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Boneless

2x12" DIY project

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Hi everyone,

I'm attempting to make a 2x12" cabinet. I know that it's probably cheaper to buy a commercial one second hand, that I may end up wasting money, etc. and I know it already, but I'd like to try and make a speaker by myself.

I was thinking at a 2x12" + midrange cabinet. I'd prefer a midrange over a tweeter due to my use (abuse? ) of distortion, and distortion through a tweeter just sounds harsh. Hence the midrange.

Anyway, I was considering these 12" drivers:

[url="http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=223"]18 Sound 12W500[/url]

I'd like not to use Eminence drivers. Just because :) I was considering Ciare, 18Sound, Beyma, RCF etc. but the only driver I found that seems to be really happy with LF reproduction is this one here.

Here is the WinISD Pro project:
[url="http://www.gospel.bo.it/albums/userp...d_2x12_wpr.zip"]http://www.gospel.bo.it/albums/userp...d_2x12_wpr.zip[/url]

Now, I am quite happy with frequency reproduction (F3 at about 60Hz, F10 at 41Hz, I am not after a bassy cabinet), the only problem though is the cone excursion. If I enter 350W as an input power (which I'd think is an adequate value) it seems that the excursion becomes way too high (see attached image).

I know that WinISD sets pink noise as input signal, so the cone excursion graph isn't exactly representative of reality, but still...

Could I actually get away with it? Keep in mind that I usually use 4 string basses, standard tuning. I rarely venture in drop D tuning. Keep in mind that I'm after a quite dry, open tone, with lots of zing and controlled bass (I was also thinking of opting for a sealed cab, but then I decided against it, since I'd like the chance of churning out big bass once in a while :D ).

As a final question, which midrange would you suggest? I was looking at some 6-inch drivers, but what power rating should I look at to be safe? I'd think about 150-200W RMS.

(Of course, you can criticize the design, even say it's complete crap, since I am a complete newbie :rolleyes: )

PS: Keep in mind that I am not after a hi-fi, even responsed supercab. I use sh*t gear, I'm gigging with an Eko MM-copy (just your average $150 Chinese bass, although I have installed an SMB4-A), I'm using a "crappy" Hartke VXL preamp feeding into a Little Mark... let's just say that I'd like to actually not hear the sound of my gear :lol:

Edited by Boneless

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Italians make the best drivers :) Your almost spoilt for choice. Assuming you can get those Italian made units for decent prices I'd go with them over Eminence to. Look at FaitalPro and B&C to altho they are both expensive.

4mm xmax isn't great tho so look out for a driver with a more, all the compaines you listed make ones. You haven't looked very hard if thats the only driver you found that is happy with low end. Plus if you dont need massive low end you should be able to get a very loud compact box.

As for a midrange looking at BA's choice of 6 or 6.5 inch drivers beyma seem to do the good ones, just make sure its got a high sensitivity so i'll keep up with the 12's.
[url="http://www.bluearan.co.uk/index.php?id=BMA605ND&browsemode=category"]http://www.bluearan.co.uk/index.php?id=BMA...semode=category[/url]

Finally if you do go ahead and make it with a correct X-over and with good components it will crush almost any commercial cab, plus building boxes is fun anyway.

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The thing is that I have dialed in the parameters for many 12" drivers (namely, from Ciare, B&C, RCF, other drivers from Eighteen Sound), but the ones with the right specs... are HUGELY powerful (700W RMS and going up), and since I'm after a twin 12"-driver cab, and seeing that I'm after low wattage after all (let's say about 500-600W at the most) the smaller drivers don't seem to be too happy with low bass :)

I've had a look at SICA speakers as well... there are some interesting drivers, but they're all with a low sensitivity rating. And they're medium-quality drivers mostly, while I'd like to choose some really nice drivers.

Staying among Italian brands, what would you suggest?

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Sure you know already but it doesn't mean they need 700W of amp power to work well. As I'm sure other will say power handling is one of the last specs to get hung up about.

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As for recomendations spend some time with winisd and model loads of drivers till you get something that suits you conditions. For bass cabs I'd usually look at Sensitivity and Xmax first.

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Yeah, but a 700-1000W driver costs much more than a 250-350W driver... that's my main concern, since I'm not going to drive the cab that much (I've only got a Little Mark, and I don't think I have ever used more than half its power :) ), big drivers would be wasted. And they would weigh more.

