Can K402 horns prevent imaging hole when placed in room corners?

[bracurrie]

I have always found this community of enthusiasts helpful and humorous. I have been on this fun with Jubilee clones 2 way ride for over two years. This is a long post to set up my question.

This last spring I came to the conclusion that my JBL 2435 drivers with DIY tractrix horns were holding me back. So I sprung for the Faital HF200 with Fastrac 400 horns. Wow what a difference that made, but I was still not hearing a good image. I rolled through any number of crossover settings and even calculated the proper time delay all with a mini DSP. I tried a number of speaker placements and settled for a setup that had the speakers at a roughly break the width into thirds distance apart with about a ten degree toe in.

Funny thing happened next, one of my old Adcom amps caught a cold and went haywire, and when I put my Forte IIs in until my amp was repaired I suddenly heard that imaging I was looking for. I attributed it to a clean back wall with nothing in the corners. About that time my Van Alstine SS amp that I had ordered a month earlier arrived. Oh JOY! Now I had good imaging and a very clean sound. Either the AVA amp is really good or the Adcoms were tired. I found a Hafler 220 that had been modified by Frank Van Alstine in the late 1980s, retired my remaining Adcom 535 and put the Fortes away.

While using the AVA for the tweeter horns I again set out to find imaging. I learned how to use the EQ feature of REW to set some filters to take the edge off the Jub clone bass bins and tame some uglies from the room. I found that 500hz was not too low to use as a crossover point and with a mix of filters set by REW and a couple set by ear I was beginning to hear it all, but not imaging. Argh! Then in these forums I read where Jubs and Khorns both belonged in their room corners to get excellent imaging results. (Also there was the K402 horn that has been acclaimed as very important to imaging and tonal balance with the Jubilee.) When I tried my Jub clone/Fastrac 400 in the corner toed in at a 45 degrees there was a big hole in the middle. So I put on my imaging reference CD Miles Davis Kind of Blue and started moving them out of the corner towards each other six inches at a time until the hole disappeared. But I left them toed in at 45 degrees. I then marveled at the imaging. [] See attached picture.

The downside to my setup is that the Fastrac 400 while still very good still has a defined sweet spot, but listening to them off axis with a small amount of added boost above 5000hz has given me a system that images beautifully with great high frequency balance. Also for the first time the system sounded equally good in my listening chair or at my desk near the back of the room. Finally there after two years of fun.

I need to thank Dave at Fastrac and Bob Crites who have made suggestions and discussed strategies.

After all this my question is this. Would K402 horns make it possible for the speakers to be in the corner and not have the imaging hole in the middle?

[tigerwoodKhorns]

by moving them away from the wall you are lessening reflections. One of the members here wrote a great thread on how to keep the horns in the corners and eliminate the reflections.

[dtel]

After all this my question is this. Would K402 horns make it possible for the speakers to be in the corner and not have the imaging hole in the middle?

Looking at that pic I would have to say yes easily. imo

I use the 402's 15' apart center to center, in a 24' wide room, and sit about 13' back, although they are not all the way in the corners but there is no hole in the center at all.

I have to ask, why are they pointed like that, it looks like they would cross way ahead of your chair, almost at the front of the rug, or it looks like it anyway ?

[Chris A]

Would K402 horns make it possible for the speakers to be in the corner and not have the imaging hole in the middle?

Yes, just put one absorption tile/pad on the side wall and front wall at the mouth exits to absorb the first foot or two of early reflections off these surfaces. Voilà! Instant imaging.

http://forums.klipsch.com/forums/p/154887/1631050.aspx#1631050

EDIT: If you continue to use your present hf horns, the "Fastracs", but sliding the speakers back into the corners, aimed at your listening position, I'd then put down some soft material on top of your bass bin cabinets all the way across the top (...thus losing the "wheelie dollies"...), then put down a throw carpet on the floor just in front of the bass bins of at least a couple of feet in depth between you and the bass bins.

If you get a box of acoustically absorbent tiles, you might also consider cutting a couple of them to size to place on the front of the bass bin cabinets over the center section, thus absorbing these cabinet reflections between the two bass bin mouths. The best way to describe why to do this: simply listen to the results, especially since you are crossing at 500 Hz, which is a bit higher than most Jubs are crossed.

