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Best "bang for the buck 15" driver?

#21
greenboy said:
Amazing how few MI speaker designers have thought about any of this.
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There's a world of difference between what MI speaker designers, at least those with real acoustical engineering chops, think of and what makes its way into products. Always keep in mind that marketing departments decide what gets made and what doesn't, and they are more conservative than a convention of Rush Limbaugh devotees. What gets made is what they think will sell, and they think what will sell is what looks right, and what looks right is what's familiar.
 
#22
billfitzmaurice said:
There's a world of difference between what MI speaker designers, at least those with real acoustical engineering chops, think of and what makes its way into products. Always keep in mind that marketing departments decide what gets made and what doesn't, and they are more conservative than a convention of Rush Limbaugh devotees. What gets made is what they think will sell, and they think what will sell is what looks right, and what looks right is what's familiar.
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That's why I'm a big fan of old style fabric speaker grills; Can't see what's behind them. ;)
 
#24
lorenk said:
So, if I wanted to get good mid range dispersion (am I using the wrong term here?) with a Mesa RR 2x15, could I still mount two 15" speakers in the enclosures and a mid range without modifying it? Or will I need to modify the cabinet?
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You'll have to modify it to the extent of mounting the mid driver, preferably two, if they'll fit, plus a crossover. I'd bag the HF horn, unless you're a slapper.
 
#25
The 3015 will be beamy from 1 to 3.5K but it has a rising response in this area that provides a relatively flat power response through the room. Considering the hole removed the piezo's have almost no additional weight and that is a major consideration in the design intent. I am using the duck horn Dayton piezo that has a "flat" response down to 4K and a drooping response above 8K this is fine with me. They are not that harsh when four are used as in the last cab I did. And lets be real all this harsh, beamy, peaky stuff is realized by the guy with the bass standing directly in front of the cab. It sounds different out in the audience. And there is that thing on the amp called EQ. I have gone in a different direction from the cab at the start of this thread. Josh wanted another Peavy bottom like the one he has but the Scorpion needs a mid to extend its range a piezo will not do and putting two 15's in one cab is counter to the lightweight direction I want to go. Josh does not want clarity either but I am forcing him down this path. THE CUSTOMER IS NOT ALWAYS RIGHT! New drawing coming soon..........
 
#26
Bellair Audio said:
The 3015 will be beamy from 1 to 3.5K but it has a rising response in this area that provides a relatively flat power response through the room. Considering the hole removed the piezo's have almost no additional weight and that is a major consideration in the design intent. I am using the duck horn Dayton piezo that has a "flat" response down to 4K and a drooping response above 8K this is fine with me. They are not that harsh when four are used as in the last cab I did. And lets be real all this harsh, beamy, peaky stuff is realized by the guy with the bass standing directly in front of the cab. It sounds different out in the audience. And there is that thing on the amp called EQ. I have gone in a different direction from the cab at the start of this thread. Josh wanted another Peavy bottom like the one he has but the Scorpion needs a mid to extend its range a piezo will not do and putting two 15's in one cab is counter to the lightweight direction I want to go. Josh does not want clarity either but I am forcing him down this path. THE CUSTOMER IS NOT ALWAYS RIGHT! New drawing coming soon..........
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The beamy characteristic is also realized by people in the audience that are not in the loudspeaker's line-of-fire so to speak. That's pretty much most of them. IMO they won't hear the mids. Regardless, has one of [Invalid or Expired Link Removed] been tried? The rising peak of the 3015 might help the loss of "presence" that one of these pattern modifiers introduces above 1 kHz. A 3015 with one of these and the right piezo bank might be an option for someone that doesn't want to go with a full-on low/midrange/crossover design yet still wants reasonable dispersion of the important 1k-3.5k area. It's pretty inexpensive to try too (at least if you already own the 3015 that is :p ).
 
#27
This beaming is very important for a guitar because its in the hard 2nd harmonic range only reached by 6 to 10 string bass. I tried this decades ago for 8" two way home speakers and did not get acceptable results but this could work for guitar, not as important for bass. But I will try after they are built to do this. Thanks for the reminder.
 
#28
Codger said:
Regardless, has one of [Invalid or Expired Link Removed] been tried?
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That's similar in concept to Ted Weber's 'Beam Blocker' (irrespective of what that article says) and yes, such devices do work. Variations on this theme date back at least fifty years, and operate using simple principles of diffraction. The problem is how they work, which is by reducing axial sensitivity. Using a driver with adequate dispersion works a whole lot better.
 
