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MiniDSP - Page 47

post #1381 of 2293
Quote:
Originally Posted by DonH50 View Post

^^^ A little more info: The usual caution is not about boosting vs. cutting but about trying to boost a null caused by signal cancellation at the listening position. By doing that you may be overdriving the system (i.e. way too loud when you are outside the null) and simply wasting headroom.

Boost or cut, once you renormalize the gain, the headroom is the same.


Absolutely! Here’s more on trying to boost nulls – should have linked it with my previous post.

Regards,
Wayne A. Pflughaupt



post #1382 of 2293
So it seems in the post quoted there was really no "myth" at all.
post #1383 of 2293

The "myth" is that boosting should never be done. It's been floating around the home theater forums for as long as they've been around.

Regards,
Wayne A. Pflughaupt



post #1384 of 2293
I saw the word "better", still looking for "never"...
post #1385 of 2293
Quote:
Originally Posted by Wayne A. Pflughaupt View Post


The "myth" is that boosting should never be done. It's been floating around the home theater forums for as long as they've been around.

Regards,
Wayne A. Pflughaupt




Whether one should boost depends on the cause of the dip. Some dips cannot be corrected with a reasonable amount of boost while some can depending on the cause.
post #1386 of 2293
OK, I just took a measurement in my room. This is after MultiXT32. My sub is the PBultra 13 in a fairly small room. I have a balanced miniDSP 2x4 with the 2.1 advance plugin. Is it possible to make the valley around 55 a bit better using it? If so what steps should I try? Other than that the curve looks pretty good if I am doing everything right.

post #1387 of 2293
Can you move the sub's position at all?
If so, I would try that. Often it only take a small move.

You can add a little boost in the upper octaves, ala 55 Hz with minimal of damage since that is where the sub will have the most headroom to spare.
Edited by jpmst3 - 2/2/13 at 7:29am
post #1388 of 2293
Do i apply that on the input PEQ or the output? Or does it not matter as long as I bypass one?
post #1389 of 2293
You want to apply the EQ to the output you are using for your sub. That way if you add another down the road you can EQ it differently if necessary.
post #1390 of 2293
I plugged I made the changes, does it save automatically? I went to run my sweep in REW and now the sub is extremely quiet. Do I have to change the gains?
post #1391 of 2293
I am not sure on the details with the saving process. Perhaps someone else can chime in.
post #1392 of 2293
Quote:
Originally Posted by audiovideoholic View Post

I got the mini 10x10 for xmas that will be used for 8 subs that are ran by 2 FP10ks (8 total channels of the amps).

Do I need to split the outputs from my AVR 8 times for the inputs or can I simply use 1 input but seperate outputs for each sub?

One cable from AVR to miniDSP is all that is required. The 10x10 has what's called "matrix routing," which means that any output can feed from any input (or any combination of inputs). Obviously, each amp channel needs its own signal cable from the miniDSP.
post #1393 of 2293
Do you know why my volume would be cut? I cannot get the sub to make any noise anymore. hmmmmm
post #1394 of 2293
No, it has to be something in your setup. Try removing all filters and start over adding one at a time.
post #1395 of 2293
It has to be something with my input voltage, it is measuring -72. That seems really low. If I put my sub trim to +12 I can get the miniDSP input voltage to read -40. Still way to quiet. I reset the miniDSP to factory defaults too.
Edited by Diesel 48 - 2/2/13 at 8:33am
post #1396 of 2293
Quote:
Originally Posted by Scott Simonian View Post

Nice! I plan on using the 10x10hd and doing something similar. smile.gif

You should be able to copy inputs to the additional outputs using the built in matrix.

Thanks Scott
post #1397 of 2293
Quote:
Originally Posted by DS-21 View Post

One cable from AVR to miniDSP is all that is required. The 10x10 has what's called "matrix routing," which means that any output can feed from any input (or any combination of inputs). Obviously, each amp channel needs its own signal cable from the miniDSP.

Thanks!

Hopefully I'll be able to get if working without too much trouble then. Is there an option that I need to turn on for the outputs I assume? Wish there was a printed user manual with it.
post #1398 of 2293
Quote:
Originally Posted by Diesel 48 View Post

It has to be something with my input voltage, it is measuring -72. That seems really low. If I put my sub trim to +12 I can get the miniDSP input voltage to read -40. Still way to quiet. I reset the miniDSP to factory defaults too.

What happens if you eliminate the miniDSP from the mix?
post #1399 of 2293
Quote:
Originally Posted by jpmst3 View Post

What happens if you eliminate the miniDSP from the mix?

As soon as I take the miniDSP out of the chain my sub levels are normal again. My SPL meter reads roughly 70db. With the miniDSP hooked up it is nothing. The only way I could get the levels going to the miniDSP high enough were to go to levels, turn my receiver to +16db and then max out the subwoofer trim to +12. That would give the amp on the sub enough signal where I could crank the amp and hit 70db on my SPL meter. It seems like the miniDSP should not be cutting the signal that much.
post #1400 of 2293
Is there a gain on the input side of the miniDSP as well?

