Blasphemy: I do not like the Tobin 104T Mods on my Bozaks
- Thread starter SiliconTi
- Start date
I was digging through my quote file looking for something and found this gem, which I thought I would share.
This thread is populated with enough Bozak fans to warrant here posting it for the other Bozak Cult members.
Enjoy:
This thread is populated with enough Bozak fans to warrant here posting it for the other Bozak Cult members.
Enjoy:
"A Glorious Time: AR's Edgar Villchur and Roy Allison"
by David Lander
Stereophile (2005, Jan 6)
David Lander: The AR-1W was a woofer-only unit. Arthur Janszen used to demonstrate his electrostatic tweeter in combination with it.
Edgar Villchur: Henry [Kloss] knew him, and we went to his house, and Arthur compared the AR with a giant, four-woofer Bozak. His decision was just as quick as Henry's. It was an obvious decision. How many people were going to buy this giant thing when they could buy his tweeter with an AR?
by David Lander
Stereophile (2005, Jan 6)
David Lander: The AR-1W was a woofer-only unit. Arthur Janszen used to demonstrate his electrostatic tweeter in combination with it.
Edgar Villchur: Henry [Kloss] knew him, and we went to his house, and Arthur compared the AR with a giant, four-woofer Bozak. His decision was just as quick as Henry's. It was an obvious decision. How many people were going to buy this giant thing when they could buy his tweeter with an AR?
greatoldone
Member
I agree! Adding the Janzen Tweeter Array to any of the classic AR's, Advents, KLH's certainly improves their treble and dispersion!
An electrostatic also improves the Bozak. It is interesting that Rudy never saw this as desirable. Particularly in the days of the B-200X. True, the source material was generally lacking, but even in the realm of 2,500 Hz to 10,000 Hz the JansZen would have made the Bozak shine. The Bozak customers certainly could have afforded to add a JansZen 65 to the setup and certainly appreciated better audio.
SiliconTi
Super Member
I have had a chance to audition some Wilson ALEXX's - yeah, I hate all my speakers now.
So, I dragged the Bozaks and stacked them onto of my La Scalas (not an easy task!). This brings the tweeter to ear level when sitting down. Changed the entire speaker's "voicing". If you sit in the sweet spot, they image very well with good sound stage. Bass is a bit shy, of course, but still what is there is accurate.
I think I'll add an external tweeters, probably planers. Let the fun continue!
EDIT: running them with the GemTune tube amp (about 8 watts).
So, I dragged the Bozaks and stacked them onto of my La Scalas (not an easy task!). This brings the tweeter to ear level when sitting down. Changed the entire speaker's "voicing". If you sit in the sweet spot, they image very well with good sound stage. Bass is a bit shy, of course, but still what is there is accurate.
I think I'll add an external tweeters, probably planers. Let the fun continue!
EDIT: running them with the GemTune tube amp (about 8 watts).
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Yes, this is a huge issue. I've always said that if, like crickets and grasshoppers, we heard with our knees then we'd experience excellent imaging. Only the smaller Bozaks placed tweeters lower (B-313, B-302, and B-305, as I recall) but two of the small bookshelfs (B-503, B-801) did not. I suspect this was slot-loading the woofers to put weight on the cone and thereby extend the low-end response. The bookshelf cabinets are smaller and loading the B-199 was likely suboptimal in that size.
A caveat for your placement, however. When speakers are stacked the lower cabinet resonates, distorting the output. In this case it is like placing the speaker on the floor and having the floor, joists, and rest of the home structure absorb, damp, re-radiate sound. The tuning of the La Scala cabinet will affect this sound. As others have described, placing Bozaks on stands greatly improves the accuracy of the low end and prevents peculiar one-note resonance issues.
I would suggest using sonic isolators between the stacked cabinets and, furthermore, covering the fronts of the unused loudspeakers to avoid having the cones act as sound dampers. (The cone, after all, is a moveable piston and it takes energy to move it, hence absorption and damping.)
I am not sure why your bass is too low. The Bozaks are capable of delivering considerable bass. Is your amplifier doing some low-end rolloff, because of coupling or bypass capacitor issues, maybe?
Great idea. Moving the tweeters is always reported as an improvement.
