Differences from the original Linus Array.
Although the design is based on the Linus Array, I have made a number of modifications to the original design
to match my different goals, higher budget, and satisfy my personal preferences and ideas about speaker building. During the
same period Jim Griffin was designing the Linus II. We were coresponding during some phases, and much input came from Jim
Griffin himself so my array and the Linus II have some strong similarities.
Changes I made to the original Linus Arrays:
Tweeter line is lengthened by 2 tweeters
This is to increase the vertical window of the tweeter line so it extends from below the seating position
to above the standing position. The tweeters do not radiate much sound vertically, so if your ear moves above or below the
tweeter line, you get a noticeable drop-off of the highs. The highs now sound even in any normal listening position. There
is a drop-off if you are laying down or if you place your ear somewhat above 6 feet 2inches, as might be the case for someone
6 feet 8 inches tall. (I am 5 feet 8inches myself.) Jim Griffin also made this exact change in his Linus II design.
Vifa PL14 woofers
This is a personal choice. I feel the MCM-1855 woofers are pretty good woofers, especially for the price.
I purchased a pair from Rick Craig, and they are rather nice sounding, and have exceptional bass for a small speaker. They
are very tame for an aluminum woofer, but there is still just a bit of harshness to my ear. I am very selective regarding
the sound of the midrange, and I find I do not like most midranges out there. I wanted a bit more detail, a more warm, sweet
and neutral sound. Several of the members purchased pairs of 5inch midwoofers to audition, building cabinets for each driver.
After listening to 7 different 5 inch midwoofers we all concluded we liked the Vifa PL-14. However it was one of the more
expensive drivers we looked at. The PL-14 are very low distortion, neutral, and detailed.
I checked out the following drivers all 5"-5 1/4":
GR-130, clean, sweet, runners up, a bit colored, rim too large, $25.
MCM 55-1855, good, very cheap, slight metal sound, not a lot of detail, $12.
Vifa MG-14, bit of harsh breakup, could be tamed. I didn't really like the sound. $45 dollars.
Hi-Vi 5g- Pretty, expensive, rings like crazy, I don't think it could be tamed. Avoid this driver. $90.
Peerless HDS-85488- Not too bad, but not a of detail either $55.
Vifa P-13, an old classic. Pretty good, but inferior to the PL-14 in my honest opinion. NO bass at all.
$35.
9 woofers instead of 12
The number of woofers is a bit of a compromise. It is a personal aesthetic choice on my part, to have the
tweeter line, and the woofer line of similar length. Also there is a consideration of the end size of the cabinet, since the
PL-14s require more volume than the MCMs. However the Vifa's are much more efficient than the MCM's so that equals out. There
was also an economic consideration since the price was exceeding my budget.
Jim Griffin has used 10 Vifa TC14 drivers in his Linus II design.
Cost
More tweeters and more expensive woofers, high quality crossover parts, and mahogany veneer. I place the
end cost at about $1800.00
Cabinet construction
I tried to work a lot of details in the cabinet construction to try to optimize the effect of the cabinet
on the sound.
The cabinet is a single chamber as opposed to 9 separate chambers. This decision was made to make the most
efficient use of internal volume, since there is 18 inches or so on the bottom that does not have woofers. I think the ideal
would be 1 woofer per chamber, but chose against it due to added size.
The following step were taken to reduce cabinet wall vibration:
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The cabinet outer walls are 1 inch mdf.
It is very heavily braced with 3/4 inch mdf. With a brace between each woofer.
A 3/4 inch strip of mdf was used as a backing for the ribbon line to provide stiffness, and a better air
seal than separate ribbon holes.
There is a 1/4 inch hardboard piece attached to all cabinet wall surfaces with flexible silicon chaulk.
This a constrained vibration layer to dampen any wall vibrations.
To reduce standing waves within the cabinet the following steps were taken:
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Flexible silicon caulk was applied to most internal surfaces to act as damping and an adhesive for the foam.
1/2 inch open celled foam was applied to the interior surfaces. (Ester open celled foam in 2lb density,
this is the same type of foam that is used as acoustic foam, but if purchased generically it can be much cheaper. In fact
some dealers have 2 price lists, one for regular foam and a SPECIAL price for acoustic applications.)
Miraflex fiberglass insulation was then attached in varying thickness', depending on the amount of clearance
available.
Where there were open areas that did not have a direct path to the port, such as the area behind the ribbon
line,fiberglass insulation was placed in the area to fill the void.
Other steps that were taken to optimize the cabinet for sound
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To reduce edge diffraction, the vertical edges were rounded over with a 1.5 inch radius.
To reduce any effect of drivers protruding on the baffle face all drivers were flush mounted.
The rear of the driver holes were rounded over with a 3/4 inch radius, to lessen interference with the backwave,
and reduce reflection from the area where the driver is mounted.
All internal edges were rounded over, including the braces, and the ribbon backing.
To eliminate any direct interaction of the woofers with the adjacent woofer the brace between woofers was
extended from the front wall about 5 inches back.
The cabinets are dead sounding without apparent vibration or resonance. It is like tapping on concrete.
When the speaker is playing loudly if you place your ear flat up against the sides you can just barely make
out some sound being transmitted through the wall, this would be inaudible at any distance.
However if you place your ear against the back of the cabinet, you can pretty clearly hear the backwave
from the drivers. This is due to an error in my design of the bracing. You will notice I cut a single hole in the back of
the brace. This leaves the sides completely braced, however fails to sufficently brace the center of the back wall of the
cabinet. If I were to do it again I would cut 2 holes in the brace and leave center bracing from front to back. I don't feel
the amount of vibration on the back wall has a detectable influence on the sound at all, since the amount of sound vibration
is still very small (my ear is against the back of the cabinet.). However the lesson for me is even with a 1 inch thick wall,
center bracing has a significant affect on the vibration being transmitted from the drivers.
The cabinets are covered in a mahogany veneer, extra thick .022mm.
Attached with Weldwood contact cement.
They are stained with a mixture of minwax red oak and red mahogany liquid stain. 2 parts red oak to 1 part
red mahogany.
