3 Attachment(s)
REW and DSP help - Acoustical vs Electrical crossover.
Acoustical vs Electric crossovers.
Do you get electrical vs acoustical crossover differences to the tune of several hundred hz?
I'm using a JL Twk88 DSP with their TUN software. I have an Imm-6 measurement mic and REW. I EQ'd my system about a month ago, it was my first time to REW, measurement mics, and DSPs. It went really well. I ignored the acoustical vs electrical crossover stuff because I'd already used the EQ to hammer it in line and it was too late to go back. I used boost (realized after talking to an installer and fellow owner of a Honda fit who also was using the same mid-bass that we were fighting the same nulls) in a couple areas. I re-adjusted my gains to compensate for the added power.
I'm starting from scratch as I have a few new components. New subwoofer(s), and some horns. This post is only focused on the mid-bass and the subwoofer. The rough goal is no boost, only cuts. I'm trying to start by ignoring the nulls. I might experiment with them later. What I'd like to focus on for the comments to this post is acoustical vs electrical crossovers and what your experience with how far off they can get.
My Midbass previously was ~20-30hz off of my LPF electrical crossover. Same thing is happening now. So far I only applied the EQ suggestions from REW using my house curve. I'm only showing 2 averages on the photos. With EQ and without EQ, no change in crossover points. The subwoofer got no change in EQ because it was pretty flat, and I didn't really know how to address the crossover being THAT far off.
My midbass HPF should be dipping down at ~640, but isn't starting until past 1khz. My subwoofer is ridiculous. Its playing to 140hz when it has an electrical crossover of 80hz. Last time I EQ'd a different subwoofer it played to ~100hz and I just EQ'd it into shape.
But before I get too deep into tuning I wanted to ask this board some questions and figure out what I should do and if this is normal.
Subwoofer is set to HPF 20hz - LPF 80hz.
Mid-bass is set to HPF 80hz - LPF 800hz
Horns then kick in above 800hz - I'm leaving those out of this discussion for now.
Attachment 13443Attachment 13444Attachment 13445
Re: REW and DSP help - Acoustical vs Electrical crossover.
What you're seeing is not uncommon at all.
For example, below is a picture of me using a 510hz high-pass filter to hit a 300hz crossover target.
And that's just the driver's side .....
https://photos.smugmug.com/photos/i-.../i-Qb3NmSQ.gif
Re: REW and DSP help - Acoustical vs Electrical crossover.
Just a quick one, is there any reason you don't want to Upgrade to a newer version of rew? That looks very old? I’ve been using the beta versions for over a year now and they are very very stable
as for your responses, it’s likely a big hump in response and a wide dip lower down, a crossover will look accurate on paper with a perfectly flat response before hand, that’s why you adjust the crossover so the actual response matches the target curve, it’s the dropping of level that gives the phase shift so in theory you could eq in a crossover if you had big enough cutting capability’s
if the actual crossover point isn’t low enough lower the electrical crossover some more
Re: REW and DSP help - Acoustical vs Electrical crossover.
Quote:
Originally Posted by
dumdum
Just a quick one, is there any reason you don't want to Upgrade to a newer version of rew? That looks very old? I’ve been using the beta versions for over a year now and they are very very stablee
screenshot looks old because it was done years ago, so it's old : )
Re: REW and DSP help - Acoustical vs Electrical crossover.
Oh he was talking to you. Lol. I shamefully updated to the latest version of REW.
I got my subwoofer tamed very easily. It fell into line with a change in electrical crossover and 2 bands of EQ.
Like I said previously, I have to take a drive to go EQ and play obnoxious sine waves and pink noise. I was playing in my driveway at VERY low volumes and thought it was interesting that without changing anything, the acoustic is almost the exact same as the electrical crossovers. It must just be with volume that it gets wily. I don't know enough about how active crossovers work on an electrical level, but if its consistent that they are more true at low volumes then one would think that the companies producing DSPs could maybe find a correlation to how volume affects the crossover drift ... It would be interesting to see if this is consistent. I'm curious Jazzi if your midrange is "true" to the acoustic and electrical crossover at very low volumes and drifts as it gets louder.
I drove all the way up the hill to my usual spot, got my mic hooked up and everything set up. I was about to play my first sine sweep when my buddy pulls up out of nowhere on his bicycle .... 45 minutes later and no EQ work was done at all... better luck tomorrow.
Re: REW and DSP help - Acoustical vs Electrical crossover.
Quote:
Originally Posted by
DirtyBumOAK510
Oh he was talking to you. Lol. I shamefully updated to the latest version of REW.