The rest of your listening room looks good. And I wouldn't move those center acoustic panels...they're doing yeoman's duty there right now. The lower outside bass traps may be a bit over the top in terms of absorbing mid-bass frequencies, so you might simply slide them either inwards of outwards and flatten them against the walls again to collapse the space behind them--I'd first try about 50% volume reduction of the triangle formed by the walls and the back of the bass trap. It's a simple trick to try. Listen for the increase in authority of the mid-bass at your listening position, but not so much as to allow "booming" sounds to occur.

As far as the absorbent tiles go between the speakers - the more that you use horizontally at the hf horn height AND vertically between the speakers, the more imaging you will have, but the room will feel smaller, so there's a trade off there. You can also stack more tiles vertically on the side walls just at the bass bin and hf horn exit.

One more thing the think about/try: place an absorbent tile on top of your hf horns, allowing some of the tile to stick out in front. The idea is to eat the spilled midrange polars (below about 1200-1500 Hz down to your crossover frequency) in the vertical direction that wind up on your ceiling and floor, those that mess with your overall timbre and vertical imaging position.

Chris

[mark1101]

No offense, but that picture just doesn't look right to me. You should not have to position a pair of Jubs like that in any room. The bass bins are almost facing each other. How did you determine what room treatments you needed, what frequency ranges needed treating, and where to place those materials? They look pretty but I am always very suspicious of room treatments. IMHO treating a room is the single most difficult activity in audio to do. IMHO most room treatments are a guess and not done properly.

If you have to position speakers like that in any room to make them sound right.............something is wrong.

[Chris A]

No offense, but that picture just doesn't look right to me...something is wrong.

Mark,

In defense of Brad's approach thus far, I believe that I understand why he is where he is at presently. And I wouldn't lean on him too much about it since what he is doing with the toe-in and inset spacing is to control the early reflections that kill his imaging. I've been there and done that, too.

That's the reason why I suggested the simple acoustic treatment at the top of my reply, above: use one absorption panel on the side and front walls while the speakers are pushed back into their corners - and you get the best of both worlds: lf corner gain and midrange imaging.

BTW: since you've tried this acoustic panel stuff before: if you still have a 2-4 absorption panels lying around, you might try to temporarily tack up one or two vertically at the exit of your K-402s/K-305s on the side walls, then waltz over the the centerline and listen - I think that you'd be surprised by the results - imaging like you've never heard.

Chris

[mark1101]

First of all..........I love the look of those Jubs. Should have mentioned that. The positioning just looks very odd.

I have about 14 2'x4'x2" thick Owens Corning 703 panels and have experimented with them many times and in many ways over the years. I'm down to just 3 on the back wall to reduce slap. I found in my room that diffusion sounded better than absorption. I basically have my equipment racks at the site of the first side wall reflections where you are suggesting an absorption panel. Just another way to skin the cat. My room had gotten too dead with all the panels. I think we both agree on the placement.............that those first side wall reflections can make a difference.

However, back to the picture in this thread. If it were me, I would put the jubs back into the corners and remove the treatments between them such that there is nothing between the speakers. I would remove the overhead treatments. Where those overhead treatments are now.........there are no horn reflections that could even reach them. They are just deadening the room, and removing bass. I would carpet the first 10 feet or so. I would toe in just the top horns as required and use either a panel or diffusion at the first reflection as we've discussed.

Then, I would use an RTA to take some FR measurements and look at some waterfall plots as well to determine any trouble spots in the FR and use a tiny amount of graphic EQ to smooth those out.

If there is a hole in the middle, then I would decide if moving the speakers closer together (But keeping them on the front wall) solves it........or if they have to come too far out of the corners along the front wall, then maybe........maybe........we are looking at a need for a center channel. Hopefully not.

In answer to the original question of using 402 horns to solve the hole issue........well, I don't know. I think the sound would be bigger and with more even directivity with 402s, but if the speakers are too far apart for the room dimensions, then the 402 may not remove the hole.

[bracurrie]

Thanks for your thoughts.

IMHO treating a room is the single most difficult activity in audio to do. IMHO most room treatments are a guess and not done properly.

