New Home for the BG Ribbons - Part 27

[Evil Twin]

Use the Force....

Use an appropriate thickness and strength baffle to contain the vibrations, and I have little doubt that you will be satisfied with the performance of your projects.





This is probably the only way to truly reduce the impact of driver vibrational effects transmitted to the panel, short of Darth Linkwitz's implementation. Remember, in his case the driver is couple to a framework to support it that does not have baffle area that can radiate sound - even if this structure vibrates- the front panel is decoupled, acting more as a waveguide.

Many challenges lie ahead of you. Consider your options carefully, if you wish to avoid disappointment. Failure is not an option....

[chasw98]

If nothing else having a gap would decouple the planars from the reactive vibrations created by the dynamic drivers shaking their section of the baffle.

Are you suggesting 2 totally independent units (one for woofers, one for planars) would be the most decouplization possible? Plus allowing one to orientate the individual units in the best position? :E :B

[chasw98]

Use an appropriate thickness and strength baffle to contain the vibrations, and I have little doubt that you will be satisfied with the performance of your projects.

As mentioned above would the ultimate reduction of interaction be separate units?

Many challenges lie ahead of you. Consider your options carefully, if you wish to avoid disappointment. Failure is not an option....

Which is why we can build with confidence knowing the power of the force is backing us up in all of our endeavours relating to 7 foot tall planar arrays? Right, Oh BLACK one?

[ThomasW]

Are you suggesting 2 totally independent units (one for woofers, one for planars) would be the most decouplization possible? Plus allowing one to orientate the individual units in the best position? :E :B

He's talking about following Linkwitz's example where the midwoofer is decoupled from the front baffle

http://www.linkwitzlab.com/frontiers_2.htm#N

http://www.linkwitzlab.com/orion-rev1.htm

Here he glues a wooden plate to the back of magnet. The plate is then attached via a bracket to the woofer cabinet.



He started off trying isolate the drivers in the Phoenix by sandwiching them between the baffle and a rear brace using foam in an attempt to decouple them from the wood.

http://www.linkwitzlab.com/m_panel.htm

[chasw98]

OK, I see now. But that seems somewhat impractical for 12 drivers in a vertical line without some serious out of the box thinking and engineering. Hmmmmm, back to the lab!

Did isolating the drivers from the baffle with foam or some material work? If it did work, what kind of material for isolation?

[ThomasW]

I'm guessing it didn't work well enough that's why he went to the glued wood block setup for the Orion.

I'm wondering if we could luck out an find a piece of steel/alu, pipe/tubing that would slip over the magnets and be held in place with construction adhesive. Weld metal rods/angle iron to the sides of the pipe. Seems like less work than fabricating a special clamp for each driver......

although someone having access to a press or larger diameter tubing bender could take 1/8" thick X 3/4" wide steel strap and make 1/2 circles with tabs on each end. Two of these would bolt together holding the magnet for each driver

[chasw98]

I'm guessing it didn't work well enough that's why he went to the glued wood block setup for the Orion.

But he still used some type of foam or other material for isolation, right?

I'm wondering if we could luck out an find a piece of steel/alu, pipe/tubing that would slip over the magnets and be held in place with construction adhesive. Weld metal rods/angle iron to the sides of the pipe. Seems like less work than fabricating a special clamp for each driver......

although someone having access to a press or larger diameter tubing bender could take 1/8" thick X 3/4" wide steel strap and make 1/2 circles with tabs on each end. Two of these would bolt together holding the magnet for each driver

I think I might know someone with access to a press/bender.

How would you hold this array of drivers up against the baffle tight enough without using the baffle for mounting. Because using the baffle for mounting would defeat the purpose of isolation, I believe. Possibly an outer "real" baffle and an inner "mounting" baffle. The inner and outer baffles could be easily isolated. I think.....

[Dennis H]

Clamping a line might not be much harder than clamping a single driver as long as you're talking about relatively light midwoofs. Crude paint sketch -- full length oak boards, spaced a magnet width apart, with bolts to suck them together. To assemble, lay it flat, drop the drivers in the holes and tighten the bolts. Use foam or felt to make sure the driver frame doesn't touch the baffle.

[chasw98]

And how might you secure the line of drivers up against the front baffle? That is the part I am trying to figure out. Along with what material to use for felt or foam.

[Dennis H]

I dunno. Maybe cut the rabbets wide enough that you could wrap wide foam weatherstripping up the side of the rabbet?

Edit: yeah, you're right, the support structure would have to attach to the baffle at least at the top and bottom. Worth it? Who knows?

