New Omnidirectional Project Complete - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 9th October 2007, 03:06 PM   #1
diyAudio Member
 
Join Date: Jan 2006
Location: Indiana
Default New Omnidirectional Project Complete

Hi all,

I wanted to share the latest omnidirectional project I'm wrapping up for those of you who dont frequent some of the other forums I have posted it on. Technically, it might be best described as a hybrid omnidirectional speaker system, not a true omni. I have been calling it HOSS (hybrid omnidirectional speaker system). The drivers are all Dayton RS drivers, including the RS265HF 10 sub, two RS150-4s and an RS28AS for tweeter. I wanted to make it more acceptable aesthetically than my first omni project and at the same time address a couple of possible sources of weakness in that design.

The project includes two RS150-4's in series, one up and one down firing as in my first omni design. The RS150 allows for a narrower baffle and smaller boxes than my first omni which used the 7 RS180-8. They can use sealed boxes about 1/3 the size of the RS180's, can be crossed a few hundred hertz higher, which pushes the RS28AS less at its low end. The baffles are rectangular, rather than square and offset the RS150's toward the front of the baffle. As a result of the forward placement of the RS150-4, the tweeter baffle is also not inset as much as it was on my first omni design, which help reduce diffraction effects from the up and down firing driver baffle edges and increases the vertical dispersion some.

The RSS265HF will be in a separate, tapered enclosure. I wanted to keep it small to improve aesthetics, but have good low end output with an F3 around 30hz and with room gain plays solidly well into the 20s. Ive always been interested in TLs and decided to take that approach with this bass bin. I decided to use the RSS265HF because it has low distortion, works in a relatively small volume and can be crossed higher than some other choices. Paul Kittinger has helped me with the tapered TL design, which ended up at about 71 in length, 20:1 taper, in 31 net liters, with an F3 of around 29hz, F6 around 24hz and F10 of 19hz. The slot output to the TL is in the back. The RSS265 is front rather than down firing, for a little more traditional look, but should be omni for most, maybe all of its effective range, since it is crossed over at about 180hz. The sub driver is placed 14 along the TL, about 20% from the end.

I wanted to keep it as a passive design on the MTM section. For now Im using 240w PE plate amps, that have a variable crossover of up to 180hz with a 24db/octave low pass slope to low pass the RSS265. The passive crossover for the MTM section includes a high pass to the RS150-4s (in series) and then a crossover to the front firing RS28 at 1560hz, all with approximately 4th order acoustic slopes.

All drivers are physically positioned to be time aligned on a radius from a 37" ear height, with a 12' distance to the listening position.

So, how does it sound? Lets say Im very, very pleased. It is the best speaker Ive built or owned so far. The low end is very deep and clean and does not seem to excite room modes to the same degree as my previous sealed 12 stereo sub bins. The driver integration is excellent and the presentation is very smooth. I worked very hard to bet the RS-150s and RS28 to match phase as closely as possible through their pass band. The vertical and horizontal off axis performance is excellent and the soundstage is very wide and deep. I believe that the transition from omnidirectional low and midranges to direct firing tweeter has the benefits of the large omni soundstage, yet provides excellent imaging.

Attached are some photos of the almost complete project, some as-built frequency response measurements on and off the horizontal and vertical axis as well as individual TL terminus, driver and reverse null measurements. The finish is Santos Rosewood veneer in high gloss with high gloss black on the horizontal elements. I hope this is not too big a post and images!

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
__________________
Dan N.
  Reply With Quote
Old 9th October 2007, 03:08 PM   #2
diyAudio Member
 
Join Date: Jan 2006
Location: Indiana
The last image was cut off, so here it is, the plus vertical off axis measurement.

Click the image to open in full size.
__________________
Dan N.
  Reply With Quote
Old 9th October 2007, 03:40 PM   #3
diyAudio Member
 
Join Date: Mar 2006
Location: Bucharest
Wow ! Looks really impressive !

How is your room setup and where do your omnis sound best ?
  Reply With Quote
Old 9th October 2007, 03:47 PM   #4
diyAudio Member
 
Join Date: Jan 2006
Location: Indiana
My room is about 15'w x 20' deep, with steeply vaulted ceilings from the end of the room the speakers are in over about 12' of that 20' depth. The speakers are about 3' out from the front wall and 3-4' from the side walls. It is a somewhat open floor plan and this room opens up into other rooms as well. This is our major living area and and they are used for HT and music.
__________________
Dan N.
  Reply With Quote
Old 9th October 2007, 07:42 PM   #5
diyAudio Member
 
sdclc126's Avatar
 
Join Date: Jan 2005
Location: San Diego, CA
Beautiful build Dan! I'm familiar with the Daytons so I know the speakers sound great. I love to see "unconventional" designs, but more than that your speakers look like something one would find in a boutique - the finish and detail are spectacular - bravo!!
__________________
Soft Dome
  Reply With Quote
Old 9th October 2007, 07:49 PM   #6
diyAudio Member
 
Join Date: Jan 2006
Location: Indiana
Thanks!

