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Old 23rd September 2006, 10:59 PM   #1
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Default Surrounds - how should they be done?

Surrounds, its love 'em or hate 'em in.

Most commercial dipoles and bipoles I see are often not implemented correctly(or at least not how I'd like it done) and I was wondering if there's a concencus on how they should ideally be designed?

Considering a bipole as an example, which would be used in a small room and be expected to offer increased spatial information for music and movies, what would you consider out of the following as optimum or worthy of consideration for further improvement:

Dual fullrangers firing at 45 degrees to each other

Single forward firing tweeter crossed at ~2Khz to dual 4" mid/bass firing at 45degrees to each other. And an 8-10" downfiring woofer crossed at 80hz or below.

Dual tweeters and mid/bass firing at 45 degrees to each other and crossed low ie, 1-1.5Khz. And an 8-10" downfiring woofer crossed at 80hz or below.

Perhaps this isn't the way to go at all and maybe an omni design with something like a deflector for the stuff from 200hz up. Again I see little theory or implemented and successful DIY designs. One that did catch my eye was Visaton's omni floorstanders which are available as a DIY kit but that would seem to be taking much of the fun away.

Or expanding on the Omni designing, using something which takes advantage of room surfaces such as ceiling and walls to bounce sound. Sounds nasty but I know of at least one design that does this.

Or maybe just a wide dispertion monopole design such as a 3/4" dome with 3" dome mid and suitable bass driver.

There's not really much talk so hopefully you can help me make my mind up and cement some kind of ideal for an in-ideal speaker.
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Old 23rd September 2006, 11:10 PM   #2
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I always liked the idea of, in back surrounds, A 4 or 5" full range firing forward and tweets fireing up. then set the crossover at were the full range would roll off or at around 8-12k Hz... thats me though...

Other than that I got a pair of optimus' that I did a x-over mod on that are aimed around 30deg on the wall from the ceiling that I'm happy with.
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Old 23rd September 2006, 11:34 PM   #3
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I played around quite a lot with positioning surrounds in my old house, and with the little speakers I was using, I found the best results was placing them in the back corners, firing up at the ceiling, mounted about about 50cm down. This was in quite a small room, 5x5m, so it may not work quite so well in a larger one.
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Old 24th September 2006, 12:50 AM   #4
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I'm looking at using them in a shoebox room anyway Al. I take it those were monopoles?

I've never really heard any decent bipoles or dipoles that take the form of surround, I'm not talking about Linkwitz's Orion or the like So maybe a good sturdy monopole design is the way to go but with a little creativity as you've highlighted.
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Old 24th September 2006, 02:54 AM   #5
tinitus is offline tinitus  Europe
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Hi Sid216

That funny, your idea with tweeter pointing upwards

Exactly what I have thought with my CSS125FR/XT19

At 10khz it might deal with not interfering so much with a widerange...I am not started yet, so I only guess, but tweeter might not need much attenuation
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Old 24th September 2006, 03:13 AM   #6
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Check out this comparison of each type, Shin.

http://www.hometheatermag.com/loudspeakers/25/

In the end, I decided a regular monopole was the safest, and most versatile option. It's nice to have the option to use it as a main speaker when the need arises.
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Old 24th September 2006, 03:25 AM   #7
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Quote:
Originally posted by tinitus
Hi Sid216

That funny, your idea with tweeter pointing upwards

Exactly what I have thought with my CSS125FR/XT19

At 10khz it might deal with not interfering so much with a widerange...I am not started yet, so I only guess, but tweeter might not need much attenuation
As far as I know, in a 6.1/7.1 system, there really is not much sound info there anyway. But when the need arises, its good to have a speaker that can dish it out.

I always thought a good quality full range with a reflecting tweeter would be ideal. with the tweeter bouncing around from the ceiling and walls, it would create a kind of delay making the room sound as if there is a little more depth. and with the wide range, the x-over would be dirt simple, just a 6db at least.

edit: as a test, build a simple enclosure and just set the tweeter on top to see how it sounds. I test small woofers in shoe boxes to see how they react. its simple and a bit effective.
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Old 24th September 2006, 03:38 AM   #8
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Quote:
Or expanding on the Omni designing, using something which takes advantage of room surfaces such as ceiling and walls to bounce sound. Sounds nasty but I know of at least one design that does this
A number of years ago I had a 5.1 set of Mirage Omni speakers for an HT, and while I didn't particularily enjoy the mains(at least compared to my 2-channel setup at the time) the surrounds were great. If I remember correctly they had a tweeter sitting in a 'pod' of sorts with a deflector above it, and then a 5-6" mid that was angled down 30-45 degrees directly beneath. Created a very believable sense of 'space' around you, but were still directional enough when needed. I have a feeling something like the CSS Fullrange/xt19 that was mentioned above would create something similiar to this.

That said, a friend of mine had a 5.1 set of defintive technology speakers and after hearing those I don't think i'd be able to go back to having surrounds that weren't truly full range. I forget the name, they were bipolar and had built in powered subs. It's amazing how much information is in those surround channels on certain dvd's, and I don't think they can be done justice with a surround that might hit 80-150hz at best and a single subwoofer for all five channels. You don't realize how much you've been missing until you hear a fullrange 5.1 setup IMO. They were small enough to put on a wall aswell.

Quote:
cement some kind of ideal for an in-ideal speaker.
I think you hit the nail on the head there, from a design perspective it seems to be more about managing the trade-offs than anything. Maybe take some of your own advice from the pc-xover thread(which i'm well on the way to copying..damn those waves apps are pricey but good i've used them in the pro-audio environment before) and write down a list of everything that you want your surrounds to do and then figure out a way to get there. For example, do you want them to be directional or not, fullrange or good down to 80-100HZ etc.

Tristan
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Old 24th September 2006, 04:31 AM   #9
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Movie theatres generally have 3-4 speakers on each side for wide, even coverage of the surround channels, then 2-4 (depending on the size of the theatre) for the rear surround channel. For larger rooms why not consider doing something similar with a bunch of small (say 1in+5in) monopoles, you can run them in series and parallel to keep ye' olde amp happy.
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Old 6th March 2008, 08:02 PM   #10
blue934 is offline blue934  Canada
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many manufacterers use angled bipoles to create a sense of space in a small room;

http://www.energy-speakers.com/v2/pr...age.php?id=298

and;

http://axiomaudio.com/surroundspeakers.html

is this just a marketing ploy? the only DIY info on the subject that i have found is;

http://www.gr-research.com/index.asp...ROD&ProdID=113

any new ideas?
blue934
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