I'm also having a look at the "Bass Speakers" from SICA, but they're either inefficient on the lows or have ridiculous xmax (2mm, they would burst with only 100W RMS).

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I'd use 18sound, without a doubt. I wouldn't bother with two 12"s if you're using a midrange, one better 15" will match the output, weigh less, cost less and sound almost identical (because most of the tone character comes from the midrange driver). However crossover design for a such a cab will not be easy so unless you plan to spend an enormous amount of time and invest in a measurement rig then you'll need to use an active crossover. You'd be best served by choosing the 18sound 15" that has the most similar response and impedance curve to the 3015LF and then using the fEarful plans on talkbass including the various passive crossovers posted on there.

Generally the neo models have superior performance than the ferrite models due to being more recent designs.

Alex

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I'm not so sure about the midrange, that's the problem.
I don't have the means, nor the expertise to actually properly design a crossover and everything else. I was thinking of simply putting the midrange inside the box, without making a separate compartment, due to its sheer size compared to the driver, and installing a simple 1-way crossover and an attenuator or whatever to control it. I am not after fidelity, and I don't mind if the cab is somewhat voiced, just as long as it's got a good tone :) The midrange would serve as a "warmer" tweeter, I'm not a slapper, just a heavy picker and a distortion addict :lol:

If I'd had the idea of actually making a supercab ( :rolleyes: ) I'd have asked to buy a kit off you, Alex :D I understand that by making proper calculations, and designing really good crossovers, and so on, I'd end up with a superior cab (in terms of efficiency, frequency response and evenness), but alas, I have no idea of how to (properly) design a cab, I'm undergoing a crash course at the moment, and I know my first design will probably be mediocre to average, but it's just for the fun of doing it. And for gaining a bit of experience.

Edited by Boneless

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You can't put a midrange into a cab without a highpass filter or you'll release the magic smoke the first time you use it in anger. At the very worst get a stock crossover with an 800-1000Hz highpass point.

Alex

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Yeah, as I said, I'd filter the midrange* (I was thinking of that, really, a -12 or -24dB highpass filter with cutoff centered at around 700-1000Hz). But is the 18Sound I'm considering actually up to the job? I know that Xmax is just a mathematical value, and that, in reality, maximum excursion is actually a bit higher than that, but seeing the Maximum Power graph, I'd have 180W maximum between 50 and 100+Hz, is it actually reasonable? I can always compromise, if you tell me that I can actually easily get away with it, I'll stick with this idea.

* : BTW, what would an adequate power rating be for a midrange? Assuming I'm looking at high sensibility, I was thinking at something in the region of 100-150W RMS, is this OK?

Edited by Boneless

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OK, I have chosen the drivers and everything, here is a (very rough) blueprint made with MS Paint :)



And here is the project file for the 2 12"s (WinISD):

[url="http://www.gospel.bo.it/albums/userpics/10222/beyma_2xsm212_wpr.zip"]http://www.gospel.bo.it/albums/userpics/10...2xsm212_wpr.zip[/url]

I have planned a 122 litre cabinet for the two twelves, and a 5-6 litre sealed cabinet for the midrange. Adding driver volume, the sealed midrange section, and overestimating the end results for safety, I have ended with a 142 litre cabinet.

The cab won't probably be terribly loud, since the drivers aren't really very sensitive (96dB for the 12" drivers, 98dB for the midrange but the cabinet will probably have a final sensibility of 98-100dB, which isn't TOO bad, I suppose :rolleyes: I wasn't after loudness, actually, since I rarely pump up the volume. And this is only an experiment.

The best crossover for this project, probably, is a 4th order Linkwitz-Riley centered at 800Hz. By entering the data in WinISD, it shows a F3 point at 1000Hz, a -6dB at 800Hz, so it's probably not too bad. But I'm open to suggestions.

Now, the big dilemma: impedance. Is it going to be a 4 ohm cab, an 8 ohm cab, or a @#?!£ cab? All I want to know if impedance is going to be lower than 4 ohms. I can't have impedance lower than 4 ohms, since my Little Mark can't handle them. And I'd like it to be under 6 ohms at least for more power. This is the impedance graph for the two 12":



And this is the midrange driver:

[url="http://profesional.beyma.com/ingles/pdf/6MI90.pdf"]http://profesional.beyma.com/ingles/pdf/6MI90.pdf[/url]

Can you help me out here?

