New Open Baffle Concept

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I think the point here if someone wanted to disprove his claims, is to spend the $10 for the plans and make it exactly as designed.. That would be the best way to see what this is all about and provide accurate insight to his design.. If it doesn't perform or satisfy to how it was described, then you actually have the same model to report about, and that would be more accurate science relating to this specified design..

The manufacturing errors were and are #1 a thumb and finger print in the transformer paint (cosmetic) #2 The volume knob all the way off is in the 2 oclock position and all the way up in the 12 oclock position rather than 7 and 5 etc (mechanical, functional)

All the rest is superb :)
 
It was Tekton that was mentioned. They've got that kinda odd OB+box where the second driver is mounted 90 degrees from the main, pointing up, helping out with BSC somehow. I like that one two. Who's available out there to make descions about what hairbrained schemes I can and cannot waste my time trying to copy? Stop me before I build again...
 
I think the point here if someone wanted to disprove his claims, is to spend the $10 for the plans and make it exactly as designed.. That would be the best way to see what this is all about and provide accurate insight to his design.. If it doesn't perform or satisfy to how it was described, then you actually have the same model to report about, and that would be more accurate science relating to this specified design..

The manufacturing errors were and are #1 a thumb and finger print in the transformer paint (cosmetic) #2 The volume knob all the way off is in the 2 oclock position and all the way up in the 12 oclock position rather than 7 and 5 etc (mechanical, functional)

All the rest is superb :)
I got the plans and will build the ZOB as described using the recommended driver. I'll also measure the driver in free air, in the baffle (with open and closed slot), the port and the complete speaker in near field and in my listening position. And sure the driver also needs a few hundred hours to perform well. So'll also comment the sound of the design.
Stay tuned.
 
Hi fwater, just_a_guy is correct. A higher-Q driver like the Betsy or B200 would be way more suitable for OB than the FE207E.

It's cool that the guy is trying to invent something. But it seems to combine the _disadvantages_ of OB and resonant enclosures.

Are we sure that the action is the backwave moving across the top of the port? It seems to me (and from his own measurements) that the coupling is largely through the enclosure itself.
 
I think the point here if someone wanted to disprove his claims, is to spend the $10 for the plans and make it exactly as designed.. That would be the best way to see what this is all about and provide accurate insight to his design.. If it doesn't perform or satisfy to how it was described, then you actually have the same model to report about, and that would be more accurate science relating to this specified design..

You don't have to build it to know that it is just not possible to get 99 db/1w/1m from the drivers that are used. That is a fact. And 3 db is not a small stretch. As to the other claims, I can't absolutely disprove them at this time but I'd bet money against them.
 
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Yeah I know, when I read the 99db figure it even raised my eyebrows, and I'm not a speaker designer or physicist by any stretch of the imagination ... I would love to have a pair of cabs that are simple and 99+ db efficient though lol , and so I look elsewhere.. :)
 
I certainly don't need another experimental project taking up space, but that won't stop me. It stands to reason that if he is getting enough sound output down low with such a low Q driver that it could only get better with a lower mass corner (is that the right statement in this case?). Dammit, I'll do it. Any suggestions where to start? Without any other ideas, I suppose an enclosure suited to generate reasonable bass if the speaker were in a standard arrangement is a good place to start looking. Someone earlier on said that there was another commercially available system that used this unbox principle. Any links?

If it's just an experiment you only need to make one. It should be pretty easy. Take any fullranger ported box that you already have on hand - as you speculate, it should be just about the right size, at least for initial experimentation. Take the driver out of the ported box. Install it on a narrow baffle. Take the ported, driverless box and cover up the driver hole. Install an opening (or port) in the driver hole cover. Now it's a helmholtz resonator with an extra opening. Simply place the opening in the resonator near vicinity of the narrow ob. Listen and measure. Adjust the opening and port accordingly. If you can't get a reasonable tuning, try tapering one or both of the ports. Also, like a guitar, if the box is big enough and you don't need very low bass performance you could plug the port right up and not use helmholtz resonance at all. If necessary, you might need to adjust the size and shape of the baffle, and driver position on the baffle, but probably not much. Once it's tuned, if there's too much bass, reduce the size of the double ported box. If there's not enough bass the ported box needs to be bigger.

That's pretty simple and should give you plenty of info, enough to build a final version.
 
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Having never built any open baffle speakers you might take the following with a large pinch of salt ;)

Looking at that design i think it could be done better :D

The slot gradually widens as it drops down into the lower enclosure, this should spread any resonances - so far so good. It's the coupling to the driver that looks suspect to me, far better to have the variable slot all the way around the periphery of the driver rather than one edge i'd have thought? That way you actually might get some useful damping of the driver cone itself, whilst still leaving the speaker as an open baffle.

If anyone doesn't comprehend my madness i'll attempt a crude drawing :eek:

Bests, Mark
 
Hi fwater, just_a_guy is correct. A higher-Q driver like the Betsy or B200 would be way more suitable for OB than the FE207E.

It juat so happens that I have a Betsy that I am currently using OB with no helper woofer. It is this close to having acceptable bass output in a low and wide setup (24"x36", long story as to why).

It's cool that the guy is trying to invent something.

It is cool. I just can't resist taking pokes at his live broadcast mess and the constant contradictions...

Are we sure that the action is the backwave moving across the top of the port? It seems to me (and from his own measurements) that the coupling is largely through the enclosure itself.

