SiliconTi
Super Member
Ahh, 'tis true.
Blasphemy: I do not like the Tobin 104T Mods on my Bozaks
- Thread starter SiliconTi
- Start date
Ahh, 'tis true.
Cosmic Pro
Member
Cosmic Pro
Member
Hello there, I just got my first pair of Bozaks, b313's from what I'm reading they are the same components that are in the 302's is this correct? Is so, the capacitors below your referring to would they be same same ones I would need for my b 313's? I appreciate your feedback...
Thanks!!!
Thanks!!!
ello
You are correct: the B-313 uses the same N-10102 crossover as the B-302 and other models.
I own a pair of B-313, BTW.
I suggest you add a midrange bell constructed from a flower pot, as I have elsewhere described. This prevents the woofer from modulating the midrange. You'll need to cover the bell with upholstery batting inside and out to muffle the backwave and prevent reflections and resonance.
Congratulations on your new speakers. When you upgrade the capacitors and change the crossover point you will greatly enjoy them. As I and others have suggested, you may want to omit the attenuation resistor for the tweeters or change it to rheostat; at low volumes it over-attenuates and can require tinkering.
twiiii
Lunatic Member
I bi=amped first using a N-107in 1972. When I got a spectrum analyzer in 75 to balance the woofer to the 209/200Y and finished the system was very flat needing just a touch of boost at 25 hz and a a little subtraction at 50 and 160 due to room resonances. Then everything was dam close to perfect to 4 kHz where a slight roll off began till I got to 10 kHz where the highs headed for the basement, and why I added super tweeters to extend the response to to 18 kHz. I measure the tweeters and super tweeters at 4 ft to get the blend right extending the gradual roll off to prevent room issues and I use a calibrated cardioid mic. Then when I moved to the listening position the highs have continued the nice acoustical roll off. They still can be a bit on the bright side but thats what a treble control is for. I did all this before Tobin came a long. So when I installed my Symphones and 313's in 08 as I expanded to a HT system I continued with the same plan. But only bi amping the front center Symphony and adding a super tweeter with a passive network. Same response only a sooner bass roll off at 35 hz. I left the 313's alone accept to install a small EQ to smooth the bass response leaving the natural response of the 313 and 4005 works best for rear and side channels. The rear symphony now has been bi=amped, but with out a super tweeter because I don't want the speaker calling attention to itself.
I was never fond of Quad . Music composed to come at me from all directions never appealed to me. And like wise for HT I prefer the sounds from the rear channels to be slightly muted as sound would be in real life from the rear.
A few years ago I visited a Bozak owner in my old home town. She had 302's in custom tall cabinets with the tweeters up high near the mid with the Tobin mod and they sounded rather nice. She also had a pair of Modern Symphonys with the Tobin mod and the 8 " mid as I remember. The sound didn't match my older 4000 contemporary Symphonies with Mac tubes, but all in all I couldn't fault them. I did miss the top octave for percussive instruments. The snare and cymbals sounded miles away which was all right for classical music, but wasn't quite right with pop music. Especially with the CW she likes. All my friends that are still with us near by have sold their Bozaks and have moved on. None of them had the Tobin mod. I have recently updated my HT processor and the clarity in the bass below 70 Hz and highs above 5 Khz has really improved. The range from 125 to 500 hz has become more open. So Bozaks can still reveal improvements with todays electronics. choices.
I was never fond of Quad . Music composed to come at me from all directions never appealed to me. And like wise for HT I prefer the sounds from the rear channels to be slightly muted as sound would be in real life from the rear.
A few years ago I visited a Bozak owner in my old home town. She had 302's in custom tall cabinets with the tweeters up high near the mid with the Tobin mod and they sounded rather nice. She also had a pair of Modern Symphonys with the Tobin mod and the 8 " mid as I remember. The sound didn't match my older 4000 contemporary Symphonies with Mac tubes, but all in all I couldn't fault them. I did miss the top octave for percussive instruments. The snare and cymbals sounded miles away which was all right for classical music, but wasn't quite right with pop music. Especially with the CW she likes. All my friends that are still with us near by have sold their Bozaks and have moved on. None of them had the Tobin mod. I have recently updated my HT processor and the clarity in the bass below 70 Hz and highs above 5 Khz has really improved. The range from 125 to 500 hz has become more open. So Bozaks can still reveal improvements with todays electronics. choices.