Might want to damp the backwave from the planar or ensure it is baffled to avoid comb artifacts. Also should be far enough away from the wall so that reflections are not a problem. Are you going to use one of the AMT clones I described earlier? If so, only the larger units are suitable as the smallest one is, I believe, limited to 3,500 Hz at the low end.
Don't forget to time-align the repositioned tweeters by positioning front-to-back at roughly at the acoustic center of the midrange driver. Yes, I am fully aware that the Bozak doesn't perform any time alignment (I am going to redo mine at some point to remedy this), but you'll hear misalignment more with the midrange than the woofer.
SiliconTi
Super Member
Hey Retro,
On the stacking: La Scalas only have a woofer cone, though it is setup as a horn, so not worried. I have isolators between the speakers. I think the bass is shy as I am used to them flat on the floor and think some "bounce" was occurring - which is no longer there. Music with solid bass still has it; after some listening time, I feel it is not lacking, but rather more true to the recording.
AMT: yes, the one you recommended in a small enclosure setup to time align is what I am thinking.
I am starting an AR-3a project soon, but I'll order parts to work on them at the same time.
On the stacking: La Scalas only have a woofer cone, though it is setup as a horn, so not worried. I have isolators between the speakers. I think the bass is shy as I am used to them flat on the floor and think some "bounce" was occurring - which is no longer there. Music with solid bass still has it; after some listening time, I feel it is not lacking, but rather more true to the recording.
AMT: yes, the one you recommended in a small enclosure setup to time align is what I am thinking.
I am starting an AR-3a project soon, but I'll order parts to work on them at the same time.
Ok, so it's not exactly missing. You wrote, "Bass is a bit shy, of course, but still what is there is accurate.". So I think what you meant, not to put words in your mouth, is that bass is not boosted beyond the level of source material. Accurate reproduction is one of the key Bozak features, in that the sound is reasonably flat with respect to the source material. An EQ will easily fix the bass.
I would try that in a lined cardboard box (hey, it's an experiment, no need to build an enclosure) and see how you like it. If not, it is returnable. The AMT is an interesting driver. Since it is off patent I would expect it to be comparable to the HEIL, as is reported. My personal preference is far better off-axis dispersion of the JansZen electrostatics compared to the ribbons or soft-dome, but the electrostatic is, of course, bulkier, more expensive, and requires power supplies. The soft-dome is another excellent option. Biggles had excellent results with the SEAS.
I don't know anyone who has, as I've suggested, added a piezo supertweeter at 10 kHz and there cut the Bozak cone tweeter. This is another interesting test which would give us some data. I suspect the soft-dome will handily beat that combination, as would, of course, the AMT. But, having written that, the question of how well the B-200Y would perform with its upper-end removed is a good one and an open one.
The original Bozak foot height for the B-302 was, I believe, about 3 inches, but this varied by model. A dry 2x4 is approximately 1.5 x 3.5 inches. So that's about perfect if you want to quickly and easily test those two heights. As always, isolation is a must, and I would not build a solid stand (four sides) underneath the cabinet as this creates its own resonance issues. Just two edges.
But no reason exists why you can't go higher! Bookshelf speakers were put on the top of bookshelves. I've seen reports of the B-302 put on stands over two feet high. Depends on where you are sitting. I've used high stands with my Karlsons, but those are full-range drivers low mounted. Made a HUGE difference. Others have similar experiences with higher stands.
Anywhere between about three and six inches would likely work for you. I suggest trying a few different heights and seeing what best works in your space. You might not experience any significant difference between three and six, particularly with relocated tweeters.
This is a "try it and see" situation. Sorry I don't have better guidance than the above.
SiliconTi
Super Member
These look like a good match - thoughts? I'll setup a simple first order crossover at 7KHz.
https://www.parts-express.com/peerless-by-tymphany-bc25sc06-04-1-textile-dome-tweeter--264-1028
https://www.parts-express.com/peerless-by-tymphany-bc25sc06-04-1-textile-dome-tweeter--264-1028
drbiggles
I like to pull weeds.
Hey man,
Dang, looks pretty darned okay from here. Its got a pretty sharp impedance rise between 10 and 20k. The sensitivity is pretty close. Between the impedance rise and being more sensitve, you may wasnt to consider adding a padding resistor or an l-pad. Iam interested to know what it sounds like.
Biggles
Dang, looks pretty darned okay from here. Its got a pretty sharp impedance rise between 10 and 20k. The sensitivity is pretty close. Between the impedance rise and being more sensitve, you may wasnt to consider adding a padding resistor or an l-pad. Iam interested to know what it sounds like.
