Yes, the overwhelming majority of home subs are active, with integrated lowpass filters, level controls and phase switches. In the grand majority of stereo amplifiers, the subwoofer output has a fixed, generally non-optimal lowpass filter for some reason (when a simple preamplifier output would suffice). No, splitting the level-line signal between two consumers will not affect the performance.
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Review and Measurements of IOM NCore Pro PWR Amp
- Thread starter amirm
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Yes, the overwhelming majority of home subs are active, with integrated lowpass filters, level controls and phase switches. In the grand majority of stereo amplifiers, the subwoofer output has a fixed, generally non-optimal lowpass filter for some reason (when a simple preamplifier output would suffice). No, splitting the level-line signal between two consumers will not affect the performance.
thetrystero
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I think I will get the audiophonics mpa-s250nc based on your recommendation. Now I just need a dac to go with it. I was thinking the smsl su8 v2 if I were to go xlr. Am I right in assuming the xlr will go only between the dac and the amp, while the speakers are connected to the amp via RCA? If I do not gain much from balanced then I will go with the topping e30 instead.
I'm freaking out right now, because I have a very similar system on its way to me as we speak. I'll have a MiniDSP SHD as a preamp, a pair of XLRs in an Audiophonics MPA-S250NC, but an RCA going out of the SHD to an active subwoofer.
Now it looks like I'll be having the exact same problem of mismatched gain between the XLR and RCA outs going to the mains amp vs the sub - so my question is now, will I be able to compensate for it in the SHD, since I'll have them on separate channels? Is it as simple as lowering the mains channels' output gain? Could anyone point me to a resource to check/ask and really make sure?
Since I've just ordered the XLR-only power amp today (friday), I might still be able to change my order to the RCA version... But obviously I would rather stick with XLR interconnects if that will work.
The SHD has four DAC channels each with adjustable gains. So you can copy each stereo, for example, channel 1 to 3 and 2 to 4 then adjust the trims on the channels sent to the subwoofers. I would use the XLR connections where possible and use the trims or volume adjustment on the subwoofers.
This should not be an issue.
- Rich
That's what I'm thinking yes, but can it definitely work in the same way as the analog twice-the-voltage-output gain with XLR vs RCA, when applying the master gain across all channels? Is there a simple math behind it so I could just set the trims on a pair of channels numerically and call it a day? I really don't want to be questioning constantly whether my mains and sub levels are equally controlled by SHD's master volume control.
You could measure it with a mic at different levels but there is not reason to believe that the SHD does not apply the .5 dB attenuation equally to all channels.
- Rich
Oh, that's not what I'm worried about, I'm sure that part is reliable. What I'm asking is - can I calculate exactly, by how much I need to attenuate the channels I'm outputting via XLR, to match the RCA ones?
I am not sure I am following you. Eventually, there will be a volume output and that can be measured and adjusted. Powered subwoofers have volume settings. If you are using amplifiers simply play sine-wave tones and measure the volume at you position. Since you have an SHD, a USB MIC and REW could yield accurate results with sweeps to make sure you subs blend well.
The choice of XLR or RCA is irrelevant since even with the same amps, speakers and subwoofers can require different trims.
The SHD has the level trim necessary to make the adjustments but to know how to make them you need, at a minimum, a SPL meter (or app) and some pink noise or test tones.
EDIT: For speakers, you can play 0 DBFS sine waves and measure the voltage at the speaker terminals using a voltmeter.
- Rich
So I'm totally new in the game, coming from an integrated amp + single mains pair, no DSP. I'm well aware that putting together a well tuned system like I'm after isn't trivial, so I freaked out a bit after reading about that case quoted above. I then also remembered reading about someone else having a similar problem, but I didn't really think much of it at the time... so now here I am, thinking this might be one of the "gotchas" that wait for me to make me miserable.
Mainly I just don't want to end up like dkinric, having to change the hardware setup in order to achieve consistent volume control response on both mains and the sub. Could he have fixed it otherwise, with the sub's own volume control and a bit more persistence? Is it really any different, having the channel trim before master trim like on SHD, vs what he had to play with? I guess I'll need to find out myself, once everything is here and hooked up.
In any case, this is severly offtopic, many thanks for the help so far, I'll sleep a bit better while waiting for my XLR-only amp to arrive. Then I'll be making a separate thread if I'll get stuck, or even just to report on my success
Mainly I just don't want to end up like dkinric, having to change the hardware setup in order to achieve consistent volume control response on both mains and the sub. Could he have fixed it otherwise, with the sub's own volume control and a bit more persistence? Is it really any different, having the channel trim before master trim like on SHD, vs what he had to play with? I guess I'll need to find out myself, once everything is here and hooked up.
In any case, this is severly offtopic, many thanks for the help so far, I'll sleep a bit better while waiting for my XLR-only amp to arrive. Then I'll be making a separate thread if I'll get stuck, or even just to report on my success
I agree with everything @RichB has said. The comments made by @dkinric do not make sense. It almost sounds to me like he was dealing with typical loudness contour issues (bass seems low at low volumes) but I can assure you it has nothing to do with output voltage differences between RCA and XLR.
Michael
dkinric
Addicted to Fun and Learning
@kokoon , Hey man, don't freak out, it's all good. I seriously doubt you will experience a similar issue as me with an SHD as they were designed to do what you are trying to do, whereas I don't believe the Topping was.