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drbiggles
I like to pull weeds.
Hey Silicon,
Hang on here, let's take a look. With the original crossover design you'd still need the l-pads, so you are correct. With Tobin's design, you got a Zobel network in the tweeter leg. This smooths out the frequency response of the B200Y tweeters, no more spike up around 9k. This is a good thing. You could very easily put the crossover points for the woofer back to 800Hz and the mid to 2500Hz. You'd just need to move the jumpers and install a 25uF cap in place of the 50uF. The issue with that is that the B209B mid's frequency response isn't smooth as it goes higher up, it gets louder. I've tried this and any imaging and depth you had, goes away. The presentation gets flat and hard on the ears. Pat's changes (all within Rudy Bozak's original designs) brings the mid's crossover point down to about 1250Hz vs 2500Hz. The first order crossover in the Bozaks has a lot of bleed through from driver to driver. So, as the mid goes up in frequency, it doesn't get to darned loud. It very precisely dies out as the tweeters come down to meet it, perfection. This is a great thing, trust me. Pat noticed, with a lot of hard work, that the B199 woofer really doesn't do well as it gets up around 800Hz. As fine as it is, it really performs far nicer down at 400Hz. While the B209B mid isn't perfect down there, it's sure as a hell of a lot better at it than the woofer is. The end result is that the woofer isn't working as hard and is in its sweet spot. The mid is now coming down a tad lower, and trailing off before it starts to yell at you. And the tweeter's spike at 9k is gone. I've done enough listening to all these configurations and more in nearly 2 years than I'd care to admit. Pat Tobin's changes are solid.
That being said, I'm still amazed at how different everyone's ear and listening environment is. Ultimately, you make the choice to what makes your Ear and psyche smile. So, if Pat's changes to Rudy's original design make you mad, then by all means put them back. A few minutes with a soldering iron and 2 25uF caps are all you need.
Biggles
Hang on here, let's take a look. With the original crossover design you'd still need the l-pads, so you are correct. With Tobin's design, you got a Zobel network in the tweeter leg. This smooths out the frequency response of the B200Y tweeters, no more spike up around 9k. This is a good thing. You could very easily put the crossover points for the woofer back to 800Hz and the mid to 2500Hz. You'd just need to move the jumpers and install a 25uF cap in place of the 50uF. The issue with that is that the B209B mid's frequency response isn't smooth as it goes higher up, it gets louder. I've tried this and any imaging and depth you had, goes away. The presentation gets flat and hard on the ears. Pat's changes (all within Rudy Bozak's original designs) brings the mid's crossover point down to about 1250Hz vs 2500Hz. The first order crossover in the Bozaks has a lot of bleed through from driver to driver. So, as the mid goes up in frequency, it doesn't get to darned loud. It very precisely dies out as the tweeters come down to meet it, perfection. This is a great thing, trust me. Pat noticed, with a lot of hard work, that the B199 woofer really doesn't do well as it gets up around 800Hz. As fine as it is, it really performs far nicer down at 400Hz. While the B209B mid isn't perfect down there, it's sure as a hell of a lot better at it than the woofer is. The end result is that the woofer isn't working as hard and is in its sweet spot. The mid is now coming down a tad lower, and trailing off before it starts to yell at you. And the tweeter's spike at 9k is gone. I've done enough listening to all these configurations and more in nearly 2 years than I'd care to admit. Pat Tobin's changes are solid.
That being said, I'm still amazed at how different everyone's ear and listening environment is. Ultimately, you make the choice to what makes your Ear and psyche smile. So, if Pat's changes to Rudy's original design make you mad, then by all means put them back. A few minutes with a soldering iron and 2 25uF caps are all you need.
