Measuring audio system and miniDSP's

Out of interest, I just remembered a cheap(ish) cheat I tried once while experimenting. If you have an integrated amp that cannot be preamp/power amp split, but you have a tape monitor switch, you can do the following when using subs. Obviously if you can split the pre/power, or if you have separates, it's even easier.

1) Beg/borrow/steal or buy a cheap active crossover (e.g. Behringer 2310 - about £90) and set it up as a stereo 2 way crossover.
2) Get some decent phono to XLR leads.
3) Connect the input to the crossover from the tape out connection on the amp.
4) Feed the high output from the crossover to the tape in connection on the amp.
5) Feed the low output from the crossover to the sub (with the sub filter switched off).
6) set the crossover frequency to about 120Hz.
7) Run the system so that you are listening to the tape monitor and then play with the levels and C/O frequency to get the bass - mid/high balance right.

For me, this was actually a precursor for going 3-way and eventually fully active, having gone through bi-wiring and bi-amping as well.
The hard bit is convincing the wife that "Yes we do need a hi-fi rack that looks like it came out of a recording studio" :rockon:
 
Had to read that a couple of times. Assume you mean a grid around the chain in the horizontal plane so you get a more average view on the listening position?

Like an array of 9 testing points?

View attachment 1108478


I suggest VERTICAL plane, like 3 rows of 3 points: center, left, righ, at, higher and below (feet from each other) head position. For me that worked rather well.

Also sub should be further away from the seat - as far as practical.
 
I suggest VERTICAL plane, like 3 rows of 3 points: center, left, righ, at, higher and below (feet from each other) head position. For me that worked rather well.
As AK readers will now know, my system is fully active, but a few years ago I tried the 2-way mains + both single and stereo subs setup. I never found a way to integrate the subs properly (and I really did try hard). From discussions on various audio forums over the years, it would appear that it's actually very difficult to get sub integration right. The main area of trouble seems to be around the 60 - 100Hz region - precisely where you say you are having trouble.
This might be worth a try. Tune your sub filter to about 100Hz rolloff and then turn the bass down on your main amp. Bass control shelving filters are usually set at about 100Hz. Oh, and try it with the subs either side of the mains. What you are basically doing is turning your system into a 3-way setup at a crossover frequency where the bass is still fairly non-directional. It will take a lot of fiddling to get the relative levels right, but it might be worth a try.
Also, as a possible bonus, what I have found is that with small mid/bass drivers, when they don't have to play the bass frequencies the midrange clarity improves considerably. If you get any joy with this, it may then be worth switching off the internal sub filters and going the active filter route. This would feed the mid+treble to your stereo mains and the bass to the subs, but in a much more controlled manner.

100Hz is too high for the sub. I would cross it at 40Hz, unless VERY steep filer is used (which can cause ringing).
 
I agree that 100Hz is too high for a sub when using it normally. The OP stated that he appeared to be getting a suckout at around 80Hz. I would imagine that this is probably due to the natural rolloff of the bottom end of his main speakers and the sub rolling off at a lower frequency than this, thus kind of leaving a gap in the system response.
What I was suggesting was to rolloff the mains below what they can't achieve properly anyway and rolloff the subs (with their internal filters switched out) at the same frequency so that the sub fills in the area that the mains are not doing very well. What this may also do is to stop the mains getting bogged down with high excursion low frequency sound that they are not really good for anyway, and allow them to concentrate on the midrange which they should do better at because their overall excursion is lower. Most sub drivers should be able to work at 100Hz anyway and it doesn't hurt the amplifier. Does all that make sense?
I'm not trying to turn it into a proper 3-way system, but this may ease the suckout problem the OP appears to be having. And it's cheap, reversible and a good excuse for having a play.
 
It will be interesting to check the response of the mains only and subs to truly gauge what’s going on. I’ll try all that’s being suggested after I do some basic initial tests.

As an aside I’m thinking that I will grab the miniDSP and try using it in a couple of different ways to see how it works out. Wondering if those in the know can confirm if what I’m thinking would work. Both would use the miniDSP 2/4 HD between the preamp and main amp jumpers.

1. Use the miniDSP to EQ correct the main amp based on the specific listening position. Continue to run all speakers full range and subs off speaker level inputs. Crude EQ’ing for all drivers essentially and use the crossover on the subs.
2. Use the miniDSP as an active crossover, 2 of the outputs running back in to the amp to run the mains (LS50’s with the option of a high pass filter) and the other 2 outputs to run an RCA cable directly to the individual subs (crossover on subs deactivated and low pass filtered).

I assume I have the use of the miniDSP right? I wasn’t sure why they offered a subwoofer version of the miniDSP and if I actually needed that instead. But seems like 4 outputs are more than enough for any needs.
 
Thanks for the shoutout, @neevo!

First of all give yourself a pat on the back for deciding to explore measurements and tweaking your system. When it comes to acoustics, my motto is, 'fight science with science'. Listening is important but measurements take out so much of the guesswork.

Anyhow, regarding your space. That's a tough space to work with. My recommendation would be as follows.

Have the LS50s on the opposite wall they are now (where the fireplace is). You would need to find a way to make the wiring look tidy. It can be done, though. The stereo stand with the amplifier and turntable would be off to the side. This way the fireplace remains unblocked and the space will still look clean and tidy. This will give you the best possible stereo imaging and also will give the LS50s room to breathe. Your biggest opponent right now is reflections within that space, and the odd layout with the three chairs, as well as the restriction by the fireplace, is going to make it really hard to get great sound the way it is set-up now.

Next, regarding your subwoofers, I would leave Sub 2 where it is (if you follow my advice above), but place Sub 1 along the west wall. Placing them in opposite corners doesn't work very well, I've found. You want to mix up the phasing and alignments of the subwoofers.

Regarding the miniDSP I have not looked much into that, so I cannot comment there.

Finally, the way you said you wanted to run everything (run speakers and subwoofers full range) would be my recommendation. You want as many low frequency sources as possible. Start with an 80Hz crossover point. This is what I am using with my LS50s.

Let me know what you think of my suggestion, and share your measurements once you get the UMIK-1.
 
Thanks for the shoutout, @neevo!

First of all give yourself a pat on the back for deciding to explore measurements and tweaking your system. When it comes to acoustics, my motto is, 'fight science with science'. Listening is important but measurements take out so much of the guesswork.

Anyhow, regarding your space. That's a tough space to work with. My recommendation would be as follows.

Have the LS50s on the opposite wall they are now (where the fireplace is). You would need to find a way to make the wiring look tidy. It can be done, though. The stereo stand with the amplifier and turntable would be off to the side. This way the fireplace remains unblocked and the space will still look clean and tidy. This will give you the best possible stereo imaging and also will give the LS50s room to breathe. Your biggest opponent right now is reflections within that space, and the odd layout with the three chairs, as well as the restriction by the fireplace, is going to make it really hard to get great sound the way it is set-up now.

Next, regarding your subwoofers, I would leave Sub 2 where it is (if you follow my advice above), but place Sub 1 along the west wall. Placing them in opposite corners doesn't work very well, I've found. You want to mix up the phasing and alignments of the subwoofers.

Regarding the miniDSP I have not looked much into that, so I cannot comment there.

Finally, the way you said you wanted to run everything (run speakers and subwoofers full range) would be my recommendation. You want as many low frequency sources as possible. Start with an 80Hz crossover point. This is what I am using with my LS50s.

Let me know what you think of my suggestion, and share your measurements once you get the UMIK-1.
I have my speakers on each side of my fireplace. Luckily there is a slot at the back of the mantle. It makes it easy to run speaker wires to the other side. My equipment is off to one side againts a side wall. I plan to replace the mantle to add more space in the back for HDMI cables, ect. since my tv is above the fireplace. The speaker wires running down the side of the fireplace are pinned into the corners where the brick meets the wall. Ill probably add a couple of those thin fairly flat cable conduits in place of how they are kept in place. The same conduit used to run power to say a ceiling fan. Being mounted there they wont really show and they do come in colors.
 
1. Use the miniDSP to EQ correct the main amp based on the specific listening position. Continue to run all speakers full range and subs off speaker level inputs. Crude EQ’ing for all drivers essentially and use the crossover on the subs.
2. Use the miniDSP as an active crossover, 2 of the outputs running back in to the amp to run the mains (LS50’s with the option of a high pass filter) and the other 2 outputs to run an RCA cable directly to the individual subs (crossover on subs deactivated and low pass filtered).

I assume I have the use of the miniDSP right? I wasn’t sure why they offered a subwoofer version of the miniDSP and if I actually needed that instead. But seems like 4 outputs are more than enough for any needs.

4 outputs are exactly what you need

Actually you can EQ the mains, EQ the subs, set the crossover point(s)/slope(s), dial in time delays, adjust levels, and so on for each channel using the 2x4 HD1 plug-in (software). The hardware doesn't care how little of the capability that you use.

https://www.minidsp.com/images/documents/Product Brief-2x4 HD1 plugin.pdf

Add the mic and REW and you can try the auto-EQ wizard. Got to love the auto part.

https://www.minidsp.com/applications/auto-eq-with-rew

All this power for the cost of a few fancy (not that fancy) interconnect cables....and a couple hours worth of reading and tweaking to get through the learning curve.

Good luck!
 
I’ll also be interested to measure my amplifier before and after a total restore/recap. Interested to see if it does anything for the sound or just a peace of mind modification.
 
@canuckaudiog is there a need for me to have the 2/4 HD over the standard 2/4?

If the quality of the DAC is improved then I’ll go the HD. Also I’m hoping to create 2 room setups for the 2 different listening positions. Would that be possible with the HD and would the remote allow me to simply switch between the 2?
 
UMIK-1 arrived today. Haven't really done anything meaningful with it as all I did was stack it on top of the laundry basket with a yoghurt maker to bring it up to ear level. I wanted a fast baseline (and a rough one) as I am recapping my amp and wanted to see if it actually made a perceptive different with the software. The results are so cool and fascinating at the same time!!!!

