What happened to my bass?


Ok, for those of you willing to read a bit, I have, as usual, something driving me nuts. I'm a speaker builder. Current speakers look like Watt/Puppy, consist of 11 inch Eton, 7 inch Scan Speak, Scan Speak Revelator tweeter. They perform very well and I haven't changed anything about them in 5 years.....but I have changed houses and of course rooms. Prior room was twice the size of the current, rather small, living room. Bass was a tad shy in the prior bigger room which was in a basement with a good amount of exposed insulation and floor joists up above. Current room is plaster covered drywall, bass traps in front room corners. Bass is generally quite a bit better in the smaller room and according to my pipe organ tracks, very low bass is no problem. So, finally, to the point. Yesterday I am listening to Bygone Days (Eileen Ivers violin track) and it dawns on me that that track has sounded different in the past. In fact, on second listen, there are bass notes completely missing that I clearly remember. I assume the memory goes back to the prior bigger, bass-shy room! I just don't get it. My sense is that bass is fuller and more balanced in this room on everything else I have listened to, and then I get to this Ivers track and there are bass notes that actually had some growl to them, completely missing? It's really wierd when you anticipate something in music and it has disappeared. Room null? By the way, it makes no difference where I am in the room. I even stuck my head behind the speakers. Am I the only one whose system drives them nuts from time to time?
240zracer

Showing 3 responses by shadorne

I can only recommend that you perform some measurements with proper software, sound card and microphone.

(Assuming of course that you actually want to understand what is going on, which is not obvious as most people here on Audiogon prefer to muddle along changing this and that in an endless merry-go-round. Of course each time around the carousel these audiophiles are excited at the new improvement brought about by their latest monthly tweak. And the lack of any rigor in this approach allows them to justify just about any change as an upgrade.)
77jovian,

There are several options. Room EQ Wizard (PC) or Fuzzmeasure (MAC) are possible software options. Since you need a microphone and good ones are powered by phantom then you may as well get a E-MU 0202 or some other similar USB box that does A to D and D to A as well as powering a microphone. Finally a microphone and a stand. A cheap but good microphone is the Behringer ECM8000 but there are several other options. I like Fuzzmeasure because it uses frequency sweeps, which has significant advantages in being able to perform more powerful analysis. (Mathematically speaking a frequency sweep can be auto convolved to get a dirac function which is like an impulse response. The only complication of this more powerful analysis technique is you need to know a bit about appropriate 'windowing' so as to ensure you interpret the data properly and do not get hung up on window artifacts - in general the software and help files are easy to follow and their is plenty of information about fourier transforms and spectral analysis on the web)

Fuzzmeasure
I posted this on Ethan Winers forum as well. His response: "Yes, it is probably one or more deep nulls". And he also says to measure the room.

A good track to test in room bass response is Rebecca Pidgeon Spanish Harlem. The bass line should stay nice and even. If some notes jump out and some disappear then you have a problem. (I found this trick from Bob Katz either from his website or his book on Mastering)