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DIY GFRP Sandwich Panel 1x15PR400
- Thread starter astack
- Start date
... plus cylinders for the magnet structure, and perhaps a fudge factor for the basket. I assume the OP did something like that to come up with his .08cf number. I've also constructed a 3D CAD model of the speaker, but it's still nice to have the manufacturer's data.
Yeah, that occurred to me as a reason for not publishing speaker displacement. Front-loading complicates the calculation, but since manufacturers can't account for the variables of mounting method or baffle thickness, rear-loaded displacement would be the number to publish, IMO.
Hmm good discussion. I believe I found ~0.1cf referenced as a typical 15" speaker on that car stereo site in the stickies, iirc, and used that as a starting point. My 143ci number (.08cf) is hard coded in the spreadsheet - thought I'd find how I calc'd that... I'll dig back through my notebook to see. I think it was a function of Sd and Xmax and not the cone shape though... Apparently I misunderstood what I was calc'ing?
Also, front loaded with an inch thick baffle... Yeah I guess a published spec would only be so helpful.
Also, front loaded with an inch thick baffle... Yeah I guess a published spec would only be so helpful.
Passinwind
I know nothing.
- Dec 3, 2003
- 23,076
- 46,029
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
I think I looked at the page once when I started using the program and forgot about it.
The geometry is a little funky on the 15PR400, so it's not a one-to-one, but I guessed best I could on dims:
Comes out to double my original guess
I also can't find my scratch calc for the 0.08cf.But this is for rear loaded, so I think I'm still OK. It'll be OK people!
Thanks Charlie for the tip!
Passinwind
I know nothing.
- Dec 3, 2003
- 23,076
- 46,029
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
There's another similar one in the software suite from the Loudspeaker Design Cook 7th Edition. It's in spreadsheet format (.xls), and you can download it for free Link Removed.
Since Will mentioned them, and I also seriously considered going that route, I thought I'd look at how the Faital matches up with a pair of Deltalite 2512 II's on the lowend with WinISD.
I loaded my box - 3.1cf and 42Hz with a single Faital (red) and then started a new project with two Deltalites (green). WinISD has a handy way to tinker with the box volume and tuning "knobs" by clinking over the box image and dragging. So I did that until the transfer function magnitudes matched up. I also started a third project with the default SBB alignment of the 2xDLII just for comparision (orange/black). (Of course there are plenty of other alignments I could have tried for slightly different results...)
Inputs:
Transfer function:
Max SPL (considers excursion):
Hehe
Max power (considers excursion):
Group Delay:
Other things:
Given that they both also have good full range capabilities (or so I've been told), two great options for simple 1-way, light weight boxes. IIRC, the Deltalites are pretty popular these days for more production-type cabs (Aguilar, Mesa, etc. I could be wrong). I do like the 2x12 form factor, but thought if I'm doing the composite route, I want it to be mega light, which the single speaker has the edge for (including a lighter/smaller box).
So there you have it...
I loaded my box - 3.1cf and 42Hz with a single Faital (red) and then started a new project with two Deltalites (green). WinISD has a handy way to tinker with the box volume and tuning "knobs" by clinking over the box image and dragging. So I did that until the transfer function magnitudes matched up. I also started a third project with the default SBB alignment of the 2xDLII just for comparision (orange/black). (Of course there are plenty of other alignments I could have tried for slightly different results...)
Inputs:
Transfer function:
Max SPL (considers excursion):
Hehe
Max power (considers excursion):
Group Delay:
Other things:
Given that they both also have good full range capabilities (or so I've been told), two great options for simple 1-way, light weight boxes. IIRC, the Deltalites are pretty popular these days for more production-type cabs (Aguilar, Mesa, etc. I could be wrong). I do like the 2x12 form factor, but thought if I'm doing the composite route, I want it to be mega light, which the single speaker has the edge for (including a lighter/smaller box).
So there you have it...
Awesome! Other goodies there, too. I've heard a lot of people swear by that book, but the libraries I checked didn't have it.
I almost went 
until I remembered you manipulated the box size until the transfer function chart lined up. I was going my DLII's show a higher displacement limit than that, bit your models are also trying to play deeper response, so that means they run into excursion limits sooner.
I still think you're on the right track with the Faital, especially seeing as you have to purchase 2 drivers with DL's as opposed to 1 Faital. Can check my model in a while here. At 2.27 cu.ft. tuned 44-45hz I think I was getting a little bit over 200watts displacement limit for the pair. Considering all my amps are 300-400 watts @4 ohms, they're a good match. The pair models around 100db/1wl1m in the lows and climbs from there. I cut them off by 1khz and pass it off to a 6. I can still run them fullrange if I want to and sound good because they're not an LF tyoe driver, just lack a little topend I'm used to having with the 2 way system.
The Faitals curve is smoother and they play plenty high. Looks like a damn nice driver for a fullrange "1 speaker plays it all" 15 cab. A pair would be as loud as anyone needs to be with a medium size amp.
