I agree both the woofer and mid look like deltalites from the back - may be OEM versions for spatial audio?
If this is a reasonably accurate recording it does tell a convincing story.
Here is something I was pondering early this morning... Turning the camshell 15"ers 90 degrees....
6moons audioreviews: Ecobox Daydream
6moons audioreviews: Ecobox Daydream
The bass was so boomy in that room with the ported designs, and much cleaner with the OBs.
I am going to do a similar build. I'm just trying to work out how similar or needs to be, as space is a big issue in my 14'x13.5' lounge with a baby grand piano in it!!!
Having just re read this thread totally, for the third time, I'm taking more in. And I'm interested that Bushmeister explains that the clamshell must face forward/back because there is relatively little output to the sides, with all the advantages of lessened room reflections, and yet the makers of the ecobox daydream, gradient with their Helsinkis, etc, have turned their dipole and clamshell woofers 90 degrees with apparent success.
What am I not understanding?
Having just re read this thread totally, for the third time, I'm taking more in. And I'm interested that Bushmeister explains that the clamshell must face forward/back because there is relatively little output to the sides, with all the advantages of lessened room reflections, and yet the makers of the ecobox daydream, gradient with their Helsinkis, etc, have turned their dipole and clamshell woofers 90 degrees with apparent success.
What am I not understanding?
The Ecobox is not an open "clamshell" in the sense that has been discussed in this thread. If you look at how and where the drivers are covered, it is actually pretty similar to a ripole, and consequently the nulls are to the sides of the speakers.
The Gradient Helsinki on the other hand has the dipole null aimed in the forward direction. If I have understood the design correctly, the listener should use room boundaries and how you angle the speakers to achieve a correct balance. It's also "supposed" to work/be placed closer to the back and/or side walls than a traditional dipole (the mid and tweeter aren't dipoles BTW). At least this is how I've understood it.
^Yes, that's the way I see it too. One benefitfor sure is force cancellation. On the other hand baffle support (width) is minimal. And upper part of the baffle is too wide. Midrange "system" and tweeeter are acoustically poor as dipole, but multiple drivers will minimize distortion
One can judge esthetics of these freely... And they might sound pretty good anyway, who knows. (I don't trust 6moons reviews much)
One can judge esthetics of these freely... And they might sound pretty good anyway, who knows. (I don't trust 6moons reviews much)
Last edited:
The (very) few examples of speakers with dipole bass null aimed forward (or as a suggested option) that I can come up with are either monopoles (Celestion SL-6000 system) or cardioid/monopole (Gradient Revolution and Helsinki). I.e. designs that are less dependent on the distance from the back wall than a dipole speaker.
Interesting thread.
I am the guy featured in the YT video on post #29.
I have posted this 'clamshell' arrangement several times on this forum, and others. The main reaction was such a design would not work.
Kudos to Bushmeister for getting such a positive response on this thread! As he has said....bass never sounded so good using this technique and minimal room modes are raised. I chose an easier construction route, though, using a scaffold frame which was ordered pre-cut for under £100 delivered.
At the moment, I am experimenting with different enclosed heads as I have found certain limitations with OB design.
For bass-heads out there (like me.....I like Kraftwerk) you can reach floor shaking depths, but choice of driver is important. The fabric surround drivers are limiting, and I found inefficient, rubber surround, heavy coned, large Xmax low Fs (under 20Hz) will deliver. My driver of choice is the Dayton UM18 which has little competition in this price range.
If anyone is interested how I got to this final design (by trial & error), I have a thread here:
Baffleless Journey
I am the guy featured in the YT video on post #29.
I have posted this 'clamshell' arrangement several times on this forum, and others. The main reaction was such a design would not work.
Kudos to Bushmeister for getting such a positive response on this thread! As he has said....bass never sounded so good using this technique and minimal room modes are raised. I chose an easier construction route, though, using a scaffold frame which was ordered pre-cut for under £100 delivered.
At the moment, I am experimenting with different enclosed heads as I have found certain limitations with OB design.
For bass-heads out there (like me.....I like Kraftwerk) you can reach floor shaking depths, but choice of driver is important. The fabric surround drivers are limiting, and I found inefficient, rubber surround, heavy coned, large Xmax low Fs (under 20Hz) will deliver. My driver of choice is the Dayton UM18 which has little competition in this price range.