Biggles
SiliconTi
Super Member
Hey Biggles - one problem - I have the paper mid, not the Al mid. I have the crossovers set as Tobin recommends. I would change them back to stock if it was not such a PITA. Right now they sound good, so I'll leave them alone. (Plus I have pulled the crossovers like 10 times - that is getting old.)
The aluminum cone tweeter is louder than the paper variety, has a higher frequency response, and has a different impedance rise. So the ideal Zobel compensation is not identical for the paper tweeter. The biggest issue you face is that the attenuation set for an aluminum-cone B-200Y/B-200Z will be too much for a paper-cone B-200X, hence the adjustable L-Pad. Which I think I suggested about a year ago?
The stock value is simply too much at low volume. Makes me wonder at what volume Tobin listened. Maybe it was some hearing loss at the high end which would also account for not finding the volume objectionable.
Both tweeters are lacking in the highest registers, which is why a super-tweeter, as Twiiii above noted, is often used to remedy the shortfall.
That's good news. All you'll need to do is adjust the attenuation for your preferred listening volume.
drbiggles
I like to pull weeds.
OH man, I get that. I've ruined screw holes for the backs on so many speakers doing just that. I HATE it. I forgot about your paper mids, sorry about that!
Biggles
Yeah, the problem with most speaker cabinets, and particularly with an infinite baffle cabinet like the Bozaks, is that the back must be in place for testing and plywood readily strips. Which is why JB Weld (or any other epoxy putty or filled epoxy) exists. Plastic makes a far more robust mounting. I've tried threaded inserts and t-nuts, but they are very unforgiving of placement, will strip, and sometimes lose adherence to the surrounding wood and just spin. Which is why I like a filled epoxy. If it is stripped, just add more.
Biggles has, BTW, rebuilt more cabinet screw holes than anyone else here and can tell you what will work and, most importantly, what will not work.
SiliconTi
Super Member
That is a good idea - which I thought of that a year ago....
scorpio333
Active Member
I've got a pair of 302a Colonials that I did the Tobin mods on about a year ago. In the past month or so after moving them to a different room, they've started to annoy me. The highs were missing, the mids screaming, the lows were still spot on. I do have the B200y's mounted on in a separate box on top of the cabinets. I decided to revisit the crossovers in an effort to keep them from the sell pile.
The plan was to use the crossovers externally until I was happy with them. Pulling the speakers out into the room, undoing the rear panel, fiddling, then putting them back together got old fast. When I did the Tobin mods, I installed a bi amp terminal cup on the back panel. I removed the bi amp clips, the bottom was input from amp, the top out to the tweeters. Now with the crossovers outside, the mids go to the top and the woofer go to the bottom connectors. Convenient.
On the crossovers, I put 1/4" female spade connectors on the jumper wires for the mids and woofers to allow quicker changes for testing. I removed all the caps, resistors, and wiring. I cleaned off old solder and tried to neaten things up a bit. When resoldering the caps and resistors, I picked this as my starting point:
From this post:
Except...On crossover 1, I directly connected the 8.2 cap to B200Y #1. On crossover 2 I put everything as above, minus the 7.5ohm resistor. Put crossover 1 on the left, 2 on the right and tested it. The left speaker was a much closer match to my ears. Closer, but now they are a little hot. Moving the tweeters back towards the wall helps, but I see L pads in my future. Just wrapped up changing crossover 2 to match, now to test it out.
I don't see much mention of only using the 8.2 cap on the tweeters, too hot for most?
The plan was to use the crossovers externally until I was happy with them. Pulling the speakers out into the room, undoing the rear panel, fiddling, then putting them back together got old fast. When I did the Tobin mods, I installed a bi amp terminal cup on the back panel. I removed the bi amp clips, the bottom was input from amp, the top out to the tweeters. Now with the crossovers outside, the mids go to the top and the woofer go to the bottom connectors. Convenient.
