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Phil Starr

1x12" Cab Design Diary

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Right, one more question and then I'll try and shut up. Actually, two more...

Terminology point here perhaps about what "front" and "rear" mount means - I assume you're mounting the driver from the front of the cab, i.e. the driver will sit just proud of the baffle on the outside, but from what I can see the Beyma only has a sealing gasket on the front of the driver? Do you need some form of gasket on the rear to mount it?

Also, from the drawings it seems the baffle sits 30mm back from the front of the cab - is there a specific reason for that, as it seems quite a deep recess? I'd probably be thinking about leaving a smaller recess and then adjusting the port length to account for the additional volume if necessary.

So that's actually three questions, or four if you count the assumption...

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30mm, I haven't looked it up but the cone will travel something like 14mm, you'll want some sort of grille to protect the cone and that will need some clearance so the cone doesn't hit. Most grilles end up with dents or a sag, so make that generous then you'll probably want the cabinet sides extending beyond the grille to protect it, maybe another 10mm. 30mm is a minimum in a practical cab that is going to be chucked in the back of a van. IME It'd be better if you did want it less to simply reduce the depth of the sides which would make the cab slightly (probably insignificantly) easier to carry.

I mount all my speakers from the front, and simply run a gasket of draught proofing foam stuck to the baffle if there isn't a gasket on the speaker.

Edited by Phil Starr

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Having struggled to cut some holes with the cheapo hole-cutting device I recommended some pages ago (I notice that Beer of the Bass had the same problem - OK for a shallow cut but hopeless for more than that), I have been looking around for some proper hole saws. Unfortunately, they are really expensive.

As luck would have it, our friends at Aldi are currently selling a bimetal hole saw set for under a tenner. Not only that, but they are currently offering free delivery to launch their online services. As this kind of set normally retails at over £30 (check on the Screwfix site), it seems like a bit of a bargain - especially as it contains a 68mm saw that should be perfect for fitting drainpipe.

Have a look here: https://www.aldi.co.uk/hole-saw-set/p/093008008220200

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Confession, I bought mine from Lidl, if the Aldi one is the same then the arbor (bit in the middle) is standard and you'll be able to buy any number of cutters that fit, should you later need a different size. Good spot Stevie.

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My Aldi hole cutters have just arrived and they look really good. I'm not happy to be importing even more steel from China, but still......
Anyone who fancies a set will have to get down to their local Aldi (or order from the web site) as these offers only last for a week or so.

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Its a shame that its 12's you need as i would be ok with stripping out the 4 x 10" Beymas i use in my practice rig and sell them on. I could live without the stack, as my gig rig is Markbass / Carvin, and have an Ampeg combo that could take over practice duties

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[quote name='stevie' timestamp='1459505148' post='3017151']
Having struggled to cut some holes with the cheapo hole-cutting device I recommended some pages ago (I notice that Beer of the Bass had the same problem - OK for a shallow cut but hopeless for more than that), I have been looking around for some proper hole saws. Unfortunately, they are really expensive.

As luck would have it, our friends at Aldi are currently selling a bimetal hole saw set for under a tenner. Not only that, but they are currently offering free delivery to launch their online services. As this kind of set normally retails at over £30 (check on the Screwfix site), it seems like a bit of a bargain - especially as it contains a 68mm saw that should be perfect for fitting drainpipe.

Have a look here: [url="https://www.aldi.co.uk/hole-saw-set/p/093008008220200"]https://www.aldi.co....093008008220200[/url]
[/quote]

The cheap eBay fly-cutter was passable once sharpened and carefully adjusted (I didn't get it right first time), but these do look much better for only slightly more outlay.

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[quote name='Gottastopbuyinggear' timestamp='1459446387' post='3016720']
Also, from the drawings it seems the baffle sits 30mm back from the front of the cab - is there a specific reason for that, as it seems quite a deep recess? I'd probably be thinking about leaving a smaller recess and then adjusting the port length to account for the additional volume if necessary.

[/quote]

I recessed mine 25mm, but I would definitely not go for any less than that for the reasons Phil mentions.

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Thanks Phil and BotB, I hadn't thought about those points. Though I have to say as the potential seller of a couple of lightly used commercial cabs in the near future (based on the impending success of my basschat 1x12, of course) my gear is always placed carefully in the back of the van rather than chucked.

