24-01-2022, 11:13 PM
The Arcam has two sets of outputs - switched and unswitched. They do that for the benefit of those who believe switches in headphone sockets can cause distortion. Not all that unreasonable really - we all know that switched can become tarnished and noisy.
Earlier A60s used DIN sockets with an extra pin, so it depends on which way round you insert the plug. Later versions used 4mm sockets, 2 black and 4 red. Whatever the arrangement, it should be clear from the labelling on the rear panel, and if not, have a look at the instruction manual. All versions can be downloaded FOC from here: https://www.hifiengine.com/manual_librar.../a60.shtml
Incidently, the later manual says that the A60 is happy with 4-8 ohm speakers, which answers the earlier question about 6 ohm speakers. In practice, it's rarely an issue anyway. Please try to understand how impedance is something that varies wildly with frequency, so the quoted value is almost a guess. It's really common for typical "8 ohm" speakers to measure 5 or 6 ohms at certain frequencies. Look here for an example: https://www.stereophile.com/content/miss...asurements (first graph, showing it varying between just under 4 ohms at 250Hz and rising to 16.5 ohms at 2kHz).
I haven't heard the SRH440 headphones, but they seem to be well regarded. The massive spike at 10kHz is a problem - see here: https://www.rtings.com/headphones/reviews/shure/srh-440
I have a pair of Beyer DT770s that are much the same, and while they're OK for checking things during mixing in a live sound environment (because they're closed-back - they also double up as ear defenders!), I wouldn't use them for a critical mix. Or even use them for pleasure. They're a tool, bought for that specific job. The ancient Sennheiser HD480s are much smoother, but being open-back, they're no good for live sound.
Either way, we keep coming back to these damn speakers!
I'm not going to call them Mission 770 - because they are not. I sense that you might not realise just how much difference it makes when you replace the drive units. To get some perspective, have a look here: http://www.zaphaudio.com/8test/compare.html
As you click the make/model numbers above the graph, the graph will change to show the frequency response accordingly. Note that it's 5dB per division.
Try again with 6.5" woofers - there's even more variation: http://www.zaphaudio.com/6.5test/compare.html
Then do the same with tweeters: http://www.zaphaudio.com/tweetermishmash/compare.html
This guy has invested a lot of time and effort, not to mention money, in measuring drive units. He's a really good designer - you can learn a lot from looking around his website.
Hopefully, investing half an hour or so - which is nothing compared to what Zaph has done for the DIY speaker community - will give you a much clearer idea of the challenges here. Your drive units might well fit the holes left by the originals, but bear no relationship at all to the originals.
Of course, that is why the crossover had to be modified. But this mod was done remotely, by well-meaning folk on diyAudio.com, who had no way of verifying their work. This is why measurements are so important.
And in case anyone thinks I've forgotten, we've no idea if the cabinet is correctly tuned for the replacement bass driver. That is easy to check - I've described that before. Here it is: https://golbornevintageradio.co.uk/forum...2#pid86472. This post also contains a lot of what I've said again in this thread - it's all there for the taking, but it does need to be digested and understood (and I remain very willing to help answer your questions, providing - with my "teacher" hat on - they are well-formed questions that demonstrate the progress you're making). Alternatively, you could just pay someone to sort the speakers for you. Or just buy a new pair of something completely different and sell the drivers from the "Missions". I'd pay £33 for them
To assess the affect of acoustics, why not get your other speakers and put them in the space? You know (and like?) how they sound in their normal home, so see what the differences are in the new room. If you can run them on long wires from the existing system, that would be even better (so that you're not running them from different components - basic science: change as few things as possible, eliminate as many variables as possible!).
Or, why not try the "Missions" in your other system? Again, you know (and like?) the sound in that space, right? So swapping out the speakers is surely the quickest way to get a sense of how good or bad your Frankenstein "Missions" actually are. Normally I'd apologise for stating the obvious with these suggestions, but this is the sort of basic thing that I (and some others) aren't sure you've tried yet?
Sorry I've not replied to your email yet - it's been a busy day. Having said that, I think I'd prefer the conversation to be on the forum because others might benefit from it. I get this a lot with emails to my personal website - 90% of them are asking the same questions again and again, and I'm seriously tempted to set up a minimal installation of the forum software on my own site so that people can see my previous answers.
