Twelve 10" NHT Subwoofer Build. - AVS Forum
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post #1 of 274 Old 08-27-2008, 07:27 PM - Thread Starter
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Well, I'm about to start my basement's final subwoofer design and I might need a little bit of advice along the way with this one.

I've decided to go a slightly different way than two 12' or 15's.

I just ordered 12 of NHT's 10" subwoofers (new) that used to be used in their "SubTwo" boxes. My understanding is that they perform pretty good, so I figure why not overkill the whole thing and just use 10-12 to be on the safe side. Xmax is stated at 12.5mm. I'm not really sure how these will compare with two 15's, but I guess it's too late anyway. One helpful member here said I should go with 12 to get the Ohms to work out right.....so I did.



Anyway, here are the specs: I have to be honest, I'm in the learning stage here, so I don't understand most of these numbers just yet.

Re: 9.58
Fs:21.5
Qms: 2.952
Qes: .444
Qts: .386
Vas: 103.84
Cms: .00561
Mms: 97.8
BL: 16.87
SPL: 85.47
Zmax: 73.2
Sd: .03631
Xmax: 12.5
Hg: 8
Hvc: 33



Photo of the old NHT SubTwo:



Their product sheet says:

Frequency Response:21Hz - 180Hz, +/-3dB



If anyone has any recommendations on box shape, or cubit ft per sub, it would be much appreciated. I have read that they should be in a sealed box, but I'm not sure of the size just yet. Power will be from an EP1500 or EP2500.
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post #2 of 274 Old 08-27-2008, 07:46 PM - Thread Starter
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Because I listen to music about 30-35%, I thought that this idea might make some sense.


What if I make 4 seperate boxes, each holding 3 subs. Each box would be wired at 4 Ohms.


Could I put 2 boxes in the front, and 2 boxes in the back of the room, then wire the fronts together as 8 Ohms for one amp channel, and wire the backs together for the other channel. That way I could just use channel one for listening to music, but run both channels at the same time when I watch movies?



I simply don't know how loud these things will be and I'm not sure if I will need more than the 450 watts per channel that the EP2500 does at 8 Ohms.


Plus would having a fairly common 4 Ohm wired box may be better later down the road if they get split up?
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post #3 of 274 Old 08-27-2008, 08:45 PM
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I was thinking about 10's just the other day.

So I calculated a pair of eD 18's vs. eight eD 10's. Came out to be the almost the same output, with the two 18's having just slightly more output.
I decided to stick with my plan of two (or four) 18's. Especially when I factored in that two eD 18's would be under $400 while eight 10's would be more than twice as expensive.

Your having four seperate boxes should smooth out the room response if used in seperate corners, according to what I've read in this forum.

"The boom is dead, long live the bass"
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post #4 of 274 Old 08-27-2008, 08:49 PM
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Quote:
Originally Posted by Erich H View Post

Because I listen to music about 30-35%, I thought that this idea might make some sense.


What if I make 4 seperate boxes, each holding 3 subs. Each box would be wired at 4 Ohms.


Could I put 2 boxes in the front, and 2 boxes in the back of the room, then wire the fronts together as 8 Ohms for one amp channel, and wire the backs together for the other channel. That way I could just use channel one for listening to music, but run both channels at the same time when I watch movies?



I simply don't know how loud these things will be and I'm not sure if I will need more than the 450 watts per channel that the EP2500 does at 8 Ohms.


Plus would having a fairly common 4 Ohm wired box may be better later down the road if they get split up?


If you're going with an EP2500 and four boxes @ 4ohms each, then you'll want to run the amp in mono. Wire up pairs of boxes in 8 ohms, then bring the pairs together to present a 4ohm mono load for the EP2500. This would use max output from the amp. Just make sure to use something like 10guage speaker wire going to each box, if you're planning on having them far away from the amp.

