Opinions plz on AR11 REBOX

[terry dactel]

Hi All

I'd like to introduce myself Paul from Sydney Australia.

I wish I'd found this place ages ago.I had a good look around the site last night,and thought this is place for me.

1st up brief a run down on my gear, modified Sony ps1 cd player, Luxman pd 264 tt AR ES-1 tt with Syrinx pu2 tone arm (currently rewiring arrrh), McIntosh C28 pre amp, McIntosh mc240 amp, and last but by no means least AR11 speakers.

A few years ago my neighbour gave me a set of Teledyne AR11's the cabinets were a little knocked around but presentable, I thought with a little clean up and some black paint to the front baffle plus a re foam job they should be ok when I get around to it.

About a year ago I re foamed the AR's and to cut a long story short, within a week the Wharfedale EVO 40's I'd had for a few years were now looking for a new home via ebay.

Now I'm ready to embark on the next stage, new cabinets.I've found my preferred optimum listening height for the speakers is approx 100mm off the floor.I have the opinion that a well set up pair bookshelf speakers have the same foot print as your typical floor stander. So why not make a set of floor standers using the AR11'S components and whilst I'm at it why not reconfigure the bass, mid, and tweeter vertically. Add some 12mm oak dowel cross bracing. That's easy part as I'm a carpenter by trade.

I'd also like to upgrade the crossover, but when it comes to the electronic side of DIY audio, I'm strictly monkey see monkey do, off the shelf type of guy so please forgive me with the choice of crossover.

Any and all opinions on my project would be welcomed. I've a few questions I'd like to ask the forum.

Q) Does the idea sound feasible, and has anyone here tried this already, if so how do they sound?

Q) Are there any benefits to using the crossover pictured below ?

Q) Given that the height of the speaker is going to increase in size by approximately 140mm how much should I decrease the depth of the speaker to retain the same air volume as the originals?

Thanks for dropping by Cheers Paul.

So here are a couple of sketches I've done up, the 1st sketch is how I'm proposing to reconfigure the cabinet.The 2nd is the original AR11 layout.

My link terry dactel AR11 Rebox

My LINK Original AR Layout

http://c1.ac-images.myspacecdn.com/images02/115/l_8d3942b12a0d4f21abdecde1be4a915c.jpg

3 Way Crossover - 12db 100W

- Crossover frequencies 700Hz, 3.5kHz

- 12db per octave roll off

- 100WRMS

- 8 Ohm

[deek]

[EDIT] I didn't take the driver re-arrangement into account...[/EDIT]

When resizing a cabinet, the volume has to stay the same (as you mentioned.) Here's the formula for that:

X1*Y1*Z1 = X2*Y2*Z2

1) Calculate the internal volume by multiplying the 3 inside dimensions. This will give you a measurement, in volume, of the airspace inside the cabinet. (X1*Y1*Z1)

2) Multiply the height and width of the internal dimensions of your new cabinet. This will give you a measurement, in area, of the baffle. (X2*Y2)

3) Solve for Z2 by dividing the product of 1 by the product of 2.

Example:

Old speaker has a width of 12", a height of 24" and a depth of 9.5"

The new speaker will have a baffle of 12" by 30". Solve for the depth by:

12*24*9.5=2,736 cubic inches of airspace in the cabinet.

12*30 = 360 square inches of baffle area.

2,736/360 = 7.6

The internal depth of the new speaker should be 7.6 inches.

-deek

[soundminded]

Hi All

I'd like to introduce myself Paul from Sydney Australia.

I wish I'd found this place ages ago.I had a good look around the site last night,and thought this is place for me.

1st up brief a run down on my gear, modified Sony ps1 cd player, Luxman pd 264 tt AR ES-1 tt with Syrinx pu2 tone arm (currently rewiring arrrh), McIntosh C28 pre amp, McIntosh mc240 amp, and last but by no means least AR11 speakers.

