[truckguy]

I downloaded the REW software a few weeks ago and have been working on tuning my system with varied results. One thing I noticed is that when I have everything muted I have spikes on my graph. Can anybody tell me how to get rid of those? I've read other threads that talk about a feedback issue but I don't know how to fix it.

I'm using a Dayton UMM-6 microphone through a USB. I do have the calibration file downloaded and input into the mic section.

Another question in general with tuning. Do you tune with your car on(14v) or off(12v). I was tuning with the car off(12v) and had things sounding pretty good. I turned the car on to go drive somewhere and it sounded terrible. Now I'm thinking I have to tune my system with my car on to get correct measurements. Does that sound right?

 

[Justin Zazzi]

If you run a sweep while the speakers are muted, and you put some heavy fabric/blankets over the microphone ... does that eliminate the spikes? Can you post one of your measurements with the speakers not muted? I'm thinking the noise you are seeing is far below the measurements you are making.

Most everyone I know tunes with the car off and with a battery charger attached.

 

[Beckerson1]

If you run a sweep while the speakers are muted, and you put some heavy fabric/blankets over the microphone ... does that eliminate the spikes? Can you post one of your measurements with the speakers not muted? I'm thinking the noise you are seeing is far below the measurements you are making.

Most everyone I know tunes with the car off and with a battery charger attached.

Yep a battery charger is a must. Op I also agree with Jazzi. Your microphone is a sensitive piece of equipment and I also believe what your seeing isn't a cause to be concerned about. Iirc I get spikes with mine. It's about the resolution. Plus if you were to change the resolution of that graph to 1/3oct you should eliminate all of that noise, well not noise spikes. It should smooth out drastically

 

[Babs]

REW newb here as well, also with a UMM-6. I had something looking like that also, then smoothed to 1/3 octave it looks like this with a few measurements shown within a few inches of each other. Keep in mind, just to illustrate.. I've done no EQ yet. Just some initial T/A and crossover points.

 

[truckguy]

Thanks for the responses. Babs your sweeps look great compared to mine. I'm probably putting more stock in the spikes where I should be looking more at my newb ability to make adjustments off these charts. I've been using 1/12 smoothing and making some crazy changes on the DSP. I have the new next few days off and plan to play around with my tuning some more.

Here are my tweeters and mids with 1/12 smoothing before any changes. The tweeters are on axis and the mids are low in the doors in stock locations.

For tuning I did use a battery charger when the car was off but swear it didn't sound anything like my tuning when driving around the next day. I could shut the car off and it would sound "good" again while running off the battery. I'm using ARC SE amps. The 2300 on my tweeters and a bridged 4200 on the mids if that makes any difference.

 

[Beckerson1]

Thanks for the responses. Babs your sweeps look great compared to mine. I'm probably putting more stock in the spikes where I should be looking more at my newb ability to make adjustments off these charts. I've been using 1/12 smoothing and making some crazy changes on the DSP. I have the new next few days off and plan to play around with my tuning some more.

Here are my tweeters and mids with 1/12 smoothing before any changes. The tweeters are on axis and the mids are low in the doors in stock locations.

For tuning I did use a battery charger when the car was off but swear it didn't sound anything like my tuning when driving around the next day. I could shut the car off and it would sound "good" again while running off the battery. I'm using ARC SE amps. The 2300 on my tweeters and a bridged 4200 on the mids if that makes any difference.

No need to worry about 1/12 oct smoothing. Most, if not all, dsps are 1/3 so when tuning use 1/3 smoothing at most use 1/6 for some finer adjustments.

Anything more then that makes it very hard to dicern adjustments and will confuse you.

 

[Justin Zazzi]

Truckguy,

How loud are your speakers when making measurements? They should be pretty loud. From what it looks like, your "muted" measurements have noise from about zero dB to twenty dB, but that is pretty similar to your tweeter measurement especially. See all that information below 200hz on your tweeter plot? That's noise and shouldn't be anywhere near as loud as your tweeters.

