I still can't get away from the multiple comments from KatieandDad, others, and the e-mail I got yesterday from them, that they are using the same crossover for both the ATC mid and Volt mid.
I don't have enough passive crossover experience to be certain, but if you designed a crossover for approx 380 hz and 3800 hz with the 16 Ohm ATC mid, and used it with an 8 Ohm volt mid, would this not affect the crossover points?
If so, this could explain it all. My crossovers may be perfect for a 16 ohm ATC mid......
I don't know if this is relevant at all, but when doing the measurements, you could hear the mid and tweeter 'oscillating' with a high pitch noise as the sine wave swept up gradually.
I don't have enough passive crossover experience to be certain, but if you designed a crossover for approx 380 hz and 3800 hz with the 16 Ohm ATC mid, and used it with an 8 Ohm volt mid, would this not affect the crossover points?
If so, this could explain it all. My crossovers may be perfect for a 16 ohm ATC mid......
I don't know if this is relevant at all, but when doing the measurements, you could hear the mid and tweeter 'oscillating' with a high pitch noise as the sine wave swept up gradually.
My guess is that what they mean by same crossover is the same circuit, with the same crossover points but different component values for the different drivers. Some evidence to support this is that the lower crossover point for the midrange is 500Hz which is where one would expect it to be particularly as the midrange resonance seems to be in evidence. Wilmslow saying it should be 380Hz would be me more of a concern to me and, if you are OK with designing crossovers, I would be tempted to offer to sort out the design for them if they supplied the parts.
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To put this whole question to rest I have e-mailed them to ask if my crossovers could be the gold version designed for the ATC mid and whether this could be the problems with the measured crossover points.
If they are using the same crossover layout but with different value components for the 16 ohm volt versus the 8 ohm ATC, then their answer should confirm this.
I await their response.
Here are some quotes from earlier in this long thread (there are more):
If they are using the same crossover layout but with different value components for the 16 ohm volt versus the 8 ohm ATC, then their answer should confirm this.
I await their response.
Here are some quotes from earlier in this long thread (there are more):
Yes the 3rd order low pass works best. If you want to crossover at 380Hz then use 5.2mH + 120uf + 1.8mH for the RV3143. Adjust the resistor in series with 120uF cap to fine tune. (I used zero ohms).
The low pass filter for the bass is very critical to obtain good integration with the atc. This is because the atc acoustic low pass is 24db/octave and so not much margin for error when setting the bass low pass. If you get it wrong things can easily sound horrible.
I also found that using a 3rd order filter for the tweeter improved the sound and phase tracking with the atc.
The low pass filter for the bass is very critical to obtain good integration with the atc. This is because the atc acoustic low pass is 24db/octave and so not much margin for error when setting the bass low pass. If you get it wrong things can easily sound horrible.
I also found that using a 3rd order filter for the tweeter improved the sound and phase tracking with the atc.
Got a response from WA. Things are clearer now:
Hi
As I said below, the crossover is basically the same, so there should not be that much difference in performance.
Regards
----- Original Message -----
Sent: Wednesday, April 29, 2015 9:47 AM
Subject: RE: Crossovers
Hi,
Just had a thought regarding the wrong crossover points on my measurements.
Could it be that I have the crossovers for the ATC mid dome, instead of the crossovers for the Volt mid dome?
Cheers,
It is clear that they are using exactly the same crossovers for both domes as I suspected. The same layout, the same circuit and the same components and component values.
Now that this is certain, I suspect that the crossovers I have are made correctly and may work as intended with a 16 ohm ATC mid.
I do not think there has been a manufacturing error or quality control problem here, I think that they are intentionally using one crossover for both speaker variations.
Hi
As I said below, the crossover is basically the same, so there should not be that much difference in performance.
Regards
----- Original Message -----
Sent: Wednesday, April 29, 2015 9:47 AM
Subject: RE: Crossovers
Hi,
Just had a thought regarding the wrong crossover points on my measurements.
Could it be that I have the crossovers for the ATC mid dome, instead of the crossovers for the Volt mid dome?
Cheers,
It is clear that they are using exactly the same crossovers for both domes as I suspected. The same layout, the same circuit and the same components and component values.
Now that this is certain, I suspect that the crossovers I have are made correctly and may work as intended with a 16 ohm ATC mid.
I do not think there has been a manufacturing error or quality control problem here, I think that they are intentionally using one crossover for both speaker variations.
Yes the 3rd order bass filter provides excellent phase tracking with the atc and is a much closer match to the 24db/octave slope of the atc. The atc high pass crossover is 12dB/octave electrical but results in 24dB/octave acoustic when combined the natural response of the driver. Both drivers should be connected in phase. If you reverse the connection to the atc you will see a big cancellation at around 380Hz.
They are not clearer to me because they used the word basically which means there are some differences. What are those differences? Are they different component values to give the same crossover frequencies? Or something else? Or should the word basically have been omitted?
Even if they do mistakenly believe that the ATC and Volt drivers are substitutes for each other, which I still find hard to believe, it doesn't mean they won't fix their mistake if they are made aware of it. My concern, as I mentioned above, is that if they did believe the ATC and Volt were substitutes for each other it might be preferable to fix the crossover yourself and give it to them in exchange for the parts rather than have them do it.
The word basically should be omitted. They are the same components. I have clarified this. I have therefore decided to diy my crossover, and as both ATC and quested used 24db active crossovers at the points mentioned earlier in this thread I will start there. I have spare amps and measurement gear so this is not a problem.
