I don't know but the drivers must have gone into some kind of resonance.  I'm guessing the sound I heard was the coil touching.  

How's the weather over there?  We've had a lot of rain this side of the divide lately but beautiful today!

Fortunately, I haven't found another piece of music with that kind of sustained bass.

More than any speaker I've heard, these reveal the quality of the recording and performance.  It's like looking over the sound with a magnifying glass.

In my room, the frequency balance of these speakers is so good that classic rock sounds like it should without any EQ. And I usually run the speakers without a ZROCK2, although it makes sound considerably better most of the time. Much of my listening is from the perspective of "what will a customer hear when he or she buys this or that in it's normal configuration..."  A ZROCK2 is so over the top, that it feels like serious cheating in so much as that once you have one, you can't not have one.

During the fest if I demo these (or any speakers) with a ZROCK2, since it has a bypass switch it is easy to hear it with and without... Problem is that from the very first time someone flips the switch to "on" no-one will like the sound without it. It will remain ON during the entire fest. Then when people, some who may not realize it was ON get home, order the a system without a ZROCK2 they will wonder why it isn't sounding the same.

For me a ZROCK2 is a dangerous drug. When it's on it makes everything sound 30% better than it actually is (recordings, not speakers and amplifiers) That in turn makes you think your gear is 30% better than it actually is to the rest of the world that has no ZROCK2. If ever you design a amplifier that needs a ZROCK2 to sound great, you've lost your spark.  This is why when I listen to a ZROCK2, it's only for a week at most and only periodically.

This will likely change soon enough as this new open baffle design with the Crystal 10 driver from Lii Audio will require the ZROCK2 to work in an open baffle speaker design on it's own. In fact I expect this will be a new and probably huge market for the ZROCK2. It's curves should fit perfectly with almost all passive open baffle speaker designs. I suspect these drivers with some break-in combined with this ZROCKED BAFFLE will be good enough to get that box of drool towels in the attic down for auditions.

Today I got both of the baffles finish sanded and have oiled the back sides of each. Still waiting for the drivers to arrive. Will design a base for these probably similar to the Big Betsy hopefully this weekend so I can post some more pictures!  I am also designing a high mass clamping system into the baffle to secure the drivers in place. When they cost a grand for just the drivers it's worth going all out to see what the true potential really is.  A few wood screws would work, but I can think of better ways to couple the energy from the frame of the driver into the heavy dense baffle.

Steve

I am thinking about using 3/4" + 1" plywood for the baffles.  

I am also curious if the F15 would work in a half imperial.

UPDATE 8/3/2019

I fixed the booboo and  as I mentioned got both baffle finish sanded and oiled on one side. Here is a picture



This is the back side.  I plan to mount the driver from the back with the cutout on the front side coming right to the edge of the surround.  The back side here in the picture is stepped to accept the driver and a high mass clamping system to hold the driver in place.  

When the oil dries, I'll be able to flip it over and do to the front side.

Steve

I was looking at some that were already built that are for sale. Thanks

Quote:


So true!  I don't know about the cheating aspect but my guess is that maybe 5% of recordings sound as good on the bypass.

Steve, can you clarify the weights location?  Are you suggesting they go stacked on the back or side-by-side but in either case with an asymmetric mounting?  The symmetry makes a lot of sense.  I was even wondering about a pair of baffles with the driver mounted 2/3 up and 2/3 out.

I do have a pair of big cast iron handles on the way already.

Now Steve has me looking for hunks of brass.  But what shape would be best?  It's expensive.  Bar stock is available.  Maybe 1/2"x1 1/2"x6" or would 1/2"x3"x3" be better?  Or even a thinner stock with a larger footprint?  At 1/2" thick, you need 6.25 sq in to make 1 lb.  Or some 2 1/4" round stock that weighs about 1 1/4 lb/inch.  I've also found thicker stock that I could get 3"x3" pieces out of at either 1 1/4" or 5/8" thick.  So many options!

I've been listening to my MDF Big Betsy's now for a couple weeks.  The bass has gotten better, but is not bone crushing.  Actually, it's just what I'd expect from a 15" driver with an Fs of 50 hz in an open baffle enclosure.  It's going to be interesting to hear Decware's this October (just made my reservations 2 days ago).  Actually, when I think about it...if I have 1w running through these things I'm probably up in the neighborhood of 100db.  At that level, I would want at least 103 db and probably more like 106db of bass.  There's no way to get that, that I know of, other that turn up the power and somehow cut back on the audio that's not bass.  Maybe that's a Zrock2.  Like I said, I'm looking forward to Oct.

The amazing thing about the Big Betsy's, IMHO, is the HUGE sound stage.  They just fill the room like no other speaker I've ever had.  And that includes a couple of attempts with multiple front and side speakers in an attempt to get a bigger sound stage.

