I don't have specs to post. I don't have the driver to measure. There are a few issues at play here.
First, SI has never been very concerned with providing proper specs for their products. They often measure a prototype driver, then guess at what the specs will be for the production driver once they make changes and post that guess as a spec. And then never change it even after the production units are manufactured and (presumably) measured. They exaggerate xmax by looking at only the Klippel measured Bl graph and ignoring all the other factors that limit xmax, factors that very high xmax drivers typically don't do well with, factors that would limit xmax to much lower values if they were considered. It's also pretty well known at avsforum that the d2 and d4 versions of this driver don't have the same t/s specs and have different enclosure requirements even though SI published specs for only one version. Basically SI is not at all interested in providing accurate t/s specs.
Second, the fact that a different factory is building the driver doesn't have much to do with anything unless it's implied that different parts are being used, and that is IMO not implied at all. I assume these drivers use all off the shelf parts, that's why it's possible to sell them at this price point. The only part that might be custom made is the voice coil and even so there's no reason a different factory couldn't make them the same. That means there's only two jobs the factory is responsible for - winding the coil and gluing the parts together. If there's a considerable change in t/s specs from that there's a big problem with at least one of the factories.
Third, Mark thinks it is appropriate to measure t/s specs inside a car and I don't. I don't care if all the doors and windows and trunk are open or not. T/s parameters are derived directly from an impedance curve. Basically anything in the general area of the measurement can change the impedance curve. Rigid boundaries and cavities like those found inside a car definately can affect the impedance curve. Simply put, I do not trust Mark's t/s measurement. He's clearly stated what he thinks of my opinion but let's not forget that even seasoned professionals are not immune to very silly mistakes - his first set of parameters was wildly inaccurate, so much so that just looking at the numbers was enough to immediately know they didn't make sense and he defended them a couple of times before reconsidering. The thing is this - if the impedance curve is wrong all the derived specs will be wrong. It might seem like they make sense because they shift in complimentary ways - ways that seem to make sense - but garbage in = garbage out. You can try to validate a 843 g MMS by saying the Bl is also higher, and higher Bl means a larger coil (and he did try to validate it in exactly this way) but as we know, both his measured Bl AND MMS were wrong. If you don't have an accurate impedance curve you won't have accurate specs. Simple as that.
IMO the best data we have at this point is choosing either the published specs or the specs measured by data-bass. Even though the data-bass measurement is a prototype version of the driver it's pretty close to the published specs and there's no indication that any parts were actually changed between the prototype and the production units.
And finally, as I've mentioned a couple of times, you won't get an accurate sim unless you use the "large coil" tweak no matter what specs you use.
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The reason I recommended this driver in the first place was because your stated budget was $500 and you had already spent over half of it. Despite the problem of finding good specs to use for simulation purposes this driver is the budget leader. And it's easy enough to work with given the framework of the discussion several months ago. Stick it in the biggest box you have space for and port it to your desired frequency. There's not much that can go wrong in that respect.
But using this driver in a more complex enclosure is a different story. You need accurate specs for more complex enclosures. Personally I wouldn't even attempt it without measuring t/s myself. If that was not an option I'd use the data-bass measured t/s but I wouldn't make anything more complex than a ported box.
But using this driver in a more complex enclosure is a different story. You need accurate specs for more complex enclosures. Personally I wouldn't even attempt it without measuring t/s myself. If that was not an option I'd use the data-bass measured t/s but I wouldn't make anything more complex than a ported box.
JAG,
Yes. I recall that you were the one who pointed me to that SI HT18. And I believe it was a good choice for the ported triangular cabinet that tb46 designed. It does put out low sounds at greater SPL than the larger box with the two Dayton ST385-8 15 inches speakers.
But as you and others predicted, it has been tough to project the output of those bass boxes to get the lowest sounds through the relatively small opening of the pipe chamber and out to the Sanctuary.
Hopefully, we will FINALLY get the sound engine online this Friday. Only after that will I be able to determine how well the low sounds are produced and the resulting balance of these boxes with the other sounds. So, I'm currently looking ahead and playing "WHAT IF" for a solution that might not even be needed.
