About horn length...

[HMVDevotee]

I've read some excellent posts here regarding the acoustical properties of horns and the complicated dynamics involved in transmitting the waves of sound generated by the from the diaphragm through the column of air that ultimately becomes the interface with the air in a room.

Base response seems to be highly dependent on horn length and I can personally attest that there is no comparison between my Brunswick Cortez and HMV 193 for base reproduction; the metal re-entrant horn of the 193 is a complex acoustical marvel.

As well, I assume the quality of the sound of the HMV102 portable is in part due to HMV's horn design that seems to maximize length, relying on the interface with the air in the room to include a reflection off of the open lid. What I find curious is that the big HMV tabletop machines do not appear to maximize horn length, with what appears to be about a 90 to 120 degree bend in the horn on its way to the front of the casework instead of the 300 degree bend (approximately) in the 102.

I've not heard an HMV130 in person and was wondering how their base response compares with other similar machines. As well, since horns are highly directional in their efficiency in transmitting certain frequencies, I was wondering if the forward-facing horn, and its shape, is a bigger determinate in base reproduction than horn length.

Are there any table-top machines that have a deck arrangement similar to the HMV102 (as found in the HMV461 currently on EbayUK) or, perhaps turned 180 degrees with the tonearm fitted in the front of the machine, just above the horn's mouth, with a longer horn that wraps around the motor on its way to the front of the machine.

[Daithi]

I am currently building a landscape style portable with the tonearm facing in a parallel direction with the front of the machine. One of the reasons that this configuration was not used much in the past is that with the diaphragm facing towards the listener needle scratch was more audible.

[AZ*]

While not a large table top machine, the HMV 103 and its siblings equipped with #4 soundboxes do have longer horns than the similar looking Victrola VIII. Although not in the same class as the HMV 193, the HMV 103 absolutely outperforms a Victrola VIII due to soundbox and horn configuration.

[OrthoFan]

... As well, since horns are highly directional in their efficiency in transmitting certain frequencies, I was wondering if the forward-facing horn, and its shape, is a bigger determinate in base reproduction than horn length.

I've always understood that the length is the determining factor for bass response, providing that the horn's expansion follows an exponential design.

This document provides some graphs illustrating the horn's length and corresponding bass cutoff:

Whats the best loudspeaker and why.pdf

(886.24 KiB) Downloaded 58 times

OrthoFan

[HMVDevotee]

AZ, thanks for the illustrative image. I wonder if the HMV130 has the same horn configuration. I have searched the internet and cannot find an image of the horn used in it.

Orthofan, thanks for the linked article... very interesting.

[OrthoFan]

AZ, thanks for the illustrative image. I wonder if the HMV130 has the same horn configuration. I have searched the internet and cannot find an image of the horn used in it.

Orthofan, thanks for the linked article... very interesting.

The HMV 130 horn is shown in this post string -- viewtopic.php?f=11&t=30621

HTH,
OrthoFan

[Daithi]

This document provides some graphs illustrating the horn's length and corresponding bass cutoff:

Whats the best loudspeaker and why.pdf

OrthoFan

The author seems to favor ¼ inch Bakelite in preference to metal as a horn material.

[HMVDevotee]

Gentlemen All,

Thanks for your input and observations. I don't think I've ever seen a bakelite horn! How interesting!

OrthoFan, thanks for the link to the thread with the image of the 130 horn... don't know how I missed it.

Great forum... helpful members!

HMVDevotee