INTERACT FORUM

Please login or register.

Login with username, password and session length
Advanced search  
Pages: [1]   Go Down

Author Topic: Noob questions about room correction with JRiver  (Read 4744 times)

PrinterPrinter

  • World Citizen
  • ***
  • Posts: 204
Noob questions about room correction with JRiver
« on: September 08, 2015, 02:25:14 pm »

Hello,
I finally got around to start messing with room correction - one of the main features of JRiver for me.

I looked at the guide and started setting it up (got a Umik). I have a few question, I'd be grateful for your feedback - thank you!

1. My main stereo computer is actually an RPI running MC. I'm using another windows PC for all the measurements because its easier, my question is; once I finish the process and have the convolution filters working properly on the PC, can I just copy over that file toe the RPI and have the same results by running it via JRiver on the RPI?

2. my system has two floor standers (B&W CM10s2) as well as a sub that's connected directly to the dad. I don't have a dedicated sub channel so I understand I have to EQ the whole system together with the sub? Shall I start with measuring the speakers on their own and then use the measurements to calibrate the sub (via REW?) before proceeding to EQ everything together?

3. According to the guide I should use Holm to close mic my speakers - they are big 5 driver 3 way speakers (mot massive speakers but certainly not small). Shall I close mic each driver? there are 3 woofers...?

Thank you, any advice would be great!
Logged

mwillems

  • MC Beta Team
  • Citizen of the Universe
  • *****
  • Posts: 5234
  • "Linux Merit Badge" Recipient
Re: Noob questions about room correction with JRiver
« Reply #1 on: September 08, 2015, 06:25:42 pm »


1. My main stereo computer is actually an RPI running MC. I'm using another windows PC for all the measurements because its easier, my question is; once I finish the process and have the convolution filters working properly on the PC, can I just copy over that file toe the RPI and have the same results by running it via JRiver on the RPI?

I haven't done much testing with convolution on the Pi, but I would not be surprised if it didn't have the CPU power to run a long convolution filter.  Assuming that convolution works on the Pi, it should be as simple as moving the file over, but that's a big assumption.  

For example I have a very short and simple convolution filter that runs at 80x realtime on an i7-2660k; I have longer convolution filters that do more and only run around 30x realtime; an RPi 2 has roughly about 1/60 of the computing power of an i7-2660k according to the best benchmarks I've seen.  So even if convolution "just works" in JRiver ARM you'll have very limited scope for your convolution filters.  Convolution is very computationally expensive, so I wouldn't count on doing all your eq in convolution.

JRiver's parametric EQ is significantly faster and less computationally expensive than convolution (even doing the exact same filtering), so in keeping with the guide, I'd advise you to do what you can in PEQ, which I can confirm works just fine on the Pi, even with a moderate number of filters (eventually you will bump against the Pi's limits though, even there).

Quote
2. my system has two floor standers (B&W CM10s2) as well as a sub that's connected directly to the dad. I don't have a dedicated sub channel so I understand I have to EQ the whole system together with the sub? Shall I start with measuring the speakers on their own and then use the measurements to calibrate the sub (via REW?) before proceeding to EQ everything together?

Since you can't actually correct the sub separately, I'd suggest measuring it all together, you'll quickly see if the sub's volume matches the speakers when you take the 1 meter measurements.  That said, depending on where you cross to the sub it might make sense to separately mic the sub as an additional stage (if you cross above 80 or 100Hz or so) or it might not matter (below 40Hz I certainly wouldn't bother unless it were very far from the speakers or I could correct it separately).

Quote
3. According to the guide I should use Holm to close mic my speakers - they are big 5 driver 3 way speakers (mot massive speakers but certainly not small). Shall I close mic each driver? there are 3 woofers...?

Thank you, any advice would be great!

I'd suggest measuring each stage separately (low, mid, and high separately).  If your mid and high stage only have one driver each, that should be easy, just follow the guide.

For your woofers, the best distance will depend on how the woofers are arranged and whether or not they all play the same frequencies.  I have a pair of washing machine sized speakers with four woofers arranged in a square and had no issues just positioning the mic three inches from the acoustic center of the four woofers.  Folks with MTMs or 2.5 or 3.5 way speakers will need to adapt the formula a little bit.

But it looks like your speakers just have the three woofers vertically stacked, so my advice to you would be to take your low frequency stage measurements at 3 inches from the center woofer (the acoustic center).

The bottom line is that your 3 inch measurement should look somewhat similar to your 1 foot measurement but much smoother.  If your 3 inch measurement looks very jagged or very different from your 1 inch measurement, try measuring a little farther out (an inch at time) until you get something sensible.  But you should be able to measure at 3 inches with that driver arrangement.

Logged

PrinterPrinter

  • World Citizen
  • ***
  • Posts: 204
Re: Noob questions about room correction with JRiver
« Reply #2 on: September 08, 2015, 06:53:03 pm »

Thanks mate!

I'll give it a go tomorrow and see where I get too.

Regarding the point about the RPI lacking processing power, my main 'library computer is actually an i7 with 12GB and runs MC (although in a different room), can I use its ability to apply DSP over the DLNA streaming and run the processing for the Pi?

Regarding the Parametric EQ, is there an elegant way of extracting the correct filters for the paramedic EQ, or translating the convolution filters to PEQ automatically? Perhaps with the programs you mentioned?

Thank you!
Logged

mwillems

  • MC Beta Team
  • Citizen of the Universe
  • *****
  • Posts: 5234
  • "Linux Merit Badge" Recipient
Re: Noob questions about room correction with JRiver
« Reply #3 on: September 08, 2015, 07:34:11 pm »

Thanks mate!

I'll give it a go tomorrow and see where I get too.

Regarding the point about the RPI lacking processing power, my main 'library computer is actually an i7 with 12GB and runs MC (although in a different room), can I use its ability to apply DSP over the DLNA streaming and run the processing for the Pi?

Some DSP is supported over DLNA, but I don't know if convolution is one of the supported modules (I've never tried).  Search the forums for DSP over DLNA and you'll see some instructions to help you test.

Quote
Regarding the Parametric EQ, is there an elegant way of extracting the correct filters for the paramedic EQ, or translating the convolution filters to PEQ automatically? Perhaps with the programs you mentioned?

If you read the room correction guide it explains exactly how to transfer filters from REW to PEQ with screen shots ;)

To be fair, the method is a manual one (not too elegant), but you should only have to do it once, and it might take ten or twenty minutes (if you have a lot of filters).  

There are some types of correction that can only be done with convolution, so for those it's convolution or nothing (but the guide also explains what those are, and they don't include the majority of the correction).
Logged

PrinterPrinter

  • World Citizen
  • ***
  • Posts: 204
Re: Noob questions about room correction with JRiver
« Reply #4 on: September 09, 2015, 05:05:16 am »

Thank you, I'll go read that guide properly ;-)
Logged

PrinterPrinter

  • World Citizen
  • ***
  • Posts: 204
Re: Noob questions about room correction with JRiver
« Reply #5 on: September 11, 2015, 04:52:17 am »

Hello,
I've started following your guide and have a small question,

In the first part of Holm measurements - to establish a baseline should I measure both speakers and sub together or have a separate measurement for each? And then somehow combine them?

Thanks!
Logged
Pages: [1]   Go Up