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Discussion Starter · #1 ·
Normally if you want to hear an active crossover, you have to buy it and set it up in your system and you probably won't get the chance to compare. Well, a chance came up to get together with some others and do some comparisons. Thought you guys might be interested in the results.


We compared

Behringer Ultradrive DCX

Behringer Ultradrive DCX with the Pilgrim audio mods

MiniDSP

DEQX


We did two tests:

1. digital conversions

2. digital active crossovers


We used an instant switching level match box that switches both inputs and outputs. For the first test, we let the units simply act as digital converters of an analogue input - ADC then DAC. We compared to a loop through wire.


For the second, we set up with the same settings and measured to ensure we were comparing level matched and with the filters doing the same thing. It's quite time consuming to set up an event like this, so it was not the last word on perfect accuracy. We did not match to within 0.1 db but we took a decent stab at matching.


We didn't do the test blind. While this may disappoint some, but I felt that using instant switching would be revealing enough. We did this test for our own curiosity, but no one had a point to prove. In a previous informal comparison, I found that was enough even with levels obviously not matched. No one in that test could hear a difference with the digital conversions vs a loop through wire, not even one person there who was certain a difference would be heard.


Our extended tests did show differences, but I'd call them subtle. At certain times, I noticed a difference in imaging where there was a small shift. The instant switch during a sustained note is quite revealing. MiniDSP appeared to have increased treble detail compared to DCX, despite mreasurements showing that it rolls off more above 20k. The measurements from what I recall didn't seem to reveal why that might be the case.


The full write up is here in my blog:
http://redspade-audio.blogspot.com/2...ing-tests.html

and there are more comments in the linked SNA thread.


My findings if I can sum it up in a nutshell?

MiniDSP is the first one you want to try out of these.


DEQX sadly didn't quite get a fair trial, we had time limits and something wasn't quite right.
 

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Paul, thanks for posting here. I have been trying to decide which way to go, and to me, opinions like these are helpful.
 

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Discussion Starter · #3 ·
I'm glad you found it helpful. I have quite a few pages now about active crossovers (digital) on the blog. There are many good choices now.
 

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I'm really considering active for my next build...it sure would make the whole process much easier. And that MiniDSP is making it a lot more affordable
. Now I just need to figure out a reasonable amplifier solution and I'll be ready to rock.
 

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Paul, thanks for posting and confirming my opinion about the MiniDSP.


I own both the DCX and MniDSP. I will be using the DCX for prototype/testing in the future, it still has great value just for doing that.


Now if someone could build a web app to generate all transfer function/bi quad values so we can just plug and play on the miniDSP. Ie....we need to know how to create a 96dB slope
 

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Quote:
Originally Posted by Starkiller4299 /forum/post/19639495


I'm really considering active for my next build...it sure would make the whole process much easier. And that MiniDSP is making it a lot more affordable
. Now I just need to figure out a reasonable amplifier solution and I'll be ready to rock.

FWIW, I just received my AS100.2 plate amps with full DSPs. I didnt realize how small they are, 7"x4" very cool little two channel amps with DSP in them. They were going for $250 Each but that was a limited sale on www.diycable.com
 

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Quote:
Originally Posted by Starkiller4299 /forum/post/19639495


I'm really considering active for my next build...it sure would make the whole process much easier. And that MiniDSP is making it a lot more affordable
. Now I just need to figure out a reasonable amplifier solution and I'll be ready to rock.

You might consider Emotiva multi channel amps. People who are a lot more discerning than I am have chosen them for active crossover applications and been satisfied. Two examples below.

http://www.avsforum.com/avs-vb/showthread.php?t=1213427

http://advanceddefinition.com/The%20Octagon.htm


I have used XPA-1 and XPA-2 and have been satisfied. a UPA-7 or XPA-7 will likely be my choice as a development/test amp.
 

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Yeah, I've definitely seen it around. But $600 (on sale) for amps does kinda break the budget
. Seriously, no reason for a decent multichannel amp to cost so much when you can get a fully featured multi-channel receiver for a fraction of the cost. Will I ever ask more than 75W/cannel? No, I most likely wont
.
 