"The boom is dead, long live the bass"
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post #5 of 274 Old 08-27-2008, 08:58 PM
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I built 2 sealed boxes each with 2 drivers and powered by Oaudio 500w amps-2cuft each box. Never measured them but performed well for HT under my mains. The Dual 10 ported end table version in 6.5cuft blew them away on HT but didn't like sub 20hz content-the subsonic filter in the amp wasn't steep enough to control excursion and the drivers would bottom out. I've since disabled both versions and i'm trying these out in H frame dipole alignment as bass bins crossed high around 200hz below OB MMTs. I think six dual driver towers placed around your room would be pretty intense. Maybe 2 up front with a higher Q and 2 sides and 2 back in around 3 cubes eash and crossed a bit lower-say 40hz. Either way sounds like fun. Good luck
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post #6 of 274 Old 08-27-2008, 09:07 PM - Thread Starter
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The 10" subwoofers came to about $400 shipped. So that's pretty good I thought. I can make sealed enclosures and keep the boxes height low enough to go under my screen. I have low ceilings in my basement.

I'm not sure how much power these 10's will need, but the originals were 500 watts with 2 in each box. I think the singles had 250 watts?


If that's the case, wouldn't running the EP2500 in 4 Ohm bridged be way more than needed? Well, I mean wouldn't running it at 8 Ohms and 2 channels be plenty and not over work the subs or the amp?


I guess I'm thinking of how nice it would be if I could run just the front set for music if needed.

Maybe it just won't work. I have never used an amp like the EP2500.
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post #7 of 274 Old 08-27-2008, 09:24 PM
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12 each subs @ 250 watts each = 3000 watts.

EP2500 rated at 2400 watts 4ohm mono or 2x1200 watts @ 2ohms.

So you could alternatively run two boxes at 2ohms on one channel, and 2 at 2ohms on the other channel.

"The boom is dead, long live the bass"
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post #8 of 274 Old 08-27-2008, 10:09 PM
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Twelve of those 10s should be great!

I actually have 8 of these sitting in boxes waiting for me to finalize a design. I am planning on building 2 sealed boxes with 4 subwoofers each (probably at opposite ends of the box). When wired in parallel, each box will be about 2.5 ohms and each will be running on a channel of an EP2500.

I certainly won't be turning the gain up all the way because according to WinISD my cones are launching across the room if I give them too much power. The boxes are probably going to be about 4 cubic feet. On the TS parameters sheet, Jack recommends 1.278 cubic foot per subwoofer, but 1 cubic foot per subwoofer increases power handling without getting Q too high.

As for your build, there are obviously many combinations possible. You could do the four boxes you mentioned, which seems like the magical subwoofer number. You could also build two boxes, six in each, and put these between your main speakers or corner loaded at the front (or rear) of the room.

Have you played around with WinISD and these subwoofers much?
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post #9 of 274 Old 08-27-2008, 11:01 PM
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Erich,
It's best to not have to wire the boxes wired in series if they are separated with long wire runs.

What I have in mind would all be based on the woofers being wired in series pairs, 2 or 4 per enclosure.
Each driver is 12Ω nominal and when wired in series pairs they will handle the full output of the EP2500 running bridged(~96v), in an appropriate box.
The power will be evenly distributed across the woofers ~200W@.

Two towers ~full room height up font in the corners loaded with 4 drivers each, and two boxes with 2 drivers each distributed to even out room modes further.

I do believe going with the front towers over distributing boxes around the perimeter will help lock in the bass to sound like it's part of the font stage. A dual vertical array should also help with room modes vs lower perimeter placement

Like so:

Regards,
Dan
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post #10 of 274 Old 08-28-2008, 05:56 AM - Thread Starter
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Dan, I think that's a really slick idea. Would they cause issues sitting directly behind my front speakers? Heck, I could always get something to replace those ported rti-8's.

I have also considered shrinking down my screen size a bit if needed.








What if I built the box so that the the front is 13" wide. That would allow me to have the option of an array standing up on a small pedestal in the corner, or removing the pedestal and laying them along the front floor if needed for future placement issues. Maybe something like 13"x60" housing 4 subs each? I could make the pedestal and/or cap height whatever is needed to fill the corners.
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post #11 of 274 Old 08-28-2008, 04:53 PM - Thread Starter
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Quote:
Originally Posted by 1080c View Post


Have you played around with WinISD and these subwoofers much?


I did try, but I'm not sure how well I did. I need to work more on that.

THEN, today I got an e-mail from the guy at NHT that is selling these. He said he made a slight mistake and they didn't have 12, only 7.

