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      09-25-2014, 12:46 PM   #1
Hopeful
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Before I start my Helix DSP RTA...

I have installed the Jehnert Flatline complete set and retained the OEM rears (for rear PDC). The base audio has not been recoded to HiFi. I have installed the Helix DSP and an XD600/6.

Before I start tuning the Helix DSP, using the Audiotec Fischer app, I was hoping for some advice on initial settings for the amp and DSP.

Amp
I have the gains set at 8 o'clock for the front components, minimum for the rears and 10 o'clock for the under seats. I will turn all filtering off and set the amp to 6 channel mode. Is that all OK?

DSP
What should I set the crossover frequencies to for the components (using Jehnert crossover), OEM rears and under seats and what slope?

Thanks in advance,
Colin
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      09-25-2014, 01:11 PM   #2
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I wouldn't amp the rears. Plus, if you get what I did, those tones will be annoyingly loud.

Two things I'd consider...
Channel 1&2 for tweeters and disconnect the Jehnert crossover
Channel 2&4 mids
Channel 5&6 8" woofers

OR

Channel 1&2 tweeter/mids with the crossover connected
Channel 3,4,5&6 for 8" woofers bridged

Try sending 300hz on down to 8" and 300hz up to the rest depending on which configuration. Should be a decent starting point.
If you delete the crossover, send 300hz-4k to the mids and 4k-16kish to the tweeters.

One thing I learned the hard way, (I used Jehnert's door boards so what I've stated may or may not apply) the left woofers (300hz on down) needed over 3ms of delay compared to the 1.4-1.5ish ms of delay for the left tweeters/mid to get things close to center for me.

I'm unaware of what the slope is for the Jehnert crossovers (12db? 24db? I didn't use the crossovers since I'm fully active on the tweeters) But be open to flipping the mid's phase 180 degrees if the crossover slope is steep enough.

Last edited by Wongway; 09-25-2014 at 01:18 PM.
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      09-25-2014, 01:20 PM   #3
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Thanks. I am NOT ripping the car apart again to run another wire for each tweeter though.

As it stands at the moment, the rears sound OK, i.e gongs and rear PDC are all fine. The under seats are also plenty loud enough, why would I want to bridge?
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      09-25-2014, 01:38 PM   #4
Wongway
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If you bridge them, you'll give the 8" a much easier easier time of hitting low notes. Conventional theory is that subwoofer frequencies (below, say, 150hz) requires considerably more power than regular speakers. So in a sense, you'll allow them to work better.

But honestly, get rid of the idea to amp the rears.

Also, the logical question comes to mind...
Why would you spend all that $$ and wasted power to speakers you will never hear or listen to? You bought it, so make sure the speakers you did buy and upgrade get the power they need to do their jobs well.

edit:
Oh yeah, if you decide that I can go fly a kite, screw it, you'll leave your rear speakers amped:
Make sure when you start doing the time alignment that you fade your rear speakers completely out. It'll mess with the front staging if you leave them on.

Last edited by Wongway; 09-25-2014 at 06:48 PM.
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      09-26-2014, 07:26 AM   #5
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Colin, I may be able to help I am running the helix dsp, but from a oem hifi head unit, so I have front and rear full frequency inputs. What is your input arrangement?
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      09-26-2014, 11:21 AM   #6
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Quote:
Originally Posted by cdgatti View Post
Colin, I may be able to help I am running the helix dsp, but from a oem hifi head unit, so I have front and rear full frequency inputs. What is your input arrangement?
Thanks - is this what you're after?

Input (High level)
A FL Full
B FR Full
C RL Full
D RR Full

Output
A FL Full
B FR Full
C RL Full
D RR Full
E FL Woofer = FL Full + RL Full
F FR Woofer = FR Full + RR Full
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      09-26-2014, 04:48 PM   #7
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That looks good, I assume you mean on the input/output matrix on the first line for example you have FL full--->FL full with all other boxes marked 'not used'. If so that looks good. Do you know if your inputs are full signal? I thought the outputs on the base head unit were heavily equalized.
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      09-27-2014, 04:23 AM   #8
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Yep, FL full--->FL full with all other boxes marked 'not used'

I haven't re-coded so they will not be full signal (but there isn't a label for equalised )
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      09-27-2014, 07:28 AM   #9
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Quote:
Originally Posted by Hopeful
Yep, FL full--->FL full with all other boxes marked 'not used'

I haven't re-coded so they will not be full signal (but there isn't a label for equalised )
Where did you grab the inputs from? If you didn't grab the signal to the underseat woofers you may not have the necessary low frequencies represented.
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      09-27-2014, 09:15 AM   #10
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From the I-drive HU. I always thought that re-coding to HiFi wasn't essential if using a DSP. Is that not the case then?
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      09-27-2014, 10:15 AM   #11
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I have the MatchPP82DSP, so maybe I'm mistaken, (I assumed all the Helix DSP worked similarly), you take the full range signal from the source and it cleans it up for you... Shouldn't need to recode the head unit...
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      09-27-2014, 12:13 PM   #12
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I would think it would give the DSP more range.

I would think it would give the DSP more range
since it didn't have to work to compensate for the
unflat signal . Also it might improve the signal to noise ratio.
The guys that have some real expierence with this might
chime in .
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      09-27-2014, 04:19 PM   #13
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The helix dsp doesn't re-equalize the inputs like say a JL clean sweep or the like. If the inputs are not full frequency you will end up needing excessive equalization on the outputs. You can however combine inputs, for instance if you could take the left fronts and the left underseats add them to one row in the matrix and you should have most of the frequencies represented, they just may not be flat if the head unit compensates for the the bad speakers and lack of tweeters like the base head unit.
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      09-27-2014, 11:02 PM   #14
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Learn something new... my match 82dsp flattened the signal I pulled from under the seats just fine. I always assumed the DSP did the same.
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      09-28-2014, 01:34 AM   #15
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Quote:
Originally Posted by Hopeful View Post
From the I-drive HU. I always thought that re-coding to HiFi wasn't essential if using a DSP. Is that not the case then?
With HiFi, nothing else is needed as it is full range and flat.
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      09-28-2014, 01:35 AM   #16
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Quote:
Originally Posted by Wongway View Post
Learn something new... my match 82dsp flattened the signal I pulled from under the seats just fine. I always assumed the DSP did the same.
Ahh but it didn't. It will put out, exactly what is put in, prior to tuning.
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      09-28-2014, 11:44 AM   #17
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I will bear a recode to HiFi in mind but I'd still appreciate some advice on the crossover points and slopes for the flatlines (using their passive crossover for the mods and tweeters)
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