Reducing the decibels by 20%? Do you mean reducing 100dB to 80dB? Do you mean reducing the level to 1/5th of the amplitude (-14dB), or 1/5th of the power (-7dB)
Decibels is a logarithic scale, 10 times the power is an increase 10dB, 1/10th the power is a reduction by 10dB. You don't multiply or scale dB, you add or subtract, that's why they are so useful.
Decibels is a logarithic scale, 10 times the power is an increase 10dB, 1/10th the power is a reduction by 10dB. You don't multiply or scale dB, you add or subtract, that's why they are so useful.
Indeed. I have no idea why input level trim would be so limited stock, that can't be more than around 8 dB of adjustment range.
In return, the woofer and tweeter level adjustments seem to have considerable leeway, much more than I'd expect to even out production variation. Odd.
I'd swear I've seen that schematic before - what is it?
Yes Behringer B2031. Ive kind of grown to like then. I have a second pair i'd like to modify. In the meantime. Well there's a shorcut. I gess I can just pull the tweeters and woofers back and call it a day. That should be enough.
I hope you've got a decent speaker measurement setup then, 'cause you'll need that to get the frequency response sorted back out. (Though an out-of-phase test signal with both speakers face to phase may help in nulling.) Not to mention getting both to the same input sensitivity.
Would be interesting to observe the effect on output noise levels though, if any (B2031As are known for having some hiss). Those are some really good speakers for the price.
I did the math again, and now got a stock adjustment range of 12.29 dB - a.k.a. about the difference between +4 dBu and -10 dBV, or the +/-6 dB trim advertised. Still, not luxurious - my K+H O110s are claiming to be accommodating a range of +6 to -18 dBu (though I think this may be incorrect; they've got a nominal input sensitivity of +6 dBu with up to 24 dB attenuation, so that would actually be +6 dBu to +30 dBu, but it could still be if those are the values for 94 or 100 dB SPL output). Swapping R90 for 1k would increase the range to 21.17 dB. 680 ohms would net you 24.16 dB.
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Klein and Hummel. Now those are some monitors. I recently stumbled across an 8 channel balanced line attenuator but it's $500 that I can't spend on level control however i do need some control over the line outs from my 8 channel DAC. What are my options for making something. I've seen a few different circuits from 4 gang DACT stepped attenuator to one that appears to to shunt the hot and cold. Any suggestions? I want to maintain as much transparency as possible.
So software/driver-level attenuation is not cutting it? I'd hope that this would do, because then you only have to drop monitor input level enough to minimize DAC noise when compared to noise inherent in the speakers.
An 8-channel level control (do you need all channels coupled?) with balanced I/O is not without its complexity, but an 800$ price is probably owed mostly to the small numbers these things would be selling in. If you look at the complexity of a mid-sized compact mixer, there's little reason to suspect that something like this (presumably with a PGA, perhaps the kind used in AV receivers for years now) couldn't be made for $100-150 in volume if you really wanted.
I don't even dare asking what the 8-channel equivalent of RME's ADI-2 DAC with its combination of digital attenuation and switched output stage gain (Auto Ref Level feature) would cost.
An 8-channel level control (do you need all channels coupled?) with balanced I/O is not without its complexity, but an 800$ price is probably owed mostly to the small numbers these things would be selling in. If you look at the complexity of a mid-sized compact mixer, there's little reason to suspect that something like this (presumably with a PGA, perhaps the kind used in AV receivers for years now) couldn't be made for $100-150 in volume if you really wanted.
I don't even dare asking what the 8-channel equivalent of RME's ADI-2 DAC with its combination of digital attenuation and switched output stage gain (Auto Ref Level feature) would cost.
It is my understanding that we should not attenuate our digital signal. I really only need my main to be balanced and attenuated. my woofers are se, my meters are unity and my headphone amp has it's own att.
If you use the XLR input, you can use an L-pad (in-line attenuator).
For example: In-Line XLR Attenuator Pad 20dB
Using such an attenuator will eliminate the need to hack into the speaker and also allow you to experiment with which attenuator suits your taste.
Tom
For example: In-Line XLR Attenuator Pad 20dB
Using such an attenuator will eliminate the need to hack into the speaker and also allow you to experiment with which attenuator suits your taste.
Tom
This understanding may well be outdated.
24-bit DACs have been available for almost two decades now, and there are few things as utterly loss-free as high-precision (e.g. float32) digital attenuation. New audio devices coming out these days tend to sport an output dynamic range in excess of 110 dB (18 bits effective) more often than not, even onboard sound. Plenty of leeway for an (at best) 16 bit signal to make it through unharmed.
(RME even makes some DACs that have several output stage gain selections and will automatically pick the best one depending on volume control setting, netting you a dynamic range between 117 dB at +1 dBu full-scale to 120 dB at +19 dBu, for an effective total of 135 dB covered. Alternatively, an Okto DAC8 Stereo will provide at least 127 dB in one go at +4.2 Vrms / +15 dBu, other levels upon custom order for a bit extra.)
If whatever you are using for D/A is not known for problems with low-level nonlinearity, I would compare noise levels with B2031A input plugged / unplugged at min / max level trim adjustment while having an essentially inaudible test signal playing (something at -90 dBFS or thereabouts, e.g. fairly easily generated in Audacity with the tone generator and two passes of amplification at -40 dB - be warned that >16 bit output may require switching to WASAPI in Windows). Actually even digital silence may do if your equipment doesn't have extra-clever muting that turns off the DAC automagically. Your findings are likely to be one of the following:
a) same output noise both with and without DAC at min and max input trim - DAC noise is not a problem then
b) elevated input noise level at maximum input trim but basically a wash at minimum - leave at minimum then
c) elevated output noise even at minimum input level trim.
Only case (c) is actually problematic and calling for either troubleshooting (>16 bit output format active? unbalanced connections?), a passive attenuator as mentioned (maybe 12 dB) or even a DAC upgrade.
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