Try increasing the volume by a substantial amount and noting the volume level on your head unit. When I make sweeps, my volume is about 75/80 on my head unit, which is close to clipping but not quite. This keeps the noise floor so low to be insignificant.

 

[Beckerson1]

Thanks for the responses. Babs your sweeps look great compared to mine. I'm probably putting more stock in the spikes where I should be looking more at my newb ability to make adjustments off these charts. I've been using 1/12 smoothing and making some crazy changes on the DSP. I have the new next few days off and plan to play around with my tuning some more.

Here are my tweeters and mids with 1/12 smoothing before any changes. The tweeters are on axis and the mids are low in the doors in stock locations.

For tuning I did use a battery charger when the car was off but swear it didn't sound anything like my tuning when driving around the next day. I could shut the car off and it would sound "good" again while running off the battery. I'm using ARC SE amps. The 2300 on my tweeters and a bridged 4200 on the mids if that makes any difference.

At what volume are you doing these measurements at. I use the normal listening volume I listen to while I drive.

What could be happening is when yor running with the car off you amp, for the mids, may not be putting out full power and could have a different response then with the car running.

Reason guys tune with the car off is noise. You want it as quiet as possible. Hence why some tune late at night.

 

[Beckerson1]

Truckguy,

How loud are your speakers when making measurements? They should be pretty loud. From what it looks like, your "muted" measurements have noise from about zero dB to twenty dB, but that is pretty similar to your tweeter measurement especially. See all that information below 200hz on your tweeter plot? That's noise and shouldn't be anywhere near as loud as your tweeters.

Try increasing the volume by a substantial amount and noting the volume level on your head unit. When I make sweeps, my volume is about 75/80 on my head unit, which is close to clipping but not quite. This keeps the noise floor so low to be insignificant.

Also to add make sure you presetup REW and the mic correctly as to not distort the measuring device. This can be done by reducing your computer's volume and mic volume. This is important as it will give you the cleanest representation of your response.

 

[truckguy]

I know I didn't make any changes for computer and mic volume. I'll check into that. My HU(Pioneer 80prs) goes up to 62 and I was making measurements at 40(normal volume). I don't start to hear any clipping until about 50 and that's my tweeters which are what I'm trying to blend better.

As far as car on and off, either my tweeters are playing louder or my mids are softer when my car is off compared to running which is making tuning difficult. I'm tuning on the Helix DSP so I'm not sure if that is 1/6, 1/12, or etc for smoothing. I'll be working on this tomorrow and will report back. Hopefully with better results. I've been working off of other threads for "Optimal RTA", REW, and Time Alignment that have been a ton of help. Now I just need to put it all together. Thanks for the input.

 

[Beckerson1]

I know I didn't make any changes for computer and mic volume. I'll check into that. My HU(Pioneer 80prs) goes up to 62 and I was making measurements at 40(normal volume). I don't start to hear any clipping until about 50 and that's my tweeters which are what I'm trying to blend better.

As far as car on and off, either my tweeters are playing louder or my mids are softer when my car is off compared to running which is making tuning difficult. I'm tuning on the Helix DSP so I'm not sure if that is 1/6, 1/12, or etc for smoothing. I'll be working on this tomorrow and will report back. Hopefully with better results. I've been working off of other threads for "Optimal RTA", REW, and Time Alignment that have been a ton of help. Now I just need to put it all together. Thanks for the input.

31 bands = 1/3 oct

Do everything at 50 on the HU. Does the Helix DSP have individual channel levels? If so you can lower the tweeter volume that way.

 

[therapture]

OP, those little spikes are normal. Nothing to worry about, some artifact of the system or what not, but they are insignificant. Make sure, as others have noted, to record at enough volume level to eliminate that noise floor. I like to see at least 60db minimum of actual output through your system, that has worked well for me.

You are headed in the right direction, now you have to take those three plots and make a "curve" out of them when they are all combined. You are in for an eye opening, fascinating, and fun experience.

