New to Dirac - a couple of questions and a lot of graphs

[Kal Rubinson]

You can unscrew the cap on the umik-1 and flip some toggle switches to increase the internal gain of the mic. That's what I did.

??? Short of using pliers, how did you do that?

[wgscott]

As I remind my children, don't use your teeth.

[flak]

Hi Flavio,

 

Thanks for your message. I had time on my hands and a quiet environment this morning, so I took the plunge. My first surprise was that, with the UMIK-1 on Mac OSX, quite a high sound level is required, even with the input gain at its maximum. This made me fear for my tweeters, and this also convinced me that my concern for low-level background noise was probably misplaced. Since repeating these potentially tweeter-damaging test noises at quite high SPLs nine times frightened me quite a bit, I measured only my sofa (while initially I thought that I would also measure the chair in front of my computer).

 

The main outcomes were:

• Imaging improved significantly thanks to Dirac,
  
• Sound remains very clear (Dirac does not muffle anything)
  
• My tweeters still work, and
  
• Dirac revealed that my subwoofer is not functional anymore.
  

 

Dirac did nothing to my sub: the frequency response below 70Hz is flat on all measurements. What it did is that it revealed that it does not work anymore. It is quite a bit embarrasing that I did not realise this for myself even if, in retrospect, I understand why, lately, I felt that some of my favourite organ CDs lacked oomph. Well, it's quite clear why now. Still, the ability of the ear-brain system to reconstruct what is missing keeps astonishing me.

 

Hello Boris

 

do'nt feel embarassed at all... your last remark is correct and interesting, it's the phenomenon of reconstruction of the missing fundamental. If you listen to the following two sequences they may seem to be played by two different instruments, the notes seem to have a different tone but the same pitch nonetheless (I'm not sure my english is good enough)

The difference between the two sequences (that are the same) is that the fundamental only has been removed in the second one (but all of the harmonics are present):

 

http://fisicaondemusica.unimore.it/Fondamentale_mancante.mp3

 

Ciao, Flavio

[Boris75]

Yes, my understanding is that there are dip switches inside the mic... and I heard that the mics have been delivered in the past with a setting that was lower that the present one.

 

Flavio

 

Thanks for your remark. The serial for my mike is 700-3045: does that mike it an old one with low gain or a new one with "normal" gain?

 

I have a couple of other questions: I bought my mike from Cross Spectrum Labs who calibrated it. If I manage to change the gain inside without breaking the mike in the process, will the calibration file (which includes no sensitivity) still be valid?

[flak]

Hello Boris,

 

I do not know about the serial numbers, I think that the right place to get that kind of info is miniDSP itself, they have a friendly tech support forum with a section which is dedicated specifically to the UMIK-1: MiniDSP :: Topics in UMIK Questions (1/3)

miniDSP may also inform you about modifying the gain (frequency response should not be affected)

 

In exchange for this info you will report the outcome in this Forum, done deal?

 

Flavio

[Boris75]

Hello Flavio,

 

Thank you very much. I will do so.

 

Does Dirac Live use the sensitivity factor reported between quotes on the first line of calibration files?

 

I am asking the question because I wonder whether my experience with the UMIK-1 could be linked to my use of a calibration file provided by Cross Spectrum Labs (which includes no sensitivity factor) while the calibration file from the MiniDSP website does include this sensitivity factor at the beginning.

 

Thanks,

Boris.

[LocutusEstBorg]

Where do I sit while taking the measurements? The sound starts immediately when I press Spacebar or click the Start button. I am unable to leave the area in time. Can I just sit in the chair? Can I slide down the chair and keep the mic where my head would be?

[Kal Rubinson]

Where do I sit while taking the measurements? The sound starts immediately when I press Spacebar or click the Start button. I am unable to leave the area in time. Can I just sit in the chair? Can I slide down the chair and keep the mic where my head would be?

 

1. As far from the speakers and mic as possible.

2. Out of the lines-of-sight between each speaker and the mic.

[beanbag]

??? Short of using pliers, how did you do that?

 

I just realized that I never answered this question.

 

I used a set of tweezers with pointy ends and stuck the two ends into the two small holes on the cap.

[Kal Rubinson]

I just realized that I never answered this question.

 

I used a set of tweezers with pointy ends and stuck the two ends into the two small holes on the cap.

 

Thanks. Gain has not been a problem for me but that is good to know.

[Liam]

This is a very helpful and informative thread. I am checking out the 2 channel trial version at present. My intention is to purchase at the end of the trial.

 

I have been having bad thoughts of upgrading my amplifier to a secondhand highend dedicated stereo one. I decided though that I should start at the front end. I bought a new AMR DP-777 dac....delighted with that. Right, is it time now to squeeze my finances and press on to locate a suitable amplifier? What about checking out room correction first? Hardware room correction is out. This is the lounge, so it is what it is. Heavily carpeted wooden suspended floor, cloth covered three piece suite, speakers mounted on inverted spikes on a custom wooden entertainments unit, on which the 42 inch plasma screen is mounted, and drapes behind. Not ideal overall.

 

Second good decision was to check out the room contribution to the overall sound. At least now if I audition amplifiers in due course, I feel I will be able to analyse their qualities without the room masking and leading me erroneously to try to correct the room with an amp which might be less than musically neutral.

 

First of all the seating area is against the back wall. Due to domestic requirements the tv and gear are set up firing across the short dimension of the room. The room is relatively small. Not a cube thankfully. The 9 readings were taken to form a rectangle encompassing the seating area 3mtrs.wide. All the rearmost readings were at ear height. The front ones were again all at the same height, but lower, by placing the tripod on the floor, which had the effect of lowering the top of the upward facing XTZ Pro mic by about 40cm. Below are the results. I would appreciate comments in general, from Flavio in particular of course, on both the results and my technique, and if/how they might be improved.

 

 

[EuroDriver]

This is a very helpful and informative thread. I am checking out the 2 channel trial version at present. My intention is to purchase at the end of the trial.

 

 

[ATTACH=CONFIG]14117[/ATTACH]

 

[ATTACH=CONFIG]14118[/ATTACH]

 

IMHO, you have a pretty acoustically nice room to work with, no deep suckouts.

 

The next place I would spend my dime would be on a subwoofer. Dirac allows you to integrate a subwoofer very nicely, and the 805's appreciate the help

 

On my set up, I get the most pleasing setup when I limit the high frequency window so that Dirac processes the high frequencies less. Your mileage will vary !

[Youreye]

Hi!

 

Kinda similar what I get with the same setup (firing across the short dimension of the room too).

This is without the closed sub. With the sub I basically don't get deeper but it offloads the Victa's 300 a lot (no highend)

[Liam]

Mmm, I don't envisage a sub, not in the foreseeable anyway. With a wooden suspended floor (vibration), and the small room dimensions, perhaps seamless integration would be difficult. The B&W 805S have audible in room output to about 39hz. Would it really be worth the effort and expense to add a sub for music only?

[Youreye]

If set properly you can only gain with the sub in stereo. If nothing else you will offload the main speaker so they can articulate better the lower mids as well the amp can play clearer not driving the deep bass so that in the end you can play much louder as well.