REW and System Baseline Tune Help

[dumdum]

jtrosky some really helpful info here. I've had a chance to read the Audiofrog tuning guide posted above and have made the decision to go to the 24dB slopes as you suggested. And interesting that there's a ~5dB dip very close to my crossover point... Also I've been studying Nick's guide on the auto-EQ function and will be using that to get a solid tune that I can enjoy for a while.

I like your idea of measuring each speaker individually. It seems like a great way to let the auto-EQ do its thing. My USB extender cable came today so that means I'm ready to make more progress this weekend and will report back here on how things are going.

I am looking forward to playing with the tune quite a bit afterwards to dial in the sound better, but also learn. Thanks again for everyone's help on this!

Auto eq is automated and literally applies a global eq over the channels I believe, but watch nicks video for more info

measuring individual speakers is handy so you can see they are in phase at the crossover points and sum correctly (you will get six dbs of summation throughout, so a pair of lr24 crossovers in phase will give a flat response as the crossover point is the -6db point for both sides so it sums as flat, butterworth is the -3db crossover point so it sums with a 3db hump, so you can then part the crossover to flatten the hump a little, it’s handy if one side or the other has a dip at the side of the crossover freq to flatten the response when summed

also you can play one side mid for example, then the other and see how they sum when played together, again if phase and timing is good you will get 6db of summation, this can reveal phase differences between sides also and if timing isn’t perfect as it will put equally spaced dips (comb filters) into the summed response

You can use rew with its auto eq feature on individual drivers and that can then be imported into the helix software also

there's lots to learn and take in, but give it time and it does get clearer and easier to do

[jrwalte]

also you can play one side mid for example, then the other and see how they sum when played together, again if phase and timing is good you will get 6db of summation, this can reveal phase differences between sides also and if timing isn’t perfect as it will put equally spaced dips (comb filters) into the summed response

I'm sure 2 speakers playing together would be a 3dB boost not 6?

On the helix auto EQ, you can do each speaker individually. You'd have to create your acoustical EQ curve for each speaker set (woofer, mid, tweet, etc) to get the auto EQ to EQ the speaker to its correct curve. Then auto EQ as a speaker set, and then all left speakers and right speakers, and then finally, all speakers. That's a lot of steps and a lot of house curves you have to switch around. But it would get you the best results and follow the same steps you'd take with a manual EQ tune. Nick's point on the auto EQ is you can get a good enough tune by doing all left, then all right and then globally. And that most people wouldn't notice the difference from that and a more advanced tune.

Also a point to make that I noticed using auto EQ. Once you start the process of auto EQing sets of speakers, which should have a summed 3dB increase, you need to increase the reference curve to match up to the new increase in output. Otherwise, you'll tell the auto EQ to EQ out the 3dB increase it is getting from the summed output.

[Jdunk54nl]

I'm sure 2 speakers playing together would be a 3dB boost not 6?

I think it should be 6...you double the speakers for 3db and you doubled the power for 3db.

[ckirocz28]

I think it should be 6...you double the speakers for 3db and you doubled the power for 3db.

That^ is correct.

[jtrosky]

I could have sworn that I only saw ~3dB increase in level when measuring left+right compared to just left or right with REW?

[Jdunk54nl]

Someone please correct me if I am wrong.

But if you see only a 3db increase and not 6db with double the power and double the speakers, that should mean that the speakers aren't 100% in phase with each other. They would be somewhere between 0 and 180 degrees out of phase. In other words, not completely in phase, but also not completely out of phase.

[SkizeR]

Someone please correct me if I am wrong.

But if you see only a 3db increase and not 6db with double the power and double the speakers, that should mean that the speakers aren't 100% in phase with each other. They would be somewhere between 0 and 180 degrees out of phase. In other words, not completely in phase, but also not completely out of phase.

Yup. Probably caused by reflections

Sent from my SM-G975U using Tapatalk

[jtrosky]

I'll have to double check the measurements with REW. I don't remember seeing a 6dB increase when playing both speakers - could be wrong though - didn't pay close enough attention to exactly how much higher the measurements were when playing both speakers - just checked to see that response stayed the same across the frequency range - and was higher. I can't imagine that the speakers (all three sets - dash, door and rear-deck) could be out of phase the same amount - I mean the physical polarity is definitely the same on them and time alignment is set properly, so just can't see how they would all be out of phase by the same amount like that.

I'll take some new measurements today and confirm if they are ~3dB or ~6dB higher when playing both left and right and go from there. Who knows, maybe there is some issue with my system that I'm unaware of.

Have you checked measurements on your system and can confirm that you see +6dB of gain when both left and right are playing?

And just to be clear, you are saying that the frequency response should be basically the same with both playing, just 6dB higher than with only one playing, correct?

EDIT: Just saw Nicks post - maybe the phase issue is reflection related - if really only 3dB higher.

[Jdunk54nl]

Ya, what is causing it and can you fix it are two important questions that are semi-hard to answer....

[ckirocz28]

I'll have to double check the measurements with REW. I don't remember seeing a 6dB increase when playing both speakers - could be wrong though - didn't pay close enough attention to exactly how much higher the measurements were when playing both speakers - just checked to see that response stayed the same across the frequency range - and was higher. I can't imagine that the speakers (all three sets - dash, door and rear-deck) could be out of phase the same amount - I mean the physical polarity is definitely the same on them and time alignment is set properly, so just can't see how they would all be out of phase by the same amount like that.

I'll take some new measurements today and confirm if they are ~3dB or ~6dB higher when playing both left and right and go from there. Who knows, maybe there is some issue with my system that I'm unaware of.

Have you checked measurements on your system and can confirm that you see +6dB of gain when both left and right are playing?

And just to be clear, you are saying that the frequency response should be basically the same with both playing, just 6dB higher than with only one playing, correct?

EDIT: Just saw Nicks post - maybe the phase issue is reflection related - if really only 3dB higher.

Yeah, you'll be hard-pressed to get that 6 db increase from speakers a car width apart, they need to be within a quarter wavelength of each other to get the full coupling effect. Subs and midbass are fairly easy to couple like that, mids and tweets are not. And the reflections absolutely figure into that problem, and all the other nastiness our cars provide.