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Discussion Starter #1 (Edited)
Well if I could kindly get some opinions from you guys here.
I'm about to embark on a speaker project which I am planning on using 4x 15" Tempest X's in a MTM type setup for my mains (4 way).
But my dilemma is I have modelled (win isd) these drivers with a sealed 80 ltr cabinet.
Well no probs but a hump starts to develope from between say 40-60hz.
I plan on using EQ in one form or another to flatten out this bump but can anyone else see any problems with my concept??

Btw the system will be active

Sorry if I knew how to add the graph here I would..:huh:
 

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I assume these are the first run of Tempest-X drivers, meaning you already have them? If so, you may want to reconsider the plan. 80 liters per woofer is far smaller than ideal for a sealed box using that driver. Ideal, ie Qtc of 0.707, is about 378 liters! 80 liters gets you a Qtc of 1.09. That's extremely high, and although power handling and efficiency will be excellent, perceived quality will likely suffer, as will the F3 point. In terms of magnitude response, the larger box will have 6dB more output for a given input power at 20Hz, and will have 3-5dB more maximum output available below 30Hz, using far less power to get there. Although, if you want maximum power handling, the small box will handle 600+ watts down to 3Hz. :)
 

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Discussion Starter #5
Unfortunately because these guys will stand about 2mtres tall I'm afraid anymore bulk caused by having boxes much bigger will be no go for me,that is unless I'm willing to become part of the singles scene again.:no:
I know bigger boxes would be the ideal for the drivers but I can't go there if you know what I mean.

So really I know that this is not the ideal solution for the Tempests,but is there any major negatives that I should look out for??:huh:

I tried modelling the 12"Shivas X's which did much better than the Peerless 12"s I was contemplating.
But very little gave me enough SPLs down to 30hz in sealed boxes,hence I'm going with the Tempests..

I really wanted to stick to 12''s to keep the width of the baffle down but I feel I have no choice, that is unless I go ported.Then it seems my boxes are growing again.

Aaron,what do you mean by perceived quality suffering??
 

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Unfortunately because these guys will stand about 2mtres tall I'm afraid anymore bulk caused by having boxes much bigger will be no go for me,that is unless I'm willing to become part of the singles scene again.:no:
I know bigger boxes would be the ideal for the drivers but I can't go there if you know what I mean.
Oh I know what you mean! My box is about 372 liters external size, and that's for one Tempest-X !

So really I know that this is not the ideal solution for the Tempests,but is there any major negatives that I should look out for??:huh:
...
Aaron,what do you mean by perceived quality suffering??
The major negatives are the 2dB bump in response centered around 58Hz and degraded transient response. These can give the speakers a somewhat boomy and inaccurate sound, where the bass notes tend to 'hangover' after the input signal has stopped. Also, group delay is significantly increased in the 30-60Hz range, which is rumored to be related to the perceived accuracy of a bass enclosure. All this may not be significantly objectionable in the case of the Tempest-X, given that the box resonance frequency is only 43Hz. I'd certainly be more concerned were this a 6.5" or 8" woofer, with a box resonance up in the 50-80Hz range.

The only way to really know how it's going to sound is to try it out. :)
 

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Discussion Starter #7
The major negatives are the 2dB bump in response centered around 58Hz and degraded transient response. These can give the speakers a somewhat boomy and inaccurate sound, where the bass notes tend to 'hangover' after the input signal has stopped. Also, group delay is significantly increased in the 30-60Hz range, which is rumored to be related to the perceived accuracy of a bass enclosure. All this may not be significantly objectionable in the case of the Tempest-X, given that the box resonance frequency is only 43Hz. I'd certainly be more concerned were this a 6.5" or 8" woofer, with a box resonance up in the 50-80Hz range.

The only way to really know how it's going to sound is to try it out. :)
I'm really hoping that with EQ I can pull that hump down and any other peaks in the room so hoping that should sort out any negaitives.
 

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Could he go with 2 18" PRs and just mass load them enough to be suitable for that size enclosure? I don't think he would be getting all of the benefit of the Tempest, so maybe go with the Shiva-X and 2x 15" PRs?
 

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Could he go with 2 18" PRs and just mass load them enough to be suitable for that size enclosure? I don't think he would be getting all of the benefit of the Tempest, so maybe go with the Shiva-X and 2x 15" PRs?
No, this wouldn't work either. A passive radiator enclosure is essentially a vented box, except with the radiators replacing the vents. Vented boxes are larger than sealed, for a given driver. Shiva-X would certainly be a better match. If you went sealed, 80 liters per woofer is ideal. It would have better response below about 28Hz, as compared to the Tempest-X sealed in 80 liters. 80 liters is still a bit small for a Shiva-X vented. You could still do it, and not have to worry about sound quality, though, but you will only gain about 2-3dB maximum output - though this is over both the Shiva-X sealed and the Tempest-X sealed. So, not a bad deal.
 

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Discussion Starter #11
Ok, even with boxes going upto about 120litres It seems this wasn't going to happen.
baaad Q !

May have to play with some 12's.
I really liked what the 15's could do,pity about the volume needed.
 

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Discussion Starter #12
Ok,this project has been scrapped.
the 15s just didn't want to play my game

But now the project has become 2x12"Shivas(facing front and rear) in one box about 100ltres.
Stay tuned for any progress.
 

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I'll be watching mate with great interest.
 

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Ok,this project has been scrapped.
the 15s just didn't want to play my game

But now the project has become 2x12"Shivas(facing front and rear) in one box about 100ltres.
Stay tuned for any progress.
I have been contemplating a similar design so I am interested in what you decide to do.

Mike
 

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Oh :)

I'd build four boxes! Place all on an array at front!
Nah. Multiple subs is a good thing but eventually you get to the point of diminishing returns. It is a lot more expensive (twice the amps, twice the cabinetry). It also gets hard to get the volume, phase, EQ, etc. correct the more subs you get in a room. The other problem you run into is unpredictable cancellations. I think two subs is great for me. Even if I built four subs, I would stack two of them in each placement location so I could keep calibration reasonable. It is pretty pointless for me to build more than two subs right now.

Mike
 
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