I toyed with the idea of Infinite Baffle drivers right above that opening (4). But cutting a hole through the plaster and lathe ceiling would be very messy. We'd have to remove all the pipes and cover everything in there to keep the dust from creating a huge problem. That would require lots of labor by our pipe tech and be very expensive. So I've rejected that plan.
I do have one area near the shades opening that would be suitable for another bass box. But a limitation is that it must be relatively narrow - on the order of no more than 18 ior 19 nches. Otherwise, there isn't room for people to have access between it and some pipes on the other side of the aisle in the pipe chamber. This is required for periodic tuning the pipes.
Here is one of my poor drawings to show what I mean.
The width of this area could be as much as 30 to 36 inches. And I think a height of 72 inches would fit. What I'm thinking is that the driver(s) could be placed on one of the 30 inch walls with a horn design (of some type) where the opening would come out right at the shades. Having the lowest notes of the organ exit right at the shades SHOULD maximize the amount of sound that could enter into the Sanctuary.
You'll recall that I'd made a decision early-on to have the speakers play at full volume as the pipes do to make voicing and balancing easier. The division of channels coming out of the amps have been setup with that in mind. The two current bass boxes are setup that way.
Some have suggested that I put another bass box out in the Sanctuary. But the sound engine allows me to make use of the organ volume pedal to adjust sounds for any channel - or to have it play full volume. But I cannot do both. (The volume pedal is called the Expression or Swell Pedal.)
So if I put a box in front of the shades for the low channel controlled by the expression pedal, the control would also apply to the two boxes in the pipe chamber. And the volume on those is already going to be adjusted by opening and closing the shades.
So I'm still leaning towards having all sound sources behind the shades.
I'm not focused on any particular driver yet. I only mentioned the SI HT18 because I'm familiar with it. It seems to have good bones for a ported box.
As you point out, some type of horn may need a different driver.
Bach On
Yes. I recall that you were the one who pointed me to that SI HT18. And I believe it was a good choice for the ported triangular cabinet that tb46 designed. It does put out low sounds at greater SPL than the larger box with the two Dayton ST385-8 15 inches speakers.
But as you and others predicted, it has been tough to project the output of those bass boxes to get the lowest sounds through the relatively small opening of the pipe chamber and out to the Sanctuary.
Hopefully, we will FINALLY get the sound engine online this Friday. Only after that will I be able to determine how well the low sounds are produced and the resulting balance of these boxes with the other sounds. So, I'm currently looking ahead and playing "WHAT IF" for a solution that might not even be needed.
I toyed with the idea of Infinite Baffle drivers right above that opening (4). But cutting a hole through the plaster and lathe ceiling would be very messy. We'd have to remove all the pipes and cover everything in there to keep the dust from creating a huge problem. That would require lots of labor by our pipe tech and be very expensive. So I've rejected that plan.
I do have one area near the shades opening that would be suitable for another bass box. But a limitation is that it must be relatively narrow - on the order of no more than 18 ior 19 nches. Otherwise, there isn't room for people to have access between it and some pipes on the other side of the aisle in the pipe chamber. This is required for periodic tuning the pipes.
Here is one of my poor drawings to show what I mean.
The width of this area could be as much as 30 to 36 inches. And I think a height of 72 inches would fit. What I'm thinking is that the driver(s) could be placed on one of the 30 inch walls with a horn design (of some type) where the opening would come out right at the shades. Having the lowest notes of the organ exit right at the shades SHOULD maximize the amount of sound that could enter into the Sanctuary.
You'll recall that I'd made a decision early-on to have the speakers play at full volume as the pipes do to make voicing and balancing easier. The division of channels coming out of the amps have been setup with that in mind. The two current bass boxes are setup that way.
Some have suggested that I put another bass box out in the Sanctuary. But the sound engine allows me to make use of the organ volume pedal to adjust sounds for any channel - or to have it play full volume. But I cannot do both. (The volume pedal is called the Expression or Swell Pedal.)
So if I put a box in front of the shades for the low channel controlled by the expression pedal, the control would also apply to the two boxes in the pipe chamber. And the volume on those is already going to be adjusted by opening and closing the shades.
