Well, its based on listening experiments...
From the latest comments in this thread, it seems there are good reasons for series wiring not being the best solution.
Bruno: Thanks you for your comments, dead honest and trustworthy as always.
My XO frequency for the woofers is 200 Hz. Do you still think UcD400's will sound as good as NC400 ?
I will of course get a pair of NC400 for my main speakers.
My guess would be that 200Hz is still fine. I'm basing myself on the observation that 200Hz is roughly where the ear starts having trouble differentiating between direct and reflected or reverberant sound. It stands to reason that differences between amps, which are much more subtle, should fly below the radar as well.
Well... I'm not sure. I did hear a significant improvement is sound quality when I changed my woofer amps from ICEpower 1000ASP's to UcD400HG's. Level matched within 0.1 dB of course.
I have a very "direct" woofer sound since I use dipoles placed about 1.5 meter from my listening position, and a very well treated listening room with short decay even in the bass region.
I have a very "direct" woofer sound since I use dipoles placed about 1.5 meter from my listening position, and a very well treated listening room with short decay even in the bass region.
Well yes I found similar comments by the aforementioned industrial customer a bit puzzling. It's wonderful when people love the stuff I make but I also like to understand what's going on. OTOH the difference between the 1000ASP and UcD is a bit larger than the difference between UcD and Ncore. And there are secondary effects to keep in mind, like conducted emissions emanating from the PSU or existing mains noise injected into the secondary ground through the mains filter. It's quite possible you're hearing a difference in the mid/high section because of PSU related currents racing through the signal wiring.
Last edited:
Hm. Some day I'll get to the bottom of this. But anyhow, considering that the 1000ASP is a different animal compared to either UcD or Ncore I personally still think I'd feel quite safe just adding UcD's. In the end you'll have to make the call yourself of course.
I'm currently working on a sub to go with the LS1's. The cutoff frequency is only 80Hz and the amp is a UcD400ST but I'll do the experiment with a pair of Ncores as well and report back (won't be this month yet though, too busy).
I'm currently working on a sub to go with the LS1's. The cutoff frequency is only 80Hz and the amp is a UcD400ST but I'll do the experiment with a pair of Ncores as well and report back (won't be this month yet though, too busy).
Hello,
the acoustical load of a woofer is usually very small, especially of a "lonely" dipole, except for stacking of _a lot_ woofers (e.g. so called URPS). Therefore I would not be afraid of subharmonics, at least not because of series connection.
Some time ago I tried the UcD180 to drive 1 Ohm (resistive), to test the overcurrent shutdown. That worked in principle, but after some playing the output cap exploded. We had some Email communication with Hypex and Bruno, but the phenomenon haven't been cleared fully. At least I did not understand this effect, because Bruno explained the low cap current even in overload conditions.
Hypex changed the module, their service is great. The load conditions were outside the spec, so no problem at all, but I would not suggest load impedances below the spec (2 Ohms).
Thank you Bruno for your great work!
Cheers, Timo
the acoustical load of a woofer is usually very small, especially of a "lonely" dipole, except for stacking of _a lot_ woofers (e.g. so called URPS). Therefore I would not be afraid of subharmonics, at least not because of series connection.
Some time ago I tried the UcD180 to drive 1 Ohm (resistive), to test the overcurrent shutdown. That worked in principle, but after some playing the output cap exploded. We had some Email communication with Hypex and Bruno, but the phenomenon haven't been cleared fully. At least I did not understand this effect, because Bruno explained the low cap current even in overload conditions.
Hypex changed the module, their service is great. The load conditions were outside the spec, so no problem at all, but I would not suggest load impedances below the spec (2 Ohms).
Thank you Bruno for your great work!
Cheers, Timo
Wim, yes the same amp should only be able to deliver 1/4th the power in 16ohm compared to 4ohm, but you also get double efficiency with the two woofer serial connection as only half the current is used twice hence giving the same output as if only a single woofer was used. Also only 1/4the the power is dissipated in each driver for the same output as a single driver when two are used in series giving less heat-related compression.
