Info on The Advent/1 re-foam.

[Shoedog]

Howdy- I am doing my first re foam job on a pair of The Advent/1 speakers and I have the following questions- 
1. The woofers are of different vintage- one has been re-foamed already and has a round magnet, while the other has a square magnet and I have started to remove the foam. Can anyone tell me which is the original and which vintage or model the other is? I may want to find a match to whichever is correct. 
2.The foam is attached to the bottom of the cone on the square magnet one- is that the way it should be done when I replace the foam? or can it be glued to the top of the cone? 
3. They have silicone type glue on them- Is that something that should be used? I have just started to learn this process and I haven't seen silicone glue/adhesive mentioned in any of the guides I have read or how to videos I have watched. 

Also- On the woofer that has already (apparently) been re-foamed- it has a scratch or buzz sound when played. If I touch the sides of the surround slightly and move the speaker center, the noise dissipates. It seems to me that the speaker works properly. Does that mean that the re-foam job was not centered properly? If that is the issue- I assume that their is no way to fix without a new re-foam? Again- thanks for any info/help on the issue.

Another question comes to mind- Is their any problem running them with the different woofers?

Thanks- I recently came into a nice variety of quality speakers that all need foamed- I hope to bring them all back to life.     Shoedog 

[Pete B]

The square magnet version is the correct one, the round one was manufactured by Jensen 

after they bought Advent and is the correct woofer for the 5002/5012.  They are very similar

but the magnet geometry is different.  I'd get a matching woofer if you don't mind spending a 

few bucks.

There are several goals when doing a refoam:

1.  Center the voice coil in the horizontal plane, luckily if you visually center the foam on the

cone and put it back on the frame where the original one was it has worked every time.

2.  Center the voice coil in the vertical plane, you want the VC centered in the gap for maximum

motor strength.  Install the foam the same way as the old foam was done.  1/16" makes a 

difference.

Also, measure the distance from the edge of the frame to the old foams position and put the 

new foam at the same "level" on the frame.   

3.  The dust cap radiates some midrange and changing it will alter the frequency response of

the woofer in the critical midrange.  Do not cut and shim, keep the original dust cap.

 

I and many, many others use Alene's Tacky glue available at Walmart and craft stores it just 

works very well giving you time to adjust if needed.

How I do an Advent refoam:

1.  Clean off the old foam and glue - for years I did this with the tip of a flat blade screw driver but I

found that the tiny wire brush on a Dremel tool works great, Gently at a slow speed.  Face the

woofer down on a flat work surface if you need to get to the back of the cone or work from the

front if possible.

2.  Put rolled up plastic shopping bags in the back between the frame and the cone to lift it up for

easier access.  Anything will work, crumpled up newspaper, etc.

3.  Squirt some glue into a bottle cap and use a tiny paint brush or Q-tip to apply glue to the inner 

lip of the foam, once I go around it usually soaks in:

4.   Apply another light coat.   Then press it against the cone.  If you want to move more slowly you

can apply say 2" of the second coat press that section to the cone, another 2" press, and work your

way around.  Stay with it after you finish and apply pressure until it sets up - let it dry for a few hours

or over night.

5.  Apply glue to the outer lip one coat, then remove the plastic bags and let the cone drop now

lift the edge and apply a second light coat of glue and align/press the foam according to the old glue 

line and/or your measurements.  Try to move fast so that the glue does not fully setup.

6.  Apply even pressure to the cone with your thumb and finger tips to both sides of the cone and push

it in about 1/4", does it move without scraping?  Rotate 90 degrees and try again, if it is not free you 

need to adjust the lip of the foam for better centering.  Press on just one side to figure out which side

needs to move in or out while the glue is still not fully dry.

7.  Some drive the woofer with a very low frequency test tone to help center it but I've never had to do

this with an Advent woofer.

 

[Shoedog]

Thanks Pete B- I will look around for a second original woofer and re-faom the newer one of the two I have while I am doing the project. I bought a lot of quality speakers that all need ree-foamed and I am learning a lot from folks willing to help me out- it  is appreciated! 

[Pete B]

I am the author of this page, FYI:   http://baselaudiolab.com/ADVENT_LA_XO.html

This is my collection:   http://audiokarma.org/forums/index.php?threads/large-advent-collection-pete-basel.699453/

[Shoedog]

BONUS! In digging thru all the boxes from the garage full of electronics I bought, I found the other original speaker to the Advent/1!  I hooked it up and it seems to work fine- now I can re-foam both and see how it works. 

[Pete B]

Another note is that the Advent/1 uses the all metal woofer, the same as in the NLA.

This version has the inner lip of the foam glued to the BACK of the cone, always glue the 

new foam in the same way as the original.  Some claim that it doesn't matter and this is 

not true.