One thing I also noticed yesterday is this:  I have one song that has a couple of notes it it that can make you wince if everything is not perfect.  For a LONG time I thought it was the recording, but I've come to realize that a great speaker does not have an issue.  Probably has a lot to do with the amp too.  My recording of Norah Jones "Come Sail Away" has a couple places in the first 30 seconds that will tell me if I'm dealing with a great speaker or not.  The Big Betsy's sound as good as I've ever heard on that song.

Now for some pictures...First is a back view.  The handle/stiffener is a 2x4 and the base is built to take cement "patio blocks" to build up the weight.



I's using 2 patio blocks per speaker, that are screwed down with a cover piece of MDF.  This brings each speaker up to around 100 lbs.



The front view makes the top look wider than the bottom, but let me assure you it's not.  After seeing that pic, I went out and measured.

Guys, a less expensive option is Rockwell dampening material. It is dense rubber with a foil topping, and is adhesive on back for easy application.  It helped placed on the back of the baffle, as well as dampening the speaker basket.
Also, if your base allows, stiffeners help too. All of this made a big difference With mine. I still have to order a few more pieces for my bass baffles.

Quote:


SteveB, Welcome to the forum!  You're in the right place.  Once these become available and for sale, this is where it will be announced first.  We may be able to take orders starting in October.

Thanks for asking!

Steve

Quote:


When I saw it in the vision it was round, about 3 inches tall, about 2.5 ~ 3 inches in diameter, and had radiuses on both ends.  A hole in the middle with a bolt to adjust tension and there may have been a thin gasket of some sort.

Steve

Dan,
It looks like your driver is centered in the arc of the sides. Is that a true perception?

Brian

Re: Steve's BIG BETSY Project
Reply #324 - Today at 07:58:37  
Dan,
It looks like your driver is centered in the arc of the sides. Is that a true perception?

Brian

That's another photo angle issue.  Baffle is 42" high with center of speaker 25" off floor.  24" wide at top and bottom.

2x4 in back is both stiffener and handle.  Concrete patio blocks are around 17 lbs each (34 lbs total), MDF baffle is around 60lbs, speaker is a few lbs.  Total is close to 100 lbs.


Dan

This is an interesting description about vibration damping.
https://www.youtube.com/watch?v=VCxm3vTWgvU

I played around a bit with bypassing my ZR2.  I still don't like the idea that it's a "cheat" though.  I mean, if the ZR2 is a cheat then is acoustic room treatment also a cheat?  Afterall, Steve's listing room so so superior to anything most of us will ever have it makes the playing field unlevel already.

Anyway, A/B-ing the ZR2 is hard since it also offers overall gain in addition to the equalization but what I found is that without the ZR2, I still have the same bass extension but the bass seems thin and muted and my Big Betsy's also seem to have more of a bloom with extra volume (with the ZR2 my BBs are blooming at all volumes).  With the ZR2 it almost seems like I have an extra octave of bass but I think it's more just the extra fullness of the existing bass that I'm hearing.

If this were a competition to get there the hard way then the ZR2 would be cheating.  But it's not a competition and when an audio "shortcut" presents itself, use it!    In other words, if you don't have a ZR2, place an order.  This is as close to a sure thing as you'll ever get in this hobby.

This post relates to the ZR2 and the Big Betsy but I have the same bass experience with my HR1s and the ZR2.

The ZSB ought to be able to be modified for speakers, wouldn't you think?

To improve structural rigidity and redistribute center of gravity while making the structure lighter may I suggest the following for consideration:

-      Include I-beam braces running from the 2 X4 handles (on each side) to the a similar 2 X4 on the heavy mass horizontal footing. The web of the I beam can be much larger than the flanges (or the flanges eliminated altogether leaving only the web for a cleaner appearance at the back) since torsional forces if any are minimal if any when the speaker drivers operate.

Advantages:
o      This will reduce/eliminate structural resonance (not Fs the speaker drivers free-air resonant frequency) due to the added rigidity. Other wise it behaves much like a cantilevered structure with a heavy mass above the horizontal centerline which is prone to “singing” unless a very thick front face is employed making this large and tall speaker quite heavy. The triangular structure is heavily used in structural engineering to reduce weight thus cost, while increasing rigidity. Best of both worlds.
o      It will also enable the front baffle thickness to be reduced thus moving the center of gravity of the speaker structure as a whole further horizontally behind though still high up due to the dominance of the mass of magnet compared with the now a lighter front face. The front foot extensions at the bottom can thus be eliminated given a cleaner front look as the c.g. has moved back behind the fulcrum point (caution: tipping depends on how much the front baffle thickness is reduced as the c.g. is still high up and whether the speaker flange is mounted at the back versus from the front in). Tipping can also be avoided by simply attaching a couple of nylon straps at the back of the horizontal footing to the floor.

Adam, I got 2 sq ft on amazon, but don’t see it there anymore.

But I did find it here:    https://www.newegg.com/p/0UK-00ZW-00047?item=9SIAGNP8994622&source=googleshoppin...

