Hot Rod 1+1s

I thought Hot Rod describes my speakers configuration fairly accurately. The idea is to reduce the speaker to its rawist state so that nothing exists other than to perform the task intended in its purist form and executed as best as I am able or can afford.

October 14th 2002.
I'm revisiting some of the component recommendations on this page - specifically the use of replacement resistors instead of the HF control, the HF capacitors (LV side), multiplier parts and a few others.

Frame

Copper tube frame description and pictures here.

Audio Interface

Circuit as here.

 

Circuit Identifier	Component	Manufacturer
R1	6R 50W rheostat	Ohmite or original
R2, 3	4 off 25k ohm 10W 1% WW	Ohmite 80 Series
R4	1 ohm 10W 1% WW These can get hot when playing very loud.	North
C1, C2, C3	200uF Zen 100V	North
C4, C5	0.01uF PP film/foil, 5000V	SEC

Power Supply

Circuit as here.

 

Circuit Identifier	Component	Manufacturer
C6 - C10	3300pF 2000V	BC Components, 356-3406 Farnell
D1 - D5	originals	Acoustat
R5	original	Acoustat

Check here for help in sourcing parts.

Measurements

I was lucky to have a friend over that likes to measure things. This is what Jack Bouska measured. Click diagrams to enlarge.

Current room is 14'9"L x 11'8"W x8'7"H. There are 6 DIY "CornerTune" type cushions in the various corners and 4 DIY "RoomTune" type devices behind/between the speakers to control the reverb field. As there is no furniture, there are two single bed mattresses at the first reflection points to break up slap echo and a duvet over the window to reduce it's effects (bass leakage and high end emphasis/blurring). The speakers are about 4' from the rear wall and 2'6" from the side walls. The listening chair is about 3' in front of the rear wall with damping behind the head to stop rear wall reflections hitting the ear. Overall the room is live without being overly damped. We moved things around a bit but it didn't make things better (the measurements) from that position determined by ear.

The low frequencies suffer from room modes and overly long reverb time. From about 100Hz up the RT is about 0.3 to 0.4s - good for a listening room however below that the RT gets up to about 0.6s or more and so needs treating. A major room mode at 38Hz needs taming. Having only been in this room for a week before the measurements and with no bass treatment, it's not too surprising to see the results as they are. Very pleasing is the lack of broad energy storage in the waterfall plots and the superb impulse response.

Of interest is the room mode analysis and it's match with bumpy bass response. I will be trying to remedy this with various acoustic devices.

Frequency Response	2mS Impulse
Waterfall - Low Frequency note: time axis = 300mS. Level 50 to 100dB< /p >< /p >	Waterfall - High Frequency note: time axis = 1.5mS Level 70 to 100dB< /p >< /p >
Room Modal Analysis.