??? That’s what I said; horn, and preferably WG, front/rear loaded dipoles provide superior performance compared to a simple ‘H’ frame OB and makes an elegant ‘statement’ to boot!
Yes, John’s goal was better directivity control down into the upper bass/lower mids without a ‘boxy’/horn sound, i.e. the best of both short WG and OB.
Well, without anything to compare to, no way to know how well it will work; I just happen to notice it had a too small a throat area [St] for dual 416s and even a little too small for dual 515s due to its need for a wider HF loading BW.
In retrospect though, the open top may have enough end correction/pressure loss to offset it enough to keep it from obviously peaking in the lower mids due to excessive driver/horn overlap.
Anyway, hope it works out, it would be a shame to have to insert a bunch of EQ or worse, scrap them.
GM
Yes, John’s goal was better directivity control down into the upper bass/lower mids without a ‘boxy’/horn sound, i.e. the best of both short WG and OB.
Well, without anything to compare to, no way to know how well it will work; I just happen to notice it had a too small a throat area [St] for dual 416s and even a little too small for dual 515s due to its need for a wider HF loading BW.
In retrospect though, the open top may have enough end correction/pressure loss to offset it enough to keep it from obviously peaking in the lower mids due to excessive driver/horn overlap.
Anyway, hope it works out, it would be a shame to have to insert a bunch of EQ or worse, scrap them.
GM
Thanks....have you got a pic or drawing of what the front/rear dipole might look like...?
Remember, this is all a bit trial and error....it's how I work...I like testing/building things.
In fact, I'm currently building a 620 Altec bass cabinet while I continue on the OB/multi-way horn system project. I figured the 620 is probably the best bass for the 416, and an easy build. Using 19mm Euro Birch ply. I posted a thread on the Altec forum and asked about cabinet bracing...got no reply. Do you have a veiw on the bracing of this cabinet? The original design was very light on. I was thinking of adding two, or possibly three 'shelf' braces, touching all four surfaces.
Kindly
Remember, this is all a bit trial and error....it's how I work...I like testing/building things.
In fact, I'm currently building a 620 Altec bass cabinet while I continue on the OB/multi-way horn system project. I figured the 620 is probably the best bass for the 416, and an easy build. Using 19mm Euro Birch ply. I posted a thread on the Altec forum and asked about cabinet bracing...got no reply. Do you have a veiw on the bracing of this cabinet? The original design was very light on. I was thinking of adding two, or possibly three 'shelf' braces, touching all four surfaces.
Kindly
Glad I found your thread here as well as on Bert's site. I am closely following your progress since I am very interested in this type of implementation. Have you been able to get a rough estimate of the frequency response of the two driver OB/Waveguide you are building? I will be using Bert's Oris 150s from 200Hz on up as I do now. I currently have a set of DIY dual 15" bass bins that I use from 80-150Hz.
I just love the look and simplicity of Bert's design.
I just love the look and simplicity of Bert's design.
Hi Rudy....have we had email chats before....there's a Rudy I was talking to last year.
Bert has done some specs on the OB's, but not a lot of data to hand, sorry. He runs x4/side...so we have to consider that. I trust his insights.
You're on with a better chance using his drivers.
Bert has done some specs on the OB's, but not a lot of data to hand, sorry. He runs x4/side...so we have to consider that. I trust his insights.
You're on with a better chance using his drivers.
We likely have corresponded before. For a while I was very interested in the Azurahorns and have also spent a lot of time with Klipsch stuff and other DIY projects.
I too trust Bert's insight into this project. His comments on the BD board seem to indicate that two 15's per side might still work. The project is too easy to do not to build a set. I hope to get on this in the coming weeks and take some measurements.
I currently have 4 Eminence Kappalite 3015LF that I will use for this.
Should be fun.
I too trust Bert's insight into this project. His comments on the BD board seem to indicate that two 15's per side might still work. The project is too easy to do not to build a set. I hope to get on this in the coming weeks and take some measurements.
I currently have 4 Eminence Kappalite 3015LF that I will use for this.
Should be fun.
You’re welcome!
No, but it’s simple enough in concept though; design a WG with the appropriate 180 deg. mouth round over and make two of them to mount back-to-back to a central baffle. If setting on the floor, then the bottom flare can be truncated to 90 deg.
Without some experimentation, I’ve no clue how to factor in Bert’s lack of a top flare and truncated sides and stepped rear profile.
Don’t remember seeing your bracing Qs, but not too surprised, there’s been numerous threads with bracing discussed in them plus the 620 cab is small enough that most figure that Altec’s bracing is sufficient.
I’m no fan of the 620 plus there’s two versions, vertical Vs horizontal vent layout, so the bracing would be a bit different also unless you just use Altec’s.
Anyway, bracing/supporting the driver plus tying all six sides together to it is the primary goal, then breaking up any large panel areas into unequal area triangles puts the finishing touch on it. These shouldn’t go all the way to forming a corner joint as this creates hot spots. Making them ~70% of the span is sufficient.