If anyone is interested how I got to this final design (by trial & error), I have a thread here:
Baffleless Journey
For the box guys it definetlly will not work😀 but my question: what is the technical reasoning for such’clamshell’ design. Some THD reduction vs one driver?
The reasoning behind the clam shell design is because I was not happy with the performance of conventional designs in my room.
I dont take a very technical approach.....I just suck it and see. Part of the fun! If it works, I run with it & further develop. if I doesn't, I try something else.........
The twists & turns on this journey lead me to a suspended clam-shell, or what I call 'boxer' design. Its documented on the Lenco post in my previous post.
Last edited:
Thanks for posting this!
I remember seeing your thread when I was considering OB! Now I am using single pro hi-efficiency 18" nude bass drivers on a swing and very happy with the bass...and revisiting your thread has my head spinning again. Haven't read the whole thread yet (21 pages will take me a while), but wanted to ask you:
- How high do you cross from the twin UM18 to the enclosed head? Noted that you use a first order xo before the amp feeding the enclosed head.
- What are the benefits of using two woofers facing each other vs one behind each other (like in post #15 on page 1 of your thread), beyond the former being easier to sit on a hammock?
Nice work K9vap! Thanks for reminding me of your dual slot loaded woofer idea.
Can your share where the XO point ended up at and what the intrinsic response of the dual opposed woofers was raw? If drivers are 18in we have essentially an axis symmetry boundary condition for 1/4-wave with 9in long duct. That should put the first dip at 374Hz. About a perfect match for PRVs. I made a slot loaded woofer for PRV once in 12in baffle. I got a 350Hz natural XO from rolloff of slot loaded woofer and the PRV.
Can your share where the XO point ended up at and what the intrinsic response of the dual opposed woofers was raw? If drivers are 18in we have essentially an axis symmetry boundary condition for 1/4-wave with 9in long duct. That should put the first dip at 374Hz. About a perfect match for PRVs. I made a slot loaded woofer for PRV once in 12in baffle. I got a 350Hz natural XO from rolloff of slot loaded woofer and the PRV.
Last edited:
I read through this thread and as is often the case, some (much?) was over my head. I did have a couple questions though. Does it matter if I do a back to back rather than clamshell setup? I think the back to back is aesthetically more appealing. Second question; the space between the drivers of 1" to 6" did not seem to influence results much. Can I assume the same numbers would hold when in a back to back setup?
I have read Vic's thread and these woofers are effectively in phase acoustically (out of phase electrically) meaning both cones move in the same direction backwards and forwards, they are not slot loaded. Using 2 drivers gives a 6dB increase in output for the same excursion. Theoretically the same would hold true for woofers back to back. The late Linkwitz did the mathematical modeling and testing of this 6dB increase for two drivers.
What Vic has done is remove the resonating woofer cabinet. Woofers can have huge energy transfer into cabinets that then vibrate. Hanging the drivers also removes vibration into the smaller drivers reducing Phase shifts as the small drivers move back and forth with the woofer vibration, not too much of an issue in the lower frequencies but can be significant in high frequencies where the wavelength is short. In simple terms this woofer vibration can cause frequency modulation of the high frequencies.
What Vic has done is remove the resonating woofer cabinet. Woofers can have huge energy transfer into cabinets that then vibrate. Hanging the drivers also removes vibration into the smaller drivers reducing Phase shifts as the small drivers move back and forth with the woofer vibration, not too much of an issue in the lower frequencies but can be significant in high frequencies where the wavelength is short. In simple terms this woofer vibration can cause frequency modulation of the high frequencies.
That would have been interesting to try them in push push slot loaded config. The vibrations would disappear and the distortion in the woofer suspension would be partially cancelled out. It would also buy +2dB for slot loading.
I made a slot loaded woofer with six 6.5in woofers on a U baffle. It worked very well. The PRV on top matched it perfectly.
https://www.diyaudio.com/community/threads/cheap-and-fast-ob-literally.249984/page-20
Here is the totally electronics free crossover with natural roll off for the woofers and top everything running electrically full range. Only level matching was used here.
I made a slot loaded woofer with six 6.5in woofers on a U baffle. It worked very well. The PRV on top matched it perfectly.
https://www.diyaudio.com/community/threads/cheap-and-fast-ob-literally.249984/page-20
Here is the totally electronics free crossover with natural roll off for the woofers and top everything running electrically full range. Only level matching was used here.
Last edited: