Dipole or Monopole?

[Hank]

Jon, a couple of quick items: Your rendering appears like the ribbon cabinet is sealed. I thought you were definitely a dipole guy for these LS's. To reduce weight and make for one mid-woof cabinet, how about using Baltic Birch for it, lined with dampening material?
Hopefully, your airplane jaunts will decrease soon. Look at the bright side: you're racking up the frequent flyer miles!

[ThomasW]

Hank

Jon's plan has always been to run the midwoofers in an enclosure. Originally he was going to have the little MCM drivers do bass too. But that cabinet would have been a little on the large side. So the newest plan is 2 sealed boxes each with 4 MCM 6.5"s. Those will stack on top of a woofer/subwoofer enclosure.




theAudioWorx
Klone-Audio

[Hank]

Thomas, I referred to the ribbon cabinet, but I know- you can't mix dipole and monopole in the same speaker configuration.
Well, concerning large, how much larger to get the 6.5's to do bass? The larger cabinet might be worth it to get rid of the separate woofer box. Separate and remotely located subwoofer of course. I thought the Grand Pooh-Bah's believed in separate subwoofers optimally placed.

[ThomasW]

I believe his plan all along has been to run the ribbon monopole.

He told me the volume differences over the phone but I don't remember the specifics. There was a significant size decrease using the MCM's as midwoofers.

Yes if possible we prefer an optimally placed sub. But since Jon lives in a rental apt that's not possible




theAudioWorx
Klone-Audio

[JonMarsh]

From an earlier portion of this thread:

"JonMarsh wrote"

Dipoles are most effective, IMO, for suppressing room interaction, in the range from 100 Hz up to 600-1 kHz. Some well known speakers utilizing the dipole principle only employ it in the upperbass/lower midrange, like the Legacy Whispers. This is a critical area for removing what is commonly perceived as "box" colorations in the bass or lower mids, but which is more complex, and due not just to the box, but the interaction of the box and room placement. (I think we've strolled down this path before).

Above about 700 Hz, dipole behavior becomes more complex, and begins to resemble a combination of two infinite baffle speakers with the rear wave reflected back off the room walls. This can make for larger sound field, and more widely distributed sound field, but it probably *won't* result in pin point imaging. The ear is dependent on the space clues and room acoustics on the recording- to the extend that the speaker system and playback room substitute their own "signature", the original acoustic will be diluted.

As Thomas notes, a large dipole system in rooms the size of his family room are probably not practical, on several levels. Here, I think either a smaller dipole system, or a carefull positioned monopole might work better. With correct positioning and suitable room treatments (see Thomas's posts on DIY treatments for some hints) the room contribution with a monopole system can be minimized. *

Re the volume tradeoffs, extended low bass can be had with rear volume for each 4 6-1/2" drivers with 110-125 liters. But the updated design concept above for a three way modular system with a single HP pole between 32 Hz and 100 Hz requires only about 65-70 liter per each 4 drivers.

I'm planning on going the ply route, anyway. Just thinking about how to break the system up into more manageable "chunks" (My X1's are already in the fairly stupendous weight category (woofer cabinets 225 lb), and being the aging geezer that I am, even with my past rock and roll history, moving big cabinets is getting to be something of a pain. )

Going over the woofer design options, again, optimizing this first pass for compactness, a sealed and EQ'd pair of BPD1203's will handle the below 75 Hz duties- each in their own boxes, which will be the base for the line arrays- their 26 mm Xmax will be up to the task....






Blueprint BPD1203 NOS*


(* New Old Stock - Blueprint appears to be no longer operating, and these drivers are not available, though similar TC SOunds based drivers could get the job done- probably at a much higher price. These set me back about $200 each on a special buy.

Woofer box visualization was done on the plane last night coming back from the windy city- will post later today. This matches up with the upper range, and provides a hopefully near ideal launch platform for the monopole line array....

I figure, once you decide to make use an additional sub(s), building the main system for extended bottom end doesn't make much sense- at least not for me. But I can provide a design plan for those interested- I would only change the cabinet height and depth, not front panel width, so crossover would work out the same.


Best regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[Jack Gilvey]

New Old Stock - Blueprint appears to be no longer operating, and these drivers are not available

Wow, news to me. I guess my still-unused 1803 is a real collector's item, I'm guessing very few were sold.

[JonMarsh]

OK, as promised, the submodule concept. One of these will be the literal and figurative underpinnings of each speaker using the RD50 and midwoofer array.


Woofer module with BPD1203

In order to desist in my continuing hijacking of this thread, ops: any further discussion of this specific system will be in a new thread. :LOL:


-Jon




Earth First!
_______________________________
We'll screw up the other planets later....