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Jose

Early 2ax sound quality

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I'm new in this site and hope this topic was not discussed already. If so, please give me a hint in which thread. Thanks!!

I am very pleased to be part of the community worldwide enjoying the same affinity for these exceptional speakers.

Sorry if my English is not good, I hope good enough to communicate with you and understand each other well

I have three pairs of 2ax, two of them working and sounding very well. They are become important to me, I spend hours every week enjoying music with this great speakers

The third 2ax pair on speakers is an early model, I guess 1969-1970 with a 6 hole 10'' woofer (bigger outer diameter circa 11'')

The cabinets of this third pair are in very good condition, and so the drivers. All drivers are basically working but the warm, deep and very pleasent to hear topical AR bass is missing in these speakers. If I compare the bass response of them with the others with the 10'' woofers and 4 holes, they are by far not so good.

I checked the crossover, everything looks original and fine. Potentiometers are not the originals but look and work fine.

I did not checked the weight of the stuffing and maybe some of it is missing. I believe though these speakers should forgive some misalignment of the original manufacturing specs. But anywayI the sound quality of these speakers is not good at all. I bought them refoamed from a private ebaY seller and I guess the foam used might be too hard i.e too stiff for the 2ax original acoustic design.

Any ideas where the problem might be would be very appreciated

Thanks in advance!

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Welcome Jose

The early 2ax woofer was the cast aluminum frame/cloth surround type. The sealant on the cloth surround may have become dry and as a result the surrounds may be porous. If they are, the speaker is no longer air-tight and the bass response will suffer.

Try this: Put your thumb and 2 fingers around the dust cap, like a tripod, and push the woofer cone in. Let go and the cone should return slowly. If it pops right back ut, you have a leak and it may be the surrounds.

Are you in this country? There is only one sealant that is right for these surrounds. It's made by Classic Speaker Pages member RoyC and sold by ebay seller Vintage-AR.

Try the test and let us know what happens.

Kent

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Oh. Those pictures are new. Obviously not cloth surrounds.

btw, that old wax capacitor should be replaced.

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Thanks for your feedback JKent and Aadams. I'm happy to be part of this AR community

The woofers are the 10'' with bigger outer diameter and 6 holes, but no cloth surrounds.

And yes the surrounds were replaced before I bought the speakers, and I guess the foam used is too hard so that the travel of the woofer is somehow limited.

You are right with the capacitor, they are original and should be replaced after so many years...but this seems not to be the root cause for the different bass sound. The other 2ax I have have also the original capacitor and sound much different.

Do you know if these early woofers with the 6 holes sound different than the later 10'' with 4 holes?

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5 hours ago, Jose said:

Do you know if these early woofers with the 6 holes sound different than the later 10'' with 4 holes?

There is no practical difference in the bass performance and the cap is not part of this problem. 

Assuming you have compared the bass of this pair with your other 2ax pairs in the same position, it could be the surrounds but I would be thinking first about the gasket seal around the woofer and your stuffing.

You seem to have a blend of glass fiber and polyfil.  They are interchangeable but not ounce for ounce and if you have too much of either it will overdamp the bass.  As I recall from a RoyC post, you should have around 22 ounces of glass fiber or 16 ounces of polyfil in the 2ax.  There is no rule of thumb for blending the two materials in the same cabinet.

If your seal around any of the drivers is not air tight it can degrade bass performance. It looks like you have scrapped away most of the sealant around the woofer hole.  Try using foam sealing tape if you can obtain it,  otherwise the duct seal material works just as well but less forgiving to remove and replace especially with chipboard baffles.  Check the other drivers for air leaks around the edges when you do the push test on the woofer after it is intalled.  The only leaks in the cabinet should be around the pot stems.

 

Adams

 

 

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I have an AR-2ax from 1971 with the wider 11” diameter frame, 6 screws and a foam surround.  The bass response is reasonably good.  About the same as my AR-14. 

I noticed in your photo that the particle board in the cabinet recess looks pretty rough.  When I removed the woofer from my 2ax to replace the surround, the sealing putty that AR used pulled some of particle board with it, leaving a pitted surface.  Before I reinstalled the woofer, I patched (DAP plastic wood) and sanded the particle board in the recess to give me a fairly non-pitted surface.  Also, I made sure all residue was removed from the back of the woofer frame, before I applied the foam tape.  I got my foam tape from Parts Express (https://www.parts-express.com/speaker gasketing tape).

