External vs Internal Horn machines, musing on sound quality

[Phototone]

Many people have remarked over the years that the transition to internal horn machines marked a step-backward in quality of sound reproduction. (Not taking into consideration later folded horn designs).

In electronic speaker practice, a bare paper-cone speaker is far inferior to the same speaker in a baffle. (or box). The bass frequencies are greatly diminished with a bare speaker, as compared to the same speaker in a baffle or box.

Wouldn't this theory also hold true for internal horn machines such as the common Victor or Columbia. Or does the fact that the effectively shorter length of the Horn, when adapted to an internal configuration cancel out any advantage gained by putting it in a baffle (or box, the phonograph case)?

Its true that some of the very best acoustical phonographs use very large external horns, like the EMG, Ginn, Cascade, etc.

[ImperialGuardsman]

This is an uneducated guess so bear with me. I would imagine that in a normal modern speaker, the box would help direct the sound, thus keeping it more focused. Further, I would imagine that the box itself would serve as an area for the sound to reverberate, creating more bass. I feel that phonograph hors already directs the sound. As for revereration in the case, that may have an effect on an internal horn phonograph, but perhaps not a whole lot.

[gregbogantz]

The reason that a "bare speaker", that is a cone driver unit without a baffle board sounds worse outside a box than inside one is that it radiates sound from both its front and its back in nearly equal intensities. The two wavefronts merge at some distance from the driver where the listener is. The shorter wavelengths of midrange and high freqencies are more likely to be in phase with each other and thus enhance those frequencies at the listening location. Actually , there is a comb-filtering effect that causes the frequency response to have peaks and dips. But the front and back radiations of longer wavelengths that correspond to bass frequencies are more likely to appear at the listening location out of phase with each other and thus cancel the total energy which is why there appears to be little bass. Putting the driver on a baffle board reduces or eliminates the back radiation from reaching the listener, so the cancellation of bass frequencies is prevented. Also, the comb filtering of midrange is prevented which makes the response smoother. Also, some speaker boxes are designed such that the back radiation from the driver is delayed and emitted thru a port or duct in such a way that it enhances the front radiation. These type boxes are called "bass reflex", "ported", or "ducted port" enclosures.

A horn does not radiate this way. All the energy emanating from a horn comes out of its mouth. So it matters very little whether the horn is contained inside a box or behind a baffle board or not. The perceived bass content of a horn is dependent on its length and the size of its opening at the larger bell end. The most efficient horns with the smoothest frequency reponse also possess special shapes with regard to how they taper or expand in cross section along their length. The most popular of these is the logarithmic taper which is the type used in Victor orthophonic phonos.

[scullylathe]

Most external horn machines, depending on the construction of the tonearm are closer to an "exponential" taper and at least to me do produce a slightly better sound than some of the early internal horn phonographs. Victor tried to maintain the external horn shape within the design of most "Victrola" phonographs by using the tapered casting that connects the base of the tonearm to the wood part of the horn. Other manufacturers couldn't do this without patent infringement, so there are a lot of other designs and once the original patents started to expire and the "third partiers" started making machines... I have a third party machine that has a fairly well tapered tonearm, but then about a 12 inch solid wood block with a 2 inch hole bored through it, which then connects to a flared, boxy wooden horn. However, the machine has a fairly nice tone to it - maybe passing through the straight wood "pipe" tends to mellow things a bit. There was really no solid science to the design of a lot of acoustic phonographs, other than the knowledge that a taper design was better than a straight "witches hat" style. Wasn't until as Greg pointed out that the Orthophonic design brought acoustic machines to the best reproduction possible in an entirely acoustic system.

[epigramophone]

I don't claim to know much about the scientific properties of horns, but I am convinced that the height at which the horn is placed has an effect on the listening experience.

Most external horn machines sit on a table, a cabinet or, if you are fortunate enough, a matching purpose built pedestal. The sound then emanates from a higher level than that from an enclosed horn machine.

I find the difference particularly noticeable with vocal records, where the sound from an external horn emerges at about the same height as that from a singer in the room. As others have pointed out elsewhere, the dog and the cat get the best seats in the house when some internal horn machines are played.

[Lenoirstreetguy]

The ironic thing about horn design was the fact that the phonograph companies wallowed around in an empirical fog designing machines by trial and error when in fact fairly solid research in horn design had been done pre-Western Electric. John William Strutt...who was also Lord Rayleigh..wrote a ground breaking text The Theory of Sound ( 1877, 1894) in which he touched on horn design. This was then taken up by Professor Webster who published an extensive article on horn theory in 1919. I believe the Western Electric boys were quite aware of this and used it as a very practical starting point. I don't believe Webster's formulae produced a horn which was strictly exponential in profile, but it certainly was a good practical design, according to Percy Wilson's book.
The research departments of the phonograph companies seemed to be rather blind to the scientific concepts of horn design, although in their defense, just about the time Webster's article appeared they were more interested in the experiments in electrical recording which were beginning to snowball all around them.
Victor especially was continually fiddling with the designs for Victrola horns. They were quick to point this out to the dealers about the time of the introduction of the Orthophonic Victrola as if that somehow made up for the lack of any real progress.
The Edison Cygnet horn, I understand, is almost exponential. Magnavox made no bones about the fact that they were inspired by it for their early loud speakers.
I have always been curious as to how the design of the Lab Model diamond disc horn ( the 250 size) and the horn of the largest Brunswick Ultona would fare under mathematical analysis.
Jim

[Edisone]

I have an Orthophonic 8-30X sitting on a sturdy coffee table; if it was any higher, I couldn't reach inside to operate it! I did this to hear if there was a difference, and there definitely IS. Sitting about 6-8 feet in front of it, my ears are about even with the middle of the upper/lower horn mouths, and there's almost the effect of 'stereo'. It's not the same sound as from a single open or internal horn.

Project idea: build a little 'stage' at end of a rectangular room, so your Victrolas can be raised & you can step up to operate them.

BTW, about those Brunswick Ultona machines: Mine has a rectangular horn. Are there many like that?

[larryh]

To my ear the console style edisons tend to project the sound upward somewhat. Standing they have more full sound than when seated in front so the cat and dog will not be as pleased with edisons design. The brunswick made many rectangular horn machines I believe previous to the round styles? I somehow don't find the square horn to be as satisfactory in sound as the round design.

Larry

[estott]

Victor especially was continually fiddling with the designs for Victrola horns. They were quick to point this out to the dealers about the time of the introduction of the Orthophonic Victrola as if that somehow made up for the lack of any real progress.

Victor tried a number of crackpot schemes, fortunately most never got beyond the testing stage- like the notion that putting spring tensioners on the horn slats might improve the sound. They put a lot of effort into the idea of hiding the Lumiere diaphragm inside a case, which would have negated the few virtues that device possessed.