Bruno, I also find 200Hz to be the crucial point when crossing between mids and woofers to avoid making the woofer maks the midrange clarity. If the woofer outputs too much above 200hz the mids suffer audibly. Regarding amps they may have much less distortion than speaker drivers, but somehow my feeling is that two amps although both featuring very low distorion do sound differently. And in many cases not my a small margin. There sure seems to be more in it than low distorion figures. My ICEPOWER and UCD sure plays bass VERY differently -also at low listening levels.
StigErik,
I haven´t done series connection in bass applications, but some commercial speakers do and still gets rave reviews. This is of course no proof, but raidho employs a combination of serial and parallel connection in their 4 woofer designs. I heard one once, and it wasn´t to my taste, but that was probably down to the implementation. When i have used serial connections with midranges the result was very good though.
In my perspective, connection two drivers in series, shouldn´t be equivalent to using one driver with a serial connected resistor, but rather to serial connect two coils, hence doubling the electrial parameters both inductive and resistive. As both coils deliver motion and acoustic output this is could just as well be equivalent to using a driver with twice the cone area and twice the electrical parameters, unless one driver is preventet to move. But normal single drivers also reacts to the acoustic load regarding their impedance and output.
cheers,
Bruno, I also find 200Hz to be the crucial point when crossing between mids and woofers to avoid making the woofer maks the midrange clarity. If the woofer outputs too much above 200hz the mids suffer audibly. Regarding amps they may have much less distortion than speaker drivers, but somehow my feeling is that two amps although both featuring very low distorion do sound differently. And in many cases not my a small margin. There sure seems to be more in it than low distorion figures. My ICEPOWER and UCD sure plays bass VERY differently -also at low listening levels.
StigErik,
I haven´t done series connection in bass applications, but some commercial speakers do and still gets rave reviews. This is of course no proof, but raidho employs a combination of serial and parallel connection in their 4 woofer designs. I heard one once, and it wasn´t to my taste, but that was probably down to the implementation. When i have used serial connections with midranges the result was very good though.
In my perspective, connection two drivers in series, shouldn´t be equivalent to using one driver with a serial connected resistor, but rather to serial connect two coils, hence doubling the electrial parameters both inductive and resistive. As both coils deliver motion and acoustic output this is could just as well be equivalent to using a driver with twice the cone area and twice the electrical parameters, unless one driver is preventet to move. But normal single drivers also reacts to the acoustic load regarding their impedance and output.
cheers,
No qualms about that. Perhaps we could restate the question in less absolute terms. Suppose we're comparing two amps in an active speaker, wouldn't it be reasonable to expect the difference to be a lot smaller if we changed only the woofer amps compared to, say, the MF and HF amps? I would think so. On top of that, the difference between UcD and Ncore, though large to my ears, is not that big compared to the difference between Ice and UcD.
Totally agreem Bruno. If one is to go the extra length, the top is where to start -from a quality perspective. Low end might win more from a quantity approach.
What is always so difficult to extract from these things is that our hearing doesn´t discriminate like instruments do. In my experience the "midrange" is often much more audibly affected by the quality of the "extreemes" on either end than what we usually expect it to be. In hearing and listening we are talking in relative terms as quality improvement in the extreemes often yeld great benefits in what we percieve as the "midrange". This speaks for that improvements in one region (like below 200Hz) can bring audible benfits which are experienced to come from a band outside that which is improved, and thus seems to bring greater improvements than expected.
