Bypassing pots

[Guest]

Hi,

I'm wondering if someone could explain to me some of the

details of bypassing pots. In particular, I'm wondering

if people actually disconnect the leads from the pot and

then connect/short them together, or whether they leave

the wires on the pot and short "in place".

Thanks,

[kkantor]

Disconnect the pot, and connect the appropriate wires directly together. Be sure you understand which wire belongs where, and that varies from model to model.

-k

[Guest]

Thanks for the reply.

I ended up doing what you suggested mostly out of lazyness -

it was a lot easier to simply remove and connect the wires

than soldering in a new connection between the two terminals,

since there were already wires connected. (I used the circuit

diagram available here to figure out which wire was what -

thanks to whoever made that available.)

I am wondering how much of a difference there would be between

the two methods, however. It would seem that if one shorted the

two terminals in place then some current would still flow through

the pot - I guess this would just be wasting the current capacity

of the amp? Is that why removing the pot from the circuit altogether

is suggested?

Also, how much of a sonic difference does the direct bypass

make? (Compared to the original setup with pots centered.)

My mid/tweets weren't functioning before the bypass so I

don't have a reference for comparison.

Thanks,

[tysontom]

>

>Also, how much of a sonic difference does the direct bypass

>make? (Compared to the original setup with pots centered.)

>My mid/tweets weren't functioning before the bypass so I

>don't have a reference for comparison.

>

>Thanks,

Disconnecting the level controls ("pots") on AR speakers (you did not mention which model) is certainly one way of ensuring reliability. There would be no level controls to oxidize, no "dropouts" or other related problems. However, the speaker won't sound exactly right or natural. Using the AR-3a as an example, the sensitivity of each driver (woofer, midrange and tweeter) is not identical, so the level controls can help to get more uniform output across the frequency spectrum. The midrange driver in that speaker has greater sensitivity than the tweeter, and by putting the mid-range control on the "dot" and putting the tweeter at close to full output better balances the output of the speaker. Bypassing both controls will also give the AR-3a a somewhat unnatural "presence" or mid-range brightness to the sound, unless the listening room is inordinately "dead."

A better -- though admittedly more difficult -- solution would be to completely rebuild the existing level controls or put new ones in their place.

--Tom Tyson

[kkantor]

Not all crossovers use the pots in exactly the same way. Sometimes, they form part of the circuit no matter how they are set, and it is best to leave them in circuit. Often they are simply "series elements" that work best when removed fully.

I guess I should have been more careful with my answer. Happy to help further if you can mention the product, or can trace the exact crossover design.

Ken Kantor

Intelligent Audio Systems, Inc.

[Guest]

Thanks to both replies. I suppose I should have described my

situation more fully before.

I have a pair of 2ax's, whose pots were definiately at the

end of the lives.

Based on information on this forum/site (and help from a friend

with a steadier hand than mine), I managed to remove the grill,

and discovered that the surrounds on the bass driver were also

on their last legs.

Although I'm not sure this was the ideal kit for the driver,

I obtained the generic 10" surround replacement kit from

parts express and managed to replace the surrounds. I didn't

replace the dustcap, however - nor did I remove and replace the

original. I don't know how severe the danger of misaligning the

cone is in practice. I had other minor difficulties following

the instructions due to the wire mesh on the drivers protecting

the cone - this prevented me from manipulating and shimming the

cone independently from the support frame, so I ended up gluing

the surround to both the cone and the frame simultaneously, using

a light magazine to weight the surround down while the glue set.

I then checked the mid/tweets by manually shorting the pots,

and they appeared to be okay. I briefly attempted to solder a

shorting wire onto the pot terminals, but given the wire and

solder already on the terminals, and the confines of the cabinet

with the other wires in place, I found that this was beyond my

skills. So I ended up heating the terminals till the old solder

liquified and simply yanked out the wires. I then twisted and

taped together the relevant wires, repackaged everything, and

called it a day.

I am not particularly keen on reopening the cabinet in the near

future, but I would appreciate any feedback/comments you may have

to offer. Also, there are a few questions that I still have.

First, is the putty/driver seal reusable? I had gotten some from

parts express when I ordered the surround kit, and so I used the

new ones, but it wasn't clear to me in the end whether that was

really necessary (the old putty still seemed fairly pliable).

I also put a lot less putty on that was originally there - it

seemed as though the amount that was originally there was overkill.

Second, I noticed that parts express sells stuffing material that

isn't the fiberglass material which is what I believe is in my

2ax's. I wasn't very careful about handling the fiberglass - I

was thinking that getting the non-toxic material may be useful

in the future. Are the materials essentially equivalent?

I apologize for the length that this message has grown to,

and if I've made any terminological errors - I didn't know

anything about speaker internals/repair 2 weeks or so ago.

Thanks for the forum!

[kkantor]

I'm travelling, so forgive the brief reply. I can answer in greater detail later, if you want. Not a problem.

1- What you should do with the existing pots in the 2ax's depends on their mode of failure: open wiper, open element, or various types of shorts. If you, or your friend, knows how to test them with an ohmmeter, you can make a decision. Replacement is possible, as is substituting a fixed power resistor. If you leave things as is, Tom T. gave a pretty good description of what you will hear. And there is no substitute for listening and judging.

2- As long as a decent air seal is preserved, don't worry about the putty. I use thin, adhesive foam weatherstripping, myself.

3- Replacing the fiberglass is not recommended unless you have means to test what you do. There are good replacement materials out there, but they don't swap at a 1:1 ratio, and so require some experimentation to get right. You can always get new fiberglass water heater insulation, if you need some in better shape than what you have. Put rubber kitchen gloves on when you handle it, and all should be fine. Other than a little itchiness if you rub against it, the main health issues with fiberglass involved workers who were making hundreds of speakers every day for years. And that would drive most people crazy first.

-k