Soon the build of my first T48s starts!

[Robin_Larsson]

Handles, Yeah, of course airtight mounting:) but still if something intrudes in to horn path, or steals volume from a driverchamber, albeit a DR or a Titan doesnt that affect performance? Will 2 % difference in volume make a difference, 10%? 20%? How much is ok?
I do want to get the best sound I can after all, don't wanna change Bills plans:)
I saw a thread where someone put on of those nice adjustable tophats in a DR 200, that must have made a significant difference in the driverchambers volume? I guess Bill have spent many hours getting all measurements and relationships just right, and deviating to much from that must make a difference in sound? I´ll read my plans again, see what The Man him self writes about it again:)


I'll see if I can put together a small box of scrap ply and the Simson MRC CA construction adhesive or such that we use at work, and test it with pressurized air:)

luckily, my landlord is a carpenter, and has a fully equipped workshop 5 metres from my kitchen, that I can use:) I think I've seen atleast 8 different bradnailers in there:) and I speak from experience when I recommend everyone not to shot selves in a finger with a bradnailer! it really hurts..

But what about plywood thickness, should I account for 12 mm being 0.7 mm thinner than nominal 1/2 " ply? How's everyone else in the metric world done it? Also, would it be prudent or maybe even stupid to round of to nearest whole millimeter on the measurements that are uneven? Say 24" which is 609,6mm, round to 610? That must be well inside the design tolerances right? If I watercut everything it doesn't matter, but if I'm gonna saw some panels it makes it easier.

[Robin_Larsson]

Another thing you may want to look at is how you do your mouth bracing. Many people have replaced the flat horizontal connector piece in the mouth bracing with a 1" or larger dowel rod and use that as a handle grab spot as well when lifting the mouth. I can tell you that I have personally helped someone move 4x 24" T48 made of baltic birch and they were heavier than i would want to move so make sure you get a dowel that is very strong. (Everyone here knows i'm a self-proclaimed whimp.)

I could use an aluminium or even stainless steel pipe, I could probably find 2 pieces 900mm long leftovers of 25mm polished SS pipe, we use a few hundres meter of that stuff at work each year:) Could overengineer a nice way to attach it:P Could use that for handles in the back panel, up and down also, saw a nice pic of a T39 I think with something like that. Downside to stainless is that it sucks to paint..

I personally don't use them but ratchet straps will work fine for this and they are cheap. You will be surprised that if you brace the horn mouths on the subs you will actually get very little vibration. In fact I find that the only reason mine tend to walk was when i didn't have the bracing installed, the duratex made the tops slip off. I have since added in the mouth bracing and put rubber feet on the bottom and they no longer walk anywhere. Keep in mind that when you say "stacking" I am assuming that you are having your stacks 56' apart from each other, this is why you don't hear of this problem too often here as most people center or wall cluster their subs with the tops on stands or placed elsewhere not on top of the subs.

Yeah, we´ve used ratchet straps alot, I like to avoid it in the BFM future:Pv In the dark ages we stacked two subs with one top on each side the stage, only once we´ve had around 56feet between them, usually a lot less. But never again stacking like that!
I had no idea about that before finding this place, but now I know, so we´re gonna do a single V-stack in a corner everytime we can with the Titans:)
But it would feel good to have something that locks them togehter so they dont slide of when we have more then 1 high. Like a small steel stud, that goes in to a "hole" in each cab, one in each corner, going in like 10-20mm in each, that way they can never move without being lifted a bit. Should even be "stumbling drunk" safe:P But maybe rubberfeet and small recces in the cab under is enough?

When V-stacking like 4 subs, 2 high, must it be "airtight" between the two cabs stacked on each other, or is say ~1" rubberfeet distance okey? I´ll make it airtight and as close as it needs to be it make a difference. Same the V-plate
Really cant wait until I get to stack 6 36" T48s in a 3 high V, to see how it looks and sounds:D 2.7m high

[netwerks]

luckily, my landlord is a carpenter, and has a fully equipped workshop 5 metres from my kitchen, that I can use:) I think I've seen atleast 8 different bradnailers in there:) and I speak from experience when I recommend everyone not to shot selves in a finger with a bradnailer! it really hurts..

Shooting yourself in the fingernail hurts even worse!

