DIY Speaker cab and experiment.

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Petebass
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Re: DIY Speaker cab and experiment.

Post by Petebass » 14 Mar 2010, 14:02

LimeB wrote:You could do a whole seperate ( or have you already ) on a guide for Non tech typres, to make the cross overs / notch filters and what they should do.
That's hard to do without writing a whole textbook. Of all the books I've read on speaker design, the crossover chapters are always the hardest, because each type of crossover has it's advantages and disadvantages.

As a general rule, the industry standard is for 2nd order filters (12dB per octave). That's fine, but the industry standard is also to incorporate a light bulb or some other sort of protections device because a fair whack of material still passes through a 2nd order filter. Higher order filters roll off a lot faster, and are therefore much better at offering protection for the tweet. They also sound better IMO. So I use 3rd Order filters (18dB per octave) or 4th order filters (24dB per octave).

Once you decide on what Order filter you'd like to use, there is a wealth of information and calculators available online to help calculate values for your components. I have a really good Excel spreadsheet that consists a gazillion crossover calcs AND wiring diagrams. I paid good money for it so I'm not going to share it around. But there's nothing it's can't do that isn't available online somewhere.
LimeB wrote:Any tips on squaring the peices when gluing and clamping them together ?
What sort of screws?
It's incredibly important that you cut your pieces square to start with. Take extra time measuring, and use a "Square" tool often.

And that "Square" tool was never far away when I was gluing the panels together either.
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
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Petebass
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Re: DIY Speaker cab and experiment.

Post by Petebass » 14 Mar 2010, 19:18

I had a family thing to go to today, so I only got a little bit done:-

First up I drive in the screws as needed to reinforce the joins. Then inserted the acoustic lining. Usually I attach these with staples, but staples won't work on the composite cab. so I used this as an opportunity to try something new and I glued them into place. I tried a couple of different things on test patches and found the best method was to use hot melt from the glue gun. That'll work on both cabs so I'm happy.

I only line 3 walls, as do a lot of commercial manufacturers. You might read that the internal lining does all sorts of wonderful and magical things to your tone but I've done the experiments in the past and it doesn't. It serves one purpose, a very important one - it stops standing waves from developing inside the cab. This can only happen at frequencies which are small enough to be fully formed within the confines of the cab. That means only highs and high-mids can form standing waves inside the cab, though in practice it's the high-mids that are most audible and need taming. This lining simply stops those frequencies from bouncing around inside the cab. By lining 3 walls, the frequencies can only bounce off one wall before it hits an acoustic lining and stops dead in it's tracks. Therefore standing waves cannot form.

Could I line al 6 walls? Yeah I guess so, but it makes no difference to the sound and this stuff costs $35 a square. It also takes up space inside the cab, thus reducing the all important internal volume. I would have had to account for that in determining the cab's dimensions.
Image

In finding an alternative to staples, it got me thinking about another part of the build in which I use staples. When I've attach the protective carpet in the past, I've used staples to hold the carpet in place, then removed them once the glue is dry. Again, that won't work on the composite cab, so i came up with something else. I built a "frame" for front baffle out of scrap ply. I'll then clamp these down to hold the carpet in place in this critical area. I'm likely to get some glue on to this "frame", an being wood it'll form an unwanted permanent bond. To prevent this, I wrapped the "frame" in packing tape. I'm confident this will work on both cabs too....
Image

The next step in preparing for carpet is to predict where the carpet joins will be, then spray it with matt black paint. This way if there's small gap in the carpet joins, the black paint will make it less noticeable. You'll notice it most in this pic on the cab corners.

I also painted the front baffle black as I don't intend to carpet it. I also had to paint the internal bracing and the walls which did not have foam lining because the woody colour made them clearly visible through the large port and I thought it needed to be camouflaged.
Image

Next step is carpet, but looking at my schedule for this week I'd say that won't happen until next weekend.
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

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thebman
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Re: DIY Speaker cab and experiment.

Post by thebman » 14 Mar 2010, 20:34

Looking good Petebass, and no doubt you'll soon be covered from head to toe in fiberglass resin and sleeping on the couch till the composite cab's finished. Can't weight for the comparison.
keep up the good work:)
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Re: DIY Speaker cab and experiment.

