[bill13]

Greg,

Sorry, I somehow (hastily looked at the thread) did not see, or realize, that that the responses were from you.   Anyway, would appreciate any comments about using an OB side-by-side mounted vertical array of 6.5" woofers to cover below 300 Hz.  Do you think that a vertical array of inexpensive smaller woofers can equal, or possibly surpass a single larger woofer?

Thks,

Bill

[studiotech]

Hard to say.  I think it could work just fine...

Smaller woofers of that style are certainly going to have a higher Fs than something much larger, so getting below say 60-70Hz might be difficult, but I'm sure they could be EQ'd to be solid at least that low.  It remains to be seen how much EQ is required and how much power those woofers can take.  If listening levels are generally below 90dB SPL, they ought to be fine.  I might have to check back in on that thread to see what the outcome was.

Greg

[JohnR]

Do you think that a vertical array of inexpensive smaller woofers can equal, or possibly surpass a single larger woofer?

Bear in mind that it takes 6-7 6" woofers to equal the cone area of a single 15" woofer. Xmax is typically lower, and Fs is typically higher. In the case of the Aura NS6-255-8a (I assume that's the woofer you refer to?), the woofer alone rolls off at 75 Hz, so combined with baffle rolloff you will have a tough time getting it flat much below that. If using separate subs, of course, that would be less of an issue.

[studiotech]

Replacement Neo10 and Focusrite 2i4 are here.  Focusrite installed and working under Arta and RoomEqWiz just fine.  Back with more soon.

[bill13]

Here's a photo of two OB experiments that did not work out:

1. The tall OB speaker prototype with four vertical Neo10 mids had a big dip in the lower treble at my listening location - will remove the top Neo10 because previous measurement with three stacked Neo10s was much smoother.  Perhaps I should tried mounting the four Neo10s with two vertically stacked Neo10s on each side of the RAAL 140-15D.  Danny Richie's quad-Neo10 measurements with crossover at 2500 Hz seems to imply this quad arrangement might work.

2. The little two-Neo10 speaker was intended as an experimental desktop nearfield monitor.  Measurements indicated that the Raal ribbon MUST be vertically oriented - horizontal radiation pattern is unusable even with the foam pads. 

I should have listened to Greg about horizontal mounting the Raal 140-15D.  Maybe can post some measurements if anyone is interested - but the images are not clear.

Bill

[studiotech]

My Digmoda are still being used at the studio, so no measurements to report yet, but I got the rear grills installed finally.  Just some thin, basic foam in there more to hide the wiring and rear of the drivers than really try to absorb anything.

Greg

[AJinFLA]

Had a chance to hear these this weekend...and tour the Studio. Thanks again for hosting Greg.
Excellent sound, very balanced, very detailed. Greg really has them tuned to his room. DSP helps
I tend to listen more for problems, these were hard to fault. Only nitpick would be depth of image, but that is highly room/placement dependent. Gregs setup is across short length of room.
Unfortunately did not get to hear any of the studio stuff, including the (large) DIY mains and his ribbon 3way nearfields, as there was an interview in progress.
Maybe next time.

cheers,

AJ

[studiotech]

Thanks AJ.  It was good to hear your 1812 in a known environment rather than the Jax Axpona show.  They are very well balanced also and there is not doubting the solidity of the coax imaging.  And the low end rocked for a pure open baffle design.  Now I'd like to hear them at your place since they sound even better there.

Yeah, since we had a somewhat similar depth issue with your speakers in those same locations, there will be many more nights of moving and shifting of placement to try to maximize what I can get in my room.  As I mentioned, auditioning them in a more suitable location, the ambiance around instruments was holographic, but not in my room.....yet.  I'm going to move the TV completely out of the way and remove all treatments and start from scratch.  Adding single spots of treatment back around carefully, one at a time.

Thanks again for stopping over.

Greg

[this_is_vv]

Thanks AJ.  It was good to hear your 1812 in a known environment rather than the Jax Axpona show.  They are very well balanced also and there is not doubting the solidity of the coax imaging.  And the low end rocked for a pure open baffle design.  Now I'd like to hear them at your place since they sound even better there.

