New MJK Baffle Article

Status
Not open for further replies.
Jump to Latest
#543
Hello all.

I'm wondering if either of these would work. What happens to the radiating figure 8 pattern when one half see's a finite baffle and the other side see's something closer to an infinite baffle -- okay not infinite, but really big by comparison - approx. 6m (nearly 20') from front to back going the long way round.

Obviously the baffle to the left of the entertainment unit (EU) has the drawer protruding forward of the baffle, potentially upsetting some of the upper frequencies covered by the woofer.

If the upper frequencies covered by the woofer would be upset due to the EU's drawer then a simple extension on the baffle to create an 'L' shape would allow for the baffle to be flush with the front of the EU like the baffle to the right in the image.

Of course if it's just a stupid idea and I haven't thought about it enough, which I haven't then could a moderator please delete for fear of public lynching 🙂
 

Attachments

  • MJK_OB_Q.jpg
    MJK_OB_Q.jpg
    21.7 KB · Views: 1,027
Last edited:
#544
Here is a similar concept that I have been working out using some Wild Burro Betsy speakers in OB combined with a tapped horn hidden into the bookcase proton of an EU. The sketch shows one bookcase as being 36 inches wide and the other as being 24 inches wide to see what they would look like. In application both bookcases would be the same size.

Now if I could only come up with some $$$ to do a bit of prototype work 🙄

In this concept everything folds away for storage and WAF......(of course)
 

Attachments

  • Bookcase Speaker Concept w Betsy Driver v1-1b 07 Dec 2009.gif
    Bookcase Speaker Concept w Betsy Driver v1-1b 07 Dec 2009.gif
    127.6 KB · Views: 1,011
#546
woody said:
The article calls for a 12db/oct xover. If I biamp could I use 6db/oct without serious
problems. I plan to only use ~2w so power handeling for the fe103 using a 6db/oct
xover shouldn't matter.
Click to expand...

First order slopes should work, I simmed low pass at 200 Hz and high pass at 500 Hz and the response looked pretty good. You could probably dial it in better by making the crossover frequencies a little closer, but the concept looks promising.
 
#548
Hi Jim
You should try and lift the ground on your plate amp plug
it will eliminate that hum.

Jim Shearer said:
Executive Summary:
Up and running!
WOW! WOW! WOW! WOW! WOW! WOW! WOW! WOW! WOW!

Review:
I am using a plate amp to provide the XO and drive the woofers; I may not have the settings just right yet. And the plate amp has a hum which was beneath notice when it was used with an inefficient sub, but which is bothersome with the 95 dB sensitive Alphas. My brother listened to them and pronounced them too bright. I applied a small amount of treble cut (via tone controls on the Yamaha CR-1000) and agree that helps. I will decide later if I want to buy the rest of the XO parts so I could eliminate the plate amp.

What I love about Magnapan and electrostatics is all there. In fact, most of what I like about Martin’s Lowther PM2A’s is there. I was thinking that I would have to save up to buy a pair of Lowthers--but no more! OK, they aren’t Lowthers, but it’s close enough for me.

Open, spacious, clear, and detailed. Not quite the holographic projection I’ve heard from Martin’s PM2A’s (both in MLTL and OB.) Still, much closer to what I want than the Fonkens and the Metronomes (both F120A and FE108eSigma.)

Jazz and vocals are excellent. Good sound stage, dept, imaging.

They can do justice to large scale orchestral works which strain the smaller speakers. And curiously, they are the first speakers I have heard which make Paavo Jarvi’s recording of Britten’s The Young Person’s Guide to the Orchestra (Telarc CD-80660) sound decent. On any other system the bass drum is loose, flabby, boomy--makes me wanna puke. Makes me sorry I bought the CD. On these OB’s, it’s OK--not quite right, but listenable. (But I still wonder WTH the recording engineer was using for monitors.)

The low freq extension seems to be enough that I am not motivated to add a sub at this point. I will make some measurements later.

Pics to follow....

Chrisb:
Stop what you are doing. Forget about the yard. You need to build the FF85k OB NOW! If you think the FF85k sounds good in a box, you’ve GOT to hear what it does OB. (Assuming you like the dipole sound.)

Martin:
Thank You! Thank You! Thank You! Thank You! Thank You! Thank You! Thank You! Thank You! Thank You!
Click to expand...
 
#556
Dave,

And I have you to thank for turning me on to this driver with your comments and the micro-Fonken. Those sounded so good that I immediately ordered a second pair from Madisound--which lead to the MJK OB build late in the season. (And good that that happened as I have not had time to begin my planned builds for this summer.)

Cheers, Jim
 
#557
MJK's "OB 2 drivers corner passive" worksheet simulation of FF85K shows a -5db decrase in the SPL response, resulting in a final SPL of 83db for the full range driver. Did any of you observed the same result? I run the simulation after I noticed a significant reduction in SPL after replacing 86dB/Wm cheap car speakers with 88dB/Wm Fostexs in my cardboard OB prototypes.

I wasn't expecting this since the FE103En didn't exhibit this behaviour in MJK's original OB paper and rated SPL values are very close (88 vs. 89dB/Wm). Can you please tell me which T/S parameter contributes to this result for FF85K?

If I'm not making a mistake in the simulation (though my listening confirms this result), is it the semi-U-frame that helped Jim balancing the SPL levels of drivers by reducing the LF SPL?

Thanks.
 
#558
leehan said:
MJK's "OB 2 drivers corner passive" worksheet simulation of FF85K shows a -5db decrase in the SPL response, resulting in a final SPL of 83db for the full range driver. Did any of you observed the same result? I run the simulation after I noticed a significant reduction in SPL after replacing 86dB/Wm cheap car speakers with 88dB/Wm Fostexs in my cardboard OB prototypes.

I wasn't expecting this since the FE103En didn't exhibit this behaviour in MJK's original OB paper and rated SPL values are very close (88 vs. 89dB/Wm). Can you please tell me which T/S parameter contributes to this result for FF85K?

If I'm not making a mistake in the simulation (though my listening confirms this result), is it the semi-U-frame that helped Jim balancing the SPL levels of drivers by reducing the LF SPL?

Thanks.
Click to expand...

Same problem in my simulations 🙁 Are really that inefficient ?
 
#559
fakamada said:
Same problem in my simulations 🙁 Are really that inefficient ?
Click to expand...

Are you setting the value of Sd properly in driver properties? It turned out for me that I took that field as a formula instead of a value that needs to be entered.

You can replace the area calculation formula directly with the value of the Sd in the worksheets, i.e replace

"pi*r^2" cm2

with

"28.4" cm2.

Hope this helps.
 
Status
Not open for further replies.
Top Bottom