Hello, I would greatly appreciate any help solving a distortion problem in the TL12s I am building.
There is a significant sibilance at the HF end of the ATC SM75-150 mid range speaker. It sounds as if the speaker is mounted on a sheet of thin ply rather than the 1" MDF baffle it is securely bolted to, I exagerate as it is only noticeble on quiet passages, particularly piano music. And the distortion is present even when the speaker is on the bench.
Both speakers suffer the same problem. I have no reason to suspect a problem with the amp so I suspect the crossover. It is the standard WA Prestige Xover design but I am using (on the adviceof WA) the Scanspeak R3004/662001 (4 Ohm) rather than the usual D2905/9900 (6 Ohm). I note WA have increased the series resistor to the tweeter to 1R5 rather than 1R. The only other changes they have made are to the mid circuit: 1R rather than 1R2 on the series resistor and 1R5 rather than 1R2 on resistor in series with the 6.8uF cap. I am sorry to say my understanding of Xover electronics is very poor.
Until I can remove the distortion there is no point in seeking further refinements.
If anyone can provide advice on this problem it would be very helpful.
Thank you.
There is a significant sibilance at the HF end of the ATC SM75-150 mid range speaker. It sounds as if the speaker is mounted on a sheet of thin ply rather than the 1" MDF baffle it is securely bolted to, I exagerate as it is only noticeble on quiet passages, particularly piano music. And the distortion is present even when the speaker is on the bench.
Both speakers suffer the same problem. I have no reason to suspect a problem with the amp so I suspect the crossover. It is the standard WA Prestige Xover design but I am using (on the adviceof WA) the Scanspeak R3004/662001 (4 Ohm) rather than the usual D2905/9900 (6 Ohm). I note WA have increased the series resistor to the tweeter to 1R5 rather than 1R. The only other changes they have made are to the mid circuit: 1R rather than 1R2 on the series resistor and 1R5 rather than 1R2 on resistor in series with the 6.8uF cap. I am sorry to say my understanding of Xover electronics is very poor.
Until I can remove the distortion there is no point in seeking further refinements.
If anyone can provide advice on this problem it would be very helpful.
Thank you.
WA TL12
PRESTIGE
The driver line up for both of the above variants is:
Treble: Scanspeak D2905/9900.00
Midrange: Volt VM753 (successor to the now discontinued ATC SM75-150)
Bass: Volt Rv3143
I presume you've not yet made the resistor changes recommended for the standard crossover?
Can you supply the relevant crossover schematic?
PRESTIGE
The driver line up for both of the above variants is:
Treble: Scanspeak D2905/9900.00
Midrange: Volt VM753 (successor to the now discontinued ATC SM75-150)
Bass: Volt Rv3143
I presume you've not yet made the resistor changes recommended for the standard crossover?
Can you supply the relevant crossover schematic?
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Can you provide measurements of the response? Even crude ones with a laptop mic or phone mic may be enough if the issue is serious. Without evidence it is likely to be very difficult to diagnose the problem/s.
Prior to the recent change of ownership Wilmslow was in pretty poor shape when it came to basic competence with respect to crossovers as can be seen in several threads on here. The fact you are using an ATC driver suggests this may not be a current kit. Do you know the age of the kit and crossover?
I bought the drivers and crossovers back in 2011. This is the crossover I have:
with the following changes ( made by WA not me ):
Mid R3 is 1R; R4 is 1R5
Tweeter R6 is 1R5
I am afraid I don't have a mic or any relevant software.
with the following changes ( made by WA not me ):
Mid R3 is 1R; R4 is 1R5
Tweeter R6 is 1R5
I am afraid I don't have a mic or any relevant software.
So, it is only now that you've started building the speakers that you've had a chance to listen to the midrange drivers in context.
The resistor changes look small, but may be significant in terms of the mid and treble response. Hopefully the crossover experts will chime in.
How handy are you with a soldering iron?
I'm OK at soldering, I have done a few electronics circuits (and a lot of car wiring) and have a basic knowledge of the subject but crossovers are new to me. I don't have much stock of 10W resistors and no suitable capacitors so I won't be able to make any substitutions until I order some parts.
As you say I have had the kit for a long time, but now I have the time as well 😱
When I listened to the Prestige kit I noticed some cabinet vibration so went for a TL cabinet as that should be rigid. My previous speakers were from WA, a Kef based TL back in 1978 and they are used every day and still going strong !
As you say I have had the kit for a long time, but now I have the time as well 😱
When I listened to the Prestige kit I noticed some cabinet vibration so went for a TL cabinet as that should be rigid. My previous speakers were from WA, a Kef based TL back in 1978 and they are used every day and still going strong !
I'll give your thread another bump.
It's unlikely that bipolar electrolytic capacitors such as the 100uF C4 in the mid filter would have deteriorated substantially in just 10 years or so.
Have you inspected the crossovers for any signs of deterioration, and can you attach a photograph for the record?
It's unlikely that bipolar electrolytic capacitors such as the 100uF C4 in the mid filter would have deteriorated substantially in just 10 years or so.
Have you inspected the crossovers for any signs of deterioration, and can you attach a photograph for the record?
That looks to be around the time Wilmslow were having problems. This long thread starting in 2012 may well be worth reading. The OP started from a similar position as you and then did almost nothing to help himself. It looks like Wilmslow had sold him a crossover with incorrect parts and then made some extraordinary statements to avoid sorting out in the way a normal business would. Note Wilmslow today is not the Wilmslow of 2011/12 and they may well be worth contacting to sort out issues when you have some solid evidence on which to base a discussion.
You have mics in your phone, tablet, laptop, headset, desktop and possibly one or two other places and there is plenty of free software around. You may not want to make the effort and the quality of the measurements may be too low depending on the issue but you almost certainly have the option.
A reasonable measurement mic costs about £25 but you will need a box to power and convert it to a digital signal if you don't already possess something suitable. This will raise the cost to around £100. There is plenty of good free and low cost software to take the measurements.
Attempting to diagnose and fix a problem of the type you describe (and the possibly similar one in the link) without measurements will be extremely difficult. It will be made worse by people with the knowledge to help being put off by vague audiophile descriptions of the issue whereas those without may well post all sorts of "helpful" random suggestions.
Here is the photo of the supplied crossover. I have checked them for loose connections ( found one which I resoldered).
I am certainly happy to get some software and a mic ( I notice my PC has a mic input ). But what kindof software am I looking for? The only vaguely relevant software I have loaded is Audacity.
I have read the long thread, it was that thread that prompted me to post my problem.
Thanks for your interest so far.
I am certainly happy to get some software and a mic ( I notice my PC has a mic input ). But what kindof software am I looking for? The only vaguely relevant software I have loaded is Audacity.
I have read the long thread, it was that thread that prompted me to post my problem.
Thanks for your interest so far.
That's certainly an easy crossover layout to work on!
The Supersound capacitors are no longer supplied by Wilmslow audio, but apparently were polypropylene types. Polypropylene capacitors do not deteriorate.
The Supersound capacitors are no longer supplied by Wilmslow audio, but apparently were polypropylene types. Polypropylene capacitors do not deteriorate.
Well that was an interesting afternoon. I managed to find a mic and downloaded Audmes. I couldn't find any user instructions but managed to get a FR graph but can find no way of saving the image, the only output file type is .cav ( a new one on me but I could only read it a column of numbers as I don't have Office). Unfortunately it is not a permitted file type for uploading. If anyone can tell me how I can save the image of the FR plot that would very helpful. Pending that I have just photographed the screen ( the sort of thing I did 40+ years ago 🙂
It doesn't look very useful to me, I could hear a tone well before 100Hz but nothing beyond 10K but I didn't expect to as I doubt my hearing is that good.
It doesn't look very useful to me, I could hear a tone well before 100Hz but nothing beyond 10K but I didn't expect to as I doubt my hearing is that good.
