Hi. I just picked up a pair of the famous (infamous) 1980 "Fourier 1" speakers for $25. These speakers feature solid mahogany boxes. They were well reviewed in their day and sold for $1100 each.
Unfortunately, the drivers (10" woofers, mids, and probably the tweeters) are shot and need to be replaced. I'm can't find information about the design. So what I'm left with are some nice boxes with stuffing and crossovers that certainly look nice, with no data on which to base my driver replacement choices, and I'm really not a speaker design guy.
So my challenge is -- without really knowing what I'm doing -- to learn (from you I hope!) whether it's possible to reverse engineer the design enough to make reasonable choices for new drivers?
Any advice? I'm a technically capable person but I'm not knowledgable about speaker design, per se.
Kind regards,
Kevin Sullivan
Unfortunately, the drivers (10" woofers, mids, and probably the tweeters) are shot and need to be replaced. I'm can't find information about the design. So what I'm left with are some nice boxes with stuffing and crossovers that certainly look nice, with no data on which to base my driver replacement choices, and I'm really not a speaker design guy.
So my challenge is -- without really knowing what I'm doing -- to learn (from you I hope!) whether it's possible to reverse engineer the design enough to make reasonable choices for new drivers?
Any advice? I'm a technically capable person but I'm not knowledgable about speaker design, per se.
Kind regards,
Kevin Sullivan
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I would suggest to get a program like BOXPLOT that will allow you to select a driver, enter in the parameters, and see if the results would work with the box dimensions that you have.
If it does not match, select another driver and try again.
Sort of reverse engineering.
Or post the inner dims of the boxes and some of the more knowledgeable members here could recommend a few choices that you could start to look at.
Have fun and don't rush.
If it does not match, select another driver and try again.
Sort of reverse engineering.
Or post the inner dims of the boxes and some of the more knowledgeable members here could recommend a few choices that you could start to look at.
Have fun and don't rush.
Just Googled photo of the speakers and I am willing to bet that the tweeter is a 1" Audax soft dome. These were "the bee's roller skates" in the mid to late '70's in the UK and seemed to be in every second top end speaker sold there.
Something very similar could still be bought. They had 91dB/w/mtr sensitivity. Resonance around 900c/s I recall and crossed over anywhere from about 2.5kHz up. Often a 3rd order network.
Couldn't guess the others.
Are there notations on the back of the drivers?
Thought of getting the originals repaired?
Cheers Jonathan
Something very similar could still be bought. They had 91dB/w/mtr sensitivity. Resonance around 900c/s I recall and crossed over anywhere from about 2.5kHz up. Often a 3rd order network.
Couldn't guess the others.
Are there notations on the back of the drivers?
Thought of getting the originals repaired?
Cheers Jonathan
Hi Kevin,
Let's be positive about this. You are not limited by the existing port size. That can be changed to suit the new driver/box combination. So that's one fixed item that is now a controllable variable. (For that matter it could end up a sealed enclosure too).
You're obviously no fool. It wouldn't take too long to read up on speakers. Stacks on the web.
Cross overs can be "cannibalised" and probably should be. By that I mean the capacitors will probably be electrolytics and may be dried out by now. Plenty on new and better quality ones around these days. New drives will require new values for the cross over (usually) and that, again, can be worked out. Coils (inductors) are pretty much indestructible so they can be recycled....Need to determine existing values but that's not impossible.
You do have a challenge, but a good one. Nice shiny, solid cabinets are a good place to start assuming you like the aesthetics which presumably you do as you bought them in the first place...
Which you DO I see (just re-read your first post, doh!).
Good luck. I am sure a number of people here will gladly co-operate in this venture.
Cheers, Jonathan
Let's be positive about this. You are not limited by the existing port size. That can be changed to suit the new driver/box combination. So that's one fixed item that is now a controllable variable. (For that matter it could end up a sealed enclosure too).
You're obviously no fool. It wouldn't take too long to read up on speakers. Stacks on the web.
