MiniDSP - Page 44

So how would I accomplish this? I have an rca-xlr adaptor from my Denon and an Xlr-phoenix adapter to the balanced minidsp. Besides ensuring the jumper is set to 2v, how do I get unbalanced input for max voltage out?

You already have an unbalanced input. The - and S are connected in the RCA to XLR adapter.

Oh, didn't realize that. So how would one have a balanced input from a receiver? I guess I figured with the adapters it would equal a balanced chain.

You can't. Some pre-pros have XLR outputs that are truly balanced. However it's been reported that even some of the gear with XLR outputs aren't truly balanced (differential +/- referenced to ground ).

If I understand it correctly, wouldn't most people using the balanced version be ok? If the recommendation is to set it to 2v (default) and have unbalanced in, balanced out, and most use some form of rca-xlr adapter in, wouldn't they get the benefit of the higher voltage out?

I suppose that depends what you mean by okay. The balanced version is definitely better suited for driving pro amps because it has more voltage output than the unbalanced model (when the balanced / XLR output is used). However the MiniDSP still could act as a restriction in the LFE signal chain and clip the signals if you overload the input (which is definitely possible).
I'm not sure there's any advantage to using a balanced input from a voltage standpoint. I haven't tested it. I have a true balanced source I could use for testing, but I'm not real motivated since I don't have any way to get a true balanced LFE out in my surround system. There definitely is an advantage to the balanced output though.

Understood. I think I'm good with my setup. I get good, clean output and only see clip lights on some torture scenes (TIH sonic cannons, for example) if I'm running my sub levels hot. Appreciate all the info. Good stuff.

I'm trying to resolve some information. RCA out of my Onkyo to mini. Balanced out of mini to balanced input of inuke 6000. I haven't measured it, but from what I gather, the 805 will output as much as 7+ vrms from the sub pre out before clipping the output.

When I first hooked this up, I used the 2 volt jumper. With mains calibrated near zero in the Onkyo I needed to boost the sub trim to near its max of +12, and the gain on the iNuke had to be at ~75% (I was trying to avoid maxing it out anywhere).

After switching to the .9 volt jumper I am calibrating with the sub trim around +3 to +5, with the amp gain right at 50%.

As I understand it, doing this means it takes 1.8 Vrms signal input to the minidsp to attain the same max output of 2 Vrms to the amp.

Furthermore, I read that the iNuke needs .71 Vrms into 4 ohms to clip the output with max gain (source: fourth post of this page).

With such a high output possibility of the Onkyo, this setting surely increases the liklihood of clipping the minidsp inputs, right?

I'd appreciate input on how to approach any semblance of unity gain with this setup. I can probably get my hands on a true RMS meter if necessary. But with the wisdom floating around this forum and thread, maybe someone can point me right into the light.

Probably, but how loudly are you listening? Can you drive your Behringer into clipping?

At this point I see the first light on the iNuke light up frequently, the second light occasionally, the third and the 4th (the red one) not at all. But I've not tried to overdo it.

Typically I listen to movies at -20 to -15 (a the high end). Music, depending on how hot it is, as loud as zero, but most commonly in the -10 to -20 range. The highest levels being brief, usually.

When using biquad filters set by REW, using the 10x10 plug in, does that adjust phase at all? Or are you just limited to the normal or invert phase options?

Pretty much any filter will affect the overall phase response in the region of the filter. So, say you're boosting 60Hz, the filter that boosts 60Hz will change the phase around 60Hz also. Not sure if this answers your question though.

I think so. i was just experimenting and didn't know if REW considers phase when it makes the biquads. I just remember when I has an sms-1, I was able to change the phase to any degree and see the results. I guess, I need to know if when REW sets the biquad filters, if there is more I need to do as far as the mini dsp after entering them. I have two subs in different locations, which is why I am concerned about phase adjusment

HI Keager, To add to Stereodude's response:

A biquad filter will affect the phase of its output, and in a non-linear way, meaning a filter that boosts around 60 Hz would likely have a different phase-shift for 55 Hz than for 65 Hz. However, the delay might be too small to be of concern. You would need a plot of the filter's phase-response to know if it's an issue for you.

Only FIR filters with symmetrical coefficients have a fixed delay, referred to as "group-delay", and that delay is related to the length of the filter.
Edited by MarkHotchkiss - 1/1/13 at 7:10pm

ok, thanks. I think I will just take measurements and post them to get advice if I need to mess with it any deeper or not.

Can the Minidsp be used as an active crossover? I do not currently have any EQ devices in my ht, and am considering purchasing a Minidsp for EQ'ing my subs and my LCR's and surrounds. How hard is it to get everything EQ'd? Do I just plug the Minidsp up to my computer, run some sweeps with REW then let those measurements make the proper settings in the Minidsp? Does the manual describe how to properly set the filters? If not, how do I go about adjusting the filters to EQ the LCR's and surrounds flat?

active xo yes, not hard u can do it manually or let rew do it for you, yes just plug it in buy and d/l the plugin u plan to use its very simple. its all very simple. go read the manual before u buy it.

I did some more experimenting last night. I played a 0 dbfs 36hz sine wave with the jumper at the .9 volt setting. Amp gain at half, sub trim +3 or so. Unfortunately I didn't notice the volume level, but it was clipping pretty quickly. Probably around -15 or -10 on the master volume. I figured it had to be the minidsp clipping the input, particularly with that jumper setting.

