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MiniDSP - Page 41

post #1201 of 1592
12/18/12 at 7:08am
what about using something like a cleanbox pro between the avr and the minidsp? couldnt you use that to control the input voltage to the minidsp?
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post #1202 of 1592
12/18/12 at 8:05am
Taking a step back for a minute I realize this could be confusing because we're talking about the maximum signal output a the minimum Subwoofer setting.

So, here's the process of what I'm discussing:

1) Set the SW channel a low as it goes (-10dB on my Pioneer SC-05)
2) Set the receiver to 0dB (reference)
3) Play a DTS file that contains the worst possible audio content in terms of generating a maximum amplitude LFE signal with all the speaker set small. This is a track that has a -0.01dBFS 40Hz test tone in all 6 channels (5.1).

This generates a signal on the SW output that has the highest possible amplitude (worse case) while the receiver is set to deliver the lowest possible SW signal at reference.

To put this in the obligatory car analogy think of this of this as the max speed a car can hit in first gear. Sure, the car can go faster in higher gears, but if you want to know how fast the car can go in the lowest gear you've got the run the engine up to the redline. The DTS track being played is akin to running the engine up to the redline. The SW channel being set to -10dB is akin to having the car in first gear.

In the case of my Pioneer Elite SC-05 this is what you get on the output under that condition:



The output is 4.48Vrms / 13.1Vpp.

Based on my testing, this (below) is the maximum signal the MiniDSP can take without clipping the input:



The input level is 4.76Vrms / 13.5Vpp

This means that the worst case DTS content played at reference on the master volume (with the SW level trim at -10dB) has only 0.52dB of headroom before clipping the MiniDSP input. So, if you push past reference you will clip the input of the MiniDSP. If you're playing at reference and apply some signal gain in the MiniDSP (filters that boost, LT, shelf filters, etc) you will probably clip the output. This last scenario may be avoidable by playing with the input / output gains in the MiniDSP. I will test this later today.
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post #1203 of 1592
12/18/12 at 8:11am
Quote:
Originally Posted by brian6751 View Post

what about using something like a cleanbox pro between the avr and the minidsp? couldnt you use that to control the input voltage to the minidsp?
Probably... I'm not that familiar with it. If it can decrease the amplitude of the signal going through it then it would do the job. Frankly, a passive resistor divider in front of the input should work too.

Edit: typo
Edited by Stereodude - 12/18/12 at 9:27am
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post #1204 of 1592
12/18/12 at 8:42am
Quote:
Originally Posted by Stereodude View Post

Quote:
Originally Posted by rock_bottom View Post

Let's take a hypothetical example of subs that have the required acoustic output, driven by Crown XLS amps with enough output power to drive the subs to this level. Since the input sensitivity of the Crown XLS is 1.4VRMS, there is no problem in this configuration with the MiniDSP in the nominal case.
That's not necessarily true as I keep stressing.
Quote:
It's not relevant what the maximum possible receiver SW output voltage is, unless it's lower than the power amp input sensitivity. For preamp outputs using op-amps with +/-15Volt supplies, these can typically put out more than 12 Volts peak before clipping. But they never need to, because the power amp has given up the ghost long before this.
I'm not sure it's entirely irrelevant but the conversation has been focused on the maximum amplitude the receiver can generate at the minimum SW output setting from the receiver at reference on the master volume and the maximum input signal the Balanced 2x4 MiniDSP can handle. What thread have you been reading?

The one that's gone off the rails.