But what about plywood thickness, should I account for 12 mm being 0.7 mm thinner than nominal 1/2 " ply? How's everyone else in the metric world done it? Also, would it be prudent or maybe even stupid to round of to nearest whole millimeter on the measurements that are uneven? Say 24" which is 609,6mm, round to 610? That must be well inside the design tolerances right? If I watercut everything it doesn't matter, but if I'm gonna saw some panels it makes it easier.

I cant answer this because I haven't built in metric but yet another good reason why PL is recommended as it can fill up to 1/8" gap if you are a little off.

[AntonZ]

Use only PL premium as per the recommended plans. If you cant get it there locally look online.

Just not available in Europe, getting PL shipped from the US is freakin expensive. There are alternatives, see the thread on where to source materials in Europe: http://billfitzmaurice.info/forum/viewt ... =14&t=4140

The expanding bit is important for two reasons:
1. airtight: expanding glue closes gaps (I'm no superskilled carpenter, so not a perfect seamless fit on every joint). Airtight is soooo important in horns.
2. as it expands, the glue pushes itself into the pores of the wood, making a stronger bond than non-expanding glue can do.

But what about plywood thickness, should I account for 12 mm being 0.7 mm thinner than nominal 1/2 " ply? How's everyone else in the metric world done it? Also, would it be prudent or maybe even stupid to round of to nearest whole millimeter on the measurements that are uneven? Say 24" which is 609,6mm, round to 610? That must be well inside the design tolerances right? If I watercut everything it doesn't matter, but if I'm gonna saw some panels it makes it easier.

There is no such thing as 12mm ply nor 1/2" ply. It's all with tolerances that are not very tight. What we would call 12mm, they call 1/2" and vice versa.

I have rounded all measurements to the nearest in whole mm's. Used a spreadsheet to do all the conversions, to avoid human error as much as possible. Wrote all mm measurements in my copies of the plans (every measurement, all pages).

[Rune Bivrin]

There is no such thing as 12mm ply nor 1/2" ply. It's all with tolerances that are not very tight. What we would call 12mm, they call 1/2" and vice versa.

I have rounded all measurements to the nearest in whole mm's. Used a spreadsheet to do all the conversions, to avoid human error as much as possible. Wrote all mm measurements in my copies of the plans (every measurement, all pages).

I got myself two steel rulers with inches on one side and millimeters on the other. One is 24", the other 50" (off the top of my head). I tried the conversion route, but that was more trouble than it was worth.

[Dave Non-Zero]

Don't worry about the plywood, and don't worry about the handles in the chamber. I've got them and there is no problem. 6 metal handles per sub. Top/bottom, and two per side. Think of the variation in the chamber volume between a slim version and a wide version and you'll realise that the volume taken up by a handle is nothing.

[AntonZ]

There is no such thing as 12mm ply nor 1/2" ply. It's all with tolerances that are not very tight. What we would call 12mm, they call 1/2" and vice versa.

I have rounded all measurements to the nearest in whole mm's. Used a spreadsheet to do all the conversions, to avoid human error as much as possible. Wrote all mm measurements in my copies of the plans (every measurement, all pages).

I got myself two steel rulers with inches on one side and millimeters on the other. One is 24", the other 50" (off the top of my head). I tried the conversion route, but that was more trouble than it was worth.

I find it cumbersome, too. But until recently I had no "feel" for measurements in inches. Making it easy and likely to cut/build things in sizes that are way off. All the talk in inches here has made me somewhat more comfortable with them, so some day I may build in inches, until then mm it is for me.

[Robin_Larsson]

Thanks guys!

Yeah, I know there´s tolerances on plywood, but it aint as much as 1mm:P As I said, I measured the ones I have, Auruco or how ever its spelled, and it doesent vary more then 0.1 mm in thickness on around 10 measurementpoints on to sheets, I´d say its 12.0mm
Most likely its the same sheets that you can buy in USA or so, its probably not 1/2" there, but rather 15/32".
But what ever, I´ll follow the plans and offset 12mm then:)

Way easier for me to just draw everything in autocad, and just scale it to metric. Simply draw it with the numbers in the plan, then scale it 25.4times bigger, voila a metric BFM:P Then I could round it of as I like and use 12mm thickness. If someone is interested I could provide dxf/dwg drawings or just pdfs with measurements in both metric and imperial, or just metric. Or even my cutsheets and all. Of course with Bills permission or through him. We´ll solve that if someone wants them and when I´m done with the drawings and have built atleast one cab.