Cross overs can be "cannibalised" and probably should be. By that I mean the capacitors will probably be electrolytics and may be dried out by now. Plenty on new and better quality ones around these days. New drives will require new values for the cross over (usually) and that, again, can be worked out. Coils (inductors) are pretty much indestructible so they can be recycled....Need to determine existing values but that's not impossible.
You do have a challenge, but a good one. Nice shiny, solid cabinets are a good place to start assuming you like the aesthetics which presumably you do as you bought them in the first place...
Which you DO I see (just re-read your first post, doh!).
Good luck. I am sure a number of people here will gladly co-operate in this venture.
Cheers, Jonathan
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You're actually spoiled for choice. Many in your position would not favour a bass reflex anyway. Depends what you are after. Sealed boxes are simpler. Do you wish to create "a very similitude" of the original CONCEPT or trying to achieve a really nice pair of domestic speakers irrespective of the acoustic theory behind them......?
Found a picture on the web at Fourier 1 Speakers Very Beautiful and Very Rare Photo - Canuck Audio Mart
It looks like the drivers were:
Audax 1" dome tweeter, as previous poster noted about 90dB sensitivity, fs about 900 Hz, 8 ohm nominal, could probably replace it with
Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter 275-070
A better option may be:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=264-1040
but you'll have to add a 2ohm or 2.5ohm resistor in series with it for it to approximate the efficiency and impedance of the original tweeter.
Midrange
Looks like old Peerless 4" midrange (probably in a sealed mounting cup) w. flat surround, about 90dB sensitivity, 8 ohms, this one's going to be hard to find an exact match, but one TangBand unit may be a good, albeit pricey choice, similar extension, efficiency and impedance, and in fact it is a much, much better quality midrange driver, really impressive transparency, this would be a huge upgrade over the original. You may have to use a long 4" diameter tube behind it, and fill it with stuffing. It may be better if you can get the tube to go all the way through the back of the box.
Tang Band W4-1805S 4" Neodymium Midrange Driver 264-890
Woofer
Peerless (old Peerless germany) woofer. It's the 10", and probably has fs of about 25Hz, Qtc about 0.4, sensitivity 88 or 89dB or so. This unit could be a suitable replacement, may not need to adjust the port:
Dayton Audio DS270-8 10" Designer Series Woofer 295-432
or maybe this one (but may need port adjustment)
Peerless 830668 10" Paper Cone SLS Subwoofer 264-1110
Definitely plan on replacing the capacitors, I recommend the Dayton Polypropylenes.
Personally, I would redo the entire crossover to optimize for the new drivers, but that's a whole different level of work. The driver options I've suggested would probably work fairly well as drop-ins without needing to change the original crossover values much if at all.
Good luck with the project.
It looks like the drivers were:
Audax 1" dome tweeter, as previous poster noted about 90dB sensitivity, fs about 900 Hz, 8 ohm nominal, could probably replace it with
Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter 275-070
A better option may be:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=264-1040
but you'll have to add a 2ohm or 2.5ohm resistor in series with it for it to approximate the efficiency and impedance of the original tweeter.
Midrange
Looks like old Peerless 4" midrange (probably in a sealed mounting cup) w. flat surround, about 90dB sensitivity, 8 ohms, this one's going to be hard to find an exact match, but one TangBand unit may be a good, albeit pricey choice, similar extension, efficiency and impedance, and in fact it is a much, much better quality midrange driver, really impressive transparency, this would be a huge upgrade over the original. You may have to use a long 4" diameter tube behind it, and fill it with stuffing. It may be better if you can get the tube to go all the way through the back of the box.
Tang Band W4-1805S 4" Neodymium Midrange Driver 264-890
Woofer
Peerless (old Peerless germany) woofer. It's the 10", and probably has fs of about 25Hz, Qtc about 0.4, sensitivity 88 or 89dB or so. This unit could be a suitable replacement, may not need to adjust the port:
Dayton Audio DS270-8 10" Designer Series Woofer 295-432
or maybe this one (but may need port adjustment)
Peerless 830668 10" Paper Cone SLS Subwoofer 264-1110
Definitely plan on replacing the capacitors, I recommend the Dayton Polypropylenes.