Also, note here how the outer edge should be placed:

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/2842-refoaming-new-advent-woofers-edge-height-details/

 

[Analogman]

The outer shape of the magnet makes NO DIFFERENCE

What matters with the magnet is gauss, meaning it's magnetic flux density (magnetic induction)

What DOES matter is orientation of pole piece, gap and distance to back plate (and where the VC's windings sit at rest)  

Klipsch (simply because they are a very good example of this) sold many many many replacement woofers that had square magnets whereas the woofers that came in the cabinets were originally round* (* possibly I have this vice versa, senior memory moment, haven't bought a replacement driver from Klipsch since P.W.K. was alive - all I know is that they did it with regularity)  I used to be a Klipsch hoarder 

They were, and are, electrically (and most importantly) FUNCTIONALLY/SONICALLY identical, all else being equal

As a matter of fact, I, until recently, owned (purchased by me) an all original untouched, one owner, bought NEW, pair of Cornwalls and one cab contained a square magnet woofer and the other a round - Klipsch (as most of them did) used what was on the assembly line until it was exhausted and then made the switch to the next batch/run of inventory of any given part # - and guess what?  I got the pair chronicling just that event as they were consecutively numbered grain matched boxes 

Sure, if one driver has a different MOTOR structure, or cone or voice coil then obviously there is and will be a difference, on several levels, but as for a "all things being equal" situation I will say it now for the tenth time

The SUPERFICIAL Shape Of The Magnet Makes No Difference Unless is just Happens to Occur on an entirely Different Transducer

What matters is the flux density

This is why manufacturers publish specs for their individual drivers and production changes in magnet shapes is/was extremely common back in the day

I would not rely simply on magnet shape in assuming a given transducer is an exact match for another driver

The only practical thing it's good for is as an aid to help identify and date some transducers - beyond that it means nothing

No speaker manufacturer "makes" any of the magnets they use and the choice of magnet used on any given design all depends on the vendor contracted to produce them

It might make some folks feel better to have matching pairs when it comes to magnet shape then so be it - but if the published PERFORMANCE parameters and the part number is correct the rest is all in your head

THE ONLY REASON SQUARE MAGNETS AND PLATES WERE/ARE USED IS BECAUSE THEY ARE CHEAPER AND EASIER TO MAKE - THAT'S IT - FULL STOP

Now the Alnico versus ceramic is another debate!

Craig

 

 

[Analogman]

http://www.humanspeakers.com/essays/square-magnet.htm

[Pete B]

You just don't seem to get it Analogman, even though I've stated it several times.  Yes we all

get that if you are designing a new woofer magnet round vs. square doesn't matter.  BUT, it 

turns out that all of the Kloss/Advent made woofers have square magnets with thicker top

and back plates, and all round magnet Advent woofers are from Jensen with thinner top

and back plates.  Again, the motor geometry is different and the VC wind height is probably

different.  So, I'll say it one more time, try to follow along, we use the square magnet to indicate

that a woofer was early Kloss/Advent production and round to indicate Jensen/Advent.  We

are NOT suggesting anything about the magnetic B field strength in the gap.

[Analogman]

Try actually reading my posts

Like the part(s) where I have said, SEVERAL TIMES - "all things being equal" about a dozen times now

I've also indicated (and acknowledged/agreed) more than once now that shape can be an aid in determining the vintage of a given driver (obviously)

I don't deal in "probably"

But I'll say it this more time:

MAGNET SHAPE MAKES ABSOLUTELY NO DIFFERENCE WITH REGARDS TO SONICS IF ALL OTHER PARAMETERS ARE EQUAL

PERIOD

IDENTICAL WOOFERS AS FOR PERFORMANCE WERE PRODUCED WITH BOTH - NOT JUST BY ADVENT

[Pete B]

That you make the comment in response to my posts should indicate that you are _trying_ to

make a relevant point , based on this last post it seems not.  All other parameters are NOT equal,

the top and back plate thickness is different.

[ra.ra]

12 hours ago, Analogman said:

PERIOD

With punctuation, this term usually indicates the end, and I hope that's the case here.

[Analogman]

The shape of the magnet on any given transducer makes absolutely no difference

That IS the point as well as a matter of fact

Pete B, you keep changing and qualifying and quantifying your insistence that it does

In the case of the woofers up for discussion here you have no evidence of your persistent claims other than pure speculation and the word "geometry" based entirely on your asumptions

Not a very technical or scientific approach

With all things being equal, the shape of a transducer's magnet MAKES NO DIFFERENCE

Your insistence in doing so is a disservice to members who for some reason have faith in what you say causing them to waste time tracking down worn out old drivers as well as giving rise to performance angst when what they have is perfectly suitable for the job (and system) at hand not to mention authorized factory replacements

All for the irrelevant shape of the magnet

[Pete B]

The motor geometry is certainly different based on the thicker top and back plates,

this impacts the large signal distortion and overload characteristics, they are certainly 

different.  It is clear that you don't even understand what they are since I had to explain

it to you.

As far as the small signal characteristics go, they are similar but since I've not measured

every important parameter I've not stated it one way or another.  I've said that they are 

very similar which is what I've observed in listening to them and through some measurements.

