I have found 5x5 sheets of baltic birch locally. 18mm is $84.99 a sheet, that seems a bit steep to me. I know it's not nearly as good but the Birch plywood at lowes or home depot is 35-45 dollars a sheet at 4x8. I know this is mostly luan core with a birch veneer and not as good as the BB, but come on.
Does that price seem high to you guys?
Still hoping to make some sawdust this weekend but who knows...
Thanks.
Does that price seem high to you guys?
Still hoping to make some sawdust this weekend but who knows...
Thanks.
Just is my opinion and others might disagree but the 3/4 birch at HD should be just fine. Yeah it's cheaper wood and yeah it might have voids or flaws but if you brace it properly and do a good job finishing it, it will still be rock solid and you probably wouldn't be able to tell the difference. I've built 6 subs now from the stuff HD sells and I haven't had any concern about its strength.
Chris,
Are you using a 6 cubic foot box like DJK did for the two speakers in your sim?
Art
"Does that price seem high to you guys?"
Yes, and the 5'x5' sheets will have too musch waste.
Check on marine ply (no voids), it runs about $70 for a 3/4" 4x8 sheet.
Yes, and the 5'x5' sheets will have too musch waste.
Check on marine ply (no voids), it runs about $70 for a 3/4" 4x8 sheet.
Thanks, I hadn't gotten around to trying a layout for 5x5, I figured it wouldn't be pretty though as the 4x8 layout is very efficient.
Last Cabs I built (the scoops) were just whatever exterior 3/4" ply lowes had in stock at the time. Not pretty, but one of those scoops rolled out of a truck bed on a sharp turn and hit pavement with minimal damage to one edge. Probably a bit of luck involved there too, but they were plenty strong. well then I may be off to home depot or lowes in the morning. I'm going to build two boxes initially.
Last Cabs I built (the scoops) were just whatever exterior 3/4" ply lowes had in stock at the time. Not pretty, but one of those scoops rolled out of a truck bed on a sharp turn and hit pavement with minimal damage to one edge. Probably a bit of luck involved there too, but they were plenty strong. well then I may be off to home depot or lowes in the morning. I'm going to build two boxes initially.
At one point in time I found some 9-ply A2 oak for cheap, that made for some real nice cabinets, and the oak was more resistant to scuffs and scrapes than birch. One Sunday when I needed to make some mids (for use at noon the next day) the best plywood I could find was some 5-ply yellow pine that proved to be almost as hard as the oak was!
http://i56.photobucket.com/albums/g196/dkleitsch/dual12MantaRay.jpg
The yellow pine monsters!
PS, my computer table is made from that same batch of yellow pine!
http://i56.photobucket.com/albums/g196/dkleitsch/dual12MantaRay.jpg
The yellow pine monsters!
PS, my computer table is made from that same batch of yellow pine!
Hmm.... you mean the drivers are not just in parallel? I'm using the 8 ohm version, I don't really want a 16 ohm load to my amp do I? or am I not understanding? Is there a schematic somewhere?
Does this look adequate for bracing? I"ll hollow out the middle one of course, maybe just with a hole saw it will be quicker I have also added the cavity for handles, but would prefer to build them and determine the center of gravity before deciding on an exact placement. Should be trivial to cut them out with a router and template afterwards.
Attachments
"Hmm.... you mean the drivers are not just in parallel? I'm using the 8 ohm version, I don't really want a 16 ohm load to my amp do I? or am I not understanding? Is there a schematic somewhere?"
Sorry, I was describing the dual 4Ω driver version (most of mine are that way, I bought 100 drivers), you have 8Ω drivers so they will be parallel connected.
Your bracing will probably be OK.
Sorry, I was describing the dual 4Ω driver version (most of mine are that way, I bought 100 drivers), you have 8Ω drivers so they will be parallel connected.
Your bracing will probably be OK.
Approximately, yes.
I'm not sure its relevant, though - a smaller cabinet reduces efficiency by reducing excursion for a given power input. A smaller cabinet EQ'd to the response of a larger one will have the same excursion but larger power requirements.
I'll run the sims with the exact drivers and double-check, but I strongly suspect something's amiss with the SPL vs Xmax claims made so far.
EDIT
Ran the Hornresp sims. 2x Eminence Kappa 15 LF2, ported box tuned to 35Hz, and then I played with cabinet volume to get a near-flat response in-band. This is approximately 1kW per driver to achieve the 130dB SPL claimed. See attachments for the Hornresp dump.
Chris
Attachments
Last edited:
I'll do the BassBox excursion and output screenprints and post them on Monday.
6th order does have as much as 2dB less output than 4th order over a narrow band above cut-off, but much more output overall.
Every design involves trade-offs, and 6th order is the best compromise (IMO).
