These pictures of clipping in a bi-amped system clearly illustrate another advantage of bi-amping that hasn't been touched on yet in this thread.
dave
dave
walker - i'm with you completely on this. active xovers + amps are undoubtedly the way to go for high quality sound on a low-ish budget. my current project is a pair of studio monitors for which i've built active xovers + 4 50W amps + enclosures + PSU for less than £100. the difficulty in going active is that the amount of effort involved goes up quite a lot. also, the attention to and understanding of details gets important - grounding becomes a BIG issue.
i'm hoping to get the electronics finished this week - the cabinets are nearly done, just waiting on a tweeter to be delivered (over 4 weeks after Wilmslow Audio sent the rest of the bits - not happy....). the initial tests have delivered a sound quality way beyond what i expected for less than £300 total parts, and there's only couple of things left to sort out now. i'll let you know how i get on when they're done 'cos i've learnt a lot of lessons during this project.....
i'm hoping to get the electronics finished this week - the cabinets are nearly done, just waiting on a tweeter to be delivered (over 4 weeks after Wilmslow Audio sent the rest of the bits - not happy....). the initial tests have delivered a sound quality way beyond what i expected for less than £300 total parts, and there's only couple of things left to sort out now. i'll let you know how i get on when they're done 'cos i've learnt a lot of lessons during this project.....
On first and higher order cross-overs
A comment was made early about using first or higher order cross-overs with the first order cross-over presenting the lowest impedance between the amp and speakers. While this comment will not be true for 3rd and higher order cross-overs, a second order cross-over does not increase the impedance between the amp and the driver compared to a second order cross-over, though the second order cross-over will present a higher overall load to the amplifier. I am using what is essentially a first order filter with an RLC notch filter across the bass-driver to give a third order filter response for the crossover frequency. This gives the driver the same view of the amp as a first order in terms of impedance, though it definately creates more load, though not excessively.
That all being said and done, I am all for passive pre-amp or active cross-overs and an amp per speaker, though like others out here, I think it will be tough to repeatable meet the cost target set out by the link starter. I guess the ultimate if you are listening to purely digital sources, would be to do all the filtering in the digital domain. For that, you can go to one of my threads currently running on DAC concept.
A comment was made early about using first or higher order cross-overs with the first order cross-over presenting the lowest impedance between the amp and speakers. While this comment will not be true for 3rd and higher order cross-overs, a second order cross-over does not increase the impedance between the amp and the driver compared to a second order cross-over, though the second order cross-over will present a higher overall load to the amplifier. I am using what is essentially a first order filter with an RLC notch filter across the bass-driver to give a third order filter response for the crossover frequency. This gives the driver the same view of the amp as a first order in terms of impedance, though it definately creates more load, though not excessively.
That all being said and done, I am all for passive pre-amp or active cross-overs and an amp per speaker, though like others out here, I think it will be tough to repeatable meet the cost target set out by the link starter. I guess the ultimate if you are listening to purely digital sources, would be to do all the filtering in the digital domain. For that, you can go to one of my threads currently running on DAC concept.
Hi walker
I am inclined to generally agree with the theory you have proposed, especially after reading the ESP site, however, two possible hold ups spring to mind:
1. Naim users, on their forum seem to universally advocate the use of a better amp when upgrading, rather than going active with a cheaper one.
2. The Linkwitz site has a section on driver selection which covers a lot more criteria than better amp control alone can improve.
If it’s any consolation, ATC use relatively cheap amps in their expensive driver active speakers. I’ve been pondering active drive myself for a long time. There is a lot of positive info about going active on the web, but most of it from people who will not reference it to a benchmark I am familiar with. At least I know what ballpark the mostly negative Naim users are in. I feel I really need to hear active drive for myself. I am currently building some ESP p3a’s for trail and experimentation with a Volt BM220 bass unit in a Wilmslow Audio Home Studio Monitor kit speaker. Will post results when/if I have something, which I feel, will be of any use/interest, but don’t hold you breath!
Mark
I am inclined to generally agree with the theory you have proposed, especially after reading the ESP site, however, two possible hold ups spring to mind:
1. Naim users, on their forum seem to universally advocate the use of a better amp when upgrading, rather than going active with a cheaper one.
2. The Linkwitz site has a section on driver selection which covers a lot more criteria than better amp control alone can improve.
If it’s any consolation, ATC use relatively cheap amps in their expensive driver active speakers. I’ve been pondering active drive myself for a long time. There is a lot of positive info about going active on the web, but most of it from people who will not reference it to a benchmark I am familiar with. At least I know what ballpark the mostly negative Naim users are in. I feel I really need to hear active drive for myself. I am currently building some ESP p3a’s for trail and experimentation with a Volt BM220 bass unit in a Wilmslow Audio Home Studio Monitor kit speaker. Will post results when/if I have something, which I feel, will be of any use/interest, but don’t hold you breath!