Personally, I would redo the entire crossover to optimize for the new drivers, but that's a whole different level of work. The driver options I've suggested would probably work fairly well as drop-ins without needing to change the original crossover values much if at all.
Good luck with the project.
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Looks like a nice project.
What, particularly, is wrong with the drivers? Have you considered getting them repaired?
Doug, Jack, et al.,
Thanks very much for your responses. They're very helpful. To further the discussion I'm attaching some detailed pictures: of the boxes, the condition of the drivers (the surrounds on the woofers look like something from Andromeda Strain -- mostly gone and what's left is crispy), crossover, and identifying marks on and pictures of the drivers.
The boxes are 38 1/2" H X 16" W X 11 3/8" D exterior, and the wood (at least on the front) is 7/8". Assuming it's the same thickness all around (I have not unstuffed the boxes), that'd make the interior dimensions
36 3/4 X 14 1/4 X 9 5/8 = 5040 in^3 = 2.9 ft^3, i.e., about 3 ft^3.
The port is 4" diameter and 6.5" from the back to the face of the speaker.
As for what I'm looking for ... I'd like to get the best sound possible from the speakers (not necessarily optimizing to replicate their original sound) without doing a whole lot of work and without spending a fortune.
I understand that old caps probably ought to be replaced, but if I could get upgrade these and get some mileage while saving the crossover upgrade for some future time, that'd be great -- thus my desire to have some sense of (rough) compatibility of the original and "near drop-in" replacement drivers.
I really appreciate the help all you folks have already provided. If there is anything else I can tell you or show you, let me know.
Kind regards,
Kevin
Attachments
Hi,
Classic mid unit and treble unit from the period.
Bass unit has a humungous magnet for the period.
Refoaming the Peerless bass drivers should't be a problem.
Equivalent new drivers would be expensive.
The Peerless mid units have poked in dust caps which can
be sucked back out, are you sure that they don't work ?
(Its the coated version, apparently two coats.)
The tweeters are the ubiquitous Audax.
The crossovers do not need changing, they look fine.
Have you individually checked all the drivers to see if they work ?
(use a multi meter to measure the voice coil resistance).
It shouldn't be a problem finding near equivalent mids and treble.
You really need to repair the bass units though.
rgds, sreten.
Classic mid unit and treble unit from the period.
Bass unit has a humungous magnet for the period.
Refoaming the Peerless bass drivers should't be a problem.
Equivalent new drivers would be expensive.
The Peerless mid units have poked in dust caps which can
be sucked back out, are you sure that they don't work ?
(Its the coated version, apparently two coats.)
The tweeters are the ubiquitous Audax.
The crossovers do not need changing, they look fine.
Have you individually checked all the drivers to see if they work ?
(use a multi meter to measure the voice coil resistance).
It shouldn't be a problem finding near equivalent mids and treble.
You really need to repair the bass units though.
rgds, sreten.
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Sreten, Thanks a ton. As I said, I'm not knowledgeable about speaker repair. But now, thank to you, I know I can refoam the darn woofers. I didn't know that before! So, I plan to fire up the things, test the drivers, and if lucky, all I'll have to do is glue on some new surrounds. I watched a video on PartsExp and there's nothing to it. *Thanks*
Kevin
Hello Kevin,
Driver info is given by the pictures: tweeter is the Audax HD 12x9, midrange is not a Peerless, but also Audax, type MHD 12. The woofer seems an American product and not a Peerless, maybe Carbonneau or the guys that produced the woofers for Madisound and AC in the 80ties.
If you accurately measure the cone outside and frame inside diameter including the frame width on which the surround is glued, it should be simple to obtain a new surround.
Look on Youtube for refoaming: with the proper surround and glue it is a piece of cake. There is no need to even know the type or brand of the woofer if you know the proper dimensions for the surround, which can easily be measured
For a handful of bucks you should be in business.
Good Luck!
Eelco
Driver info is given by the pictures: tweeter is the Audax HD 12x9, midrange is not a Peerless, but also Audax, type MHD 12. The woofer seems an American product and not a Peerless, maybe Carbonneau or the guys that produced the woofers for Madisound and AC in the 80ties.