Think of it this way. There are varying subwoofer sensitivities and varying subwoofer amp gains. If one considers the SPL to be fixed (say, at reference), then that means the receiver SW output must vary when set to 0dB to take the differing sub sensitivities and sub amp gains into account. Presumably this is part of the calibration. You're making the assumption that this level is fixed, which, if you think about it carefully, rather than insulting others, must be a false assumption.
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post #1205 of 1592
12/18/12 at 8:52am
Quote:
Originally Posted by rock_bottom View Post

The one that's gone off the rails.
Think of it this way. There are varying subwoofer sensitivities and varying subwoofer amp gains. If one considers the SPL to be fixed (say, at reference), then that means the receiver SW output must vary when set to 0dB to take the differing sub sensitivities and sub amp gains into account. Presumably this is part of the calibration. You're making the assumption that this level is fixed, which, if you think about it carefully, rather than insulting others, must be a false assumption.
Insulting??? What the heck are you talking about? confused.gif

I made voltage measurements with the master volume at reference (0dB) and the SW channel level trim at 0dB. This can clearly clip the input of the MiniDSP with DTS encoded content. I also made measurements with the SW channel level trim at -10dB. This just barely clears the maximum input level the MiniDSP allows with DTS encoded content with the master volume at reference. If someone has the same gear I do it can only just barely be set up to allow reference level playback without clipping the signal fed to the subwoofer amp, and playback above reference is out of the question. These are simple facts. I haven't assumed anything to be fixed. I've made a series of measurements under two different setup conditions. The measurements show proper calibration is only just barely possible and hinges on what you're doing in the MiniDSP and how it works internally. I haven't a clue how this can be possibly be seen as insulting...
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post #1206 of 1592
12/18/12 at 9:13am
Quote:
Originally Posted by Stereodude View Post

Insulting??? What the heck are you talking about? confused.gif
I made voltage measurements with the master volume at reference (0dB) and the SW channel level trim at 0dB. This can clearly clip the input of the MiniDSP with DTS encoded content. I also made measurements with the SW channel level trim at -10dB. This just barely clears the maximum input level the MiniDSP allows with DTS encoded content with the master volume at reference. If someone has the same gear I do it can only just barely be set up to allow reference level playback without clipping the signal fed to the subwoofer amp, and playback above reference is out of the question. These are simple facts. I haven't assumed anything to be fixed. I've made a series of measurements under two different setup conditions. The measurements show proper calibration is only just barely possible and hinges on what you're doing in the MiniDSP and how it works internally. I haven't a clue how this can be possibly be seen as insulting...

This is what's insulting, "Of course not. He's just spouting off uninformed nonsense because he didn't bother to read the last several posts."

You are forgetting that the output voltage you're measuring is only pertinent to your model of receiver. Your stating this as if everyone will have this problem if they set the sub output to -10db, set the volume to 0db, and play the same track. That's simply not the case at all.

All the varying receivers and amps will have varying voltage outputs and sensitivities, and your test only pertains to one receiver and one amp so far.
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post #1207 of 1592
12/18/12 at 9:22am
Quote:
Originally Posted by lukeamdman View Post

This is what's insulting, "Of course not. He's just spouting off uninformed nonsense because he didn't bother to read the last several posts."
I'm pretty sure I addressed that at you, not him. If he's insulted because I pointed out your lack of reading comprehension he's not going to last long here.
Quote:
You are forgetting that the output voltage you're measuring is only pertinent to your model of receiver. Your stating this as if everyone will have this problem if they set the sub output to -10db, set the volume to 0db, and play the same track. That's simply not the case at all.
All the varying receivers and amps will have varying voltage outputs and sensitivities, and your test only pertains to one receiver and one amp so far.
Actually, I've measured two receivers and 0 amps. I haven't brought any amps in this. If you want to believe the my two receivers are outliers from the norm feel free to measure some other ones and prove it. Otherwise you're making a speculative claim that may be erroneous. I never said this would affect everyone. I've listed the 3 conditions necessary to make this a problem in more than one of my posts.

I'm afraid I can't make this any more simple. If you chose to willfully read thing from my posts that I've not said I can't help it.
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post #1208 of 1592
12/18/12 at 9:28am
Quote:
Originally Posted by Stereodude View Post

I'm pretty sure I addressed that at you, not him. If he's insulted because I pointed out your lack of reading comprehension he's not going to last long here.
Actually, I've measured two receivers and 0 amps. I haven't brought any amps in this. If you want to believe the my two receivers are outliers from the norm feel free to measure some other ones and prove it. Otherwise you're making a speculative claim that may be erroneous. I never said this would affect everyone. I've listed the 3 conditions necessary to make this a problem in more than one of my posts.
I'm afraid I can't make this any more simple. If you chose to willfully read thing from my posts that I've not said I can't help it.

