://www.eltheringtongroup.co.uk/[/url]
Dont know if they stock the punched grille stuff your looking for, but they have always been helpful and might point you where to go.
These are another local ali company but never used them, again they might know a source.
[url="http://www.aalco.co.uk/"]http://www.aalco.co.uk/[/url]
[/quote]

Cheers Andy, much appreciated! I will check these options out

[JTUK]

Like to see the finished article

[soopercrip]

[quote name='JTUK' timestamp='1323564462' post='1464660']
Like to see the finished article
[/quote]

Me too

Andy

[LawrenceH]

Cheapy rubbish 12mm ply for prototype has been bought...don't have a router so advice on a blade for a powered jig-saw for cutting the baffle hole greatly appreciated! Have had problems in the past with the blade deflecting as you go round. Currently thinking about drilling at multiple points just inside the circle, joining these up then finishing off with a rasp. any alternative suggestions/general advice welcomed.

[soopercrip]

Drill your holes, use one of these [url="http://www.ebay.co.uk/itm/Silverline-Keyhole-Saw-310Mm-7Tpi-/280721884956?pt=UK_Hand_Tools_Equipment&hash=item415c54071c"]http://www.ebay.co.uk/itm/Silverline-Keyhole-Saw-310Mm-7Tpi-/280721884956?pt=UK_Hand_Tools_Equipment&hash=item415c54071c[/url] and finish with a half round file

Andy

[Phil Starr]

Hi Lawrence, you've probably cut your speaker holes by now but if you are stuck with using a jigsaw then you need a blade which is ground so the teeth are wider than the rest of the blade rather than a cheapy where the teeth are just offset. T101B is good or a T101BR which cuts on the down stroke. If you have to cut smaller than 10" holes then you would be better with a T101A0. Set the blade speed fairly slow and take your time.

Use a new blade, I find old ones wear more on one side than the other and they wander off true as a result.

Interesting you have chosen a PA driver for bass with an essentially flat response. I have done the same and I'm not sure of the results. Having true bass is interesting in a gigging situation as room acoustics become quite important. I almost always end up rolling off the bass, sometimes quite a lot. The relative absence of peaks in the 2-3k range means that the cabs lack character a bit. The speakers do what it says on the tin but I wondered if I might have preferred some of the 'inaccuracies' of the Eminences and the made for bass Celestions to the clean sound I have. It's all down to taste and I'm looking forwards to seeing what you think.

Edited December 19, 2011 by Phil Starr

[EdwardHimself]

[quote name='soopercrip' timestamp='1322422803' post='1450720']
This is a link to alocal Hull based aluminium supplier I used to trade with. [url="http://www.eltheringtongroup.co.uk/"]http://www.eltheringtongroup.co.uk/[/url]
Dont know if they stock the punched grille stuff your looking for, but they have always been helpful and might point you where to go.
These are another local ali company but never used them, again they might know a source.
[url="http://www.aalco.co.uk/"]http://www.aalco.co.uk/[/url]

Andy
[/quote]

sorry I don't have anything to add to this thread, but HULL!!!!!

[LawrenceH]

[quote name='Phil Starr' timestamp='1324300026' post='1472684']
Hi Lawrence, you've probably cut your speaker holes by now
[/quote]

Not at all, thanks very much for the tips! Head down to Devon on Weds and will get going once Christmas is out of the way.

Regarding the flattish response, yes that was deliberate based on the fact that I use passive jazzes which themselves tend to have pickup resonance peaks around the same frequencies as a lot of these drivers. I like the sound of the basses (and further tweak them based on how they sound) through semi-decent headphones. My aim is to have a solid tone but one where the 'cabinet' sound isn't dominant, so switching basses will result in a more useful tonal change. As an example, rather than use the speaker for that peak I could switch the pots on, say my jazz with Model Js (internal parallel wiring) from 250 to 500k and the Hi Z resonance peak will increase in magnitude but I won't be stuck with it for my other basses. I really want these cabs to function as acceptable 'all-rounders'.

In terms of low(ish) bass, I think there is leeway in the design to tweak the tuning slightly higher to firm up the response around 100Hz (which at the mo is a couple of dB down) at the expense of lower down, I'll see how I get on. For comparison I can very easily change to an Eminence Deltalite in this cab which will do roughly the same thing as well as add that peak.

