Altec Stonehenge III Studio Monitors

[tubedelights]

Hi all,

I have some queries regarding the specifcations & performance of the Altec Stonehenge III Studio Monitors.

Just wondering whether there are any fellow members who are owners or have experiences with this pair of speakers, and would like to comment on the following observations;

Based on the dimensions of the Stonehenge III Enclosures, the speaker is about 5.62 cubic feet.
I calculated the cabinet tuning to be at 27.7 Hz
But why does Altec report the response as only 50 - 20000 cycles ?
Could it be the speakers are optimized for Vocal Performances ?
But why then tune to 27.7 Hz
If response to 50Hz was all that was desired then why not tune the cabinet to 55 Hz or so ?
If you tune the cabinet to 27.7 Hz, then we should expect flat response to 1/3 octave below this ..... or 20 to 25 Hz
Perhaps this is the true response of the Stonehenge III Speakers.


.

[GM]

>Based on the dimensions of the Stonehenge III Enclosures, the speaker is about 5.62 cubic feet.

I calculated the cabinet tuning to be at 27.7 Hz
But why does Altec report the response as only 50 - 20000 cycles ?

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OK, where can I find the specs? I only have up to SH II.

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>Could it be the speakers are optimized for Vocal Performances ?

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Can't really comment until I know more.

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>But why then tune to 27.7 Hz

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Not to put too fine a point on it, I've never seen an Altec factory cab tuned this low, so I have to wonder if you made an error.

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>If response to 50Hz was all that was desired then why not tune the cabinet to 55 Hz or so ?

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Why not indeed! SH I, II is tuned around this frequency IIRC.

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>If you tune the cabinet to 27.7 Hz, then we should expect flat response to 1/3 octave below this ..... or 20 to 25 Hz

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Not really, it depends on the driver loading.

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>Perhaps this is the true response of the Stonehenge III Speakers.

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Again, all Altec designs I've reverse engineered are slightly underdamped, and based on the published response expect tuning for the SH III to be no different.

GM

[tubedelights]

Hi GM,

Thanks for the response.

The Altec Stonehenge IIIs cabinet has a very small port with a rather long port tube.

The cabinet tuning was re-calculated and found to be indeed 27.7 Hz

This is very very low & points to it's intended use in Recording Studios as a Reference Monitor !

It uses the Altec Model 604-8Gs .... 15" bass driver with co-axially mounted Sectoral Horn & compression driver.

The Official Published Specifications by Altec Lansing can be found at the following web page;

http://www.lansingheritage.org/image...me/pages07.jpg


Thanks,


David

[GM]

Greets!

You are welcome! Interesting, the link is correct, yet it does not work for me unless I cut and paste it into the address bar. Since internal dims are not published in the link, there is no way to determine the vent length, bracing, net Vb from a photo, so unless you post all the necessary dims that allowed you to calculate Fb to one decimal place, then based on what I do know about many of Altec's designs I still think you have made an error in your calcs/assumptions (if any).

Anyway, in retrospect, my tuning remarks WRT earlier designs was a bit too general/misleading in that typically Fb was around a slightly underdamped 35-40Hz after the internal wiring and inductor's series resistance (combined with the amp's DF back when tube driven) is accounted for, which means a usable lower aneochoic limit (full space) of ~50-55Hz. If placed up against/in a wall and factor in a bit of room gain, then ~35Hz is a realistic in-room Fb. With what little info I get from the catalog, the SH III's design appears to be more of the same, just a bit more honest.

GM

[jmarkwart]

Howdy!

I have a great blueprint of the Stonehenge III (3577A) that was re-created by Jim Easley. The Vb is indeed 5.62ft^3, and the vent is shown (in inches) as 5.5 H by 2 13/16 W by 4.0 L. In addition to the usual cleats, there is also a 1 1/2 by 3 1/2 lateral brace that the 604-8G magnet is cradled in, as well as 3/4 by 2 5/8 and 3/4 by 4 fore and aft braces. So, after deducting the speaker and crossover volume make sure you deduct for some extra lumber! I wagged 5ft^3 as the net volume and plugged it into WinISD to get a tuning frequency of 33.5Hz using the supplied Qts of .25. If a couple ohms of series R brought the Qts up to .27, the response would be nice and flat with a -3dB point of 52Hz.

Jeff

[GM]

Greets!

Thamks for the info! As I figured, good ol' Altec was nothing if not consistant. Glad to hear they finally decided to support those heavy drivers.

GM

[tubedelights]

Hi GM,

Thanks to you and Jeff for highlighting and resolving the mixed-up regarding the tuning and performance specifications of the Altec Stonehenge III Studio Monitors.

I really appreciate all the feedback and comments

BTW, GM ..... you will note from Altec Official Published Specifications on the Stonehenge II speakers, the freq response reads as 35Hz to 20 kHz ........ maybe you would like to say something on this.

And if Mr. Todd W White is reading this, can I just say somthing ......... I'm still waiting for your response & reply regarding the pair of custom-made Stonehenge V speaker enclosures.


Rgds,

David

[Richard C.]

The actual link is: http://www.lansingheritage.org/image...ome/page07.jpg There was an extra "s" added to "page07".

[Todd W. White]

Hey David - I'll get back to you on the enclosures Monday or Tuesday: I'm finishing up two sets for someone else and got behind, so I'm trying to get them shipped.

Sorry for the delay.