6th order does have as much as 2dB less output than 4th order over a narrow band above cut-off, but much more output overall.
Every design involves trade-offs, and 6th order is the best compromise (IMO).
Last edited:
Started building yesterday. Ended up buying pine, the birch at HD was prefinished with a glossy surface that looked like cheap particle board furniture from wal mart. The oak had nasty sides all dinged up. The pine looked good and was cheap. It's not the most durable though and I didn't notice till I got home but it's China pine. Oh well. Rented a table saw for $42. The fence was hanky I had to use a clamp to hold it square. Probably could have done better with my circular saw and rip guide.
Everything came out ok. I rough cut the panels with circ saw to make them easier to get into the table saw since I was working alone. Made a ghetto out feed table with a wires helping unit and that smooth material they actually use on such things, I forget what it's called but I had a small sheet my father in law gave me.
The table saw fence only went to 25 inches so the bigger cuts had to be done with circ saw and rip guide. I'm making two boxes so I clamped two sheets together and cut two at a time to be sure I got two identical pieces.
First thing that struck me was just how compact these are. Wow.
Got too cold to glue so that's on the agenda today a
Everything came out ok. I rough cut the panels with circ saw to make them easier to get into the table saw since I was working alone. Made a ghetto out feed table with a wires helping unit and that smooth material they actually use on such things, I forget what it's called but I had a small sheet my father in law gave me.
The table saw fence only went to 25 inches so the bigger cuts had to be done with circ saw and rip guide. I'm making two boxes so I clamped two sheets together and cut two at a time to be sure I got two identical pieces.
First thing that struck me was just how compact these are. Wow.
Got too cold to glue so that's on the agenda today a
Glad your build is going well Sigma. Not sure if you have the room but older Craftsman TS can be had on Craiglist/paper for nearly what you paid for in rent. Then you can dial it in and build panel jigs etc.
The FR and size factor of the PPSL is getting me interested. Some questions for those familiar. I simmed multiples and it appears the low corner is getting lower. True? Also, wanted to confirm that in HR displacement is for both drivers so I can effectively use 2X xmax. Having a hard time believing what I am seeing: I simmed a pair of PPSL with PA385 that is near 140db to 30hz and both together are basically the size of one large TH cabinet... 😱 Surely I am doing something wrong. 😀 If this is remotely true, I might snag some PA380s while on sale to try the concept and hear it for myself.
The FR and size factor of the PPSL is getting me interested. Some questions for those familiar. I simmed multiples and it appears the low corner is getting lower. True? Also, wanted to confirm that in HR displacement is for both drivers so I can effectively use 2X xmax. Having a hard time believing what I am seeing: I simmed a pair of PPSL with PA385 that is near 140db to 30hz and both together are basically the size of one large TH cabinet... 😱 Surely I am doing something wrong. 😀 If this is remotely true, I might snag some PA380s while on sale to try the concept and hear it for myself.
Hornresp shows the cone excursion of the drivers. Using 2x Xmax would imply your driver(s) can move 8mm when rated Xmax is 4mm etc etc.
Chris
True, but the low corner changes very little. The Fs of multiple drivers in close proximity drops slightly, but Fb is unaffected by the number of drivers.
Chris already explained that doubling drivers does not increase excursion, but it does double displacement.
Doubling displacement, power, and cabinet size results in a 6 dB increase in level.
Don't bother with sims above the Xmax of your driver, driven above Xmax drivers progressively sound worse. At double the Xmax rating, you hear the "flap" a lot louder than the fundamental tone, and the reduction of even order harmonics the PPSL provides won't make any change in that regard.
Art
I've been looking, don't have a ton of space but could fit one in. Anyway, want to have these done by thanksgiving so I just rented the saw to get it done.
The China pine sucks but I think the first box will hold up anyway. Gonna need a durable finish. I guess everyone fills with bondo? I'd like to find some warnex, but I don't think it's available in the states. Is duratex worth the money?
Also, which driver gets wired out of phase?
Thanks!
Duratex is 100% worth the money every time. I'm a huge fan personally. It also doesn't take much a whole lot. Can't give exact numbers, but I'd estimate a gallon would easily do 4 cabs.
The driver with the basket exposed to the outside should be wired in reverse phase.
The driver with the basket exposed to the outside should be wired in reverse phase.
In HR I compared PPSL with a TH (Snyder/Steele) using PA385 and output is same but PPSL goes to 30hz and flatter above 100hz (who cares 😀) but TH only to 40hz. Once I converted metric to imperial I realized the TH is actually smaller than the PPSL?! Was hoping the PPSL would be 3-6db over the TH and be the smaller of the 2... Maybe once DJK posts we will learn how he is getting more out of the design. HR vs BB issue?
- Status
- Not open for further replies.