Let's get back on-topic and recap where we are. 🙄
This is about investigating an upgrade to the Advent which mirrors Speaker Dave's effort with the Acoustic Research AR4x. This was phivates suggestion.
I take it everybody knows what that Acoustic Research AR4X 8" bass plus 1" cone tweeter speaker looked like. Bit of a classic. But overly lively to some ears. Some issues at the low crossover.
Dave did a crossover which he feels worked much better. Below.
I feel I've said enough at this point.
This is about investigating an upgrade to the Advent which mirrors Speaker Dave's effort with the Acoustic Research AR4x. This was phivates suggestion.
I take it everybody knows what that Acoustic Research AR4X 8" bass plus 1" cone tweeter speaker looked like. Bit of a classic. But overly lively to some ears. Some issues at the low crossover.
An externally hosted image should be here but it was not working when we last tested it.
Dave did a crossover which he feels worked much better. Below.
I feel I've said enough at this point.
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You'll build a bridge and get over it. A silent forum is not real functional. Besides, new enthusiasts arrive daily and benefit from what the old hags consider beneath their haughty consideration. As for the pace of things, well Steve you haven't been here for my week of auto mechanic pensioner expletive enhanced cooling system refurb on the speaker retriever minivan I'm downsizing into.
My Advent tweeters' DCR is as advertised. I also have Advent/3's which have 2-3 ohm dcr cone tweeters. You could help by referring us morons to a filter primer which plainly demonstrates, with graphs please, how these pesky things do what they do. Some of us are disabled learning-wise, but our love of music, and lesser interpretations of reality, is not encumbered. Butterworth? Bessel??
My Advent tweeters' DCR is as advertised. I also have Advent/3's which have 2-3 ohm dcr cone tweeters. You could help by referring us morons to a filter primer which plainly demonstrates, with graphs please, how these pesky things do what they do. Some of us are disabled learning-wise, but our love of music, and lesser interpretations of reality, is not encumbered. Butterworth? Bessel??
Hope you're still interested in this upgrade issue, phivates! 🙂
I've been pondering Speaker Dave's update to the Acoustic Research AR4X. He's addressing the roughish peak at (1.2kHz) crossover really.
What he's done, IMO, is give the woofer a lot more rolloff at 2kHz (around 6dB) with the Zobel. This must be good, because those of us who have heard these speakers always disliked the cone breakup from the woofer.
You don't then need to do a lot to the tweeter filter, but you can implement a second or third order now with good phase. Which again must be a good thing, because anything you do for steeper rolloff with a tweeter gives it an easier ride.
The Advent's crossover is a bit higher I believe, but the idea remains good. I'm really fairly clueless what values are appropriate here, but the Zobel must be around 40uF and 7.5R for a 6 ohm DC woofer.
I've been pondering Speaker Dave's update to the Acoustic Research AR4X. He's addressing the roughish peak at (1.2kHz) crossover really.
What he's done, IMO, is give the woofer a lot more rolloff at 2kHz (around 6dB) with the Zobel. This must be good, because those of us who have heard these speakers always disliked the cone breakup from the woofer.
You don't then need to do a lot to the tweeter filter, but you can implement a second or third order now with good phase. Which again must be a good thing, because anything you do for steeper rolloff with a tweeter gives it an easier ride.
The Advent's crossover is a bit higher I believe, but the idea remains good. I'm really fairly clueless what values are appropriate here, but the Zobel must be around 40uF and 7.5R for a 6 ohm DC woofer.
My thanks to the mods for cleaning up some of the junk posts here. Hopefully, those who made them and now notice their absence should take note.
The Advent is around 4.5 DCR. You need to get yourself a pair. The BBC wasn't the only game on planet back in the day, but of course you've revealed your soft spot for AR already. I started out with AR4x and Dyna SCA35 but now I'm ready for the next big non vented thing. Not a fan of hooters; I was breast fed and then moved on.
And I'm sticking to my story on the basket damping necessity on these systems.
And I'm sticking to my story on the basket damping necessity on these systems.