Here's the layout as I had it, as I mentioned I didn't do anything special, just pointed the mic in between the mains and measured mains, mains and subs together, subs only.

1631C97F-3078-4266-8EB3-F17509F897DD.jpeg

What did I learn? Well I am not going to toot my own horn but I do have a room node in exactly the spot I thought I would in listening position 1; 150hz. The other thing that is amazing is how flat the response of the LS50's is above 200Hz, very impressive and nothing really needs addressing as far as I can tell above that level. It appears most of the work needs to be done on the room node. The last thing that very surprising is how deep the LS50's go, looking at the subwoofer overlay its not really adding much and I suspect I can drop the crossover right down and boost the gain a bit to get some lower end.

I might be reading the graphs wrong though so hopefully those in the know can direct me on my test run.

Mains only:

Position 1 Mains Only.jpg

My observations:
1. Response is pretty flat from 50 - 20kHz excluding the 120-150 room nodes. Not sure I can fix that other than some room treatments as the subs only have a frequency response of 35Hz to 120Hz, so it seems to be an issue with the mains.
2. Seems like some EQ could really have a dramatic impact here with a target level around 85 dB
3. There's a surprising amount of bass considering these are LS50's only!

Mains with a separate overlay for the subs:

Position 1 Mains and Subs.jpg

My observations:
1. The subs are filling in a little bit but not really in a way that I would say is benefiting the system much other than the 10dB boost under 40Hz, looks like I need to think about crossovers and gain to get the most out of it all. Stands to reason why I couldn't tell if the subs were on when I put the LS50's on this new amp. One benefit could be though that I could high pass the mains in the future and take the pressure off the amp. I could crossover around 70Hz I reckon.

Full system test:

Full System Test.jpg

My observations:
1. Obviously huge peak around 40Hz, surprised it doesn't sound too overbearing, maybe its accentuating the dip around 120-150Hz, not sure until I can test some EQ.

I was going to try to create a equalised curve but can't work out how to do it yet. Need to read up on how to use REW a bit more!
 
Wait... found the button. Here's a rough cut matched response. No crazy sharp filters and reduced the peak to trough to only 13dB, however did this with the original smoothing on the graph which is probably the wrong way to do it.

Matched Response to Target.jpg
 
Last edited:
Question about subwoofer cables. I have a miniDSP on the way and I’d like to try using it to run the subs off vs running them off the speaker level inputs.

With a max 7m run of RCA cable needed. Should I buy a quality cable like Van Damme Patch Pro or can I get away with a much thinner option like I have the subs running off at the moment (QED Micro Speaker Cable)?

Is it worth trying it out first with some cheap cables or will I potentially ruin the subwoofer performance?
 
With a max 7m run of RCA cable needed. Should I buy a quality cable like Van Damme Patch Pro or can I get away with a much thinner option like I have the subs running off at the moment (QED Micro Speaker Cable)?

Is it worth trying it out first with some cheap cables or will I potentially ruin the subwoofer performance?

The improvements from good EQ and sub placement will he obvious both to the ear and in measurements. That is unlikely to be the case with a more expensive cable. Unless money is no object and you like the look of the fancy cables, I'd focus on the former.
 
Is it worth trying it out first with some cheap cables or will I potentially ruin the subwoofer performance?
Sticking purely to electrical principles, a subwoofer cable is carrying low frequencies and the electrical demands are negligible. Any cable that isn't outright damaged or broken will be fine.
 
I’ll also be interested to measure my amplifier before and after a total restore/recap. Interested to see if it does anything for the sound or just a peace of mind modification.

I'm going out on a strong limb here to opine the amp is not what is causing the "holes" in your response.

If the holes are truly "suckouts" as some have described, you really can't EQ your way out of them...at least not very effectively. It's sorta like trying to fill a black hole doing it that way because they are actually cancellations of the waves. You can make bigger waves but they still cancel each other out. Those have to be handled more by arrangement and room treatments to change how the waves interact in the room.

Edit: Sorry...didn't get to your more recent posts before replying.
 
Last edited:
The improvements from good EQ and sub placement will he obvious both to the ear and in measurements. That is unlikely to be the case with a more expensive cable. Unless money is no object and you like the look of the fancy cables, I'd focus on the former.

I’ll do that first for sure and test EQ on the current setup (mains and subs off same amp with speaker level connections). However I’d like to try the subs on RCA’s directly off the miniDSP and I don’t have any cables on hand.

I’ll grab some cheap ones to see if it’s worthwhile.
 
If the holes are truly "suckouts" as some have described, you really can't EQ your way out of them...at least not very effectively. It's sorta like trying to fill a black hole doing it that way because they are actually cancellations of the waves. You can make bigger waves but they still cancel each other out. Those have to be handled more by arrangement and room treatments to change how the waves interact in the room.

Edit: Sorry...didn't get to your more recent posts before replying.

That’s my assumption too. I was going to play around with speaker/sub placement and see if I could improve things. I was also wondering if time aligning the speakers might help too as it should change when the frequencies align?
 
Back
Top Bottom