The Arm/Cartridge Matching Myth

This Resonant Frequency has ZERO affect on the sound quality of a particular tonearm/cartridge combination and I have proved it hundreds of times with a dozen different arms and over 40 cartridges.

Hi Halcro . . . I think the main conceptual problem here is that the resonant frequency is only one parameter that's descriptive of the tonearm/cartridge resonance envelope. Keep in mind that the tonearm/cartridge combination is a mechanical high-pass filter, and if there is a resonant peak . . . mathematically it must be a multi-pole system. This means that affecting any element changes not only the resonant frequency, but the width and height of the peak (Q), the transition-band slope, and the amount and periodicity of any pass-band ripple.

The difference between 8 and 12 Hz really is very little in the frequency domain - at 1/3-octave it's the same as two adjacent bands on a 31-band EQ. And while the tonearm/cartridge system is indeed multi-order, its filter slope isn't anywhere near steep enough to make much difference in LF response or warp-immunity simply with a change of frequency. Rather, the effect of raising the tonearm mass for a given cartridge usually increases the Q of the filter in addition to lowering the resonant frequency; that is, the resonant peak becomes higher and narrower.

The trade-offs of raising the system Q are the same as for any electrical filter: the "benefits" are that the transition-band (immediately below the resonant frequency) becomes sharper and more selective, and the pass-band (area above the resonant frequency) becomes overall "flatter". The "drawbacks" are that the system becomes dramatically more sensitive to energy imparted at the resonant frequency, the pass-band ripple increases, and increased ringing in the time-domain (impulse) response.

Pragmatically, the main issue will be the extent to which your turntable and environment conduct energy into the tonearm/cartridge system, and at what frequencies. If you're using non-suspended turntables, on sturdy furniture, in a concrete building, then you're probably going to have fewer issues with subsonic resonances, but your system will be more prone to acoustic energy conducted back into the tonearm . . . and a heavier, more rigid tonearm definitely helps to control and dampen this.

But for suspended turntables, springy wooden building structures, heavy support furniture sitting on carpet etc. etc. . . . indeterminately increasing the Q of the tonearm/cartridge system is playing with fire. Each of these additional spring/mass systems can potentially combine to create a condition where the system is extremely sensitive to subsonic and low-bass energy. Many view this as a reason to universally condemn suspended turntables . . . but it's simply a different type of energy to which the system is susceptible, and the trade-off for better immunity to conducted energy within the audio range.

But regardless of the type of turntable design, domicile construction, or support furniture . . . I seem to see fairly regular inquiries on these fora for help to solve the issue of woofer-pumping while playing records. Much of the time the owner has already followed this sort of advice . . .

The best match for ANY cartridge ever made….is simply the very best tonearm you can afford…whatever its Effective Mass

Given that the prime mechanism determining susceptibility to this phenomenon is the tonearm/cartridge resonance envelope . . . the notion that this issue could be avoided simply by spending more money on a "better" tonearm seems a bit unreasonable to me. It's simply far more effective to change to a lower-compliance cartridge, thereby creating a system with a lower-Q resonance envelope at a slightly higher frequency.

Thank you all for the kind words, and thank you Al for correcting my sloppy math . . .

On the issue of acoustic feedback, I'd just like to add that it rarely occurs at the tonearm/cartridge main resonance point, simply because it takes a speaker with extremely powerful subsonic response to produce enough energy to "close the loop" at these frequencies. But with a big subwoofer, it can definitely happen. Usually it seems to occur at a frequency that's modally related to room dimensions, or in the mid-bass region where the loudspeakers are efficient, but the turntable's suspension isn't.

I have (and had) combinations which have been between 9.7 -10.0- 10.4
Nearly super (from that Theory) but I was amazed that some carts performed MUCH better in Arms where the "calculation" showed different datas.

If you're not actually measuring the resonance point, there's no way to know whether or not you're getting the best results within a given range. Keep in mind that manufacturer compliance and effective-mass data varies wildly in its accuracy - and poor data isn't an indicator that the theory of operation is incorrect. Similarly, many speaker drivers have inaccurate specifications for their Thiele-Small parameters . . . but this doesn't mean that the matching of the driver and the cabinet is any less important.

Of course, the tonearm/cartridge resonance envelope is just one of myriad factors that determine sound quality in LP playback, but it is one of the fundamentals. It's also something that is particular to playback . . . that is, it's one of the ways in which a turntable is fundamentally different from a cutting lathe.