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I remember being incredibly impressed by the AR4X. They seemed to go louder and louder without distortion. 🙂
We had a really good thread going about classic monitor designs, and what the secret sauce in them was. In AR's case, I decided it was Acoustic Suspension and cone tweeters.
Hence I have had this WLM La Scala design in mind for a long time:
WLM, or reviewers anyway, say they cross that Visaton TW70 tweeter over at 1.2 kHz, though I find that hard to believe. But it may be a modern reincarnation of the AR4X.
FWIW, here's a rough sim of what the AR4X Zobel and tweeter filter modification does, since you asked for graphs. The Fs of the TW70 is 1400Hz.
We had a really good thread going about classic monitor designs, and what the secret sauce in them was. In AR's case, I decided it was Acoustic Suspension and cone tweeters.
Hence I have had this WLM La Scala design in mind for a long time:
An externally hosted image should be here but it was not working when we last tested it.
WLM, or reviewers anyway, say they cross that Visaton TW70 tweeter over at 1.2 kHz, though I find that hard to believe. But it may be a modern reincarnation of the AR4X.
FWIW, here's a rough sim of what the AR4X Zobel and tweeter filter modification does, since you asked for graphs. The Fs of the TW70 is 1400Hz.
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Basket ringing is an interesting and unwanted factor IMO. Of course, Acoustic Research used to mount their drivers on a tar-like gasket in the days of Edgar Villchur, which looked incredibly messy, but probably did something toward damping. They may have overlooked this with later designs like the AR6 which I didn't like at all. Below are the early AR4x drivers, AFAIK.
Those of us who modify crossovers a lot often notice that the "Magic" of a design can be ruined by small changes like adding attenuators or near-Zobels in the shunt arm too.
You often get a trade-off between a more revealing speaker and some unpleasant harshness or loss of detail. I won't go on about some higher order filters, but notice that the Dynaco A25 tweeter sees quite a high source impedance around 12R, so is less tightly coupled to the chassis. The chassis can ring without it finding its way to the diaphragm.
My experiments with this factor are ongoing. 🙂
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A friend of mine who does reviews for 6 moons has a pair of La Scala's that I have listened to and compared to my "Intimates" during an afternoon listening session. The WLM's are very efficient and have a very simple crossover. I think it's 1st order elect.
I have also done some experimenting with AR4x's. Visit here for details on my work with phenolic ring tweeter replacements and xover mods that include a post showing similarities in performance outcome very similar to speaker Dave's.
AR4x tweeters - An Investigation of two PRT types as replacements - Mods, Tweaks, and Upgrades to the Classics - The Classic Speaker Pages Discussion Forums
I have also done some experimenting with AR4x's. Visit here for details on my work with phenolic ring tweeter replacements and xover mods that include a post showing similarities in performance outcome very similar to speaker Dave's.
AR4x tweeters - An Investigation of two PRT types as replacements - Mods, Tweaks, and Upgrades to the Classics - The Classic Speaker Pages Discussion Forums
There's a lot of life in first order crossovers, Carl, especially with commercial speakers. I looked up the details of the B&W 685, and surprise, it's just a 1.35mH coil on the 6" Kevlar bass and 4.7uF on the metal tweeter. 🙂
Cone tweeters get very little interest here, but those of us who have tried them like them. They also seem to tolerate a lower crossover than most types down to including the Fs peak in the overall response.
I've not tried all the options with the WLM La Scala Visaton W200S and TW70 drivers yet, but first order tweeter seems to model very badly unless you take the crossover very low to around 1.5kHz with a Zobel on the bass. I must order some biggish tweeter coils around 0.5mH and see what I can try next.
Your higher order filter on a cone tweeter makes a lot of sense to me. They really seem to need that.
Cone tweeters get very little interest here, but those of us who have tried them like them. They also seem to tolerate a lower crossover than most types down to including the Fs peak in the overall response.