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Quote:
Originally Posted by Starkiller4299 /forum/post/19639669


Yeah, I've definitely seen it around. But $600 (on sale) for amps does kinda break the budget
. Seriously, no reason for a decent multichannel amp to cost so much when you can get a fully featured multi-channel receiver for a fraction of the cost. Will I ever ask more than 75W/cannel? No, I most likely wont
.

I think the difference will be the robustness of the design; the ability to provide high current basically flat response 20Hz to 20kHz (and near flat above and below that) at rated power all channels driven with good damping, a high slew rate, a low noise floor, no active cooling (fan), with decent aesthetics.


With efficient speakers (say 95 dB 1w/m) and an active crossover, you are right, you will not need a lot of power. In fact, if your multichannel receiver has line level inputs for each channel (many do), you could use it as your multichannel amp.


Another inexpensive suggestion is something like this

http://www.amazon.com/AudioSource-AM...p_ob_e_image_0


one for each two-way speaker. I have owned these too and been satisfied. Similar Audio Source designs have reviewed well.
 

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Quote:
Originally Posted by Starkiller4299 /forum/post/19639669


Yeah, I've definitely seen it around. But $600 (on sale) for amps does kinda break the budget
. Seriously, no reason for a decent multichannel amp to cost so much when you can get a fully featured multi-channel receiver for a fraction of the cost. Will I ever ask more than 75W/cannel? No, I most likely wont
.

I think using an AVR with multi-ch inputs is a great idea. You can get 7 channels for easily under $200.


I have my favorite Panisonic XR55 used that way. Too bad they are hard to find



The Denon 3805 here
http://www.avsforum.com/avs-vb/vbcla...do=ad&id=14794


is $240....one heck of an amp with gain structures for that price IMO.
 

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Discussion Starter · #12 ·
Even in Australia where there is a fair shipping cost, the Emotiva amps are impressive value and people around here are starting to take notice and buy them. BTW, it's surprising how much power you can actually use even in an active setup. I was watching a movie recently which was pretty dynamic, and the levels of my mid amp went crazy and put me on edge (I like lots of headroom). The amp was a Behringer A500 with 160w or so into the load of a 6.5" vifa c17 midbass. Not very efficient but I was surprised to see how much power was being used.


Class D modules are an option to consider - they are becoming very cheap.


penngray,

I'll be looking for a solution with the biquads as well. It's definitely an appealing option to be able to create custom filters. Another thing I like about MiniDSP is the flexibility and ease of upgrading. You could run a digital input in and then add on an external DAC if you wanted to get fussy. Only light duty diy would be required. That makes it work for those of us who don't get too heavily into diy electronics.
 

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A fair point on power consumption, Paul, but I'm planning on some fairly efficient (ie, ~95dB/[email protected]), so I think the time's I'll exceed 1 watt, much less 10 or 100, will be rare
.


Dangit Penn--my wallet is till recovering from my subs, and you go and tempt me like that! I wonder if I could also use that one as an optical switch? That would seal the deal for me
.
 

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Quote:
Originally Posted by Starkiller4299 /forum/post/19640583


A fair point on power consumption, Paul, but I'm planning on some fairly efficient (ie, ~95dB/[email protected]), so I think the time's I'll exceed 1 watt, much less 10 or 100, will be rare
.

I think Paul has a valid point. I used this example in an earlier post:


"Since sound pressure falls off pretty rapidly, the further away from the speakers people sit, the greater the issue speaker sensitivity versus amplifier power becomes (each time the distance is doubled, the sound pressure level, or SPL drops by 6dB, 3 dB is a noticeable change in volume to most people, 10 dB is twice as loud, each 3 dB increase in SPL requires 2 times as much amplifier power). Using the speaker sensitivity mentioned above as an example: With 90 dB at 1m with one watt sensitivity, at about 12 feet that becomes about 81 dB which is about half as loud, to achieve a 99 db peak in a movie at 12 feet (a reasonable seating distance) would require 81 dB + 3 + 3 + 3 + 3 + 3 + 3 = 99 dB or 1 + 2 + 4 + 16 + 32 + 64 watts"


95 dB sensitivity at 1w/m with 64 watts would give you a 104 db peak at 12 feet .