So I'm still leaning towards having all sound sources behind the shades.
I'm not focused on any particular driver yet. I only mentioned the SI HT18 because I'm familiar with it. It seems to have good bones for a ported box.
As you point out, some type of horn may need a different driver.
Bach On
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If I'm reading you right, the box can be 72" x 36" x 19", 28.5 cubic feet gross maximum.
If you confirm the dimensions, one could design something that would fit the space you can allocate, rather than suggesting things that won't.
That said, adding more of what you have, adjusted to fit in the space available would probably better than a relatively small (for the desired Fc) tapped horn.
As I think I mentioned a couple of times now this project has spiraled into something a lot larger than your original query of how to make your existing box better. From the beginning (after answering your original question) it was noted that this should be viewed as an end game, not adding and adding more and more stuff. My thoughts at that point were to use ALL your existing space with 8 of the SI drivers in ported boxes and move all the other higher frequency boxes somewhere else.
I would be wary of putting sub boxes in different locations if the locations are more than 1/4 wavelength apart at the crossover frequency, this is going to necessitate delay and possibly other dsp so they are not fighting each other. Even with dsp it won't be as good as keeping them close, this is large room acoustics, not small room acoustics.
There are all kinds of things you COULD do if you think outside the box, but IMO the time for this type of planning was before you starting building your first sub.
For example, here's an example of another church build. It's basically an unfolded Labhorn that doesn't use a box at all, at least not in the traditional sense. It's built right into the building, floor to ceiling, and uses the existing walls, floor and ceiling as part of the box. The only thing they had to build was a single wall to define the flare within the existing building structure. This takes up relatively little space, it just pushes one of the walls in a few inches so you lose a few square feet of the room. This is very cost and space effective but it requires a very rigid existing structure (walls, ceiling and floor). This concept can also be used with a bend or two if you don't have a room that's long enough. This kind of "box" is visually benign since all you see is a wall and you can put it anywhere, even right on the stage or in the listening room if desired.
Live Sound International | Backstage Class: A Variation of the LAB Subwoofers Successfully Deployed
There's a bunch of stuff you COULD do but I'm very hesitant of throwing wild ideas out at this stage of the game because I don't have a really clear view of your building or your end goals and mixing a bunch of different concepts might not blend too well.
At this point I would strongly recommend testing what you currently have. Seal up all the leaks in the boxes, get your DI box up and running, hook everything up and start measuring and listening at various places in the pews and see what you actually have at this point. If it's good enough then you are done. If it's woefully inadequate then it might be time to start with a bigger and better plan and plan it from the start instead of planning to add more and more stuff until it's good enough.
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Here's a quick example of the previously described concept. This is a very bold example as it puts the subwoofer right in the middle of the line of sight, right on the stage. Visually it would just look like a curved wall at the back of the room but it could be large enough to build almost a full sized front loaded horn right into the existing structure without even being noticed as a piece of audio equipment at all.
That's a top down look at a SEVERAL THOUSAND LITER floor to ceiling front loaded horn with multiple drivers. Visually benign but huge. Since most of the horn is using the existing structure you only need to build the curved wall and the driver chamber. There's plenty of room for maintenance work on the drivers if needed.
Advantages to this type of "box" include the ability to make a true curved hyp/ex flare (it's easy to bend large sheets of wood) and true corner loading. Low cost since there's not much to build and you don't lose too much floor space since it's floor to ceiling and only requires one wall to be built.
This is just a concept to show how easy it can be to put a massive subwoofer right in the place you would least expect it to be acceptable. This is the type of thing you can achieve if you plan ahead. It's just one idea, there's a thousand different ways you can put big bulky stuff anywhere you want and have it fit right in. This type of thinking is IMO a lot more productive than trying to figure out how to fit huge subs in a tiny room.
An externally hosted image should be here but it was not working when we last tested it.
That's a top down look at a SEVERAL THOUSAND LITER floor to ceiling front loaded horn with multiple drivers. Visually benign but huge. Since most of the horn is using the existing structure you only need to build the curved wall and the driver chamber. There's plenty of room for maintenance work on the drivers if needed.