[ThomasW]

How would you hold this array of drivers up against the baffle tight enough without using the baffle for mounting. Because using the baffle for mounting would defeat the purpose of isolation, I believe. Possibly an outer "real" baffle and an inner "mounting" baffle. The inner and outer baffles could be easily isolated. I think.....

Yes I too wondered about using a inner and outer baffle.

My drivers are scheduled for deliver today. I'll look at them and see if any 'ideas pop into my head...

[CraigJ]

I know most of us tend to over engineer our baffles, but if it's a "walk in the park" for Thomas's eight 8" drivers, will 12 drivers even be "working" enough to cause vibration issues? My 6 RS180's don't seem to vibrate 7 layers of .25" HDF + 1 gallon of glue. Perhaps they're is something I'm missing. ;x(

Craig

[chasw98]

Yes I too wondered about using a inner and outer baffle.

My drivers are scheduled for deliver today. I'll look at them and see if any 'ideas pop into my head...

Mine will be here tomorrow. Perhaps one of these vibration isolation mounts might have promise in isolating a front baffle and an inner rear baffle.

http://www.vibrationmounts.com/Store.asp?Page=Products1.htm

Picture this:
Front baffle is pretty on the outside. The inner side is lined with foam or felt material fitted into the cutouts that the line of drivers will sit against when mounted. For now assume 12 drivers 78 inches tall.
The rear baffle has a length of wood with 12 round circles cut in it spaced to fit the magnets plus 1/4 inch for off center possibility. Another board with no holes cut in it is fastened to the board with holes. This assembly will now have 12 circles of neoprene or some type of compressable isolation foam put into the 12 circles. It will then be fitted up against the 12 drivers and pulled tightly together in a sandwich using an appropriate 'stud and nut' type mount from the web page just linked. You would then have 3 points of isolation (1)the front of the speaker frame, (2)the rear of the magnet, and (3)the coupling between the front and rear baffle. That might mitigate any vibration between the driver and the baffle. Just thinking out loud........... And it would not be very expensive!

EDIT: And as Craig just pointed out, is it really needed? Jon?

[Evil Twin]

I know most of us tend to over engineer our baffles, but if it's a "walk in the park" for Thomas's eight 8" drivers, will 12 drivers even be "working" enough to cause vibration issues? My 6 RS180's don't seem to vibrate 7 layers of .25" HDF + 1 gallon of glue. Perhaps they're is something I'm missing. ;x(

Craig

Yes, but consider, my faithful apprentice, you ARE using 7 layers of 1/4" HDF, not a piece of 3/4" MDF or the like.

It would be reasonable for anyone with a large dipole panel to consider an accelerometer measurement on any proposed design. I think you would fine some type of spine design with the magnet assembly based spine support worthwhile, UNLESS massive measures are taken for the panel itself.

[CraigJ]

Ah, welcome back Evil,

I had originally planned on going with 6 layers, but added the 7th layer to please you. I knew you were in a far, far away place, but I'm sure you would have felt a change in the force had I only used 6 layers of HDF. I'm confident the gallon of wood glue used in laminating, assisted in the effort.

Your Young Padawan

p.s. is there an unknown build going on using multiple Peerless drivers that the Master hasn't told me about? As of now, still time to order the drivers.
p.p.s.s. dear Master, should I join the group and buy, or should I stick to our original master plan? :demon:

[Evil Twin]

You have not erred with your generous use of wood glue. And your intuition serves you well, regarding the consequences of only 6 layers of HDF, compared with 7.

However, my efforts are currently focused as hinted by the images earlier on this thread, though I have not forgotten the considerations we have discussed earlier this month. It is all part of a grand master plan to provide esthetic alternatives based on a well tested fundamental technology. Driver research is continuing without fail, treble units have been completed, and midrange evaluations should be complete by the end of this week. Some additional midbass unit tests will be done, but that is largely an unnecessary formality at this point.

The good doctor will continue working under my direction on aspects of the enclosure design and fabrication drawings to deliver to the Advanced projects division of Santhe/Sienar for fabrication. These may be distributed at a later date on the Holonet should there be interest by any besides the rebel scum frequenting these forums. This project is moving forward on an accelerated basis to gauge the feasibility of a live demonstration in Denver during the upcoming RMAF.

[CraigJ]

And your intuition serves you well, regarding the consequences of only 6 layers of HDF, compared with 7.

