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Multi-Way Conventional loudspeakers with crossovers

Need Help: Designing 12" Tannoy + 15" Woof
Need Help: Designing 12" Tannoy + 15" Woof
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Old 19th November 2019, 12:44 AM   #31
KrautNotRice is offline KrautNotRice  United States
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Originally Posted by lousymusician View Post
I'm sure that you would know if the diaphragm was a ring radiator, there would have been a hole in the middle.

How did you implement the BSC? Any other crossover tweaks?

Bill
When the tweeter was apart, the phase plug didn't separate from the dome, so I couldn't see the middle of the dome. But the part of the dome I saw definitely looked like a normal dome. I've got some SB Acoustics SB29 dual ring radiators, and their shape looks nothing like what I saw of the Tannoy dome.

About the crossover, I'm not done tweaking yet, just started actually.
Before implementing the BSC, I thought the tweeter needed a good bit of series padding, but before desoldering the entire PCB and rebuilding it point-to-point (to be able to pad the tweeter individually), I thought I'd first try some 'wholesale' BSC to test it out.
What I did was very crude, I simply placed a 2.3 mh inductor with a parallel 5.2 ohm resistor in front of the entire factory crossover for 6db of BSC. Of course that's not ideal, and it did muffle the top end quite a bit, in other words it degraded the top end besides just padding it. That did do wonders for the bass though, so I know I'm onto something.
Now my next step will be to desolder all components from the PCB, to rebuild everything point-to-point to be able to tweak the woofer and tweeter separately. Once I do that, the signal for the tweeter no longer has to travel through all of the woofer's BSC and filter components first.
I was tempted to simply place an l-pad on the tweeter for experimenting, but the ones I've got on hand are 8 ohms, and the tweeters do have that 8.2 ohm parallel resistor built into the factory crossover dropping the tweeter's net resistance to less than 4 ohms.

Last edited by KrautNotRice; 19th November 2019 at 12:47 AM.
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Old 3rd December 2019, 01:30 AM   #32
KrautNotRice is offline KrautNotRice  United States
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Finally have some time to mess with this again.
I'm about to desolder all of the xo components from the pcb and arrange everything on cardboard with point-to-point wiring / jumpers, for convenient tweaking.

HUGE FAVOR, if anyone could chime in with some help regarding BSC:
The stock xo has no baffle step compensation, bc they're ceiling speakers. What is the simplest way I can implement BSC?
Do I really have to add a second inductor (with parallel resistor) to the woofer filter, or can I somehow achieve BSC using the woofer's existing 1.75mh inductor?

This is the stock xo schematic:

+ (from amp) > 1.75mh series > 25.0uf parallel > LF

+ (from amp) > 6.8uf series > 0.22mh parallel > 8.2 ohm parallel > HF

I hope that makes sense.
That 1.75mh inductor is very close in value to what the BSC would need, can I use the existing coil to implement BSC by adding a parallel resistor across the 1.75mh inductor?
If not, and I have to add an additional inductor for BSC, do I put it in place before the low-pass filter section?
Thanks for any input.
I've also played the woofer full range, to hear exactly what the low-pass filter does, and it's not radically different, the woofer just plays a little bit higher but there is no audible break up or shoutiness from the woofer full range.