For [ML] TL high aspect ratio cabs, the pressure wave is concentrated along its length plus we don’t want to disrupt airflow anymore than necessary, so the bracing should run parallel in these alignments and preferably offset in a golden or acoustic ratio to get the unequal areas.
The top and bottom need to be rigid plus the top needs to be massive also to both handle the pressure and provide some/all of the stability a tall cab requires and to mass load it to the floor. Heavy potted plants or similar work well and helps with any SO/WAF issues.
FWIW, I use to have cheap access to Ga. Marble and slate, so when the app demanded WAF, etc., compliance I would have massive, decorative top plates cut to suit and Velcro them on to both make them easy to remove and ensure good constrained layer damping of the top plate. Of course if spaced up off the floor, then the bottom needs the same/similar.
Nowadays I design around pre-cut pieces or make a simple mold to ‘pour’ them using Portland cement/whatever.
GM
No, but it’s simple enough in concept though; design a WG with the appropriate 180 deg. mouth round over and make two of them to mount back-to-back to a central baffle. If setting on the floor, then the bottom flare can be truncated to 90 deg.
Without some experimentation, I’ve no clue how to factor in Bert’s lack of a top flare and truncated sides and stepped rear profile.
Don’t remember seeing your bracing Qs, but not too surprised, there’s been numerous threads with bracing discussed in them plus the 620 cab is small enough that most figure that Altec’s bracing is sufficient.
I’m no fan of the 620 plus there’s two versions, vertical Vs horizontal vent layout, so the bracing would be a bit different also unless you just use Altec’s.
Anyway, bracing/supporting the driver plus tying all six sides together to it is the primary goal, then breaking up any large panel areas into unequal area triangles puts the finishing touch on it. These shouldn’t go all the way to forming a corner joint as this creates hot spots. Making them ~70% of the span is sufficient.
For [ML] TL high aspect ratio cabs, the pressure wave is concentrated along its length plus we don’t want to disrupt airflow anymore than necessary, so the bracing should run parallel in these alignments and preferably offset in a golden or acoustic ratio to get the unequal areas.
The top and bottom need to be rigid plus the top needs to be massive also to both handle the pressure and provide some/all of the stability a tall cab requires and to mass load it to the floor. Heavy potted plants or similar work well and helps with any SO/WAF issues.
FWIW, I use to have cheap access to Ga. Marble and slate, so when the app demanded WAF, etc., compliance I would have massive, decorative top plates cut to suit and Velcro them on to both make them easy to remove and ensure good constrained layer damping of the top plate. Of course if spaced up off the floor, then the bottom needs the same/similar.
Nowadays I design around pre-cut pieces or make a simple mold to ‘pour’ them using Portland cement/whatever.
GM
GM, I have been looking for some basic guidance on how large to make the throat area in Bert's model. Can you recommend some reading on the subject? If you place the WG on the perifery of the woofer diameter, would that be too large? I'm new to this whole OB/WG concept so am trying to learn some of the basics.
Thanks GM...I've added a mix of battens and wall bracing. Thread is now here.
Kind regards
http://www.diyaudio.com/forums/multi-way/232564-ideas-altec-620-bass-cabinet-bracing.html
Kind regards
http://www.diyaudio.com/forums/multi-way/232564-ideas-altec-620-bass-cabinet-bracing.html
Not really, only for regular [closed] horns which AFAIK the most popular are Harry Olson's, Marshall Leach's, Don Keele's papers and Earl Geddes for WGs.
Again, don't know how the dipole action at the top affects it.
I assume Siegfried Linkwitz is the most knowledgeable WRT OB design.
GM
Hey GM,
So it was you that steered JohninCR? I have a pic of his dipole wave guide here somewhere. Yes, he completely stopped after that and has been pursuing perpetual motion machines since I talked to him a few years ago. I was talking to Bill Woods about it and he said, "That enclosure is something called a "boffle" used in the 1940's on train stations with a widerange 8" speaker.
The idea being to radiate sound in two specific directions.
It probably give a little boost at 100Hz the way your friend is using it."
I've been intending to build a boffle like John's using a Pioneer/TAD PE-16 but have never gotten around to it.
Martin King mentioned in his H frame work that he intended to see what a "flaired" h frame front and back might do. There certainly seems to be room for exploration!
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Atilsley,
I'll post the dipole waveguide pics later. I wish I knew someone nearby that could make me a pair.
I'll post the dipole waveguide pics later. I wish I knew someone nearby that could make me a pair.
Greets!
Yes, and for the 'life of me' I couldn't remember what it was called or where I had originally seen it, but it must have been at Atlanta's long gone 'hub of the South' Terminal Station.
The other 'reference' of course is the 180 deg mounting of two or more PA horns politicians and others would mount atop their vehicle to broadcast their message as they cruised through the large city boroughs and/or small towns.
GM
Yes, and for the 'life of me' I couldn't remember what it was called or where I had originally seen it, but it must have been at Atlanta's long gone 'hub of the South' Terminal Station.
The other 'reference' of course is the 180 deg mounting of two or more PA horns politicians and others would mount atop their vehicle to broadcast their message as they cruised through the large city boroughs and/or small towns.
GM
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