I've freely posted many measurements here, where are yours?  I have measured Fc and Qtc 

for the OLA, NLA, and Jensen 5002/12 on more than one sample of each and they are all close.

I actually have a spread sheet for calculating large signal performance based on the motor

geometry, and have entered the square magnet woofer data since I've removed a cone and

measured the VC.  I've not done this yet on a round magnet Jensen version but clearly they

will be different due to the top and back plate differences.  One has a bumped back plate the

other doesn't, they are obviously different.

I am very careful about how I word things on these forums due to the comments from a few

nut jobs like you.  I've said to go ahead and mix round and square but that it is better to have

the same type, this is my opinion based on my observations and measurements.

 

[Analogman]

I don't know why such a simple law of physics is so difficult for you to acknowledge

I have said now at least a dozen time now - ALL ELSE BEING EQUAL

THE SHAPE OF A TRANSDUCER'S MAGNET MAKES NO DIFFERENCE

Everything you speculate on can be as easily accomplished with a round magnet structure as a square

It's obvious that if two transducers are of entirely different designs then that is another subject altogether

Try reading Huw Howell's piece on the subject; I posted the link

I would think he and Winslow Burhoe would have a little more insight into the topic than you, no intent to damage your seemingly fragile ego

Unless you yourself are responsible for some of the most revolutionary designs in audio of which I am not aware (along with Henry Kloss and Arnie Nudell)?

Craig

 

[Pete B]

https://patents.google.com/patent/US6341166B1/en

I am also the author of the first T&S style analysis/simulation of transmission line loaded woofers,

tell us about YOUR scholarly papers.

 

You state the obvious as if we need to be educated when in fact it is you who missed

the top plate differences and actually need to be educated.  If the magnet structures

were the same then magnet shape would not matter, the fact is that the structures

are not the same - this is obvious.

 

So Craig, where are YOUR measurements?  Or do you just call it good enough and hope

for the best?  Put up, or shut up.

 

 

[ITCHIJO]

HEY SHOEDOG: AS A MARINE I AND MY BULLDOG SAY, HEY JUST TAKE IT TO "OEM" STATS, AND THEIR VALUE WILL BE INCREASED. JUST DO IT, AND THAT IS AN ORDER!!! BESIDES WHAT THE DISCUSSION IS HERE, YOU ARE MISSING OUT ON SOME REAL HEAVENLY TUNES. GET BUSY AND GET "JAMMIN" TOO YOUR ADVENTS, AND LOVIN EVERY MINUTE OF SWEET SOUL MUSIC!!! STAND AT ATTENTION WHEN THE STAR SPANGLED BANNER PLAYS!!! ENJOY, MY DIEHARD ADVENT BROTHER!!! "GRUNT ITCHIJO"

[Analogman]

10 hours ago, Pete B said:

https://patents.google.com/patent/US6341166B1/en

I am also the author of the first T&S style analysis/simulation of transmission line loaded woofers,

tell us about YOUR scholarly papers.

Hey, you're not the guy who gave us "stadium" night club" "arena" "Jazz" etc etc are you? (actually, Telefunken did that almost 60 years ago but in the Analog domain)

Never been a big fan of engineered tone controls, for a multitude of reasons - I enjoy the most the recordings from the "golden age" that got it right the first time (Van Gelder, Fine, Ludwig, Martin, Grundman and many many more too numerous to list all here)  People who could/can hear

And they did it all before the silicon chip (or computers!)

Not a big fan of devices employing boatloads of IC architecture either (and so called "engineers" determining for me how my Music, equipment or mix, should sound) but rather Masters of Good Microphone Placement and Arrays

The Blumlein pair is one of my favorites but RCA and Mercury were pretty creative as well!  (I am a HUGE fan of minimalism when it comes to recording)

As for your documentation on watching transmission line design behaviors and documenting them, THANK YOU, librarians are very important for us all

And a big Analogman "shout out" to Stromberg-Carlson and "Bud" Fried for all that heavy lifting!

That all being said, I am not a patent holder I am sorry to confess, so you are one of a kind in this dialog

Congratulations and all the best

Craig

[Shoedog]

On 4/25/2018 at 5:20 AM, ITCHIJO said:

HEY SHOEDOG: AS A MARINE I AND MY BULLDOG SAY, HEY JUST TAKE IT TO "OEM" STATS, AND THEIR VALUE WILL BE INCREASED. JUST DO IT, AND THAT IS AN ORDER!!! BESIDES WHAT THE DISCUSSION IS HERE, YOU ARE MISSING OUT ON SOME REAL HEAVENLY TUNES. GET BUSY AND GET "JAMMIN" TOO YOUR ADVENTS, AND LOVIN EVERY MINUTE OF SWEET SOUL MUSIC!!! STAND AT ATTENTION WHEN THE STAR SPANGLED BANNER PLAYS!!! ENJOY, MY DIEHARD ADVENT BROTHER!!! "GRUNT ITCHIJO"

Thanks just trying to learn here  Finally ready to do this- practiced on some other speakers first.