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Discussion Starter · #1 ·
Actually, I lost my hair many years ago, but if I had hair, I'd be losing it!
I promise; I did my due diligence.
I've been all over this site, the Helix DSP tuning "magazines", Andy's tuning guide, consulted clergy and medicine men, etc, and the more I dig, the more confused I'm getting. Seems like there's a million ways to do this, and it seems like there really ought to be something approaching a few "best" or at least better ways.
I had no problem setting the input gain on the DSP (.wav 0dB 1kHz mono sine tone, 9'10ths max HU volume with all bells & whistles flattened, neutralized, or off, turn up gain until clip light comes on, back off until it turns off), and if i simply had a HU and amp: same HU setup except volume at max, true RMS voltmeter connected across speaker output, turn up gain until you get the square root of the product of rated power and speaker impedance (strangely, there was an MTX video where the guy showed an equation of the square root of PR, so I'm kind of wondering if either he screwed up, or maybe I'm spota use the product of rated power and the DCR of the driver?) in DC volts. Other than that bit of confusing data; easy.

Where I'm getting confused is in the proper point (and procedure) in which to set up amplifier gains with a DSP. Firstly, I have 5 gains; 1 for each bridged channel for the mids, 1 for the sub (this is the 900/5 amp), then 1 each for the bridged tweeter channels (the 400/4 amp. Overkill, I know, but this is temporary, until I get the OEM speakers back in the rear door. They're not bad sounding at all, and they're just for rear fill, and simplify the Hell out of all this, being full-range. In the interim, I just turn the gains way down on this amp, and never have to worry about sending a clipped signal to these expensive tweeters).

The confusing part: if I set up the amp gains from the DSP first, then do all the DSP-ing, it seems to me that I'd have to set the gains again after the DSP-ing, to account for all the dipping and possibly a bit of boosting. Resetting the gains then changes the response, especially because I have all of these gains going to the sub, mids, and tweeters, so I'd have to go back and RTA-EQ it again, then re-set the gains, then RTA-EQ it again, etc, etc....
It's really no different, in my mind, if I do the DSP-ing first, except that maybe this is a less-safe way of doing things.
Is there anyone who can shed some light on this for me?
I'd be extremely grateful!
 

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You do not need to "set the gains" from amplifiers at all unless you need those to output more power.

That DSP outputs 6v, Your amps accept 8v into its inputs, so you get roughtly 3/4 of the max power when gains are at "zero" position.
 

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I agree. If the the amp gain us at "0" there's minimal chance of the the amp putting out a distorted signal. Set the levels in the dsp using proper crossovers and such. That's a whole other basket and there is very good tutorials on here for initial dsp tuning.

Amp gains don't ever need to be touched if you have enough volume. They are there just to match/compensate the input voltage.
 

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Discussion Starter · #4 ·
Yes, ive got printed copies of the tutorials, and the Helix "DSP PC-Tool tuning magazines. Ive read them, and havent had a problem understanding about 98 % of the DSP tuning portion. What i dont understand is why JL Audio, in their manuals for these amps, says to use a test tone and turn up the gains until the clip light comes on, then back off, (or use a voltmeter) if the gain knobs were intended to be left at zero? Dont get me wrong; im a fan of a conservative approach, especially considering what ive spent on all this gear, but im also pretty deaf from years of automatic weapons fire in enclosed spaces, RPG's, mortars, breaching demo, etc, and would like to be able to turn it up a bit when im driving her car (its actually a present for my wife).
 
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As I said if there's not enough volume, adjust responsibly.

JL says that to teach people how to adjust safely if needed opposed to using as a volume control.
 

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Discussion Starter · #7 ·
As I said if there's not enough volume, adjust responsibly.

JL says that to teach people how to adjust safely if needed opposed to using as a volume control.
Thats exactly what im trying to learn. At this point, doing so with a DSP seems much more complicated than it appears to be with just a head unit.
 

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For me. I set (find out what is) the HU at it's max volume before distortion (3/4 volume rule of thumb). I then set TA and crossovers in the DSP. I make sure everything is off/flat on the amp and set the amp gain at that point. All further adjustment is done in the DSP.
 

