Which MiniDSP?

Phil

Hi Fella's
I'va question that needs an answer. I wanna do this;

place 3 to 4 subs around the room, thinking of mid point along each wall and I want to EQ each sub, provide both high pass and low pass so the subs see 20hz to say 50Hz or so, then be able to time align each so they behave like a single sub.

Then I will use my HDP-4 DEQX to manage the whole system, where the above subs are a single sub according to deqx.

So what unit will do this? What plug-in is needed?

Make sense?

Thanks.

JohnR

G'day Phil, are you using pro amps for the subs (balanced input) or are the subs self-powered?

If the former then the miniDSP balanced would I think do the trick. With the four-way "plugin" you have a single input and four outputs the independent high pass/lowpass, delay and EQ. (6 parametrics each). The catch is that it doesn't have regular XLR connectors so you have to massacre some cables (or build adapters, or buy the raw board and built it into a box).

If the latter then the single-ended one would work, but check the sensitivity of the sub amps (must be < 0.9V RMS).

In either case you get 7.5 ms of delay on each, which equates to about 2.5 meters. I've always found this to be enough as I just make the delays on everything equal to the physical distance and then use other means to get the response flat. In this case you'll have the DEQX for overall alignment.

Interesting idea, by the way!

PS. I'll add a couple of tags to your post.

Phil

Great, thanks heaps John. Yes pro amps will be used to power the subs - actually one will/could be a powered jobbie (JL F113), but might just stick to the 3 subs that I'm building for the Deqx setup and leave the JL for HT. The subs I'm building include Dayton 18" from Paul, sealed.

So the balanced MiniDSP is the one. Cool, I'll order it now

Great to know the delay limitations of 7.5ms. This will affect where I can place the subs as they must be time aligned with each other before the deqx see's them.

The new forum looks tops BTW.

Cheers
Phil

Phil

Nutha question. What are the plug adaptors I need once I have butchered some XLR cables?

JohnR

Hi Phil, thanks, no worries! Did you order the one in a box? They come with (I think) the plugs that go into the green sockets. I believe they're called Phoenix connectors.

Lemme see... here, this chap did a bit of a write-up:

Easy RCA Inputs and Outputs for a 2x4 Balanced miniDSP

JohnR

PS. You'll also need a power supply, must be 12V DC. Got any old hard drives laying around? Most of those have 12V DC plugpacks.

paulspencer

Some of the iNuke amps have DSP included, haven't checked their delay limits. 7ms might not be enough. In your room I'd probably try that kind of placement first also.

MALfunction

Also check out the Crown XTi 2 series of amps that's what I'll be using with the tapped horns .

http://www.crownaudio.com/xti-2-series.html

Phil

Thanks again. Didn't know about the plugpack but did see when I ordered that the plugs are included. That link is not working. I'll do a web search for the same thing.

Paul, good idea about the iNuke DSP, I did not give that option any thought to be honest, was just looking at the power amp versions only. Not to worry.

MALfunction

Hi Phil

How are you going to connect the mini to the DEQX.

Cheers

Phil

The theory I have in my head is that the deqx will be a 2-way plus subs (mono or stereo), so the low output from the deqx will connect to the input(s) of the minidsp. I'll use an impulse measurement in REW to help me keep it all in time.
I've already done a heap of experimenting with a single sub with the 2-way horns I had and the improvement was solid.

MALfunction

Sounds great .

JohnR

Whoops, fixed link (http://seriousaudioblog.blogspot.com.au/2012/06/easy-rca-inputs-and-outputs-for-2x4.html)

What is the two-way part up top, Phil?

Twodogs

Phil,

have you read the Geddes approach to multi subs. He recommends not having the subs symmetrically placed. (You mentioned "midway along each wall").

Out of interest, could you please let me/us know whether 4 subs is signif better than 3 ? and 3 better than 2 ? I am about to try 2 subs and undoubtedly will wonder "what-if a 3rd"? (where "better" means an even bass response throughout the room).
cheers
Nigel

Phil

The 2-way was a corner loaded 18" and a compression driver in a circular horn. X-over is 350hz between them. Coz the 18" needs to go pretty high, I wanna take the low freq's from it. This system is sold but I will replace with the same in the new year. I have other speakers to keep me occupied.

The subs idea will work with any speaker and is not limited to what I had.

Nigel, I'll start with the 3 subs I'm building and will place each where they measure independently well enough to allow good summed performance. That's gunna take some time. If the mojo remains for me to add the existing sub I have, then I may, but it will probably stay as the HT sub.

Phil

Bugga, forgot to add, I checked that fella's RCA cable work linked above but that seems like a lot of work for negligible benefit. Wont I just cut the plug off a mic cable and screw the +, -, Earth into the phoenix connectors??

JohnR

Hi Phil, yep, sorry, I just meant to illustrate how the connectors work.

You may not need/want to connect the shield, try it both ways.

Phil

Thanks John for all your help.

paulspencer

Nigel,
4 subs is a harman suggestion and i think the put it forward before geddes suggested 3. The harman config puts 4 at midwall locations and it works in large rectangular rooms quite well and is good with multiple rows and many seats as you would have in a fairly large HT. Geddes suggests 3 in typically asymmetrical locations.

I suggest between 1 and 5
Depending on how they measure. In my room, mains with bass plus 1 sub is plenty and more subs don't bring real benefit. In reality, the benefit of multiple subs can be less than people would willingly pay for in many situations.

If someone wants to be lazy and has a situation like the harman test room, then that config will work well.

At my room at the show, I went with a harman config, didn't have much time so I put them at midwall placements and measured. The result was good and I barely had time to even do that properly.