Or you can put it this way, if the movie is playing at 86 dB on your 95 dB at 1w/m speakers, with about 75 watts, you have about 18 db headroom which is an explosion that is not quite 4 times as loud as the dialogue (eg people yelling right before the explosion). As it turns out, this is darn close to THX reference (from the THX website; THX Certified Receivers reproduce studio Reference Level, 85dB SPL with 20dB of headroom), which is why sensitive speakers are such a great deal.
 

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I have it a little better, even--I'm barely 2 meters away
. Tack another 6 dB onto that headroom, and with 24dB I'm pretty happy with that
.


Looking at it from the other angle though, doulbling the amplifier power to 150W, and from there to 300W, only nets +3/+6dB. So if your speakers aren't very efficient, you can draw quite a bit of power to get where you want to be--just as Paul stated
.
 

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Quote:
Originally Posted by Starkiller4299 /forum/post/19640740


I have it a little better, even--I'm barely 2 meters away
. Tack another 6 dB onto that headroom, and with 24dB I'm pretty happy with that
.


Looking at it from the other angle though, doulbling the amplifier power to 150W, and from there to 300W, only nets +3/+6dB. So if your speakers aren't very efficient, you can draw quite a bit of power to get where you want to be--just as Paul stated
.

So true. I wondered why SVS recently "upgraded" the 750 w to 1000 w amp in their 13 ultra series; I seemed to me such small change in power would have little discernible effect on output.
 

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So what happened with the DEQX?


where you able to figure out what went wrong?



Matt
 

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Discussion Starter · #18 ·
DEQX? On the first day they were all incompatible with the valve pre and the DEQX had a different response which we didn't have time to sort out - the difference we heard was the difference in response. On the second day we noticed it even more, there was HF roll off even when we tried to just run it for digital conversions with no xo duties. I wondered if it had some setting that needed to be defeated. We had so much to do on the day that we just let it go. It was a shame because it would have been a great to just judge the SQ between a $6k and $100 crossover! I don't just assume that the expensive unit be better in terms of SQ - you don't know til you try.


About power and headroom. With dynamic passages, it's amazing the power you can eat up. On that particular movie at my normal level (not crazy), I was probably seeing 80 - 160w on peaks and I like to see a few lights not coming up for headroom. The difference between 80 and 160w is tiny on a transient peak. In fact even vs 20w there's not much in it. The raw sensitivity of the driver is about 87 db, so with 95 db you have 8db. So in that situation, with the same volume where I got close to clipping and got edgy about it, you would have had the headroom and been sitting at more like 20w. If you turned it up more because the sound is cleaner, then you might have started running out of all the headroom too!


Normally I only see about 1 - 20w going to the mids. This was one horror movie that had a lot of dynamics. So it was a bit of an outlier. In a fullrange system, I'd use twice the power.


I heard some JTR triple 12s with a 100w receiver and they filled a big room with sound which was louder than you hear at a cinema, more like rock concert levels. Pretty impressive.


I'll be going for efficient speakers next, at some point I'd like to try TD15M and WG/CD. And some kind of monster under floor sub.
 

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Never heard the JTR 12s but I heard the JTR 8s a couple of years ago and they are the speakers that made my conclusions about dynamics clear.


Definitely too bad you didnt get the DEQX running, its my next step up and if the MiniDSP didnt come out I would have been sourcing a used DEQX.


The DEQX has all that phase alignment functionality in it which should make it superior to the MiniDSP. Someone did tell me that I should look at a Trinnov auto EQ solution that has phase alignment and try it with the MiniDSP. I have not researched that more but Im hoping its true.
 

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Discussion Starter · #20 ·
I haven't heard of Trinnov but will look into it. Thuneau Allocator is worth looking at as well, although it's not as cheap as you might first think if you get a serious sound card and it does require a PC.
 
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