So, he actually upgraded my order to the 083 model at no extra cost. I thought that was pretty nice as the unit is $10 more.

They are a little bit different, but not much. Here is the link to the actual specs. Honestly, the vast majority of this is a bit Greek to me right now.

Link:

http://home.comcast.net/~jhidley/Kli...I_Detailed.htm




In his email, he mentioned that if I went sealed, the recommendation was for 2 cu ft per driver. He also said "This will give you an anechoic -3dB point of 30Hz. Room gain will drop the -3dB frequency even lower."

Obviously I have multiple ways to wire them, but he did mention this, which I believe is along the same line as Neo Dan mentioned.

"wire the drivers 6 in parallel, then both groups in series ( 3.17ohms at DC) or 4 drivers in parallel then all 3 groups in series (7.15ohms at DC). The actual impedance will be much higher than these values."


I'd like to get started on these boxes this weekend if I have the time.

I have read about people porting these 083 models, is there any reason for doing that if I have 12??? Or should I just keep it fairly simple with sealed and lots of power?
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post #12 of 274 Old 08-29-2008, 08:27 AM
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I'm looking at the page linked in the above post... which set of T/S parameters should I be modeling with to model this driver?

There are T/S parameters listed for:
Large+warm
Large+cold
Small Signal

I started with the Large+warm (thinking this was large signal when the driver's warm) and things looked pretty reasonable until I noticed the FS of 10Hz... does that seem reasonable?

Any help would be appreciated!
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post #13 of 274 Old 08-29-2008, 09:11 AM
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4 per box 8'³ sealed is good
4 per box 10'³ @ ~15.75Hz via 1-6" x 28" port would be nice
Going ported would require a high pass filter the Behringer MIC2200 can do this and convert your RCA out to balanced line to drive the amp. It's goes for ~$100 or less.

Look in the excel file:
http://home.comcast.net/~jhidley/


Regards,
Dan
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post #14 of 274 Old 08-29-2008, 09:17 AM
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Lennon,

Please reread the 2nd paragraph on the sale page. For T/S modeling you need to use the T/S parameters located in the Excel spreadsheet.

Jack Hidley
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post #15 of 274 Old 08-29-2008, 10:16 AM - Thread Starter
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I've been thinking about this build for a few days now and I appreciate the extra help guys, I really do. One goal I was hoping for was to be able to run a lesser number of these for music. But I'm not so sure this will be possible because of the Ohms and the EP2500.

I suppose there isn't much difference whether I go 2 x 1200 at 2 Ohms or 1 x 2400 at 4Ohms?

If there is no difference, then I keep trying to get the fronts on one channel, and the rest on the other channel.



My only thought was this, which is taking a few ideas here and putting them together.

Using Neo Dans method for the front array. But only using 3 per box giving a 4 Ohm load to each. One on each side, wired to give me 2 Ohms.

Then have another set of 3 directly in the middle under the center channel, and the last box behind the seating area.


Each sub would be getting 200 watts, and I would have the ability to use the front channel for music, or both channels at the same time for theater.


I know it's more building, but that's okay.

Would that idea make any sense at all? I think I would feel a bit more comfortable being able to control 2 channels and have 4 Ohm boxes.
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post #16 of 274 Old 08-29-2008, 11:13 AM
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you could do it but I wouldn't recommend it.

what AVR are you using?

Do you have a balanced line converter or EQ that has balanced lines out?

Regards,
Dan
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post #17 of 274 Old 08-29-2008, 11:45 AM
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Erich,

Why do you want to use less subwoofers when listening to music?

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post #18 of 274 Old 08-29-2008, 12:16 PM - Thread Starter
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I have a Denon 987. I will be getting some type of EQ at least for the subs. The Denon does have preamp outs and line inputs per channel. It also has built in EQ's for each speaker as well. I haven't used that yet.

Jack, I will eventually be building my own fronts once I get a better handle on all of the lingo and learn more. Likely using some more of your speakers.

But right now I have Polk rt1-8's in the front, a CSi-3 for the center, and FXi-A4's for surround. I don't think they can keep up with all 12 subs for music. I normally have the sound mostly coming from the rti-8's for music.


Maybe this is just my own perseption, but for music I seem to like the bass coming from up front by the mains. I've been moving subs around in my room for about 6 months and while the back is definitely stronger bass in my room, once I put two 12" subs on the front wall, it just sounded right to me.