 

[truckguy]

I started from scratch today and made it thru 3 rounds of sweeps. I ended up with the HU at 48. There is a difference if I have my car on and off so having it louder helped cover the sound of the car running. Right now I'm using 24db slopes but might end up trying 18db. The helix does have separate channel gains and etc. Here is where I ended up. I still have quite a bit of work left. I have left(blue) and right(purple) sweeps below and then a full sweep with a house curve I created. There is a huge bump in the lower mid range I can't remove. I also have some work between 3k and 5k. Let me know what you think and if you have suggestions.

My only questions now are how big of cuts/gains can you make in areas? Right now I have a -6db cut on the left mid at 315hz and wonder if it's okay to do more. I have a few other spots with +4db gains but afraid to do more. Also if I want less rumble and more punch out of my sub what cuts/boosts do I need for that?

Oh I also watched a youtube video where they had an external soundcard so they could create a loopback calibration file to clear up noise. Is it worth doing that? I think I'm okay for now at my level.

 

[Justin Zazzi]

Do you really have a difference of almost 40dB between your bass and treble? I know this is all about personal preference, but some people might consider that a bit much. I only mention it because you're asking for help.

You can make as large a cut as you need to, up to 20dB or more if the system needs it. Boosts though, be careful with. +3dB of boost is double the power, so you will run out of headroom really fast. In addition some frequencies will not respond to boosts and if you notice this, don't try to boost those particular frequencies.

To get more punch and less rumble, try boosting the midbass frequencies (100-200hz) and cutting the lowest octaves (30-40hz). For more detail, check out this chart and look near the bottom.

Interactive Frequency Chart - Independent Recording Network

If you're using a USB microphone, then you cannot use the loopback method to calibrate for frequency response anomalies of a sound card, because you're not using one. Good try though.

Oh, and those levels look much better than the charts you posted before

 

[therapture]

I am very limited here due to experience of less than 2 years with a dsp...but...that bump at 315-ish could actually be a dip at 200...and if you ran an excess group delay plot for the raw data (not averages) you could find that out, I believe. To me, the curve looks solid.

I think sticking with 24db slopes for now would suffice, there are some advantages to this particular slope that seem good enough to stay on this slope for most purposes.

Try to cut more than you boost on the EQ. Don't be afraid to try larger cuts, whatever it takes to fix the problem. I have a problem frequency that I actually put 19+ db of cut into to correct the sound! And the "Q", use it to focus or spread out the adjustment width from the center frequency.

Remember, 3db in cut/boost is twice the power, so a 6db boost is 4x the power!

I started from scratch today and made it thru 3 rounds of sweeps. I ended up with the HU at 48. There is a difference if I have my car on and off so having it louder helped cover the sound of the car running. Right now I'm using 24db slopes but might end up trying 18db. The helix does have separate channel gains and etc. Here is where I ended up. I still have quite a bit of work left. I have left(blue) and right(purple) sweeps below and then a full sweep with a house curve I created. There is a huge bump in the lower mid range I can't remove. I also have some work between 3k and 5k. Let me know what you think and if you have suggestions.

My only questions now are how big of cuts/gains can you make in areas? Right now I have a -6db cut on the left mid at 315hz and wonder if it's okay to do more. I have a few other spots with +4db gains but afraid to do more. Also if I want less rumble and more punch out of my sub what cuts/boosts do I need for that?

Oh I also watched a youtube video where they had an external soundcard so they could create a loopback calibration file to clear up noise. Is it worth doing that? I think I'm okay for now at my level.

 

[Babs]

As a humble REW or RTA measuring newb myself, I think I should leave this here. This is about the best REW tuning thread I've found so far. About every car audio REW question I've seen has been covered a bit in here:

http://diymobileaudio.com/forum/how...first-timers-guide-measuring-your-system.html

Just sharing as I spent all night last night sucked into Hanatsu's great explanations.

 

[truckguy]

I got a good laugh out of the 40db for my sub. I kept boosting that area thinking it would help the kick drums in rock music. This tells you how much I have to learn. I also have the remote for the Helix with volume control for sub. When my kid is in the truck I turn it off for the most part. I have the sub and mids crossed at 70. I'll get rid of the bump at 30-40, move the crossover up to 80, and see what else I can do. Turn the volume knob down.