Anyway, keep up the progress. You're going to end up with a damn fine rig there.
until I remembered you manipulated the box size until the transfer function chart lined up. I was going my DLII's show a higher displacement limit than that, bit your models are also trying to play deeper response, so that means they run into excursion limits sooner.I still think you're on the right track with the Faital, especially seeing as you have to purchase 2 drivers with DL's as opposed to 1 Faital. Can check my model in a while here. At 2.27 cu.ft. tuned 44-45hz I think I was getting a little bit over 200watts displacement limit for the pair. Considering all my amps are 300-400 watts @4 ohms, they're a good match. The pair models around 100db/1wl1m in the lows and climbs from there. I cut them off by 1khz and pass it off to a 6. I can still run them fullrange if I want to and sound good because they're not an LF tyoe driver, just lack a little topend I'm used to having with the 2 way system.
The Faitals curve is smoother and they play plenty high. Looks like a damn nice driver for a fullrange "1 speaker plays it all" 15 cab. A pair would be as loud as anyone needs to be with a medium size amp.
Anyway, keep up the progress. You're going to end up with a damn fine rig there.
will33 said:
Just had to say, that bit about adding foam is hilarious...
Edit: hilariously awesome.
Still alive here. Just finished up getting (mostly) settled into out new place and finally have time again to work on this guy. 
Of course in the mean time, I've been reading up on a bunch of other designs...
I think I've caught the bug!
Side note: 1" XPS foam was nearly impossible to find here in the bay area. Everywhere had 1/2" and 2" a few with 3/4". I nearly gave up until I stumbled across some at Home Depot of all places in Emeryville (went to 3 other HD's before with no success). I had even tried half a dozen building supply specialty places. I'm pretty happy with the look and performance of 1" so far, so I'm glad I held out.
Being from the midwest, where insulation is actually needed, never thought it'd be hard to find this stuff. Anyway, heads up to anyone in warm climates that is looking at doing this.
OK, way too much talk! Need to finish this thing...
Of course in the mean time, I've been reading up on a bunch of other designs...
I think I've caught the bug!Side note: 1" XPS foam was nearly impossible to find here in the bay area. Everywhere had 1/2" and 2" a few with 3/4". I nearly gave up until I stumbled across some at Home Depot of all places in Emeryville (went to 3 other HD's before with no success). I had even tried half a dozen building supply specialty places. I'm pretty happy with the look and performance of 1" so far, so I'm glad I held out.
Being from the midwest, where insulation is actually needed, never thought it'd be hard to find this stuff. Anyway, heads up to anyone in warm climates that is looking at doing this.
OK, way too much talk! Need to finish this thing...
Alright, short first day back. Just wanted to get this thing cleaned up and ready for the final glassing tomorrow.
Mixed up some more epoxy/silica/micro of varying proportions to reinforce the inside fillets and float out the back and outside joints. The last panel to go on was a bit lacking especially on these because I thought I could get by with less. (Wrong...)
Here's a new and improved fillet:
On to the outside. As you could see a page or so back, the outside joints had some gaps, so I used a wetter mix to flow down and fill 'em up.
At the top and bottom, I had gone back and sanded a bit to get everything matched up better and took the dremel to the inside/side glass (the lines along the top/bottom edges). Because of the hardness mismatch, I had to take a bit of foam with it (~1/8" or so along that line). So, then I went back with more a peanut buttery mix to float out the ever so slight mismatches.
While I was at it, I floated out the "holes" in the back panel, so it's now an even surface, although it covered up that smooth mylar finish. Ehh.
(Re: The white area)
And finally, the new work space ATM:
To be honest, I'm not quite sure how this last part's gonna go with wrapping it all, but worst case, there'll be tons of micro to cover up blemished.
We'll see soon enough
Mixed up some more epoxy/silica/micro of varying proportions to reinforce the inside fillets and float out the back and outside joints. The last panel to go on was a bit lacking especially on these because I thought I could get by with less. (Wrong...)
Here's a new and improved fillet:
On to the outside. As you could see a page or so back, the outside joints had some gaps, so I used a wetter mix to flow down and fill 'em up.
At the top and bottom, I had gone back and sanded a bit to get everything matched up better and took the dremel to the inside/side glass (the lines along the top/bottom edges). Because of the hardness mismatch, I had to take a bit of foam with it (~1/8" or so along that line). So, then I went back with more a peanut buttery mix to float out the ever so slight mismatches.
While I was at it, I floated out the "holes" in the back panel, so it's now an even surface, although it covered up that smooth mylar finish. Ehh.
(Re: The white area)
And finally, the new work space ATM:
To be honest, I'm not quite sure how this last part's gonna go with wrapping it all, but worst case, there'll be tons of micro to cover up blemished.
We'll see soon enough
Well the story of this build is running short of materials all the time and today didn't disappoint. A couple yards short on glass, so I just cut what I could and will pick up more tomorrow.
Not one to want to waste the whole day, I did a few more little things.
First, added a layer of micro/fairing to the front of the baffle, since that's the only surface I didn't have cure on something, so there's a good amount of print-through and if I sanded it, I'd be sanding glass pretty quick.