Because of the rediculous number of times I have moved subs, I'm a little worried about building this system and not having many options once built. I'd be pretty well locked down because of the unusual Ohm load for the different boxes and they would all need to be wired exactly one way for the amp. I'm not sure I could make much change in the room without rebuilding every single box.




One question I have never been able to find an answer for is pretty simple: Will I get the same solid music kick from 12 speakers running at 25%, or would it sound more solid running 6 at 50%? I would think that running all of them at a much lower volume would give you more of a muddy bass sound without the extra punch.
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post #19 of 274 Old 08-29-2008, 12:30 PM
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Does that Denon allow custom settings depending upon which source you select? If so, you could stay with the suggested four corner approach for HT via the DVD player, and then just the front corners with your mains for stereo music listening via the CD player. Not as easily selected if you are listening to SACD or DVD-A from the DVD player though, but those are normally enjoyed as surround sound anyway.
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post #20 of 274 Old 08-29-2008, 01:04 PM
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Where do you crossover now(subwoofer x-over in the AVR), do you run the mains fullrange.

Regards,
Dan
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post #21 of 274 Old 08-29-2008, 01:12 PM - Thread Starter
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The Denon does have 3 "User Modes". I have one set up for CD music, one for HT, and the other is for the tuner.

I have an amp that allows me to switch between 2 pairs of speakers (A+B). I have the A's set up with 2 15" sonotubes for HT and the B is set up for 2 12" ED 13ov.2's for music. Yes, I know I'm a sub nut!!

So right now I just turn on the reciever, hit the user mode to whichever, then pick the proper set of subs.


Having only the 15's on in the back while listening to music (or any sub in the back) makes it seem directional or disconnected because they are 22' away from the fronts not very good at all for music. But not a big deal for movies for some reason....sounds okay.



I guess that's why I am worried about not being able to turn off the rear subs for music. Maybe I don't need to worry. But if there's chance for issues, I won't know until after the build.
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post #22 of 274 Old 08-29-2008, 01:16 PM - Thread Starter
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Quote:
Originally Posted by NEO Dan View Post

Where do you crossover now(subwoofer x-over in the AVR), do you run the mains fullrange.

All speakers are set to small. Crossover is set to 80.

Dan, you mentioned that you don't recommend the four 4 Ohm boxes. Is this because of amp issues between 4 Ohm mono versus 2 channel at 2 Ohms?

Will I be heating my basement with this thing running at 2 Ohms??


Chances are, I won't be able to turn this thing up anywhere near what it can do. It would start buckling the plaster walls upstairs!
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post #23 of 274 Old 08-29-2008, 06:13 PM
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You should be comparing the difference between the responses of the two locations with the same sub woofers by moving the eD subs back to the rear and measuring/ listening for the difference.

If you MUST have 4 boxes buy 4 more drivers, still going with 4 drivers per box wired series parallel. I'd still run all or most of it up front, maximum one box in the rear. Most likely in the center position. probably down firing.

With your low SPL requirements I would consider getting a bassis, with the 12 or more drivers you should be able to tweak in a nice low end.

With subs up front you should be able to raise the x-over up to 120Hz or so, giving you more punch from the subs and taking the workload off the Polk towers.

Have you ever considered moving the Polk's out into the room further, and maybe a tad closer to each other. It may seriously improve your sound-stage, and allow you to run without the center channel. A huge improvement, imagine the sound coming out of the screen.

Regards,
Dan
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post #24 of 274 Old 08-29-2008, 08:10 PM - Thread Starter
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I will try to to move the Polks out farther from the wall then and see how that goes. I have been thinking that things are just too spaced out.

I have tried the ED subs in the back and I do get much more bass, but it doesn't sound as nice. There seems to be just one sweet spot in that back area, but it also sounds disconnected and very obvious to pin point it's location. So yeh, your idea of keeping most up front is definitely going to happen.


I believe I have a serious spike somewhere in the back. I can easily hit 115db with some quickly made 15" Sonotubes hooked up to an amp feeding 100 watts to each. Amp is set around the 10:00 location, not even half way up. Denon sub level is at '0'. They are 800-1000 watt subs. And I've got a decent amount of accoustic panels and traps up as well.


