Shims to make Duetta Sigs vertical

[EldRick]

I've started to build my new stands. I had been planning to use the OEM stands bolted on top of a 3" tall aluminum box-section about 18" long to raise the speakers. I was planning to make them vertical with an adjustable point at the back end, but I've got wood floors, so I'd need to get a couple of stone slabs to protect the floor and distribute the load over more than just one board.

This morning it occurred to me that there is an easier way - leave the bottom of the aluminum risers flat on the floor, and use tapered shims between the OEM stand and the back of the speaker to remove the backward lean.

Since the rake of Duetta Sigs is known (and measured - I verified it) to be 2.5-degrees, it's easy enough to spec a tapered shim - about 10" long, 1-3/4" wide and a sixteenth or so thick at the thin end. It would wind up about 3/8" thick at the thick end and require longer attachment screws, but should be simple to program and manufacture on a CNC mill.

I've sent an RFQ to a local shop to see if this would be cost-effective.

Would anyone else interested if the price for these shims is reasonable? The more parts, the lower the cost per part...

[artm]

What am I missing here? Is the original design flawed by having a rake on these? Are you using Graz ribbons that require no rake?

Curious but confused...

[EldRick]

I've discussed this with Graz and with Rich, and a number of others have described considerable improvements from having the speakers a) vertical and b) raising them a bit (3"-12") to get the center of the ribbons at ear height or higher.

Vertical position allows the reflected wave from the wall in back of the speakers to do a better job of matching phase and blending with the front wave in the mid and lower ranges - it's more coherent.

In addition, the vertical imaging height from ribbons is at the center of the ribbons and perpendicular to the line of sight to the center of the ribbon, because the sound from both ends of the ribbon reaches the ear at the same time. This also determines whether the sound sound seems to come from below your ears or above them, depending on height.

The net is better resolution of detail and a more realistic portrayal (unless you prefer to sit in the nose-bleed seats at a concert, where the sound comes from a source below you).

And then there is reduced interaction with the reflected wave from the floor, which is lessened by having the speaker farther from the floor = less interference with both high and low frequencies.

You can easily verify the vertical part of this - notice the difference in sound between standing vs. sitting in a low chair. Then toe the speakers in an inch or two - that gives a similar effect as having the speakers leaning back, and smears the imaging and definition quite a bit.

Have a look at the comments on stands in the recent thread entitled "Building A Better Apogee Duetta!!!"

The original design was perhaps constrained by considerations of WAF and fear of having Apogees falling forward and killing pets and small children...

[Graz]

Rick's speakers were my original first planar Apogee's, later fitted with my ribbons when the old ones expired. The requirements for these ribbons are absolutely identical to those they were fitted with in the late 1980's, and the foil for the ribbons from the original mill = the only difference is tolerance over the original. The xover is stock standard, the only modification being the replacement of the old terminals with full copper sota Bocchino ones. Nice to see them in pictures - I have spent many happy hours around them...

Rake. Setting a speaker upright or angle depends on it's height and distance relative to the listener. The Duettas factory rake was 2.5-3 degrees from new, and the settings optimal for floor placement and a couch listener. To really get the benefits of vertical placement the speakers need to be actually raised from the floor by 12-16"and this has been best achieved in an after-market variable placement stand by forum member Toine imho. His stand continued the thickness and theme of the Duetta case, with a large floor piece. They were made from slabs of thick MDF, and had brackets that went up the back of the speakers. Something like this, with longer extensions would be perfect. Toine posted measurements and designs of these originally-








Take care - Graz

[EldRick]

That's a nice design. If I had a table saw, I'd copy it.

I intend to be be conservative with this - I don't want to irreparably drill holes in the speakers, and I'd like to be able to supply the next owner with the original stands, so I want to retain them as supplied, while using them as a removable part of this stand experiment. I've always hated the flimsy OEM feet, as they seem to me to be far too prone to falling forward, so the new stand-bases will protrude 2" farther backward, and 5" farther forward than the Apogee stands, and will be heavily weighted.

BTW, these days Graz's pride and joy have new capacitors, potted coils and an internal brace that he must have forgotten installing. I've got new KLM3 ribbons and foil returns on the shelf, and finally found someone skilled to assist with the transplant, so that will finally happen in the next few weeks.

Just for a teaser, here's a blurrycam shot of the parts that I just cut, sitting as they will be assembled. The stock stands will be bolted on top of the (black-painted) base, with the back end butted up to the cross-piece.

[Forrest]

. . . and this has been best achieved in an after-market variable placement stand by forum member Toine imho.

. . . and I agree. I couldn't imagine a stand any nicer. I really like that design, but where do you find 30mm or even 1" MDF?

Rick, it looks like you're on the way and your idea looks like it going to turn out well. Keep us posted.

[ThingMan]

. . . and this has been best achieved in an after-market variable placement stand by forum member Toine imho.

. . . and I agree. I couldn't imagine a stand any nicer. I really like that design, but where do you find 30mm or even 1" MDF?

In Holland 30mm MDF can and will be ordered by any sawmill that does custom jobs.

But even when not available, one could glue two layers together, producing the required thickness...