January 2018

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Room measurements: (Basement) 21' long x 12.5' wide x 7.5' high. Whilst the room wasn’t eye candy, acoustic treatments only work well when you employ it large scale. few 1" thick foam won't provide useful improvement. As a result, I focused more on sound quality than aesthetics.

 

Absorption: Consisted of Roxul Safe’n’Sound DIY panels on front and rear walls.  

 

Diffusion: Focused on sides, above and below ear level on middle front and rear. The "temporary" panels were effective from ~450hz to 8khz.

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The front wall was used as an infinite baffle to mount the speakers. The rear section of the front wall was reinforced against 3 other rear walls. This space behind was initially a closet, which I converted into a large speaker enclosure, resulting in the “infinite baffle”. The rear closet area was filled with Safe’n’Sound and some pink fiberglass insulation, which still provided some absorption.

I had roughly 200 pounds of concrete block glued to the rear of the front wall to attenuate vibrations. This actually worked quite well, but I soon discovered that ~200 pounds wasn’t enough, and I ran out of room to add more blocks.

 

Initially, I wasn't thinking vibration would be my biggest bottleneck. Patching solutions used afterwards, by these blocks only achieved so much in keeping the wall rigid. That is the cost of learning.

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All infinite baffle systems (except tweeter of course)

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• Best sound achieved with seating position approximately 38% away from the front wall (and therefore, speaker). 

• The so called “38% rule” was obtained from real trap website. Thanks to Ethan Winer.

• As a result, this qualified the system as "near field"

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All speakers were driven fully active, and only by using balanced connections. I dislike single ended signals. XLR rule when designed properly, has all my amplifiers using fully balanced topology.

Processing the data is an PC Intel I7 with SSD running Windows 10 and JRiver music player is Asio mode.

JRivers use native sampling rate from music library, no point to re-sample at 96khz or 88.2khz.

 

I have a Synology NAS with about 140,000 songs (no mp3’s stored here) connected via Ethernet to the computer, which feeds the Melodious Audio USB/AES bridge connected to the modified Mini DSP 4x10HD crossover/DSP.

 

The modified Mini DSP 4x10HD is running on a dual regulated external linear power supply. The external PSU has 210,000uf of capacitance, which is more than most commercial 200W amplifiers! The end result was the 4x10HD sounding nothing like the original, with an easy sound and delivering tremendous dynamics.

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There is only a single capacitor in the entire signal chain, inside the Mini DSP 4x10HD, from the DAC chip to the analog opamp stage. Unfortunately, it’s was impossible to remove the capacitor as it eliminated a ~2.5Vdc offset from the DAC.

 

Every amplifier is DC coupled. I didn’t use a "protection capacitor" on any speaker. On the tweeter, I installed a small 0.5A inline fast blow fuse, as unlike capacitors, fusing doesn’t induce a phase shift and still somehow protects the delicate tweeter voice coil.

 

Amplifier used:

• Bass and Front Subs. Krell TAS (fairly modified, using 4 amplifiers in the 5 amplifier chassis, and running on a dedicated 240Vac line)

• Rear Subs. DIY mosfet 500W/channel built inside a recycled Parasound A21 chassis. ( Run on 240Vac line)

• Midrange. Krell 300CX (modified fed by a separate dedicated 240Vac line)

• Treble. 12W monoblock DIY kit based on the LME49600 and using AD797 (120v). Those amps are hard to beat.

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All drivers are digitally time aligned and compensated for the room at the listening position. I’ll eventually upgrade the DSP, but the modded MINI DSP is still very good despite the manageable background hiss it produces.

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Speakers used:

• Tweeter: 3.5Khz-40Khz (28mm Transducer labs Beryllium dome)

• Midrange: 260hz-3.5khz (100db efficient 6" Pro Audio midrange, the Max Fidelity PR65Neo, used to be the ScanSpeak illuminator 12mu8731)

• Woofer: 260hz-35hz (scan speak illuminator sandwich cone 13")

• Subwoofer: 35hz-18hz (4x Heavy duty 18" from Mach 5 located in Winnipeg, Canada)

Wires:

• DIY high speed USB cable (solid silver core conductor and Teflon sleeve built as 2 separate cables inspired by the LH light speed USB cable)

• AES/EBU Mogami digital cable (can’t recall the model)

• All XLR cables are solid core silver into Teflon sleeve, except the rear amp feeding the rear 18", which used a shielded Mogami balanced cable.

• Tweeter: Solid core silver and Teflon sleeve

• Midrange. Duelund 2.0

• Woofer. Solid core silver and Teflon sleeve

• Subwoofer: Solid core silver plated cooper and Teflon sleeve

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Possible future components:

• DIY Plasma tweeter (initial project ordered for testing)

• Dual 15" woofer system to replace the single 13'' revelator, which was previously purchased but needs to be auditioned.

• Horn midrange. I’m a bit “iffy” on this one. Purchased a JMLC horn and will need to do long term auditioning.