Edited by Boneless

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[quote name='Boneless' post='537333' date='Jul 10 2009, 05:08 PM']Now, the big dilemma: impedance. Is it going to be a 4 ohm cab, an 8 ohm cab, or a @#?!£ cab? All I want to know if impedance is going to be lower than 4 ohms. I can't have impedance lower than 4 ohms, since my Little Mark can't handle them. And I'd like it to be under 6 ohms at least for more power. This is the impedance graph for the two 12":

Edited by Protium

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Anyway, I actually made a mistake about the crossover. It's actually a 4th order Butterworth filter centered at 1000Hz.

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[quote name='Boneless' post='537596' date='Jul 10 2009, 11:02 PM']Anyway, I actually made a mistake about the crossover. It's actually a 4th order Butterworth filter centered at 1000Hz.[/quote]

This doesn't really matter because the driver impedances are not ideal to get a usable speaker configuration below 12ohms.

Personally I would look for 16ohm woofers or a 4ohm midrange or use a 2-way crossover.

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[quote name='Protium' post='537612' date='Jul 10 2009, 11:28 PM']This doesn't really matter because the driver impedances are not ideal to get a usable speaker configuration below 12ohms.

Personally I would look for 16ohm woofers or a 4ohm midrange or use a 2-way crossover.[/quote]

Hes already described the woofers and crossover hes planning to use and seems to know exactly what to use and where. His question is whether the impedance graph suggests the overall load will drop his amp below the minimum load, I think.

it looks like Boneless knows exactly what hes doing and is just worrying about the detail IMHO. Best to let him get on with it :)

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No, no, I actually DON'T know :)

It's just that I tried choosing an adequate driver, keeping in mind power, frequency range and cost, and these three are satisfied by this choice of drivers.

The point is now, impedance-wise, will I get a 4+ ohm cab? If I don't, I have to plan everything from scratch again... (f***! :rolleyes: )

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[quote name='Boneless' post='537667' date='Jul 11 2009, 01:01 AM']No, no, I actually DON'T know :rolleyes:

It's just that I tried choosing an adequate driver, keeping in mind power, frequency range and cost, and these three are satisfied by this choice of drivers.

The point is now, impedance-wise, will I get a 4+ ohm cab? If I don't, I have to plan everything from scratch again... (f***! :lol: )[/quote]

If you look at your impedance plot and think how much thermal power your amp will put out then it can be seen as a 4 ohm cab. I think :)

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[quote]This doesn't really matter because the driver impedances are not ideal to get a usable speaker configuration below 12ohms.

Personally I would look for 16ohm woofers or a 4ohm midrange or use a 2-way crossover.[/quote]

But generally the impedance of the cabinet is given by the woofers. If you have a 4x10" cabinet with a tweeter, the tweeter is generally overlooked since it shouldn't have any influence on the total impedance. I'm only substituting the tweeter with a midrange, so things shouldn't change :)

Edited by Boneless

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Boneless, you will struggle to do what you are attempting with the knowledge you have. I'd suggest that you keep it simple.

Build a 2x 12" cab first and forget about using a midrange unit for the time being. Align the drivers vertically. Go for a cabinet size between 80 and 100 litres. Build it from 15mm or 18mm birch ply. Brace well, particularly the back and between the drivers. The Beyma you have selected is pretty good (although it's not Italian, but never mind) but you would be better off with a neodymium speaker for a number of reasons. (In a few years time, nobody will want anything else). Beyma have a few really nice ones. Check them out. The 12MW/Nd and 112Nd/W both look good.

Maximize port area to reduce port noise. Minimum 2 x 4" ports or 4 x 3" ports, but more if possible. Or a slot port like this: [url="http://www.speakerplans.com/index.php?id=gsub"]http://www.speakerplans.com/index.php?id=gsub[/url]

Stage two would be to use the bottom driver to compensate for the baffle step. Finding out what this means will be part of your learning curve. Then, if you want to, build a compact top cab with a good midrange driver and bi-amp it using an inexpensive Behringer electronic crossover. I can assure you, this will be much cheaper in the long run than trying to design a passive crossover when you have never done it before. However, I expect you will probably be happy with the midrange sound of a good 12" speaker and may not even want to do this.

Good luck. By the way, your speaker will be 4 ohms.

