[rick57]

Martin
Thank you.  

Rudolf,
to an English only reader, your site looks very good.   I tried to translate with babelfish, but it spat the dummy (and each page has the same web address) – any chance you will translate it?

I’m planning different dipole systems in two rooms:
One using the Linkwitz Phoenix “W frame” woofers that I have nearly completed, to be used over 40- 100 Hz, with sealed monos below.
In a room with very high (3.8 m) cathedral ceilings, due to limited floor space, I was intending to hang the woofers from exposed trusses about 2.5 m from the floor, 1.3 m from the ceiling. With time alignment, possibly I should consider mounting them on the ceiling.  

The other room will have sealed monos up to say 70 Hz, then for serious listening, baffles about 0.9* 1.1 m, that (again due to no floor space where you would normally put dipoles) fold down from the ceiling, with a rope pulley. (The alternative is acrylic baffles).  
I was going to mount the drivers at the low end of the baffles, avg about 0.7 m from the ceiling, but it seems it would advantageous to mount them close to the 'top' (the ceiling).

Is the advantage of woofers near the room boundary increasing the SPL, in the range about 25-50 Hz?

Cheers

[Rudolf]

Rick,

thanks for your kind words. I never really thought that dipolplus.de would get that much attention abroad. And if people like you don´t stop pushing me for a translated version, it really might happen - some day.

I certainly can´t answer your question more thoroughly than MJK already did. Knowing your driver parameters one could easily simulate the effect of border loading with his OB worksheet. On my website I tried to simulate the same with EDGE, using the mirror image method:


Simulation is for an ideal driver mounted on a 100x30 cm floorstanding baffle at 85 (green), 60 cm (magenta) und 30 cm (red) height. Listening position would be at 3 m distance and 0.85 m height. Don´t look at anything above 1000 Hz. The achieveable gain below 200 Hz is obvious, but it will not exceed 6 dB by theory.

What I can´t estimate is the psychoacoustic influence of a sound source hung that high. You might ask hurdygurdyman, under which conditions his IB woofer in the  attic is really vanishing.

Rudolf
www.dipolplus.de

[hurdy_gurdyman]

What I can´t estimate is the psychoacoustic influence of a sound source hung that high. You might ask hurdygurdyman, under which conditions his IB woofer in the  attic is really vanishing.


www.dipolplus.de

My attic IB is crossed quite low to fill-in below the 45-50 Hz range. Nobody has been able to detect it from listening yet. All the sound seems to come from the main OB's. I don't think I'd cross much higher than that, though. In my present set-up, I can't play the sub by itsef, so can't listen to it or measure it without the main speakers playing. I'm driving the sub amp/XO from the output of the mains tube amp and need to keep a load on the tubes. Someday I'll get some load resistors and play the sub alone to see just how easy it is to locate it by ear.
My ceiling is 8 feet high.

Dave

[JohninCR]

Rick,

As Rudolph's graphs demonstrate, boundary gain is significant and
it seems to be what makes a minimal baffle work so well for me.
I've thought about getting my woofers up near the ceiling, but
haven't tried it yet.  I have 2 concerns in doing so, decoupling
the driver from the structure and possibly creating a disjointed
sound. 

I've found open bass to be more directional than monopole.  I've
tried a single open sub and found that the soundstage collapsed down
toward the sub even when crossed low.  The same doesn't happen
with a single monopole sub.  Having the woofers up near the ceiling
may actually be a benefit in this respect by opening up the soundstage
even more.  Please let us know your results if you try it.

[Bob in St. Louis]

I can't play the sub by itsef, so can't listen to it or measure it without the main speakers playing. I'm driving the sub amp/XO from the output of the mains tube amp and need to keep a load on the tubes. Someday I'll get some load resistors and play the sub alone to see just how easy it is to locate it by ear.

Dave, can you get a roll of cheap 'zipcord' and set your mains in another room (or further depending on lenth of wire) with the door closed?
It'd be cheaper and easier than making a false load, wouldn't it?.
Then you could hear just the sub.

Bob

[rick57]

Rudolf
A picture (or a graph) tells a thousand words - thanks for the simulation graph - all is now clear.
(when I get a couple of amps out of the way, I will have a very good play with dipole model variables )

> I never really thought that dipolplus.de would get that much attention
With the super concise presentation of material at linkwitzlab.com, it may be the best dipole site there is  . .

Maybe as my favourite music is more powerful music (eg zeppelin), I hadn't thought of a psychoacoustic negative in a high sound source. However it may not suit acoustic music eg country blues. Better do a mock up - thanks for the concern!

Cheers

[hurdy_gurdyman]

I can't play the sub by itsef, so can't listen to it or measure it without the main speakers playing. I'm driving the sub amp/XO from the output of the mains tube amp and need to keep a load on the tubes. Someday I'll get some load resistors and play the sub alone to see just how easy it is to locate it by ear.

Dave, can you get a roll of cheap 'zipcord' and set your mains in another room (or further depending on lenth of wire) with the door closed?
It'd be cheaper and easier than making a false load, wouldn't it?.
Then you could hear just the sub.

Bob

Bob,

I just need to pick up some heavy wire wound resistors to use for a load. Only a few bucks. I'm just waiting until I have a reason to send in an order for something else to go with it.

Dave

[Bob in St. Louis]

Gotcha Dave 

Bob