DIY Waveguide loudspeaker kit

[gedlee]

Noah

Very perceptive as I have thought about just that. Put the center speaker NOT on stands and face it upward. However, there are lobs in the vertical plane and this could be an issue. But I could do a crossover that optimized the vertcal plane down at 15 degrees or so. I have to think some more, do some simulations and then try some things.

I just can't see why you need the small gain provided by the screen with the lumin power available with a modern projector. I tone down the light output of my projector and I use a dull bedsheet with negative gain, otherwise its too bright. I do have a very dark room, but it seems to me that there are options that would allow you to use the bedsheet (far far better than an "acoustically transparent (NOT!)" screen).

[TRADERXFAN]

As an idea for the center solution...
Does the vertical off axis response characteristics match the horizontal response characteristics? If so I would say tilt it back for the center to be at the specified 22.5deg tilt.relative to listening position.
If not, I would try it with the speaker laid horizontal and tilt upwards to the 22.5deg axis with listening position...

Tony

[Ed LaFontaine]

I'm gonna go out on a limb and guess the lobing referred to is a result of the mixed responses from the waveguide and woofer if the speaker is tilted back.

A horizontal placement of a speaker with the woofer and horn side by side would result in grossly different response across the horizontal plane.

[gedlee]

Originally posted by TRADERXFAN
As an idea for the center solution...
Does the vertical off axis response characteristics match the horizontal response characteristics? If so I would say tilt it back for the center to be at the specified 22.5deg tilt.relative to listening position.
If not, I would try it with the speaker laid horizontal and tilt upwards to the 22.5deg axis with listening position...

Tony

Tony

Again another cool idea - but I hadn't thought of that one!! No the response are quite differnt vertical and horzontal as you might imagine with a vertical displacement of the sources.

Thanks for that idea. I may actually try that one quite soon. Very good idea!!

[gedlee]

Originally posted by Ed LaFontaine
I'm gonna go out on a limb and guess the lobing referred to is a result of the mixed responses from the waveguide and woofer if the speaker is tilted back.

A horizontal placement of a speaker with the woofer and horn side by side would result in grossly different response across the horizontal plane.

The lobing is a result of the non-coincident sources at the crossover.

The less than ideal vertical response then become the horizontal response when it placed on its side so what you say is also true.

I have thought that the center speaker might want be narrower in directivity than the sides, but it still needs to be of the same configuration etc. If it were narrower then the "hole" could be moved out of the passband.

[noah katz]

"Put the center speaker NOT on stands and face it upward."

The 9 deg I mentioned is with no tilt, but if it hadn't been enough I actually would have tilted it downward.

Tilting it upward enough might create an issue with ceiling reflection, vs a floor reflection nicely attenuated by carpet.

"I just can't see why you need the small gain provided by the screen with the lumin power available with a modern projector. "

I really wanted an acoustically transparent screen; my first was Dazian fabric, roughly unity gain.

It was just too dim.

Several points:

1) I forget which projector you have, but the typical "1000 L" projector nets a few hundred L after calibration for correct color.

2) The gain isn't small - 2.8 w/optimum setup; I estimate I'm getting about 1.8.

3) A 133" screen is about double the area of the typical 8-ft screen

3) Not exactly germaine, but the HP is retroreflective, which gives it several qualities I'm loathe to give up - uniform image brightness from any viewing angle, good rejection of off-axis ambient light, and relative immunity to waves.

[gedlee]

How could you loose 80-90% of the light output just correcting the color. That just doesn't seem right. How close do you sit to this massive screen? I mean there are optimum sizes and distances etc. A screen that big would have you sitting back about 20 feet or more to be optimum and thats if its 1080. At 720 it would be even further.

Are your eyes OK?

[noah katz]

"How could you loose 80-90% "

More like 70%; the way I learned it, "a couple" is roughly 2, "a few" is roughly 3, more than that is "several".

First, most mfgr's just lie about the rating, and the lumens they do achieve is with all controls set to give max brightness, which gives much too high a color temp, and poor grayscale tracking, and probably white clipping.

Also they spec brightness at minimum throw ratio; at the long end of the throw range where I'm at, brightness is typically 30% lower because of the smaller effective aperture.

You can check it out for yourself in the reviews at projectorcentral.com

And I forgot to mention that the UHP arc lamps used in projectors lose about half their brightness by half way through their lifetime.

I sit roughly in the middle of my 14 ft wide by 22 ft long room, which is slightly closer than the 1.2 (or is it 1.25) X screen width recommended for HD material.

[Bryce H.]

Originally posted by gedlee


Ai is not a viable option at this point until such time as Ai gets back in business.

When did Ai go out of business? I just received an email from them 2 - 3 weeks ago with their current price list. Now I understand that the Abbey and Nathan are different than the Ai ESP12 and ESP10 because you further developed them, but they should still be an option, correct? And the ESP15 is the same as the Summa if one decided to go that route, as you said previously. Sorry just wanting clarification about them in/out of business.

[gedlee]

Sending out a price sheet and sending out the product are two different things. Price sheets they can do, product they can't. They have not shipped any product in about a year. I can and have actually shipped product. So I'll leave it for you to decide who's "in business" and who's not.