He said "rather than insulting others", so you're proving him to be correct.

I think it's a safe assumption that different makes/models of receivers will have varying output voltages. I don't think anyone will think that's an "erroneous" claim...
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post #1209 of 1592
12/18/12 at 9:37am
Quote:
Originally Posted by lukeamdman View Post

I think it's a safe assumption that different makes/models of receivers will have varying output voltages. I don't think anyone will think that's an "erroneous" claim...
Yes, but that wasn't the crux of your original claim now was it? I'm sure there is variation between them. However, you're posts clearly suggests that my receiver is an outlier case with an abnormally high voltage output and says that other people won't have this issue. I'm sure you'll be along shortly with measurements to prove your assertion right?

And, again... I made no claims that this would affect everyone. I'd listed the conditions that would cause it to affect people several times. If you want to stick your head in the sand and pretend the MiniDSP is the best Sub EQ device and doesn't have any potential issues to be aware of, feel free. I on the other hand, know it's limitations and potential issues. Apparently posting facts and alerting people that under some conditions with some gear the MiniDSP could clip the signals in their LFE playback chain is upsetting to some people.

Edit: typo
Edited by Stereodude - 12/18/12 at 11:24am
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post #1210 of 1592
12/18/12 at 4:52pm
Quote:
Originally Posted by Stereodude View Post

*Disclaimer* This post may be hazardous to the enjoyment of your MiniDSP. Continue reading at your own risk */Disclaimer*
Today I did some testing of my balanced MiniDSP 2x4 and found what I believe to be some fundamental issues with it that make it potentially problematic for LFE equalization duty if your receiver has a strong voltage output. Specifically the MiniDSP has a good probability of acting as a signal level restriction or clipping the LFE signal in the playback chain of people listening at reference.
Some things I learned today:
1) The “balanced” output and input of the balanced MiniDSP maxes out at ~4.6VAC (RMS). Specifically this is the point where increases of the voltage on the input are not met with corresponding increases in voltage on the output.
2) The “unbalanced” (RCA) output of the balanced MiniDSP is at effectively half the voltage level of the “balanced”. This is a loss of ~6dB from the input.
3) The subwoofer output from my THX certified Pioneer Elite SC-05 can exceed 4.6VAC (RMS) under a lot of circumstances.
I used a True RMS multimeter for all my measurements. I used a 40Hz sine wave as the basis of my testing. It was at -0.01dB from full scale. I used both .wav files and 1.5Mbit DTS 5.1 playback via HDMI from my HTPC. The receiver was set at 0dB (reference) and the SW output level trim was set to 0dB. All speakers were set to small and crossed at 80Hz. Additional sound processing was disabled (DPL IIx, etc). Here are the voltages I measured:
DTS 5.1
channel(s) 40Hz sine wave was in – measured VAC (RMS)
LFE - 7.87
Left - 2.76
L&R - 5.5
LFE+L&R - 9.23
All 5.1 - 9.47
Wave playback
channel(s) 40Hz sine wave was in – measured VAC (RMS)
L - 1.703
L&R - 3.43
Leaving the master volume at 0dB and backing the SW output level trim in my Pioneer down to -10dB, the lowest possible setting, and measuring the worst case DTS scenario (the 40Hz sine wave in all 6 channels) again I got 4.44VAC (RMS). This tells me 2 things. First, the Pioneer is probably clipping in the first 0dB SW level test since the extra 10dB should give a voltage gain of ~3.16x and the measurements only show ~2.13x. Second, that measured 4.44V is basically at the I/O limit of the balanced MiniDSP. This means that at reference even with the SW output channel trim turned down to -10dB it’s possible for content to push the input of MiniDSP right to the limit. Further, if you apply any signal boost with filters the MiniDSP doesn’t have the headroom to output a signal that hasn’t been clipped without decreasing the levels with the plugin software.
So, at reference you can just barely keep things from clipping by decreasing the SW output as much as possible and turning the MiniDSP down internally. For playback above reference there's no solution that I can see short of inserting a voltage divider ahead of the MiniDSP on the input side.


Do you have enough room to raise the speaker trims?
This would net you a lower MV for RL and a lower sub-out voltage.
You're pretty close at -10 sub-out trim.
Maybe a bit of an increase to the speaker trims, knocking off a few dB of sub-out. will do the trick.
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post #1211 of 1592
12/19/12 at 4:02am
Quote:
Originally Posted by Oliver Deplace View Post

Do you have enough room to raise the speaker trims?
This would net you a lower MV for RL and a lower sub-out voltage.
You're pretty close at -10 sub-out trim.
Maybe a bit of an increase to the speaker trims, knocking off a few dB of sub-out. will do the trick.
That's another possibility. Increasing the other speaker's level trims and moving reference down from 0dB on the master volume to something less would create a bit more headroom in the LFE chain.

I did some additional testing yesterday and found that you can also create some additional headroom in the MiniDSP for gain from filters with the input or output trims as long as you're not clipping the input.

In my test first I lower level for the input by 6dB in the GUI.


Note that the input level meters don't read dB. A 6dB reduction show up as -12. confused.gif

Then I created a 6dB boost at 40Hz.


That restored the amplitude of the output (per the level meters in the GUI).


Here's what shows up on the scope of the input vs. output.


No clipping. Also, the behavior is the same if you reduce the output level trim by 6dB and leave the input level trim a 0.

Edit: Typo
Edited by Stereodude - 12/19/12 at 9:46am
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post #1212 of 1592
12/19/12 at 9:28am
Thanks for the info Stereodude. It confirms the reasons I did not like the minidsp personally. I know it did not work well with my gear. The limited voltage range and headroom available are problematic in an EQ device IMO. The lack of correspondence between the gui meters and the actual headroom available is odd. It can be setup to work effectively but takes a lot more work to get the gain structure right than most put in I suspect. Anyway thanks for sharing your findings.
Edited by Ricci - 12/19/12 at 10:30am
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post #1213 of 1592
12/19/12 at 9:49am
How about the 8x8 version, Stereo and Ricci? That version has support on it's output for 8vac. I'm not sure what the DCX is capable of but I do know that you, Josh, like it and I sure do too.
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post #1214 of 1592
12/19/12 at 9:53am
FWIW, my buddy is going to take the same data with his Onkyo that I did for my Pioneer with the same DTS test tones. He's not done, but it looks to have a SW output that's not as hot as my two Pioneer Elite units. From the preliminary data I got it looks to be about half the voltage under the same circumstances. I'll post a comparison when I get all the numbers. The more interesting thing is that the unit is capable of crazy output voltages on the SW output with no clipping. He saw 18.4Vrms / 52Vpp at +18 on the master volume with the SW level trim at 0dB with one of the test tones (no clipping).
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post #1215 of 1592
12/19/12 at 10:10am
Quote:
Originally Posted by Scott Simonian View Post

How about the 8x8 version, Stereo and Ricci? That version has support on it's output for 8vac.
$400 is a little stiff IMHO. I'll admit that the voltage ranges looks better on paper though. A "LFE Edition" Balanced 2x4 unit at the similar price (say a $10-20 premium) with higher IO ranges would be much more interesting to me.

