Jub-Like Drone Build (Jubilee)

[Panacea Engineering]

I asked the below question in Dave's Driver Balancing thread and I would appreciate anyone's input here, as I think this is an important question, that has not been discussed yet.

"Dave,

I have been reading this thread with great interest. As I am getting ready to start some extensive testing on the Jub-Like Drones, it raises the following question for me:

Should I use the two way passive with a dummy load for the HF or should I use one of my DBX DriveRack 260's, where I can manipulate the upper cutoff range?

This would enter into the mix, a whole new set of parameters, to establish the upper end of the cabinet. Is this something we would want to do? I certainly do not want to sabatoge your thread, so I will ask the same in the build thread. I look forward to responses in the build thread, if everyone doesn't mind."

W. C.

[Guest David H]

W.C. I would think either would be suitable, however I would like to see the curve without any HF cut, to see if the the HF was influenced by the woofers, build, drone etc.

I would think first order of business would be to measure the box response. Using an filter in line, is more for balancing the drivers rather than checking the response.

Dave

[Panacea Engineering]

Dave,

This is gonna sound Dumb any way I ask it. Am I to understand that the drivers shouuld be connected straight to the amp with NO type of crossover in line? Then do a full frequency sweep? Second question; Do we want the drivers in series or parallel?

I am hopefully gonna get to start with this today, as long as the rain isn't too bad. Supposed to get near seventy, mid day.....

W. C.

[Guest " "]

for a 2-way setup

I would under size the fuse on the tweeter during testing and tweaking. as cut off frequency goes down, so does power handling.

[PrestonTom]

My friendly suggestion is that you do first things first. At this point I would not worry about setting up the crossover and the tweeter. That comes later.

You have two systems that need to be set up. Both use drones. Each of these needs to be tuned with the weights. One of these uses K-31 woofers and the other does not. We know the non-drone version with the K-31 woofers has a throat area that is within about 10% of value prescribed by the Keele equation. The other driver has different T/S values and the area will need to be correspondingly altered, although it may not be much. We know that the K-31 woofers require a back volume of about 37-39 liters per driver. The other driver is different, however the back volume can be "adjusted" with open cell foam (you can get this at Joann's Fabrics).

How the back volume requirement might change (reactance annulling) with a drone vent is unknown, at least to me. There is also a concern that the back volume itself might be "leaky" (mistakes sometimes happen ....). In a non-vented cabinet, this can be checked with an impedance plot, I am not sure of the strategy/interpretation with a vented system.

So it looks like there are several things that need to be tackled before you worry about the tweeter integration.

Good luck and how are you coming along with your measurement rig? I remember I had a number of trivial set backs in getting my computer to recognize the sound card etc - but those are solvable probelms (headaches)

-Tom

[Panacea Engineering]

Tom,

Well as usual, it is raining like a Mo Fo.....

What I just interpreted from your post IS; Not to use any type of crossover...is that correct...? Also do we connect the K-31's series or parallel? I will be using a SAE A102 amp 100 wpc.

There are three cabinets to test:

Golden Jubilees (Reference

Cabinet A - two K-31's and a K-12 passive (NO Weight Adjustment(

Cabinet B - Two K-31's and a TC Sounds VMP 12 (Adjustable Mass Passive)

These three should keep me busy for a while....... As far as "The Rig", I should have everything we need to test with, hopefully. I have the Dayton WT3 Woofer Tester for the Inpedence curves. I think I listed everything a few post ago. We will not get into different woofers for quite a while as I want to "Milk" all I can from the K-31's. We don't have a Joan's Fabrics here in Charlotte...I believe it is called Mary Jo's Fabrics and every time I have been (Grill Cloth) I have been the ONLY man in the store...really not a bad place to meet women...Well...that is a whole different story...[A]

[PrestonTom]

Hello WC,

You have got the rain, while Connecticut is getting the snow.

Yes, the drivers are wired in parallel. Note that at a low frequency the system repsonse will drop to as low as 3 Ohms.

There is probably no reason to test the Reference system at this point. Simply enjoy them ....

No crossover is necessary at this point. Just be careful about putting too much voltage in below about 40 Hz or so. When you do incorporate the tweeter you may want to put a cap in series with the tweeter as a safety pre-caution while the crossover is tuned up. At a future point in time, you will see a couple of peaks in the bass bin response. These are around 100, 200, and 300Hz. These are due to reflections resulting from the horn having a smallish mouth. They are exaggerated when the cabinet is pulled away from the corner (IOW, the boundary gain tends to hide the peaks and dips). Ultimately, you may want to knock down these peaks with a modest amount of EQ'ing (this is trivial with a electronic crossover like the Electro voice dx 38 etc)

Is there no adjustment on the K-12 drone? I am a bit surprised. Perhaps there is someway to jury rig something.

Yes, I have had the same experience at the fabric store.