On the crossovers, I put 1/4" female spade connectors on the jumper wires for the mids and woofers to allow quicker changes for testing. I removed all the caps, resistors, and wiring. I cleaned off old solder and tried to neaten things up a bit. When resoldering the caps and resistors, I picked this as my starting point:
From this post:
Except...On crossover 1, I directly connected the 8.2 cap to B200Y #1. On crossover 2 I put everything as above, minus the 7.5ohm resistor. Put crossover 1 on the left, 2 on the right and tested it. The left speaker was a much closer match to my ears. Closer, but now they are a little hot. Moving the tweeters back towards the wall helps, but I see L pads in my future. Just wrapped up changing crossover 2 to match, now to test it out.
I don't see much mention of only using the 8.2 cap on the tweeters, too hot for most?
The Tobin imbalance, as I've elsewhere noted, was a tradeoff between accuracy (which would have required adjustment to music and volume) and ease of use (i.e. no adjustment). I think everyone experiences the imbalance and seeks a fix (see below).
Something variable is best.
An L-Pad or a rheostat in place of the fixed value, possible with a smaller fixed value to establish a minimum attenuation level. Use your favorite means to adjust the volume for balance.
Another option is to separate the tweeters and bounce one off the rear wall to diffuse the sound. The success of that depends upon your room, of course. You'll still need some sort of volume control.
Two issues are being conglomerated in that question:
(1) Impedance rise near resonance. That is what the Zobel cures.
(2) Attenuation to match volume of tweeters to midrange and woofer. This the voltage divider portion.
(2) Attenuation to match volume of tweeters to midrange and woofer. This the voltage divider portion.
So one could remove the attenuator but leave the Zobel,which really should be present.
I suggest using a variable attenuation to address the sound at varying power levels. Whatever you like, but it should be variable.
drbiggles
I like to pull weeds.
Hey man,
Hmm, there should be balance. Even with the darker tweeters. Check the polarity on your mids, should not be out of polarity. In the early to mid 60's Rudy wired the mids out of phase to make the mid more forward. Double check your inductor lug connections. Both the woofer and the mid should be connected to the ones closest to the inductors. This will cross the mid over at approximately 1250Hz vs the original 2500Hz. The mid has an impedance rise and will get far too forward when crossed over that high. And, everyone has an issue with the tweeters being too dark when the Pat Tobin 104T modification is completed. As Retrovert figured out, remove the 7.5ohm resistor in the tweeter network and install an 8ohm 15 watt l-pad instead. Use your meter to find out which of the two prongs to use to get an 8ohm variable resistor. It will be the center one, then either the left or right lug.
Biggles
Hmm, there should be balance. Even with the darker tweeters. Check the polarity on your mids, should not be out of polarity. In the early to mid 60's Rudy wired the mids out of phase to make the mid more forward. Double check your inductor lug connections. Both the woofer and the mid should be connected to the ones closest to the inductors. This will cross the mid over at approximately 1250Hz vs the original 2500Hz. The mid has an impedance rise and will get far too forward when crossed over that high. And, everyone has an issue with the tweeters being too dark when the Pat Tobin 104T modification is completed. As Retrovert figured out, remove the 7.5ohm resistor in the tweeter network and install an 8ohm 15 watt l-pad instead. Use your meter to find out which of the two prongs to use to get an 8ohm variable resistor. It will be the center one, then either the left or right lug.
Biggles
Biggle's comment about the reversed midrange reminded me that this would account for your forward midrange report.
The Tobin mod undoes that, but this does not mean your midrange is properly wired.
Here's what I've elsewhere written about that change.
The rationale from Bob Betts, Rudy Bozak's right-hand man and the co-designer of the famed Bozak 909/919 preamp and 929/939 amps among others:
Tobin's commentary:
The Tobin mod undoes that, but this does not mean your midrange is properly wired.
Here's what I've elsewhere written about that change.
The rationale from Bob Betts, Rudy Bozak's right-hand man and the co-designer of the famed Bozak 909/919 preamp and 929/939 amps among others:
Tobin's commentary:
