Video Asylum

Posted by Timbo in OZ (A) on April 28, 2002 at 02:23:39

Hi all,

As this is a request for advice and would need a bit of reading of what is below etc, thankyou in advance.

I am moving to add surround to my tube stereo system. This is not for
HT purposes. The HT is in the family room kitchen part of the house.

NB - most of my listening is and will be to stereo sources, and for a long time to come.

Yes, I do have one or two Nimbus sound-field mike records using the Schoeps, and some EMI SQ or QS records. I remember when Gerzon was writing his ideas up a long time back.

For some more info see 'inmates systems' under 'Timbo in OZ'. The room is a smallish L-shaped lounge and dining room with an open room divider cum bookshelf - leaving the larger area as the lounge and listening area. The longest dimension, diagonally across the L is 35 feet. Wood frame brick veneer house, so fairly lossy at ELF and mid bass.

I have a second hand Luxman F-105 surround unit serviced with one of the tape loops converted - to a jumpered L&R pair - electrically in front of the built in power amps.

I am a music lover first, a one time cathedral chorister, and value
clarity and depth of image, along with dynamics. Classical - specially
HIP/authentic and Jazz, blues, R&B rock and pop.

I wanted to combine two ideas which have always struck me as essential
features for my second foray into surround.

So - here is what I want to do, the questions follow after.

Objective 1.

Keep the main L and R feed from the tube pre pure and unprocessed - the pre would remain the main control unit - to my main pair of speakers. The volume control can feed 4 L&R out, 2 for the two stereo biamped power amps, one for a sub, and a spare pair for surround processing.

The main spkr pair are spheres and give very clear and 'quiet' stereo. I do not want to lose this.

Objective 2.

Feed delayed rear signals (eg L-R ie Dolby surround low-pass filtered and Dolby NR'd, or the other options the F-105 provides) to several smallish wedge* speaker units mounted on the floor but firing up its adjacent wall area.

I read about this idea in Audio Amateur a long time ago, the report
said that adding adj. delay makes this idea work even better.

* The wedge shapes the article recommended is to aim the sound up the walls and increase the delay and diffusion of the sources
passively. The driver mounted on a baffle at 60 degrees to the wall, or 30 from horizontal.

Using several such speakers / sources rather than just two adds diffusion from distributing them along the side walls instead of just the rear. Front wall too? see below.

The amps available for this duty include the two 25 watters in the F-105 and the two stereo tubed (PP 6BM8s-ECL82 10 watts) channels of a
restored/rebuilt Kenwood tube receiver. It is currently used just as a tuner, with the amps B+ (HT) off.

So, I build 5 new wedge shaped boxes with one Fostex FE103, a small but good full range driver - I have collected 5 of these. I know a good RC Z-rise Eq network to go across their terminals.

QUESTIONS -
Q1. Ported (QB3) boxes or simple sealed ones for the little FE103's?

Q2. I wonder if adding a coil - to pull down the upper mids - as another article on the FE103 driver suggests, is really worth it!?

Q3. Is it best to distribute the wedges only to the sides and rear and not the front wall? OR

Q4A. one (or more) of these at the 'front wall' too? but still at the
floor/ aimed up the wall? One each to the sides, and one to the rear?

Q4B. Use my extant pair of rectangular FE103 boxes (Lyrebirds) above and to the rear of the main front pr - as with Yamahas ideas?

Q5. Use image enhancement at the front with a second (smaller) pair of
spheres (one Coral Flat 5 FR driver) run off the treble amp.

Q6. Whatever distribution I choose for the smaller wedges and the
Lyrebirds / spheres ......

What about adding two larger enclosure pairs giving a range
of differing bass roll-offs? I could fairly easily achieve this as I
have two 10 inch, and two 6 inch, paper twin cones and enough >10 inch
diameter form-work tubing to build two pairs. I would slice the tubes at angle of 30 degrees, just as with the little wedge boxes.

Q5. Even if I did not do the bigger boxes, would I still get an improvement in mid and upper bass level. I remember this as a commonly reported consequence of delayed derived surround.

Q6. The LUXMAN F-105 itself. Do any of you know it? I have both the the user manual and the service manual.

Why am I asking?

'Cos it is remote controlled and that still works. .......

I wonder if the chips used for the main stereo in and out path, including the volume control are good enough (transparent) for me to use it as my main control centre for line level?
OR
would the chip sockets/circuit board allow an upgrade? I would still use the tube pre for RIAA vinyl amplification.

Warmest,
Timbo

in anticipation