Mark
Mark25 said:
I'm a NAIM user, and used to be a NAIM dealer, and i wouldn't agree with that sentiment.
Now if one considers that NAIM users tend to stay with NAIM amps and there is a general correlation between quality & price in that lineup there is some validity.
But if one considerd amps outside of NAIM then a cheaper, smaller amp, can be better than the bigger more expensive amp. And by the very nature of bi-amping you can get away with smaller amps. You don't want to sacrifice quality but you can sacrifice cost when looking at amps for bi-amping.
One should also consider that when bi-amping your amp is typically driving a much less reactive load, and even thou it may not be of quite the same quality as the more costly amp when driving the more reactive speaker, it may well be better driving the less reactive driver than the big amp is driving the more reactive speaker system. (ie because you are reducing the complexity and bandwidth requirements, the lesser amp may work better into its load).
dave
Think I`ll have to interrupt here, after all this is about one of my favorite subjects. Passive xo`s are critical, but if they`re done right they (allmost) don`t do any harm.
The first thing to be sure of is that every component involved are capable of handling it`s power without clipping/distortion. No cheap caps or tiny resistors; I`m using 600v Solen for low freq, three of them in parralell (100uf=3x33uf,same sice=same speed). Same way with resistors, 6-10 in parralell for "unlimited" power handling. And off course heavy coils, like 4awg(trafo) for low-end
and 10awg (foil!) for mid. "Forgetting" this makes the speaker screem at high levels and the amps begging for mercy.
Next; avoid shortcutting the amp. Every (single) component placed in paralell between the two signal-halves represents a "relative" shortcut of the amp. Just look at the impedanse-curve and see what happens. That leaves only first-order parralell-filters left, and that again don`t leave many drivers..
Well, one single component in paralell makes the amp "see"(meet) itself in a power-leaking shortcut, but by adding another component (like a resistor) the amp will no longer see itself like before. This opens for using a "semi"-third-order filter if absolutely needed, me I`m avoiding that to keep the signal as clean and dynamic as possible. But first-order with imp.-corr. is a good compromise.
This really makes a big differense, no reason for doubt here. It`s much like tuning up a car; remove anything that blocks the airstream/power. And like with tuning a car-enegine, it`s important to pick only the best parts to reach the ultimate preformance. Really fast and clean-sounding drivers that allows a simple filter is a good start.
Through the years I`ve (re-)discovered a few other tricks too. I`m not using any absorbers in my speakers anymore, but diffractors.(-and asymetric cabinets) Absorbers are "eating" acoustic energy, and even if the amp can compensate for this it will still ruin the dynamics.
Specially the bass-system are suffering from this, but also the mid can be clearly(!) improved by replacing the absorbers with well-made diffractors.
Then finally there`s cables and amps. When it comes to speaker-cables there`s only one thing that does it: heavy solid-core cables. On my transistor-amp I`m using someting like 2,5awg for bass and mid, "a little less" to the top.(tube-amps or smaller drivers don`t need that heavy stuff, but still..) And off course separate cables for each driver. The effect of using separate cables(bi-/tri-wiring aso) are much simular to using several amps if just the amp has "unlimited" power. Even if the current falls in the cable from feeding the bass-driver, this "shaking" will be allmost undetectable on the tweeters connection after running through some feets of cable. (try and see!)
The same thing about amps; it`s not just the sice of the powersupply that makes the control, it`s about the sice of the thread used in the trafo, specially on the secondary side. A big trafo done from tiny thread will not be able to handle great power-dynamics, adding power-caps just covers up the problem and makes the amp "slow"and "fat"-sounding.
Even before the amp there`s something to do; one of my biggest dynamic improvements came from replacing several exotic powercables just with .. solid core. I started up making up cables for a friend and his Jadis power-amps, but when we later on was doing a comparasion between LP and CD I tryed the cables on the CD-combo as well, and what a jaw-dropping shock! Now the effect won`t be that big on a smaller system, but it definitely gives better conditions for the powersupply witch can be heard in improved dynamics and cleaner sound.
And what does all this end up with? "Whow, it sounds like live!"
The first thing to be sure of is that every component involved are capable of handling it`s power without clipping/distortion. No cheap caps or tiny resistors; I`m using 600v Solen for low freq, three of them in parralell (100uf=3x33uf,same sice=same speed). Same way with resistors, 6-10 in parralell for "unlimited" power handling. And off course heavy coils, like 4awg(trafo) for low-end
and 10awg (foil!) for mid. "Forgetting" this makes the speaker screem at high levels and the amps begging for mercy.
Next; avoid shortcutting the amp. Every (single) component placed in paralell between the two signal-halves represents a "relative" shortcut of the amp. Just look at the impedanse-curve and see what happens. That leaves only first-order parralell-filters left, and that again don`t leave many drivers..