I've not tried all the options with the WLM La Scala Visaton W200S and TW70 drivers yet, but first order tweeter seems to model very badly unless you take the crossover very low to around 1.5kHz with a Zobel on the bass. I must order some biggish tweeter coils around 0.5mH and see what I can try next.
Your higher order filter on a cone tweeter makes a lot of sense to me. They really seem to need that.
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Now that we've hi jacked this thread pretty good, you may have seen this already....
6moons audio reviews: WLM La Scala
BTW, I've sold may xover kits for OLA and NLA speakers but have not tinkered with a xover mod. What I did do was build the Pete Basel baffle step compensator module. It takes down the upper MR to HF response and levels it with the bass response with great effect.
BSC vs Shelving - Advent - The Classic Speaker Pages Discussion Forums
6moons audio reviews: WLM La Scala
BTW, I've sold may xover kits for OLA and NLA speakers but have not tinkered with a xover mod. What I did do was build the Pete Basel baffle step compensator module. It takes down the upper MR to HF response and levels it with the bass response with great effect.
BSC vs Shelving - Advent - The Classic Speaker Pages Discussion Forums
Glad you're on board Speakerdoctor. This topic needs a New Englander to balance our Old Englander. So Steve the ringing I speak of is not that of an amplifier or an antenna, or the combination thereof such as an amplifier/loudspeaker connected by some length of wire; it's that of a bell. The ordinary steel speaker basket usually has a flat area to which the motor is attached. Your picture of the AR 4x drivers has one with a larger motor than any of my examples; it couples the top plate to the angled legs of the frame leaving little or no room for undamped flexing to occur. The Large Advent has a flat area between the break of the angled supporting legs of the frame, the rafters to a carpenter, and the motor assembly itself. It flexes to its own resonant frequency, generating what I referred to as hash earlier. Once fixed with epoxy putty and duct seal, there remains some noise from the tweeter but not as smeary (say) as before treatment. Not a lot of options for altering the tweeter.
Hi guys,
Whether the crossover mods that I did for the AR4x are suitable depends a lot on driver phasing. With the AR it required a lot of phase bending to get both reasonable individual responses and a good phase overlap. I was also trying to create a tutorial on general network design.
Someone will need to measure phase and response of the individual sections of an Advent to see if big potential improvements exist. My impression is that Henry Kloss worked harder at driver blending, while AR was of the "get the power response okay" school. This may mean that potential improvements are less.
Last time I measured Advents the response through crossover was decent, but that tweeter had real problems above 10k. I would be playing with phase plugs or rings (occluding rings) to see if response in the top Octave could be improved.
If someone in New England wants to lend me a pair....
Whether the crossover mods that I did for the AR4x are suitable depends a lot on driver phasing. With the AR it required a lot of phase bending to get both reasonable individual responses and a good phase overlap. I was also trying to create a tutorial on general network design.
Someone will need to measure phase and response of the individual sections of an Advent to see if big potential improvements exist. My impression is that Henry Kloss worked harder at driver blending, while AR was of the "get the power response okay" school. This may mean that potential improvements are less.
Last time I measured Advents the response through crossover was decent, but that tweeter had real problems above 10k. I would be playing with phase plugs or rings (occluding rings) to see if response in the top Octave could be improved.
If someone in New England wants to lend me a pair....
Dave: I have one NLA available. PM me for details.
With regard to the OLA, P. Basel recognized the OLA as needing BSC and designed a line stage module that, with selective parts choices, one could pad down much of the high end, thus yielding an overall flatter response that included the LF. I suppose something could be done with the OLA passive xo to accomplish the same. Perhaps a larger series coil on the woofer for starters?
You have an avid basket dampening supporter over at AK.org. You'll need to register to view the thread.
Dampen your driver frames.... - AudioKarma.org Home Audio Stereo Discussion Forums
I do take this basket damping problem seriously. It gets even worse on a very rigid baffle due to the energy involved and lack of absorption IMO.
