Open baffle question...

Smirkr

Member
2009-07-24 2:17 pm
Any thoughts on adding a dome midrange (monopole) to a 3 way OB? I'm currently running an open back planar tweeter, 8" midrange and 2 12" woofers per side (all active). I impulse bought an amplifier off of the 'Bay a few days ago and I'm trying to figure out my next move. ALL opinions and experiences are welcome!
 
A monopole in low treble between dipoles sounds like a disaster to me! Why on earth would you like to have different dispersion and room response in the most delicate range of hearing?

Smirkr, have you designed and measured your speaker's off-axis and rearside responses? How smooth is axial and off-axis response now?

Multiway dipoles are very difficult to make smooth in low treble 1-3kHz, beause driver's and baffle's effect on dispersion is changing rapidly. This is why LX521 and Nao Note a 4-ways with 4" mids.

NaO Note Design Objectives

Note_front-118x377.jpg
 

Smirkr

Member
2009-07-24 2:17 pm
Well, the DQ-10's use a mid dome and open back mid bass and I was wondering if there was some special merit to this approach. Maybe I'll just slap a 4" midrange driver in there instead and call it a day. I might also be interested in those knockoff BG clones...
 
Any thoughts on adding a dome midrange (monopole) to a 3 way OB? I'm currently running an open back planar tweeter, 8" midrange and 2 12" woofers per side (all active). I impulse bought an amplifier off of the 'Bay a few days ago and I'm trying to figure out my next move. ALL opinions and experiences are welcome!

In general with an OB, adding another driver/band to the system may or may not help. More is not always better. Honestly, a dome midrange is not going to "play well" with the rest of the OB setup.

Why don't you post a picture of the speaker. This will be helpful in terms of what you might do to the system to improve it.
 

lowmass

Member
2016-01-26 12:46 am
So I assume you want to cross the 8" lower and get around its issues above 1kHz with a dome?

The small well behaved mid cone is probably your best choice , BUT now you have to deal with a more complex crossover.

The problem with the "planers" that can go low enough is they all have limited dispersion in both horiz and vert. Some find this ok but I personally dont like it.
 

Smirkr

Member
2009-07-24 2:17 pm
So I assume you want to cross the 8" lower and get around its issues above 1kHz with a dome?

The small well behaved mid cone is probably your best choice , BUT now you have to deal with a more complex crossover.

The problem with the "planers" that can go low enough is they all have limited dispersion in both horiz and vert. Some find this ok but I personally dont like it.

Well, TBH I really don't have any complaints with what I have now. However, I was visiting my brother over the holidays and we were messing around with REW and a mic and the DSP on his system. I thought my imaging was really good but what I heard coming out of his system was on another level. I really am using these 8 inchers WAY above where anyone would recommend they be crossed over. They sound fantastic; imaging is good, but what I heard was other-worldly and I want some of that. so, I figure handing off to a smaller diameter upper mid would help. Knowing that Dahlquist mixed a dome and open back driver on the DQ-10 I thought I'd ask for all of your thoughts on the subject.
 

Smirkr

Member
2009-07-24 2:17 pm
In general with an OB, adding another driver/band to the system may or may not help. More is not always better. Honestly, a dome midrange is not going to "play well" with the rest of the OB setup.

Why don't you post a picture of the speaker. This will be helpful in terms of what you might do to the system to improve it.
 

Attachments

  • IMG_20190328_174542562.jpg
    IMG_20190328_174542562.jpg
    532.3 KB · Views: 160

lowmass

Member
2016-01-26 12:46 am
Smirkr

where are u presently crossing each driver?

IMO That 8" is going to have trouble matching ribbons fidelity at anything above about 1 k cross, however that ribbon is probably going to freak out with a cross that low

I suspect much of what you heard in your friends system is a cleaner mid range

If you want to stay with the wide baffle design and 3 way ( much simpler than a 4) I would simply get a decent 5" mid woofer to replace the 8"

It will be a cheap fix with big bang for buck
 
Last edited:

Tweet

Member
2015-01-29 6:33 am
Smirkr,

I realize cost is a factor but open baffle design is a challenge to anyone.


If I may, I would suggest you dump the 8" SB20 and use it in another project and select a better driver for the upper midrange to cross over to your planer. Actually, the SB 29SDAC-C000-4 dome would be a good choice replacement (although it is only monopolar) if you want a excellent quality dome tweeter inplace of the planer.

The ScanSpeak 'Discovery' 15W/4424G00 midwoofer would be a good choice with a crossover around 400c/s or above to the 830669 woofers. This would give you a clean upper midrange to your planer. Of course you would have redesign your crossover to suit, but tweaking is part of the game with OB design.


C.M
 

Smirkr

Member
2009-07-24 2:17 pm
Smirkr

where are u presently crossing each driver?

IMO That 8" is going to have trouble matching ribbons fidelity at anything above about 1 k cross, however that ribbon is probably going to freak out with a cross that low

I suspect much of what you heard in your friends system is a cleaner mid range

If you want to stay with the wide baffle design and 3 way ( much simpler than a 4) I would simply get a decent 5" mid woofer to replace the 8"

It will be a cheap fix with big bang for buck

I would have the same opinion had I not heard this particular 8" woofer. They defy all conventions. They are smooth, clean, articulate and roll off without any breakup to mention (5.6 khz/18dB). I have NO problems with them in regards to distortion. One of my favorite drivers ever. It's a shame they have such an unconventional frame shape. If the frames were round they would be an all time best seller (currently on closeout at Madisound for $27).

I'm not worried about going from 3 to 4 way. I've been doing this for awhile. My thing is: Is it worth it? I love my speakers. Maybe that time, effort and money would be better spent on some super-duper hoss-*** baffles. There is certainly room for improvement there. Also, I'm running a MiniDSP 2x4 with a cap and coil on the tweeters and the DSP on the mids and woofers. Perhaps I should get them into the same DSP realm. That opens up the whole time-alignment thing which may be more important to the task at hand.

Having said all of that... these SB 8" drivers are special. They are the stars of my OB show. I know I'm crossing them over way higher than a sane person ever would (at their rolloff). I know a lower X/O will change the imaging but how will it change the SOUND. I seriously love, love, love the vocals and highs that I have now.
 
Thanks for posting the pic of the OB system, Smirkr. If I could offer a suggestion it would be to fit a 5"-6" class midwoofer where the Beston ribbon is located now, and then just mount the ribbon onto the top edge of the baffle itself, e.g. "sitting on top", right above the midwoofer.

This placement of the new midwoofer will benefit from being close to the edges instead of central on the baffle, which is important in the band extending up to 1k-2k and slightly above. Cross the 8" to the new midwoofer around 750-800Hz and take it up to 2-3kHz before crossing over to the ribbon. This should help the system sound better in the critical band around 1kHz.

Some possibilities for the new midwoofer, that I have personally measured and used in OB systems, are:
Audax HM130C0
SB Acoustics SB17MFC35-4
Peerless NE180W-04

The best one of the above three for your application would be the Audax (it's a 5.25" driver). The least expensive is probably the SB Acoustics.
 
Last edited: