Rear speaker - feasible???????

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Just want to check if these are feasible for rear speakers that would be placed behind the listener (about 1.8m high) with the tweeters firing towards the front of the room. The 2 mid/woofers would be wired in parallel and share the same enclosure. Is there problems with having mid/woofers at 90 degrees or 135 degrees to one another.
I'd appreciate any thoughts or comments.

Peter (Rabbitz)
 

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Did you just think of this or did you see it somewhere else?

Cause I just seen a diy speaker page where the designer made the speakers like you thinking of doing (the picture on the left). He stated the adantages of such a design and he also buillt one that was flat in the front. Don't know the webpage, I think it might have been a center channel speaker though.
 
That design looks to be a simple compromise of a true dipole design. Dipoles often make the best surround speakers because they can overcome odd room shapes better.

Personally, I don't like that design because it is tailored to 5.1. I run 6.1, and that speaker would interfere with my rear centre channel.

Go for a dipole design.
 
Just completed...

a pair of rears almost exactly the same as diagram 1. except that they have a slight downward pointing lean on them. Pics as soon as developed. They are designed to be positioned flat on the wall, just above head level, just behind the normal listening position, providing a diffused rear effect, with reflections from the back wall also contributing.

The guy who they were built for says they do the job extremely well.

I have also used the angled MTM as centre speakers to obtain a somewhat wider spread. The angle can be narrower or wider depending on the room proportions
 
Thanks for the replies.

I've seen plenty of rears with TMT configurations either bipole or diplole but have been for side wall mouting. I can't use dipoles as I don't have any suitable side walls. At the moment I'm using monopole at the rear in a 5.1 system and I am after a bit more diffused pattern.

The only place I've seen this was a centre speaker in the Loudspeaker Design Cookbook.

Peter
 
Bipoles

Thanks Andy

Your picture shows exactly what I'm after.

I didn't want to get additional tweeters to make bipoles - I've got enough to try and cram in these boxes. The mid/woofers will be going up to about 5000Hz which should throw a bit of higher energy to the side walls (which are vastly different distances from each speaker) and one of the reasons for wanting 2 mid/woofers was to increase the SPL up to 89dB to match the tweeter so I don't have to use resistors to attenuate the tweeter. The Xover will be 1st order for the mid/woofers as they start rolling off around this area and 2nd order for the tweeter.

In your photo the drivers look like Vifa TC11WG(SG) & D19TD(SD)?

So now I know the idea isn't crazy I can start to work out the Xover. I've already got the box volume and port worked out.

Cheers
Peter (Rabbitz)
 
Smart or what???

Well!!!!!!!!

Aren't I smart. Not really - it's just that I got some D19SD-05-08 and TC11SG-69-08 for these speakers at a good price from Mass Technologies and thought they looked familiar.

Now I know I'm travelling in the right direction. Thanks. When I work out the Xover I see if your kind enough to give me an opinion.

Peter (Rabbitz)
 
Well I'll be!!!!!!

I'm at Valentine - small world hey. You'll probably hear me from Broadmeadow if I stuff it up.

I think I'm ready to roll on this job.

Have worked out the crossover. Going to let the woofers roll off naturally (I can always add a xover later if required) and put a 3.3uF Met/Polypropylene cap and 0.33 inductor for the tweeter to give me a second order xover. I calculated using the driver resistance at the xover frequency and not the nominal figure. I think thats right. Seems to line up with the Vifa recommendation for 5000Hz.

Thanks again.
 
Timn8ter: re locatisation etc

I don't know if what I'm going to say is correct, its just an idea for consideration.....

If you listen to a pair of rears during HT there seem to be 2 main sorts of sound that they push through them.
Firstly there is a lot of background music and effects in the midrange area, which I think needs to be diffused to create an overall feeling of space... secondly there are the directed sounds, such as doors closing, glass breaking etc etc etc which are very often at a higher frequency range......

open for discussion ..........
 
My understanding is that, at this time, there are different ways of mixing the rear channels. One method is to roll-off the highs and lows creating ambience, the other is to use more discrete directional sounds. This is why some manufacturers have produced switchable rears, changing from reflective to directional depending on the material. Rabbitz has chosen a compromise but more discrete application. Most of us home users will have to decide on a compromise also.
 
Re: Re: Bipoles

Andy Graddon said:



Well done !!!! 2 x TC11SG49-04 (in series) + D19TD.. series x-o..
the TC's were on special and I had a few D19's in the cupboard !

i got 4 x TC11 and 2 x D19 what is a better config?

a) tweeters in a vertical array woofers on either side WW TT WW
b) woofer in center flanked by tweeters T WWWW T
c) tweeters in horizontal array in center flanked by woofer WW TT WW
 
Almost complete.........

The rears are almost complete.

Have been tested as a stereo pair to to make sure all is well and they have come up extemely well - ran them along side some B&W 303's. Just have to finish the grilles and run some movies through them. Will post some pictures when the film is developed.

I'm a very happy chappy.............
 
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