Advantages to this type of "box" include the ability to make a true curved hyp/ex flare (it's easy to bend large sheets of wood) and true corner loading. Low cost since there's not much to build and you don't lose too much floor space since it's floor to ceiling and only requires one wall to be built.
This is just a concept to show how easy it can be to put a massive subwoofer right in the place you would least expect it to be acceptable. This is the type of thing you can achieve if you plan ahead. It's just one idea, there's a thousand different ways you can put big bulky stuff anywhere you want and have it fit right in. This type of thinking is IMO a lot more productive than trying to figure out how to fit huge subs in a tiny room.
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Deep Throat
I promised I would publish this here. It is a compact and renamed version of my original work. WHG
I promised I would publish this here. It is a compact and renamed version of my original work. WHG
Thanks, JAG. Good analysis. Yes. I do recall that you suggested more bass drivers early on. You also suggested that we use different speakers for the upper frequencies rather than blocking up the pathway for bass sounds with our big HC12 speakers. Several people agreed with your suggestions. Some even suggested a wall of bass drivers. Nearly everyone suggested that I change my original sealed box to a ported one. I did so. And there was an improvement of output at low frequencies.
Someone on the organforum suggested a slightly different approach. He suggested removing the mid-range drivers, tweeters and crossovers from the big boxes and putting them into much smaller boxes. Each channel would get a small woofer capable of producing 64 Hertz. That's about as low as a 16 foot organ stop would need in the range of the manuals. Bass frequencies in that range wouldn't require such a large cabinet. That would reduce the size of the six boxes for the manuals significantly. He then suggested that the 6 Eminence woofers be placed in two large cabinets for reproducing the low range.
So many have agreed with your early analysis. And I did understand what you were saying.
Whgeiger. Wow. You've brought those dimensions down considerably.
Bach On
Someone on the organforum suggested a slightly different approach. He suggested removing the mid-range drivers, tweeters and crossovers from the big boxes and putting them into much smaller boxes. Each channel would get a small woofer capable of producing 64 Hertz. That's about as low as a 16 foot organ stop would need in the range of the manuals. Bass frequencies in that range wouldn't require such a large cabinet. That would reduce the size of the six boxes for the manuals significantly. He then suggested that the 6 Eminence woofers be placed in two large cabinets for reproducing the low range.
So many have agreed with your early analysis. And I did understand what you were saying.
Whgeiger. Wow. You've brought those dimensions down considerably.
Bach On
Weltersy:
If I discover that we need such a cabinet, I'm leaning towards one on the order of 72 inches High, 32 inches Deep and about 18 inches Wide. Those are external dimensions. I figure losses (motor, interior bracing, etc.) in the neighborhood of around one cubic foot. That would make for an interior volume of roughly 20 cu. ft.
JAG's observation that separating one box beyond the distance of 1/4 wave of the tuning frequency may introduce negative issues is valid.
Too, mixing a horn with ported box may introduce negative issues.
And I'm still hopeful the boxes we have may turn out to be adequate.
But I'm looking at a good potential solution that will fit if they aren't.
Bach On
20 cubic feet is not large enough for a 16 Hz Fb tapped horn to be very effective, but makes for a decent size BR.
Jag mentioned locations more than 1/4 wavelength apart at the crossover frequency are problematic, at 100 Hz that would be only 2.8 feet, at the tuning frequency (Fb 16 Hz) the distance could be 17.65 feet and still be within 1/4 wavelength.
I went back to post 24 (page 4) of this thread. tb46 suggested a T-TQWT horn based on the Stereo Integrity HT18.
I've been studying it. The dimensions are pretty much within the available physical space I've been describing.
I've been able to follow the design, though there is one space I just do not understand. I've highlighted it in blue, Oliver. It doesn't seem connected to the interior of the box. What would this space do for the design? 😕
Would any negative impact result if I turned this box upside-d, own to put the exit near to the shades opening in our pipe chamber? My thinking - limited as it is - was that this would maximize getting sounds out into our Sanctuary.
Finally, it appears from the frequency response graph that there is a hump just above 60 Hertz. My thoughts were to give this cabinet it's own amp playing frequencies below 56 - 60 Hertz. A 2nd or 3rd order crossover system might cause a 12 dB roll-off from that crossover point into that humped area. So this sub would start to "wake-up" as the SPL of the others was diminishing. 🙄
Whacha think?