Dave, as you say, the change in volume of chambers and horns from handles are not that big, but I wanna build the wider version to get the best bass, and for example putting a handle each side, could potentially block of 2-3 inches or more of the hornpath, depends on where they end up, should that be noticed? I know, I´m rambling:P


And yeah, bradnailer in a fingernail, does not sound like a nice thing:P
I´ll probably build the first cab with one the handles as per Bills design, and then see if we want top and bottom handles.
Dave, how do you lock your T48s together when stackin 2-3 high? "Locking" corners?

[Dave Non-Zero]

yeah, locking corners. i usually strap them too though, especially if im stacking tops on top.

[Robin_Larsson]

Nice video Dave:) Something like that is what I´m planning to do also, I guess you have a dolly of some sort that you just lift the cabs onto? You lock that in place with the straps also?
Its those plastic locking corners right? I´ll see if I can come up with a simple design that gives a more positive lock..

How much volume can the handles be allowed to steal, before its possible to notice? I mean, handles in the sides does make the cab effectively more narrow, atlest where they are, if for example one would more or less block of the lower hornfold-corner, to say 1.5" in on each side, wouldn´t that make a 36" cab play more like a 33"? Or does a relatively small restriction like that not make a real difference? Same in the driverchamber, if the handles takes up say 5% volume, in a cab without the reducerpanel, would it simply get more like a cab with the reducer?
Havent decided on the reducer yet in the T48s, only gonna build 2 cabs now, but hopefully 2-4 more later this year.

I think I would prefer the type of handle that is a cutted square/arced in of all 4 sides type of handle, cant find a pic of one right now.. That would have to be made airtight with a spacer and a plywood plate on the inside, or a thinner metalplate:P

When using metal handles of the type I posted a link to earlier, is there anything besides making it 100% airtight to consider? Think I seen something where someone coated with some kind of insulation/car underbody paint or whatever it was., to make sure you dont get any ringing or so?

I just had a quick look at Meyersounds website and their bigger linearray systems, they have the type of quickconnect fly rigging system I tried to describe earlier:P They even have a steelframe bolted on the outside of the cab that contain all rigging points and takes all load. smart, then when you destroy parts in the fly hardware you just change that frame instead of having to take apart the whole cab! And they also integrated simple steelpipe handles in them:)

Also found this: http://www.vikingaudio.com/images/line_ ... ging_1.jpg Looks like a good way to rigg line array!

[Dave Non-Zero]

Yeah, and have you ever tried to pick up a Meyer cab? Two man lift for even small topboxes.

Just bung in some handles wherever you want dude. It makes no difference.

I'm still thinking about a cost effective system for locking tops together at the angles required, but I've been using blocks of wood and straps for a few years now so it's not the biggest priority.

[Robin_Larsson]

LoL! No, I have never used Meyer, I´ll take your word for it!

Okey, I´ll try to let go of my obsession about stealing volume from the cab then:P Just that I thought I read something about not doing that, and getting measurements correct and all that:P
Thanks again all of you! This place is great!

If I´ll figure out a simple, effective way to couple the DR 280s, I´ll let you know! And I hear you Dave, needs to be lightweight, and slim. Something like Meyers frames maybe, perhaps in Alu, or as thin steel as possible. Or more integrated to the cab. The Meyer-frame does also solve the handle problem:P

[Dave Non-Zero]

I can't even face the price of buying the pins at a fiver each, never mind the extra weight involved! I've rigged many a PA with flying hardware and it's much easier to woodblock and strap lightweight cabs than have the fanciest rigging but still need two people to hold the box in place while you line up a pin hole.
If you find a cheap supply of the pins then I'll start thinkig about it again.

[Robin_Larsson]

Yeah, the pins are pricey to say the least! Have been looking, not found anything cheap yet, but we´ll see:)

I do see your point, no need to overcomplicate things! You usually groundstack your tops or? Put the bottom one on something to get it up a bit? Guess you´r not using a tophat and a standard speakerstand to stack 2-3 280s high, or are you?

I´d like to fly my tops from lifiting stands, or trussing, but maybe no need for that with only one each side. But if flying a few in a line array, then I sure want something more than woodblocks and straps:P

[netwerks]

Okey, I´ll try to let go of my obsession about stealing volume from the cab then:P Just that I thought I read something about not doing that, and getting measurements correct and all that:P
Thanks again all of you! This place is great!

Those spring loaded handles you pointed out will not take up any volume and they work great. Perfect for your application. Anything more than that is overkill IMO. Keep it simple.