RF-7, Tilt for Lower Mids

[leok]

I have always wondered what the RF-7 would sound like in a D'Appolito configuration (horn centered between the two cones). As the speaker is designed, the two low mounted cones broadcasting identical information at different distances from my ears has seemed a recipe for phase problems with frequencies above a few hundred Hz.

No, I haven't replaced the "motorboard." I decided to align my ears directly between the cones instead of with the horn. I figured the crossover region might suffer a bit, but it's already compromised somewhat because of what it is and the existing RF-7 physical layout and I wanted to hear how things sounded with equal path length from both cones.

Instead of sitting on the floor, I have angled the RF-7s back so that a line from my ears to a point between the cones intersects the speaker face at 90 degrees.

I like the result. Imaging and recorded room (or hall) ambience are clearer. Lower mid fundamentals are better defined (good for piano and cello in particular, but most instruments seem to have better fundamental definition). The nice clean highs don't seem compromised.

I don't know that this would make much difference with loud rock, but for critical sweet-spot listening it's worth a try.

Leo

[Audio Flynn]

Craig NOS Valves did have his LaScalas tilted slightly a while back. I

have thoght about geting some matching walnut 2 in X 2 inch to tilt

them back without looking poorly.

How do you prevent the RF-7 from getting tippy?

[leok]

Rick,

The tilt isn't that extreme. However there is much more force on the back feet (or spikes in my case) than front.

Leo

[Speedball]

....duplicate

[Speedball]

Ah, an inexpensive tweek for my rf7's.........thanks Leo.

[Jay481985]

i still don't quite get how it works but if someone can explain how it is placed a bit better I would be much abliged

[leok]

If the RF-7 is standing vertically and the listener's ears are in line with the horn, the distance from the lower cone to the ear is greater than the distance from the upper cone to the ear. The two cones are producing exactly the same sounds at exactly the same time, which means the sound from the lower cone reaches th ear after the sound from the upper cone. Technically, this blurrs the sound. By tilting the speaker a few degrees back the cones can be aligned so the sound from each reaches the ear at exactly the same time.

It's up to the listener to decide if it's even worth a try, try it if it seems worht it and determine if there is an improvement. I think there is and prefer it.

Leo

[TheEAR]

leok,

Tilting speakers back,I am doing this since the Mission 765 days.All my tower(floorstanders)are tilted.

And yes it works great,all my speakers(not stand mounted)including center channel speakers are tilted to face the listener.The incline being very gentle,the speakers will not be close to tip over.They would need a solid push.

One of the pioneers of tilting(aligning the drivers)is Jim Thiel,almost all his designs have slanted(tilted if you so like)baffles.And this combined with tilting them towards the listening position gives outstanding results.

Good tip Leok,anybody cann do it (providing no little kids or animals run around the house).

[leok]

Arthur,

Absolutely! I actually got the idea when looking at a few of the speakers you mentioned. Yes, people have been doing this for some time. It obviously took me a while to figure out what you and others been doing all along.

Leo

[whell]

Leo - might you be able to post some pics of this revised set up? It sounds like something I could try with my RF-7's. I think I'm following what you're describing, but as they say, "a picture is worth...."

[Jay481985]

soooo.... what do you use to tilt the speakers.... I wonder if it will help with my rf-83??? since I have one more cone lower .......

[Raider]

Interesting.

This subject was discussed previously in the thread

http://forums.klipsch.com/forums/thread/782250.aspx .

The effect you describe is frequency dependent in all arrays to some degree. and is known as comb filtering, due to the resultant shape of the speakers response on a graph when measured from a fixed point. This is most noticable in the frequency range whose wavelength corresponds to the driver spacing.

This is a downsidel when using multiple drivers in an array to reproduce the same frequency spectrum. The upside is that multiple smaller drivers can be more efficient than a larger heavier-coned driver of the same area, and the multiple motors can offer better control of transients. Also, the resulting narrower profile of the front face of the speaker significantly improves the ill effects of baffle step diffraction from the reflections off of the front face of the speaker. These benefits are often more audible than comb filtering, so its a pretty reasonable engineering tradeoff. And comb filtering can also be compensated for to some degree by speaker positioning, as you are doing, for really critical listeners.

Klipsch elects to use a tapered array crossover in their center channel Reference speakers to help compensate for this, but not in the vertically oriented towers. Most folks seem to think the phenomenon is more noticable in a horizontal plane. Your experience, and that of others, seems to indicate some are more sensitive than others to this effect in the vertical plane as well.

It would be interesting to know why Klipsch doesn't use the MTM arrangement (mid-tweeter-mid) preferring a TM, TMM, or TMMM arrangement in their towers, but uses the MTM or MMTMM arrangement in their centers. Its all about engineering tradeoffs and best compromise, but it would be interesting to hear the logic behind their choice articulated. I certainly can't argue with the results.

[leok]

Raider,

I had completely missed the http://forums.klipsch.com/forums/thread/782250.aspx discussion. Probably, since I wasn't going to mess with the crossover (any more than I already have) I just read it quickly and continued to let the problem nag at me. I hadn't looked at the RC-7 solution very carefully in the past either, because I thought the different low pass frequencies for the cones were simply for frequency response smoothing. I should read more carefully.

Very nice technical description of the problem.

Leo

[PhilMays]

I guess now someone will sell an acoustic treated wedge to place under the front speaker feet. Starting at only 179.99 each.

Great tip. I'm going to try this tonight!

[Raider]

Maybe the Q-Link folks that make those golf pendants will make a medallion that you can place between the drivers to synchronize their output.

Or we could make something out of exotic wood with healing properties used by the ancient Mayans............

[Erik Mandaville]

Leo:

I wonder that this may be similar to sloped baffles for the purpose of time alignment of voice coils.

I guess it's sort of like what was done on the attached picture, the difference being that the cabinet itself (fired clay) was cut at an angle. I also like the result.

Erik

[leok]

Erik,

I don't know. I always figured the angled motorboards with different drivers had to do with time alignment, but since the drivers handle different frequencies the problem, or goal, is different than with parallel drivers handling identical frequencies. Nice looking speakers.

Leo

[Erik Mandaville]

Leo:

" but since the drivers handle different frequencies the problem, or goal, is different than with parallel drivers handling identical frequencies."

I understand what you're saying. I guess that is different from what I mentioned about time alignment. I wanted to mention that I remember awhile you back you described the effect of installing some light fill in your speaker cabinets. I'm going to try the same thing with our very early pair of Heresies. I bought some poly fiber fill at a nearby craft store for a first experiment. Acoustically, it's kind of interesting how the addition of extra material in a sealed enclosure can effectively increase the internal volume of the cabinet, as well as sometimes its efficiency.

Erik

[leok]

Erik,

Let me know how the fill works out. I would expect it to have a significant impact (good or bad). I'm particularly interested in how it works with the sealed cabinet. (It performed wonders with the passive radiator Chorus-II and destroyed the lower bass in the ported RF-7. But then the RF-7 started out pretty well damped.

Leo

[Erik Mandaville]

Leo:

I will surely let you know. I'm trying to finish some other writing for school (taking a break right now!), but should have a couple of hours this afternoon to work on that. I was just going to temporarily attach the stuff with double-sided tape until I get the amount, thickness, and placement sounding right (but who knows, I guess there's an equal chance, as you said, that it might sound worse).

Erik