Yeah, since we had a somewhat similar depth issue with your speakers in those same locations, there will be many more nights of moving and shifting of placement to try to maximize what I can get in my room.  As I mentioned, auditioning them in a more suitable location, the ambiance around instruments was holographic, but not in my room.....yet.  I'm going to move the TV completely out of the way and remove all treatments and start from scratch.  Adding single spots of treatment back around carefully, one at a time.

Thanks again for stopping over.

Greg

Greg,

May be i missed but is your system active or passive...if passive what is cutoff frequency you are using and if active what are the amps and power rating you are using.

As i am finding some issues with different power ratings amps i am using for various equipment...


V

[studiotech]

Greg,

May be i missed but is your system active or passive...if passive what is cutoff frequency you are using and if active what are the amps and power rating you are using.

As i am finding some issues with different power ratings amps i am using for various equipment...


V

It's fully active.  Digmoda 552.  3 way class D with DSP all built in.

http://www.digmoda.com/

Greg

[ProfNiko]

Greg,

Sorry, I somehow (hastily looked at the thread) did not see, or realize, that that the responses were from you.   Anyway, would appreciate any comments about using an OB side-by-side mounted vertical array of 6.5" woofers to cover below 300 Hz.  Do you think that a vertical array of inexpensive smaller woofers can equal, or possibly surpass a single larger woofer?

Thks,

Bill

Hi Folks -
Sorry wasn't keeping an eye out on the forums and didn't realize my dipole experiment had migrated over here. 

Greg is right, the FS of smaller woofers are the limiting factor when comparing a column of smaller woofers to a single larger woofer.  Above 60 Hz multiple smaller woofers have advantages (in my opinion).  The mass of the smaller drivers is significantly lighter, and I believe I can hear the combined smaller lighter drivers as faster and more dynamic than that of a larger driver.  Each driver in a column is working less hard and distortion levels at higher volumes is reduced (above 60 Hz).  Combined drivers can usually achieve a higher sensitivity than a single large driver.

To really get deep (on paper) you have to go to larger woofers with lower Fs measurements.  You could EQ boost smaller woofers to compensate for their roll off, but you would greatly increase their distortion and limit peak volume.  My design intent for these wasn't aimed at deep bass at all.  I figured they would be flat to about 65 Hz.  The slim woofer column was about spatial imaging with smaller faster drivers to blend well with the lightning fast B&G planar drivers.  I have a 3 x 18" infinite baffle subwoofer in the room to handle anything the dipole woofer columns could not.

In my room (15x22x7-6") the column of 6.5" woofers is flat (measured) to 60Hz without any EQ boosting, and they are measuring -6db at 50Hz, -12db at 45 Hz, and drop off very rapidly after that.  In an anechoic chamber my guess they would be flat to about 70 hz with an F3 of 65Hz.  An interesting and unexpected behavior I didn't predict from this design is the in-room response seems to augment low end from the woofer column much more significantly than the same room does with a box design speaker with the same F3 in the same location. 

There seems to be a difference between a box speaker flat to 60 Hz vs a column of OB woofers flat to 60 Hz.  The column just has a transparent, nimble, and effortless quality to deeper bass than their measurements would suggest.  I have built and measured a ton of designs over the last 20 years, and these speakers SOUND like they have an F3 closer to 45 Hz, though they measure 60.   My Marantz pe-amp thinks the same.  After letter the Auddessy auto-calibration ring out the room it perceives the OB woofer column as having a needed crossover point at 40Hz to hand off to the subs.  The same calibration with box speakers flat to 60 Hz yields a 60 Hz recommended crossover point from the pre-amp.

All this is to say, even though multiple smaller woofers in a column will (on paper) show a fairly modest F3, their usable real-world bass is very much more impressive than the numbers show.  I can, at the press of a button, integrate a very, very well blended 3 x 18" sub woofer (flat to 20hz, F3 15 hz) into the mix, and I find more and more I am perfectly happy to listen to the dipoles without them.... (most of the time) 

Professor Niko