It's been a long time since I had the tools out, and I've been playing with a lot of ideas so this post will be a bit of a ramble. Remember the SNR-1? A 2-way with a 6.5" Scanspeak Revelator mid-woofer?They are still my personal reference speakers. Several things have come together in my listening area. I am switching over from Logitech Media Server to Roon. Honestly being on a subscription software service bugs me, but Roon's music service and DSP capabilities have won me over. I'm also setting my HT again, and as before, am doing my own room correction.
Anyway dear readers, to take advantage of Roon's DSP capabilities I pulled out OmniMic again (thanks Bill Waslow) and measured the speakers in place. First thing to talk about is just how much bass a good 6.5" driver can produce.The red chart below shows you the original speaker response, while the black is the response after correction:
The Start Line
Some of you may see this 1/6 octave plot and wonder why the bass is already so smooth. The answer is in part the room and in part the room treatment. The wall behind
the speakers has a large opening to the rest of the apartment, making
certain modes very difficult to start. I also use a pair of stacked
Soffit Traps and 5 other acoustic panels around the area. All from GIK Acoustics.
I should be clear here: I cannot achieve results this good with so little compensation without the room acoustics. They enable the EQ.
The Goals
Having
a lot of experience in motion picture measurement and calibration as
well as doing the same in my multiple apartments I had clear and simple
goals in mind. Absoltuely flat response was NOT one of them. Also, I
know the microphone was set low to the tweeter, so I wasn't worried
about the last octave drop-off. I also know how easy it is to get
carried away with EQ, so here were my goals:
- Ensure a smooth bass response
- Match the two speakers to one another
The Process
I played ripped tracks from the OmniMic CD , observed the frequency response in real time while I adjusted the EQ in Roon. Honestly the hardest part of this was figuring out the Roon nomenclature. They use "Parametric EQ" for things that affect all channels, and "Procedural EQ" for exactly the same, but they adjust 1 or more channels.
The Result
Using Roon and OmniMic I was able to very quickly flatten the response with the judicious use of two parametric filters, shown below.
The left speaker is placed much farther away from the side wall, so I really did not have the same issues at all, and it's correction curve is boring. However, I did use the Right channel as a template and forced the Left to match throughout the mid-treble area with a delicate, single filter. The phantom center is much more filled in and voices distinct and close to palpable.
One other thing, take a look at the original chart. This response was WITHOUT a subwoofer! If you make the SNR-1 or buy a model from Fritz Speakers with similar drivers and configuration you are going to get awesome bass out of a small monitor. If you don't, it's your room.
Oh, of course, you could just buy a Wilson or Gamut if you prefer.
Here's more information from one of the most famous kit designers on earth, Troels Gravesen. Most of Troels' kit designs include charts showing how much a speaker changes in a room, vs. the ideal/anechoic expectations. He calls it "room gain" and here is an example from his Fusion kit:
Every room is different, so you can't use these charts to predict the response of any given speaker, but it illustrates the point: The actual bass output of speakers in a room is more than their spec.
Adendum
In the end I added about 3 dB to the bass by using a Low Shelf filter at 82 Hz. It's still not chest thumping, but adds some body to the music. Here's an image of the filters. The Parametric EQ works on both channels at once, so it acts like a tone control. I then used 1 Procedural EQ per channel for the room correction needs which I documented above.
