Simulating a car environment

[har-bal]

Paavo and I were speaking the other day and I was tellling him that a lot folks love to test their CD's in their cars and wouldn't it just be great to able to siimulate a car environment in your studio. It would sure save a lot of CD's : )

Well here is the process he came up with.

Take a laptop with a USB sound card plus microphone and a CD with a pink noise track. Then play the CD whilst recording the sound pressure using the microphone in your normal listening position. Then take
the orginal source pink noise track and the reproduced pink noise track and analyze them with harbal. Then use the microphone recorded track as reference and the pink noise as source. Now adjust the source
spectrum to match the reference and save the filter. You've now just constructed a HarBal filter that mimmicks the frequency response in your car! Now you can use HarBal to see how it might sound in your car.

Use a good electret with a flat frequency response and you'd probably want to use one with a cardiod pattern rather than a back electret because using a back electret may show artificially less bass than there actually is in your car.

Earle

[mflorio]

Earle,

You forgot to actually say to do this *in the car* !

Also - very important in my opinion - record with the engine running or while actually driving the car if you can (get someone else to help !). You want to make sure that you properly account for the noise floor when driving at moderate speeds.

Mike

[mflorio]

Logically, taking this one step further :

You should actually record the pink noise with mic as it sounds in your studio, and analyze *that* audio with Har-Bal, instead of using the pink noise audio right off the cd. Now your two recordings will be :

- How the pink noise sounds in your room
- How the pink noise sounds in your car

Mike

[mflorio]

Sorry for all the separate posts ... !

This just got me thinking that it's possible to actually "tune your room" using this method...

- Analyze the direct pink noise off the cd

- Analyze the recorded pink noise as it sounds in the room (using a mic with as flat a response as possible)

- In HB, using the direct as a reference, build a filter for the room eq until it matches the direct eq trace exactly.

You have just created a filter that compensates for your listening environment. You can then apply this filter to any audio you open in HarBal, before making further changes.

Mike (again)

[Har/Bal]

Mike

Thanks for the correction and yes you can actually tune your room using this method.

Earle

[Har/Bal]

Mike

Creating a filter to use as a starting point based on your room accoustics and then shaping the spectrum is actually a brilliant idea!

You may have just started something.

What brand mic would you suggest that is affordable for most folks based on the specs here?

"electret mic with a flat frequency response and a cardiod pattern"

Earle

[dbmasters]

I am currently beta testing a software plugin for a company that does precisely that. They have models of different environments, systems and such and it is actually very cool. Not totally stable yet, but coming along nicely. So stay tuned. It will be mentioned at HRC when launched, I won't here becasue, well, this is the site for a different business...

[mflorio]

Mike
What brand mic would you suggest that is affordable for most folks based on the specs here?

"electret mic with a flat frequency response and a cardiod pattern"
Earle

Hi Earle,

That's a tough one, and I'm probably not the right guy to answer. All the mics I use are really for vocals, and hence have a certain 'character'. I would think a large-diaphram condenser, but definitely omni (and even stereo) instead of cardiod. Cardiod will not sufficiently pick up the room reflections from all directions, like your ears would.

Mike

[Har/Bal]

Well Mike I tried it using my AKG C414b mike. and it worked like a charm.

I placed it in the center of the room and shot pink noise out from my other system and recorded about 30 secconds.

Loaded a cd with pink noise into Har-Bal and allowed it to create a .anl reference file. I then loaded the newly recorded pink noise file and matched it to the original and created a filter.

What a difference it is making.

Found a few holes and peaks that I was always trying to adjust for.

Definately happy with the results

Earle

[mflorio]

That's great news. I'll have to try it with one of my vocal mics.

Do you mind telling me what reference cd you're using. I guess I can just use a pink noise generator on a synth too...

Mike

[Har/Bal]

I used the pink noise generator included with a product called Spectrum Analyzer Pro Live 3.9

When I recorded the pink noise I positioned the mic in front of my console.

You can go to my other site and download the pink noise mp3 I used which was included with the program

URL is www.hdqtrz.com/Pink

That idea of your really worked well and I am sure a number of folks will be trying it out.

Earle

[HarBal]

Mike
What brand mic would you suggest that is affordable for most folks based on the specs here?

"electret mic with a flat frequency response and a cardiod pattern"
Earle

Hi Earle,

That's a tough one, and I'm probably not the right guy to answer. All the mics I use are really for vocals, and hence have a certain 'character'. I would think a large-diaphram condenser, but definitely omni (and even stereo) instead of cardiod. Cardiod will not sufficiently pick up the room reflections from all directions, like your ears would.

Mike

That's fine but be careful with open back electrets since it may give you misleading LF measurements. Thats because at the LF end open back electrets respond to pressure gradient and if you've got a standing wave in your room coming in at right angles to the mike the mike won't pick it up. That was my main reasoning for the suggestion of a cardiod pattern.

Ideally you should be using a instrumentation mic if you have one or can get one. Good noise performance is not that critical for this sort of thing so you can go for a cheap one. Behringer actually makes an instrumentation electret condeser that sells for around $100 US and it comes with a frequency response calibration curve for it as far as I remember.

In a future version I'll add a calibration filter to Harbal so you can load your compensating frequency response automatically applied to what ever you are working on. You wont see the effect of the filter on the spectrum display but you'll definitely hear it on the output.

Regards,


Paavo.

[mflorio]

Thanks for the tips and mp3, guys.

Here are the mics I currently have:
Rode NT2, StudioProjects C1, Audix OM5, AKG C535eb, Shure SM57

Any suggestions as to what to try first ?

Mike

[HarBal]

Thanks for the tips and mp3, guys.

Here are the mics I currently have:
Rode NT2, StudioProjects C1, Audix OM5, AKG C535eb, Shure SM57

Any suggestions as to what to try first ?

Mike

The problem with most studio mikes is they are not designed to have a flat frequency response so you'll need to compesate for this when you make an adjustment.

If you are really serious about measuring your listening environment performance then I'd recommend buying a measurement microphone. As I mentioned earlier Behringer makes an inexpensive measurment mic (ECM8000) which has an onmi-directional pattern and also has a low LF corner frequency. Here is a link to the product description if you are interested.

http://www.behringer.com/ECM8000/index.cfm?lang=ENG

Regards,


Paavo.

[mflorio]

Yeah, I figured an omni mic would be the best choice. Thanks for the link. I just ordered it for $50 US.

Mike