Just to be sure.

The idea of 1 box of 3 in each corner as you drew out earlier (sitting on a base to get it up higher).....then one box of 3 right in the middle under the screen......total of 9 up front....then one downfiring box of 3 in the back.......do you think that would be okay? I know it might not be ideal, but will I notice a huge difference with either of these methods:

9 up front, 3 in the back

or 8 up front, 4 in the back


Not that I'm all for looks on this, but the 3 per box trio up front might look pretty cool staring back at you too!

Tough decisions.

P.S.- I ordered the EP2500 today.
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post #25 of 274 Old 09-02-2008, 09:28 AM
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[quote=NEO Dan;14550401]4 per box 8'³ sealed is good
4 per box 10'³ @ ~15.75Hz via 1-6" x 28" port would be nice
Going ported would require a high pass filter the Behringer MIC2200 can do this and convert your RCA out to balanced line to drive the amp. It's goes for ~$100 or less.

Look in the excel file:
http://home.comcast.net/~jhidley/


Thanks for the link!

My math on figuring resistance is a bit sketchy (especially running 3 drivers per box). What are the wiring options for boxes of three drivers and what resistances do you end up with? I'm running some models in Unibox and need to know how much power each driver would be seeing.
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post #26 of 274 Old 09-02-2008, 10:39 AM - Thread Starter
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I've been doing the measurements for boxes of 3, 4, and even 6 per box to try and make this work the best (as in appearance too).

My reasoning for the 3 per box deal was also based on the thought that I might be moving in a couple years. Making a box that is roughly 80" tall might not fit at the next place. Granted I can just rebuild at that point.

I was using WinISD, but it was the free version and not giving me much data. So I did download Unibox and I'm currently running numbers in that. I seem to be getting an odd "max power input" figure. It seems very low per sub. I'll keep at it though.
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post #27 of 274 Old 09-03-2008, 09:22 PM - Thread Starter
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I think my subwoofers and amp will be arriving tomorrow.


I tried to do a few quick designs for the boxes and would like to get some feedback. I just started using SketchUp (as you'll soon notice) and tried coming up with a some different layouts. The cu/ft listed would be before drivers and bracing.


Any ideas on these?


4 in a sealed box:




4 in a ported box:




6 in a sealed box:




Or another idea I was thinking about:




Now that last one is intresting to me. But I'm not quite ready for the whole fullrange crossover deal just yet. However I thought that I could build a small recessed rectangle where the mids and tweeter would be.....big enough to slide a center channel or book shelf unit right into it. Maybe somehow allowing it to swivel and be directional? Okay, that might be a bit odd, it was just a thought.


Any comments are appreciated. And feel free to poke fun at my Sketch Up work too!
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post #28 of 274 Old 09-03-2008, 11:01 PM
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Looks good, Erich.

I modeled your boxes in WinISD and I would shrink the sealed boxes and make the vented box bigger.

The Q for the sealed boxes is around .714 if you take the 4 subwoofer box down to 6 cubic feet and take the 6 subwoofer box down to 9 cubic feet. The vented box gives you a better f3 if you take it to 14 cubic feet and tune it to 20 Hz.

See what NEODan has to say!

One thing to note...if you do 2 boxes of six you can put each box on a channel of the amp. If you do 3 boxes of 4, you'll be doing two boxes on one channel of the amp and 1 box on the other channel...it's not too big of a deal but something to think about.
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post #29 of 274 Old 09-04-2008, 12:06 AM
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1080c,

I think you are modeling the npt-11-075-2 woofers. Erich is using the npt-11-083-x woofers, which have a softer spider and therefore slightly different T/S parameters. The 083 should have a Qtc of about 0.7 in 2 cuft.

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post #30 of 274 Old 09-04-2008, 05:45 AM - Thread Starter
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Thanks guys. Those are sort of approximate values on size. I can't go much taller than 80". I could go a bit wider and I suppose a little bit deeper.

Sealed was my initial thought and it seems to be what the programs are recommending. But I would take the time to do ported as well, then again, box size may be a factor unless I stuff 3 in that 10 cu ft box versus 4.


I'm pretty excited about getting these things going!
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