Well, one single component in paralell makes the amp "see"(meet) itself in a power-leaking shortcut, but by adding another component (like a resistor) the amp will no longer see itself like before. This opens for using a "semi"-third-order filter if absolutely needed, me I`m avoiding that to keep the signal as clean and dynamic as possible. But first-order with imp.-corr. is a good compromise.
This really makes a big differense, no reason for doubt here. It`s much like tuning up a car; remove anything that blocks the airstream/power. And like with tuning a car-enegine, it`s important to pick only the best parts to reach the ultimate preformance. Really fast and clean-sounding drivers that allows a simple filter is a good start.
Through the years I`ve (re-)discovered a few other tricks too. I`m not using any absorbers in my speakers anymore, but diffractors.(-and asymetric cabinets) Absorbers are "eating" acoustic energy, and even if the amp can compensate for this it will still ruin the dynamics.
Specially the bass-system are suffering from this, but also the mid can be clearly(!) improved by replacing the absorbers with well-made diffractors.
Then finally there`s cables and amps. When it comes to speaker-cables there`s only one thing that does it: heavy solid-core cables. On my transistor-amp I`m using someting like 2,5awg for bass and mid, "a little less" to the top.(tube-amps or smaller drivers don`t need that heavy stuff, but still..) And off course separate cables for each driver. The effect of using separate cables(bi-/tri-wiring aso) are much simular to using several amps if just the amp has "unlimited" power. Even if the current falls in the cable from feeding the bass-driver, this "shaking" will be allmost undetectable on the tweeters connection after running through some feets of cable. (try and see!)
The same thing about amps; it`s not just the sice of the powersupply that makes the control, it`s about the sice of the thread used in the trafo, specially on the secondary side. A big trafo done from tiny thread will not be able to handle great power-dynamics, adding power-caps just covers up the problem and makes the amp "slow"and "fat"-sounding.
Even before the amp there`s something to do; one of my biggest dynamic improvements came from replacing several exotic powercables just with .. solid core. I started up making up cables for a friend and his Jadis power-amps, but when we later on was doing a comparasion between LP and CD I tryed the cables on the CD-combo as well, and what a jaw-dropping shock! Now the effect won`t be that big on a smaller system, but it definitely gives better conditions for the powersupply witch can be heard in improved dynamics and cleaner sound.
And what does all this end up with? "Whow, it sounds like live!"
Going active made the most noticable improvement to my system next to the loudspeakers. Replacing a single amp, which is trying to push the full frequency range through a crossover to multiple different drivers, with smaller amps producing a limited frequency range connected directly to a single driver just makes sense IMO. Why waste the power? I made a MTM active for just under $300 by building 4 X 50 watt amps and 2 active crossovers, which greatly improved dynamics. Also nice to be able to adjust gain and not worry too much about matching driver sensitivity.
Jason
Jason
It's simple and it isn't
I'm sorry that I haven't got the time to answer all the questions raised today, if there is still interest in this issue I'll get back to most of them next week.
The simple point that I'm trying to make is that when it comes to driver quality you reach the point of diminishing returns at fairly low prices. Let's pick a 12" driver, and compare a $50 unit and a $120 unit, you can expect quite a noticeable difference in quality. Now if you compare the $120 driver with an $800 driver, in my experience the difference is much less. Now let’s compare the $120 driver directly connected to the amp, (active xo) and the $800 driver with a passive xo. I have found that the loss of dampening/control usually reduces the quality of the $800 driver to less than that of the $120 direct coupled unit.
Sure you need more amps but at lower power ratings and most would be aware of the many other benefits of bi-amping.
In the end, it is my experience, that it is cheaper to use good quality mid priced drivers directly connected than to pay for exotic, (read ridiculously priced) drivers used with passive xos.
Regards WALKER
I'm sorry that I haven't got the time to answer all the questions raised today, if there is still interest in this issue I'll get back to most of them next week.
The simple point that I'm trying to make is that when it comes to driver quality you reach the point of diminishing returns at fairly low prices. Let's pick a 12" driver, and compare a $50 unit and a $120 unit, you can expect quite a noticeable difference in quality. Now if you compare the $120 driver with an $800 driver, in my experience the difference is much less. Now let’s compare the $120 driver directly connected to the amp, (active xo) and the $800 driver with a passive xo. I have found that the loss of dampening/control usually reduces the quality of the $800 driver to less than that of the $120 direct coupled unit.
Sure you need more amps but at lower power ratings and most would be aware of the many other benefits of bi-amping.
In the end, it is my experience, that it is cheaper to use good quality mid priced drivers directly connected than to pay for exotic, (read ridiculously priced) drivers used with passive xos.
Regards WALKER
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