O.K., I confess, my HDF only has one smooth side and I forgot to reverse the last piece on my 6th piece so the front and back of the baffle would be smooth. My bad, thus the odd 7th piece. ;x(

So, if allowed to live, do I buy the four 10" we discussed, or await the outcome of the 7" driver selection.

still a young padawan

[Dennis H]

A simpler (but perhaps less effective) way to avoid metal-wood contact would be to use well nuts -- rubber thingies you stick in a hole and they expand when you tighten the screw.

http://www.mcmaster.com/ -- bottom of catalog page 3240 (type 3240 in the search box).

[Evil Twin]

O.K., I confess, my HDF only has one smooth side and I forgot to reverse the last piece on my 6th piece so the front and back of the baffle would be smooth. My bad, thus the odd 7th piece. ;x(

So, if allowed to live, do I buy the four 10" we discussed, or await the outcome of the 7" driver selection.

still a young padawan

This depends entirely on you and the space available for projects- the larger system design is in process at the Advanced Projects Division. The drivers are all on hand. Are you prepared to consider a construction of this magnitude? It is understandable, considering the size and weight, that it would be avoided, even considered dangerous.

The smaller system on the accelerated development path could be adapted to two different esthetic approaches. A preliminary analysis suggests that either approach can be most effectively constructed in a single cabinet, maximizing woofer volume while minimizing total cabinet volume and weight.

The larger system has several possibilities, and must, in our considered opinion, be two piece.

For the smaller system, several driver options are possible, including relatively low cost components. Initial evaluations show hint at considerable performance for the low price midrange; some others being evaluated are in a price range between 6 and 12 times higher. This is a span from $25 to $379, with the third least expensive at $162. After testing we will see if the higher priced alternatives actually deliver performance worth the premium. Considering the efforts in the cabinet and crossover, scrimping on drivers would not be in our best interest.

That said, at least two driver/crossover designs will be prepared; the selection process will identify the best low cost driver(s), and simply the best drivers out of the candidates being considered. The latter is not as straight forward as one might think- there is not always a clear cut winner in all categories.

[CraigJ]

Are you prepared to consider a construction of this magnitude? It is understandable, considering the size and weight, that it would be avoided, even considered dangerous.

As discussed previously, have partner with multiple plates in spine to assist in heavy lifting. Also, there is no such thing as "one more speaker". Obviously, I will follow one design into the next..... someone, anyone, please help me :storm:

still a young padawan

[Johnloudb]

All this talk of isolating the woofers from the front baffle worries me ... there in lies the Dark Side. So, I'm thinking of solutions to the vibration problems that are more in my DIY realm.

I'm thinking maybe a split baffle that interlocks. Think felt padding would dampen the vibration from the woofers but give some extra structural support the midrange/tweeter panel. It would also be braced down low on the baffle. The baffles will be 1.5" thick.

I think I'll probably use 1" aluminum tubing to support the woofer panel.

Image not available

Any complaints? Is this a valid approach?

I'm think the I'll place the drivers 12"-16" off the floor. I hear people talk about floor bounce but not sure how that would affect this type of arrangement.

[ThomasW]

My test baffle is 18mm BB ply with 1/2" MDF laminated to the front and back. It's well damped and quite rigid. The drivers will be bolted directly to the baffle.

Chuck and I have talked about bracing baffles with a metal truss system much like the ones used for antenna towers.



I have an accelerometer so I'll make some measurements of the baffle with the speakers powered up.

The RD series planars are VERY VERY stiff. They'll reinforce anything they're bolted to....so it might be a good idea to take advantage of this characteristic.

Whether it's beneficial to raise the drivers depends in how low they're playing.

[Hank]

Failure is not an option

Oh no! He's baaaack! I'm feeling the incredible pressure.
Okay, I'm thinking baffle is a sandwich of 3/4" MDF Front, constrained layer (PE's vinyl damping sheet), 3/4" birch ply Rear. I know, Thomas says it won't be as rigid as without the damping layer. I'm stubborn and have been wanting to try that constrained layer thing for years. Mount the drivers from the rear, round over the MDF front of the driver opening. PE gasket material between baffle rear and drivers, then pressure on the driver magnets to push them tight and leak-free into the gasket. Obviously the method of applying this pressure is the current topic of discussion.
One problem with my idea: I couldn't veneer the driver opening roundovers. That alone might kill my rear mounting idea.
Another question is: will two solid attachments of a "spine" to the baffle transmit significantly less vibes than conventional mounting of the drivers?

Mark (The Kid) started salivating when I told him I'd like to do active crossovers. I think he really digs active.

The RD series planars are VERY VERY stiff. They'll reinforce anything they're bolted to....so it might be a good idea to take advantage of this characteristic.

