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Discussion Starter #1
Hi everyone, thanks for all your posts on this forum - what a great resource.

I'm building a house and planning on an IB sub using 4 x IXL 18.2.2's. Yes, I know this is not the IB forum. Stay with me please! :)

While the house is being designed and built (12 months still) I want to put the drivers in simple boxes so I can play with them and the amp, etc.

I am building the (2) boxes already. For simplicity and WAF they are about 170l, sealed.

I'll be driving them with an EP4000 and EQ with a FBQ2496.

So, with boxes about this size, an EP4000 and four drivers to play with, can I use two drivers per box or will this be worse than a single driver per box?

I'm happy to cope with the complexity of the 2/box option if it will be a better result. Usage will be 80% HT, 20% music.

Modelling in WinISD seems to suggest it will be better with two per box, although I'm not sure how much amp power to use in each model...

Appreciate any advice please?
 

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Elite Shackster
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Hi Mat, welcome to HTS.

I'm a big fan of sealed subs, but Ive pretty much come to the conclusion that to really do a sealed design justice you need to use multiple drivers. 2 drivers are excellent, and if you have more there is nothing wrong with making multiple driver designs etc etc.

I would build 2 dual driver boxes, this will give the best balance of having powerful subs while affording you the options to better integrate them into your system using eq, which I see your already setup to take advantage of. I assume you have REW and an SPL meter?

When modelling, a dual driver sub will require double the cabinet volume of a single driver version, and because your using 2 drivers, the subwoofers power handling also doubles (800 watts per driver max, so 1600 total). Sealed subs are power hungry beasts, and the power is needed to eq them properly, especially at the low end, so more power is good. Using multiple drivers simply means the available power is shared across the drivers. When you model your subs though, be sure to pay attention to the Qtc and adjust your cab size to suit the system Q your prefer. Typically, the middle ground (safest option if you dont know what your doing) is to go for .707. Higher will increase upper bass punch, but could lead to an overly boomy sound depending on your tastes. Lower will lead to a cleaner lower sound, which you might find robs some musicality, but your mainly HT focus will probably suit this more. FWIW, your IB will have a very low system Q close to the Qts value of your drivers, so to get more of an idea of how that will sound you could try a Qtc of .505. Larger cabinets will lower the system Q, and especially seeing as these are a temporary option, you could experiment a little by building larger cabs, and displacing some of the volume to alter the Qtc and learning from how system Q alters the sound character of a sealed sub.

Hope that ramble helps :D

Enjoy the forums :T
 

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Discussion Starter #3 (Edited)
Hey Moonfly, thanks for the quick and helpful response. Chalk up one vote for two drivers per cabinet, thanks!

Regarding Qtc, I'm a bit of a noob - how do I work that out? The manufacturer recommends 130l for a sealed cabinet. My boxes will be about 170l because this makes the box
(a) big enough to line up with the entertainment unit next to it
(b) big enough to fit two drivers in
(c) as big as I can get through the WAF.

EDIT - I think (if I did it right) that Qtc in a 170litre box (6 cu ft) is 0.56 - but this is for one driver, right? How does using two affect this?

If 170l turns out to be too big, I figured I can always displace some volume. I modelled this box in WinISD and it looks 130 or 170litres makes little difference - but again, I'm a noob and could be doing it completely wrong.

My other concern - I'm planning on only one EP4000 to drive both cabinets, will this drive 4 drivers across two cabinets OK or would I be better sticking with two drivers, two cabinets?

Thanks to all who are reading, and look forward to any help!
 

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Elite Shackster
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The 130 litre recommendation is probably based on a Qtc of around .7, so for 2 driver you would need 260 litres to maintain the same system Q (Qtc value). If you look in the box tab of your model in WinISD, you will see the Qtc value at the bottom, and you can monitor how that changes when cabinet volume is altered. From the sounds of thing, 2 drivers in a 170litre cabinet will lead to quite a high System Q, which is going to make these subs very punchy, and probably insane chest pounders. The low end grunt will be there, but not as prominent and somewhat overshadowed by the upper bass power. You can help off set an undersized cabinet a little bit by using poly fibre fill stuffing, as this has the effect of making the driver(s) act like they are in a cabinet thats larger than it is. There is an article here on that:

http://www.nousaine.com/pdfs/Box%20Stuffing.pdf

The EP4000 is 2 ohm stable, so it can run both subs with dual drivers in each, but I would keep the stock fan in it for this purpose as its the heaviest load the amp can handle, which translates into it producing more heat. Its not an issue if enough air is moving over the heat sync to remove it and keep the amp cool. The up side is that the EP4000 will put out more wattage when running 2ohms, which will suit your subs better.
 