Post by mkat » 15 Mar 2010, 00:57

Petebass wrote:I've contemplated going with 9mm ply and bracing it, but I've never actually tried it. The only problem I can see is that the timber is now so thin that the screws I currently use would split it as they went in, even if I pre-drilled the holes.
Pete,

One way to do the bracing is to laminate the ends with ply to make them thicker. This way, you'd have no issues splitting the ply and you wouldn't have a significant increase in weight. So, you could go with 9mm ply, laminate the edges only to 18mm. For example, you could laminate a peice 40mm long (or whatever to give enough screw clearance) with the same width and thickness (or thinner) as the brace (ie. offcut).
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Petebass
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Re: DIY Speaker cab and experiment.

Post by Petebass » 15 Mar 2010, 05:15

mkat wrote:
Petebass wrote:I've contemplated going with 9mm ply and bracing it, but I've never actually tried it. The only problem I can see is that the timber is now so thin that the screws I currently use would split it as they went in, even if I pre-drilled the holes.
Pete,

One way to do the bracing is to laminate the ends with ply to make them thicker. This way, you'd have no issues splitting the ply and you wouldn't have a significant increase in weight. So, you could go with 9mm ply, laminate the edges only to 18mm. For example, you could laminate a peice 40mm long (or whatever to give enough screw clearance) with the same width and thickness (or thinner) as the brace (ie. offcut).
Not a bad idea. With that problem solved, the next one is to work out the distance between braces on a 9mm panel. From my experience a solid 12mm sheet (i.e no holes for speakers to weaken it) needs a brace approximately every 40cm. 9mm ply flexes a lot more than 12mm, so I suspect a 9mm sheet would need a brace every 15 to 20cm. So basically twice as much bracing is needed. So the question is arises as to whether or not the weight of twice as much bracing plus the laminates on the edges will cancel out the weight gains by going to thinner timber? An experiment for another day perhaps :)
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

remo
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Re: DIY Speaker cab and experiment.

Post by remo » 17 Mar 2010, 20:11

nice thread, I love building projects like this. One this I might suggest is instead of the old rat fur try this:

http://www.duram.com.au/productdetail_var11var22var319

It's tough enough to be used in the tray of a ute so I would expect many years of service as a cab coating compound.
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Re: DIY Speaker cab and experiment.

Post by Petebass » 18 Mar 2010, 16:00

remo wrote:nice thread, I love building projects like this. One this I might suggest is instead of the old rat fur try this:

http://www.duram.com.au/productdetail_var11var22var319

It's tough enough to be used in the tray of a ute so I would expect many years of service as a cab coating compound.
Looks good but I've already started the carpeting process.

The problem with coatings like this is weight. I have previously built two identical 2x12 cabs which are identical except one is covered with carpet and the other got sent to the local Rhino ute liner guy to get coated. The ute liner is extremely tough, but that cab weighs 3kg more than the carpet covered one.

That sparked a bit of research on my part and in summary, products which dry via evaporation and/or exposure to air don't add weight, but aren't very durable e.g. paint, estapol. Any product that "cures" to dry will be much more durable, but it will weigh the same dry as it did wet. So if you use 1itre on your cab, and a 1 litre tin weighs say 3kg, you've just added 3kg of weight.

I guess I should take pics of the carpeting process? More to come ......
Last edited by Petebass on 19 Mar 2010, 11:27, edited 1 time in total.
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

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Re: DIY Speaker cab and experiment.

Post by Petebass » 18 Mar 2010, 17:40

Ok this is how I go about attaching the protective carpet:-

Commercial manufacturers use carpet with a self-adhesive backing, but I don’t know where to get it in small quantities. Most people use some sort of spray adhesive for this job, but I’ve found them all to be rubbish.

I once again use exterior grade PVA glue because it’s strong and resistant to spilled drinks. The trick is to use just enough glue. Too much and it’ll seep through the carpet and harden to an undesirable stiff wire brush texture on the outer surface of the cab. Not enough glue and it won’t stick properly. I've got a pretty good idea nowadays how how thick/thin to spread it:
Image

Lay the carpet over the glue and position and pat it down by hand. Then add a bit of weight while it's drying. That's a piece of melamine board. The PVA glue doesn't stick to the melamine all that well so there's no danger of accidentally attaching it permanently.
Image

Then I used those pieces of timber wrapped in packing tape to glue down the carpet on the front lip. Again the packing tape prevents the glue from sticking where you don't want it to. Trimming the corners is the tricky part:
Image

So far so good but without being able to use staples, this is taking a lot longer than it normal. Staples allowed me to do the whole cab in one go. Instead I have to do one panel at a time.
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

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Re: DIY Speaker cab and experiment.

Post by Petebass » 28 Mar 2010, 13:08

Sorry to keep y'all waiting for a update. It's been a pretty hectic week which included an plumbing emergency of the worst kind... don't ask.... lets just say I will never ever use the expression "Sh1t Happens" ever again :)

Here's what the cab looks like at the moment. All it really needs is a grill and some tweaks to the tone circuitry and it's done.
Image

I have run my first lot of frequency sweeps, but only at a reasonably moderate volume, and here's the first frequency response graph. For this test I had the 2.5K notch filter in place, the one I posted a picture of earlier.
Image

Not bad! That's pretty much what I wanted. It's not perfectly flat, but it's as close as reasonable on a 2 way design and that hump at 80Hz to 100Hz region is pretty much what I wanted on this cab. For those of you who heard my previous 1x12 at the Sydney GTG, this new cab does indeed sound noticeably fuller, but maintains the clarity and articulation in the mids that I believe is essential to being heard live. That mid scoop between 500Hz and 1K looks worse than it sounds. This cab does not sound scooped. If fact I'm considering adding a toggle switch which activates a "warmer again" circuit i.e another notch to the high mids which also attenuates the tweeter some more. I think that'll be particularly useful for recording or for gigs where a more mellow approach is more appropriate.

Right now the cab weighs 11.2kg. By the time I add a grill and other circuitry, 12kg is looking likely. It really does feel light! It's 3kg lighter then my previous 1x12, but it's physically much bigger (71 litres compared to 40 litres), and those 3kg are very noticeable. I can only imagine how light the composite cab is going to feel.

Speaking of which, someone I know made a Carbon Fibre composite version of my previous 1x12 design. It shaved 3kg off the weight. I'll post some pics and info over in the thread for that cab:-
http://www.ozbassforum.com/viewtopic.ph ... d&start=15

More to come.
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

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Re: DIY Speaker cab and experiment.

Post by Petebass » 29 Mar 2010, 17:02

Today I fiddled with the crossover circuitry to see if I could flatten out that frequency response a little more. I swapped out the notch filter in the mids for an even simpler solution, an inductor in series with the 12" woofer to simply replace the inductance lost when we went from ferrite to neo speakers. I also attenuated the horn a little bit.

I ran the Frequency response sweeps twice, once at a quiet level as per yesterday's tests, then again at a higher SPL. I'm still not quite at ear bleeding levels but I did have to wear ear muffs for the second experiment as it got a bit loud and uncomfortable.

I did the sweep at a higher level just to be certain the frequency response wasn't being tainted by such a low level signal in the original tests. As you can see, the frequency response of the higher SPL test (the Red line) mirrors that of the lower SPL tests (the black line).

Image

It looks and sounds like he frequency response has flattened out even further than yesterday's tests. The cab sounds noticeable smoother, but still has the bite required for slapping and other techniques which require a bit of zing. I'm thinking this is the frequency response that will please most bass players, so I'm likely to make this the standard circuitry for this cab, and add a toggle to revert to yesterdays tone as a "brighter" circuit. I'll have to figure out if such wiring is possible before I make a decision on that.

I guess the next step is to make the grille. That can be my project for the Easter break.
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

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Re: DIY Speaker cab and experiment.

Post by Petebass » 02 Apr 2010, 20:41

Ok the final wiring is done the cab is sounding pretty darn good IMO. I ended up with 2 toggle switches, One toggle bypasses the notch filter I used to smooth out the mids, just in case you feel like you need to cut through a bit more. The other toggle turns the tweeter on or off.

Tomorrow I'll make a grill and that's it, the wooden cab is finished. I'll post some final photo's soon.

That means I'm almost ready to start work on the composite version of this cab. I've already been on a shopping expedition to buy everything I'll need, so I'm not far from starting what I expect to be a challenging build. I'm looking forward to it !

I've already outlined the process of making a grill in a previous thread, but in the interest if keeping it all in one place, I'll cut and paste it into this thread as well:-

"I'm using some extruded steel mesh I had left over from my last build. Notice it's started rusting, so I had to get the wet and dry sandpaper out and clean up the part I'll be using for this cab. I've measured and marked in texter and I'm about to fire up the angle grinder to cut the metal to size.
Image

Next mark out where the folds are in the metal are going to go, mark it, and cut out the corners.
Image

Now I use two pieces or hardwood, some F-clamps, and a hammer to make a crude panbrake to bend the edges:-
Image

Image

Image

Some budget gloss spray paint goes onto the grill, then it's ready to go into the cab.
Image
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

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Re: DIY Speaker cab and experiment.

