I've been troubled by a perceived harshness in the high mids from my system for some time now.
I've tried moving the speakers (a bit, at least, my room isn't big enough to allow radical moves), eliminating toe in, and I've tried using makeshift sound absorbers at various points on the walls (heavy towels). I've gone back to stock everything in terms of cables, supports etc, I've done my best to ensure that no signal cables run too close or parallel to power cables. Basically all of the obvious stuff to try.
All to no avail.
So I picked up a Umik-1 and downloaded REW, in order to try to get to the bottom of things. And now I have a 20Hz-20KHz reading of the room taken from the listening position with a frequency response graph, a 'waterfall' plot and so on.
The thing is, I'm no expert at reading this kind of stuff. There's some wrongness going on at the bass end. But I don't have an immediate issue with the bass - I need to solve the high mid problem before worrying about that. Likewise there's an unexpected peak around 18KHz which is way too high to be the issue.
It's perfectly possible that the problem stems from not getting on with the speakers (S-400) and/or the source (usually a 172, but for this test an offboard DAC running into the 172's analogue input) rather than a problem with the room. Or from some other non-room related thing. But this measurement seemed a good place to start.
I've attached images of the SPL graph and the waterfall - does anyone fancy helping me to interpret them?
Posted on: 09 October 2017 by Finkfan
Ok. I’ve found the solution to my audio issue. I REW, under ‘Preferences’ top LH corner, the box pops up with soundcard options. Under ‘output device’ this was set to ‘default device’ by default. Clicked on this for options and clicked on Speakers and all is well again.
Posted on: 09 October 2017 by Finkfan
Did a quick test this evening and here’s the problem area for me, lack of bass. There graph looks pretty much the same from 200Hz up 20,000. No big peaks or nulls. Will do some tweaking to REW and give it another go at the end of the week.
Posted on: 09 October 2017 by Huge
It does look as though you have a serious problem of bass cancellation in your room.
Was this with both channels active or just one?
Is it any different the other way?
Have you tried entering your set-up into the Room Sim dialogue? You can use that to try out theoretical tweaks (or radical changes 
) to your set-up.
Posted on: 09 October 2017 by Innocent Bystander
Adding to Huge's questions, I assume that is measured at the listening position? Very significant roll-off from around 130/140Hz, as well as the strong dips at 49/54 & 90 Hz. Latter most likely cancellation that might be fixed by rearrangement of speaker and/or listening positions, but the general roll-off is more puzzling - It Is a bit reminiscent of a small standmount in a big room! Are they further from the back wall than the manufacturer's recommended distance? Where is the listening position in relation to the back wall?
Posted on: 09 October 2017 by Finkfan
Hi Huge
It was with both channels running. I’ll try it with one channel over the weekend. I’ve not tried the room sim dialogue. Again will give that a look later.
Hi IB
Yes, measurements taken from listening position. My Revel speakers, which aren’t fussy on position, are around half a meter from the rear wall. I have experimented with positioning and it made very little difference to low end performance. The listening position is 1.7m from the rear wall in a 4.5m long, 2.5m wide room. The ceiling is vaulted and peaks at 3.1m running the length of the room. There isn’t much in the room at the moment which doesn’t help I know. In my lounge where my setup used to live, the revels sounded stunning. Plenty of furniture in there though which I’m sure helps a lot.
Posted on: 10 October 2017 by Innocent Bystander
A rather tricky room being that narrow (a converted garage, perhaps?). Time for a stupid question, but worth asking, have you checked the speakers are connected right, and not one accicentally connected out of phase with the other? I've not tried ti assess what that would look like in the plot, but is simple to check.
Posted on: 10 October 2017 by Huge
If the worst comes to the worst, it's curable using a miniDSP 2x4 to connect a sub to the 272. The DSP can be used to control both the crossover to the sub and correct for the room mode fundamentals. It can also act as the line driver to drive a long cable to the sub (hence preventing excessive capacitative load on the output of the 272).
All is not lost - we can retrieve your bass response!
