Air Tight Seals

[Phototone]

I often wonder, as I see people post photos of their acoustic machines, about the "air-tightness" of the various types and designs of tone-arms. I know the more air tight the better the sound quality, from sound-box to flare-end of horn. In that regards, the earliest designs that just had a leather-elbow between reproducer and horn might be giving the best seal, although more weight and mass on the record due to the long support arm and horn. Edisons best machines always had a near air-tight seal from reproducer to horn, and his machines sound darn good (disc and late cylinder) but he (his company) also excelled at recording.

Some lateral disc machines, even of very high quality or price only seem to have rudimentary attempts at giving a tight air passage. Many tone-arms look like they would leak air like a sieve.

The products of the Victor company (of course they had patents) seem to be better than most but what is the opinion of this board? What machines would you characterize as having the "best" and "worst" air-tight seals? And in addition, what advice can be given to increase the efficiency of getting air tight seals? NOTE: I'm talking about the pre-orthophonic era, in other words prior to 1925.

[estott]

Frequently you can improve the tightness of a tone arm seal with very thick grease, but that will only go so far until it becomes either messy or it adds undesirable drag- free movement of the arm is important.

[gregbogantz]

The importance of the air seal is primarily related to providing good bass performance, so it became quite important in the orthophonic era where the horns were finally big enough and properly designed to actually support bass down to around 100 Hz. Beyond that, air tightness does improve efficiency (loudness), but it is of secondary importance in the overall scheme of things, particularly in the pre-ortho machines. For example, I have a Pathé desktop model P with outside horn that plays significantly louder than any of my Victor or Edison pre-ortho machines. Yet the tonearm joints at several places around the pivots are ridiculously loose and leaky - they were designed that way. It doesn't have any bass, of course, but none of these early machines do because their smallish horns are incapable of supporting bass frequencies. Where air tightness WOULD matter in an early machine is when you use them with listening tubes and earphones. In this usage, you would be able to hear the improved bass from the tight air seals.

With regard to the question of which early machines had the best air seals, I would suggest that probably the Edison machines would win this contest. There are no sliding or rotating seals in most of the early Edison cylinder designs, so they are pretty airtight. Likewise, the only connection which even has a seal to worry about in a DD player is that between the reproducer and the tonearm/horn. That is already pretty tight by design, but you can improve it if you like by putting grease on the parts. Note that there is no rotational seal involved in the vertical motion of the DD stylus and weight assembly or in the lateral rotation of the horn/tonearm by design. In contrast, the Victor and Columbia as well as the very leaky Pathé machines have sliding or rotating seals in usually two places that are much harder to make tight because they MUST be free to move while the record is playing.

[estott]

I found an interesting reference on this matter in (I believe) a 1906 Sears catalog. They list a metal coupling for their cylinder machine horns (what we term a "Tizit") but they say that it is most useful when a horn must be removed often- in other cases a rubber connection will give the best results. I like that- they admit that the cheaper option actually works better.

A bit OT, but in the tool section they say "Cast Iron nail hammers are NO GOOD" and give a list of dangers, such as the liability to shatter. They continue..."If you MUST have one we will sell you one for 5 cents...you will be sorry if you buy it. Can't you pay a little more and buy a GOOD hammer?"

[VintageTechnologies]

The worst tonearm leaks that I have seen is on a back-mount Oxford (Columbia) cylinder phonograph; a coupler between the reproducer and arm is very loose fitting; the arm also swivels in a leaky joint, and I think the sound is cut by half.

Also bad are the Pathé outside horn disk machines, but they can be so loud that it hardly seems to matter.

I posted on another thread that when Brunswick patented their 3-way Ultona reproducer, the patent described a liquid seal for the tonearm base. Curious, I removed the tonearm on one to see, and sure enough, the edge of the tonearm swings between two concentric rings that appears it could be filled with oil. I have not tried that yet.