What I think is notable is that multi-driver cabs without horns will typically roll off in that 1-2k-plus region anyway due to reduced coupling once driver spacing gets significant v wavelength. Looking at online graphs of an Ampeg fridge and a fair number of 'classic' cabs, they all peak in the mid-bass/low mids as you'd expect. If I was building a pair of 2x10s to use together I'd likely choose a driver with more of a rising upper-mid response at the expense of low-mids to counter this, for a similar overall voicing.

[soopercrip]

[quote name='EdwardHimself' timestamp='1324318723' post='1472989']
sorry I don't have anything to add to this thread, but HULL!!!!!
[/quote]
There are worse places Eddie, not many, but there are

Andy

[LawrenceH]

[quote name='EdwardHimself' timestamp='1324318723' post='1472989']
sorry I don't have anything to add to this thread, but HULL!!!!!
[/quote]

I don't know, they've got The Deep, and, err, um...
...do aluminium suppliers count as 'attractions'?

[Dood]

I'm interested in this thread as you have chosen Celestions speakers - There doesn't seem to be many DIY builds favouring these. The Eminence speakers you mention are getting lots of love - I feel sure Celestion must be doing something equal in spec? - I'm also interested as Celestion the company aren't a million miles from where I live.

I look forward to seeing how things turn out!

[LawrenceH]

Woo! Finally am getting going on this. Have cut the panels for a prototype from cheap nasty ply, using a circular saw which seems to wander a little so tolerances are less than fantastic to put it mildly. Two cheapy B&Q saws were tried and rejected because the bases were too flimsy and bent pretty much as soon as they were used in anger, this is their third cheapest, not great but will do. Anyway, right angles are for losers. Just off to look for a jigsaw blade as recommended by Phil now, apparently they've got them in stock locally.

[quote name='dood' timestamp='1324582636' post='1476007']
I'm interested in this thread as you have chosen Celestions speakers - There doesn't seem to be many DIY builds favouring these.
[/quote]

I think that's as much to do with the relative dominance of US-based builders on the forums as anything else, the Eminence have represented amazing value for money over there it just doesn't make sense to try anything else. Unfortunately though these Celestions are coming in so expensive even here now with the neo price hike. There's still a few available at old prices (cheaper than you can get a deltalite) but not for long I shouldn't think. Lightweight drivers are becoming a truly premium item again sadly.

[Phil Starr]

Hi Lawrence, don't know which bit of Devon your folks live in but if it is near Chard I'm happy to cut a few panels on the bench saw.

[LawrenceH]

Phil, that is a fab offer thanks! Basschat is awesome. Prototype is all cut and glued now, but for the poplar I'll think about the options and may possibly take you up on it (if I get that far before I have to head home again). Am in Newton Abbot so Chard is do-able. My dad and I have built a few cabs in the past but usually got the cutting done on his trading estate and/or used mdf which was much easier to work with, hideous allergic responses notwithstanding. I don't think it helped that the ply we used cost £6.19 per sheet from Trago Mills...as you're in the Westcountry I'm sure that'll give you a fair idea of the quality we're dealing with
I will put up a couple of build pics if I can for the comedy value.

[LawrenceH]

Some pics, prepare to recoil in horror at this cruel parody of woodwork...however the dimensions are within a couple of mm and it'll be more or less airtight apart from the port.

The empty box, waiting for glue to dry. I've used some standard wood glue, alongside that horrible (but useful) sticky expanding PU stuff that BFM recommends for the more dubious cuts and the bracing. The shelf port is designed to slide out for trimming/replacement if necessary since I don't trust the box sims for accurate length calculations.
[attachment=95969:DSC00955.JPG]

Bracing from offcuts, I may add to this, every addition makes a very noticeable difference to panel resonance based on tapping. I've got a lovely C major triad going between the side and two of the top spans currently (perhaps not so ideal!) The unbraced panels rang like a xylophone. Also, I definitely need more practice cutting these baffle holes. Oh how the American DIY builders must laugh, with their enormous 'shops equipped with routers, table saws, belt sanders etc etc.
[attachment=95970:DSC00959.JPG]

Would you like a little plywood to go with your big airy voids, sir? Actually not as bad as some visible in those braces! Somehow though, despite all the air this cheap ply is quite heavy.
[attachment=95971:DSC00960.JPG]

Recycling! There are quite a few bits like this...PU glue is good for cheapskate panel bodging.
[attachment=95972:DSC00961.JPG]

[EdwardHimself]

[quote name='LawrenceH' timestamp='1324374870' post='1473437']
I don't know, they've got The Deep, and, err, um...
...do aluminium suppliers count as 'attractions'?
[/quote]

It depends how attracted you are to aluminium, which is probably not very much seeing as aluminium isn't magnetic...

