Over the past few months, I’ve been trying to learn more about room acoustics. After purchasing my FR 10s, I got an RTA app on my iPad and measured the output as part of positioning the speakers. I don’t know much about acoustics, as I said, but I think that this plot is reasonably good. If I’m wrong about that, please let me know. See the graph pasted below, 1/6 octave with slow averaging. There is no room treatment, except that I have a SR Black Box placed between the speakers. Edit: I do have bookcases with LPs and books in the room, which provide diffusion.
I do see that there are a couple of spots where the bass output rises. I wonder if these correlate with the two spots that I hear louder output when I play the bass scale track that is included on the Aspen set up disc. (Is there a way to find out what frequency a particular note is from the CD track?)
I also see that there is a low point around 500 HZ, which seems to correlate with the crossover from the bass driver to the mid range. Is that correct? I can’t think of any way to address this; perhaps it’s not really audible.
That does not seem too bad, I’ve seen worse. As far as improving the bass response the only ways I know are bass traps and active EQ. The two peaks (around 100Hz and 300Hz) could be smoothed with active EQ but this could be expensive and usually comes with some sonic degradation.
Bass traps while not cheap can work without knowing the offending frequencies precisely, you just need to know they absorb frequencies low enough to cover your particular problem.
Since your bass response is not that bad I think traps would help enough to improve the unevenness.
As far as correlating frequency with CD track you would need to know the range, e.g. 20Hz to 250Hz, and the number of tracks. (Assuming the jumps between tracks are the same, like 1Hz or …. The only disks I know of that have explicit correspondence of track and frequency are the ones from Granite Audio and Linkwitz labs. These may not be available now (but possibly used).
By the way what is the Aspen set up disc? It seems I did not get one with the FR30s.
My FR 10s came with a box (one for each speaker) that included a set of Allen wrenches, the user manual, and a set up guide. The FR 10s require only the smallest wrench, but the box has three or four, so I assumed that all the Aspen series got the same box. The setup guide is a small book with a CD in it. In the fourth track on the CD, Chris Brunhaver plays a scale up and down the double bass. Any notes that jump out from the sequence, either louder or softer, indicate an issue. As I said, I hear two notes in the scale as louder.
If it’s a straight scale on the CD, a Cmaj for example, there are pdf’s online that give the note/freq correspondence. I have one somewhere but can’t find it right now.
I found the CD really helpful, because the booklet explains what to listen for as you play each track and offers suggestions if what you hear doesn’t match what’s on the recording. PSA should send you a CD or a set of digital files.
I checked Music Direct and the Granite Audio disc is still available. The one I have is
There are several types of freq tracks. For fine tuning tracks 10 through 99 are useful. They are in 1Hz increments and track number = freq (track 10 = 10Hz, etc).
There are a number of issues with your measurement and I wouldn’t necessarily use it to make too many decisions.
I would recommend spending $75-200 and getting a calibrated measurement mic and start learning a free measurement software like REW so you can tune your system. There are ways to determine if a response issue is room related and tailor some room treatment or EQ around fixing it.
As a starting point, your low frequencies aren’t actually as smooth as as in almost any room and it’s because you are using 4K FFT window size. Please increase to this 16K or higher.
The response aberrations are likely the result of some comb filtering because of the lack of room treatment. These wall/ceiling/floor reflections interfere with the direct sound of the speaker in the range that you’re mentioning. Below a couple hundred Hz, things the behavior of the room are more geometric and modal but above this, sound works a lot like rays of light. Some basic treatment can likely help significantly.
Can you take some pictures of your room in a 360 from the listening position?
Thank you very much for your reply. I will redo the measurements using a larger window size – I didn’t know that mattered (as I said, I’m new at this). There are a few more things going on which I will try to explain.
A year or so ago, I looked into software that would help analyze my room. The ones that I found (can’t remember whether REW was one) all seem to work only with a rectangular room or something close to. I own a Victorian house – think bay windows, pocket doors, etc. Basically, it’s an open floor plan in a highly irregular shape. The area where I listen would be one room if everything were closed off. I do have a rug in this area to help with floor to ceiling reflections.
If I can find software that will help, I’ll buy a new microphone for my iPad. (The one that I bought a while back does not work with the new iPads that have USB-C connectors, even if you get an adapter. I researched this and discovered it’s a well-known problem.) I’ll double check REW. More to follow . . . .
