ripblade
Super Member
Your numbers check out, but I doubt the arm's mass is that low.Is it possible for a cheap tonearm to have an effective mass of 2.6? Have I done something wrong here? Is this formula no good?
Your numbers check out, but I doubt the arm's mass is that low.Is it possible for a cheap tonearm to have an effective mass of 2.6? Have I done something wrong here? Is this formula no good?
Your numbers check out, but I doubt the arm's mass is that low.
Just pointing out that the resonant peak is (or maybe it's just me..) is the highest measured peak.Not sure what I am looking at there, Rip...
The formula is good but the 14Hz (calculated??? How? you need the eff. mass for this, and you don't have it to begin with) is just a guess, so if the math is right, the result is just a guess.Is it possible for a cheap tonearm to have an effective mass of 2.6? Have I done something wrong here? Is this formula no good?
The formula is good but the 14Hz (calculated??? How? you need the eff. mass for this, and you don't have it to begin with) is just a guess, so if the math is right, the result is just a guess.
This is fascinating to me, but I cannot be bothered to do math where records are concerned, lol.
Watching with great interest.
Gotcha, so it's not calculated, it's just plugged in.If I go by the spectrographs that I posted above (possibly erroneous due to being recorded by crappy laptop's DACs), I see possible peaks at 14, 10 and 8 Hz. If I use these, I get effective mass results of app. 2.6, 7.5 and 12.5.
If I go by the spectrographs that I posted above (possibly erroneous due to being recorded by crappy laptop's DACs), I see peaks (indicating possible resonant frequency) at 14, 10 and 8 Hz. If I use these, I get effective mass results of app. 2.6, 7.5 and 12.5, respectively.
No, Turntable RCAs into 1/8" adapter into the microphone input on my Macbook Pro.
Recorded at 24/96 into Audacity.
All of this makes me feel dumb. I can't follow any of it. For me it's simple. Does it sound good?
All of this makes me feel dumb. I can't follow any of it. For me it's simple. Does it sound good?
Don't worry about it. I had no idea about it either in the first round of vinyl superimacy back in the 70's and it's still mostly academic. It's very similar to figuring out how well a VW beetle can do if we mount it on an 18 wheeler suspension, or visa versa. The resonant frequency is just an uncontrollable cascading "poing" that happens when we subject any spring to vibrations. This frequency changes with the varying of the spring's compression. This always happens, even in a cart, b/c the cantilever is essentially a spring. All we can do is just make sure that frequency is something we can't hear and can't trigger by walking on the floor or by shutting the garage door.Me too !!!
OK, so how do I adjust my suspension on my Marc Morin modified AR XA so I can use it in my main living area without getting foot fall skips? That's really all I need to know how to do. For now, the XA is in the basement system on a concrete and tile floor and SOUNDS FANTASTIC. Bring it upstairs and put it in the mix with my Audible Illusions and Pass Labs gear and it sounds OK, and I can't walk by it without it skipping.Don't worry about it. I had no idea about it either in the first round of vinyl superimacy back in the 70's and it's still mostly academic. It's very similar to figuring out how well a VW beetle can do if we mount it on an 18 wheeler suspension, or visa versa. The resonant frequency is just an uncontrollable cascading "poing" that happens when we subject any spring to vibrations. This frequency changes with the varying of the spring's compression. This always happens, even in a cart, b/c the cantilever is essentially a spring. All we can do is just make sure that frequency is something we can't hear and can't trigger by walking on the floor or by shutting the garage door.
The trick is matching the tonearm effective mass (which is just another name for "inertia") to the cantilever springiness (compliance). There's a formula for this that dates back a couple centuries. It tells you what's the "right" effective mass of a tonearm, taking into account the weight at the end of the tip, and the springiness of the cantilever. All of this aims at keeping the resonant frequency low within the range of a goldilocks zone that's accepted by convention. That range is between 8Hz (8 cycles per second), which is just above the 6Hz of footfall, and 12Hz, which is just arbitrarily bellow the 20Hz that we can hear.
It's worth mentioning that effective mass is the amount of resistance a tonearm exerts to the changes in direction the stylus wants to move to, as a result of reading the groove modulations. A tonearm has it's own inertia, so when a springy stylus wants to suddenly go right while the tonearm is still going left - it's going to encounter resistance. This resistance is going to generate vibrations in the cantilever and if the two don't match, we, in theory, can degrade the sound quality. That's all there's to it.