As a point of reference, after setting my SW out on my SC-05 all the way down to -10dB so I wouldn't clip the input of the MiniDSP, adding a 6dB cut in the MiniDSP to allow for the up to 6dB of boost my equalization curves could apply (dependent on frequency) so the output of the MiniDSP wouldn't clip post filters, and setting turning the gain knobs on my Crown XLS Drivecore 2500 all the way up I was not quite able to hit 75dB with the SW calibration test tone. I had to set the SW channel trim up to -9dB. Post calibration testing shows I can clip the Crown's output before getting to reference on the MV so the amp will clip before the MiniDSP, but working around the limited voltage capability of the MiniDSP is a bit of a pain.
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post #1216 of 1592
12/19/12 at 10:14am
i still wonder if this would help. take a look at the specs and see if it might do what you need:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=245-868
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post #1217 of 1592
12/19/12 at 10:24am
Quote:
Originally Posted by Stereodude View Post

$400 is a little stiff IMHO. I'll admit that the voltage ranges looks better on paper though. A "LFE Edition" Balanced 2x4 unit at the similar price (say a $10-20 premium) with higher IO ranges would be much more interesting to me.

Definitely. That would be a great seller, me thinks. I'd like mine not as a lil' box thing though but more like a rack mount version like the 4x10hd series.
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post #1218 of 1592
12/19/12 at 10:33am
Quote:
Originally Posted by brian6751 View Post

i still wonder if this would help. take a look at the specs and see if it might do what you need:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=245-868
Probably, but you could end up needing 2 of them. One before the MiniDSP to cut the voltages down to something it likes and a second one after the MiniDSP so you can get the voltages back up to what your amps need. Also, my understanding is they roll off pretty hard under 20Hz also.
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post #1219 of 1592
12/19/12 at 10:38am
Quote:
Originally Posted by Scott Simonian View Post

How about the 8x8 version, Stereo and Ricci? That version has support on it's output for 8vac. I'm not sure what the DCX is capable of but I do know that you, Josh, like it and I sure do too.

DCX is around 12 volts ( rms) in and out. Both input and output clip at almost exactly the same time. Plus the indicators on the unit and in the software are accurate. Actually the red clip indicator lights up a little bit before actual signal clipping occurs on both the in and out which is the way it should be.
Quote:
Originally Posted by Stereodude View Post

FWIW, my buddy is going to take the same data with his Onkyo that I did for my Pioneer with the same DTS test tones. He's not done, but it looks to have a SW output that's not as hot as my two Pioneer Elite units. From the preliminary data I got it looks to be about half the voltage under the same circumstances. I'll post a comparison when I get all the numbers. The more interesting thing is that the unit is capable of crazy output voltages on the SW output with no clipping. He saw 18.4Vrms / 52Vpp at +18 on the master volume with the SW level trim at 0dB with one of the test tones (no clipping).

I have a very cheap old Pioneer (now in my garage) and it is about 6 or 7 volts out clean.

Yep Onkyo's put out crazy voltage from what I have seen. I never did get mine to clipping because my professional SC input won't handle more than about 13 or 14 volts before clipping the input. I figured at that point it didn't really matter how much more was available so I didn't put any effort into further investigation. That is why it drives me nuts when people say that the Onkyo's need a boost box because they might be capable of more clean voltage than the booster! You just have to set them up to utilize it.

My problems with the minidsp likely stemmed from the GUI readings not being accurate. So in all likelihood it was clipping both the input and output when I thought there was quite a bit of headroom left.
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post #1220 of 1592
12/19/12 at 11:00am
Quote:
Originally Posted by Ricci View Post

DCX is around 12 volts ( rms) in and out. Both input and output clip at almost exactly the same time. Plus the indicators on the unit and in the software are accurate. Actually the red clip indicator lights up a little bit before actual signal clipping occurs on both the in and out which is the way it should be.
I have a very cheap old Pioneer (now in my garage) and it is about 6 or 7 volts out clean.
Yep Onkyo's put out crazy voltage from what I have seen. I never did get mine to clipping because my professional SC input won't handle more than about 13 or 14 volts before clipping the input. I figured at that point it didn't really matter how much more was available so I didn't put any effort into further investigation. That is why it drives me nuts when people say that the Onkyo's need a boost box because they might be capable of more clean voltage than the booster! You just have to set them up to utilize it.
My problems with the minidsp likely stemmed from the GUI readings not being accurate. So in all likelihood it was clipping both the input and output when I thought there was quite a bit of headroom left.

