Need some pointers for my first project

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#81
One thing I do like about the 12pw is that it will be more flexible if I ever want to try some different designs. It seems to be a woofer that can work with anything.

I think I would be looking at a speaker that's at least 70cm tall, though, so for desk use it might be a bit impractical. That's combining the height of the alpair enclosure with the 12pw. Unless I ditch the shallow design idea

Scottmoose said:
Re his remarks, Mark simply meant that the 12PW is not a subwoofer...
Click to expand...

I see, that does make sense. Probably not the best wording for something marketed as a woofer though
 
#82
Bringing the box up to a depth of around 160 internally does actually make it a realistic idea. I just have to think about the best tradeoff for size. Another benefit of a smaller box I thought would be smaller panels and less bracing required.
 
#83
Skinny box.

FatCGR-visulaization.png


http://www.planet10-hifi.com/planset/fatCGR-extents.pdf

Seal it up, install an A12pw (or any driver for that matter that uses the sam evolume [& fits]) instead of the A10p… to get it up to 70 cm you’d need 20 cm of stand, but the box shape is easily tweaked.

dave
 
#84
Thanks for the suggestion. I wasn't very clear in what I meant. I meant that being 70cm would be too tall. I may just go for something like the box you sent me.

I was initially wanting it as shallow as possible to attempt to reduce the delay of the front wall reflections. I think realistically 150mm inside was the shallowest I could really go, not sure if being 190mm deep will make much difference. I'm pretty tempted on the 12PW
 
#85
A sealed box is very mutable. To be shallower the shown box would need to be taller, wider, or a combo.

If the box is essentially hanging off a wall making the sides 45° (ie huge chamfers) can helreduce bipole dip and improve the transition to the wall being the baffle.

The slower, earlier rolloff of sealed, should better match what the wall does, a BR ewould need a different tuning to increase damping closer to a sealed box so the extension difference between sealed and BR in this specific case probably becomes moot.

dave
 
#90
Quite busy atm so I don't have much time to think about this now but still want to get on with it.

I have been wondering what sort of layout I can do for the speakers. I decided I want them as a CGR with width being the longest dimension.

I thought about 21 litres ish for the 12pw making the internal dimensions 276Hx446Wx170D, and about 9.7 litres for the alpair which makes 214Hx346Wx132D. I plan to to make them separate enclsoures so I can interchange woofer/midtweet if I buy something new in the future.

I have realised that this would make a rather square looking baffle once you add up the heights and account for thickness of wood (and also add extra external width for alpair to make the baffle the same). As far as I understand, this isn't optimal in terms of diffraction, so wondering if anyone can give any pointers on keeping the box reasonably shallow and the right sort of shape. If I make a CGR for about 31 litres the box is a good size, but once I split the box in two, I am messing with the internal dimensions a lot. Wondering if anyone can suggest anything. If I separate the enclosures with angled pieces of wood, would this help?
 
#93
Hi, Dave. The box size for the 12pw isn't the issue. I was aiming for something like 21 litres to account for bracing. Not sure if I should aim lower to account for stuffing too. I think the optimal size is about 20 litres from memory. I thought better to be too big than too small, but I'm not really sure how much exactly QTC changes with stuffing.

I'm not really sure how to implement the 7ms on top becase for q 0.707 it's about 8.7 litres, was aiming for about 9.7 box size. Once I then stack the boxes the baffle becomes esentially square shaped. From what I've worked out, it looks like the best way is to make a box of about 31 litres (very happy with dimenions of 31 litre CGR) litres and split it in two on the inside, but then I mess with the internal ratios so wasn't sure how to go about it. Or maybe I'm just overthinking something that's not much of an issue?


I was thinking instead of splitting it with a straight piece of wood, perhaps splitting it with two angled bits of wood to help disperse any standing waves
 
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#94
20 litres is about right but far from critical. Stuffing will increase the effective volume (and is easily changed after the build for fine tuning if necessary.

The trick i use as a start with a CGR is cuberoot(volume[litres x 1000]) = w. Then d=w/1,618, h = w x 1.618. Then i fiddle the dimensions to account for the box material, brace (and in my case the vent structure).

A7ms up top is even less critical, as you will be rolling off the bottom.

dave
 
#95
I plan on crossing minimum 200 I think. I was thinking of changing the xovers for different listening distances. I'm going to wait until they're in my room and measured before I decide on what is the best xover frequency. I'm going to try and pick the most flat looking area between 200-400, and I may even apply some linear phase EQ before I do the crossover.

I was aiming for QTC 0.707 or less on the 7ms to match the 12pw, I'm not really sure how much difference it'll make 200-400hz. I was previously considering making the 7ms vented but wasn't sure if this would affect transients. a QTC of 0.8 is 4.94 litres.

I'm still not really certain of how to add the drivers boxes together without affecting the exterior or interior ratio too much. Unless I build the 7ms box inside a 30 litre box. What would you advise? I'm happy to go away and read a bit more on this, but it'll have to wait a few days unfortunately. I am pretty eager to get the main details down asap
 
#97
Thanks, Dave. I'm going to look into some mid enclosure ideas, I like the idea of the lines that run the sound waves through all the stuffing so they can't come back through the cone. Wondering if I can squeeze this into a single enclosure with the 12pw
 
#98
I think I've been overthinking the squarish baffle I'll end up with by using two stacked boxes. After looking into it, it seems like it'll be fine with the drivers slightly off centre + rounded/angled/bevelled edges. Although the speaker will end up quite huge. I considered a similar idea to tysen mid tweet but with only 19cm depth internal the mid enclosure would be tiny. Unless someone is willing to advise on how to squeeze in 5-9l in a 31l cgr, I'll probably go with stacked speakers.

As the 7ms is similar size sealed and ported, I am considering making it ported and using heavy stuffing to push it towards sealed as you suggested, Dave. Then this would be enable me to adapt it to a regular full range 7ms if needed
 
#100
Not yet, I was planning to wait a little to see how my living situation changes. I'm pretty tempted to just order one for now to keep the dream alive and also it feels much easier buying one at a time instead of two in one go 😀 I actually have all the things I need for one in my basket at KJF 😀

Still trying to decide if I should build it all into one enclosure or two separate. I think I prefer the look of all in one (sort of like those big sideways studiomonitors),
 
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