Done that too.
You guys will have to wait... my hands are full at the moment. Good things happen to those who wait.
I have simulated the response based on Joe's raw driver
measurements and with mine impedance approximations along
with the modified Joe's XO filter and I am positive that the summed
response is nowhere near as benign as being presented here.
Increasing the XO frequency together with lowering the electrical
filter order is a recipe for troublesome vertical off-axis behavior.
The whole idea here was not to improve the loudspeaker SQ,
but to support the idea of using amp designs different than the
usual ones.
measurements and with mine impedance approximations along
with the modified Joe's XO filter and I am positive that the summed
response is nowhere near as benign as being presented here.
Increasing the XO frequency together with lowering the electrical
filter order is a recipe for troublesome vertical off-axis behavior.
The whole idea here was not to improve the loudspeaker SQ,
but to support the idea of using amp designs different than the
usual ones.
The quoted paragraphs pretty much clearly state that my conclusions
are sound, including the marketing thing.
That you persist on stating that loudspeaker XO filters are somehow
flawed( "noise") is a bit too much. That's brainwashing.
Your whole approach to this matter is very similar to what cable
manufacturers claim about their products.
Joe, I'm sure your speaker sounds very nice. And I know you are a decent fellow. But all this is nonsense. You have a very simple crossover. An series inductor on the woofer, a series cap, an LC shunt and a series resistor on the tweeter. All the other elements are nothing more that impedance compensation. Their only function is to make the voltage applied at the input of the crossover less sensitive to amplifier output Z. They do not make it constant current. They make the speaker look like constant Z to the amp. As for what the drivers see, the following plots show the voltage at the input node of the crossover with and without the Z comp elements. The first picture show you circuit and the point at which I consider the input to the crossover.
As far as current sourcing, any time you place a large series resistor, Rs, between a voltage source, Vs, and a network with characteristic impedance Zc, it starts to look like a current source as the current is Is = Vs/(Rs +Zc) and as Rs becomes much larger than Zc this goes to Is = Vs/Rs and since Rs is constant then Is will tend to be constant. Of course, that is the current delivered to the speaker. It is not the current that reaches the driver as much of the current is drawn off through the compensation networks. I.E. a lot of power is dissipated (wasted) in the comp networks. Better to use an amplifier designed to drive a load with frequency varying Z. But it's very audiophile to make excuses for poorly designed amps and blame it on the speaker's Z characteristics.
More important is what the impedance comp networks do to damping. To see that you have to look at the impedance the driver sees when the driver is considered as the generator. The plots below show the "look back" Z the woofer sees and the "look back" Z the tweeter sees with the impedance comp networks in place for amps with 0.01 output Z and 270 ohm output Z. Note that high impedance means little electrical damping.
Sorry to pick on you Joe, but most of the stuff you are saying is basically audiophile gobblly gook.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
As far as current sourcing, any time you place a large series resistor, Rs, between a voltage source, Vs, and a network with characteristic impedance Zc, it starts to look like a current source as the current is Is = Vs/(Rs +Zc) and as Rs becomes much larger than Zc this goes to Is = Vs/Rs and since Rs is constant then Is will tend to be constant. Of course, that is the current delivered to the speaker. It is not the current that reaches the driver as much of the current is drawn off through the compensation networks. I.E. a lot of power is dissipated (wasted) in the comp networks. Better to use an amplifier designed to drive a load with frequency varying Z. But it's very audiophile to make excuses for poorly designed amps and blame it on the speaker's Z characteristics.
More important is what the impedance comp networks do to damping. To see that you have to look at the impedance the driver sees when the driver is considered as the generator. The plots below show the "look back" Z the woofer sees and the "look back" Z the tweeter sees with the impedance comp networks in place for amps with 0.01 output Z and 270 ohm output Z. Note that high impedance means little electrical damping.
An externally hosted image should be here but it was not working when we last tested it.
Sorry to pick on you Joe, but most of the stuff you are saying is basically audiophile gobblly gook.
Last edited:
I have only had 4 1/2 hours of sleep and gotta work, so I will be brief. The last few posts mean that this thread is about to close down, at least discussion wise. The tone is now obvious. Very condescending.
The "nothing new here" line and that Croat now saying this is a marketing exercise (how it can be interpreted that way completely beyond me) means that will be the case. The 'usual suspects' have turned up.
Could you at least explain this:
If you can, I would be indebted to you. It has stumped a couple of very competent speaker designers (I can't mention their names because I don't want to drag them into these murky waters).
If you don't understand the graph and what is behind it, then it it's because you did not read the earlier posts.