Okay, good to know. I knew it was something high like that but wasn't sure. Sounds like the DCX will work great with the high voltage my Onkyo outputs. That sucker is hot! I think right now I have my 'Sub out' set to -15dB to keep it from clipping my BFD. I'm not even using Audyssey or any boosts!

EDIT: I wonder if I should try using the "pro" input sensitivity mode again on my BFD. I haven't tried using that since back when I first got the LLT's up and had a Harmon Kardon avr.
Edited by Scott Simonian - 12/19/12 at 11:16am
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post #1221 of 1592
12/19/12 at 5:25pm
I have an onkyo PR-SC885 that can go to -15dB on its sub level. If that isn't enough there's a tone adjustment setting that can lower the sub level even more. If that still isn't enough there's a setting that you can adjust the lfe individually for dolby digital, dolby truehd, dts, dtshd-ma to where you can set each one of those sound formats lfe to -10dB, -20dB, and -infinity. I wish this test was done two weeks ago before I bought my balanced minidsp. I might have bought something from behringer but thought that the minidsp was supposed to be better.
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post #1222 of 1592
12/19/12 at 7:36pm
i gotta ask, cuz i dont know and im looking to buy one of these for sub duty. Seems to be a TON of happy MiniDSP customers using these for their subs. Why has no one had issues like this till now?
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post #1223 of 1592
12/19/12 at 8:01pm
Quote:
Originally Posted by brian6751 View Post

Why has no one had issues like this till now?
I guess ignorance is bliss.
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post #1224 of 1592
12/20/12 at 12:42am
This is why I bought the 2x8 version. MiniDSP was/is considering working on a sub box with higher levels if there was request for it, but nobody really cared. I'd mentioned this multiple times before now, guess people are finally catching on.
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post #1225 of 1592
12/20/12 at 4:39am
I should compile my data and post something on their forum. At the very least maybe they can fix the levels reported back in the GUI to be peak amplitude instead of RMS as well as making the reported level dB instead of whatever it is now.
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post #1226 of 1592
12/20/12 at 8:15am
Quote:
Originally Posted by brian6751 View Post

i gotta ask, cuz i dont know and im looking to buy one of these for sub duty. Seems to be a TON of happy MiniDSP customers using these for their subs. Why has no one had issues like this till now?

This isn't a new "issue". They didn't hide the capabilities of their product, and as it turns out, some people had issues with the voltage limitation. However, those voltage limitations work just fine for a vast number of preamps and amps.

Quote:
Originally Posted by Stereodude View Post

I guess ignorance is bliss.

Let's not get carried away...jeepers

Quote:
Originally Posted by Stereodude View Post

I should compile my data and post something on their forum. At the very least maybe they can fix the levels reported back in the GUI to be peak amplitude instead of RMS as well as making the reported level dB instead of whatever it is now.

I think that's a good idea. The more information they have the better.
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post #1227 of 1592
12/20/12 at 8:55am
so i guess ill have to measure my avr output voltage before i buy. thanks for the work and heads up! i definitely think you should report it to MiniDSP. not sure if just blasting it onto their forum is the best way though LOL tongue.gif. maybe a email first? like Luke said, i dont think they are hiding anything but its good info
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post #1228 of 1592
12/20/12 at 9:27am
Quote:
Originally Posted by notnyt View Post

This is why I bought the 2x8 version. MiniDSP was/is considering working on a sub box with higher levels if there was request for it, but nobody really cared. I'd mentioned this multiple times before now, guess people are finally catching on.

Yes, yes. We all can't be as awesome as you.
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post #1229 of 1592
12/20/12 at 2:11pm
My $169 QSC DSP-30 is looking even better now biggrin.gif
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post #1230 of 1592
12/20/12 at 2:13pm
Dont you get around this issue with using amplifiers with higher gain? Audyssey set my main sub at -15 (ive turned it up to -10) and the Oaudio plateamp has its volume knob around 10-11 O´clock...
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