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Discussion Starter #41 (Edited)
Ok, another question for you all. When I look at these plots, I am looking at what the SPL would be for a given input power source. Obviously these 18" drivers can get louder than what I have, but that's at peak volume. If I rarely, if ever am hitting above 100dB, what difference will these 18s or even 4 or 8 DPL-15s do for me? Are you strickly adding volume? And if with a BFD you can contour these plots a bit, couldn't you make them all about the same response curve? If that's the case then isn't the difference between driver TYPE and NUMBER simply a matter of max volume and how much EQ is necessary to get the curve you want? The advantage the DPLs have so far over anything else I've modeled is that they don't drop off as much as anybody else's below 30Hz-ish. I know what I have will be ok for now, I'm just curious to know these answers.

Thanks in advance.
 

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Multiple drivers adds headroom capability and sensitivity. It allows the individual drivers to work less hard which keeps distortion lower and other compression effects. I think you may be surprised at how hard you end up driving that single pair of 15's. Driver for driver IB is not a huge output monster. That's why you always see 4 or 8 drivers being used.

I don't know how well those 2 15's are going to do when trying to hit 100db at the listening position in the 10-25hz range. You may run out of excursion. IB's are always mechanically limited (excursion at the low end). I'm not trying to freak you out, just saying to take your time learning where the limits are with them when you get them installed.

I would've recommended the Fi IB 18's if you hadn't already purchased the DPL's. Yes I would've still recommended 4 too as they come in packs of 4 for $800 and you shouldn't have to ever worry about headroom with that much displacement. Add one EP2500 to drive all 4 and you have an incredible reference capable bass system for less than $1300 total.
 

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Multiple drivers adds headroom capability and sensitivity. It allows the individual drivers to work less hard which keeps distortion lower and other compression effects. I think you may be surprised at how hard you end up driving that single pair of 15's. Driver for driver IB is not a huge output monster. That's why you always see 4 or 8 drivers being used.

I don't know how well those 2 15's are going to do when trying to hit 100db at the listening position in the 10-25hz range. You may run out of excursion. IB's are always mechanically limited (excursion at the low end). I'm not trying to freak you out, just saying to take your time learning where the limits are with them when you get them installed.
but a single 12" could already be way more than enough
 

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Discussion Starter #44
Multiple drivers adds headroom capability and sensitivity. It allows the individual drivers to work less hard which keeps distortion lower and other compression effects. I think you may be surprised at how hard you end up driving that single pair of 15's. Driver for driver IB is not a huge output monster. That's why you always see 4 or 8 drivers being used.

I don't know how well those 2 15's are going to do when trying to hit 100db at the listening position in the 10-25hz range. You may run out of excursion. IB's are always mechanically limited (excursion at the low end). I'm not trying to freak you out, just saying to take your time learning where the limits are with them when you get them installed.

I would've recommended the Fi IB 18's if you hadn't already purchased the DPL's. Yes I would've still recommended 4 too as they come in packs of 4 for $800 and you shouldn't have to ever worry about headroom with that much displacement. Add one EP2500 to drive all 4 and you have an incredible reference capable bass system for less than $1300 total.
Yeah, I hear ya. I spent $370 on drivers, $800 is a hole 'nuther ballpark. I don't think I'd be able to mount 4 of them in a cube though as they're too big for the 16" gaps between studs in the roof. I'd have to go higher which I don't think I can. That'd take me back to the two hole idea.

The one thing I have going for me is that the DPL-15s do relatively better than any of the other mentioned drivers at the <20Hz range. All the others drop off like mad. So the only thing "leaning my way" is the lower distortion I'll get for the better un-eq'd low end, and the 8ohm impedence which should be nice and easy on my amp. That and the fact that I'm not going to be in bridged mode which is like 10x worse in the distortion category.

I'll pull out the cliche "this is a journey" idea now and say that I will always be saving money for fun stuff. I'm 29 and this is my first attempt. I'm sure each house I own will have a nice IB install in it. Wish me luck, everything arrives today! I'll take pics.
 

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but a single 12" could already be way more than enough
It really depends on the volume of the room, the driver used and the design.