I suspect you have come in at a tangent to the discussion and quickly summed up - and hence seen reason to teach me kindergarden stuff (sigh), but tell me please, what is happening in that graph, never mind the tiresome "nothing new stuff" line (yes, there is a good reason why there is a single inductor and you never even had the courtesy to ask why - and I just want to tell you there is a particular reason I chose that).
I am very tired, people who have the Usher S520 now have an option that is reversible, they can build the crossover and decide for themselves and keep it if they want. There are so many of these little buggers out there, that was the attraction. My motives are pure, I sleep well. I like the idea of DIY and I am not by nature a commercial beast - although the 'usual suspects' have locked in that conclusion.
So, unless the tone changes, any questions asked will have to be answered via PM, and that is truly sad as free discussion is becoming an increasing premium.
BTW, I would have liked to have had a discussion about the nature of motional and inductive and microphonic EMF and how to deal with them. Now seems unlikely.
Na0?
BTW, always liked dipole speakers, built my first pair in 1975.
41 years ago... scary.
Yep, been doing them stuff for that long. I even remember my discussion with Richard Small in that same year, re using the very non-orthodox use of adding series resistors to woofers that were to heavily over-damped so that they could be used in larger enclosures and get lower Fb or Fc. His idea, not mine. That would be heresy these days and I pointed out to him that it was even heresy then. But he was of course right - damping factor was nonsense to him and all that mattered was the final alignment - later a commercial loudspeaker designer/manufacturer made a subwoofer and confided that he used a 2.2 Ohm series resistor to get the Qc = 0.6 but didn't tell anybody.
Sorry for the name dropping, but I have been around and I won't be lectured to as if I was a novice.
BTW, always liked dipole speakers, built my first pair in 1975.
41 years ago... scary.
Yep, been doing them stuff for that long. I even remember my discussion with Richard Small in that same year, re using the very non-orthodox use of adding series resistors to woofers that were to heavily over-damped so that they could be used in larger enclosures and get lower Fb or Fc. His idea, not mine. That would be heresy these days and I pointed out to him that it was even heresy then. But he was of course right - damping factor was nonsense to him and all that mattered was the final alignment - later a commercial loudspeaker designer/manufacturer made a subwoofer and confided that he used a 2.2 Ohm series resistor to get the Qc = 0.6 but didn't tell anybody.
Sorry for the name dropping, but I have been around and I won't be lectured to as if I was a novice.
I don`t understand what is the problem?
Do you people really think Joe started this thread, rediscovering wheel, to earn money??
Yes it is seen before, but Joe is again raised this question and I think it is interesting to think about and comment without claiming it`s a marketing thing ...
I think that crossover "noise" it`s just a lack of adequate word. I also didn`t understand that part of the story, but let the mean speak, so you could comment later....
Do you people really think Joe started this thread, rediscovering wheel, to earn money??
Yes it is seen before, but Joe is again raised this question and I think it is interesting to think about and comment without claiming it`s a marketing thing ...
I think that crossover "noise" it`s just a lack of adequate word. I also didn`t understand that part of the story, but let the mean speak, so you could comment later....
Which is something i have seen Joe say here a number of times.
From the FR graphs, except for a small extension in the bass with a current amp, this XO/filter allows one to ignore the amplifier output impedance (ie damping).
If it doesn't involve computers, there is vanishing little that hasn't been explored by those that came before us. This is an idea that deserves reexploring.
What Joe has presented is a ready to implement design for a commonly available speaker that allows diyers to explore a whole class of amplifiers that have been for some time relegated to the locker room. And see what effect it has on more commonly available amps.
And many will take the ideas and apply them to their loudspeaker. Results will speak for themselves.
Personally i'm not a fan of cone + dome speakers, or passive components between an amp & a speaker (after all "XOs are evil" Geddes) perferring to try to sort the problem at its root.
Joe has been exploring this concept for sometime… the 1st i saw was Visaton B200 loaded in an aperiodic TL (dramatically reducing the bass humps), and a tweeter (of questionable need once the driver has been properly modified). Then a revision of the Elsinore. All the way with lots of others involved.
dave
PS: John, what is the output impedance of the "amp" in your sims.
What marketing? This is a give away...
XOs are flawed. As i quoted in my previous post "XOs are evil" Geddes. They are usually the weakest part of a speaker. We can only work to minimize their issues.
dave
I haven`t seen a bare cone driver without impedance peak, so I guess, for this exact issue, no one sorted the problem at it`s root or there is a flat impedance driver?