Biggles
First, that's 4 Ω. So you'll need two in series. Was that the plan?
Few questions.
Why are you crossing so low, i.e. 7 kHz? You are overlapping the existing B-200Y with this? You will run into peculiar impedance at the high end, particularly if you do not cut the B-200Y. The two will be in parallel at that point. You will also have comb artifacts if you keep the existing tweeters in place, because they are geographically separated further than 1/4 wavelength. Plus you'll experience the full non-linear behavior of the B-200Y in a region where the soft-dome is linearly operating.
You might want to try a driver which could, for experimental or main purposes, replace the B-200Y on its own. Try that. Also try having it pick up at about 10 kHz and cut the B-200Y with an inductor. (Build a band-pass for the B-200Y, exactly like a midrange.)
Final thought. I don't trust a tweeter that inexpensive, given that the SEAS and comparable fabric domes are typically 2.5 times the price and up. What is the difference? I don't know. But it surely exists.
Few questions.
Why are you crossing so low, i.e. 7 kHz? You are overlapping the existing B-200Y with this? You will run into peculiar impedance at the high end, particularly if you do not cut the B-200Y. The two will be in parallel at that point. You will also have comb artifacts if you keep the existing tweeters in place, because they are geographically separated further than 1/4 wavelength. Plus you'll experience the full non-linear behavior of the B-200Y in a region where the soft-dome is linearly operating.
You might want to try a driver which could, for experimental or main purposes, replace the B-200Y on its own. Try that. Also try having it pick up at about 10 kHz and cut the B-200Y with an inductor. (Build a band-pass for the B-200Y, exactly like a midrange.)
Final thought. I don't trust a tweeter that inexpensive, given that the SEAS and comparable fabric domes are typically 2.5 times the price and up. What is the difference? I don't know. But it surely exists.
SiliconTi
Super Member
Good point on the 7K crossover. What is the crossover point now (if you know of the top of your head)? I'll just set it above that to "fill in" what is missing and balance it as needed.
Cost: It gets good reviews and will work well as a testing platform. I also like the freq. response.
The plan was to use one as a test and add the second if I like it. Yes, that makes a very low load, but my Mac can drive 2 Ohms all day long, so it will be fine until I dial it in.
Cost: It gets good reviews and will work well as a testing platform. I also like the freq. response.
The plan was to use one as a test and add the second if I like it. Yes, that makes a very low load, but my Mac can drive 2 Ohms all day long, so it will be fine until I dial it in.
I don't have an exact value. Here's what I can say from observing the frequency response charts. I'll give you my reasoning, which has a lot of guesswork in it, so it can serve as a discussion or research point.
Above about 10 kHz the B-200Y gets very spikey and non-linear. It begins to drop off in SPL at this point. So my guess—you are urged to experiment—the driver begins to lose some power and linearity slightly below this point, even though the response chart does not necessarily reflect this. Remember, the chart is for a sine wave of a single frequency that is linearly changing, so that may not reflect how the driver performs with actual music varying all over the place.
You'll see the same spikey behavior with the Electro-Voice T-35 tweeter, which is why I somewhere recommended that this not be treated as a substitute. The Sphericon could be used, if you wanted to go vintage phenolic compression, but it starts to misbehave above about 10 kHz, too. Common issue for tweeters of that timeframe.
So if one is using both the Bozak and soft-dome tweeters, I think I would cross at somewhere in the range of 8 kHz to 10 kHz. Lower is likely better, because the decline in SPL of the B-200Y will not cause a sudden rise in volume as the soft-dome takes over. But it probably is not very critical.
Lots of conjecture there. Experimentation is needed.
Another point. Why continue with the B-200Y if a substantially better tweeter is available? This isn't snark, by the way, it's a question. One could argue that the B-200Y offers a sound response balanced to the other drivers. Maybe. But with an L-Pad the new tweeter can be dialed in to the proper point, so mismatches in volume should not be an issue. Besides, many older listeners with some hearing loss prefer louder treble. (Again, not snark, just a fact that ears wear out from too much street noise, too much jackhammer exposure, and too much Motorhead.) One could also argue the frequency response of the B-200Y is perfect for jazz, swing, and other 1950s music. Yeah, ok, but purity of sound is even better, so why stop at what music in the 1950s could reproduce? Classical has better response now, too.