On to cutting a hole for the jack plate. Since the last time, I went out and bought a cheap tile jigsaw blade, so that's what I tried. And...
No contest. This worked so much better than the dremel cutting bit. Compare:
Compared to the dremel, the tile blade went faster, cleaner, was easier to maneuver, didn't leave shards of FG, and didn't melt the foam. Compared to a fine-toothed jigsaw blade, the tile blade didn't delaminate the FG skins.
In goes the jack plate:
And finally, the mock up:
Other upcoming stuff:
I've figured out a good way to do the outside wrap that should be pretty straight forward. Not sure this image will make sense to anyone... But it shows the order of glassing (read from top left to bottom right... like a book).
Anyway, point is, you get 2 layers everywhere, don't need to wrestle with a giant piece of glass, get sufficient overlap (4-6" would be good, I'm thinking), timing should work out that you don't have to glass a vertical surface or have a too sticky side down (I'll be working on melamine again so it doesn't bond). We'll see how it goes
Still thinking about how I want to mount the speaker and hardware. I have bolts and flat t-nuts for the speaker and handle. Thinking of epoxying the t-nuts to the inside and then use a nylon locking washer on the inside. Not totally sold on this method. I'd kind of like a solid spacer between the FG skins for the speaker, too. For the corners and jack plate, I think it'll be something like Petebass did with plastic drywall anchors. Only problem is, they need to be short enough to not stick through the panel and be able to be flush mounted. Haven't found any like that yet. I think the feet get the same treatment as the handle. Hmm...
Not one to want to waste the whole day, I did a few more little things.
First, added a layer of micro/fairing to the front of the baffle, since that's the only surface I didn't have cure on something, so there's a good amount of print-through and if I sanded it, I'd be sanding glass pretty quick.
On to cutting a hole for the jack plate. Since the last time, I went out and bought a cheap tile jigsaw blade, so that's what I tried. And...
No contest. This worked so much better than the dremel cutting bit. Compare:
Compared to the dremel, the tile blade went faster, cleaner, was easier to maneuver, didn't leave shards of FG, and didn't melt the foam. Compared to a fine-toothed jigsaw blade, the tile blade didn't delaminate the FG skins.
In goes the jack plate:
And finally, the mock up:
Other upcoming stuff:
I've figured out a good way to do the outside wrap that should be pretty straight forward. Not sure this image will make sense to anyone... But it shows the order of glassing (read from top left to bottom right... like a book).
Anyway, point is, you get 2 layers everywhere, don't need to wrestle with a giant piece of glass, get sufficient overlap (4-6" would be good, I'm thinking), timing should work out that you don't have to glass a vertical surface or have a too sticky side down (I'll be working on melamine again so it doesn't bond). We'll see how it goes
Still thinking about how I want to mount the speaker and hardware. I have bolts and flat t-nuts for the speaker and handle. Thinking of epoxying the t-nuts to the inside and then use a nylon locking washer on the inside. Not totally sold on this method. I'd kind of like a solid spacer between the FG skins for the speaker, too. For the corners and jack plate, I think it'll be something like Petebass did with plastic drywall anchors. Only problem is, they need to be short enough to not stick through the panel and be able to be flush mounted. Haven't found any like that yet. I think the feet get the same treatment as the handle. Hmm...
Your drawing makes total sense to me. Going aroud like that and havig the seams meet sort of half-way past the previous seams should be strong. I assume you'd figure out something similair for the baffle and back, either by layering, or by usimg different folding schemes with a larger piece of cloth/fb, which would I guess be another sort of layering?
I just like the idea how after it's all said and done, it's sort of a one-piece "shell" without any weak spots that could separate or break away easier than the rest.
Would you guys do something similair on the interior? Again more curiosity. No glass experience here.
I just like the idea how after it's all said and done, it's sort of a one-piece "shell" without any weak spots that could separate or break away easier than the rest.
Would you guys do something similair on the interior? Again more curiosity. No glass experience here.
Don't know if I'd want to take on a FRP build, but I enjoy watching build logs like this one. Thanks for taking the time to document and post.
Since you're an engineer, here's an armchair quarterback question:
One thing I've noticed in every FRP build is internal fillets with filled epoxy, as you're doing. I understand that it's difficult to wrap the glass around a sharp internal radius, but... do you think it's necessary to carry the fiberglass to the internal corners? It seems that would be a low-stress area, and it would save time to simply glass slightly short of the internal corners and edges. That could be done in the flat, before assembly.
Zac2944, nice to see you here. Chime in if you like.
Since you're an engineer, here's an armchair quarterback question:
One thing I've noticed in every FRP build is internal fillets with filled epoxy, as you're doing. I understand that it's difficult to wrap the glass around a sharp internal radius, but... do you think it's necessary to carry the fiberglass to the internal corners? It seems that would be a low-stress area, and it would save time to simply glass slightly short of the internal corners and edges. That could be done in the flat, before assembly.
Zac2944, nice to see you here. Chime in if you like.