Post by PilbaraBass » 02 Apr 2010, 20:51

I love that fiddly bits spray paint... it's cheap as chips and quite good, actually...

you should do the grill in something like blue, however... just for something a little different :)
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Re: DIY Speaker cab and experiment.

Post by Rude_Mechanical » 02 Apr 2010, 21:57

Petebass wrote:I did the sweep at a higher level just to be certain the frequency response wasn't being tainted by such a low level signal in the original tests. As you can see, the frequency response of the higher SPL test (the Red line) mirrors that of the lower SPL tests (the black line).

Image
That looks like a nice, usable cab - just enough kick in the fundamental / 1st order harmonic freqs to reinforce the fact that you're a _bass_ player :)

c-
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Re: DIY Speaker cab and experiment.

Post by Petebass » 04 Apr 2010, 09:46

PilbaraBass wrote:I love that fiddly bits spray paint... it's cheap as chips and quite good, actually...

you should do the grill in something like blue, however... just for something a little different :)
Any colour as long as it's black! I've done the coloured grill thing previously but I found it just makes it a dead giveaway that the cab is DIY. I like to keep people guessing :)

I've tried all sorts of paint for grills, including some pretty expensive paint, but everything eventually scratches it's way off. And that includes whatever it is they use on commercial cabs. So I figure I'd rather use $5 paint and just touch it up whenever it needs it.


Rude_Mechanical wrote:IThat looks like a nice, usable cab - just enough kick in the fundamental / 1st order harmonic freqs to reinforce the fact that you're a _bass_ player :)
It sounds very much like a bass cab. Even the low B is solid! That reference to the 1st harmonic touches on something not everyone knows so I'll outline it here briefly.

Most electric basses have a much stronger 1st harmonic than fundamental. For example, if you played a low E on a spectrum analyser, the fundamental 41Hz frequency is often 10dB or 12dB down on the 1st harmonic of 82Hz, depending on the bass used of course. So if you used a narrow band EQ to remove 40Hz, you'd certainly hear the sound of that note thinning out, but nowhere near as much as is you removed 80Hz. As a result, most bass cabs only need to produce 40Hz at -12dB because doing so does not subtract anything/much from the original note.

So that hump in the freq response between 60Hz and 200Hz accentuates the 1st harmonic of the low B right through to the open G string. In other words, it's right where you want it as a bass player. And no, that was no accident :yep . But care has also been taken to produce enough fundamental to support the bass notes properly.

For reference, this cab not only sounds fuller than my previous 1x12, it has more depth than the 2x12 as well! Surprisingly it competes with my much larger vintage JBL 1x15 for bottoms. And it does this without sacrificing efficiency. I played music through it and adjusted the volume to 90dB. Without touching any of the controls I then switched over to my 2x12, expecting the 2x12 to be louder. Nope, still 90dB. Switching over to my other 1x12 produced a 3dB drop. So it's both louder and fuller than my previous 1x12.

Could I have gone lower. Yep! But the cab would have to be considerably larger and at 72l, it's already about as large as I'd like to get for a 1x12.
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

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Petebass
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Re: DIY Speaker cab and experiment.

Post by Petebass » 04 Apr 2010, 10:02

OK guys, the plywood cab is officially FINISHED! :hyper:

Here's a pic of the final cab. You cab see the two toggles inside the handle recess. I positioned them carefully so as to not get in the way of your carry hand, but they're recessed enough that placing another cab on top won't break them off. But most importantly, they're where you can reach them while playing a gig. Placing them around the back makes no sense to me.

Image

So how much does it weigh?

Image

I'll put it through it paces at some upcoming gigs and rehearsals an perform any fine tuning adjustments as required, but that shouldn't stop me from getting started on the next part of this experiment.

That's right folks, now the real fun starts. the composite cab build shall commence ASAP! This should be interesting :hyper:
* 2 Stingray 5's (one heavily modded), Ibanez SR805, Ashbory, + more...
* Carvin B1500, Epifani PS1000, Ashdown Superfly amps.
* Lots of DIY neo/lightweight cabs including one made from composites http://www.ozbassforum.com/viewtopic.php?f=5&t=2546

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