Speaker input conversion from volts to dB help requested:

JeffF

New member
Through a 3rd-party retailer, I obtain a manufacturer’s frequency graph, which is based on 0.1 volts input (as stated on the engineers’ notes).

The reason I need to know conversion of voltage to dB input is because the low-end rolls off quite a bit (approximately -15dB) from 80Hz before reaching its rated 40Hz response bottom.

Hopefully, the graph was produced at a higher testing input than -10dB. In which case, my using a -10dB input should produce much less roll off at bottom.

Therefore, conversion help is appreciated as I am not mathematically able to work such formulas as some of you are. Your help in working out the formula is appreciated.

Thanks--JeffF.
 
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Hello Spantini,

I appreciate the conversion calculator on provided website link.

In establishing a rudimentary knowledge base (in this rather specialized area), over the last few days I reviewed material on dB applications and terms, which I understood of basic concepts. However, I am not confident I correctly applied that information to the conversion calculator.

If convenient of your time, would you double check my results on two basic calculations?

If you may further assist, here is the conversion calculator I used: “How to Calculate Decibels?” selection at the bottom of page you provided. To save you time, I used this page: dB calculate - decibel calculation dB calculator voltage power ratio sound pressure level matching dBA SPL sound pressure intensity ratios converter thd percent % audio engineering impedance matching bridging - sengpielaudio Sengpiel Berlin.

Then I used the section titled: The formulas for voltage and power and the level calculation.

With the 2 operations I did (briefly outlined below), I included my steps (underlined), as I applied terms/values entered into the conversion calculator.

1) In wanting to determine the line-level dBV input (that the manufacturer used in testing the stated response of a woofer), the only figure I had to work with was 0.1V input (as the limited information I could obtain from the manufacturer). I arrived at approximately (rounded) -20dBV input using the conversion calculator.

Conversion operation steps: I went straight from entering the voltage of 0.1V to dBV conversion.

That seemed an unusually low dBV testing level. However, if correct it may possibly be why the manufacturer’s website does not show it used to arrive at their stated Hz response . . . or I may be wrong in conversion.

2) My Tascam DP24SD unit has a monitor jack rated at -2dBu output. I need to convert dBu output to dBV output, so I know what dBV line-level I am sending to sub/monitors. By using the conversion calculator for the -2dBu figure, I arrived at approximately (rounded) -4.2 dBV.

Conversion operation steps: I first entered the -2 dBu to get the audio voltage. Then I entered that voltage figure into the box for voltage to dBV conversion.

If I’ve got the conversion calculator right on this second operation (for -2dBu), then I’ll be confident to convert other dBu values to dBV for a common output term (dBV) sent from my Tascam to monitors—doing this for myself in the future with various applications using different dBV line levels.

At your convenience, if not imposing, I’d appreciate your double checking both of these operations for me. Again, in light of my brief familiarity of terms, I may have selected the wrong terms in steps of conversion.

I’ll be making purchase decisions in a couple months based on such information, so I appreciate your experience extended further if your time allows.

Most gratefully for what you've done thus far and any further help, JeffF.
 
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You got the right numbers. dbV is referenced to 1V, 0.1V is 1/10th of that, and 1/10th is exactly -20db no matter what it's 1/10th of. The dbu to dbV conversion is a little tougher, but the calculator gave me the same value you got, so....
 
The dbu to dbV conversion is a little tougher, but the calculator gave me the same value you got, so....

Respectfully, to be clear were you referring to dBu to dBV numbers as what you got of the same value or only the voltage input to dBV conversion mentioned in the earlier sentence (not shown in quote)? If referring to dBu to dBV, is that how you would have worked the problem--I can understand concepts about electronics, but math, whoo!

Separately, drawing on your knowledge, would there be any technical reason a signal routed from a source's stereo RCA O/P jack--from my Tascam unit in this case--would be less of quality in any way compared to the unit's monitors' 1/4" O/P jack? (The signal would be sent first to a sub then monitors.)

The reason I ask, if I am correct about the dBu to dBV conversion figuire, I may need to use the stereo jacks if no quality signal issue--dBV input rating for the monitor jack would not reach the sub's input rated response at -3 dBV. However, Tascam's stereo O/P jack is rated at -10dB to max +6 dBV that would be within the input spec for the sub.

Thanks, JeffF.
 
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