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Discussion Starter #6
Wow, thanks guys so much for your help already. I didn't expect to get so many answers so quickly.

Of course Qtc is in WinISD, I thought it would be. I feel like an idiot. I didn't look hard enough.

Modelling with 2 drivers gives a Qtc of 0.726. That's not too far away from the ideal you mentioned of 0.707, is it? Makes me think the box size is still OK for two drivers perhaps? But then, 1 driver per box is a Q of 0.584 - good for real low bass. Hmmm.

Your comments about the load on the amp are great, and makes me stop and think. I can't live with a loud amp, either now or in the final IB setup - I HAVE to do the fan mod, I assume. Given that this will be the same load as in the IB, would I be best to get a second EP4000 maybe? At $570 AUD per amp it's not a big deal (compared to $1300 worth of drivers!). Obviously not ideal but a small price to pay for oodles of power and no risk of overheating etc. I'll have to do more research about guys running 4xIXL 18s off an EP4000. Anyone here doing that?

The sensible option would be one cabinet, two drivers, one EP4000.

Of course that's not going to happen!

Thanks again, Dan & Mike for your speedy answers. Any and all help appreciated.

Mat
 

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Elite Shackster
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I run my dual driver sub from an EP4000, and run it from one channel. My amp never gets hot so it is possible to run your subs from one amp. Could you put the EP in another room, thats what I did so I could keep the original fan in. I also keep the clip limiter on just for peace of mind, and may spare channel runs a bass shaker. My amp never even gets warm. If your going to mod the fans though, I do think a second amp will be a good idea, but when you get the IB up and running, you wont need as much power and series wiring your drivers will lower the load and one amp will probably fine at that point.

I think the 130 litre subs QTC is a good one, and thats what Ive made my subs Qtc at (.675 for mine), and I think it sound fantastic. It also suggests the driver have good upper bass sound naturally, which again is a good thing, and makes them a good choice for an IB too IMO. I think a Qtc of .726 will be leaning towards the boomy side, but you can easily try it and see what you think, and taste is personal.
 

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Discussion Starter #9
OK, great, thanks. I didn't realise you could series-wire the drivers in an IB (hadn't read that far ahead!).

My plan will be two cabinets, one driver each (for a Qtc around 0.58) and one EP4000. This should give me a sound closer to an IB (which I've never heard so I'm keen to keep the sound more similar) and a suitable load for the amp.

I can always displace some volume inside the boxes then to play with the Qtc.

Guys, I can't thank you again. Off to the workshop!
 

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Elite Shackster
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Sounds like a good plan, just remember though that it takes less power to move the driver as you increase cab size. Chances are you could bottom the drivers if you push too hard (although Ive not modelled it), which isnt an issue, but you should be aware of it for peace of mind. You can monitor this in WinISD as well :T
 

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2 drivers are better than 1, but if the choice is between 1 driver in 4 boxes vs 2 drivers in 2 boxes. The 4 boxes will give you the best placement possible. Though only if your room allows.
 

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Discussion Starter #12
Boxes are nearly finished, up to the point of designing grilles. I don't have the drivers yet (haven't made the circle cuts) and I can't find a dimension anywhere for how far the driver protrudes from the face it is mounted on; i.e. how much clearance the grille cloth needs from the mounting face.

Does anyone have an IXL 18.2.2 and can tell me how much clearance to allow from the face to the max driver extension? From the diagram on the Mach5 website I estimate it to be about 40mm (just over 1.5"). Is this right?

Thanks to anyone that can help.
 

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Discussion Starter #14
Thanks Mike, 1.5" it is.

Finished building the first box. I have a tendency to over-engineer things.... the box is 60kg without the driver. Oops! :dontknow:

Got no idea how I'm going to move these things when they have the 15kg drivers in them too. Sheesh!
 

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Discussion Starter #17
Ha!...and fair enough too, thanks to you guys for your help.

The first box is done and sealed - without the driver cutout (have to wait 4-6 weeks for stock to arrive ) there's not much to see - roughly a 24" cube with 1.5" walls...

As I make the second one I'll take some pics etc. It's a bit embarrassing after seeing your last build, though Dan. My excuse is these are temporary boxes (12 months max) so the bracing etc isn't very elegant.

But man is it heavy. :flex:
 

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Elite Shackster
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I wouldnt worry about how it looks all that much, as long as its solid it will do its job. Routing the bracing like I have is pretty much pointless, but its easy to do so I do just because I like it. If your boxes are temporary then not finishing them makes sense too.

In the end we are all just enthusiasts, and we cant resist a look at a build :D
 
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