# First Impression DSP, miniDSP



## broncosaurs (May 31, 2013)

First impressions of using a DSP/Xover in a multi-amp setup. I got a MiniDSP 2x8 running the 4x10 plug-in. The amp is a Emotiva UPA-700, 7 ch @ 80 w/ch on sale BTW for $429. I am going to be using this system to run BG neo3, neo10, and TBD 6-8” bass. I loaded the driver and program from miniDSP into a small Asus 10 mini computer with no problem. Then upgraded the firmware on the DSP board, again no problem. To get familiar with the board programing I first hooked up some outdoor rock speakers to two channels of the amp, amp hooked to two channels of the 2x8. I didn’t want to blow out expensive speakers while I am in learning mode. Worked with the x-over properties using one speaker as the high and one as the low. This worked like a charm. I am amazed how easy it is to change the slopes, and frequency. I then did a second setup using each speaker full range. Using REW and a UMIC from MiniDSP (I am also new to REW) I proceeded to flatten out the response of one speaker. Using all five EQs I ended up with an OK, +- 6 db response. Not bad with a $20 plastic speaker. I then did an A-B comparison between the two speakers. Made sure both speaker levels were the same using the REW. Wow, what a difference. The equalized speaker was so much clearer and more detailed. Kind of funny to say that about a $20 rock speaker! 

I then moved on to some 2 way speakers I built years ago. They started as a “MorPee” or “PeeCreek”, any who, these speakers have a usher 9950 tweet and a 6” Peerless 850122 tuned to just under 50hz. I pulled the x-over out of one speaker and ran wires thru the port to the tweet and bass. Again I used REW to flatten out each speaker’s response. This time using REW’s auto EQ to derive a set of biquads for each the tweet and bass driver. I had a little problem getting the 2x8 to accept the biquads but did finely get them in. X-over set to 2k hz 48db. It was so nice to sit in a chair with my laptop in my lap turning on one driver, other driver off run a sweep, turn other driver on and first driver off , run seep and never get up to switch a cable, SWEET. I then did a side by side with the speaker with the passive x-over to the active speaker using the miniDSP. Again the difference was nothing short of amazing. I took the other speaker’s x-over out to run both speakers as an active system. I guess I need another DSP and amp for these speakers because I won’t be putting back in the passive x-overs.

Using a DSP to R&D speaker design cannot be beat, tweaking x-over, muting a speaker, muting a driver, changing eq, change delay, fix balance and play music, tweaking some more doing it all without changing one wire sitting in the listening position! Even if the design is going to be a passive x-over I would start with a DSP. As for the sound quality of the DSP, time will tell as I get into better drivers/speakers combinations. 
I also have to write up a thread about the first time with REW. What a nice program. Please, if you use REW send in a donation. (yes I am going to also)

Brad


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## Owen Bartley (Oct 18, 2006)

Thanks for the explanation and your impressions, Brad. I don't have any experience with crossover design and it always seemed too complex and painful. But it seems like the miniDSP takes most of the pain out of the equation and makes it a lot more fun.


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## AudiocRaver (Jun 6, 2012)

Great feedback on an ambitious project!

As much as we may love our speakers, they are still usually the weak link in delivering audio, and changing from passive to active crossover can be a good way to clean them up in many cases. Sure sounds like you went about it the right way. Smart move experimenting on throwaway drivers. Keep us updated.


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## broncosaurs (May 31, 2013)

OK, an update. I did manage to blow out two Usher tweeters:crying:. Anyone have any 9950s they want to sell? Not really my fault. Sometimes when the Minidsp is powered off, unplugged, it outputs a very loud pop. Yes I know I should turn the amp off first but sometimes that wont happen, ie power failure. I am working with the minidsp people to work out where it is coming from. There has been many threads about using a blocking cap on the tweets, please do it during the R&D phase. It might save you a few dollars. I might even place a few on the neo10s when I bring them into the system.

I wanted to not go into the big money system until I have everything worked out with the minidsp. I ordered a set of the Alpha-8 Minion from dyisoundgroup. If I blow the CD I can get a replacement cheep, sort of. I'll use the 2x8 for the xover and not the xover with the kit. I also ordered a sub Dayton Audio UM12-22 12" Ultimax DVC and 2ft^3 enclosure from partsexpress. This way I can work with a 2.1 system to see how the dsp works with the sub type setup. I also wanted to work with the xover frequency and waveguides to better understand what I have been reading about waveguides reflections and dynamic range. When I am done with this speaker setup I will use them as an outdoor speaker system. Probably put the smaller minidsp, 2x4 in them. I dont think they will need the power of the 2x8.

Maybe then onto bigger and better things.

Brad


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## Mike P. (Apr 6, 2007)

I believe Parts Express sells the Usher 9950.


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## st.villanus (Mar 1, 2010)

Brad,

Grab an identical sub, and run the two in a stereo bass configuration. Place a sub in each corner of your room and delay the timing of your mid/high drivers. With bi-quads created with REW, you should a very detailed sonic image.


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## broncosaurs (May 31, 2013)

Mike, thanks. PE is where I got them from the first time. I might try something cheaper or the Dayton for the same price. 



> Grab an identical sub, and run the two in a stereo bass configuration


st.villanus, dang, it is only money!