I switched to the 2volt jumper and tried again. With the same gain/trim settings I could hear it start to clip right at -7 on the master volume. To be certain it was the mini, I backed the volume off and increased the sub amp's gain. PLENTY of headroom there - all clean.

Next I turned off the sub amp, and plugged the computer into the minidsp. The input meters on the mini's display were reading -5 or -4 at the early clipping point determined above. This is less scientific but nonetheless confirms the report by Stereodude. The gui meters are not to be trusted and an Onkyo receiver has no problem clipping the inputs.

It would seem that leaving the amp gain at full tilt would be the safest way to ensure I keep the signal going into the minidsp at a safe level. Are there any drawbacks I'm overlooking?
Edited by baniels - 1/2/13 at 8:41am

none at all, if anything having your receiver output as low as possible will reduce distortion.

Yes, but what you're describing is not an active crossover. That's just a full range EQ. The MiniDSP can do it, but keep in mind it only works if you have outboard amplification and are not using the amplifiers in your receiver for the channels you want to EQ.

Thanks for the reply, and yes, I am aware of the differences between active crossovers and EQ'ing, so perhaps I did not make myself clear. What I am trying to figure out, is can the Minidsp be used in a 7.2 channel configuration, and EQ all 8 of those speakers? Are there any downsides to using a Minidsp for this purpose? What is gained by using a more expensive EQ devise, such as the QSC Dsp-30?


The next set of questions that I have are totally separate from the above.

1.s the Minidsp capable of being used as an effective active crossover?

2 If I build a trio of 3 way towers for my theater, can a single Minidsp be used to actively crossover the entire 9 drivers in my 3-way LCR's?

3. How hard would it be to set everything up correctly if I used a Minidsp to actively crossover my, soon to be built, 3-way LCR's?

4. Is the Minidsp a good choice for this?

5. Is there anything to be gained by using a better quality devise, and if so, what would you recommend?

Any help you could possibly give would be greatly appreciated!

Yes, the 8x8 (10x10) MiniDSP can do that if you have external amplifiers for all 7 channels.
Well, the MiniDSP has a pretty wicked turn off thump so you would want to either leave it on all the time, or shut it off after your power amps / subwoofers are turned off. The more expensive products are generally from more established companies. Most competing products (that I'm aware of) can't take bi-quad coefficients directly. That's a plus for the MiniDSP (assuming you want to use them).

Yes
Yes, but not a single 2x4 model. You would need 3 in and 9 out. That product doesn't exist. Even the 4x10, 8x8, and 10x10 won't work (because the x10 ones only have 8 unique analog output channels). Three separate 2x4 units would work. Also keep in mind you would need 9 channels of amplification.
I'm not sure since I haven't done it, but you will need a calibrated microphone and a knowledge of how to use it and how to interpret the measurements to set up the MiniDSP.
Seems like it.
Not sure on this one.

Edit: correcting mistake
Edited by Stereodude - 1/3/13 at 12:30pm

You can use the MiniDSP effectively as an active crossover. You will probably need to use multiple units to cover the number of inputs and outputs... For a single 3-way speaker you would need 3 channels of amplification and one MiniDSP 2x4 with one of the "Advanced" plugins. Just keep adding that up for the number of speakers you have. If you switch to a 2-way design (or use a hybrid approach, passively crossing your tweeter and mid, and actively crossing the tweeter/mid combo and the woofer), you could use one MiniDSP 2x4 and 4 channels of amplification for two speakers.

The approach to creating the crossover is largely the same as making any crossover (IE, complicated and nuanced), but as long as you have the ability to make calibrated nearfield measurements of your drivers (using a MiniDSP UMIK-1 and REW or HolmImpulse), you can use Charlie Laub's excellent Active Crossover Designer spreadsheets (http://audio.claub.net/software/ACD/ACD.html). They are a bit tricky to setup, so go through the full setup instructions and tutorial example FIRST. The spreadsheet will then help you model various active crossovers for up to 4-way speakers, and then lets you export the Biquad ("advanced") filters directly to the MiniDSP. It will still take a lot of experimentation, but at least you can just keep loading new filters and listening, without buying new capacitors.

-Sam

What would be the advantage, if any, of using a DSP if one is currently utilizing an SMS1. Deciding if I need to pick this up for my current build.

anyone know of a tutorial for splicing rca's into the pheonix connectors? im assuming i could use the rca input's on my ep4000's and not have to buy xlr cables.

What I did was just use some cheap rca cables that I had lying around. The type that you get for free from a dvd player or what not. When I cut mine in half there was an outer wire (the ground/negative) which was wrapped/covering the inside (positive) cable that was covered in plastic so that it wouldn't short/touch the negative wire. If you have wire strippers it can easily be stripped done but could also be stripped, carefully, with a razor blade.

This was the orginal guide that I used:

http://seriousaudioblog.blogspot.com/2012/06/easy-rca-inputs-and-outputs-for-2x4.html#!/2012/06/easy-rca-inputs-and-outputs-for-2x4.html

but you don't need to buy any special twisted wire rca's to get it to work and would be a little more of a challenge to determine which one is the positive and negative wire. Just cut a cheap rca in half and strip back some of the covering to explore what you've got. I can't see other rca cables being much different than what I initially described.

Here you go Brian..

awesome thanks. is that supposed to be the input on the top and output on the bottom?

Sorry for the confusion, bottom is if you are using balanced input and top is for unbalanced.

This is not the best idea if you have a balanced MiniDSP. The balanced MiniDSP in balanced operation has 2x the voltage output as it does in single ended (unbalanced) operation. This means you get an extra ~6dB of signal via balanced.