2008 "Atmosphere" Compact

updated September 2008

I have been listening to speakers long enough to realise that the enclosure is everything! You can make really cheap parts sound exceptional if you have a quality container as long as the rest of your system has a decent amplifier and source.

Last weekend Jane arrived back from the Saturday morning garage sales sporting a couple of very heavy marble occasional tables.($5 each)Two trianglar sections that link to form a table. We decided quite quickly that they were not going to work in our living area so they seemed destined for the deck.

Interested in the material, their weight and shape, I thought......what about......Hmmmm........maybe..... a pair of speakers.

Having plenty of speaker bits lying around and some spare MDF, these turned out to be a very cheap project.

Jane nodded.....yes dear!

RIGHT ATMOSPHERE, resting on my Fidelio BL horn, its mass also helps to firmly seat the Fidelio into the carpet

Some technical details;

The copper coloured driver is one of a new series of RESPONSE PRECISION drivers available at JAYCAR electronics. The following information was taken from their website

4" High-End Full RANGE Driver
The latest in our range of high-end drivers for home theatre and multimedia applications. They feature the last word in speaker materials technology: anodised magnesium/aluminium alloy diaphragms, Kapton voice coils and shielded neodymium magnets

Specifications:
• Nominal impedance: 8 ohms
• Power nominal: 25WRMS
• Sensitivity: 85dB (2.83V at 1m)
• Qms: 3.91
• Qes: 0.63
• Qts: 0.52
• Vas: 4.5l
• Fs: 56Hz
•Tuning frequency: 50Hz

WEBLINK TO JAYCAR

Considering the volume requirements and the size of my cabinet I decided to incorporate a 5in ABR. I had a pair of eighties Technics ABRs taken from the model SB-4

Obviously bracing is not required here. Internally I packed the inside with 6 wool and 6 foam triangles.

Marble is not an easy material to work with so I decided to keep things simple. Two small drills holes at the rear for some cable, I spent some time smoothing the front edge with a sanding block and used iso-propyl alcohol to clean mating surfaces before gluing (araldite) the baffle. The boxes were left for at least 7 days before I fixed the drivers

The MDF has been treated with Danish Oil. The slight orange tinge works well with the copper colour

I am using them with my Passion and Dave Goodman MOSFET power amp and a Luxman d-105u tube hybrid CD player

a closer look at that copper coloured magnesium/aluminium alloy cone. Very attractive glow at night! The grey ABR helps to fill out the low end

How do they sound?

Completely out of the box!

These are the best imaging speakers I have ever made, no exception. Listening to "Amused to Death" by Roger Waters you can easily focus on the individual zones of sound. Its so distinct! Sounds seem to be available through 360 degrees.

You are simply not aware of the box!

Its an infinite baffle that sounds like an open baffle, but has the advantage of small size and decent bass. Excellent bass considering this is a 4in driver.

The top end performance easily matches my Fostex FE 206, better in this size enclosure

They are still running in so I havent pushed them too hard.

They need a powerful amp to reach decent SPLs at least with my chosen passive pre amp

I now know that MARBLE is well worth investigating.