It is clear from their response that they feel the crossover points should not differ if I have the gold or the platinum crossover. This speaks for itself.
I have sent them the freq response graph you have seen and explained carefully my concerns that the mid-tweeter crossover point is 2.5khz resulting in a major dip in response (as if that isn't clear in the graph). I have sent them a photo of the actual crossovers.
I have then asked if it could be that I have a crossover optimised for the ATC mid rather than the volt mid. They have told me the graph is OK, the crossover is the correct one, and that it doesn't matter which crossover I have because they are 'basically the same' and therefore it will have no bearing on the acoustic slopes produced.
What am I missing here? Even a novice speaker builder would know this is completely wrong.
It is clear from their response that they feel the crossover points should not differ if I have the gold or the platinum crossover. This speaks for itself.
I have sent them the freq response graph you have seen and explained carefully my concerns that the mid-tweeter crossover point is 2.5khz resulting in a major dip in response (as if that isn't clear in the graph). I have sent them a photo of the actual crossovers.
I have then asked if it could be that I have a crossover optimised for the ATC mid rather than the volt mid. They have told me the graph is OK, the crossover is the correct one, and that it doesn't matter which crossover I have because they are 'basically the same' and therefore it will have no bearing on the acoustic slopes produced.
What am I missing here? Even a novice speaker builder would know this is completely wrong.
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Your plot does not really show a crossover at 2.5kHz. It shows a tweeter being high passed to cross at around 3 kHz and a midrange being low passed to cross around 1.8 kHz. But the woofer/midrange crossover at 500Hz looks to be as intended for a Volt midrange.
An ATC crossover would low pass the woofer at 380Hz which your plot does not show. An ATC crossover would be very unlikely to correctly high pass the Volt at 500Hz but I haven't checked. Etc... This does not look like an ATC crossover or a Volt crossover. It looks like a mistake which I would expect any business to fix if given the chance.
Have they seen the graph or only been told that it crosses at 2.5kHz? It may be of some relevance that the slopes will indeed not change.
It is not completely wrong. It could be fixed to a large extent by simply doubling the crossover frequency of the midrange low pass.
I can see nothing to suggest this is a correct Platinum or Gold crossover. It looks to me like a Platinum crossover with a fault.
Perhaps you are right.
I do not wish to get into a pedantic argument with you about what is wrong with the crossovers.
I am sending them back to WA, as they have offered to check them.
As I have said twice already I sent them the graph and the photo.
It is difficult to turn a blind eye to their responses:
They do not seem to appreciate that a crossover designed for a 16 ohm driver with different parameters and frequency response will not work in the same way with an 8 ohm completely different driver - having reread you post, is it possible that the slopes would not be affected??
They do not see a problem crossing the volt mid with an fs of 400 at 380.
They do not see a problem with the graph I sent them despite the fact it is obviously wrong.
These points are not confidence inspiring.
Do you not think this is bizarre?
How does your theory of a simple error in the crossover construction tie in with these responses?
Currently I would have much greater faith in you being able to design a decent crossover than them...
I do not wish to get into a pedantic argument with you about what is wrong with the crossovers.
I am sending them back to WA, as they have offered to check them.
As I have said twice already I sent them the graph and the photo.
It is difficult to turn a blind eye to their responses:
They do not seem to appreciate that a crossover designed for a 16 ohm driver with different parameters and frequency response will not work in the same way with an 8 ohm completely different driver - having reread you post, is it possible that the slopes would not be affected??
They do not see a problem crossing the volt mid with an fs of 400 at 380.
They do not see a problem with the graph I sent them despite the fact it is obviously wrong.
These points are not confidence inspiring.
Do you not think this is bizarre?
How does your theory of a simple error in the crossover construction tie in with these responses?
Currently I would have much greater faith in you being able to design a decent crossover than them...
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I think the level of ignorance and incompetence being levelled at Wilmslow is hard to believe and so rather than piling on I am trying to work out what is fact and what is assumption. A bit unusual in a forum I know but we all have our own interests.
For what it is worth, the crossover does not appear to do what one might expect for a speaker at this price point in terms of adapting to the baffle, compensating for the midrange resonance and the like. However, without being able to see the response from a correctly functioning crossover it is probably unwise to be too judgemental.
The cabinet would also seem to need some attention. The tall single chamber would perhaps need dividing, the large surface areas braced, some significant form of damping adding,... I would expect at least the wood for the internals to be supplied with a kit at this price point.
It doesn't look like a bad kit (assuming the crossover gets fixed) but it does seem to lack the sophistication one might expect at the price point. Although to be fair, the cost without the drivers is modest and so perhaps this isn't quite fair.
Again you may be right. Perhaps my emails have been answered by a sales person rather than one of the engineers and they are just plain wrong.
But the others I have quoted earlier got similar answers.
I guess all that is left to do it send them back and see what happens.
In a way it doesn't affect the project too much for me as I was always likely to use an active implementation due to the points I have raised earlier.
Thank you for your insight into this though, and I do hope you are right, WA have always been helpful and responsive in the past.
It would be a real shame if they were just using an off the shelf crossover with no proper measurement or consideration to the complexities.
But the others I have quoted earlier got similar answers.
I guess all that is left to do it send them back and see what happens.
In a way it doesn't affect the project too much for me as I was always likely to use an active implementation due to the points I have raised earlier.
Thank you for your insight into this though, and I do hope you are right, WA have always been helpful and responsive in the past.
It would be a real shame if they were just using an off the shelf crossover with no proper measurement or consideration to the complexities.
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