A few years ago my neighbour gave me a set of Teledyne AR11's the cabinets were a little knocked around but presentable, I thought with a little clean up and some black paint to the front baffle plus a re foam job they should be ok when I get around to it.

About a year ago I re foamed the AR's and to cut a long story short, within a week the Wharfedale EVO 40's I'd had for a few years were now looking for a new home via ebay.

Now I'm ready to embark on the next stage, new cabinets.I've found my preferred optimum listening height for the speakers is approx 100mm off the floor.I have the opinion that a well set up pair bookshelf speakers have the same foot print as your typical floor stander. So why not make a set of floor standers using the AR11'S components and whilst I'm at it why not reconfigure the bass, mid, and tweeter vertically. Add some 12mm oak dowel cross bracing. That's easy part as I'm a carpenter by trade.

I'd also like to upgrade the crossover, but when it comes to the electronic side of DIY audio, I'm strictly monkey see monkey do, off the shelf type of guy so please forgive me with the choice of crossover.

Any and all opinions on my project would be welcomed. I've a few questions I'd like to ask the forum.

Q) Does the idea sound feasible, and has anyone here tried this already, if so how do they sound?

Q) Are there any benefits to using the crossover pictured below ?

Q) Given that the height of the speaker is going to increase in size by approximately 140mm how much should I decrease the depth of the speaker to retain the same air volume as the originals?

Thanks for dropping by Cheers Paul.

So here are a couple of sketches I've done up, the 1st sketch is how I'm proposing to reconfigure the cabinet.The 2nd is the original AR11 layout.

My link terry dactel AR11 Rebox

My LINK Original AR Layout

http://c1.ac-images.myspacecdn.com/images02/115/l_8d3942b12a0d4f21abdecde1be4a915c.jpg

3 Way Crossover - 12db 100W

- Crossover frequencies 700Hz, 3.5kHz

- 12db per octave roll off

- 100WRMS

- 8 Ohm

I wasn't aware that Teledyne had acquired Acoustic Research when AR11 was in production. I'm assuming you're talking about the three way 12" "bookshelf" speaker that's approximately 2 cubic feet that was the next evolutionary step after AR3a and that was manufactured at the same time as AR 10 pi in the early to mid 1970s.

The principle which the original inventer called an "acoustic suspension" design would more accurately have been described as a pneumatic suspension design. It is critical that the internal volume be exactly as the original, the amount of trapped air inside the box is part of the design. It is also critical that the box be air tight and rigid. The stuffing should be saved and reused in the exact amount as the original. The nature, number, and packing of the fibers in the stuffing controls the mechanical damping of the speaker/enclosure combination and will change if either the quantity or nature of the stuffing changes.

The crossover network design should not be changed. Not only will you change the sound of the speaker probably for the worse, inadvertently lowering the low crossover points of either the tweeter or the midrange would substantially increase the risk of damaging them by overdriving them at frequencies they are not designed to handle. Rebuild the existing crossover network by replacing the capacitors with the same values as the original design and cleaning potentiometers or switches until they work smoothly and have no dead spots.

Changing the physical arrangement of the drivers will also affect the sound. This is not a matter of risk of damage but merely a consequence of the geometry of the layout affecting at what frequencies and where in a room reinforcements and cancellations will occur where the drivers operate at the same frequencies. This effect is unavoidable in any multiway non coaxial design, AR's or anyone elses.

Good luck on your project. Please keep us informed of how it works out. There's always plenty of skilled help here to assist with any problems along the way.

[terry dactel]

[EDIT] I didn't take the driver re-arrangement into account...[/EDIT]

When resizing a cabinet, the volume has to stay the same (as you mentioned.) Here's the formula for that:

X1*Y1*Z1 = X2*Y2*Z2

1) Calculate the internal volume by multiplying the 3 inside dimensions. This will give you a measurement, in volume, of the airspace inside the cabinet. (X1*Y1*Z1)

2) Multiply the height and width of the internal dimensions of your new cabinet. This will give you a measurement, in area, of the baffle. (X2*Y2)

3) Solve for Z2 by dividing the product of 1 by the product of 2.

Example:

Old speaker has a width of 12", a height of 24" and a depth of 9.5"

The new speaker will have a baffle of 12" by 30". Solve for the depth by:

12*24*9.5=2,736 cubic inches of airspace in the cabinet.

12*30 = 360 square inches of baffle area.

2,736/360 = 7.6

The internal depth of the new speaker should be 7.6 inches.

-deek

Thanks for your quick reply.Whilst you were posting I was busy doing another sketch.

Thanks for the formula I'll convert that to metric, I've not used inches for 30 years. Its just to dam confusing now

My link the grey area is extra height

[terry dactel]

I wasn't aware that Teledyne had acquired Acoustic Research when AR11 was in production. I'm assuming you're talking about the three way 12" "bookshelf" speaker that's approximately 2 cubic feet that was the next evolutionary step after AR3a and that was manufactured at the same time as AR 10 pi in the early to mid 1970s.

They do look same as the AR3, I believe the AR3 had paper cones the AR11 have what appear to be poly carbon cones.

The principle which the original inventer called an "acoustic suspension" design would more accurately have been described as a pneumatic suspension design. It is critical that the internal volume be exactly as the original, the amount of trapped air inside the box is part of the design. It is also critical that the box be air tight and rigid. The stuffing should be saved and reused in the exact amount as the original. The nature, number, and packing of the fibers in the stuffing controls the mechanical damping of the speaker/enclosure combination and will change if either the quantity or nature of the stuffing changes.

Thank you for the tip I will make the cubic capacity to the original value.

The crossover network design should not be changed. Not only will you change the sound of the speaker probably for the worse, inadvertently lowering the low crossover points of either the tweeter or the midrange would substantially increase the risk of damaging them by overdriving them at frequencies they are not designed to handle. Rebuild the existing crossover network by replacing the capacitors with the same values as the original design and cleaning potentiometers or switches until they work smoothly and have no dead spots.

Very good point, the crossover's are working fine so maybe I'm best off leaving well enough alone.

Changing the physical arrangement of the drivers will also affect the sound. This is not a matter of risk of damage but merely a consequence of the geometry of the layout affecting at what frequencies and where in a room reinforcements and cancellations will occur where the drivers operate at the same frequencies. This effect is unavoidable in any multiway non coaxial design, AR's or anyone elses.

Whilst I agree with you. I've got nothing much to lose apart from a few sheets of ply and an afternoon in the workshop, and maybe every thing to gain by reconfiguring the mids and tweeters.If it doesn't work out then I can always put them back in the original cabinets.

Good luck on your project. Please keep us informed of how it works out. There's always plenty of skilled help here to assist with any problems along the way.

Thanks for the well wishes look forward to posting the results.

[michiganpat]

IIRC teledyne bought them in the early 70's, while the 2ax,3a,etc were in production...

AR11 uses a paper cone, too...

keep the volume of the box the same, keep (or duplicate) the original crossovers (might be easier/better to keep the originals in the original boxes and just build new using the same values as the old). if you reuse the originals, replace any non-polar electrolytic capacitors in the crossover with like valued poly film caps.

[genek]

Teledyne acquired Acoustic Research in 1967.

[Pete B]

Hi All

I'd like to introduce myself Paul from Sydney Australia.

I wish I'd found this place ages ago.I had a good look around the site last night,and thought this is place for me.

1st up brief a run down on my gear, modified Sony ps1 cd player, Luxman pd 264 tt AR ES-1 tt with Syrinx pu2 tone arm (currently rewiring arrrh), McIntosh C28 pre amp, McIntosh mc240 amp, and last but by no means least AR11 speakers.