But you may have solved the rattling and ringing issue for me indirectly here. I think I need to do a really good rubbery gasket around the cutout and perhaps not overtighten the bolts. Baskets don't ring much when sat on a rubber gasket. Dave Smith will be familiar with this from KEF days where they decoupled bass units on rubber.
I'm going to rebuild my workpiece with a modified Advent-type crossover over the next couple of days which also decouples the voicecoils a bit from the magnet with a higher source impedance. This is an 8 ohm crossover of course. We'll see how this goes. 😎
Dug up a few Advent pictures here too. Lots of Masonite in evidence...LOL
But you may have solved the rattling and ringing issue for me indirectly here. I think I need to do a really good rubbery gasket around the cutout and perhaps not overtighten the bolts. Baskets don't ring much when sat on a rubber gasket. Dave Smith will be familiar with this from KEF days where they decoupled bass units on rubber.
I'm going to rebuild my workpiece with a modified Advent-type crossover over the next couple of days which also decouples the voicecoils a bit from the magnet with a higher source impedance. This is an 8 ohm crossover of course. We'll see how this goes. 😎
Dug up a few Advent pictures here too. Lots of Masonite in evidence...LOL
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OK I admit it I'm an AK lurker. I prefer DIY because my dad convinced me that I won't get better (at tennis say) unless I practice against better players. So I don't hang around over there much, what with the high praise for warm sounding 70s transistor receivers and so on. They remind me of me. So as for the basket damping, or dampening where water borne duct seal is utilized: the Advent basket needs more than damping to cure its structural deficiency. Granted, ample damping suppresses most of the problem, but it isn't that hard to correct the basic flaw.
Now you're going to want pix.
Now you're going to want pix.
Very enjoyable days work on gaskets, since it seems good to damp the baskets a bit. 🙂
I built a thick cardboard one for the woofers and a rubbery one for the tweeters. The tweeter really benefited and I've kept it. But I didn't find the woofer did, so I ditched that.
I also did some AB testing between my simple 3.5kHz filter and the complex one. The complex one was more detailed and energetic, but really, there is nothing not to like about the simple one. So I'm using the simple one now! 😎
I also tried a 7kHz tank of 22R and 0.33uF across the woofer BSC coil to reduce cone breakup or hash. More detailed sound, but overall I didn't like it.
So really, I'm thinking you Advent fans should fit a second order tweeter filter and leave it at that. Quite where the crossover point should be depends on how the woofer rolls off, but I'd be thinking about 3kHz, so that might be 8uF and 0.15mH for 4 ohms and some input resistance at least.
I built a thick cardboard one for the woofers and a rubbery one for the tweeters. The tweeter really benefited and I've kept it. But I didn't find the woofer did, so I ditched that.
I also did some AB testing between my simple 3.5kHz filter and the complex one. The complex one was more detailed and energetic, but really, there is nothing not to like about the simple one. So I'm using the simple one now! 😎
I also tried a 7kHz tank of 22R and 0.33uF across the woofer BSC coil to reduce cone breakup or hash. More detailed sound, but overall I didn't like it.
So really, I'm thinking you Advent fans should fit a second order tweeter filter and leave it at that. Quite where the crossover point should be depends on how the woofer rolls off, but I'd be thinking about 3kHz, so that might be 8uF and 0.15mH for 4 ohms and some input resistance at least.
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Advent did a second order on the tweeter but maybe too low to keep resonance noise out the response. I'll try moving the x-o up a bit since my cone and basket mods are extending the woofer's range, right? 'Cause I want it that way, right??
OK I'm ready to move on. I got wave guides to play with and they won't fit the fried egg. On to another 10" two way, Boston A 100. Into the 1980s people!
OK I'm ready to move on. I got wave guides to play with and they won't fit the fried egg. On to another 10" two way, Boston A 100. Into the 1980s people!
I checked the caps on mine it's says 8uf and 16uf. Id read that this speaker is REV. 1 crossover.
16/8/3 was the last of 3 xover iterations and probably the one Kloss settled on for best sound.
Rev. 1, IIRC, had 16/16/4.
Rev. 1, IIRC, had 16/16/4.
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