Thomas, thanks for pointing out the obvious. I think I'm back to front mounting and forgetting the spine/glued blocks/steel rings rear mount approach. Rigid baffle made more rigid with the RD's.

My last item is which RD: the 50's or 75's. As I've said, I don't care about sound perfection at stand-up walk around heights, so I can't yet see the necessity of the tall 75's. Mark and I will discuss predicted response differences at likely listening distance.

[chasw98]

All this talk of isolating the woofers from the front baffle worries me ... there in lies the Dark Side. So, I'm thinking of solutions to the vibration problems that are more in my DIY realm.


Any complaints? Is this a valid approach?

I'm think the I'll place the drivers 12"-16" off the floor. I hear people talk about floor bounce but not sure how that would affect this type of arrangement.

I am also almost ready to throw away the anti vibration ideas and go with brute non resonant force. Another cohort in this thread has said that is what he will do also.

How many drivers are you going to use? I don't think I will have the room to mount woofers that far off the floor.

[Johnloudb]

I am also almost ready to throw away the anti vibration ideas and go with brute non resonant force. Another cohort in this thread has said that is what he will do also.

How many drivers are you going to use? I don't think I will have the room to mount woofers that far off the floor.

Well, I have RD50 drivers and I'll be pairing those with 6 8" woofers per side. If you're using the RD75 with lots of woofers I don't think floor or ceiling reflections should be a concern since it's basically a true line source.

I kind of like the open space between the woofers and the RD50. So if I leave the space, the RD50 probably wouldn't help too much with stiffness. I plan on using a heavy gage square aluminum tubing to frame the woofer line array. And I'll be filling the vertical tubes with sand. This should be really stiff.

I'm probably throwing out the felt isolation idea too. Seems kind of flimsy and likely wouldn't accomplish much.

Anyway, that's my plan for now.

[Hank]

If I buy RD50's, and wanted the woofer line length to equal the RD50 length, I'd use 8 of my Peerless 830857's. They are 6.45" across the flats, so 8 of them would be 51.6" total array length. RD50 length is 51.5". 6 woofs would be 38.7" length. 51.5" - 38.7" = 12.8" /2 = 6.4" from each end of the RD50 to nearest woof.

RD75: 12 woofs would be 77.4" length and the RD75 length is 75 5/8" ( Jon Vader could fill a mall movie theater with sound from this configuration8O)
10 woofs would be 64.5" length.

[chasw98]

RD75: 12 woofs would be 77.4" length and the RD75 length is 75 5/8" ( Jon Vader could fill a mall movie theater with sound from this configuration8O)
10 woofs would be 64.5" length.

And the problem would be?????

I am planning on 1 RD75 and 12 woofers per side (plus tweeters in the future) on my remodeled back porch! None of the drivers will ever be working very hard to get very nice life like levels of sound, low distortion, and lots of headroom.
It has been suggested to look at the Neo8 PDR elements that are 8 inches in length and to use multiples of them (like 10 to equal 80 inches) in the same fashion as using multiple woofers. Hopefully, someone will buy some of them and be able to give an honest correlation to the RD75 unit. A lot of the larger B&G projects recently have been based around the Neo8 unit and not the RD75 but it has been hard to get decent information about the units.

I am going to try and mount some woofers this weekend and get some hands on experience. My woofers arrived yesterday.

[chasw98]

Here is the beginning of building the Peerless array. The masonite template was fairly easy to construct with a little geometry and a router table. I believe I have come up with a fairly easy, accurate, clean way to route the openings for the drivers. Pre marking the centers to route the center out is a must, then at the end chamfer the rear openings.

Gluing up.



Router bushing.



Template.



In action.



Finished cutouts.



Fitting drivers.



Well, all this looks great and wonderful and it sure does appear if that Chuck knows what he is doing..... DOH! I cut it twice and it is still too short. This is only 81 inches long and I meant for it to be 84 inches. Oh well, good practice, $25 mistake, back to home depot.

[ThomasW]

I'm lazy so instead of moving, adjusting and clamping a template 24 times, I'm wondering about simply cutting overlapping circles.

Seems to me that would do the same thing with the exception of the 1st and last drivers in the line....

[chasw98]

I'm lazy so instead of moving, adjusting and clamping a template 24 times, I'm wondering about simply cutting overlapping circles.

Seems to me that would do the same thing with the exception of the 1st and last drivers in the line....

Where is the challenge? Expand your skills!

PS, I will be done with my template shortly if you want to borrow it. :E :B

[JonMarsh]

Just use the template at the ends....

