Also bear in mind that the person I bought these from told me that they were WA's own demo pair of the older style of cabinet, I would hope that they would be demoing the actual model they were selling. It might be that the crossovers were altered when the new design boxes came out?
Can't make much sense of the many variations of Prestige being discussed here, but I've been looking at bushmeister's inherited crossover. Here's a review.
Correct polarity is ++-. Anything else is due to inaccuracies in component values.
Problem with Katieanddad's filter was it had too much rolloff on the mid, and should really have a second order tweeter filter for an LR2 response at the top end. Crossing from bass to mid is problematic, because it's near butterworth 90 degree phase difference.
I have a feeling we are talking about ATC SM75-150 16 ohm here. And a ring radiator. Just have to hope the ring radiator works on a second order.
My advice is to lose the 100uF, the 8uF and change the 0.9mH to something between 0.4 and 0.5mH. It will all look a lot better then. Impedance stays above 4 ohms.
Correct polarity is ++-. Anything else is due to inaccuracies in component values.
Problem with Katieanddad's filter was it had too much rolloff on the mid, and should really have a second order tweeter filter for an LR2 response at the top end. Crossing from bass to mid is problematic, because it's near butterworth 90 degree phase difference.
I have a feeling we are talking about ATC SM75-150 16 ohm here. And a ring radiator. Just have to hope the ring radiator works on a second order.
My advice is to lose the 100uF, the 8uF and change the 0.9mH to something between 0.4 and 0.5mH. It will all look a lot better then. Impedance stays above 4 ohms.
Attachments
In 2013 Wilmslow Audio sent me this in an email:
"Looking back at what we have been supplying over the last few months, it seems that we have returned to using the same crossover for both the Gold and Platinum designs. The main parameters of the two midranges are very similar and although we did have slightly different designs for both, we have found that the Gold crossover does actually produce a better soundstage than our original Platinum design. However it quite often comes down to individual hearing. So if you feel after running them for a while, that the sound needs tweaking, we would be happy to advise accordingly
If you change the tweeter from the Gold to the Platinum unit, you may need to change the resistor value, but again that depends more on how they sound than a theoretical design. So again, see how they sound and if a tweak is required, we would be pleased to advise."
The Gold Prestige used ATC midrange drivers while the Platinum used Volt. The frequency responses for these drivers are quite different, esp at the lower end. I was surprised to say the least.
"Looking back at what we have been supplying over the last few months, it seems that we have returned to using the same crossover for both the Gold and Platinum designs. The main parameters of the two midranges are very similar and although we did have slightly different designs for both, we have found that the Gold crossover does actually produce a better soundstage than our original Platinum design. However it quite often comes down to individual hearing. So if you feel after running them for a while, that the sound needs tweaking, we would be happy to advise accordingly
If you change the tweeter from the Gold to the Platinum unit, you may need to change the resistor value, but again that depends more on how they sound than a theoretical design. So again, see how they sound and if a tweak is required, we would be pleased to advise."
The Gold Prestige used ATC midrange drivers while the Platinum used Volt. The frequency responses for these drivers are quite different, esp at the lower end. I was surprised to say the least.
The Volt wants crossing at about 500 Hz given the 400 Hz Fs and indeed this looks to be about where it is crossed in Bushmeister's plot. The ATC probably wants crossing at about the same place given the small surface area but it often seems to be crossed a 100Hz or so lower. At the top end the crossover frequency should probably lie somewhere around 3-4kHz and it is this that looks wrong in Bushmeister's plot.
As has been said before, the advertised Volt and ATC drivers have both different sensitivities and different impedances and so cannot use the same values in the crossover. I find it hard to believe that people working at Wilmslow Audio would not know that. It is possible to interpret your quoted post to mean that the Gold and Platinum are slightly different circuits with appropriate values for the Volt and ATC drivers rather than the same circuit with one set of values for the Volt driver and one set for the ATC driver. Can anyone rule out one of the interpretations?
For what it's worth:
According to their publications ATC themselves cross the mid at 380 and 3800Hz for both the 'S' and non 'S' versions, active and passive.
Don't know about the passive version but the active ones use 24dB Linkwitz-Riley.
ATC list the Fs as 320Hz in their driver data pdf.
Quested use the Volt mid and cross at 450 and 4500Hz, 24dB L-R active according to their site.
According to their publications ATC themselves cross the mid at 380 and 3800Hz for both the 'S' and non 'S' versions, active and passive.
Don't know about the passive version but the active ones use 24dB Linkwitz-Riley.
ATC list the Fs as 320Hz in their driver data pdf.
Quested use the Volt mid and cross at 450 and 4500Hz, 24dB L-R active according to their site.
If anyone knows the equivalent frequencies for the PMC version I would be very interested to know. I think it is the same as ATC.
It could still mean the same circuit with appropriate values of the components to match the set of drivers or the same circuit with the same values of the components to match, presumably, only one set of drivers.
I agree, it could mean that but from what I was told by WA they were supplying the same product, not a variation of it.
I found reference to this on a PMC dealer's website and they use the 380 and 3800Hz points - the same as ATC. Taken together with the PMC drivers being mechanically similar to the ATC ones it would seem that they are one-for-one replacements.
They might still differ in impedance and sensitivity.
Should be easy to measure, the hard bit is getting hold of them in the first place.
So that still leaves two questions in my mind:
1. Is the crossover you have correct for your drivers?
2. Is the crossover I have correct for my drivers (with the different treble and bass units)?
True. I have done the hard bit (got hold of a pair!) but it's highly unlikely that anyone else has them outside of PMC boxes.
The first problem will be establishing which is the correct crossover! Mine seem to be far larger and more complicated than the ones in the picture you posted.
Have they confirmed that the supplied values are correct or just that it looks like one of their crossovers? The high pass for the tweeter and the low pass for the midrange are clearly not aligned with the latter looking to be at about half the intended frequency.
Did they see the frequency response? If they did and have replied that these are correct crossovers then that would be extraordinary.
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