I definitely have some places to cut but I'm limited to 10db I think. All this helps me out a bunch. The link itself helps with understanding where each instrument plays. I know what I want my system to sound like but don't know how to get it there! Lots of experimenting I guess.

The How-To tab in diyma is where I found a lot of information. The threads sticky'd at the top are great.

It's to cold to get out there tonight. I'll see what I can do tomorrow. Thanks everybody for the help.

therapture, can you explain how to run an excess group delay? I usually delete the "raw data" after I create the averages. I'll be creating some more tomorrow though.

 

[Beckerson1]

I got a good laugh out of the 40db for my sub. I kept boosting that area thinking it would help the kick drums in rock music. This tells you how much I have to learn. I also have the remote for the Helix with volume control for sub. When my kid is in the truck I turn it off for the most part. I have the sub and mids crossed at 70. I'll get rid of the bump at 30-40, move the crossover up to 80, and see what else I can do. Turn the volume knob down.

I definitely have some places to cut but I'm limited to 10db I think. All this helps me out a bunch. The link itself helps with understanding where each instrument plays. I know what I want my system to sound like but don't know how to get it there! Lots of experimenting I guess.

The How-To tab in diyma is where I found a lot of information. The threads sticky'd at the top are great.

It's to cold to get out there tonight. I'll see what I can do tomorrow. Thanks everybody for the help.

therapture, can you explain how to run an excess group delay? I usually delete the "raw data" after I create the averages. I'll be creating some more tomorrow though.

I'd do L to R balance before going hard into EQ work.

What I mean by this is you want your FR response on each side to be within at least 3db of each other (then you can work on getting them closer). This will clean up any wandering you may have. Then you can worry about EQ work.

This may differ between guys but for me:

TA, L & R balance, EQ

 

[therapture]

therapture, can you explain how to run an excess group delay? I usually delete the "raw data" after I create the averages. I'll be creating some more tomorrow though.

In the tabs on the left of the REW window, where each measurement is...have THAT particular tab selected... see the tabs above the plot labeled "GD"?...select that. Now, click the "controls" button on the top right, you can see that there is a button you can click called "Generate Minimum Phase". Once clicked it generates the delay line called "Excess Group Delay" in the names below the plot.

What that line shows you is say, at 40hz on the horizontal axis you have a point that intersects the 25ms line on the vertical axis...and another at 250hz that intersects at 3ms...means that at 40hz the signal being played is 22ms BEHIND the sound at 250hz. Ideally, you would have a perfectly flat line at all frequencies at "0" ms, but don't worry, that really doesn't happen. You can kind of tell from the group delay charts for the system if you have a big TA issue between sub/mids/tweets as there could be a huge V at the crossover/handover frequency. I had a huge suckout at 70hz and all it took was adding 2.25ms of delay to the sub and that cured most of it.

Your sub will usually have a sloping line from say 10ms to 30ms or more as it goes lower in frequency. Mids and tweets ideally would be at 0 all the time, but again, in the real world...not going to happen. Use the delay charts to spot problem areas...the big tall "V"...

What you are really looking for is a big "V" in the delay line, pointing upwards. Where ever you have one of these big tall V's at a specific frequency, typically corresponds with a DIP in your frequency response chart. At that frequency, you really cannot EQ it out, you could boost that frequency all day long and make little difference in the actual sound measured, but you can mess up the sound trying to over EQ that frequency.

Hope I explained that correctly...

 

[Babs]

^ Goes back to Erin's thread on sub phasing. Sub phasing and T/A need to be fairly well dialed in, or it'll throw your FR at those crossover transitions I'd guess by significant amount.

So like Beckerson1 said above if I may amend: TA/Phasing, THEN balance, THEN EQ. So messing with EQ at all before the foundation is built, is putting the cart in front of the horse.
... As if I actually have a clue as to what I'm talking about. LOL!

I'm actually taking Hanatsu's big thread I linked above and truncating it down to main steps 1-2-3, etc in my iCloud notes.