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Thanks for the help.
Actually, the midrange is more aimed towards the upper mids and treble, in other words, a smoother tweeter. I'd actually rely on the woofers for true midrange (and, according to the charts, I should have plenty of it).
Anyway, I thought active crossovers worked BEFORE the power amp, not after it. For the crossover, I'd ask an electrical engineer, a friend of mine, who has already told me that he can give me some advice here and there. I might just disconnect the midrange for the time being for now, anyway. I'll install it, try it out, see if it works correctly (my head has built-in protection, so I'm really not bothered, if it doesn't work, it will just switch off). According to my calculations, impedance will only go below 4 ohms (at about 3 ohms) between 200 and 500Hz, and everyone has assured me that it's perfectly normal.

In regard to the woofers, I'd have preferred using Italian drivers for various reasons, but there simply wasn't a 12" driver in my price bracket (100-150€) that would satisfy my needs. Many people are very happy with Ciare, 18Sound, RCF, FaitalPro, etc. but they all seemed good for midbass applications (they simply didn't go down very low), while I was looking for a more fullrange speaker. SICA seemed to have some good choices, but they either had low power ratings or low Xmax. I'm OK with an European driver, though.

I chose the SM212 instead of the 12MWNd just because of price. I was actually leaning towards the latter, which seems to be a superior driver in everything, but then I didn't want to risk potentially wasting more money than I'd want. I agree though that neo drivers will probably be the standard in a few years. They are already starting to be, by the way, most of the big names have a neo line in their offerings.

I'm installing 4 3" ports in a 120 lt cabinet. According to the simulations, I should be really safe, considering that Xmax is reached at 400W (but in a simulation, which considers sinewaves) and port velocity is below 17 m/s over 38Hz at 400W.

Driver alignment isn't vertical just because I wanted to fit the both the woofers and the midrange in a compact box, while keeping a 60cm width which is standard - many heads are built according to this standard, I don't want heads larger than the box, and I want to keep my box in a vertical position. Many boxes have a similar alignment, so I guess it can't be too bad :) Plus, I want the midrange as close as possible to my ears.

Edited by Boneless

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[quote name='Boneless' post='540430' date='Jul 14 2009, 11:12 AM']Many boxes have a similar alignment, so I guess it can't be too bad[/quote]
Yes, it can be too bad. The basic design parameters of most commercial cabs are set forth by marketing departments, based upon what they think will sell, and that's almost always a matter of looking 'right'. But what's most pleasing to the eye is not what's most pleasing to the ear. The number one reason for building one's own cab is the ability to not have to settle for what some marketing department head who probably doesn't even play bass thinks will sell based on looks. Your reasoning for not doing vertical drivers is the same as theirs, and is intrinsically flawed.
[quote]I'd actually rely on the woofers for true midrange (and, according to the charts, I should have plenty of it)[/quote]The charts aren't worth squat, because they show axial response. whereas 30 degree and 45 degree off-axis is what counts.

Edited by Bill Fitzmaurice

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Yeah, but since I actually don't know WHY vertical alignment is better, I actually wouldn't know what the benefits are. I might rearrange the drivers, though, no problem in that of course.
But my aim is simply building something that works and that may be on par, at most, with most commercially available cabs. Not something BETTER. How could I? Commercial cabs, although they may be ill-designed from a technical point of view, still please most people, and I won't be able to actually do something better (those cabs are still designed by someone who probably knows what he's doing). In due time, I will start experimenting with different driver alignments, with proper crossover design, etc. but for now, I want to opt for a conventional design.

Then, I might build another cabinet with other specs and simply reuse the components from this cab, to understand the differences and benefits from a better cab design (even because my somewhat limited experience tells me that better designed isn't necessarily better sounding, if I get my tone from a cab with a huge hole in a certain frequency range, is it really a bad thing? Most people may actually be disappointed by a well-designed cab, just like many people are disappointed by true flat sound. That said, I understand why it's best to have the option to actually choose your own tone, instead of your gear forcing you one).

By the way, my next design will probably be a 12"/15" + midrange, but done "properly". I might even buy an electronic crossover to better judge crossover point by ear.

Edited by Boneless

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[quote name='Boneless' post='540513' date='Jul 14 2009, 12:28 PM']I actually don't know WHY vertical alignment is better[/quote]Which goes to why everyone who does know how speakers work in this and other forums have told you that you should not be trying to design your own cab. :)

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