NGAS Altec M500 Maestro Update

[Lansing4412]

The M500's restoration is finished and they're tri-amped at 1.1 kHz and 7.5 kHz. While they're sorta-kinda-maybe usable up to 20 kHz according to Altec, they start to roll off just over 12 kHz. So an Eminence ASD-1001 HF driver with an Eminence APT-200S bi-radial horn were added to make the system go all the way up 20 kHz.

Initial listening tests are very positive. The MR994A horn and 909-8A combination present a wide soundstage and very smooth life-like sound. The 3154 woofer is a wolf in sheep's clothing. It's usable from 45 Hz to 1.3 kHz (1.5 KHz with help from a PEQ). Yea, you can get it to do the 2 kHz spec but since the horn can be crossed as low as 500 Hz, it really isn't necessary.

This speaker system shows a lot of promise.

[RonSSS]

There goes the eBay prices on 3154's and MR994's
😊

[GM]

they start to roll off just over 12 kHz.

All these old horn designs requires some form of CD horn EQ to maximize their HF extension.

GM

[mah]

After a bit of cross-referencing of EV,1996, Altec Lansing repair parts list pages I came up with cone number 18-03-025127 for the 3154 speaker.

See here: Altec 3154 Low Frequency Loud Speaker~Pro Series~Sub Woofer~15" Driver~ 027569 | eBay


Go to the ALTEC LANSING RECONE KITS PARTS LIST/FIXTURES LIST page, last page, here: Dropbox - ALTEC PRO PDF'S

The individual re-cone part numbers are shown under R/K# 85274XX.

Happy hunting.

[Lansing4412]

All these old horn designs requires some form of CD horn EQ to maximize their HF extension.

GM

That's correct, CD (Constant Directivity) horns do require EQ correction. The M500's do work well with just CD equalization, but the aim of the project is to see if an old Altec design could be utilized for critical monitoring like a new JBL M2. To make things fair the M500 is getting all the benefits of digital crossovers and correction that are utilized by the modern JBL's.

Just today I was able to get some truly amazing results from the Altecs. At this point they can already easily compete with many world class studio monitors.

[GM]

OK, that wasn't made clear in your initial post, though given enough hi-def frequency shaping EQ and we don't need to start with expensive speakers, so hardly surprising the results you're getting.

Really, you're mainly proven what we already known all along, that other than advancing materials, manufacturing technology there's been virtually no improvement in speaker component design since the early 1930s and in some ways we've gone backwards to keep cost down, though the newest neodymium drivers have broken through the field coil Vs permanent magnet barrier, so I need no longer pine for the good ol' days of audio.

Regardless, thanks for sharing, no such thing as too much knowledge!

GM

[Lansing4412]

Really, you're mainly proven what we already known all along, that other than advancing materials, manufacturing technology there's been virtually no improvement in speaker component design since the early 1930s and in some ways we've gone backwards to keep cost down...GM

I would agree that there's been cost cutting from some manufacturers that have been a step backwards. However, I disagree that component design hasn't improved over the years. Stronger diaphragms have been developed for power handling. Improved phase plug designs for higher frequency response. And, improved horn designs for more equal dispersion of sound. For example the new acoustic lenses work much better than what came before them. In A/B testing of the Altec 511 vs. the MR994A, even with PEQ correction, the 511 was not the equal of the MR994A. That's not to say that the 511 is a bad horn, just that the more modern MR994A is an improvement in design and performance.

[Phil-G]

I'm not sure the MR994A is the "modern" design GM refers to. And being a 30+ years old design its not striking me as all that modern either.
Its fraternal twin has a better coverage pattern. fwiw

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I'm not sure the MR994A is the "modern" design GM refers to. And being a 30+ years old design its not striking me as all that modern either.
Its fraternal twin has a better coverage pattern. fwiw

[GM]

In A/B testing of the Altec 511 vs. the MR994A, even with PEQ correction, the 511 was not the equal of the MR994A. That's not to say that the 511 is a bad horn, just that the more modern MR994A is an improvement in design and performance.

No surprise there, the 511 was designed for a cinema screen's ~3 kHz ~flat BW limit whereas the MR was designed to EQ 'punch through' the screen to meet THX standards. Limit the two to the lower limit and it wouldn't surprise me if the 511 was best overall since the MR by design has a higher throat distortion.

From a purely SQ POV, Harry Olson's 1930s conical horns are a [major IMO] step up with Dr. Geddes's being the current SOTA horn/WG.

Stronger diaphragms = materials improvement

Improved phase plug designs = manufacturing improvement

Improved horn designs are just adaptations to the market's changing needs, but there's no new technology per se unless you consider DSL's Synergy concept, which I don't since its and the TH's roots are in Jensen's Transflex 'sub' [aka tapped TL, TTL nowadays].

Anyway, the pioneers proved that they understood the physics of sound reproduction to a fare-thee-well, literally 'writing the book' as they went along, making these 'improvements' all a function of computer aided materials, manufacturing advancements, so we'll have to agree to disagree and let the 'gentle reader' come to their own conclusions.

GM

PS: I like the way Tom Danley once responded to a similar thread, bemoaning that 'the ancients keep stealing all my inventions'.