[mmalkie]

I have acquired a set of excellent condition 7B STs that are presently at the Bryston HQ getting a total check over. I will be using Magnepan LRS occasionally and would like to know if I should have them parallel or in series with the switch?? They are 4 ohm but as anyone knows they can be difficult speakers. Thanks

[FullRangeMan]

A few weeks a go an ACer expert fellow member inform us the 4Ω is just nominal they run most of the time in 3Ω.

[opnly bafld]

From Stereophile tests:

The 7B-ST can be configured by back-panel slide switches in "series mode" to provide high-voltage output for speaker loads of 5 to 8 ohms, or into the high-current "parallel mode" configuration to drive loudspeakers of low (1-3 ohm) impedance.

 My measurement of the speaker's impedance magnitude revealed that the LRS behaves more like a 3.33-ohm load, with a minimum value of 2.8 ohms between 400 and 600Hz. However, the electrical phase angle (dotted trace) is very low; the LRS behaves almost like a pure resistance. This loudspeaker will work well with amplifiers that have no problem driving 4-ohm loads.

[mmalkie]

So basically I'm better off in parallel?? Sorry for my lack of knowledge.

[James Tanner]

Hi

Unless the impedance is really low - say around 2 Ohms I recommend the Series.

You can try both but the Maggies have a low impedance but it is very resistive (not capacitive) so I have always found I preferred Series on the Maggies.

james

[mmalkie]

Thanks James...coming from your experience I will use series.
Cheers

[RwVision]

Hello mmalkie and others,

I'm glad that people still use like me the 7B ST's and I would like to just leave here my 2 cents. Good to leave it on the internet.

Beside power/current there are quite some differences in sound between the series and parallel. I'm running Infinity Renaissance 90's, so my first thought and usage for few years was to go only in high current mode. At first, I did not catch the P vs S sound differences and assumed that my speakers need that current. Few months ago I also switched to series - period. I'm glad that James confirmed it.

On my Re90 speakers:

Parallel - In this setup the highs are obviously more forward. The highest frequencies tend to come out from the background. Overall, the sound is more aggressive, a bit faster maybe... Very good for a WOW effect, but you can compare it as to using sliver speaker cables vs copper. My system in the past lacked some details, that's why I preferred this setup. But this could be sometimes tiring and lead to a very thin and harsh highs and even midrange. Bass response seemed to be a little more powerful - but - only in certain areas. The whole bass frequency was not linear and you could hear some "boomines".

Series - The first and very strong impression is that the highs have gone - but after a while you notice that they are just not overpowered, and it leaves the amount to the recording. Along with that, you can hear more natural and free of noise instruments. The cymbals are flowing more like on A class or tube. Now what really convinced me to series is the sweeter midrange and vocals. I suppose that the highs emphasis went down and it allowed the midrange to come out. As the bass response comes I can still hear almost the same speed, but most importantly - linearity. There are no gaps in bass frequencies, all guitar layers tend to come out ad different levels. Something I thought was an issue of my room modes.

All in all, the Re90 are also mostly playing at 4 Ohm, rarely dipping to 3 Ohm above midrange. I've also re-designed their woofer crossover, but that's another story.

That also leads me to the infamous Stereophile review - it definitely sounds as the 7b ST were parallel and the reviewed SST in series (which is mentioned).

Cheers all!
Rafal