A few years ago my neighbour gave me a set of Teledyne AR11's the cabinets were a little knocked around but presentable, I thought with a little clean up and some black paint to the front baffle plus a re foam job they should be ok when I get around to it.

About a year ago I re foamed the AR's and to cut a long story short, within a week the Wharfedale EVO 40's I'd had for a few years were now looking for a new home via ebay.

Now I'm ready to embark on the next stage, new cabinets.I've found my preferred optimum listening height for the speakers is approx 100mm off the floor.I have the opinion that a well set up pair bookshelf speakers have the same foot print as your typical floor stander. So why not make a set of floor standers using the AR11'S components and whilst I'm at it why not reconfigure the bass, mid, and tweeter vertically. Add some 12mm oak dowel cross bracing. That's easy part as I'm a carpenter by trade.

I'd also like to upgrade the crossover, but when it comes to the electronic side of DIY audio, I'm strictly monkey see monkey do, off the shelf type of guy so please forgive me with the choice of crossover.

Any and all opinions on my project would be welcomed. I've a few questions I'd like to ask the forum.

Q) Does the idea sound feasible, and has anyone here tried this already, if so how do they sound?

Q) Are there any benefits to using the crossover pictured below ?

Q) Given that the height of the speaker is going to increase in size by approximately 140mm how much should I decrease the depth of the speaker to retain the same air volume as the originals?

Thanks for dropping by Cheers Paul.

So here are a couple of sketches I've done up, the 1st sketch is how I'm proposing to reconfigure the cabinet.The 2nd is the original AR11 layout.

My link terry dactel AR11 Rebox

My LINK Original AR Layout

http://c1.ac-images.myspacecdn.com/images02/115/l_8d3942b12a0d4f21abdecde1be4a915c.jpg

3 Way Crossover - 12db 100W

- Crossover frequencies 700Hz, 3.5kHz

- 12db per octave roll off

- 100WRMS

- 8 Ohm

I suggest that you just build your box and not worry about the extra volume.

You will get a lower Fc and slightly lower box Q, however the effect is

square law so small changes in volume do not have a large effect. You can

always reduce the volume by gluing in styrofoam blocks as needed. Certainly

reduce the depth a bit if you prefer the smaller box. You could also add a

few shelf braces for added strength.

Use the original crossover and replace all the capacitors. Measure and

replace any resistors that are out of spec. Do not use a generic crossover.

Nice project ... enjoy!

[deek]

Thanks for your quick reply.Whilst you were posting I was busy doing another sketch.

Thanks for the formula I'll convert that to metric, I've not used inches for 30 years. Its just to dam confusing now

My link the grey area is extra height

How many furlongs in a nautical mile again?

Looks like a great project! Keep us posted.

-deek

[terry dactel]

The consensus so far seems to overwhelmingly be if favour of keeping air volume as is and the crossover's in tact.

Replacing the caps and resistor's out of spec, this is not a job for me its outsource time, the natural born enemy of the DIYer

I do like Pete B's idea of not worrying to much about the air volume, at the 1st build and sound check stage. It's practical, potentially time saving, and less effort, the allies of the time pressed carpenter . As he suggests, I can always correct this later on, if they sound like a dud.

I'm leaning toward using mdf for the build.

Thank you all for your interest and input its much appreciated.Cheers Paul.

[Pete B]

I"m not sure how hard it is to get the crossover board out of those boxes,

but if you knock them out you might find that the soldering job is not so

bad. Certainly you can learn to solder if you do not already. Take

pictures as you go and it should not be difficult at all or just do one

at a time and use the other as a reference. These are big easy to solder

connections, just be sure to use an iron with enough power to heat them up.

[terry dactel]

I"m not sure how hard it is to get the crossover board out of those boxes,

but if you knock them out you might find that the soldering job is not so

bad. Certainly you can learn to solder if you do not already. Take

pictures as you go and it should not be difficult at all or just do one

at a time and use the other as a reference. These are big easy to solder

connections, just be sure to use an iron with enough power to heat them up.