[Panacea Engineering]

Tom,

The only way to add weight to the K-12 would be to drill the spider disc and use a toggle bolt and washers. Of course these can be weighed but the real problem is; The rubber surround appears to be extremely flimsley. I am afraid if any real amount of weight was added it would start to sag. I would rather leave the K-12 as is and do any mass adjustments either with the TC Sounds VMP 12 (Built like a tank) or the CSS AMP 12 (not as heavy duty as the VMP) We have two different adjustable mass passives to try and I am sure that each has its own sound charestics.

W. C.

[Guest David H]

Dave,

This is gonna sound Dumb any way I ask it. Am I to understand that the drivers shouuld be connected straight to the amp with NO type of crossover in line? Then do a full frequency sweep? Second question; Do we want the drivers in series or parallel?

I am hopefully gonna get to start with this today, as long as the rain isn't too bad. Supposed to get near seventy, mid day.....

W. C.

Yes, connect the woofers in parallel, do a full sweep on the bass section of your 3 test subjects and post the results.

Really no need to check the HF at this point, after the bass bins are done, you can install the filters and balance the 2 sections.

Dave

[Guest David H]

Tom , and Fritz, thanks for all the good info, this is the sort of info I can use for my testing and balancing.

Dave

[Panacea Engineering]

OK, FINALLY some decent weather.....! Anyway, got some things taken care of this morning and started at lunch setting everything up. The first test i wanted to do was the Impedence test with the WT# Woofer tester. Started out having to set the laptop up, it recognized the hardware correctly, went through all of the steps of calibration and ran into a snag. No matter how many times I tried, I could not get the leads in a dead short situation tio read below 1 Ohm. I tried this, closing the program, re-booting, resetting to default and anything else I could think of. So after spending an hour trying this, I decided to start from scratch because, my Fluke was giving me correct readings for the 1K Ohm test resistor and the best I could get out of WT# was 794.56 Ohms. Something was not right at all. Disconnected everything, reloaded the software and went through the steps again. I discovered that the mocrophone was set at 100% rather than 1 and that was the issue all along. I distinctly remember going through that step but for some reason it did not take the first time. After resetting, everything checked out perfectly, the test resistor read in at 1001 Ohms on a 1% test resistor, so I was satisfied. I did three test today and I have NO idea what I have just accomplished at all as I am sure that what I did is/was wrong, but here goes. The WT3 wants you to test Free Air Impedence and that is what I did for all of the test. It also gave me options of putting in SPL (which I do not have for the K-31 and/or the box volume. These test will be done tomorrow after a little research, but I did manage to get the Free Air Test done for the K-31 by itself and then for the Golden (two K-31's in parallel) and then Speaker A (2-K-31's and the K-12 passive. The screen shots will follow in the next three post.....

[Panacea Engineering]

K-31, sitting on the table with leads hooked up

[Panacea Engineering]

Screen Shot of WT3 free Air Test of k-31

[Panacea Engineering]

Golden (Reference) Both drivers connected in parallel Impedence Sweep

[Panacea Engineering]

Speaker A K-31's in parallel with K-12 passive

[Panacea Engineering]

Someone a whole lot smarter than me will need to interpret the last one. I am presuming that the three humps are reflections and if that is the case I know the reason completely. The speaker was sitting behind a large sliding door and I did not think it would make any difference since I was reading directly from the speaker rather than a microphone....Maybe this is part of the learning curve and I need to have it completely outside. That will happen in the morning. Well, at least we have finally started and I look forward to any and ALL comments.

[mikebse2a3]

Hey WC

I believe you accidently posted the first plot twice.......The Golden (Reference) Plot looks the same as the free air plot.

[Panacea Engineering]

Mike,

That could be very well be but I did notice that when I did the Golden it looked almost identicle as the single K-31. I am going to redoo everythuing in the morning, as this was more of a test for me, to see if I could get and save the screen shots. I am totally on Brain Burnout after fooling with this for three hours straight.....! It has been a major learning day for me.....! It is time for some Bud and to sit back and reflect......[H]

[mikebse2a3]

Here is Roy's raw Z-Plot for the KPT-KHJ-LF as a reference for you.

Note: when a driver is loaded in a sealed rear chamber the driver/box's resonate frequency Z peak will increase and also dual parallel drivers will decrease up to 1/2 of the single drivers overall impedance.

The Golden's plot should look very close to Roy's plot.

Alot of work and (brain cells) goes into testing so yes relax and attack it again when you've recharged[]

[Panacea Engineering]

Here is an overlay of Speaker A (Greenish) over the Golden Jubilee. I also updated the previous post that Mike pointed out with a fresh scan of the Golden Jubilee. It appears that the first "spike" goes much lower that the Golden Jubilee and I am presuming that the that spike is the passive or is that cabinet resonance.....? This is where I seriously need interpretation of the scans, as I clearly do not know what I am looking at. I DID only take me an hour or so to figure out how to do the overlay...so I am learning. Each file can have up to 20 panels (memory) so there is plenty of room to do all of the testing that will be needed. The next thing I need to do is to calculate the volume, to do the closed box test. This is getting more fun everyday.....!