If you accurately measure the cone outside and frame inside diameter including the frame width on which the surround is glued, it should be simple to obtain a new surround.
Look on Youtube for refoaming: with the proper surround and glue it is a piece of cake. There is no need to even know the type or brand of the woofer if you know the proper dimensions for the surround, which can easily be measured
For a handful of bucks you should be in business.
Good Luck!
Eelco
These people sell Audax drivers, you might find replacements for any dead ones but they are in the UK:
Falcon Acoustics | The Leading DIY Speaker Parts and Kit Supplier since 1972
Falcon Acoustics | The Leading DIY Speaker Parts and Kit Supplier since 1972
Thanks. Having learned I can at least test the speakers even without the woofer surrounds, I've now run the speakers. The woofers and mids speak. The tweets don't.
Is this problem "almost certainly" in the tweeters themselves--i.e., should I order replacements--or is there a meaningful chance the problem's elsewhere, e.g., in the crossovers?
Thanks again for your help with this weekend project,
Kevin
The tweeters
So the original Audax 9x12 apparently had a resonant frequency of 800Hz. The current version of the "same" item (available in the US, e.g., at Madisound) has a resonant frequency of 1200Hz. That's a pretty big difference. Does anyone have a good sense whether this difference is likely to present a problem or not?
So the original Audax 9x12 apparently had a resonant frequency of 800Hz. The current version of the "same" item (available in the US, e.g., at Madisound) has a resonant frequency of 1200Hz. That's a pretty big difference. Does anyone have a good sense whether this difference is likely to present a problem or not?
I still have some of the Audax tweeters.
The driver (tweeter-mid) spacing on this design is odd.
As Boden points out the woofer is USA made.
From the picture of the midrange rebate, it looks to me like these cabs are particle board with veneer.
What i would do with these is refoam the woofers -- that keeps the woofer alignment similar (as with most vented boxes of this generation, i'd likely end up putting a porous foam bung in the port). I would then fit a piece of 4" PVC pipe behind the midrange cutout and run it all the way to the back of the cabinet and load it with a nice 3" FR -- the Fostex FF85wk is my current favorite for this kind of application -- choice might be somewhat dictated by relative sensitivity differences between FR & the existing woofer, with FF85 88-90 dB would be good for the woofer. The XO would need to be reworked (a PPLXO and bi-amping is an option, and cheaper if you have a spare amp kicking about, and eliminates any issues with relative sensitivity of the 2 drivers) with XO point near the baffle step. The tweeter can be left to fill the hole there (but disconnected) or you could make a new plate to fill the hole.
dave
The driver (tweeter-mid) spacing on this design is odd.
As Boden points out the woofer is USA made.
From the picture of the midrange rebate, it looks to me like these cabs are particle board with veneer.
What i would do with these is refoam the woofers -- that keeps the woofer alignment similar (as with most vented boxes of this generation, i'd likely end up putting a porous foam bung in the port). I would then fit a piece of 4" PVC pipe behind the midrange cutout and run it all the way to the back of the cabinet and load it with a nice 3" FR -- the Fostex FF85wk is my current favorite for this kind of application -- choice might be somewhat dictated by relative sensitivity differences between FR & the existing woofer, with FF85 88-90 dB would be good for the woofer. The XO would need to be reworked (a PPLXO and bi-amping is an option, and cheaper if you have a spare amp kicking about, and eliminates any issues with relative sensitivity of the 2 drivers) with XO point near the baffle step. The tweeter can be left to fill the hole there (but disconnected) or you could make a new plate to fill the hole.
dave
Hi Kevin. Thanks for the photos, "tres" helpful. You "got lucky" with the cross overs. Those capacitors would appear to be plastic film types and they last a lot longer than 'electros' so they prob' don't need replacing. It also speaks well for the quality of the original product. Tweeters; More likely they have failed than the cross over. If you can disconnect even just one lead from the xover to the driver and test for DC continuity across the tweeter that will give a definitive answer. Use a meter and check for resistance. It will either be around 6ohms or 3ohms (approx) depending on the nominal impedence which will usually be "8" or "4" ohms. My guess is that the difference in resonance is not a major issue but I couldn't swear to that.