Archie,

When testing speaker baffle resonance or the sides of a speaker box, the frequencies are narrow. As an example, 400Hz might have no real drama, nor does 500Hz, but 417Hz might really light things up. The only effective way to test for this is to be able to slowly sweep the frequencies or step the frequencies 1Hz at a time.  Also you don't need a stethoscope always, you can use. your finger tips.  What you do need is stick-on dots that you can stick on the exact place where your finger tip was and write the frequency on the dot.  If you want to get documentative, you can glue a piezo tweeter diaphragm to the spots and hook the leads to an oscilloscope.
 
Many speaker cabinets I have tested over the years and some drivers themselves, have what I call an evil note, where if you hit it, and it sustains for any length of time, like a whole second, it will resonate and peak the frequency by 6, 10 even 12dB!!!! Just a single note in some cases. This is why some speakers sound so great until you play a specific recording with a sound that falls into that notch... Then suddenly your eyes squint, your neck cocks to the left and turns slightly...  then your palm finds your forehead.

And, as far as the weights, keep in mind it was a vision that flashed, but I agree with you it would take for example a 417hz peak on a board and move it down out of the audible range. Being of high density and mass it isn't going to turn energy into heat, but rather store/release/redistribute the energy.

I figured out right away with these Big Betsy baffles that they themselves actually become the wavefront, so if we look at the baffle similarly to the way we look at a speaker cone, we're just dealing with modal resonance patterns that are aggravated at certain SPLs. This is why it will be fun to see how baffles compare that are stiff sound boards, vs. energy traps.  

You can find frequency generators in apps for your computer or phone.  You can't rely on recorded tones, because you have to sweep the tones back and forth many times as you hunt down the vibrations, and then you narrow it and narrow it until you find the center frequency.  Usually in the case of a speaker box you put a brace in that spot -- which often doubles the frequency and drops the energy in half.  However, weighting it would make it more relaxed sounding and perhaps natural... so much audio gear has it's panties in a bunch from over execution... sometimes its nice to just ditch the panties.

Steve

So this is the first coat of linseed oil and after at least 24 hrs I'll do a second coat using steel wool, buff it after it dries and wax it.  Something about walnut that I have not found a finish that I like (poly/shellac/lacquer) because it makes it look fake, brings out a purple plastic veil that I can't stand, and that's amazing to me because I have never found anything that shellac didn't make look over the top good, except walnut.

The most impressive part of this build so far is actually the figured oak.  I purchased 20BF of this stuff for making tape machine sides, which I did, but now seeing it in the speaker, with just natural oil framed by the darker walnut I really couldn't be more pleased.  

BTW, the knots you see on this panel I actually painted into the finish because this baffle was knot free and the other panel is full of knots.  Hehe, that's the beauty of oil finish on hardwood... I can add more knots anytime I want... well within my patients to hand paint intricate wood grains because you can't just paint a knot anywhere you want.

So the next step will be to actually install the bases and front feet so I can stand them up in the shop.  Then I will focus on the esoteric mounting system for the drivers.  By then they should be here and I can lay the driver in the baffle and slowly craft something really trick to hold them in place with adjustable tension.  This way I can experiment with hard-coupling, gaskets, or even energy drains like a viscoelastic membrane.

While I wouldn't hate a larger radius on the opening I think this partial horn-loading of the cone will add some real attack.  We will see.

Steve

Steve, I think that frequency investigation is beyond me at this point.  My facility to pull that off is primitive, to say the least.  I am thinking about trying something I saw in a video.  A couple of the links have already been posted in this thread.  The engineer working with panel speakers determined that mounting the driver 2/5 and 3/5 off center and then mounting weights in the four quadrants in a 2/5 and 3/5 location helped break up resonances and reduce what remained.  He also said the total mass of the weights should be about 20% to 25% of the baffle mass.  I'm estimating my baffle at 50lbs so I'd need 10+ lbs of weight.  That would be roughly 3"Dx1"L weights, 4 per baffle.  Here is one video.  The relevant time start is around 21:30.  https://www.youtube.com/watch?v=zdkyGDqU7xA

The thing is, in his next video he claims that the reduction in the peaks was small and that blending panels with different peaks was a more effective method for flattening the frequency response.  (22:23 for:  https://www.youtube.com/watch?v=CKIye4RZ-5k)  But since I'm not building more Big Betsys and forming an array, the weights may be the only real option available.

All that said, I haven't found any bad tones in my listening sessions.

Pal, I don't know how it relates to perceived bass but I hear the strongest bass in the baffle at the top when using a stethoscope.

At some point Arch, I will run REW to see how the response looks like vs my other OBs.  

I'll see what kind of peaks I have across the spectrum and then zero in on those to see if the wood is contributing.  

I won't alter these baffles any more.  They are just a temporary home until I build some proper ones.  

I have some Baltic birch leftover from my previous build.  I may double that up to see how it sounds and then decide if I go hardwood or not.

I have found its possible if you change the smoothing and/or the increments shown on the chart axis