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set you gains the jl way, using a 0db tone will leave your amp with a decent bit of head room, most people will use a -3 or -6db tone to give themselves more volume, as most music almost never hits 0db. with this headroom, you should be safe to eq as long as you dont use any huge boosts. the response of your system will be the same regardless of volume, and therefore gain, theoretically, however in the imperfect world of car audio thats only close to true, due to reflections and nulls and what-not. do the tuning at the volume youll do your critical listening at, when youre "jamming out" you wont care about fidelity as much, and when you arent paying much attention to it and have it down, same thing.no reason to bridge your tweeters, so you can use 2 channels from your tweeter amp for the rears when they go in. there are different schools of thought on rear speakers, with 2 channel fidelity saying to either dont use them, or use them bandpassed, low volume, and with a bit of delay, so that they seem like an echo, making it sound as though youre in a music hall and the performance has some reflections, a lot of people less deep in the hobby though, just want to be "surrounded" be the music, and these people often enjoy rear speakers.
 

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Thanks for asking this question. I’ve got the exact same issue since I got my jl amp and dsp.3 installed. So it sounds like the consensus is for Helix to J:

1. Set input sensitivity on helix, set crossovers, eq flattened.

2. Then set the gains on the Jl amp(s) according to JL’s instructions with a DMM (which will probably need little if any gain).



Edit: just so no one gets confused I altered this to the correct way.
 
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This is the basic flow I use.

Find max undistorted output from your head unit with the sub output set to max ( if using sub out on head unit ) using test tones , I use -5db for mid/treble and 0db for the head unit max output , -10db for the subwoofer.
Feed this signal to your DSP and adjust the input sensitivity so as not to overload the input stage.
DSP all flat , crossovers set to the correct frequencies and DSP channel levels adjusted for the highest maximum undistorted output.
Feed this to your amps and adjust the gain so the output is maximum before clipping.
All amp gain settings now don't need to be touched again.
All your levels are now set in your DSP while tuning.

Also I never boost when tuning only cuts otherwise you can run into gain issues.

I personally only ever use an oscilloscope for this , to me this is the only way to do it properly and to not be guessing but I am an electronics tech so I have always had an oscilloscope handy even in the days when they were really expensive.
 

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yes, as above, tune to max clean on each piece of the signal chain, in order from source then next in line all the way back to the last amp, then once thats done, do your eq. again, if you set gains with a 0db, youll have plenty of headroom even for small boosts (sometimes its easier to boost the problem low than to lower everything else to match it)
 

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This is the basic flow I use.

Find max undistorted output from your head unit with the sub output set to max ( if using sub out on head unit ) using test tones , I use -5db for mid/treble and 0db for the head unit max output , -10db for the subwoofer.
Feed this signal to your DSP and adjust the input sensitivity so as not to overload the input stage.
DSP all flat , crossovers set to the correct frequencies and DSP channel levels adjusted for the highest maximum undistorted output.
Feed this to your amps and adjust the gain so the output is maximum before clipping.
All amp gain settings now don't need to be touched again.
All your levels are now set in your DSP while tuning.

Also I never boost when tuning only cuts otherwise you can run into gain issues.

I personally only ever use an oscilloscope for this , to me this is the only way to do it properly and to not be guessing but I am an electronics tech so I have always had an oscilloscope handy even in the days when they were really expensive.
I'm not sure I understand how you set amp gains with XOs enabled...Are you using tones that are the center of each passband? Presumably, in a classic XO scenario, let's say 80-400-4000, the standard 40Hz tone would only come through the sub and the 1KHz tone through the midrange.
I've always set amp gains without XO, so I'm very interested to learn a different/better way.
 
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I'm not sure I understand how you set amp gains with XOs enabled...Are you using tones that are the center of each passband? Presumably, in a classic XO scenario, let's say 80-400-4000, the standard 40Hz tone would only come through the sub and the 1KHz tone through the midrange.
I've always set amp gains without XO, so I'm very interested to learn a different/better way.
It would seem to be slightly better to do it your way (no crossovers set) because that allows you the freedom to dial the crossovers in however much you want at any time down the road.

On the other end though, with the crossovers set, the drivers would be pushed to their highest possible spl.
 
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It would seem to be slightly better to do it your way (no crossovers set) because that allows you the freedom to dial the crossovers in however much you want at any time down the road.

