2 plus 2, Various, exchange 2+2 for Spectra 44?

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Robert Sabelis2004-02-23 22:21

Hello Andre Szabo, I have 2+2\'s and are considering ugrading to Spectra 44. Is it an upgrade in your opinion? What\'s the difference between the 44 and 4400? Or 66 and 6600 for that matter. Thanks in advance, Robert

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Andy Szabo2004-02-23 22:21

Ah. . .one of my favorite subjects! Both the Acoustat Model 2+2 and the Spectra 44 (or 4400) have four ESL panels per speaker. What sets the models apart is the way the panels are physically arranged, and the interface electronics used to drive the panels.

The 2+2 drives all panel area full range, and has the two columns of panels set at an angle to each other (about 9 degrees). This angle improves horizontal dispersion, and prevents the speaker from being too beamy. However, this approach is a compromise, because the angle is the same for all frequencies. The 2+2 has pretty good stereo imaging, but with considerable room for improvement.

The Spectra 44 has all of the panels mounted in the same plane (i.e. with no angle), but with each panel electrically divided in half and driven by a frequency-contoured signal. All panel area is driven at low frequencies; about half the panel area is driven at mid-frequencies; and only a very narrow strip is driven at high frequencies. The result is a speaker that becomes progressively narrower as frequency increases. Furthermore, a time-delay is introduced for the mid and low frequencies, making for a speaker that is electrically, rather than mechanically curved. Hence the acronym, SPECTRA, or Symmetric Pair Electrically Curved TRAnsducer.

A Spectra speaker is very narrow for high frequencies (where most localization cues are found), but still retains a very large area for mid and low frequency reproduction. The result is superior imaging, while retaining the great bass response and dynamic range expected from such a large ESL.

In addition to providing the frequency contouring and time delay necessary for Spectra operation, the interface electronics offer better saturation resistance and dynamic range as compared to the MK-121 series on the 2+2. All of the improvements learned in the MK-121\'s Medallion Transformers are incorporated in the Spectras.

So, to get to the root of your question, I consider the Spectra 44 to be a significant upgrade as compared to the Model 2+2. The 2+2 is a great speaker (and was Acoustat\'s top seller for many years), but the Spectra 44 is an improvement in all respects. I cannot think of any disadvantages in upgrading to a Spectra 44.

The Spectra 4400 is merely a cosmetic upgrade of the 44, with the addition of wood trim with polished brass inlays along the sides of the frame. Electrically, and sonically, they are the same speaker. The same can be said of the Spectra 66 vs. the 6600.

In comparing the 44 vs. the 66, things get only better, with no compromises. The 66 is the same as the 44 for high frequencies, and therefore offers the same precise imaging (one could not say that in comparing a Model 2+2 to the Model 6). The difference is increased panel area at low frequencies, offering even better bass response and dynamic capability.

There is one additional improvement you may gain, but this depends on the vintage of your 2+2. In the mid-1980\'s, Acoustat introduced a new conductive coating. This much higher resistance coating allowed the speaker to play louder bass signals without the familiar crackling sound of an ESL reaching its limit. Panels with the new coating are identified with a bias wire that is yellow with a red spiral stripe. Panels with the old coating have a bias wire that is solid red or white with a red spiral stripe. The last few years\' production of the MK-121 series used this new coating, as well as all Spectra models.

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