Bach On
The space I'm describing for an horn is a nominal 7 to 8 feet from either of our other two subs.
BO
That path length difference and the small exit from a small room to a large room, plus the phase differences between a TH and BR make any outcome difficult to predict, other than it is unlikely that the output will be equal to the sum of the disparate parts.
Hi Bach On,
Post #391: "...I went back to post 24 (page 4)...What would this space do for the design?...Would any negative impact result if I turned this box upside-d...
The picture shows part of the drawing from Page 4, Post #39, as it says in that post: "... there is still a bit of wasted volume...". This was the leftover space after finishing the fold as per Hornresp length. You have to stop somewhere 🙂. I have not had time to try to rework this design to fit with the new (Mark's) T/S parameters, and I'm not sure when I'll find time to look at this in any detail again, or to apply the JAG Fix to the design in Hornresp, etc..
I'll be out of the country for about two weeks starting the middle of next week, and my friendly co-workers found it necessary at the end of last month to present me with an additional unnecessary three weeks worth of equipment damage to repair that I'm just now getting to the end of.
Bjorno describes the T-TQWT enclosures as pressure sources (I hope I got this right). This enclosure should be very forgiving to the location inside the pipe chamber as it's purpose is to load the chamber w/ long wavelength sound waves (3.5 to 21.5 meters, or so). What any of this means will have to be evaluated in situ. Same w/ the crossover(s), and playing together w/ the other boxes.
As you said in Post #383: "...Hopefully, we will FINALLY get the sound engine online this Friday. Only after that will I be able to determine how well the low sounds are produced and the resulting balance of these boxes with the other sounds..."
Maybe you'll find that once you got the amplification sorted out, and the signal corrected, that the current two boxes are sufficient? (At 16Hz more is always better 🙂 .)
Regards,
Post #391: "...I went back to post 24 (page 4)...What would this space do for the design?...Would any negative impact result if I turned this box upside-d...
The picture shows part of the drawing from Page 4, Post #39, as it says in that post: "... there is still a bit of wasted volume...". This was the leftover space after finishing the fold as per Hornresp length. You have to stop somewhere 🙂. I have not had time to try to rework this design to fit with the new (Mark's) T/S parameters, and I'm not sure when I'll find time to look at this in any detail again, or to apply the JAG Fix to the design in Hornresp, etc..
I'll be out of the country for about two weeks starting the middle of next week, and my friendly co-workers found it necessary at the end of last month to present me with an additional unnecessary three weeks worth of equipment damage to repair that I'm just now getting to the end of.
Bjorno describes the T-TQWT enclosures as pressure sources (I hope I got this right). This enclosure should be very forgiving to the location inside the pipe chamber as it's purpose is to load the chamber w/ long wavelength sound waves (3.5 to 21.5 meters, or so). What any of this means will have to be evaluated in situ. Same w/ the crossover(s), and playing together w/ the other boxes.
As you said in Post #383: "...Hopefully, we will FINALLY get the sound engine online this Friday. Only after that will I be able to determine how well the low sounds are produced and the resulting balance of these boxes with the other sounds..."
Maybe you'll find that once you got the amplification sorted out, and the signal corrected, that the current two boxes are sufficient? (At 16Hz more is always better 🙂 .)
Regards,
Enjoy your trip. Sorry about the damaged equipment.
Once again - a delay from Friday (today) until Monday. But soon. Then - and only then - will we hear what we have.
So the space I highlighted serves no "crucial" purpose. I get it.
I guess I just don't quite understand how crucial the T/S data is to the specific design of the T-TQWT box. But your T-TQWT design does look like it would fit our available space.
Your previous design on the Triangular box was good. So I just jumped to the conclusion that this one would be good too. I'm not pressuring you for work.
Thanks!
