Altec 606 cabinets and which 604 to use

[HeathKitPat]

Hi all, fairly new to the board but an Altec lover. I have a (few) questions about a pair of Altec 606 cabinets I now own. I understand that these cabinets were originally designed for use with the 604C. I only have one 604C now and understand how hard it can be to get a good second one. It seems there are many more "E's" available and my thought was to perhaps either find a pair of E's or have a look to see if I can find a C that needs repair and have it and the one I have now reconed using good GPA parts/service to essentially have a pair of E's in terms of performance. I believe the LF resonance of an E is 25hz, I'm not sure of the LF resonance of the C is and what the effective resonant loading of the 606 cabinet is. If I put a pair of 604e's in the 606 cabinet what will I have to do to load them properly to the LF resonance of the E (if it's different than the C and I believe it is.

Thanks,
Pat

[604man]

This page lists the 604-C as 40 hz free air resonance go here http://www.lansingheritage.org/image...ign/page03.jpg
Lots of good design data on the Lansing Heritage site.........GC

[cradeldorf]

My C's have a 53 hz Resonant Frequency. If you go with E's you won't need a subwoofer. You can tune a cab using the impedance measurement method although there will be some argument as to the proper tuning. I'll add my thought now, Tune them to the Resonant frequency of the speakers you choose.

[604man]

Was 53hz in the cabinet or in free air ?? I see other specifications of 38hz in free air.
...............GC

[cradeldorf]

53hz was free air. And I have seen 604E's all over the place even in Altecs literature. I've seen them as 25hz, 27hz, 30hz and so on. All I can say is both of my C's measured 53hz in free air using DATS to measure them. That's why I suggest just tuning the cabs to the speakers using the impedance method because then no matter what the Fs of the speaker is, they're tuned to the cabinet properly. If indeed you think the cabinet should be tuned to Fs.

[GM]

All I can say is both of my C's measured 53hz in free air using DATS to measure them.

This is way too high! OEM was ~40 Hz max or they didn't ship, at least this was the official marketing 'line'. Are they original?

GM

[GM]

FWIW, the 606 dates from at least the end of WWII and I was told by someone who was around at the time that it dates to the original 601 to ~mimic the in room presentation of RCA?s premium studio monitor corner horn, but never seen any proof.

Regardless, the norm was to tune the cab to the driver's Fs to maximize power transfer in the LF and you get whatever in room performance you get, which IME is too 'boomy' if there's any significant LF in the signal below ~45-60 Hz, but this only applies if you're driving it with a period correct high output impedance.

If not, then it's generally best overall to tune a BR for best blend in room at the listening position, which can be from well above, to well below, the driver's Fs, so pretty much any Fs below ~60 Hz is fine in a corner cab where there's likely going to be enough gain to offset the driver?s rapidly falling response below Fs.

Anyway, if yours are utility cabs, then tuning them is a simple exercise, but salon cabs potentially require a lot of removing the back plate to change the vent area, so a really good gasket seal is required each time otherwise it will be tuned too high compared to what theory predicts.

In short, buy whatever driver model suits you, i.e. one ideally needs a Fs that?s at, or below, the lowest frequency it?s likely to ?feel? at any appreciable SPL, then tune as required whatever type cab[s] one has/builds.

This is the main reason for DIYing speakers, one doesn?t have to accept some ?best? compromise that will work merely OK in a wide variety of apps, but truly optimized for only a few at most without some form of EQ, and often lots of it if one chooses to use acoustical solutions for acoustical problems; though at the rate DSP room, etc., correction is improving, relatively soon we may be able to do it all electronically at a very competitive price.

GM