#29
OK before I get a bunch of crap the tweeters do not have to be together to work right. You can accept a small interaction and notches by sticking them together or you can have no interaction by having them farther apart than the lowest wavelength they propagate. This would not be done for stereo but a mono bass guitar bottom is OK. I am considering using four tweeters with two on each side. Nothing fancy just a lightweight properly tuned bass cab.:hyper:
 

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#30
Bellair Audio said:
OK before I get a bunch of crap the tweeters do not have to be together to work right. You can accept a small interaction and notches by sticking them together or you can have no interaction by having them farther apart than the lowest wavelength they propagate.
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Or you can mount them vertically, eliminating any dispersion and combing issues while improving vertical pattern control. ;)
 
#31
You do not eliminate combing by putting then vertical to each other. That only works on one horizontal plane in the middle of the tweeters. Any deviation from that plane vertically will have combing. Of course the closer they are the less this is. The way I have them there is no combing at all and the sound is spread out a little. Remember this is a bass cab not a stereo system.
 
#32
Okay, molds are prepped, cloth(carbon and kevlar) is all cut(the carbon was easy, with electric shears, but the kevlar was much harder to work with), Nomex honeycomb cut and ready. We lay it up and bag it tomorrow morning, along with another cool experiment with the honeycomb. I'll post up some pix of the resinous fun, and if I can remember to do it, I'll get shots of a cool experimental guitar under way at the shop.

Josh
 
#33
Okay here we go! Actually it went pretty well..... First, the mold:
mold1.gif

This step is call "Pre-pregging" where the cloth is soaked with resin by squeegee and roller. Last layers into the mold are the first to get the resin:
Cclothpre_preg2.gif

Next comes the laying into the mold:
Cclothlaying3.gif

This next step is a cool idea by Mr. Devins(the shop owner). He adds a "bead" of tool putty(a light, fluffy mix used for mold-making) along the corner surface inside the cloth. It serves to solidly form the corner edge of the cloth and also solidly set the honeycomb in place. Nice touch!
Cclothtoolputty2.gif

Next comes the honeycomb, in this case we used Nomex:
honeycombinsertclose1.gif

Then comes the inner Kevlar layer. Kevlar has an interesting "damping" effect we are investigating as an alternative to adding a non-structural damping layer over a simple fiberglass inner layer. (Less steps and more stiffness).
Kclothlaying2.gif

Next comes the vacuum bagging for overnight curing with a solid clamping. A layer of very thin "release cloth" is placed over the panels, followed by a layer of fluffy batting for vacuum equalization, then into the bag where it's sealed up and hooked to the vacuum pump.
bagvacuuming1.gif

The whole process should have taken about four hours, start to finish. We spent about six with our "learning curve" included. The panels will come out of the molds tomorrow for trim and "bonding prep" prior to assembly. At that time the various speaker and hardware bolting points will be reinforced against collapse from fastener clamping.
Here's another take on making light panels for less money: Eighth-inch plywood with a honeycomb center! At two ounces per square foot it might be a winner. We're going to do a cabinet this way and see how it sounds. Here's our inch-thick test square:
eighthinchply_honeycomb2.gif

Here it is next to an inch-thick piece of twenty-ounce per square foot plywood.
boardcompare2.gif

Quite a difference! The sound performance remains to be seen. Hopefully both ideas will perform well. Stay tuned!
These next two pix are of a cool guitar body Mr. Devins has been working on. It might Make for an interesting. "bigger" sounding acoustic bass?
protobody1.gif

protobody2.gif

This last picture is one of the usual denizens of Mr. Devins' shop:
racecar1.gif
 
#34
Bellair Audio said:
You do not eliminate combing by putting then vertical to each other.
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Agreed, but you confine the combing to a different plane. Everyone at the same height hears the same results. A seated audience of course hears differently from standees, and short vs. tall people may hear differently.

As people move around the hall they don't hear any combing (unless they bounce a lot while walking). And two people seated side-by side---of similar height---hear the same.
 
#36
Bellair Audio said:
But the response problem is still there even if it is not shifting by moving up & down. The point is to eliminate the issue with the placement I am using.
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That placement does not eliminate the issue. If anything it makes it worse. Vertical placement does eliminate the issue, with the added benefit of vertical pattern control.
 
#39
Still tuned. Regarding your 1/8 ply and honeycomb panels, how are you planning to join them? My own experiments with 1/8 ply and foam core panels have shown that, while the panels are relatively easy to construct, joining them in a manner that provides both durability and structural strength is not. I'm very interested to hear your take on this.
 
#40
There is a layer of fiberglass between the panel and the honeycomb. I am also thinking about using a soundproofing fiber board for the meat of the sandwich. Unfortunately all these ideas require a working model to test out. My latest issue is second guessing the piezo tweeter. I have six various tweeters and I think I am going with a real magnet / coil speaker despite the weight. Sorry Josh!:crying:
 

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