[LawrenceH]

Unfortunately the weather has stopped me properly testing this, so alas no freq responses/waterfalls, but I've managed to check the box resonance and play some bass/recorded music through it at reasonably decent volume. Shelf port makes the tuning frequency a bit sketchy but it has come out at 58 Hz, so not quite the figure of 55 I'd decided on but perfectly acceptable, reinforcing the upper bass but not giving that dreaded, boomy 'hump'.
For testing purposes I used a mixer/DI into QSC PLX2402, a 'proper' PA amp. Incidentally this would make a fabulous amp for a truly high-powered rig that was still light enough for an easy load.
Recorded music sounds solid enough, no tweeter means my perception is dominated by the lack of shimmery high end on full range material but it extends high enough for my purposes (much more than a 12" Ashdown blueline, for example) and it is definitely a lot less 'honky' than a Deltalite, sounds quite neutral. The bass is not dominant, there isn't any boom, but it is there and authoritative when the overall volume is turned up - I'd describe it as tight and punchy which subjectively matches with what the model would suggest. Bass guitar on recorded tracks sounded very good to my ears. I tried the cab both unlined and lined, using 1 to 2 inches of Monacor wool/poly wadding throughout except around the port. Testing this on vocal tracks, it surprised me how minor the difference was. I think this may be a combination of the braces and rough ply acting to make the inside a bit less regular, and the wadding not absorbing much below 1k. I suspect that lack of tweeter made a difference as well, I have found before that imperfections are a lot more obvious when you have full-range signal.
On bass guitar it sounded very good. I was using a battered but good 80s Jap Fender jazz, and the growly loveliness of the tone came across well without over-emphasis of any part. I can imagine for some gigs, EQ-ing to replicate the tone of more typical bass speakers would indeed be useful as Phil suggested, but I think it will do well set flat for most of the time. Again, a nice tight sound. No boom, and at low volume this suggests real bass might be under-represented, but turning it up to (loud) rehearsal volume gives a (IMO) very well-balanced sound and just emphasises the importance of Fletcher-Munson curves when auditioning loudspeakers for gigging. A relatively brief burst of real power to get the cones moving by a good cm or more peak-peak was very impressive, and suggests that from the performance perspective this cab will easily manage what I want. Bass end didn't seem to be struggling either from fart-out or chuffing.

Weight of the prototype is ~7.75kg, quite heavy really (eg half a kilo more than the Genz Shuttle even without hardware, though that's a 12l smaller cab). I hope to lose a fair bit of this with the poplar.

Disappointingly several things got in the way that slowed me down and I'm back to Edinburgh tomorrow, so I won't get to the 'real' cabs this time. But I'm hoping to have the ply machine-cut for accuracy and progress further in the near-ish future. User 'Discreet' on here has given me some very helpful advice and suggestions for finishing. Obviously the prototype was a rough bodge with no aesthetic considerations at all but for the real thing I will take much more care. One concern is the softness of poplar compared to birch, so I may yet go down the carpet route to avoid obvious dents. I know from previous cabs that Duratex-type paint won't protect it enough. The polyurea spray is still a possibility. Further suggestions of what to do and what to avoid welcomed. What are other people's preferences aesthetically?

[LawrenceH]

Right, so this has been a very boring build diary since other things got in the way, but finally I have nearly finished these cabs in case there is anyone out there who still cares! Afraid I didn't take pics all the way through. But.

Rebuilt the cab as a pair based on the prototype but tweaked the port length to drop the tuning slightly, bringing it pretty much to 55Hz as intended. I also abandoned the rear-mounted driver idea for these versions for finishing reasons, so lost a tiny amount of internal volume with the required extra 12mm recess but the acoustic difference this makes was fairly negligible in the real-world with a port length adjustment to maintain the tuning frequency. This time rather than a flat grill, the edges were folded over which adds a really worthwhile and noticeable extra rigidity. To prevent ringing I mounted it onto padded vinyl-covered wood in the corners and put a few extra blocks below the baffle to further deaden it and add more strength. It would be very hard to damage the driver by kicking now!