You can buy standard foam surround replacement kits at a number of places. No issues there.
Edit: Dave posted while I was still typing.....sorry if my post not up to speed re tweeters.
You can buy standard foam surround replacement kits at a number of places. No issues there.
Edit: Dave posted while I was still typing.....sorry if my post not up to speed re tweeters.
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If you do decide to go with Dave's genuine Audax replacement tweeters you might consider a nice simple LCR compensation circuit that removes a peak at about 13kHz. Takes some of the "tizz" out of what is usually regarded as a v. good unit. I think Spendor used them at one stage. But that is probably a bit of a way down the track and might come under the catergory "of guilding the lily".
Cheers, Jonathan
Cheers, Jonathan
Hi,
I was guessing with the bass unit make, recognised the
old midrange badge but misindentified it, fair enough.
If the mids are working then poked in dust caps are not
enough to warrant replacement and complete redesign
of the crossover, especially not knowing the basic bass
unit sensitivity.
The tweeters really aren't that good, (JB has alluded to
the typical problem), and a replacement is decent idea,
chosen on being able to use the original face plate.
New faceplates with the coil dome assembly are available
in the UK, but they cost as much as a modern tweeter.
Here is the modern version :
Madisound Speaker Store
With an authentically accurate treble rise, the question is does
the x/o compensate for this or not, you have to draw it out.
P10 is right about typical bass alignments, though I
prefer lining the ports with porous foam - say 1/2"
thick here - a rectangular piece port depth x 3 times
the diameter folded into the port to detune it and
tighten and extend the bass response.
rgds, sreten.
I was guessing with the bass unit make, recognised the
old midrange badge but misindentified it, fair enough.
If the mids are working then poked in dust caps are not
enough to warrant replacement and complete redesign
of the crossover, especially not knowing the basic bass
unit sensitivity.
The tweeters really aren't that good, (JB has alluded to
the typical problem), and a replacement is decent idea,
chosen on being able to use the original face plate.
New faceplates with the coil dome assembly are available
in the UK, but they cost as much as a modern tweeter.
Here is the modern version :
Madisound Speaker Store
With an authentically accurate treble rise, the question is does
the x/o compensate for this or not, you have to draw it out.
P10 is right about typical bass alignments, though I
prefer lining the ports with porous foam - say 1/2"
thick here - a rectangular piece port depth x 3 times
the diameter folded into the port to detune it and
tighten and extend the bass response.
rgds, sreten.
Followup on Fourier 1 rebuild
Hi Jonathan and all,
Can't tell you how much I appreciate all your help. So here's what I did. On the advice of people here, of Peter Aczel of Audio Critic and Fourier 1 fame, and of a gentleman from the UK who sells Audax, I decided to rebuild the speakers to their original specs/voicing by avoiding mods and by just having the mids and woofers repaired. I shipped them to a guy Peter recommended to be refoamed. At $110 for the whole job plus shipping, it was a no-brainer. They arrived at the guy's shop late last week. I should have them back around Oct 1. As for tweeters, I bought and will drop new Audax 9X12s. They're not exact replicas of the originals, but they're very close and will surely do just fine. I'll let you'all know how they turn out in about two weeks.
Thanks again! Great community here.
Hi Jonathan and all,
Can't tell you how much I appreciate all your help. So here's what I did. On the advice of people here, of Peter Aczel of Audio Critic and Fourier 1 fame, and of a gentleman from the UK who sells Audax, I decided to rebuild the speakers to their original specs/voicing by avoiding mods and by just having the mids and woofers repaired. I shipped them to a guy Peter recommended to be refoamed. At $110 for the whole job plus shipping, it was a no-brainer. They arrived at the guy's shop late last week. I should have them back around Oct 1. As for tweeters, I bought and will drop new Audax 9X12s. They're not exact replicas of the originals, but they're very close and will surely do just fine. I'll let you'all know how they turn out in about two weeks.
Thanks again! Great community here.
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