Pete B

Soldering as you say is not to difficult, I've mastered that. Getting correct caps and resistors in the correct place with the correct values are tad more difficult.

[terry dactel]

opps double post

[soundminded]

Pete B

Soldering as you say is not to difficult, I've mastered that. Getting correct caps and resistors in the correct place with the correct values are tad more difficult.

Soldering correctly is a skill that can be easily acquired but it does need some practice and instruction. There are many excellent one or two sheet instructions with good suggestions. Practice on spare wire and acquire the skill before you try it on your project. Make your mistakes where it won't matter. If you have to solder directly to the midrange and especially the tweeter terminals, use a small soldering iron. One that's too large can melt the small wires in the speaker. I know from personal experience. Fortunately they were very cheap ones. clean the tip of the iron and solder it first but apply the solder to the work, not the iron when you solder. The solder will flow towards the iron. Use an iron that is hot enough to get the job done quickly. The results should look shiny bright and continuous with the wire or the terminal. A cold solder joint is unreliable and will fail.

If you give this project to someone else to do, find someone who is highly skilled and long experienced at speaker repair or building. Damage to the drivers, especially the tweeter and midrange will make it very difficult or impossible to be successful, these components are very hard to come by now.

I must disagree with Pete about the volume of the box. The amount of air trapped inside determines the springiness of the restoring force on the cone in this design. It will affect the F3 (system resonant frequency) and the system damping. The goal of the original design was to get the lowest system resonant frequency with the flattest response. The volume of air in this design which was probably determined originally by experimentation is matched to the characteristics of the driver and the amount and characteristics of the stuffing. It gives the best results.

By changing any of the factors of the original desgn, you will not have the same speaker. How it deviates and to what degree will depend on the changes you make. IMO you should not try to alter the design any more than you have to until you have far more experience and are willing to accept the possibility that the changes you make will not be to your liking. The original design was not arrived at haphazardly, it was the result of long hard work by the most knowledgable and inventive people in this industry at the time it was created. Don't take as your first effort trying to be smarter than they were.

[Steve F]

The consensus so far seems to overwhelmingly be if favour of keeping air volume as is and the crossover's in tact.

Replacing the caps and resistor's out of spec, this is not a job for me its outsource time, the natural born enemy of the DIYer

I do like Pete B's idea of not worrying to much about the air volume, at the 1st build and sound check stage. It's practical, potentially time saving, and less effort, the allies of the time pressed carpenter . As he suggests, I can always correct this later on, if they sound like a dud.

I'm leaning toward using mdf for the build.

Thank you all for your interest and input its much appreciated.Cheers Paul.

Here's a suggestion that might make your choice of cabinet dimensions a bit easier: Build a false 'base' into the cabinet. In other words, use a solid internal 'shelf' to separate the cabinet into two internal sections. The top section would be the exact same air volume as the AR-11, so no guesswork or finger-crossing would be needed for that.

The bottom section could then be whatever size/height you deemed necessary to meet your cosmetic requirements. But from the outside, it would appear as one cabinet, so your goal of a "floorstanding" AR-11 could be easily met.

Steve F.

[mluong303]

Since AR already did all the calculation and optimized the performance and came out with the AR91(floor standing) and AR-58s(compact which required stand to sit on), why not just choose the design you prefer and follow through the actual dimension of either one?

For the taller AR91 cabinet, AR added a 3/4" x 1-3/4" center brace from front baffle( at between the midrange and woofer) to the back baffle to strengthen the cabinet.

Minh Luong

[Robert_S]

Hello,

Rather than the AR-91, I'd suggest the AR-915 as a basis for your design. The cabinet lacks the (to my mind, idiosyncratic) beveled edge of the AR-91, thereby simplifying construction.