A JL Audio 12w7 would easily fill most rooms in the proper box. But it's no ordinary sub either. The Infinity Perfect Kappa sub is another driver capable of filling a room. Even the Dayton Reference drivers are capable. Everyone has different wants in their theater and a great 12" design is vastly superior to the majority of commercial designs on the market today. SVS only has one sub with a driver bigger than 12. As does JL Audio and many other manufacturers.

Few people ever need a tapped horn Maelstrom 21" to fill their wants either. Not that the world can't enjoy such a beautiful sub. :R Consider what this guy is coming from I think 2 15" will more than satisfy him for now.
 

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I'll pull out the cliche "this is a journey" idea now and say that I will always be saving money for fun stuff. I'm 29 and this is my first attempt. I'm sure each house I own will have a nice IB install in it. Wish me luck, everything arrives today! I'll take pics.
Consider good luck wished. Take your time with the build and keep us updated.:T
 

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Discussion Starter #48
Thanks all for the motivation! Before I forget, in WinISD do I select "normal" or "iso-barik" for this opposed-speaker manifold type of IB? Gives much higher levels on normal than iso-barik. Everyone seems to be using normal, while I assumed iso-barik.

So I spent Saturday working on my design, cutting/laminating panels, and getting the wall wiring done. I had to redesign a little bit. When I got up in the attic, I noticed that there was an extra beam I didn't know about (see pic below) and that the roof is very close to the internal ceiling. As you can see, the triangle support beams get in the way of "setting" a manifold box on top of the normal trusses. I also have that extra beam for some reason breaking up my 24" working space into a smaller 17.5" working space. Actually the beam isn't completely straight so it's 17.25" up to 17.5" of workspace. Since the left side of my box is going to have to sit next to the left truss (instead of sit on it) that cuts my space down to 16" since the laminated panels are 1.5" wide. The drivers are 15.5" so 16" didn't give me much structural support to my box with only .25" inches on each side of the driver. SO, I decided on something else. I'm going to take what was going to be the box's right panel and nail it into the "slot" you see between the right-most truss and the extra beam (nailed to the extra beam, not the truss). I'll have to move that power cable obviously. Then I'll assemble the rest of the manifold and drag it up there and nail it to that right panel. That'll make my box wider by the width of that 2x4 (1.75"). That moves me from 15.5" to 17.25" (up to 17.5") wide panels which I can deal with to mount my drivers in. You can see a couple of my panels in the second picture. They are 20" by 17.5" panels. One is 17.25". My top panel will have to be trapezoidal. Errrghh...

I may also not install the customary 2x4 cross beams that people use to set the box on top of. Since the left wall will go all the way down to the drywall, I'm thinking of having the entire box rest flush with the drywall. Obviously since my right panel is on the other side of that extra beam, I will have to "notch" the bottom to fit around the beam. The box would then be nailed to the trusses instead of using tie plates.

Any thoughts? I've gotta go to work tomorrow, but I might assemble my manifold as much as possible in the evening. That laminated wood is heavy; it's going to be a PITA to drag up into the attic and into that space. I don't know exactly how I'm going to have room to screw it in without contorting my body to great degrees. Par for the course?


Install location is before the cross beam with the power on it. If you look at the living room pic from page 1, this area is right above the right speaker stand.


Drivers and some prelaminated mdf/osd panels:


A few panels propped up to show shape:
 

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Discussion Starter #49 (Edited)
Pic of comparison between something kinda similar to my PS-1000 (250W, 10", 4th order bandpass in teal), my DPL-15 x 2 IB project (yellow), SS-18 x 2 IB (purple), Maelstrom 21 x 1 IB (green), and an insane 12 driver IB setup (blue) that I found here: http://www.subwoofer-builder.com/ib.htm
All but linked IB setup and the 10" boxed sub are assuming 550W RMS. Box size set to 10000L for IBs. I used normal, not iso-barik.




How the picture changes when I upgrade to 4 DPL-15s instead of 2, yellow curve now ROCKS:
 

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Discussion Starter #50
I'm not regretting at all going with the DPL-15s after looking at these yellow plots lines. I'll see what I think once it's all installed and tested though. Man I hope I don't fubar anything!
 

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Looks good. Use normal for modeling. You are not running an Isobarik set-up.