Aldi hole saws - how much?! The look of the cheapie ebay things that Stevie and BotB used scared the sh*t out of me so I bought a hole cutter from Wickes, but I'm ashamed to say how much it cost me. Let's just say my wallet feels violated. And that was just a single cutter.

Can I just take the opportunity to add yet another comment to a thread about what a great community Basschat can be at times, with people sharing their experience so freely and taking time to respond to numerous questions. Cheers all!

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Having thought about it I'm going to buy one of those hole saw sets from Aldi. But I'm a self confessed gear snob, so I'm planning to give them a light rubbing down with some 800 grit, and apply a few home made "Makita" decals.

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Lol. I dare say they are not state-of-the-art, but they are bimetal. And for the number of holes we are likely to cut, you probably don't need anything better. I haven't tried my Aldi hole cutters yet, but they do look very well made.

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I think we could probably speed the design of this box up if I had a Beyma driver. Phil and I had plans for a 12" + tweeter and a 12" + 6" midrange, which we should be able to do fairly quickly now that the weather is improving and I'm finalising my other projects. The fact that the only drivers available to us have been the ones out of Phil's PA cabs has slowed this project down tremendously. So, although I have too many drivers as it is, I'll have one if there is a group buy.

I must say, the take-up so far is a bit disappointing.

[Edit for missing apostrophe :rolleyes: ]

Edited by stevie

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[color=#282828][font=helvetica, arial, sans-serif]Annoyingly after we have done all this work Beyma have now upgraded and changed the SM212 Don't panic though, I've run the new driver through WinISD and frankly the changes are fairly minor and IMO an improvement. Basically they have made the cone slighly heavier, stiffened the suspension a little and maybe made some tweaks of the coil/magnet circuit. It means the frequency response is a little flatter and the speaker will work slightly better in a small box. With the proviso that all our tests were on the old driver I think it will work very well in our cab. Anyway on a quick look this is what they've done.[/font][/color]



[color=#282828][font=helvetica, arial, sans-serif]Xmax is now 8.25mm up from 7mm, that's entirely down to changing the way they calculate it. They used to use the most pessimistic way of calculating Xmax but now use the rather more optimistic methods used by Eminence and others. Either way it is very good for a driver at this price level.[/font][/color]
[color=#282828][font=helvetica, arial, sans-serif]Vd (total air shifted) is correspondingly increased but nothing has really changed apart from the calculations.[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]They've changed to a heavier cone which has changed the frequency response a little. The new speaker will give a slightly cleaner and more extended bass, but hardly noticeable unless you put them next to each other IMO. The thicker cone has damped out the 2kHz cone resonance that some of us have noticed in the prototypes. This is probably a good thing but I've got quite fond of the little brightness/slight roughness on some notes. Again this is probably a subtle improvement in the new driver.[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]The quoted frequency range in Beyma's specs has gone from 45-6000Hz in the old version to 45-4000 in the new driver, actually the frequency response curve is very similar so I don't think that you'd notice any loss of top end apart from the damped cone resonance at 2000Hz.. These figures are at a -10dB level but as the curve isn't flat it's not altogether clear what they are using as the base level. the old driver crosses the 90dB line at 6000 Hz and the new one at 5,500Hz.. There isn't really a loss of 2000Hz from the top end.[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]Not in the above, but to my mind more significant, is that with changes in the suspension and the cone plus some other tweaking Vas has come down to 103l which means this driver is happier in a smaller cab like the Basschat 12. The result is that the small bass peak of about 2dB in the original is down to 0.5db with the new driver and there's a tiny bit more low bass, perhaps 0.5db at bottom E. You won't notice that but you probably would notice the cleaner bass around 100Hz.[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]The heavier cone and slightly stiffer suspension also means the midrange efficiency is slightly down.[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]So, to be fair to Beyma I think what they have done is tweaked a bargain speaker slightly; which makes it more usable in a small cab like my design giving a slightly better (in the sense of flatter) frequency response with almost no penalty to the user. I can't see any reason to change the design at the moment.[/font][/color]

[color=#282828][font=helvetica, arial, sans-serif]In case you missed it there's a thread in the build diaries of someone who has built the 1x12 [/font][/color][url="http://basschat.co.uk/topic/282230-a-1x12-or-maybe-two/"]http://basschat.co.u...2-or-maybe-two/[/url]

[color=#282828][font=helvetica, arial, sans-serif]Blue Aran have the SM212 in stock for once [/font][/color][url="http://www.bluearan.co.uk/index.php?id=BMASM212"]http://www.bluearan....php?id=BMASM212[/url][color=#282828][font=helvetica, arial, sans-serif] [/font][/color]

Edited by Phil Starr

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I have just bought one of the new spec SM212 speakers. Phil has. Modelled a good response in a 30 litre box and also that is works well in a sealed box. I confirmed the results of Phil's modelling and have briefly tried out sealed and mis-tuned cabinets. The mistimed cab had a 4db peak at 120Hz and sounded surprisingly good. The sealed cab was good too but I missed the syrupy sound of the ported cab.