What I experienced, and laid out above, was that I suspect that there were logarithmic scales at work that appeared to have different arc levels coming out of the XLR vs RCA outputs when used simultaneously and adjusted by the volume control on the Topping. One would think with all the volume adjustments available on the powered subs and Topping (as Pre), that one could compensate and dial in a good balance between subs and main speakers.
And you could.
The issue was that balance seemed to vary at different volume settings, and the whole system sounded better to me with the CA back in the chain as preamp. It's totally possible my preference was based on it being louder at lower volume settings due to the CA gain - and higher distortion, I'm sure, but still probably below audible thresholds.
Another factor was likely that in the Topping as pre setup, it was basically stereo bass, as each L/R channel went to one of my two subs, whereas in the CA as Pre setup the sub out was split, so it was mono bass - both subs working together. I think mono (summed?) bass is recommended for maximum impact.
I should clarify that my experience was 100% subjective, no measurements were done. I lived with it for about a week. Sounded clean, but not as balanced to my ears at different volume levels, so I switched it back and have kept it since.
FWIW, my future upgrade plans include an SHD or similar.
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rvsixer
Addicted to Fun and Learning
This is a simple one. The DX7 Pro has no sub integration capabilities, so the outcome is as expected. The miniDSP products on the other hand, are a tool of choice to integrate subwoofers. Find the proper place for the subwoofer(s), disabling all active controls of course, connect as necessary preferably all XLR but mixing in RCA is not a showstopper, level match gain matched sub(s) to mains, find the best crossover settings, fine tune level match to blend, run DIRAC if you must...done. They have many a tutorial on their website on how to do this.
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That's exactly what I was (and still am, actually) worried about. And I find it odd that nobody is addressing the "science" behind it - even if just to explain how it's not an issue. It's obvious that XLR is twice the gain of RCA, so what you experienced in your setup would be the same on SHD. So apparently it's possible to correct for that on SHD - but does the pre-master, channel trim really work differently than adjusting the sub's gain/trim knob, which you were trying? Everyone is saying just touch it up in SHD's channel mixer, or run dirac or something like that. But the (possibly) different voltage curves when attenuating master, due to XLR/RCA voltage difference, doesn't get addressed.
I can just shrug and think to myself - either it's so obvious that people don't even think to address it, or I'm not being understood.
Why do you think that there would be different voltage curves between RCA and XLR? Why do you think that output voltage between RCA and XLR needs to be equivalent when they are being routed to amplifiers with different gains?
If you want equivalent output voltage it is very easy to do with the SHD by attenuating the XLR outputs by -6 dB
Let's look at some examples at different volume levels.
0 dB - no attenuation
RCA: 2V * 10^(0/20) = 2.00V
XLR: 4V * 10^(0/20) = 4.00V
-10 dB - no attenuation
RCA: 2V * 10^(-10/20) = 0.63V
XLR: 4V * 10^(-10/20) = 1.26V
-20 dB - no attenuation
RCA: 2V * 10^(-20/20) = 0.20V
XLR: 4V * 10^(-20/20) = 0.40V
Now adding 6 dB attenuation to the XLR in the SHD.
0 dB - 6 dB attenuation
XLR: 4.00V * 10^(-6/20) = 2.00V
-10 dB - 6 dB attenuation
XLR: 1.26V * 10^(-6/20) = 0.63V
-20 dB - 6 dB attentuation
XLR: 0.40V * 10^(-6/20) = 0.20V
These are now exactly the same as the RCA output voltage with no attenuation.
Michael
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That's exactly what I was hoping for, so looks like order of attenuation operations is interchangeable? Cause you first did the master and after that the -6dB, which is not what we've been talking about. If that is the case, the same could be achieved at the end of the chain, on the sub.
Just to make it clear - I'm so grateful for all the effort you guys are making to ease my mind - I'm not being an idiot trying to prove anyone wrong, I just need this clarity for my own peace of mind. I guess this really is enough about this, in the thread about a review of a product that's almost completely unrelated to my questions
Just to make it clear - I'm so grateful for all the effort you guys are making to ease my mind - I'm not being an idiot trying to prove anyone wrong, I just need this clarity for my own peace of mind. I guess this really is enough about this, in the thread about a review of a product that's almost completely unrelated to my questions
rvsixer
Addicted to Fun and Learning
It was suggested to RTFM so you could believe at least the manufacturer on this if you didn't want to hear or understand the several correct answers here...so I do one step for you and give you just one link of several at the manufacturers website that explain subwoofer integration with master volume properly tracking output for all channels after correctly matching mains to subs:
https://www.minidsp.com/applications/audio-streaming/sub-integration-with-shd
Yes, from a volume perspective the order of operations is interchangeable. If you don't believe me I suggest you take some voltage measurements with a DMM as a learning exercise
. You can definitely achieve the same thing at the end of the chain (which has been suggested many times in this thread).Michael
wyup
Active Member
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So any RCA/XLR cable will do?
Specs related, does an NC122MP based power amplifier in XLR-only configuration perform better than a RCA one?
I'm considering using an unbalanced source with the XLR option amp, if there is no penalty for it, as long as I'm using a preamp with both XLR and RCA (can't do RCA input to XLR output though).
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