As said just make your manifold capable of adding 2 more drives later if you need them later.
 

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Discussion Starter #52
Yeah, I've just got to make sure the 2 extra drivers will fit in the triangle shaped holes you see in the pics. If I pre-cut the holes, I don't know how I'll plug them up for now since I can't glue the "donut hole" onto a panel and slap it on the sides, there's no room. I may just not cut the holes now. That'll make it harder to do the upgrade later though.
 

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Discussion Starter #53
Last question for now: the drivers come with a harder plastic/rubber cover going around the perimeter of the driver. I thought about removing it, but it looks like it'll fit more flush with it in place. What's the norm, leave it or remove it? The metal alone is L-shaped or has a lip that would have to dig into the wood or would prevent the thing from sitting flush.
 

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That outer rim surround will help create a seal between the driver and cabinet, so it should be left in place really, unless you plan to seal it another way.
 

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Discussion Starter #56 (Edited)
When looking again at those WinISD charts, I noticed something I'll have to deal with. When you model with 4 DPL-15s, the cone excursion is perfectly fine with a 550W signal. It stays below the xmax of 22mm. With only two though it hits xmax at 20Hz and goes as high as 30mm by the time you hit 10Hz. How will I protect the drivers from this? With the BFD? How do I know how much to tweak to be safe? You know, that just doesn't make a lot of sense to me. The maximum wattage they give on their site for the driver is 600W. It's specifically an IB driver, yet when you model it at that 600W for a single driver in an IB, you get cone excursion of 43mm down at 10Hz. Why would they say the max is 600W then if it sounds like that isn't realistic? Help!

Also, is there no way in WinISD to say if you're hooking up the 4 drivers in series, parallel, or a combination? The numbers will obviously change quite a bit depending on how I wire them. Do I have to go change Znom or something?
 

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When looking again at those WinISD charts, I noticed something I'll have to deal with. When you model with 4 DPL-15s, the cone excursion is perfectly fine with a 550W signal. It stays below the xmax of 22mm. With only two though it hits xmax at 20Hz and goes as high as 30mm by the time you hit 10Hz. How will I protect the drivers from this? With the BFD? How do I know how much to tweak to be safe? You know, that just doesn't make a lot of sense to me. The maximum wattage they give on their site for the driver is 600W. It's specifically an IB driver, yet when you model it at that 600W for a single driver in an IB, you get cone excursion of 43mm down at 10Hz. Why would they say the max is 600W then if it sounds like that isn't realistic? Help!

Also, is there no way in WinISD to say if you're hooking up the 4 drivers in series, parallel, or a combination? The numbers will obviously change quite a bit depending on how I wire them. Do I have to go change Znom or something?
The watts for a driver is simply the power handling capabilities of the motor. Its the eventual cabinet design/size that determines how much actual power is needed to reach maximum excursion. Smaller cabinets reduce excursion capabilities for any given amount of input, you can get round this by adding power and in these cases more power handling ability is a good thing. Dont forget that adding or subtracting drivers into a given volume effectively increases and decreases the cabinet size each driver sees. With an IB you alter cabinet size by adding and removing drivers because you obviously cant alter the cabinet itself as with a traditional sub build. Its not always gospel that you have to put all the power into the motor, and as ever a bit of head room is only a good thing. This is where the custom designing bit comes in though, because as you reduce input power, you reduce SPL produced, so you need to monitor all aspects of the design to get to where you want.

For modelling drivers with different VC wiring configurations, you can alter this in the drivers parameters for the type your going to use by editing the TSP's. I dont think you can model multiple drivers in the same cabinet with different wiring configurations though, I'm fairly certain of that. I also think that it would be asking for trouble to do that personally.
 

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Discussion Starter #59
by "a combination" I meant two sets of parallel drivers wired in series. That would make them all equal still and the amp would see a single 8ohm load still, even with 4 drivers.
 

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by "a combination" I meant two sets of parallel drivers wired in series. That would make them all equal still and the amp would see a single 8ohm load still, even with 4 drivers.
Ah right, well then you dont need to alter the driver parameters as they remain the same, its only the amp that sees a different load, so you can just model as normal with 4 drivers, or how ever many you want to use. Just make sure your amp is happy with the load your going to present it with :T
 
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