X
X
Back to the top
X
X

GPA

GPA 212-8A
/

Great Plains Audio Model 212-8A

Great Plains Audio designs and manufactures some of the finest loudspeakers in the world. We continue this tradition of excellence with the release of our newest loudspeaker, the Great Plains Audio Model 212-8A. The extension of usable lower frequency limits and the expansion of available dynamic range have placed greater demands on audio monitoring systems. As audio-video facilities are constructed or upgraded to accommodate HDTV, equal attention should be placed on providing a superior acoustic setting. Th e 212-8A will deliver the high definition audio reproduction required for this environment. Recording studios, mastering facilities, and home theater rooms are also......

Read more

GPA 604-8H-III-Rev-02
/ /

Great Plains Audio 604-8H III Rev. 2 Duplex

The Great Plains Audio 604-8H III Rev. 2 is more than just an evolution in the classic series of 604 Duplexes, it's an AUDIO REVELATION! For more than fifty years, there has been one studio monitor loudspeaker that has been the defacto standard by which all others have been measured. Though it has been through various generations, it is still known by the simple model number which graced the very first unit manufactured – 604. The popularity of this outstanding loudspeaker grew until, by the 1970's, 604-based systems were used in more recording studios than all other types combined. It’s......

Read more

Regaussing Woofers
/ / / / / /

Alnico Magnets and Degaussing (Losing their magnetic field)

Alnico magnets, by their nature, are easy to degauss (demagnetize) with drive. They will not change with time and their dependence on temperature is really small – maybe 1% at 100 degrees Fahrenheit. Alnico stability and resistance to back EMF is really good. This is why they make very good sounding magnetic structures. Unfortunately, given a big enough pulse of magnetic energy, they will degauss by up to 3 dB. The sensitivity to degaussing is dependent on the specifics of the magnetic circuit and the length of the coil providing the field. Underhung woofers, midranges, tweeters, and compression drivers do not have sufficient back EMF fields to push the operating point of the structure below the knee. They are essentially stable regardless of input signal. The short-gap, long-coil speakers are the ones that have a problem. A woofer can take a hit of up to 3 dB, if a big enough hit of current takes place. 1.5 dB to 2 dB is more common. The effect does not get better or worse with time, it solely depends on how much current is driven through the coil. The more current, the more field. Once the field is bigger than a certain number, some amount of degaussing occurs. It is permanent (until externally recharged) and will only increase if a larger sustained current hit occurs.

Therefore, if you have a qualifying alnico woofer and you have played it loudly, you have some degaussing. You can have the unit recharged, and it will be fine until you play it again. Exceed the critical level, and it will start degaussing again. If you never do, it won’t ever degauss. Most of these designs trace back to the 50’s and 60’s where 15 – 30 watt tube amps were the rule. They didn’t have the current capability to hurt anything. With the advent of big solid state amps, the current levels went up and the problem started to surface.

Most of the qualifying motors will lose 1 – 1.5 dB, unless they are pummeled. Some of the older 3″ motors with really short magnets will typically be around -3 dB down. They go really easily.

Great Plains Audio can regauss your alnico magnets, if they need it. Regaussing is included free when we replace diaphragms and cones.

Altec Lansing Valencia
/ /

Altec Lansing Valencia: Improving a Classic

The Altec-Lansing Valencia 846B is an American audio classic that inspired the development of the legendary Model 19. It shares many similarities with the newer and larger Model 19. There were two versions of the Valencia: the 846A and 846B. For our testing purposes we chose the 846B due to its impedance, and that it was a tuned port enclosure. We had two goals with our Valencias: 1. Make them perform like a Model 19 and 2. Make them outperform a Model 19. Many Altec Model 19 fans will immediately point-out the differences between these two loudspeaker system, and claim......

Read more

Altec-Lansing-M500-Maestro

The Altec Lansing Model 19-MR3: The Loudspeaker That Never Was

The Altec-Lansing M500 Maestro is a largely lost and forgotten loudspeaker, but it is, perhaps, the best the company ever built. It arrived in the final days of Altec-Lansing, Inc., and production was cut short due to the sale of the company. Why is the M500 Maestro important to us today? It provides the framework for what would have been the replacement for the highly acclaimed Model 19. It has been suggested that the new model would have been called the Model 19MR or Model 19-MR3. So the M500 is of great importance to Altec-Lansing fans around the globe. The......

Read more

Original Altec-Lansing 604
, / / /

Altec-Lansing DUPLEX Speakers

Altec Lansing invented the first DUPLEX® Loudspeaker System in 1941 (some sources say 1943 - we're really not sure). Called the "601", it was of the field-coil type and included a small-format HF compression driver mounted to a 12" low frequency loudspeaker with a hole bored through the pole piece of the woofer which connected to a 2 x 3 multicellular horn. Thus began the famous DUPLEX® series of loudspeakers. In 1944, the first of the world-renown ALTEC "604" series of DUPLEX®Loudspeakers (left) was introduced. It utilized a new, permanent magnetic structure of Alnico V, had a 15" low frequency......

Read more

Altec-Lansing-M500-Maestro
/ /

The Altec-Lansing Model 19-MR3: The Loudspeaker That Never Was

The Altec-Lansing M500 Maestro is a largely lost and forgotten loudspeaker, but it is, perhaps, the best the company ever built. It arrived in the final days of Altec-Lansing, Inc., and production was cut short due to the sale of the company. Why is the M500 Maestro important to us today? It provides the framework for what would have been the replacement for the highly acclaimed Model 19. It has been suggested that the new model would have been called the Model 19MR or Model 19-MR3. So the M500 is of great importance to Altec-Lansing fans around the globe. The......

Read more

Altec Stonehenge III
/

DIY Altec-Lansing Stonehenge III

Perhaps one or the other of you recalls that about two years ago I had two short posts, Björns Altec Stonehenge III replicas as well as the associated. He was lucky to have a beautiful NOS pair of Altec 604-8 G Duplex with AlNiCo magnets, together with related original turnout , which he summarily transplanted into a corresponding test cabinet made from OSB. So now, the adaptation of a corresponding to the original volume, visually far more sedate casing that (almost) without a parallel walls, meets the highest technical standards... Read more at 2A3 Maniac...

Read more

Stevens Dream Altec 604 Loudspeaker
/

Stephæn’s Altec 604 Dream Speaker

Looking back, it's easy to comprehend why I'm a believer in the concept of thought as object - the notion that we bring into our lives that to which we give our attention. That's how I manifested many of the good things that I am fortunate to have this time 'round. But, sometimes I falter and forget that. I can be quick to immediately assume something is out of reach. That's exactly what happened last October when I learned that the speakers from the room I ranked best in show at RMAF 2005 were beyond my modest financial means. I......

Read more