This is something that I considerred, but I fall to one side by saying the coupling is largely through the mouth(?) of the unbox, with reinforcement communicated through panel vibrations. It makes me wonder what kind of material I want to experiment with. Probably not MDF or the like because it is just, well, ya know, MDF. But I hate scrapping boxes that I'm only tinkerring with when they're made out of nice ply. Maybe those medium-cost "dimensioned lumber" panels you see at Home Depot, the ones cut to certain widths and lengths, packaged in plastic? They come in all sorts of wood types, but poplar is relatively inexpensive and seems like it might be good at transmitting vibrations that we minght desire...
 
If it's just an experiment you only need to make one. It should be pretty easy. Take any fullranger ported box that you already have on hand - as you speculate, it should be just about the right size, at least for initial experimentation. Take the driver out of the ported box. Install it on a narrow baffle. Take the ported, driverless box and cover up the driver hole. Install an opening (or port) in the driver hole cover. Now it's a helmholtz resonator with an extra opening. Simply place the opening in the resonator near vicinity of the narrow ob. Listen and measure. Adjust the opening and port accordingly. If you can't get a reasonable tuning, try tapering one or both of the ports. Also, like a guitar, if the box is big enough and you don't need very low bass performance you could plug the port right up and not use helmholtz resonance at all. If necessary, you might need to adjust the size and shape of the baffle, and driver position on the baffle, but probably not much. Once it's tuned, if there's too much bass, reduce the size of the double ported box. If there's not enough bass the ported box needs to be bigger.

That's pretty simple and should give you plenty of info, enough to build a final version.

This is what I was thinking, but I would have to build one as all of my enclosures are enormous (my wife has approved of my hobby). And, pardon me if I sound arrogant, I was already thinking on how to get a better coupling of the driver to the unbox, as event horizon suggests. My first thought was something that would end up looking like the double-mouthed BVRs we all know so well but without the mouths. Hey, why would it have to be without the mouths? Hmmm...
 
Just,
A person could use up more material and spend more money in the end using that approach, rather than just spending the small 10 dollar fee to get the plans in the first place etc. Just saying :)

No, you just use a ported box you already have, a small piece of wood to cover the driver hole, and a few lengths of pipe. I don't know about you but I always have that stuff on hand. If I were inclined (and I might be in the future) it wouldn't cost me a penny.
 
I think the "Unbox" is a box in appearance but is more of a placebo.. How about the ''Placebox'' = placebo + box or ''Placebo Box'' :)

Placebox= you just place a box under the driver and tinker away till you get the sound you want lol ;)
 
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This is what I was thinking, but I would have to build one as all of my enclosures are enormous (my wife has approved of my hobby). And, pardon me if I sound arrogant, I was already thinking on how to get a better coupling of the driver to the unbox, as event horizon suggests. My first thought was something that would end up looking like the double-mouthed BVRs we all know so well but without the mouths. Hey, why would it have to be without the mouths? Hmmm...

The appeal (or at least the marketing slant) is that the loose coupling is an advantage. After all, guitars work fine. I wouldn't worry about it.

If you want to make a massive horn instead of a helmholtz chamber that's up to you, but it's not necessary and I'm not sure it would work the way you think. If you close the Sachiko's dual horn mouths, the large end (that used to be the terminus) would end up being the throat and you would probably end up with a massive tapered tl with an incredibly low tuning. So slow down cowboy, start small.
 
Interesting design if it really works and provides enough bass to justify the build. Looking closely at the drawing on the part 4 article, it seems there might be more going on here. It appears that the bottom of the baffle board doesnt solidly attach to the box (gap), hence the addition of the reinforced lip. Maybe attached with flexible adhesive? If this is the case, does the baffle act as a cone since it can freely vibrate? Also, the port under the driver expands inside the box so some sort of horn loading thing also going on too? Just some quick observations and queries.

amt
 

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ok as I was so keen on my own open baffle project i am ready to try this test, not for bass extension etc. but for what i perceive as missing harmonics. Here is the photo...... what a lucky fit. Had these in the shed pair... of old reynauds ....had a gap already on the top for a tweeter and the port at the back was for the crossover. Unfortunately both the f5 and oto are both under testing, so might not get round to testing them till Sunday.
 

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Looking closely at the drawing on the part 4 article, it seems there might be more going on here. It appears that the bottom of the baffle board doesnt solidly attach to the box (gap), hence the addition of the reinforced lip.

But there's nothing to indicate that the baffle does not attach solidly to the side pieces. Being loosely fastenned to the botton only would not allow for too much free vibration. Or would it be just enough...?

Also, the port under the driver expands inside the box so some sort of horn loading thing also going on too?

Not horn loading, but spreading out of the peak resonance, theoretically (and probably actually) flattening out a sharp spike into a wider and flatter hump. Air flowing past the mouth will tend to excite a note closer to the original driver's sound rather than a single pipe hum. Audio Joy looks like a good candidate for feedback since he is quite familiar with his setup as evidenced by his long build thread and listenning impressions. If there's any positive changes in sound, then I'm on board.

If we're going with placebox (and yes, I know what placebo means, it just a good sarcastic play on whether this thing works or not), can we spell it "placeebox"? The other way just looks like place box.
 
You guys can pick whatever name you want :) It is sort of a placebo though, in that it is a box providing some bass with no driver.. Like a pill relieving a headache with no medicine :) All your really doing is placing a box and adjusting a slot valve to the box to adjust the timber as seen in the paper and release pic.. Must have taken some time to figure it all out to work properly, he has had it ongoing for sometime now.. I'll eagerly await Nelson Bass's build as he is doing it exact from plans with the same drivers, so will be interesting to read about...
 
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