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EQ Advice Sought

2K views 10 replies 2 participants last post by  srosenberg 
#1 ·
attached is a WinISD file for a build i'm considering - TC Epic 10 in a 14.5L sealed box. The amp i'm thinking of using (SVS) is 400W, though there is also a nice alternative (XTZ) at 200W.

at 400W, the EQ i've come up with is a 2 db boost at 40 hz with a Q of 0.7. this yields an F3 of 47.1. a 3 db boost will drop that to 43, but cone excursion is getting close to the Xmax.

at 200W, the EQ i've come up with is a 5.5 db boost at 40 Hz with a Q of 1.7. this yields an F3 of 36.7, albeit with 3 db less output than the 400W model.

i was hoping to get some suggestions on how to better EQ this build than what i came up with above... any inputs would be appreciated!
 

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#3 ·
Hi Mike,

thanks so much for the inputs - VERY helpful. are there general guidelines one should try to follow when considering how much boost or cone excursion (relative to xmax) to employ?


how much boost (db) in the 30-40 hz region is advisable (assuming the xmax is not exceeded)?

what amount of excursion (relative to xmax) is advisable to stay within?
 
#4 ·
Boost is all about the available amp power, most amps can provide over their rated power for a short duration. If you are demanding too much from the amp then it will clip. The best scenario is to have more power then you need. If a driver needs 400 watts and you are boosting 3 db somewhere in the frequency range then a 800 watt amp would be able to provide the needed power.

In your case you can try 3 db of boost and see how the amp handles it. If the amp clips then you can reduce the boost.

As for excursion, ideally you can take it to the drivers rated Xmax.
 
#5 ·
mike, again, thanks for the advice - i can't tell you how helpful you've been (this is my first build). sorry for the string of rookie questions - regarding 'having more power than you need'... doesn't this result in reaching the Xmax of the driver earlier?

the reason i was considering the 200 watt amp is that i found with some drivers, when i enter 400W as the System Input Power in WinISD, the Xmax is quickly exceeded - sometimes with just a little boost, sometimes with no boost at all.

since the box i'm building is small, i've found a boost in the 40 hz range to be necessary to get decent extension. for some drivers, like the TC Sounds Epic 10, this is no problem... 400 W and a 3 db boost at 40 hz still only results in a peak cone excursion of 17.1mm with an Xmax of 18.1mm.

however, for other drivers with more limited Xmax specs, the cone excursion will exceed the Xmax when 400 W is modeled even with no boost added... for those, i thought there was no choice but to use a lower powered amp to enable some boost without exceeding the Xmax... see attached WinISD file.

is this thinking incorrect??
 

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#7 · (Edited)
yup... i realized i uploaded the wrong file a few minutes ago. there are sub woofer drivers which have similar limitations - that is, bumping into Xmax when modeled with 400W either with a little boost or none at all. the tc epic 10 and seas l26r04Y seem to offer the best balance of performance in a box the size i'm working with... both can take 3 db boosts and 400W w/o exceeding their XMax. the Peerless XLS10, which would be fantastic for it's shallow mounting depth, but can only take a 1.5 db boost before reaching Xmax. likewise, the 9" morel uw958 would be great for the small size of the driver, but has even tighter limitations where power / cone excursion is concerned (225W with no boost gets it to the Xmax).

it's just a matter of finding the driver with the right combination of attributes.

i found a thread from march where a build was proposed using the epic 8 and a 10" passive radiator... i modeled it using dual CSS 10" PR's and it was pretty incredible. switching to the 8" Seas PR brought the performance down a bit, but it still looks amazing on paper.

attached is the file... are these designs less suited for music use than a sealed sub (without a Qtc to check, i'm having a hard time telling how these would compare to a sealed box with a Qtc of ~0.65 where 'tightness' is concerned). if the group delay is the variable that correlates, there's no comparison between the sealed designs and the PR designs - the sealed boxes never get out of the high teens, while the PR boxes exceed 25ms by 30hz. there's a good read on the subject here for anyone interested and some more great info here.
 

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#8 ·
From doing a lot of reading it appears that sealed is the way to go for music although personally I like my ported subs since the majority of music that I listen to is hard rock and roll. I guess it just depends on what kind of music a person listens to and what the preferences are.

Your modeling of the Epic 8 with dual PR's looks impressive for a 10" cube, now you got me thinking of a sub for my computer system!
 
#9 ·
Your modeling of the Epic 8 with dual PR's looks impressive for a 10" cube, now you got me thinking of a sub for my computer system!
mike, don't break out your checkbook just yet... in reviewing things, i don't think this is going to work, as the PR cone excursion is well beyond the Xmax. the 8" PR's i've found have xmax limits around 9mm - 11mm, while nearly double that is required. moving up to a 10" PR might be necessary, as those offer Xmax's in the 26mm - 28mm range.
 
#11 ·
with the 10" passives, things look really nice in WinISD. even better with the Epic 10 or Seas R04Y - since the box needs to be tall enough to allow for 10" passives on the sides, i can work a 10" active driver on the front instead of the 8". nice.

the issue i'm finding is group delay... what do you generally shoot for in group delay for a 'tight' musical sub?
 
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