Nice work, Chuck.

For all who got in on this buy, I bet this is going to work out pretty nice- these drivers have a pretty decent motor in them.

[chasw98]

Just use the template at the ends....

I know but I just can't resist pimping the curmudgeon! :T

Nice work, Chuck.

Thank you.

For all who got in on this buy, I bet this is going to work out pretty nice- these drivers have a pretty decent motor in them.

I hope so. I have not told the other half that a 7 foot array will be appearing anytime soon. :E ;x(

[Hank]

Just use the template at the ends

There you go.

Someone asked about the BG Neo8PDR's Is the Dayton Audio PT2C-8 made by BG and if so, does it have the Neo's guts? It's on sale at PE for $36.57 retail. I'm sticking with RD's - just posting this in case anyone is interested.

I have not told the other half that a 7 foot array will be appearing anytime soon.

Chuck, you may be walking into the proverbial train tunnel with a headlight approaching. That's the one drawback of the RD75's - a WAF's decor-imposing giant structure. Time for a new piece of jewelry? Hmmm?

[ThomasW]

Is the Dayton Audio PT2C-8 made by BG and if so, does it have the Neo's guts?

Nope not made by B&G. And IIRC is a push design not push-pull like the Neo8's.

Also the PT2 are 'tweeters', IMO they don't play low enough to match up with the Peerless (yes I know people that are doing things like this but it's not something I'd recommend)

[JonMarsh]

I hope so. I have not told the other half that a 7 foot array will be appearing anytime soon. :E ;x(

You haven't? 8O Ruh roh!

[chasw98]

Chuck, you may be walking into the proverbial train tunnel with a headlight approaching. That's the one drawback of the RD75's - a WAF's decor-imposing giant structure. Time for a new piece of jewelry? Hmmm?

I realize that, except.... I have the best gal in the world and she knows I like speakers, so as long as they look nice, it is OK with her that I have them. I am also remodeling the porch with hurricane impact windows and furniture for her plus a trip to Aspen to see the fall colors. I have built up my karma in the bank, I think.

Has anybody thought about how they will wire up 12 or so drivers? I have got my own scenarios I am looking at (obviously some series parallel affair) but I am curious what others have thought of or come up with. I have even come up with 12 1 rack space 100wch amps for grins. Talk about redundancy and headroom!

[exojam]

Chuck,

My wife may be in the running with yours for the “best” (but I know we both have VERY tolerant wife’s). It depends on how she responds to the little sub woofer plan I am hatching And on that note I may try to call you this weekend to pass some ideas by you.

James

[CraigJ]

" I have built up my karma in the bank, I think" :rofl: . I can relate to that.
Craig

[chasw98]

And at the end of the day..... PROGRESS!







5 down, 7 to go for one side.

[JonMarsh]

Purty them up... ?

I don't know if you gentleman have thought all that much about how you're going to cosmetically finish these works of sonic art, but you could do worse than to take a gander at Mark K's RS225 dipole for some starting ideas....














Now, if only I could find a good 8" driver buyout deal.... :B

[ThomasW]

Has anybody thought about how they will wire up 12 or so drivers?

You have 4 sets like this...



Or......






From Jim G's whitepaper....

[chasw98]

It sags... Time to implement the stiffening plan.

[ThomasW]

Paint it with Viagra...... :B

[JonMarsh]

Paint it with Viagra...... :B

That would be kind of expensive compared with some conventional braces...
:W

[Johnloudb]

Looking good Chuck! :T

I decided to do some box modeling for my six woofers using 8" Ushers.

So I did a closed box sim with an internal volume of 10,000 liters, and a uniform feed 2/2/2 as per Thomas's post. Here's what I got.

Image not available

Here's the setup conditions in LSP Cad lite box sim. I'm not sure what Box Q (line 2 in box specs) refers to, so I left it alone. Does this sim seem realistic? Not sure I trust these results. I'm just looking for an idea of what kind of EQ I'll need to get down to 16Hz! :P (kidding) Probably 35 - 40Hz. I'll be building an electronic crossover.

CLOSED BOX
Box
Vol 10000.00 l
Q 15.0
Fill 50 %

Driver
Manufacturer Usher
Model 8137A
Filename 8137A.UNT
# drivers 6
Extra mass 0.0 g
Electrical connection of drivers : 2-2-2

Setup
Start freq. 20 Hz
Stop freq. 1000 Hz
# plot points 50
Ug 2.83 V
Rg 0.00 Ohm
Lg 0.00 mH
Pg 1.000 W

Additional details:
-3dB point: 68.37 Hz