My main problem at this point:
With stock crossover, there's way too much mids. Does the HF 6.8uf + 0.22mh seem like it's accentuating the mids? Wouldn't reducing the capacitor size reduce the output near the xo frequency?
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Old 3rd December 2019, 04:45 AM   #33
KrautNotRice is offline KrautNotRice  United States
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OK I had a chance to desolder one of the crossovers, and play some low level music through the speakers while swapping around components a bit.
I'm using jumper leads with alligator clips to connect stuff point-to-point.
First impression is that the speaker I'm working on seems to play louder and have more bass, so perhaps the crossover on a pcb robs some current / adds restriction?
For starters, I concentrated on the HF high pass, as that is the most glaring issue. So I reconnected the factory low pass as it was with jumper leads.
I briefly tried whether or not a resistor across the woofer's inductor would do anything remotely like BSC, but it didn't to my ears.
On the stock crossovers, the tweeter level seems to be louder than the woofer, so I tried a series resistor before the high pass capacitor, but seemingly that robbed some top end sparkle as well as reduced the level of the HF. Interesting.
I just grabbed a simple 4uf cap as high pass for starters, as the factory 6.8uf plus 0.22mh seems to emphasize the mids way too much.
Lots of playing around to do when I have more time.
A couple tests I'm planning next are:
-Running the high pass filter with the stock components just point-to-point instead, to see if that sounds better.
-Adding series padding to that to see if it is merely out of balance, but fine otherwise.
-Play with smaller caps than 6.8uf, with and without the factory 0.22mh shunt inductor.
-Play with impedance correction on the tweeter

Also I noticed while undoing the components from the stock pcb, that the 8.2 ohm resistor was actually behind the 0.22mh inductor going to ground.
I will say that with one speaker running the stock xo, and the other one running my science experiment with stock low pass point-to-point and a single 4uf cap as high pass, the bass is deeper, the speaker louder, and has more top end sparkle.
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Old 3rd December 2019, 06:05 AM   #34
lousymusician is offline lousymusician  United States
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KNR,

I have my pair of these drivers up and running now. For the record they are Tannoy part 3198, so not the same drivers Dave was looking at.

The drivers went into recycled boxes of about 2.5 cubic feet / 75 liters. The boxes are routed for 4" abs ports, but the best tuning turned out to be with the ports removed entirely, so a 4.5" x 3/4 " port.

Still very light on bass without bsc, so REW, Umic and minidsp to the rescue. A high shelf of 8dB, q=0.7 at 160 Hz flattened out the bass. Yeah, that's a lot of bsc. A couple of notches at 4500 and 10,000 smoothed out the highs a bit. The tweeter rolls off quickly after 10k, fans of top end sparkle would likely be dissapointed. My hearing is pretty well gone at 10k, so i can let that slide. The smoothest response is slightly off axis so I have them toed in to cross in front of my listening position. There's still a peak that adds an unnatural bite to certain female voice notes that I need to ID and correct.

Next up was plugging the ports and adding woofers. I'm using what I have, 10" NHT subs I got at Burning Amp many years back, in small sealed boxes with a Linkwitz transform to reduce the system q and give a slow roll off.
A couple of notches are needed to minimize nasty room modes at 40 and 70 Hz. The woofers are far less sensitive than the Tannoys, which have to be attenuated 10dB (on top of the dB bsc cut) to get them down to the woofers' level. Makes for a lousy gain structure and limits the max volume to not all that loud. I need a higher gain woofer amp, more sensitive woofers, or both. Still pondering my next step there. For now I'll keep the bottom octave and live with the available volume. If Santa brings me a bass amp, I'll bypass the passive crossovers and try bi amping the Tannoys.

The good stuff: they are efficient and dynamic sounding, have a pretty wide listening window. Tannoy's crossover works well, the transition between drivers is smooth. They do a pretty good job of sounding like a big single driver which is IMO is the reason for going coax in the first place. I figure I'll get my money's worth out of them in fun and the process of learning how to get the best from them.

Bill
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Old 3rd December 2019, 04:01 PM   #35
lousymusician is offline lousymusician  United States
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OK, a little more info now that I'm on the big PC instead of a tablet.

First, TS parameters taken with the S&L Woofer Tester 2:

