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When I'm adding filters with my BFD to acheive the target curve, be it a flat response or house curve, do I need to concern myself with the affect those filters will have on my cone excursion? With my current PB13's I've filtered away to acheive my curve with no thought toward cone excursion, and I've never had and issue. But, as I model my DIY build I notice any filters I apply send my excursion above the X-max.
 

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Yes, you need to consider this especially if you are adding boost. Each +3db of boost will demand twice the power from your amplifier at the boost frequency... you also need to consider your amplifier's output capacity to avoid driving it into clipping due to applied EQ.
 

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With my current PB13's I've filtered away to acheive my curve with no thought toward cone excursion, and I've never had and issue.
The PB13, if it's like most of SVS' other subs, has built-in limiters.

But, as I model my DIY build I notice any filters I apply send my excursion above the X-max.
Is the program taking into consideration the size of your room, and whether or not you will require maximum output from the driver and/or amplifier at the levels you intend to use? I have a hard time believing that you'd go through the trouble of building a DIY sub that's less capable than your SVS...

Regards,
Wayne

 

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I will have to keep an eye on my dual 18" FI Q18's then as I have applied 8db of boost at 33hz as there was a dip at that frequency. I do get a better response if I angle the subs inwards but then it doesn't sound as good bass wise. I have not seen any problems yet but I guess it would make sense to play a 33hz test tone. Would that tell me if it is too much?

That is the only boost I have applied. The other 6 filters were slight cuts so I guess also I will still have alot of headroom.

My amp is the EP4000.


cheers

Graham
 

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Discussion Starter #5
I'm modeling with WinISD which doesn't take into consideration room size, as far as I know.

I did use the maximum output of the amp, 2000W, as part of the model, a Behringer ep4000. The available headroom may be why the Exodus Audio application sheets for their Maelstrom 21" show the excursion at 50mm even though the X-max is 32mm. But if you had significant boost in there it would be easy to reach 2000w.
 

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Corock,

I don't listen to music of watch films below -20db on the MV on the onkyo which should leave loads in the tank of the EP4000 for that boost I have applied. The other thing I guess to think about is that say with a boost at the 33hz I have applied how often will you get a constant tone of that frequency when watching films and playing music. Not alot really maybe a split second or two.

cheers

Graham
 

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The other thing I guess to think about is that say with a boost at the 33hz I have applied how often will you get a constant tone of that frequency when watching films and playing music. Not alot really maybe a split second or two.
Explosions and other low-freq noise on movie sound tracks are typically fairly broadband, similar to something like bass-limited pink noise.

Regards,
Wayne

 

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What you need to remember is that EQ can never force the speaker beyond xmech (damage=bad) or the power output capabilities of the amp (clipping= also bad but not near as bad as severly bottoming out your driver).

Look at your modeling and input the maximum amount of power that you could expect the amp to ever put out. Does it cause the driver to exceed xmax? Xmech in the intended pass band? Don't worry about below the tuning if it's ported. If it doesn't exceed the drivers physical limits then don't worry, your amp will clip first. If the driver does exceed it's limits at some range of frequencies then yes you could run into severe trouble if you push the sub too hard, but that assumes that you are EQ boosting in that range, which you may not be.

If the sub is sealed you can control this somewhat with the enclosure size. If your amp is capable of overpowering the driver mechanically in modeling then you can reduce the box size somewhat to help limit the cone excursion. This is not going to allow a cheap 10" to survive the brunt of a 2000w amp. Think of it more like a fine tuning than a gross adjustment.

Also remember that in the real world there are all sorts of losses that will help keep your driver safe. There is compression, suspension tightening, loss of BL, thermal heating, amp not meeting it's full out specs, ac line sag, fact that content is usually a complex large bandwidth signal, etc. Things are not perfectly linear like winisd assumes they are.
 
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