I've hear great things about the SEAS and other soft-domes, I don't know anything about this one.
Doesn't matter if your amplifier will arc-weld. What matters is the nominal impedance determines the value for the crossover capacitor, and you cannot use the capacitor currently present in the crossover because the nominal impedance has changed.
This change of a factor of two in impedance will similarly change the crossover frequency by a factor of two and you will observe a very different sound because your tweeter crossover frequency is now way off, moving up from roughly 2,500 Hz to about 5,000 Hz. You now lost your upper treble. Bleh.
Driver impedance matters.
SiliconTi
Super Member
Good info.
I'll actually be using an external crossover just for the add-on tweeter (hence the load on the amplifier I spoke about).
I'm not opening these up again. I'll keep the B-200Ys in place - I have an L-Pad on them so I can dial them in/out as required.
Your reasoning is similar to mine, hence why I thought 7KHz would be a good starting point. I can build a dead simple first order crossover to allow easy experimentation, and see what happens after that.
I'll actually be using an external crossover just for the add-on tweeter (hence the load on the amplifier I spoke about).
I'm not opening these up again. I'll keep the B-200Ys in place - I have an L-Pad on them so I can dial them in/out as required.
Your reasoning is similar to mine, hence why I thought 7KHz would be a good starting point. I can build a dead simple first order crossover to allow easy experimentation, and see what happens after that.
Arrrrgh, matey, beware tha amplitude distortion and comb artifacts as ya steer ya ship 'tween them craggy peaks. Others ha' tried, and failed.
Paralleling a second speaker of lower impedance and dumping all of the energy going to the first speaker will dramatically alter the current available to drive the second tweeter. You've added a voltage divider which is dumping energy which reduces the available output level to the tweeter you want to power. Expect the sonic terrors of low treble output and distortion as the amplifier is excessively loaded in that range. This may rob power from other parts of the spectrum because the impedance is now lower in that region.
Should the B-200Y overlap a second tweeter distortion will result: time-alignment (the same frequency band is now arriving at different times and different angles with different reflections) and comb artifacts (signals combine, reinforcing and cancelling). Comb artifacts are a problem in TMT configurations for center channels and the interwebs will provide you explanations, diagrams, charts, and photos of people covering their ears whilst screaming.
I suggest you ensure the B-200Y is completely out of circuit using a switch, instead of merely dumping its current to accomplish the same goal.
Finally, by placing only the new speaker on top of cabinet the sonic differences are not apples to apples, so the entirety of variables in the "improvement" have not been reduced to changing one factor at a time for analysis. The results can be misleading. Not sayin', just sayin'.
Hmmm. My reasoning is:
Experiment 1: Replace the B-200Y in its entirety, having a switchable option for soft-dome vs. B-200Y. A Kierkegaardian either-or situation.
Experiment 2: Build a bandpass for the B-200Y (existing tweeter capacitor, but adding an inductor to limit ceiling), thereby keeping the signature Bozak sound to somewhere 8 kHz to 10 Khz thereby removing spikey and non-linear behavior, then transitioning to a supertweeter of some sort, also using a bandpass filter to cut the high end at 30 kHz just in case your amplifier outputs ultrasonics. The 6 dB/octave rolloff won't eat into the 20 kHz high end. This creates a split tweeter which might cause alignment artifacts if the positioning is radically different.
Experiment 3: Same as Experiment 1, but also build a bandpass for the B-200Y (same capacitor, but adding inductor to limit ceiling) to limit the upper-end the B-200Y and remove spikey behavior.
Experiment 2: Build a bandpass for the B-200Y (existing tweeter capacitor, but adding an inductor to limit ceiling), thereby keeping the signature Bozak sound to somewhere 8 kHz to 10 Khz thereby removing spikey and non-linear behavior, then transitioning to a supertweeter of some sort, also using a bandpass filter to cut the high end at 30 kHz just in case your amplifier outputs ultrasonics. The 6 dB/octave rolloff won't eat into the 20 kHz high end. This creates a split tweeter which might cause alignment artifacts if the positioning is radically different.
Experiment 3: Same as Experiment 1, but also build a bandpass for the B-200Y (same capacitor, but adding inductor to limit ceiling) to limit the upper-end the B-200Y and remove spikey behavior.