You nailed it. The placement of the panels was a guess. The room contained all hard surfaces and was harsh to my ear so I thought they would help. With my limited acoustics knowledge it seemed like a good idea at the time. They did deaden the room somewhat and made 85-95 db listening less stressful. But no measurements were made before or after so who knows. I don't think they hurt.

If you have to position speakers like that in any room to make them sound right.............something is wrong.

I do know that sometimes acoustics plays tricks on us. I tried the 45 degree placement on a lark and it seems to work for imaging.

[bracurrie]

Chris - Thanks for your thoughts. It was your posts that motivated me to try using the corners. I will try again when I have the materials to control the first reflection point. Brad

[Chris A]

Brad,

If you've got some old quilts, blankets, or comforters, you can try pinning those up in the locations by your Jubs...these substitutes actually work very well, as well as very heavy/thick curtain material - like the type used for theater curtains. This will give you an idea of the effectiveness of the technique without first having to buy absorption tiles.

Here is a link to the type that I use:

http://www.amazon.com/gp/product/B000T4M9PG/ref=oh_details_o03_s00_i00

There may be cheaper solutions available.

Chris

[tigerwoodKhorns]

Cask,

OT and not to hijack, but what kind of dog is that? That is a really good picture of her (or him).

[Chris A]

That's Tommy, our 8 year old Border Collie. We have to watch what we say around him, since he's spontaneously picked up the ability to identify ~50 words--even embedded in the middle of sentences. It's phenomenal...

[dtel]

I have to ask, why are they pointed like that, it looks like they would cross way ahead of your chair, almost at the front of the rug, or it looks like it anyway ?

I know it's strange to quote yourself but I still have not heard a good reason why the speakers are pointed like that ?

I don't see how any speaker would sound best like that, if they do there are serious problems.

Just asking

[bracurrie]

The problem is the room and the horn. I do not know why but this placement sounds great IMO. Because I am listening to the horns off axis I boosted the output to them 2db and boosted from 5k out with a high shelf a little may another 2db.

I have to ask, why are they pointed like that, it looks like they would cross way ahead of your chair, almost at the front of the rug, or it looks like it anyway ?

I know it's strange to quote yourself but I still have not heard a good reason why the speakers are pointed like that ?

I don't see how any speaker would sound best like that, if they do there are serious problems.

Just asking

[bracurrie]

Fine looking dog. Got two here and three cats. Momma can't stay away from the shelter.

[dtel]

Those are great dogs, my mother in law has one, very smart dogs.

It just looks really wrong the way they are pointed, I was thinking it looks like you would hear sound bounced off the side walls even more. I wonder if what your hearing is kind of the bose theory, bounce of of everything until the sound kind of comes together in the middle. ( not trying to be a smart @ss)

It just looks like the sound would be directed to the sidewall first, and reflect back to your chair. Strange that it sounds best like this.

I would normally say whatever sounds best but I think I would try something different than that.

"The problem is the room and the horn"................I think your right.

Maby try them in the corners pointed to cross just before your chair and move the room treatments to try and fix what you don't like ?

I surely don't have the experience most here do adjusting for room problems, just trying to help, but to me it does not look like the room is "to wide" to have problems like you describe, could be a combination of a few things?

I don't mean for any of this to sound negative, it's not meant that way at all, just really strange.

[artto]

"Can K402 horns prevent imaging hole when placed in room corners?"

No.

Welcome to the world of stereo

[artto]

I've been using a derived phantom center channel since 1978.

Do you think the Richard Burwen's system below has any problem with an imaging hole? []

[mark1101]

I would be careful here. It may be that the horns he is using now do not cover the whole width of the room. Bigger horns and with different directivity angles might. 402s are CD horns and broadcast almost equally across its whole pattern so the off axis complaints he is posting about might go away.

[Arkytype]

For a source of low-cost wall treatment, try these. They come in black, burgundy & tan. The fabric is fire-rated.

http://www.samsclub.com/sams/acoustic-panels-24-x-40-4-pk-black/193623.ip?sprodId=193623#spec

http://www.unitedplastics.com/consumer-my-theater.php

Lee