If not, you may need an Art Clean Box or some other type of booster gear.

You definitely don't want to run any component in the chain at full gain, especially the receiver. Full gain usually introduces more THD.
post #1401 of 2293
Quote:
Originally Posted by jpmst3 View Post

Is there a gain on the input side of the miniDSP as well?

If not, you may need an Art Clean Box or some other type of booster gear.

You definitely don't want to run any component in the chain at full gain, especially the receiver. Full gain usually introduces more THD.

The only thing you can do on the miniDSP is cut the gain, not boost it.
post #1402 of 2293
Quote:
Originally Posted by Diesel 48 View Post

The only thing you can do on the miniDSP is cut the gain, not boost it.


Ahhh, well then I would imagine he has no choice but to boost the signal externally.
I was under the impression that the balanced version had more signal strength.
post #1403 of 2293
Quote:
Originally Posted by jpmst3 View Post

Ahhh, well then I would imagine he has no choice but to boost the signal externally.
I was under the impression that the balanced version had more signal strength.

I am currently using the RCA out from my receiver. Maybe I should pick up an XLR cable and try the balanced output. Maybe that will give me the voltage I need.
post #1404 of 2293
Quote:
Originally Posted by audiovideoholic View Post

Quote:
Originally Posted by DS-21 View Post

One cable from AVR to miniDSP is all that is required. The 10x10 has what's called "matrix routing," which means that any output can feed from any input (or any combination of inputs). Obviously, each amp channel needs its own signal cable from the miniDSP.

Thanks!

Hopefully I'll be able to get if working without too much trouble then. Is there an option that I need to turn on for the outputs I assume? Wish there was a printed user manual with it.

The matrix screen in the software is pretty intuitive. Just click on the outputs you want to feed from a given input.
post #1405 of 2293
minidsp masters, this came up in the Rythmik subwoofers thread and I wanted to ask here.
Quote:
Originally Posted by dstew100 View Post

Quote:
Originally Posted by DonH50 View Post

On the miniDSP: There is a dedicated thread in the DIY Forum on the miniDSP. One of my concerns using it vs. something like Audyssey for full-range control is that my understanding is that it easily implements standard filters to adjust the amplitude over frequency, but I am not sure how flexible it is when it comes to phase/group delay. For example, if you have a three-driver speaker (woofer/mid/tweeter) plus sub, one of the desirable outcomes is that everything is time-aligned. Frequency-domain tools do not usually make that easy...

Yeah I need to get to toying with mine to figure that stuff out but it is a concern I have as well. Audyssey and Antimode both claim time domain. Minidsp can add delays, but not sure if they are flexible enough for what we are talking about. I'm interested in understanding this more. So lets say I add a filter to attenuate by 3db maybe 5hz wide gradual slope. I don't really understand what that does to phase and how wide across the spectrum it impacts the phase/timing. Maybe we should head over there? I'm familiar with the thread you are referring to. HTS and the minidsp website have minidsp specific forums too.


How does the minidsp impact time alignment and phase? I really don't understand how EQ filters impact phase, any reading you all recommend?
post #1406 of 2293
Quote:
Originally Posted by dstew100 View Post

How does the minidsp impact time alignment and phase? I really don't understand how EQ filters impact phase, any reading you all recommend?

One good read on the subject of how EQ affects system phase response can be found in the Minimum Phase section of the REW manual.

I couldn't quite tell what DonH50 was specifically referring to, but it looks like he was talking about the use of the miniDSP as an active crossover for a fully active loudspeaker. In that application, a difference in distance from each driver to the listener can be compensated by adding the appropriate delay to the driver or drivers closest to the listener. This might be useful in the case of a flush-mounted tweeter and a woofer whose effective acoustic center is somewhat behind the baffle because of the cone shape.

It sounds like what you're interested in though is an EQ application, is that right? If so, the information I linked above should help.
Edited by rock_bottom - 2/4/13 at 12:08pm
post #1407 of 2293
Quote:
Originally Posted by rock_bottom View Post

Quote:
Originally Posted by dstew100 View Post

How does the minidsp impact time alignment and phase? I really don't understand how EQ filters impact phase, any reading you all recommend?

One good read on the subject of how EQ affects system phase response can be found in the Minimum Phase section of the REW manual.

I couldn't quite tell what DonH50 was specifically referring to, but it looks like he was talking about the use of the miniDSP as an active crossover for a fully active loudspeaker. In that application, a difference in distance from each driver to the listener can be compensated by adding the appropriate delay to the driver or drivers closest to the listener. This might be useful in the case of a flush-mounted tweeter and a woofer whose effective acoustic center is somewhat behind the baffle because of the cone shape.