It is too early to be sure but it looks like a tiny cab can be produced with this driver. My table saw and jigsaw are at my daughter's house at the moment so I cannot build trial cabs at the moment. However if Stevie reads this, you can have the driver for 10-14 days for testing if you would like. PM me!

Edited by Chienmortbb

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PMs are being exchanged as I write. Phil is also going to let me have the prototype cab to work with. So maybe we'll see some developments on a Mk2 cabinet soon.

Incidentally, I don't think you're going to get the best out of the Beyma in a 30-liter cab.

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Do you have the cabinet dimensions and number/length of ports sorted yet? I only ask as I am keen to make a start on the cab. I have read the post from page one and my brain is now liquid.

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Check out post 554 in this thread. I'd advise you to make a removable front baffle, as there will be further developments at some time in the future that you might like to incorporate.

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Apologies yet again, life keeps getting in the way. There's some good drawings here which should help people build the cabs and a couple of people have already had a go and seem happy with the results. I really will get round to a decent step by step guide and [b]mikel[/b] if you want to start then I'm happy to talk you through any problems. Rather than make this thread any longer post up a thread in the build diaries and other people can follow your progress. The fee is to post a review of your speaker once it is finished :)

Good luck

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[quote name='Phil Starr' timestamp='1478369922' post='3168720']
Apologies yet again, life keeps getting in the way. There's some good drawings here which should help people build the cabs and a couple of people have already had a go and seem happy with the results. I really will get round to a decent step by step guide and [b]mikel[/b] if you want to start then I'm happy to talk you through any problems. Rather than make this thread any longer post up a thread in the build diaries and other people can follow your progress. The fee is to post a review of your speaker once it is finished :)

Good luck
[/quote]

Cheers Phil, and thanks for the mountain of work you have put into this. Respect.

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Stevie is right, the driver only arrived last week and we have yet to get the driver and cabinet together. For me there are two goals, two must into my car boot and they must be as light as possible. Of course having said that I realise that I need to measure my boot. I have just gone from a Freelander to a littl Suzuki and space is tight.

As Stevie says the revised driver still works well in the original design and if you need one soon, build that one. I suspect it will be some time before any revisions are done to the design, if there are any.

Finally thanks to Stevie and Phil. They have so much knowledge and they give us so much of their time.

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Stevie is right, the driver only arrived last week and we have yet to get the driver and cabinet together. For me there are two goals, two must into my car boot and they must be as light as possible. Of course having said that I realise that I need to measure my boot. I have just gone from a Freelander to a littl Suzuki and space is tight.

As Stevie says the revised driver still works well in the original design and if you need one soon, build that one. I suspect it will be some time before any revisions are done to the design, if there are any.

Finally thanks to Stevie and Phil. They have so much knowledge and they give us so much of their time.

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Hi everyone!

I finally grew the courage to start fooling around with winISD thanks to all the work here. I've been able to more or less repkicate the results obtained so far and looking at other speakers to compare I bumped into this one by Thomann: The box 12 280 A (I'm not able to paste right now, I'm on mobile). It seems better in the model than the W variant.

Cheap thing, about 50euros. Has a roll off on highs a bit sooner so I'd suppose a darker sound.

I'm considering giving it a try, just for the fun of it.

Or did I messed everything up with a beginner's mistake somewhere?

Cheers!

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No, it looks good value, the W variant has a bigger magnet and a roll surround and it's resonant frequency is consequently lower. I wouldn't use it without a horn and crossover though, it cuts off early and has some nasty breakup resonances. I couldn't find any t/s parameters though.

The A would be better for bass, the frequency response looks good and Xmax is excellent for a cheap speaker. The drawback is the smaller magnet which means damping (Qts) is quite high. I suspect in a practically sized cab it would have a significant hump in bass output around 100Hz. as many cheaper commercial bass speakers do.

If you struggle to model the cab yourself let me know and I'll have a look for you

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