Keep going and, above all, keep it logical. One step at a time. Perhaps keep notes?
Earlier A60s used DIN sockets with an extra pin, so it depends on which way round you insert the plug. Later versions used 4mm sockets, 2 black and 4 red. Whatever the arrangement, it should be clear from the labelling on the rear panel, and if not, have a look at the instruction manual. All versions can be downloaded FOC from here: https://www.hifiengine.com/manual_librar.../a60.shtml
Incidently, the later manual says that the A60 is happy with 4-8 ohm speakers, which answers the earlier question about 6 ohm speakers. In practice, it's rarely an issue anyway. Please try to understand how impedance is something that varies wildly with frequency, so the quoted value is almost a guess. It's really common for typical "8 ohm" speakers to measure 5 or 6 ohms at certain frequencies. Look here for an example: https://www.stereophile.com/content/miss...asurements (first graph, showing it varying between just under 4 ohms at 250Hz and rising to 16.5 ohms at 2kHz).
I haven't heard the SRH440 headphones, but they seem to be well regarded. The massive spike at 10kHz is a problem - see here: https://www.rtings.com/headphones/reviews/shure/srh-440
I have a pair of Beyer DT770s that are much the same, and while they're OK for checking things during mixing in a live sound environment (because they're closed-back - they also double up as ear defenders!), I wouldn't use them for a critical mix. Or even use them for pleasure. They're a tool, bought for that specific job. The ancient Sennheiser HD480s are much smoother, but being open-back, they're no good for live sound.
Either way, we keep coming back to these damn speakers!
I'm not going to call them Mission 770 - because they are not. I sense that you might not realise just how much difference it makes when you replace the drive units. To get some perspective, have a look here: http://www.zaphaudio.com/8test/compare.html
As you click the make/model numbers above the graph, the graph will change to show the frequency response accordingly. Note that it's 5dB per division.
Try again with 6.5" woofers - there's even more variation: http://www.zaphaudio.com/6.5test/compare.html
Then do the same with tweeters: http://www.zaphaudio.com/tweetermishmash/compare.html
This guy has invested a lot of time and effort, not to mention money, in measuring drive units. He's a really good designer - you can learn a lot from looking around his website.
Hopefully, investing half an hour or so - which is nothing compared to what Zaph has done for the DIY speaker community - will give you a much clearer idea of the challenges here. Your drive units might well fit the holes left by the originals, but bear no relationship at all to the originals.
Of course, that is why the crossover had to be modified. But this mod was done remotely, by well-meaning folk on diyAudio.com, who had no way of verifying their work. This is why measurements are so important.
And in case anyone thinks I've forgotten, we've no idea if the cabinet is correctly tuned for the replacement bass driver. That is easy to check - I've described that before. Here it is: https://golbornevintageradio.co.uk/forum...2#pid86472. This post also contains a lot of what I've said again in this thread - it's all there for the taking, but it does need to be digested and understood (and I remain very willing to help answer your questions, providing - with my "teacher" hat on - they are well-formed questions that demonstrate the progress you're making). Alternatively, you could just pay someone to sort the speakers for you. Or just buy a new pair of something completely different and sell the drivers from the "Missions". I'd pay £33 for them
To assess the affect of acoustics, why not get your other speakers and put them in the space? You know (and like?) how they sound in their normal home, so see what the differences are in the new room. If you can run them on long wires from the existing system, that would be even better (so that you're not running them from different components - basic science: change as few things as possible, eliminate as many variables as possible!).
Or, why not try the "Missions" in your other system? Again, you know (and like?) the sound in that space, right? So swapping out the speakers is surely the quickest way to get a sense of how good or bad your Frankenstein "Missions" actually are. Normally I'd apologise for stating the obvious with these suggestions, but this is the sort of basic thing that I (and some others) aren't sure you've tried yet?
Sorry I've not replied to your email yet - it's been a busy day. Having said that, I think I'd prefer the conversation to be on the forum because others might benefit from it. I get this a lot with emails to my personal website - 90% of them are asking the same questions again and again, and I'm seriously tempted to set up a minimal installation of the forum software on my own site so that people can see my previous answers.
Keep going and, above all, keep it logical. One step at a time. Perhaps keep notes?
