Linkwitz Pluto+ for the bedroom | Virtual Listening Room

System

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Pluto cross-over + amps (1 channel)

Pluto cross-over + amps (1 channel)

Pluto+ cross-over (1 channel)

Pluto+ cross-over (1 channel)

Pluto+ sub-woofers

Pluto+ sub-woofers

Description

A small actively tri-amplified system for music and movies in our bedroom.

Very natural with tight bass. The placement gives some warmth, eliminates image depth, and hurts image focus. To my surprise they don't suffer as much as other speakers in the same location, perhaps because the front wall first reflections are so close in spectra to the direct sound that human hearing correctly identifies and suppresses the reflections.

Design by Siegfried Linkwitz; sub-woofer aesthetics by me; construction in two garages and a high rise apartment across three moves.

Polar response is exceptionally uniform with the midrange driver being acoustically small and close to the tweeter at its 1KHz point.

The mid-range enclosures are cylindrical, making them free of panel resonances and sound emissions since the stress is in tension. Damped transmission lines are used with 99% of the mid-range back wave absorbed.

The midrange and tweeter amps run off a modest transformer and heat sinks but 30V rails, gaining a lot of dynamic range for music although they wouldn't rate a lot of Watts on FTC tests with sine waves. Bridged LM3886 chip-amps are used on the mid-range.

The woofers are equalized with a Linkwitz Transform for a second order roll-off at 20Hz with Q=.5, making them -3dB at 30Hz and -6dB at 20Hz anechoic or ground-plane.

Some time I'll get around to applying a shelving filter for the front-wall gain and compensating for low frequency room gain.

Components Toggle details

- Samsung BD-P2500
Blue-ray, CDs, DVDs
- Samsung HP-T5054
50" plasma
- Linkwitz Labs Pluto
Omni design with drivers in damped transmission lines (40dB return loss on the mid-bass) with active bi-amplification

Build from plans like me
http://www.linkwitzlab.com/Pluto/intro.htm

for approximately $700 or buy assembled
http://www.linkwitzlab.com/pluto-wa_2.htm
- Adcom GFA-545 mkII
Pluto+ sub-woofer amplifier. Affordable and even works into 2.5 Ohm loads.
- Linkwitz Labs Pluto+
SAF-friendly .5 cubic foot design with Linkwitz transform producing second order roll-off Qp=.5 Fp=20Hz.

LR4 acoustic cross-over to Plutos

Build from plans
http://www.linkwitzlab.com/Pluto/subwoofer.htm

for approximately $575 a pair plus your favorite two channel amplifier or buy assembled
http://www.linkwitzlab.com/pluto-wa_2.htm I built my pair from Baltic birch plywood with yellow birch lumber framing the top and bottom with the bottom edging continuing into feet. The finish is super blonde shellac rubbed out to a satin finish with #0000 synthetic steel wool. Construction is per Siegfried's blueprints with an added pair of intersecting braces, counter-sunk drivers, and height increased 1/4" to accommodate the displacement. The corner miter joints were made with clear epoxy which shows the darkness inside the box and aren't as visible in person. The tops actually have attractive grain with decent chatoyance which doesn't show up in the video camera/low-light picture.

Comments 3

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Owner

1) The Plutos have limited output compared to Orion. While no worse than any other 6" 2-way I wasn't happy until I added the Pluto+ sub-woofers which give a lot more head-room. The Seas driver used in current Plutos adds about 6dB of head-room and does better although equalization is extended to 40Hz so that may be somewhat content dependent.

2) If you want optimum performance from freestanding speakers the optimum placement is the greater of 4-5' off walls and half the distance to the listener. That said speakers with more uniform polar response work better when in sub-optimal situations. I have the Plutos about as close as they can get to bedroom wall and they suffer less there than conventional speakers.

3) There are "seeking audition" threads on the orion user's group forum http://orion.quicksytes.com. People can probably find nearby Orion/Pluto builders to hear a pair.

drew_eckhardt March 19, 2011 02:49

love to know a few things about the pluto... does it get loud enough for music that thumps a bit? how does it compare to the orion (especially on the low end). you might be one of a few people in the world with both systems. I've heard some people say the placement of the speakers wasn't as important as stated by the designer, but you would know best. Thanks for any info!

yovoy June 28, 2010 06:00

I admire your resolution, perseverance and craftsmanship in completing those Plutos... They probably sound very good, too, I expect.
I've been mulling over the Orions for some time now... and still mulling.

gregm May 11, 2009 08:35

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