An intereting aspect of the omni designs where you are listening 90 off axis to the drivers, as you are here with the RS150-4's, is that their break up modes and distortion profiles also measure well down in comparison to on axis applications of the same driver since the driver naturally rolls off as you move off axis. In other words, I believe they sound better and are easier to handle in the crossover in this applciation than they are in a typical monopole application.
__________________
Dan N.
  Reply With Quote
Old 9th October 2007, 08:28 PM   #7
diyAudio Member
 
sdclc126's Avatar
 
Join Date: Jan 2005
Location: San Diego, CA
Yes that makes sense - break-ups at the higher frequencies will not be as noticable off axis - makes for some interesting experimental potential for metal drivers.

Couple of questions - do you have a schematic of the crossover? I understand it's 4th order but did you notch the woofers too? Or with the natural off-axis attenuation did you find this unnecessary?

Also, how did you arrive at using two midwoofers, and have them facing eachother? I'm wondering if this arrangement might provide some kind of complimentary lensing effect, although they may be too far away from eachother for this to work. Or was it simply to help compensate for the loss of efficiency inherent in omni designs?
__________________
Soft Dome
  Reply With Quote
Old 9th October 2007, 09:45 PM   #8
diyAudio Member
 
Join Date: Jan 2006
Location: Indiana
Here are a few more images. The crossover, which also includes a high pass to the RS150-4's, the measured impedance and impedance phase and the measured frquency response with the phase shown. The phase tracks very well from around 400hz through 2.7khz (see the red, black and blue phase lines). The purple phase line represents the phase with the reverse null at the xover point.

It's a pretty standard LR crossover, 4th order acoustic, not electrical, with a zobel on the RS150-4's, but it attenuates the woofer breakups by 40-45db .

The reason for two drivers is primarily due to losses from your listening axis being 90 off the drivers axis and alos due, I believe, to the fact that they are really playing in 4pi space throughout their range rather than 2pi for part of the range. The woofer firing at each other in order to better integrate them with the tweeter. The output is much like a single driver in many ways, IMO. The distance between them is quite important and was subject to a lot of testing in this and my prior omni project. Get them to close together and you start getting peaks and valleys created by interactions between the baffles and drivers. Get them too far apart and they won't sound as integrated. They are 9.5" apart, which is actually about 1" closer than would be practical with these drivers on a traditional flat baffle, so they should integrate better for that reason alone. I have not found any lobing to occurr vertically or horizontally off axis in my measurements.


Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
__________________
Dan N.
  Reply With Quote
Old 9th October 2007, 11:34 PM   #9
diyAudio Member
 
sdclc126's Avatar
 
Join Date: Jan 2005
Location: San Diego, CA
Hope this is more of a sidebar than a thread hijack, because it's on the same topic - but given your experience with this type of design, perhaps you could give me some feedback on an idea of mine -

I have envisioned a dual woofer "omni" also, but with each mounted at 45 instead of horizontal, and with one front firing and the other rear firing. They would be mounted directly opposite eachother. The tweeter could be mounted in between the woofers, in its own little baffle similar to yours, on the top of the cabinet, or perhaps in the cab below the front woofer.

Perhaps the effect would be something of an omni/bipole hybrid?
__________________
Soft Dome
  Reply With Quote
Old 10th October 2007, 12:08 AM   #10
diyAudio Member
 
Join Date: Jan 2006
Location: Indiana
If I follow your description correctly the potential problem I see with any front to back omni woofer design is how do you get the phase to match? If wired out of phase, will they cancel each other out if they are too close together? If wired in phase, How will they be able to integrate with each other and the tweeter, since all three drivers are at a significantly different distance from the listening position?

I'm not saying it won't work, but I'm skeptical that the phase match between the two woofers and the woofers and the tweeter could be overcome without either a digital delay element added or a complex passive ladder delay network. You might want to experiment with that concept with some inexpensive drivers before sinking a lot into it.

My omni designs so far have been very careful to have the drivers VC's time aligned physically to the listening position to ensure that this is not an issue.
__________________
Dan N.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
First project complete prezden Subwoofers 9 15th January 2009 11:14 PM
DIY Project 27 Complete DeadSpeaker Swap Meet 1 24th November 2008 08:16 PM
My omnidirectional project. Acoustic Absorb Multi-Way 27 17th May 2007 06:28 PM
Asking for PLH complete project Jay Pass Labs 4 6th October 2005 12:24 PM


New To Site? Need Help?

All times are GMT. The time now is 02:05 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2