I have a just bought a pair of Mission 782, which are decent Made in England 3 way speakers from the 90s, with a famous fatal flaw. The Audax made Keraform mid drivers all suffered corrosion on the coils from the glue they used reacting with the solder. It is terminal, and these ones are no exception with 2x dead mids.
I have ordered 2x Audax HM130Z12, which I have been advised are excellent replacements of much higher quality, although I am told they will require a bit of routing to make fit, which is no problem for me.
My question here is whether they genuinely are drop in replacements electrically, as the sensitivity seems to be lower than the earlier Audax HM130Z0 that Mission themselves used to replace the failing Keraforms.
The original (Mission branded) Audax Keraform 82-LF130/QS had a sensitivity I've yet to unearth. I can't find a datasheet online, and all surviving units seem to have failed due to coil corrosion.
The Audax Aerogel HM130Z0 that Mission used to replace these dead units has a sensitivity of 92dB
The Audax Aerogel HM130Z12 that I've ordered (as some say they are an improved version) has a sensitivity of 87.8dB
I'm guessing I may end up with a more laid back midrange than is optimal. Is that likely? Would I then need to attenuate the tweeter and bass drivers to flatten the response? What's the best way of assessing this?
Many thanks
Lucas
I have ordered 2x Audax HM130Z12, which I have been advised are excellent replacements of much higher quality, although I am told they will require a bit of routing to make fit, which is no problem for me.
My question here is whether they genuinely are drop in replacements electrically, as the sensitivity seems to be lower than the earlier Audax HM130Z0 that Mission themselves used to replace the failing Keraforms.
The original (Mission branded) Audax Keraform 82-LF130/QS had a sensitivity I've yet to unearth. I can't find a datasheet online, and all surviving units seem to have failed due to coil corrosion.
The Audax Aerogel HM130Z0 that Mission used to replace these dead units has a sensitivity of 92dB
The Audax Aerogel HM130Z12 that I've ordered (as some say they are an improved version) has a sensitivity of 87.8dB
I'm guessing I may end up with a more laid back midrange than is optimal. Is that likely? Would I then need to attenuate the tweeter and bass drivers to flatten the response? What's the best way of assessing this?
Many thanks
Lucas
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Others have said they work exceptionally well.
They are both mids and easily cover the same frequencies. Both 130mm. They are different sensitivity, hence my questions.
Just a thought. You’re not confusing the Mission 782 with the Mission Cyrus 782 by any chance? Completely different speakers from the 80s.
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If only! I can’t seem to find it. I could open up the crossover and have a direct look I guess.
Good advice about the woofers there. Of course! So, I guess I’ll just try them when they arrive, and see if I need to slightly attenuate the tweeters.
Thanks for replying!
It's not just the sensitivity that's going to be different though. The entire lower end roll off of the mid range driver is going to be different too, along with a different shaped impedance peak.
Others may have said it works well but from what I've seen one guy online says he replaced one set of broken 782s with Z0s and one set with Z12s. Apparently both sound amazing...These two drivers are like chalk and cheese in terms of their compatibility as drop in replacements. In other words a speaker designed for the Z12s would not work well, in the slightest, with the Z0s and visa versa.
I find it very hard to believe that the Keraform units, in the original speakers, were of particularly high sensitivity. Quite the opposite in fact. The Keraform speakers are far more in line with Audax's AP, plastic chassis, range of speakers, with smaller magnets and lower sensitivities vs their more upmarket offerings.
Neither the HM130Z0 or Z12 will be suitable as drop in replacements and as to which is the most suitable is anyone's best guess. My guess would be that the Z12 probably is but that's just a guess. Either way I would expect both to require crossover modification to work properly.
If Mission carried out replacements with the HM130Z0, for individuals of broken 782s, then naturally they'd have to rework the cabinets for them and could quite easily have altered the crossover to suit the different drivers too.
Good luck.
From what I remember of a review article with the 782s they were very insensitive speakers to start with, like 83dB or something, so I wouldn't worry about the Z12s being only 88dB. You can easily attenuate, or remove attenuation, from the current crossover.
Others may have said it works well but from what I've seen one guy online says he replaced one set of broken 782s with Z0s and one set with Z12s. Apparently both sound amazing...These two drivers are like chalk and cheese in terms of their compatibility as drop in replacements. In other words a speaker designed for the Z12s would not work well, in the slightest, with the Z0s and visa versa.
I find it very hard to believe that the Keraform units, in the original speakers, were of particularly high sensitivity. Quite the opposite in fact. The Keraform speakers are far more in line with Audax's AP, plastic chassis, range of speakers, with smaller magnets and lower sensitivities vs their more upmarket offerings.
Neither the HM130Z0 or Z12 will be suitable as drop in replacements and as to which is the most suitable is anyone's best guess. My guess would be that the Z12 probably is but that's just a guess. Either way I would expect both to require crossover modification to work properly.
If Mission carried out replacements with the HM130Z0, for individuals of broken 782s, then naturally they'd have to rework the cabinets for them and could quite easily have altered the crossover to suit the different drivers too.
Good luck.
From what I remember of a review article with the 782s they were very insensitive speakers to start with, like 83dB or something, so I wouldn't worry about the Z12s being only 88dB. You can easily attenuate, or remove attenuation, from the current crossover.
Hmm. I guess I am a bit disappointed to hear that they may not work well, considering how hyperbolic some reviews of this speaker swap are. That's what you get for reading reviews I guess - people like their own stuff!
The roll off at the bottom end won't be the same, that is true, but it may not be unpleasant, or make as much difference as say, room placement - we will see. These newer Aerogel drivers are generally much better drivers which is promising, and I am happy to make some crossover changes if necessary. I've done that extensively on some Celestion Ditton 44 speakers on which I replaced the tweeters and electro capacitors. Any advice would be welcome.
The roll off at the bottom end won't be the same, that is true, but it may not be unpleasant, or make as much difference as say, room placement - we will see. These newer Aerogel drivers are generally much better drivers which is promising, and I am happy to make some crossover changes if necessary. I've done that extensively on some Celestion Ditton 44 speakers on which I replaced the tweeters and electro capacitors. Any advice would be welcome.
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Thanks for that! It looks like that's the bass low-pass on the left board, and the rest on the right, wouldn't you say? Ferrite inductors and bipolar electrolytic caps, huh. Although there's nothing wrong with those components per se, it's hardly high end as some have suggested.
Thanks for sharing your wisdom with me. If you were trying to integrate these drivers into these speakers, how would you go about it? I mean, what's the process of evaluating what needs to be changed? Thanks
That would appear to be the case. According to the specs here Mission 782 | Loudspeaker | Sound Production Technology the crossover details are:
1st order LF; Acoustic 2nd order MF; 2nd order HF with crossover frequencies of 195Hz and 2.5kHz.
The speaker's sensitivity is quoted as 89 dB/2.83V/m
As you have tweaked some Celestion Ditton 44s, can you find the crossover in your mission loudspeakers and verify the component values? I could give you a hand with some measurements if you are nearby to Cambs once we are out of this phase of lockdown.
I know nothing of the keraform material so i do not know if it was more sensitive or less sensitive than the aerogel.
As you suggest, if you fit them you will have sound from them, as long as nothing else is damaged, miraculously it may sound good or less than good.
Don't forget to connect them initially with the same polarity as the originals, if they sound less than well integrated you could try swapping the polarity, but normally that would make the situation even worse with two nulls at the crossover frequency.
I know nothing of the keraform material so i do not know if it was more sensitive or less sensitive than the aerogel.
As you suggest, if you fit them you will have sound from them, as long as nothing else is damaged, miraculously it may sound good or less than good.
Don't forget to connect them initially with the same polarity as the originals, if they sound less than well integrated you could try swapping the polarity, but normally that would make the situation even worse with two nulls at the crossover frequency.
Thanks. That’s really kind of you. The data sheet for the new Audax drivers suggests they are just about at their rolloff limits, but ok from 190 Hz to 2.5khz - not sure if that’s actually good or if this would normally be considered too tight.
https://en.toutlehautparleur.com/media/catalog/product/datasheet/audax/HM130Z12-8.pdf
https://en.toutlehautparleur.com/media/catalog/product/datasheet/audax/HM130Z12-8.pdf
I had a look for the thread where the suggestion for the replacement driver came from and now you have posted some driver data i cannot see it needing too much effort to get something workable, maybe just some resistive padding. I wouldn't be surprised if it wasn't reasonable on the first try.
The thread did suggest you need to be handy at either modifying the cabinet or the driver faceplate to get it to fit into the enclosure and faceplate moulding. That looks more intricate than tweaking or redesigning the crossover to me.
Good luck with that bit.
The thread did suggest you need to be handy at either modifying the cabinet or the driver faceplate to get it to fit into the enclosure and faceplate moulding. That looks more intricate than tweaking or redesigning the crossover to me.
Good luck with that bit.
They finally arrived today. I have fitted one of them. Interesting process. They don't fit as standard, as the surrounds are too chunky. Beautifully made drivers though.
I didn't use either the "rout the MDF" of the cabinet nor the "carve the aluminium driver surrounds" methods.
Because I may use the drivers on another project later on, I didn't want to cut into the driver aluminium at all. Also, I just spent £135 on them, and waited nearly 2 months for them to arrive from France!
I had planned to rout the MDF to make them fit that way, but then the drivers are quite set back from the plastic surrounds by about 7mm and that seems quite sonically unsound as well as not looking right at all. I wanted a snug fit, just like the originals.
Instead, I went for a new method, carving the plastic tweeter plate, which I had to do such that I made 4x visible holes to accommodate the shoulders of the driver. Yes, it looks a mess in a way, but for me it was the best compromise, as it is sonically the soundest and besides, I always use the speaker covers (kids!)
I didn't use either the "rout the MDF" of the cabinet nor the "carve the aluminium driver surrounds" methods.
Because I may use the drivers on another project later on, I didn't want to cut into the driver aluminium at all. Also, I just spent £135 on them, and waited nearly 2 months for them to arrive from France!
I had planned to rout the MDF to make them fit that way, but then the drivers are quite set back from the plastic surrounds by about 7mm and that seems quite sonically unsound as well as not looking right at all. I wanted a snug fit, just like the originals.
Instead, I went for a new method, carving the plastic tweeter plate, which I had to do such that I made 4x visible holes to accommodate the shoulders of the driver. Yes, it looks a mess in a way, but for me it was the best compromise, as it is sonically the soundest and besides, I always use the speaker covers (kids!)