[attachment=108875:DSCF1494.JPG]

[LawrenceH]

So for a finish I decided the poplar ply really was too soft for any of the brush/spray versions, even rubber/polyurea-based, to be viable. I really wanted these cabs to be smart and 'professional' looking enough for functions gigs, and I feel people often judge these things on quite superficial aesthetics rather than performance (fair enough on here where you can't hear them anyway!) so felt the looks should match the material and driver quality employed. Tolex (vinyl fabric) is hard to beat on looks but people often complain it gets tatty quickly. I decided that some padding would both help protect the poplar or at least hide dents, and also protect a top layer of vinyl as the cushioning would help prevent it tearing due to catching on stuff. I would've liked to use closed cell polyolefin but gluing is a bit of an issue, especially to tolex, so for the time being I've used an open cell (polyurethane?) furniture trim. You can see the folded-edge grill here too. Definitely worth the extra effort.

[LawrenceH]

So next was addition of the vinyl itself. Rather than a loudspeaker tolex I went for a premium high-abrasion-resistance contract vinyl, designed for heavy-duty commercial upholstery. Decent grade PVC on a tight weave polycotton scrim. Drawback is it's more difficult to work with as it's thick and the backing is not the same colour so seams are difficult. I also decided that this look would suit a retro grillcloth so put some speaker cloth on the grill, glued on to help keep it looking tight and neat.
Here's a couple of pics of one very nearly finished cab, one thing I will change is to replace the panhead screws holding the corners with countersunk screws inside round-edged finishing washers so they're not liable to scratch anything they bash against.
[attachment=108880:DSCF1570.JPG][attachment=108879:DSCF1569 (2).JPG]

Edited May 28, 2012 by LawrenceH

[LawrenceH]

As you can see in the previous picture, the grill is held on by rubber feet. There's a reason for this rather odd arrangement apart from the fact that IMO it looks a bit cool and quirky in an oddly Scandinavian 1970s way. First I wanted maximum flexibility for stacking with these cabs, but also to use a really good comfy handle - which for me ruled out the recessed ones meaning whichever side it was on would not be stackable (the cabs were built with offset baffles in mirror image to minimise driver spacings whether stacking on long or short edges). Second, with the prototype I found that the easiest way of carrying a cab one-handed is with the longest edge horizontal against your body, and the shortest edge horizontal perpendicular to this. So both things pointed to putting the handle on the back. In this pic you can see this and also that I dealt with the vinyl seams by cutting a thin channel into the wood, overlapping the vinyl slightly at this point and holding it in with beading to give a smart finish:
[attachment=108881:DSCF1569.JPG]

This, with the nice leather handle, small overall size and light weight makes it exceptionally comfy to carry! Luckily given the expense, the poplar made a noticeable difference when comparing the final versions with the prototype.

Edited May 28, 2012 by LawrenceH

[LawrenceH]

So that's where I'm at. Things still to do include getting the finish washers on exposed screws and adding feet to an extra side if I want to stack on the shorter dimension. I'll try and arrange it so that the feet of the top cab when stacking sit with the screws/washers of the lower cabs inside them to stop and chance of slipping. Similarly it'd be good to add something to secure the F1, and a tilt function.

On the second cab I haven't got quite as far but I think that rather than screw the corners straight over the foam/vinyl I'll put in a nylon washer instead of the foam, 1mm thinner than the surrounding foam, so that it doesn't compress the vinyl quite so much on the corners but still holds it nice and tight.
I may also get round to making a vinyl cover to help protect the speaker grillcloth when transporting it, and am idly contemplating a logo of some sort.

How does this final version sound? Well, I've gigged them a couple of times as a (bare wood) pair and a (nearly) finished single cab and I really like it - clear, articulate and smooth. It doesn't boom and tweet and as a result, with the Markbass F1 on flat almost sounds bass-light because of the clear midrange, but this is deceptive. It gets pretty loud and deep when you want it! I'd love to try them with an SWR-type creamy valve preamp as I think they'd be awesome (I do wonder if the MB fusion could deliver this in a micro package). They were designed to give me a killer jazz bass sound in a tiny package and I really think they deliver. As a bonus if I wanted a more hyped up bass sound without EQing it in, then I could swap out the Celestions for the Eminence 2510ii as they'll also work well in this cab and give an instant scooped boombox 10" driver sound.