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On 5/22/2020 at 5:51 PM, JKent said:

Try this: Put your thumb and 2 fingers around the dust cap, like a tripod, and push the woofer cone in. Let go and the cone should return slowly. If it pops right back ut, you have a leak

 

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Thank you all for your replies.

Regarding the tightness check JKent, I tried the check pushing the caps with the well working speakers and the problem speakers and did not notice a big difference between them.

But I will pay more attention to the stuffing and the tightness of the cabinets and sealing surface between the woofer and the cabinet. 

Your recommendations about reducing air leakage make sense and I'm happy to hear that the woofer itself are not the root cause.

I will change to the foam tape to seal all the drivers, check the contact surface of the cabinets and try to get new stuffing to refill the cabinets.

Thanks a lot for your support, we stay in contact

 

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2 hours ago, Jose said:

I will change to the foam tape to seal all the drivers,

Be careful.  The tweeters have plastic flanges and maybe these mids also.  If they have never been removed the hardened sealant can make driver removal difficult and damage from too much force is easy.  If all you are concerned about is leaks, you can push in a bead of duct seal around the circumference of the mids and tweeters.  Deal with the woofer seal  and stuffing first.  You probably don't have leaks around the other drivers.  I recommend not removing them unless there is a good reason, in which case it is definitely better to use gasket tape for re installation.

Adams

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Thank you Adams. Good recommendation.

Also thanks to AR55. I'm trying to find a good gasket tape here in Germany. Your recommendation to reduce the roughness of the cabinet recess is good

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Don’t forget to make sure the polarity is correct on the woofers. If one is accidentally wired backwards, these out of phase woofers will cancel each other’s bass out. 

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In the last three days I finally had some time to work in the 2ax. Here is the update


I began with one of the loudspeakers and focused on the stuffing and on the sealing between drivers an cabinets.


About the stuffing, I took the white polyfill out and left only the fiberglass stuffing. Checked the remaining weight 644gr (22,5 ounces) which is quite close to the recommendation and left it so.


I worked quite long on the woofer sealing trying to get a good flange surface. Spent quite long removing the old putty from the woofer flange and the seating surface of the cabinet. Used plastic wood to fill some dents in the recess surface of the cabinet. I sanded the surface after that achieving a flat and smooth seat.

Using a thin foam gasket (it has a strong adhesive on the cabinet side) the woofer seat is now really air tight. I checked then the sound quality comparing with the other 2ax loudspeaker expecting to hear a huge difference, but...was a little disappointed to hear only a tiny improvement.
The next was to carefully remove the midrange and tweeter to see if the air leak was coming from there. The midrange was sealed only partially with putty and two of the screws had no clamping force. The tweeter had no sealant of any kind at all.
By the way JKent you were right, the tweeter flange is really delicate and this one had a crack on the plastic flange and quite big plastic deformation in the area of the screw holes. Someone before me applied too much torque to the screws...

That's why I tryed to use gasket around the tweeter magnet trying to seal it radially in the cabinet instead of using the gasket in axial direction as usual. Unfortunately it did not work as the gasket is quite thick and the diameter clearance between the tweeter an the hole in the cabinet too small. So the tweeter did not fit in the hole...and it took me another 1/2 h to go one step back and remove the gasket from the tweeter body...

After that I filled some dents and used sandpaper to prepare the flange surfaces of the cabinet and discovered then that the nuts of the midrange in the cabinet were losen. That was the explanation to the missing clamping force of the screws.


Summarizing... I repaired all that mentioned as good as I could, put all together and compared finally the sound again with the 'unchanged' loudspeaker.
I can definitely hear now the soft and deep AR bass in the repaired speaker.
So it was not only one root cause, but several things that led to a bad bass performance.
I also checked polarity of the woofer and the other drivers, everything was fine.


I will repair the second speaker in the same manner the next few days.


Thank you all again for your support and the good recommendations !!!

It was very nice after the effort to hear the 2ax performing well again. That great sound we all like to hear...
The time went by so fast, it has been great fun.
Lessons learned for the next project... a pair of 3a from 1974...


But I leave that for another thread 😉

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I recommend following through with replacing the crossovers and maybe even the tweeters.

just finished off a pair and the rewards were worth the effort 

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