The Altec 615B Duplex / Coaxial

[Earl K]

Hello

- Something to look at . :p

[Earl K]

Followup pics :)

[chaslieb]

Hi Earl,

Had these speakers for years but never built a box as I could never get specs on them. Different forums show how little is known about them. Some say they have the same drivers as 605b's but trying to get info about even the 605b's has proved difficult. If you have any parameters to help in box design, please let me know. It was said the 605 was rejected because of poor sound when placed in boxes designed for the 604. If this is the case, I do not wish to place these speakers into boxes that are not appropriate for them. The usual altec box is 9cu ft but the TS parameters for a 605a suggest a 4 cu ft reflex box would be better. Please let me know if you have specs on the 615b or even 605b as I wish to put these drivers to use.

Thanks,

Charles

[Earl K]

Hi Charles,


Please let me know if you have specs on the 615b or even 605b as I wish to put these drivers to use.

- Sorry, I don't have any TS parameters for either the 605a or 615b ( woofer sections ) .

- If they were mine, I would treat the woofer portion as a 16 ohm, 416-8b and system align them accordingly . That means following all of the "old & ancient" Altec guidelines ( pre - Theil & Small ) .

- Scan the basic info in Altec Enclosure Plans (http://www.lansingheritage.org/html/altec/plans/altec-plans.htm) section for some ideas. Particularly, the 1974 Enclosure Manual (http://www.lansingheritage.org/html/altec/plans/1974-enc-manual.htm) is somewhat useful.
It appears to recommend a 7.5 cu' enclosure as being optimal for the 416-8b .
- As an excercise, run the known TS numbers for the 416 , aligned in a 7.5 cu' cabinet.

- You've already ( seemingly ) run into the paradox that Altecs woofers really don't align very well, from their published TS numbers. You'll need to pursue this paradox with someone else who has been around Altec for decades ( someone like GM who you can find posting in other forums ). He may be able to offer some wisdom on this matter ( he uses 515s in huge boxes ) . I'm more of a JBL woofer guy ( have been, since the 1970's ).

ps ; What I'm getting at here, is the "belief" that if it doesn't "sim" well on a TS driven computerized "Tuning" package / well then it must not be any good . This is a form of "dogma" that most of us live by / that needs some re-examining . For instance, Altecs' highly damped woofers were designed ( empirically ?? ) in the days when tube amps ruled the roost, along with those amps' very low damping factors . The amps are part of the system & and therefore part of the sound ( as designed in the forties ) .

regards <> Earl K