What setting to use on my active monitors

[Maurits]

Hello everybody,

I'm feeling kind of stupid for asking this, especially because I asked before. I think it was Mark who responded and he suggested I study the specifications in my manuals of both my monitors and my DP. Further I searched in the tutorials that Phill posted (a regular gold mine. Thank you so much!!) and the technical explanations CMaffia offered (also very useful and also many thanks!!). However I still don't understand what setting I should use on my active monitors.
Maybe someone can enlighten me. I'd like to know what setting to use and also why that is.
The specs on the DP -as everybody here probably knows- say something like:
0dBFs gain +10,2 monitor out (max) +14dBu
-16dBFs monitor out (nominal) -2dBu
The specs on the monitors say:
Input level for 85dB SPL @ 1m (+4/-10)
Input level for max peak SPL (+4/-10)
The settings on the monitors are nominal, +4dB and -10dB

It makes no sense to me...
Thank you very much in advance!

kind regards,
Maurits

 

[Mark Richards]

The settings on the monitors are nominal, +4dB and -10dB...It makes no sense to me...I'd like to know what setting to use and also why that is

It's very simple. You match the nominal analog audio power output of your gear to the nominal audio power input sensitivity of your active speakers' amplifier (as it's not specified for your speakers, assume the power rating is stated in dBu).

Here's why.

Comparable Measures of Analog Audio Output Power:
-12.22dBV = -10.00dBu = 0.2449 volts
-10.00dBV = - 7.78dBu = 0.3162 volts (nominal consumer and home studio level)
- 4.22dBV = - 2.00dBu = 0.6153 volts
+1.78dBV = +4.00dBu = 1.2275 volts (nominal professional studio level)

OM Specifications Page - Stereo Out Jack:
Connector: RCA pin jack
Rated Output Level: -10dBV (indirectly correlates to OM Level Diagram/Stereo Out digital -16dBFS level)

OM Specifications Page - Monitor Out Jack:
Connector: 6.3mm (1/4") Tip/Ring/Sleeve (TRS/Balanced) standard jack
Rated Output Level: -2dBu (indirectly correlates to OM Level Diagram/Monitor Out digital -16dBFS level)

Thus the Monitor Out jack produces more audio power (2x the voltage) than the Stereo Out jack when recording at the same -16dBFS digital recording level.

So...for your speaker to achieve an 85dB SPL at the specified distance from the speaker (that's "sound pressure level where 0dB is the threshold of hearing, and is a different measurement than dbV/dBu):

• If you use the Stereo Out jacks - the closest match to your speaker input setting is: -10dB.
• If you use the Monitor Out jacks - the closest match to your speaker input setting is: + 4dB.

Audio Power Level Diagram in the OM:
If you record at digital -16dBFS, you will achieve the specified nominal analog audio power levels (0.3162 volts/Stereo Out; 0.6153 volts/Monitor Out), giving you both ample digital headroom for transient spikes in your recordings before reaching 0dBFS, and a nice safety margin to avoid analog over-driving/distorting/damaging your speakers.

 

[Maurits]

That, again, is a very quick reply. Thank you so much! Although the dBu and the dBV part still is incomprehensible for me, I at least know now what setting to use. Non the less I will look up what the terms mean, study the technical issues and try to understand. That will probably be useful in the future.

Again, thank you so much! This forum and it's tireless experts are a true gem!

 

[Mark Richards]

...the dBu and the dBV part still is incomprehensible for me...

Very simple: both are a measure of analog audio power (electrical voltage generated by the audio signal).

Each uses a different reference point:

• Consumer gear uses dBV, and 0dBV is 1 volt.
• Pro gear uses dBu, and 0dBu is .775 volts.

These are internationally established standard reference points for electrical engineering.

There's a post in the Equipment Tips sticky that goes into more detail about dBu and talks about the relationship of dBu and dBFS.

 

[Arjan P]

This is quite technical, so it may help - or it can confuse more, but there is more here especially about the difference between the 'V' and the 'u' (which used to be 'v')..:
https://en.wikipedia.org/wiki/Decibel#Voltage

 

[Maurits]

Thank you Arjan! This wiki lemma is however way over my head. Although math and science ware among my strong points in my education, it is too long ago to remember all that. When I have my studio up and running (finally) I'll dive into that a little bit. Anyway, again thanks for the effort!

 

[Maurits]

Hello, it's me again.

On Marks recommendation I switched my monitors to +4dB. What strikes me as odd though is that the volume increases in comparison to the nominal setting. Intuitively I would say that when the power on the monitor outputs is about twice as high as the stereo outputs and the monitor setting on the latter is recommended to be -10dB, one increases the sound level difference between the two outputs by setting the monitors in the respective settings. So this +4/-10dB settings apparently are not some kind of compensation for the difference in output power?

 

[Mark Richards]

In audio, the voltage power output = audio signal amplitude (loudness); and voltage power input = audio input sensitivity.

I think a simple analogy is trying to connect a firehose to a garden hose.

The water pressure of the firehose (+4dBu amplitude of the audio signal) is too strong for the garden hose (-10dBu speaker input sensitivity). This creates an overload going into the garden hose (overdrive of the audio signal's sound pressure level coming out of the speaker).

In reverse, the output pressure flow of the garden hose (- 10dBu audio signal amplitude) into the firehose (+4dBu speaker input sensitivity) does not create overload, but it will be too weak to produce the desired water pressure required of the firehose (underdrive of the audio signal sound pressure level coming out of the speaker).

That's why you would want to closely match dBu to dBu when connecting audio gear.

 

[Maurits]

I see, that analogy makes sense to me. But is it a right assumption that you need to crank up the volume knob pretty much to achieve the same volume out of the moni's when connected to the stereo outputs while set on -10dB in comparison to when they are connected to the monitor outputs while set on +4dB?

 

[Mark Richards]

This is your monitor speakers' performance spec:
Input level sensitivity for 85dB SPL @ 1m (+4/-10)

If you match dBu to dBu you should get the indicated 85dB SPL at 1 meter distance from the speaker without needing to adjust the monitor speaker's volume control from its optimum position and without overdriving or underdriving the speakers.

You can verify that using an SPL Meter app on your smartphone.

 

[Maurits]

I see. So if the power from the source is higher and the moni's are +4dB (louder), the SPL is the same as when the power from the source is lower and the moni's are -10dB (less loud). That is hard to understand for me. I guess that has to do with the impedance?

 

[Mark Richards]

Impedence is irrelevent - high impedence is assumed as these are all line-level signals.

But this is now going way beyond anything specific to the Porta-studios.

There's a Recording 101 sub-forum on this site. If you want to further discuss, by posting your questions there you can tap into the much broader expertise of all the members of the tascamforum.com website, many of whom are very knowledgeable about technical subjects.

 

[Maurits]

Ah, that's alright! Anyway, although I don't understand the science behind it all, for the practical issue I addressed in the first place, I'm out of the water now. Again, thank you so much!!