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PostPosted: Tue Dec 12, 2017 7:44 am 
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Location: Whitby, ON, CA
For nostalgia I’m trying to refurbish some original Mission 700mk1 - photo below

Tried a Mcbride 8ACC woofer, sounded bad, missing too much middle

Saw these HI-VI PA8 on clearance and grabbed them - they weigh more than the speaker

Should I bother using them, am I way way out in left field here?

Any suggestions on what I should try to use? Original missions are impossible to find.


Thanks in advance for your help.


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PostPosted: Tue Dec 12, 2017 7:51 am 
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Check this site out: http://seventiesstereo.blogspot.ca/2010 ... -700s.html
I wouldn't just randomly throw drivers into the box just because they're the same size...they're likely quite different again from both the originals and the other ones you tried. Anyway, the site above indicates that the bass driver replacement is the Monacor SPH-210, which you can find here: http://www.bluearan.co.uk/index.php?id=MON100890
though I am sure there are other resellers...
Good luck!
B

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PostPosted: Tue Dec 12, 2017 7:52 am 
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https://www.kijiji.ca/v-speakers/ottawa ... 1317607597 they where listed on cam not long ago i believe he will ship


Last edited by rednecknber on Tue Dec 12, 2017 8:00 am, edited 1 time in total.

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PostPosted: Tue Dec 12, 2017 7:57 am 
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The box volume, port tuning (if applicable) and technically the crossover are calculated based on the Thiele/Small parameters of the original driver. Replacing the driver with something different you are technically changing the characteristic of the speaker – most likely for the worse. Better off finding a used working pair, be it original drivers or complete speaker.


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PostPosted: Tue Dec 12, 2017 8:13 am 
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Hi,

The Mission 700 was a nice speaker and you are to be commended for trying to refit a pair. However, there are real constraints. All speaker driver units have what are called Thiel-Small parameters, and these are found in the specification list for a driver unit. Examples of these parameters would be Vas and Qms. The driver that goes in, on a refit, has to pretty well match the parameters of what comes out, for the speaker to sound even vaguely similar to the original as a total unit. In your case the Monocor unit suggested above has been tried and tested with that Mission speaker in UK, where it was manufactured. Many speakers are rebuilt in the UK and there are companies that just specialize in refits. It may also be possible to source the Monocor unit in the US or Canada; try Solen in Montreal, and Madisound in Madison Wisconsin.

Finally, the actual cone material used in the originals, in this case I believe it was polypropelene, has a definite bearing on the overall sound of the speaker unit, particularly in the mid-range where voice and most instruments are reproduced. It is very difficult to perfectly match both cone material and Thiel-Small parameters when the production of a given driver ends.

Cheers,
David Neice

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PostPosted: Tue Dec 12, 2017 8:19 am 
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buybye88 wrote:
Hi,

The Mission 700 was a nice speaker and you are to be commended for trying to refit a pair. However, there are real constraints. All speaker driver units have what are called Thiel-Small parameters, and these are found in the specification list for a driver unit. Examples of these parameters would be Vas and Qms. The driver that goes in, on a refit, has to pretty well match the parameters of what comes out, for the speaker to sound even vaguely similar to the original as a total unit. In your case the Monocor unit suggested above has been tried and tested with that Mission speaker in UK, where it was manufactured. Many speakers are rebuilt in the UK and there are companies that just specialize in refits. It may also be possible to source the Monocor unit in the US or Canada; try Solen in Montreal, and Madisound in Madison Wisconsin.

Finally, the actual cone material used in the originals, in this case I believe it was polypropelene, has a definite bearing on the overall sound of the speaker unit, particularly in the mid-range where voice and most instruments are reproduced. It is very difficult to perfectly match both cone material and Thiel-Small parameters when the production of a given driver ends.

Cheers,
David Neice

the pair i have where made in canada same version


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PostPosted: Tue Dec 12, 2017 8:27 am 
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All is good in learning from this and taking the experience to the next level where you will probably start over again .No matter how much we learn you can never quit. With mistakes we gain wisdom. Keep on trying . They are not the cheapest nor the best. A good reference to gain some experience for the next project.