It sounds like what you're interested in though is an EQ application, is that right? If so, the information I linked above should help.

Thanks for the link. Yeah I believe you are correct that Don is more interested in full range / active crossovers but we'll let him chime in. I will just be EQ'ing my subs so not sure how concerned I should be with how minidsp filters (or PEQ filters in general) are hurting me (if at all), and if they are how do I make the situation better.

He's point about frequency vs time domain is interesting though. Audyssey and Antimode both claim time domain corrections. Is that possible with minidsp? I'm aware of the time delay, but is one overall time delay per channel really what is needed to compensate? I probably don't understand enough at this point to even ask the right questions, I'll read that link you provided.
post #1408 of 2293
Quote:
Originally Posted by dstew100 View Post

He's point about frequency vs time domain is interesting though. Audyssey and Antimode both claim time domain corrections. Is that possible with minidsp? I'm aware of the time delay, but is one overall time delay per channel really what is needed to compensate? I probably don't understand enough at this point to even ask the right questions, I'll read that link you provided.

That ends up being a somewhat complex question which I'll split into two.

First, there's the question of whether fixing up, say, a response peak with EQ will fix up the phase as well (which would also fix up the time domain quirks caused by that peak). The answer is that if e.g. the peak is in a minimum-phase region of the response, and the EQ is minimum-phase, flattening the response will indeed fix up the phase in the frequency region over which the EQ acts, which in turn will fix up (only) the time domain quirks caused by that specific peak (which you might verify with a waterfall plot). The filters in the miniDSP are of the minimum-phase type. The link shows how to determine whether the response region you're trying to EQ is minimum-phase or not.

The other issue is that most speakers, when considered over their full bandwidth, are not minimum-phase. This behavior causes time domain quirks in such speakers. Fixing up these kinds of quirks is done by so-called delay equalizers. The miniDSP does not do this. Not sure if Audyssey does, and I'm only aware of one audio product (by Thuneau) that actually does this, though there may be many more.
post #1409 of 2293
Quote:
Originally Posted by dstew100 View Post

How does the minidsp impact time alignment and phase? I really don't understand how EQ filters impact phase, any reading you all recommend?
I don't (yet) have a miniDSP, but I understand how their filters work.

It sounds to me as Don is referring to the fact that IIR (Infinite-Impulse-Response) filters have a non-linear phase response. In other words, different frequencies are delayed by different amounts of time. FIR (Finite-Impulse-Response) filters, on the other hand, can have a linear phase response: a constant delay for all frequencies. This constant delay, called "group delay", is equal to the time between each sample, multiplied by half the size of the filter. This means that, if you use the same size FIR filter for each channel, everything comes out at the same relative phase as it went in, although delayed by the group-delay.

The biquad filters used by the miniDSP are a specific form of IIR filter, and therefore they will suffer from unequal delays for different frequencies. But the phase-shift is small, and some say its of no consequence (I cannot speak to that issue - I just don't know). It can also be mitigated somewhat, and a Linkwitz–Riley crossover is an excellent example of how to repair the phase delay.

Note that the time-domain adjustments in Audyssey or the miniDSP might not be useful unless they can be made to effect the delay with the inverse relationship to frequency as the FIR filter's effect.
Edited by MarkHotchkiss - 2/4/13 at 1:11pm
post #1410 of 2293
Quote:
Originally Posted by MarkHotchkiss View Post

Quote:
Originally Posted by dstew100 View Post

How does the minidsp impact time alignment and phase? I really don't understand how EQ filters impact phase, any reading you all recommend?
I don't (yet) have a miniDSP, but I understand how their filters work.

It sounds to me as Don is referring to the fact that IIR (Infinite-Impulse-Response) filters have a non-linear phase response. In other words, different frequencies are delayed by different amounts of time. FIR (Finite-Impulse-Response) filters, on the other hand, can have a linear phase response: a constant delay for all frequencies. This constant delay, called "group delay", is equal to the time between each sample, multiplied by half the size of the filter. This means that, if you use the same size FIR filter for each channel, everything comes out at the same relative phase as it went in, although delayed by the group-delay.

The biquad filters used by the miniDSP are a specific form of IIR filter, and therefore they will suffer from unequal delays for different frequencies. But the phase-shift is small, and some say its of no consequence (I cannot speak to that issue - I just don't know). It can also be mitigated somewhat, and a Linkwitz–Riley crossover is an excellent example of how to repair the phase delay.

Note that the time-domain adjustments in Audyssey or the miniDSP might not be useful unless they can be made to effect the delay with the inverse relationship to frequency as the FIR filter's effect.

Thanks for your time and help. I have some learning to do but this is helping me figure out what I need to figure out.

One note for those that were discussing over in the other thread, the auto EQ REW can send to a minidsp uses the biquad filters so as stated above, there is an impact but may be minimal enough to be inaudible.
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