Thank you Andy, just the advice I needed as I do not know much anything this type of software. I do know a certain amount about time series analysis and frequency spectra from some work I did back in 1970s so more than a bit rusty ! So I hope with the aid of some proper documention I will be able to produce something more useful.
I look forward to another interesting days study tomorrow🙂 ( something else new, I have never tried smilies before either ).
I look forward to another interesting days study tomorrow🙂 ( something else new, I have never tried smilies before either ).
The REW software is certainly impressive and with excellent documentation. It will take me a while to get to grips with it. It warns that the signal level from my mic ( a measurement mic ) is very low, and the PC's built in sound card doesn't have a powerful enough amp.
But I have been doing some swapping and wired up a different midrange ( Kef B110 ) and there was no distortion. I also hooked the ATC SM75-150 to a different crossover and get the same sibilance so it is hard not to conclude that both my ATC speakers are damaged: no idea how or why but as I bought them back in 2011 I can't see WA replacing them. Btw I have emailed and tried to phone WA in the past couple of weeks about a different issue and received no replies, they didn't answer the phone so I left a message. I wonder if they have shut up shop the duration ?
Many thanks for your help, I will now ponder my options.
But I have been doing some swapping and wired up a different midrange ( Kef B110 ) and there was no distortion. I also hooked the ATC SM75-150 to a different crossover and get the same sibilance so it is hard not to conclude that both my ATC speakers are damaged: no idea how or why but as I bought them back in 2011 I can't see WA replacing them. Btw I have emailed and tried to phone WA in the past couple of weeks about a different issue and received no replies, they didn't answer the phone so I left a message. I wonder if they have shut up shop the duration ?
Many thanks for your help, I will now ponder my options.
Slightly confused. What type of microphone are you using? A conventional measurement microphone is a capacitor/condenser which takes "phantom" power from the DAC, mixer or whatever box that contains the mic preamp and gain knob (to fiddle with to get good S/N in REW). A normal builtin PC sound card will not provide "phantom" power or an analogue mic preamp gain knob although you can likely get plugin cards that do.
First you need to measure them in order to identify the issue. If you are running a midrange without a (correctly functioning!) crossover you can fool yourself. See that long thread for an example. A measurement sweep will show both the response and the levels of distortion.
If there is a problem I would ring ATC first to discuss what has happened, what caused it and repair costs. It is a pro driver and so repairs are routine unlike with home drivers. Then armed with maximum information ring Wilmslow if the damage could conceivably be laid at their door. They no longer supply ATC drivers and weren't the owners at the time of the problem so it would be a remarkable act of goodwill for them to pay for a repair/replacement but likely worth a phone call.
Thanks Andy. I have a measurement mic but didn't realise it would need a pre-amp and phantom supply. I will buy an ordinary mic. I will also try to find my small LCD meter ( another trip to the attic!) so I can measure the three unmarked inductors.
I built a pair of TL15s a couple of years ago and they are amazing. I am delighted with them. The drivers are a bit different from yours and I designed my own crossovers with the help of XSim. I bought an Omnimic V2 for all the measurements and it worked out very well using a laptop. I feel sure that would give you all the measurements you need and help you find the cause of the problem.
I am glad your TL15s turned out well. I bought a ( cheap ) mic and plugged that into my sound card, I get a moving blue bar on windows-settings-sounds so it looks as if the mic is working, but I can't get REW or Audacity ( or windows voice recorder ) to read from the mic. Very frustrating. I will borrow my wife's laptop and give that a try. I was hoping at least to record the distortion I am hearing. It is only really noticeable on piano music, but as that is my particular interest it currently renders these none-too-cheap speakers useless.
But it looks as if my ATC mid range speakers are at fault but before sending them off for repair I will try connecting another mid range to the speakers; it just seems very unlikely I could have received two faulty speakers.
Which drivers did you use ?
But it looks as if my ATC mid range speakers are at fault but before sending them off for repair I will try connecting another mid range to the speakers; it just seems very unlikely I could have received two faulty speakers.
Which drivers did you use ?