Here is some info from another post from me:

giverago, did you ever get the minidsp running with the alpha 8s ? I too am using a minidsp 2x8 w/ the 4x10 plugin with the alpha 8 Minion and the .6ft^3 boxes. Just getting started. I use REW program/UMIK mic auto eq for the bass and horn EQ. Loaded the biquads into the 2x8 running the speakers in a bi-amp system. Individually checked each speaker’s frequency response, level, polarity and time phase with biquads enabled, and all looked OK. Played some music and the sound seemed harsh, something that would fatigue me real quick. Moved the xover around from 1200-2400, 12-48 db/oct. Added 1/2 -1 lb accustuff to each speaker. Nothing seemed to help. Giverago how did your system/setup end up sounding? Could you post the minidsp file?

Please do not think I am saying this harshness is the speakers fault. I have not tried the xover that came with the speakers. Until I build and install the xover that came with the speaker these comments on the sound are about my tuning. I have had such good luck with the above set up method I thought I would give it a try first. This is the first waveguide/pro woofer I worked with, maybe it is a little different to get set up correctly. I do hear the dynamics and imaging these speakers will offer if I can calm them down.

One other thing, I do have a lot of port air noise. Anyone find a cure for this?

Still working with the xover and filters with the speaker. Getting better but still fatiguing. The miniDSP is so great to do this type of R&D with. I still get a loud thump on power down of the DSP every so often when the amp is on. Working with MiniDSP on this.

Brad


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## st.villanus (Mar 1, 2010)

Brad, 

I sense sarcasm in the response to my subwoofer comment. I understand money doesn't grow on trees. The subs I chose are from RadioShack. The point of my suggestion is that a pair of subs running in stereo with the right placement will astonish you. 

As to the thump you are hearing, it sounds like the gain staging of you setup is open too much on the amp end. Where is the attenuator placed in the signal path?


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## broncosaurs (May 31, 2013)

st.villanus, the "just money" was just for fun. Thank you for the info. When I get this sound ironed out these seoses will end up as outside speakers with a cheaper sub. When I move into the neo3-neo10 system I will use the Ultimax DVC subs in a multi-sub setup as you suggest. I agree that multi-sub system do have a nice sound to them.

Right now the system I am testing/working with is: 

Computer out->MiniDSP->Amp

MiniDSP set to .9mv input and same on output. MiniDSP input/output set to 100%, kind of. The Seos CD output is down 13.2db. Computer volume is the system volume control.

Thanks Brad


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## st.villanus (Mar 1, 2010)

This sounds like a fun project. I looked that amp up. I am quite impressed. It looks simple and effective. 

I speculate the harshness you were hearing is a fault of the system's gain structure. By using the computer as the attenuator, the rest of the components risk getting poor signal. I prefer to attenuate the signal right before the amp stage. That way all the other processors are working with the best signal. Have you tried the ADC mode of the MiniDSP with an external potentiometer? Or, maybe the harshness is caused by a fault in the cables from the DSP to amp. 

In regards to the popping, maybe slaving the auto-on connection of the MiniDSP to the amp's trigger output is a workable solution. In this way, the amp becomes the master power switch. 

Good luck making your system sing.


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## st.villanus (Mar 1, 2010)

I forgot to ask about the state of the port air noise.


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## broncosaurs (May 31, 2013)

st.villanus, I dont think the harshness has much to do with the Computer/DSP/AMP gain structure. This system sounded great on the Usher/Pearless speakers till I blew out the Usher tweets. 

I do have the miniDSP VOL-FP add on which is a master volume control. I could not tell much difference between using the computer volume control with the DSP at 100% in-out or the computer set to give a 90% input to DSP and using the DSP volume. Using the computer is just much more easy. I do have a miniStreamer on the way to keep the computer signal digital into the DSP to reduce on of the DAC-ADC conversions. With the miniStreamer I can bring the digital signal from the computer directly into the digital input of the DSP.

I have a feeling what I consider the harshness of the speakers are in fact the speakers. As I said before I never worked with a compression driver horn/waveguide setup before. I do have them sounding better then when I started by using the speaker's designer x-over and EQ recommendations as a starting point and tuning on that. It is nice the miniDSP has 4 configurations in memory that can be switched on the fly to do sound comparisons. I do find it odd that these speakers can sound so different between different setups even though the measurements are quite close. I just got some f10 felt and more acustuff to play with.

I placed a fast acting control module that has a AC input and dc switched output to control the turn on/off of the DSP. So when the AC supply drops the module tells the DSP to shut down in 20ms. The built up charge in the PS and the 12v input caps on the DSP board must give the DSP board enough energy to shut it down correctly. I haven't had a pop since I added the control module but I do still have some protection caps on the tweets. I think I put Dayton 27uf in line to block the DC of any pop. They will be there until I am convinced the pop is gone.

st.villanus, thanks for the info

Brad


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## st.villanus (Mar 1, 2010)

I'm curious. Have you tried the horns without the caps? It may not make a difference, and then, it might. Also, have you taken REW measurements of the horns at different levels? That information may give you valuable insight. 

I'm happy to read you found a power switching solution. 

If you haven't found success in quieting the port noise, then my suggestion is to cover the inside of the port with some medium density fabric (burlap, old sweater). The low resonant frequency of the port should pass through most porous materials.


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## broncosaurs (May 31, 2013)

Port air noise, even x-overed at 100hz 12db to the sub there is still some noise but not bad. I think i will cut the baffle out and make a full width port. I wont get on this until i feel I am done with the tuning.

Brad


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## PassingInterest (Mar 29, 2009)

Oh man, this is like a cliff-hanger. I can't wait to find out what happens next. No, seriously. We all learn from each other and this is an interesting experiment you have going on. Thanks for sharing it with us. I can't really contribute anything useful, since I haven't yet tried a mini-DSP.


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