Yes, it is a problem. Given the assumption that amps have low ouput impedance, speakers are almost all universally designed for such amps and little care is given to mechanical damping. There are drivers with modest Qms (i have seen 1.4 to 2.0), that with careful enclosure design can reduce the size of the impedance bump at the bottom (aperiodic enclosures, a TL is often a good starting point). and if designed specifically for a current amp, a bump at the bottom can be used to extend the LF response. As an example, here the raw inpedance and the impedance in midTL of the FF85k.
This is actually for use as a midTweeter, but also brings out the situation where one biamps with a voltage amp on the bottom and a current amp on the top.
Playing with a variable output impedance amp also showed that, at least with a FR, the rise in impedance at the top & bottom could be used to dial in a more extended frequency response.
Historically there have been drivers with Qm less than 1, back in the day when amplifier output impedance was generally higher than today. Until i chatted with an old WE engineer still building amps and him saying "Why would anyone build an amp without an output impedance the same as the speaker?" was what started my journey out of the "low output impedance is important" camp.
Many claims have been made for current amps, the community deserves a chance to confirm or not whether these hold water.
dave
Bingo!
But what makes them the weakest part and why we can only ever compromise, that is the real discussion we ought to have here and not get shot down in flames. Having that discussion would also see the reason for the 'noise' comment and why it is a troublesome word to use.
Why does John Kreskovsky like open baffles? I believe it has to do with microphone type EMF that modifies the driver's impedance dynamically - that the only perfect VC is one that has a DCR flat from DC (hence DCR) to infinity. Any increase that deviates from DCR are produced by EMFs of different kinds... and while these are significant, the effects of EMF(s) is further exacerbated by the crossover. Studying how to suppress EMF(s) and you realise just how big a problem the crossover is and that you will never have the perfect answer. I asked Brad Serhan (sorry, but it seems I have to resort to name-dropping, not to brag, but to show credentials) once whether he had ever done a speaker system with a series crossover. He said only once and it was tricky for him, but admitted that it sounded very "sweet." I told him I believed I knew why it did.
Esa Merilainen has written about these things in his book, but it is not an easy read (sorry Esa, but it is clumsily written and I wish I could have a hand in proof-reading) and hence there has been a need to have this discussion. The crossover I have developed deals with these things and tries to get the crossover out of the way as much as possible. It is not perfect.
Take that single series inductor that John so clearly focused on, to have the compensation before the inductor and seen directly by the amplifier's terminals, was a very deliberate choice in not correcting the inductance right across the speaker's terminals. That is a challenge to do, but it means that the high-pass to the tweeter needs very careful attention - and of course you need a bit of luck to make it work - I am reasonably pleased with the result in the Usher.
So why not use a Zobel on the MidBass? Why not flatten the Z?
Maybe we can all agree with this basic fact, with or without crossover, that with voltage drive we (the driver actually) have to convert V to I and add to that EMF(s), and now the addition of crossovers and you have opened the door for interference patterns... noise? The best way to suppress those potential interference? What the VC sees when looking back and the suppression of unwanted interference is as high impedance as we can muster. Hence Zobel that flattens the Z on the VC has a cost.
BTW, when discussing EMF, the F stands for potential, voltage. The irony, as I see it, is that a low impedance speaker is a current device, yet also can be seen as a voltage source going in the opposite direction?
That is that the peak Z at Fs is caused my motional EMF and that the rise in Z above 200Hz is related to inductive EMF, so hence that upwards deviation is actually caused by voltage.
Voltage generation changing the impedance dynamically? That is what It looks like to me - if Esa turns up here I wonder if he would agree with that summation.
And top of that, any other mechanical forces, resonance in both cones and enclosures (open baffle anyone?) and other microphonics creates additional voltages that interfere with V/I conversion. And at he heart of all this: The crossover, the weakest link of all.
Yeah, Geddes was right - a quote I have not seen, but I trust he said it as you quoted him.
Cheers, Joe
PS: Just got some terrific news this morning. The largest selling Australian Album of 2015 has been nominated for eight Tamworth Awards - it was recorded on my six-channel tube front-end (affectionately known as "The Tube Station") custom made for the producer Garth Porter - a legendary name in Australian music. Made my day and makes the point that I am not the infantile novice that some think I am.
Last edited:
Garth Porter: Not the man who wrote 'howzat'?
Rancom St. Studios Sydney - Equipment but you do indeed get a mention under microphone preamps.
Rancom St. Studios Sydney - Equipment but you do indeed get a mention under microphone preamps.
- Status
- Not open for further replies.