Bach On
P.S. I received suggestions in another thread on an amplifier for bass that doesn't have big roll-off for signals below 20 Hertz. Several suggested the older Crown MA2400. Some wrote that these amps - no longer being made - will play down to 5 hz. Bad news - would have to buy used; they are very heavy; and the fan system seems to be loud. But it would decrease reliance on hacked equipment like that Rolls pre amp. And yes. I caught the subtle reminder. ;-)
Once again - a delay from Friday (today) until Monday. But soon. Then - and only then - will we hear what we have.
So the space I highlighted serves no "crucial" purpose. I get it.
I guess I just don't quite understand how crucial the T/S data is to the specific design of the T-TQWT box. But your T-TQWT design does look like it would fit our available space.
Your previous design on the Triangular box was good. So I just jumped to the conclusion that this one would be good too. I'm not pressuring you for work.
Thanks!
Bach On
P.S. I received suggestions in another thread on an amplifier for bass that doesn't have big roll-off for signals below 20 Hertz. Several suggested the older Crown MA2400. Some wrote that these amps - no longer being made - will play down to 5 hz. Bad news - would have to buy used; they are very heavy; and the fan system seems to be loud. But it would decrease reliance on hacked equipment like that Rolls pre amp. And yes. I caught the subtle reminder. ;-)
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Hi Bach On,
Bjorno has been advocating the use of the T-TQWT, and the ones that have been build (that I know of) have been well received.
One other way of getting amplification is to provide individual plate amps to your cabinets. This would provide you w/ level, phase and crossover controls for each speaker, and should give you a lot more flexibility and adjustability to match speakers and room(s). Here is just one example:
Yung SD500-6 500W Class D Subwoofer Plate Amplifier Module with 6 dB at 25 Hz
This one has a little bass boost option centered @ 25Hz, which would imply that it has extension well below 15Hz, and that the bass boost can be fiddled with. (He says, not knowing what he is talking about.)
Here is another one that has a built-in parametric EQ and a little more power:
http://www.parts-express.com/dayton-audio-spa1000-1000w-subwoofer-plate-amplifier--300-809
You would still have to find out where the -3dB low frequency point is, and if such an amplifier is suitable for constant duty/Pa applications.
Regards,
Bjorno has been advocating the use of the T-TQWT, and the ones that have been build (that I know of) have been well received.
One other way of getting amplification is to provide individual plate amps to your cabinets. This would provide you w/ level, phase and crossover controls for each speaker, and should give you a lot more flexibility and adjustability to match speakers and room(s). Here is just one example:
Yung SD500-6 500W Class D Subwoofer Plate Amplifier Module with 6 dB at 25 Hz
This one has a little bass boost option centered @ 25Hz, which would imply that it has extension well below 15Hz, and that the bass boost can be fiddled with. (He says, not knowing what he is talking about.)
Here is another one that has a built-in parametric EQ and a little more power:
http://www.parts-express.com/dayton-audio-spa1000-1000w-subwoofer-plate-amplifier--300-809
You would still have to find out where the -3dB low frequency point is, and if such an amplifier is suitable for constant duty/Pa applications.
Regards,
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Hi Bach On,
If you have room somewhere for a 5'x5' riser you could build a PPSL T-TQWT, here is a sketch 🙂 :
Regards,
If you have room somewhere for a 5'x5' riser you could build a PPSL T-TQWT, here is a sketch 🙂 :
Regards,
You're just full of ideas. But I don't think our space would accommodate this big boy.
Even if it isn't perfectly matched to that SI HT18, I think your earlier T-TQWT design is more within the scope of our available space (and shape). But I would need to have the exit opening at the top, instead of the bottom. Frankly, I can't see how that would significantly change the sounds coming from the box.
I know I've written this before, but I'm still wanting to have enough bass capability that none of the amps or boxes have to be run too hot. I'm just concerned this will produce distortion. I'd like to have enough reserve SPL that I may say, "OH wow! I need to cut that bass way down." 😀
Maybe Santa would bring me a used Crown MA2400 in good condition for Christmas to power it. (I just don't quite trust Plate Amps for this kind of setup. And it adds another level of complexity for turning it on and off remotely when the organ is switched on.)
I'll keep your design on my short-list for solutions if it turns out our bass cabinets aren't quite enough. That would probably be a good winter project. Then we could surprise everyone at Easter. 😱
BO
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