StigErik,
When I did the tests, I played around with the PS for the UCD to get the most from it. What I did get from the comparisons (UCD100 vs ICE500 both on linear PS´s with around 400-500VA coils) was that the UCD has a meatier (and more "together") bass where the ICE seems leaner. The ICE did seem more extended where the UCD could be made to have better grip. These experiences ware heavily dependent on the way I did the PS for the UCD´s and i used the ICE as a reference for comparison with no alterations, so are thus no really usefull for generalizations.
cheers,
I reached the same conclusion independently quite some time ago, though it depends somewhat on what one defines to be back EMF. In most cases the return loss of the speaker enclosure is well above the drivers' underlying nonlinearity. Strictly speaking the resulting back wave reflection to the cones/domes/whatever is microphonic and not a back EMF in the traditional use of the term in physics. But from the amplifier's standpoint it's all just an error for the feedback loop to sense and suppress. The Spice modeling I've done suggests the quality of the error correction is primarily a function of passive crossover component selection---the sims tend to agree with subjective observations ESR matters for transient response as well as level control---with amplifier output impedance and cable selection being more like second and third order effects, respectively.
Hi, we were comparing 2 parallel woofers versus 2 series woofers. So I still would say that when the amp delivers 4 times more power, this will also be produced by the speakers. The only reason the efficiency of the speakers goes up, is because the cone area is doubled, but this is the case for both parallel and series woofers. So I still would think that the parallel configuration would have 6db more of acoustic output, hence more headroom...
Juhleren,
It's pretty much the same as my experience. I compared ICE 1000ASP with UcD400HG / SMPS400. The UcD had "meatier", fuller bass with more tone, and even so better control, dynamics and attack. I did not notice any difference in extension, both amps played 20 Hz with no lack of quality compared to the rest of the frequency range.
It's pretty much the same as my experience. I compared ICE 1000ASP with UcD400HG / SMPS400. The UcD had "meatier", fuller bass with more tone, and even so better control, dynamics and attack. I did not notice any difference in extension, both amps played 20 Hz with no lack of quality compared to the rest of the frequency range.
Hmm... having built my first icepower 125asx2 diy kit, this is relevant to my interests. Would you say that icepower is the poor man's hypex?
@twest I would indeed consider the effects you're listing part of back EMF. The degree to which they are significant is easiest seen from an impedance plot. What I had in mind though was nonlinear distortion (harmonic distortion etc), because a lot of it lands inside the bandwidth of the other units in a passive multiway system if there is a significant common impedance between the crossovers (like cable resistance or amplifier output impedance).
@banglacx I thought the ST modules were the poor man's Hypex?
@banglacx I thought the ST modules were the poor man's Hypex?
Maybe... but you cant compare the two really. ICEpower is not generally available for DIY (apart from rogue modules sold on ebay), and Hypex is. Yes, Hypex is more expensive. It has to be since they have great support and sell single modules for DIY. With ICEpower there is no support at all for DIY, and you simply cant buy single modules from B&O ICEpower.
The ICE 125ASX2 is a very good module I think, but not quite up to the level of Hypex sonically. The ASX2 series is in my opinion the best ICE modules for midrange and treble, while the old ASP modules do offer slightly better bass.
@banglacx I thought the ST modules were the poor man's Hypex?
If you look around, complete kits, including casing, connectors and cables can be had for $210 utilizing the 125ASX2, shipped. And it does sound pretty good! Putting the ST module together would have been more expensive.
I'm hoping that someday Bruno would release something like "Ncore-Frugal" editions. All the goodness of Ncore, reasonably priced, about 50 watt per channel. Perhaps a different distribution chain, in small quantities for DIY only. If the Ncore lives up to the expectation, then the hypothetical "Ncore-frugal" has the possibility to gain clear leadership in market share for class-D amps.
It's funny to see split personalities of customers when it comes to amps. When Nelson Pass says "25 watts is enough, or you're doing it wrong", everyone politely agrees. And then they demand 500 watts of a class-D design, "just in case". I've seen this before - people requesting 200 WPC class AB design amps to listen at 9 O'clock position almost all the time. The usual suspect is this.
I hope the technology trickles down to low-powered, value priced DIY kits. Bruno, I appreciate all you've done for the DIY community.
- Status
- Not open for further replies.