Completed: Sat Nov 30 14:00:00 2019
Drive level 87.500% [3.044 mA]
Sine,LoZP(LV/LA)->Vas,27 pts
;------------------------------------------------------------------
Re = 4.7495 ohms
Fs = 107.9636 Hz
Zmax = 31.1768 ohms
Qes = 0.7653
Qms = 4.2583
Qts = 0.6487
Le = 0.5515 mH (at 1 kHz)
Diam = 260.0000 mm ( 10.2362 in )
Sd = 53092.9118 mm^2( 82.2942 in^2)
Vas = 22.4013 L ( 0.7911 ft^3)
BL = 12.7882 N/A
Mms = 38.8463 g
Cms = 55.9417 uM/N
Kms = 17875.7441 N/M
Rms = 6.1882 R mechanical
Efficiency = 3.4612 %
Sensitivity= 97.4102 dB @1W/1m
Sensitivity= 99.6747 dB @2.83Vrms/1m
Krm = 6.410E-03 ohms Freq dependent resistance
Erm = 667.902E-03 Rem=Krm*(2*pi*f)^Erm
Kxm = 59.093E-03 Henries Freq dependent reactance
Exm = 506.605E-03 Xem=Kxm*(2*pi*f)^Exm
;------------------------------------------------------------------
Ftest = 77.265 Hz
Ftest/Fms = 0.7157
Test Mass used = 37.0000 g (Equal to 7.4 nickels)
Test Mass (Ft=Fms*0.90) = 9.112 g (Add -27.888g for Ft=97.167)
Test Mass (Ft=Fms*0.75) = 30.214 g (Add -6.786g for Ft=80.973)

The test mass was a ring of Mortite around the tweeter. I'll retest some time with more hours on the woofer and probably a lighter test mass. Main takeaway, high Fs and Qt. These might work well in an open baffle with a suitable woofer, and in a bigger room than my 11 x 14 foot den. Might even try it myself just for kicks.

Attached are WinISD simulations based on the measured parameters and my test box, and the simulated baffle step from Edge. The cabinet height in Edge includes the woofer box on which the test cabinet sits, which also gets the Tannoy up to ear height.

Bill
Attached Images
File Type: jpg Tannoy 3198 Win ISD.jpg (186.8 KB, 48 views)
File Type: jpg Tannoy 3198 edge.jpg (226.4 KB, 49 views)
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Old 3rd December 2019, 06:06 PM   #36
KrautNotRice is offline KrautNotRice  United States
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Quote:
Originally Posted by lousymusician View Post
KNR,

I have my pair of these drivers up and running now. For the record they are Tannoy part 3198, so not the same drivers Dave was looking at.

Bill
Thanks so much for that info!!
So I'm thinking I should concentrate on properly implementing BSC before messing with the high pass perhaps.
Regarding break in: I noticed a HUGE difference after break in for the tweeter, after letting the speakers play for a week straight. It still rolls off, but no longer at 10k. The phasiness I noticed initially also disappeared after break in.
For the woofer, I played 10 hours of 30hz sine wave and it also made a noticeable difference for the better.
My test cabs are 48 liters tuned to 53hz via 3 x 2" ports.
I'm real hesitant to put them in bigger cabs, as the woofers' fs is supposed to be around 60hz they will most likely always need helper woofers or stereo subs.

For your NHT subs, it seems like all you need is a more powerful sub amp(s). PE had some buyouts recently with VERY attractive pricing.

I've got several inductors and many resistors on hand of different values to play around with BSC, my concern is just that the gauge on those inductors is too small, so I'm concerned that once I settle on a combo that works well, and I go to order the appropriate gauge inductor that it will be different sounding, but we'll see.
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Old 3rd December 2019, 06:31 PM   #37
KrautNotRice is offline KrautNotRice  United States
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Quote:
Originally Posted by lousymusician View Post
OK, a little more info now that I'm on the big PC instead of a tablet.

Bill

Oh one thing I forgot to mention is that even after break in of the tweeters, which like I said made a huge difference in the right direction, I'm still planning on running my pair of super tweeters with these Tannoys. They are just missing that very top end sparkle.
The Tannoy labels on my shipping boxes also said Driver Type 3198, I just couldn't find ANY info on 3198 online. Could it be that these drivers are just the V12 / i12 type woofer with a newer tweeter?
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Old 7th December 2019, 01:36 AM   #38
KrautNotRice is offline KrautNotRice  United States
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I'm playing with the added BSC circuit and started a separate thread for XO help with that:
Need help: Adding BSC to passive 2 way Tannoy 12"
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