If the notion is of interest, you'll find detailed drawings in the library relating to the AR-915 Cabinet.

www.classicspeakerpages.net/library/acoustic_research/special_sections/drawings/SpeakerDrawings.swf

Scroll down the page, 75% or so, and download the four files referenced below (note that these files are incorrectly indexed as pertaining to the AR-91):

All being well, you should be looking at:

AR-Drawing-387, -388, -389, and -390.

The files are fairly high-resolution tiffs, and may require an appropriate application to render/display correctly.

Robert_S

[terry dactel]

To everyone who's shown and interest in the project, and taken their time to post advice, you've been a great sounding board thank you.

The cone's to my eye's don't appear to be paper maybe a paper composite.

Here are latest developments in the project. I floated the idea at GTG over the weekend, to some very experienced professional audio technician's and very talented Diyer's. One of whom had resently finished recapping a set AR3 for one of his clients.Theses guy's have forgotten more about audio than I'll ever hope to know.

I've been offered help with crossover side of the project, I do the crossover work with someone looking over my shoulder, I'd like to do this at my next GTG, I fully expect to be the butt of all jokes on the day but that's part the fun.

Soundminded, I apologise if I came off sounding like I'm an arrogant know it all that thinks he can do it do better than the original designers of AR11. Mate that's not where I coming from, I'll settle for naive newbie

Its basically a "what if" I done this project. As mentioned in a previous post I'm a carpenter by trade, I've got the equipment to build the cabinets, plenty of left over mdf and all it's going to cost me is an afternoon in the workshop.

If it works then great. If it doesn't, at very least I can say I've tested the theory for myself and it doesn't work.If not then I can build a set new set of cabinets to the exact dimensions of the original AR11.

My neighbour gave me the speakers he'd them stored in his children's rumpus room,for last 20 + year's and only used them as party speakers, as result the cabinets are looking a little worse for wear and tear.

The last picture after re foaming shows how the cabinets have suffered over the years.

[RoyC]

The cone's to my eye's don't appear to be paper maybe a paper composite.

Nice re-foam job, Terry.

Your woofers are not original AR-11 woofers. They appear to be the woofer AR used in later (TSW) models in the 1980's...which, incidentally, had larger cabinet volumes! It also had different response characteristics than the original AR-11 woofer, so there is absolutely no need to worry about building a slightly larger cabinet. It may actually be beneficial.

Roy

[terry dactel]

Mluong 303, RobertS and RoyC Good call on the TWS and 915 and 91 after a google search they appear to all use the same drivers.

The question begs the answer. I've original AR11 cabinets, tweets and mids, with a TWS drivers using original AR11 crossovers,what next as far as the crossovers go.

I'd still like to stick to my original plan as shown in my sketches.

[mluong303]

To everyone who's shown and interest in the project, and taken their time to post advice, you've been a great sounding board thank you.

Its basically a "what if" I done this project. As mentioned in a previous post I'm a carpenter by trade, I've got the equipment to build the cabinets, plenty of left over mdf and all it's going to cost me is an afternoon in the workshop.

Hi Terry

The AR TSW-610 and AR-58BXi used only 3/4" MDF with vinyl covering(black / walnut finish). 1" MDF would be a better choice for sturdiness. I would suggest center bracing your floor standing cabinets as picture shown. Good Luck on your project and by the way American Walnut veneer with lacquer coatings would look best on AR speaker cabinets.

Minh Luong

[terry dactel]

Hi Terry

The AR TSW-610 and AR-58BXi used only 3/4" MDF with vinyl covering(black / walnut finish). 1" MDF would be a better choice for sturdiness. I would suggest center bracing your floor standing cabinets as picture shown. Good Luck on your project and by the way American Walnut veneer with lacquer coatings would look best on AR speaker cabinets.

Minh Luong

Yep will definitely using centre bracing thanks for the tip I'm thinking of embossed black western or black embossed pasley tolex with the front baffle in matt black spray painted.

Cheers Paul