MiniDsp 2X4 HD Boxed Unbalanced 2v 4v jumper

[Invi]

Hi all
Hope that the section is the right one.
Sorry for the stupid question i search the forum and can't understand if it's better or not..
I have denon 3500 h i misured 3.2v on sub out at referece volume. Do i need to set jumper on minidsp 2X4HD (Unbalanced) to 4v? If yes i must take care of something like volume..and or gain on subwoofer/avr subwoofer channel?

I have read that setting the jumper from 2v to 4v introduces 6db of attenuation of the input signal is this correct? What exactly does this mean? sorry but I'm not a signal expert. What can I do to compensate for this loss, can it be done? Could / should I increase the gain of line input of minidsop by 6db? Does this make sense?
Sorry again for the questions but I'm missing out!

It's possbile to have same spl from the subwoofer setting the jumper from 2v to 4v?

My configuration is :
avr sub out 1 -> minidsp 2X4HD input 1 -> 3 subwoofer out.
Thanks.

 

[waudio]

I don't undestand very well what you mean and how exactly are connected your Denon and the minidsp after the minidsp #3 out . Or it goes to you sub amp input? But ...

Default levels from the analog output of most DVD, Blu-ray and CD players are about 2V, in some cases 2.4V.

The reason for the jumpers is to make sure that you don't saturate the minidsp analog inputs into clipping. That would process the signal with distortion through the minidsp to its output/s. So, in your case, if the output from your source (avr sub out 1) is really 3.2V then, yes, put the jumpers in 4V position. If those 3.2V are measured after the minidsp - you don't care (as far as your amp/subwoofer amp can take this signal without distortion).

When you change the jumper the output from the minidsp will become two times more quiet for the same volume control level in minidsp. In that case you may need to increase the minidsp volume by 6db to arrive at the same output level as before.

Another approach is to not change the jumper, but instead decrease the avr sub out 1 signal (if you have control over it), and make sure that it never goes above 2V. Then play with the minidsp volume control to set its output 3 at the level that you wish. There should be enough range to do that. The good thing is that in minidsp app you have VU meters and you can always tell if the signal hits in the red.

Hope that this helps.

 

[Invi]

thank you very much for your reply, it helped me a lot. Sorry for the bad explanation of my configuration, I summarize it briefly. I have
3 sub woofers (2 svs pb1000 (one wirless), one svs pb2000), I connect minidsp input # 1 to my avr sub out # 1, and 3 out analog from minidsp to # 1 pb2000, # 2 to pb1000 (wirless), # 3 other pb1000.
I took some more precise measurements yesterday at various volumes, and what I found is that 2v from the avr sub out are only exceeded in volumes to which I don't listen to music or films. With the sub trim a 0 on avr i have 2v at -5.5db from reference volume (74.5 of 80 on denon) i listen music and films generally at -15, -10 maximum with a trim of sub out on avr at - 6. So I think I will leave the jumper at 2v and set the maximum volume to 74.5 to prevent someone from unintentionally increasing the volume too much.
what do you think about it? Is this a correct reasoning?
Thanks again.

 

[waudio]

I see. Minidsp is used as splitter for the 3 subwoofers. It seems that you're OK with your levels setup. You can always google "gain structure" to understand better how the levels should be set in an audio system.

The general idea is to have sufficient level to feed the next device, but not too high to clip it, or too low to bury signal in the noise floor. Also it's good to have progressive signal increase. Each device should add some gain that is kept to the next, or at least keep the signal at the same level between devices. It's not good practice to add too much gain in device 1 and then in device 2 to attenuate it, then add gain again in device 3 etc... You get the point.
Below is an example how I would try to set gain in a system like yours. Take it as an idea. I don't know all of the parameters of your system!

I would start by checking how much input level your subwoofers plate amps need for max SPL before distortion occurs, or reference as you call it. This might be also given in the specs of the subwoofer.
Anyway, to find this level I would set the plate amps volume control to say 2/3 from max and leave it there. Then I'd make sure that the minidsp is able to supply this level at reasonable gain settings, say -3db for the minidsp analog input and 0db at the analog outputs. On the minidsp VU meters I would check that the signal is reaching in the green and sometimes in the yellow, but never in the red. That will guarantee a decent headroom in minidsp.
Finally the above should define the max AVR sub output level to give me those green/yellow levels in minidsp that would give me those max SPL level from my subs. If it happens that above 2V are required from AVR (I doubt that), I'd use the jumper...
If it happens that the AVR level ends up very low I would maybe drop the subwoofer plate amps volume control to 1/2 from max and start over the same steps until I get reasonable gain settings in all devices. Not too much, not too little. Of course another adjustment is needed to match the subwoofers with the rest of the speakers. I would probably do that from minidsp by changing up or down the minidsp output gain (the one that I left initially at 0db). Or it will be taken care of in the AVR speakers management.
From there just use whatever volume control you use to set level to normally watch movies or listening to music.

 

[Invi]

Yes basically i use minidsp in order to equalize the 3 subwoofers response (Eq, Delay, High pass crossover).
This is a great reply, you give me tons of tips. And next weekend i'll start the process as you describe!

I'll report the result as i finish the process!

Thanks.. Thanks .. Thanks.

 

[Jack1949]

Invi,

Here's a link to an instructional youtube video you might be interested in. I used it last month after purchasing a miniDSP 2x4 HD. I found it very helpful.

REW multiple sub setup with miniDSP 2x4 HD

 

[Invi]

great video outstandig!!!!

Thank you very mutch! Great channel too!!