Was that aimed at you instead? What's going on!? lol
Quote:
Originally Posted by
DirtyBumOAK510
Like I said previously, I have to take a drive to go EQ and play obnoxious sine waves and pink noise. I was playing in my driveway at VERY low volumes and thought it was interesting that without changing anything, the acoustic is almost the exact same as the electrical crossovers. It must just be with volume that it gets wily. I don't know enough about how active crossovers work on an electrical level, but if its consistent that they are more true at low volumes then one would think that the companies producing DSPs could maybe find a correlation to how volume affects the crossover drift ... It would be interesting to see if this is consistent. I'm curious Jazzi if your midrange is "true" to the acoustic and electrical crossover at very low volumes and drifts as it gets louder.
The behavior of an audio system should be linear, meaning it behaves the same at low volume and high volume. This is certainly true for DSPs and amplifiers and other electronics unless you're pushing them *way* too hard. This is also true for speakers at medium and low and "very low" volumes. So I doubt your system would behave different between medium, low, and very low volumes.
It is more likely the very low volume measurements were corrupted by ambient noise or some other non-speaker-thing that is usually quiet enough to not matter when you're measuring a medium volume levels.
Unless you're using part of your factory radio system? Some factory radios have a crossover frequency shifting as volume increases to protect speakers from the lowest frequencies as you start to hammer on it. This is a really neat feature when you have lots of design constraints and cannot use the speaker you want, so you use the speaker you have in the best way you can at each volume level.
I think what I'm saying is if you're really seeing this behavior, it's not on accident because normal DSPs don't work that way. It takes a lot of effort to setup this kind of feature on purpose. You can very easily check for this behavior by taking multiple measurements as you slowly increase the volume on your radio a couple clicks at a time then look at all the measurements on the same screen at the same time.
Re: REW and DSP help - Acoustical vs Electrical crossover.
Quote:
Originally Posted by
Justin Zazzi
Was that aimed at you instead? What's going on!? lol
The behavior of an audio system should be linear, meaning it behaves the same at low volume and high volume. This is certainly true for DSPs and amplifiers and other electronics unless you're pushing them *way* too hard. This is also true for speakers at medium and low and "very low" volumes. So I doubt your system would behave different between medium, low, and very low volumes.
It is more likely the very low volume measurements were corrupted by ambient noise or some other non-speaker-thing that is usually quiet enough to not matter when you're measuring a medium volume levels.
Unless you're using part of your factory radio system? Some factory radios have a crossover frequency shifting as volume increases to protect speakers from the lowest frequencies as you start to hammer on it. This is a really neat feature when you have lots of design constraints and cannot use the speaker you want, so you use the speaker you have in the best way you can at each volume level.
I think what I'm saying is if you're really seeing this behavior, it's not on accident because normal DSPs don't work that way. It takes a lot of effort to setup this kind of feature on purpose. You can very easily check for this behavior by taking multiple measurements as you slowly increase the volume on your radio a couple clicks at a time then look at all the measurements on the same screen at the same time.
I was going to say just that... floor noise ���� And the rew upgrade was for the OP :D
Re: REW and DSP help - Acoustical vs Electrical crossover.
I've learned to EQ before applying xover filters. Makes it easier to identify areas outside of the passband that needs correction. Using LR4 xover filters; I'll EQ up to an 1.5 octaves outside of the passband and maybe more if I have filters left. I found this usually results in acoustical xovers matching electrical or very close at least.
Re: REW and DSP help - Acoustical vs Electrical crossover.
Quote:
Originally Posted by
Justin Zazzi
Unless you're using part of your factory radio system?
Not a factory radio. I'm gonna chalk it up to background noise and noise floor issues because I was doing this with VERY low volume. I'll take your word for it.
Re: REW and DSP help - Acoustical vs Electrical crossover.
So I just realized I've been living in bonehead land. Somewhere I could have sworn I read that you should EQ with Sine sweeps and not pink noise. So thats how I eq'd my last build. Now I'm halfway through EQing this one and realizing the error of my ways after chatting with someone. So I'm supposed to have been using periodic pink noise. After searching the forums, this has become clear. Doh!
So my questions of the day, which I ask after scouring threads all afternoon and still not feeling confident.
1. When do we use sine sweeps? What purpose do they serve?
2. I'm setting my EQ by using 8 measurements, (Left speaker = 3 left ear, 5 right, Right speaker = 2 left ear, 6 right ear), then taking an average. Then plotting that against my custom house curve (Andy's bass, Jazzis dip (verified by Eric Stevens)) So if I'm using periodic pink noise... How long do I need to take each measurement (per ear)? It seems link pink noise repeats itself every 3.5 seconds, so is that as long as I need to take a measurement?
3. When downloading Periodic pink noise ... I know that I match the FFT on my RTA graph. But when downloading the periodic pink noise, I'm downloading it at 0dbfs? Left only? (for left speakers) and vice versa R only for right speakers? Because L+R pink noise is no longer mono ...
Thanks in advance.
