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Discussion Starter #1
i just picked up a 3000DSP and am planning two sealed 15's or a single dual opposed box. My first build ever sans the decware 10" deathbox i built for my car in 1993. Can you help me find some information like "dsp for dummies" that i can read?

From what i've been reading so far on here and on AVS I need to boost the low end of the drivers when in the sealed configuratio but i don't know how to do that. Do i need a linkwitz transform? do i boost at 25hz with a "wide q" and decrease the gain? ...i'm lost.

When i look at winisd and it shows 100db at 15hz but the transfer function graph is at -15db, does that mean i'm not really getting that output? It'd think 100db at 15hz would be pretty good.

thanks,

Pete
 

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A Linkwitz transform is similar to, but not exactly identical, a really low Q (wide) EQ band placed at a very low frequency (E.g. 10-15Hz). The goal being to only target the low end in order to make the overall response flat down to a target, like 25Hz, and then a specified roll off shape after that.

Some people say that "usable" response is the same as the -10dB point. I would say that for subs that can go even further since you will almost always have some level of room reinforcement. Being only -15dB at 15Hz sounds pretty rumbly to me.
 

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Discussion Starter #5
Thank you. I've been playing with the behringer software and it seems like it has linkwitz transform settings in there. So I think I'll carefully try out various settings. Any tips on where to start? Do I have to first limit the amps output to protect the drivers?

Thanks,

Pete
 

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That's great! I didn't know it could do a Linkwitz.

Will the limiter not work by itself or can you turn it down? I would suggest not setting the limiter to a lower than full setting, since the power demand on the amp will be very high down low once your Linkwitz is in place. As far as sizing the Linkwitz goes, it's a trade off between low extension and nominal SPL. Try something like an f0 of 30Hz and go from there.

Do you have measurement equipment to use REW?
 

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Discussion Starter #7
Actually I'm not sure if it can. It says linkwitz in some of the filters. I found this today on avs.

"Originally Posted by LTD02 View Post

"The only issue I have with my iNuke 3000DSP is the lack of any DSP functionality below 20 Hz. My subs need a slightly lower highpass than that...."

i believe that you can "wing it" with a combination of a 2nd order high pass and a low shelf with *negative* gain.

a second order high pass filter set to 20hz will have a -3db point at 20hz and will be down -12db at 10hz.

a high shelf 12db/octave (hs12) set to 20HZ will have a +3db point at 20hz and will be up +9db at 10hz.

together, these two filter produce the same thing as a second order high pass filter set to 10hz.

of course, you don't have to use 20hz for a 10hz net, you can set both filters for 30hz in order to achieve a 15hz high pass net.

the only downside is that the noise floor will be higher, which may not be a problem."

I've got my cuts sheet ready a d will begin building next week. Woot. Box will be 24h x 16w x 22l. 1.5" baffles and .75" everywhere else.

Thanks

Pete
 

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Linkwitz-Riley is a type of slope shape for HPF and LPFs, it's not the same as a Linkwitz Transform (LT) which is more of a low end shelf.

I have been looking into how to do an LT with the inuke DSP. The place to start would be with varying levels of the LS12 filter at maybe 20-25Hz.

You can use WinISD to compare several PEQ bands to mimic the shape of an LT. You can get pretty close. Unfortunately WinISD doesn't have shelf filters like the inuke has. With the shelf effect the inuke should be able to get really close to the same filter gain and phase response as an LT, it just might take some extra work...
 

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Discussion Starter #9
Gotcha. You answers my next question which was going to be about how to model the ls12 in winisd!

Thanks

Pete
 

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Discussion Starter #12
Thanks man. So no rolloff below 20hz to worry about? Think I should hpf at 20hz along with the ls12 or alternate potato?

I am obsessed.

Pete
 

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I believe I've set mine at the quote from ltd but can someone confirm as the a possible screen shot or as to which tabs on the dsp setting should be adjusted. Here is what I did a while ago. On the filter/xover tab I set the highpass at 20hz with a buttersworth at 12db. On the paramedic eq tab I set a HS12 at 20hz with a -5db gain. Is this correct or do I need to do Something a little more or different to achieve a lower than 20hz filter. I think was doe to get me around 15hz. Let me know thoughts or if there are other ways
 

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Discussion Starter #17
You shouldn't have the xover setting at anything. Your reciever would do that. You make the hpf in the EQ page by doing a hs12 with -gain and the you bump the overall gain on the xover screen by adding in the equivalent positive gain. I didn't need to do this at all because my subs are sealed. I assume this is a ported sub? I can't do screenshots because the software only shows 20hz so the effective filter is to the left of where you can see on the screens.
 
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