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PostPosted: Tue Dec 12, 2017 11:18 am 
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Location: hawkesbury, ON, CA
I would go with seas or vifa drivers very similar. after all those parameters monbo jumbo. if there was only one receipy to successfully implement a good match, if every company that uses drivers like, let say a p 17 seas woofer.would mean every company that uses that particular driver( and there is hundreds of company that did) they would ALL, have ended up, with the same axact size of boxes, and port dimension. (NOT). back in those days it was not as complicated ( replacing a woofer) as today. because now everybody use their computer programs( and there is a few dozen of them if not hundreds ) that by gods all mighty wisdom, are the only way to go. and yet they are still ending up with all kind of different size of cabinet , and loading , for the same drivers, just different approach.even with todays technics and calculation...
most speaker manufacturer, many times use the same woofer for 3 or 4 speaker model, and end up with 3 or 4 different cabinet size and loading.
all this to say that if you carefully choose a SIMILAR driver as what was used 9 efficiency, and qts, you should end up with very similar performance, and even superior performance can EASELY be achieved. just find a good match and enjoy the damn speaker.
specialist like solen and madisound can easely find a suitable replacement.


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PostPosted: Tue Dec 12, 2017 11:58 am 
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They still used complex equations back in the old days. This was the base of Thiele’s calculated alignments from back in the early 60’s. Small extended on Thiele’s work to which combined, came up with a predictable outcome for a set speaker design based on known calculations. From there the T/S parameters have become the industry standard for the past 40+ years. Computers just took over from graph paper and calculators.

There are may ways to tune a loudspeaker cabinet following TS parameters. One can select an equation to give a higher Qtc which may give the impression a speaker has more bass than it actually does (as an example).

Correct that companies may use the same driver across different models but a lot of the time that same driver is augmented with something else (dual drivers or changed from a bass mid to strictly a mid). There is a lot more to speaker design than just throwing a driver into a box.


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PostPosted: Tue Dec 12, 2017 12:24 pm 
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Location: Sarnia, ON, CA
Also had the same problems with Mission 717's. The driver is more square then round.
Put in a pair of full range drivers which Improved the sound.The reviews written by others swayed me this way.
I couldn't find the correct one.
Either Parts Source or Parts Express is where I bought them.
Good luck.


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PostPosted: Tue Dec 12, 2017 1:47 pm 
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sthomas1049 wrote:
They still used complex equations back in the old days. This was the base of Thiele’s calculated alignments from back in the early 60’s. Small extended on Thiele’s work to which combined, came up with a predictable outcome for a set speaker design based on known calculations.


True dat. Back in the day I tried to play Mad Scientist with a pair of Mission 710s'. I attempted to retrofit a pair of Mission 770 woofers into the 710 cabs. Managed to make them fit OK but epic fail nonetheless. The Frankenstein speakers didn't sound like a pair of 770s' and they actually sounded worse than the original 710s'. Lesson learned.

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PostPosted: Tue Dec 12, 2017 3:34 pm 
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Location: hawkesbury, ON, CA
for sure you cannot just trow in, just any driver.you have to carefully choose one. many people think that only that original driver will do a good job in that particular cabinet and xover. but that is a very normal 2 way speaker with easy to find same size of driver. there is at least a dozen of good drivers out there that will do a good job, in this cabinet( seas, vifa, peerless,scan speak). and probably MORE than half of them will do a better job than the original drivers. but your biggest problem right now is that not too many driver today are made with foam surround, most use rubber surround.
and repairing the original driver unless it is just foam surround, is a NO NO, by experience, I have never got satisfaction out of driver rebuilt with NON original parts. they never sound the same, and most likely will not last long.


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PostPosted: Tue Dec 12, 2017 4:09 pm 
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Not sure I understand the foam/rubber issue. Also do not understand your comment on never being satisfied with non original parts. Is that not the point of this discussion? Replace with original parts and not off the shelf drivers?

The cabinet and cross over was designed based on the T/S perimeters of the original driver. If it is a 6 inch driver, replacing it with an off the shelf driver of the same size will change the characteristics of both the cabinet and crossover. In others words, the speaker. The OP has gone through this experiment and did not like the outcome. Picking a random driver, regardless of quality or price is guess work at best. And not good guess work!

A link was provided above to show these speakers can still be found on the used market – and most likely cheaper than a pair of Sea’s or a Scan-Speak drivers.


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PostPosted: Tue Dec 12, 2017 4:55 pm 
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Crossover has to match the drivers.
Any change in drivers, modify the x-over.


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PostPosted: Tue Dec 12, 2017 5:14 pm 
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To add to this, the drivers are also most likely paired given their natural roll off with a crossover designed to filter above and below that roll off. Replacing that driver with a non original and modifying the crossover (assuming one possesses the skill) risks creating large peaks or drop offs within the crossover range.

As demonstrated in the link below, a crossover is designed by both mathematical equations and extensive measurements.

http://www.troelsgravesen.dk/crossovers.htm


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