On the other end though, with the crossovers set, the drivers would be pushed to their highest possible spl.
Right, and as I said, I'm open to learning a new way. I just don't understand the mechanics of how it's done. If you're setting gain for a Midbass amp with XOs from 80Hz to 400Hz, the classic 40Hz and 1KHz tones would be so attenuated as to be useless. Do you then use 40Hz for sub, 250Hz for MB, 1Khz for MR and 8Khz for TW, for example?

I must be missing something obvious here...
 
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Right, and as I said, I'm open to learning a new way. I just don't understand the mechanics of how it's done. If you're setting gain for a Midbass amp with XOs from 80Hz to 400Hz, the classic 40Hz and 1KHz tones would be so attenuated as to be useless. Do you then use 40Hz for sub, 250Hz for MB, 1Khz for MR and 8Khz for TW, for example?

I must be missing something obvious here...
I don’t know if this is correct or not, but for my two way systems I set the crossover and then set the gain using all the tones in the spectrum I want them to be playing.

So whatever tone comes in with the most power, that’s the one I set it at. I haven’t done it in a year but I remember using a phone app and you can quickly find the most powerful frequency.

The reason I do this is because on a couple occasions I’ve used the 1k tone and then noticed an area near that - like 1600 or 2000 - was much higher and peaking on the RTA (which could have been a number of other factors too). But that’s my superstitious ultra careful way of doing it.

Im definitely down to learn any best practice techniques though - especially if it is of benefit.
 

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Sorry , I shouldn't have said all crossovers , the sub and midbass I have with with no crossover when I'm setting the gain but I do definitely have the crossover set for the tweeter.
Also sub bass level is set with your head unit if you are using sub out , if not then it's done in the DSP.

The tweeter gain on the amp is usually set to minimum as the tweeter requires way less power than midbass and sub.

The max unclipped signal is used for the sub and midbass only.

I usually use 40hz for sub and 500hz - 1khz for midbass gain settings and 1khz for the head unit max unclipped output , but I also do check the head unit at 40hz/500hz and 10khz just to make sure the levels are the same at all frequencies.
 

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Sorry , I shouldn't have said all crossovers , the sub and midbass I have with with no crossover when I'm setting the gain but I do definitely have the crossover set for the tweeter.
Also sub bass level is set with your head unit if you are using sub out , if not then it's done in the DSP.

The tweeter gain on the amp is usually set to minimum as the tweeter requires way less power than midbass and sub.

The max unclipped signal is used for the sub and midbass only.

I usually use 40hz for sub and 500hz - 1khz for midbass gain settings and 1khz for the head unit max unclipped output , but I also do check the head unit at 40hz/500hz and 10khz just to make sure the levels are the same at all frequencies.
Ah, that makes perfect sense now. Thank you.
 
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Discussion Starter · #19 ·
yes, as above, tune to max clean on each piece of the signal chain, in order from source then next in line all the way back to the last amp, then once thats done, do your eq. again, if you set gains with a 0db, youll have plenty of headroom even for small boosts (sometimes its easier to boost the problem low than to lower everything else to match it)
Thank you all for your time and effort with helping me out! This was definitely seeming like a bit of an enigma for me.
Just two questions: I was setting my crossovers, initially, according to the manufacturer's recommendations, as well as Andy's, so 50-4000 on the 650s, 1400-up for the Piccolos, and 20-150 or so for the sub (I wonder if I should set the low end of the sub just above the driver/enclosure's calculated frequency of resonance?), 24 dB/octave Linkwitz for all, then when it comes time for the first setting of all crossovers, adjusting frequencies at points of overlap to eliminate waveform interference that causes dips or peaks (in direction of within drivers' frequency responses, of course, especially tweeters').
Are you saying to adjust EQs of drivers before amp gains are adjusted, and then again afterwards, or just after amp gains are adjusted?
I am using subwoofer output from HU: should I set this to max both when setting the DSP's input sensitivity and its amp gain (and presumably while setting the EQ), or just with gains, then back to null when doing EQ?
 

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Yes , head unit subwoofer output at max when setting all gains then while tuning you can adjust the subwoofer level in the head unit , don't touch the physical gains you set earlier.
Set gains before adjusting any eq , don't touch the physical gains once set then do your tuning and levels by adjusting the DSP.
 
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