Advent A3 versus A4

[Guest retsoo]

Hello everyone...I just picked up a pair of walnut A3's and hope to stack them with my A4's What is the difference between the A3 and the A4? Both have the metal woofer and the orange tweeter. I have read here in the forum that it is not a good idea to stack different models. Does this apply to the A3/A4 combination?

On another note, the tweeters in the A3's I just got will only work when the switch is in the extended position, normal and decrease have no sound. What should I be checking on the crossover?

Thanks for your input!

Fred

[Guest wbz]

Hi Fred. I have a stack comprised of New Large Advents and Advents/1 with a pair of original Advents on the side. In my case they mix fine together. Your mileage may vary.

DL a copy of the xover available in the Library of this forum. Assuming the switch is good with no broken wires you will find R1, the 3ohm resistor, open. If it is open you may find some other damage. A resistor would normally not just "go bad". The usual cause would be escessive current through it. Which would imply that every other component in series with the resistor could have been stressed to near failure. At the very least I could check the capacitors with an ohmeter to make sure they are not shorted. I original it wouldn't be a bad idea to replace all the caps anyways. Others have opinions over which brand of caps to use. I'm sure their advice will follow. Myself I stick with midpriced electrolytics and polystyrenes from Parts Express. They work fine for me.

[Guest retsoo]

Thanks...didn't find the schematic in the library but did fine a nice diagram of the crossover from Pete B in one of the posts. Anyway, not sure which diagram you refer to but R1 has a value of 1.5 in Pete's diagram which is what is installed. You have to bear with me as I'm electronically challenged. I measured with the woofer and tweeter disconnected from the crossover and the switch in the normal position. R2 is open and R1 seems to fluctuate between 8-15 ohms. With the switch in decrease mode, R2 is open, R1 measures 15M ohms. In extended mode, both R1 and R2 measure about 16M ohms. Let me know if the procedure to measure is correct, or do the components have to be isolated, as in unsolder everything. Thanks for your help.

Fred

[Guest retsoo]

I think I can answer my own question now with regards to the difference between an A3 and an A4. After taking apart the A3's I picked up today and comparing them, the only difference appears to be two yellow wires in the crossover, the A4's have more insulation on them. Other than that, they are identical. Same finish, same lumber inside and out, identical crossover and speakers. The A3's have a date of Nov 1977 and the A4's June 1978. So, why the model upgrade for two wires?

[Doug G.]

A3 and A4 don't designate a model number. It has just gotten popular to refer to them that way.

The speaker is still "The Advent Loudspeaker" albeit the new version.

The 3 and 4 are just continuations of the serial numbers.

The original masonite Advents went up through serial number 299,999 and the New Advent started at 300,000 and went on up through 400, something.

The real model designation is the "A" for walnuts and "U" for utilities.

I hope this is clear.

Doug

Oops, I forgot, anytime you measure a low ohmage resistor, even if in circuit, you should get pretty close to the rated resistance if the resistor is good.

This is because any other component in the circuit (except low value inductors) is likely to have greater resistance (or infinite if it caps.) so the meter will still read close to the resistor's value.

If there happened to be an inductor in parallel with the resistor, you would get a lower resistance reading than with the resistor alone but you would never get a higher reading (resistors in parallel etc.)

In other words, if you are measuring across a 1.5 ohm resistor and you get a very high reading, the resistor is most assuredly bad.

Doug

[Guest retsoo]

Thanks Doug on the A3 A4 clarification and the resistance info. I have ordered the parts and will rebuild the crossovers. Would too much current cause the resistors to blow or would this be an age thing? One of the resistors had the green fuzzy stuff on the wire coming out of the resistore at both ends.

Fred

[Guest wbz]

Like Doug said, looks like resistor is bad. Green fuzzy stuff?? Must have done time in a damp basement. Maybe it's not burnt open, just corroded open. Are these Large Advents? I only know of the crossover with one resistor. R1, it's a 3 ohm which is in series with the tweeter. In the increase and normal mode it is bypassed with an 8ufd, or 16 in older ones, capacitor. The Advent Utility Schematic is the fifth item down in the Advent section of the Library from the home page. As far as I know, and have ever seen, the Utilities are the same as the walnut version. Let us know how it's going as you proceed.

[Guest retsoo]

Yes, these are large Advents. Got these from a guy whose basement had things like Tannoy, Stax, Carver, MacIntosh...etc, no dampness here! Both the A3's and A4's I have do have the same crossover, two resistors, 1.0 and 1.5 as per Pete's New Large Advent schematic. It's going to be a while before I get the parts. Spent all day yesterday looking for the appropriate parts locally, nothing ( I'm in Canada). Parts Express it is! So, it's wait about 2 to 3 weeks while USPS and Canada Post do the parcel exchange at the border.

Fred

[Guest wbz]

Well i'll be. I guess if I had bothered to look that shematic up my prior post would have turned out differently. My U4's, and others I have seen, xovers are identical to my U1's. I guess I've never seen a New Large Advent like yours. Sorry for any confusion Let us know how they sound when your done.

[Doug G.]

A speaker beginning with a U1... serial number should not have the same crossover as one with a U4... number because they should be different speakers.

The U1 speaker would be an original with masonite woofers and the U4 would be a "New" Advent with the all-metal woofers.

Although the crossovers are similar, the components are different.

The crossover is at ~1000 Hz for the original Advent and ~1800 Hz for the New Advent.

Doug

[Guest wbz]

Geez, am I sorry for posting. :+ (couldn't find a foot in mouth smiley) Now the thread is poluted with my disinformation. I would have sworn my U4s, past and present, were the same as my U1s. Now what am I going to do with the 16ufd & 8 ufd caps I ordered to upgrade the crossovers someday.....

[Guest retsoo]

I finally received my parts yesterday and have now rebuilt the crossover's in the A3's. I used the Dayton resistors and Solen 6.2 and 6.8 caps from Parts Express.. I also installed new surrounds. All of this in anticipation of stacking them with my A4's to hear what everyone has been talking about. I hooked them up to my amp in the A/B configuration so that I could compare the two sets of speakers. The A4's have also had the surrounds replaced last spring but they have the original crossovers. I could not believe the difference in sound when comparing the two sets of speakers. The A3's with new crossover's have much crisper, clearer highs and midrange when listening to strings, horns or cymbals etc. They seem to lack a deep base though. The A4's with original crossovers sound like the midrange and high's are almost mute, but has a definitive punch with the base. Is this an expected result of upgrading the crossovers??? Does a new crossover really change/improve the sound that much. I like the sound of the A3's, with the exception of being a bit weak in the base. Will the base improve as I get more use out of them since the surrounds have just been installed?

Any thoughts/opinions on this are greatly appreciated.

Fred

[Guest wbz]

Even though my credibillity is low I will offer my 2¢. I have found that Solen caps do sound a bit brighter but tend to "burn in" nicely. As for the bass, if the surrounds are new they will definitly get better. Did you stack them with the tweeters together and wire them in parallel? Most A/B switches do this but it's worth checking. Most people elevate the bottom woofer about a foot off the floor to tighten the bass, mine are spiked so about 2" off the floor & suit me fine. Let 'em burn in for a week or so before you listen too critically.

[Guest retsoo]

They are stacked with the tweeters together and in parallel, but I don't have them off the floor. I have read here a few times about letting them burn in. Thanks for your input.

Fred

[Guest One-Shot Scot]

>Hello everyone...I just picked up a pair of walnut A3's and

>hope to stack them with my A4's What is the difference between

>the A3 and the A4? Both have the metal woofer and the orange

>tweeter. I have read here in the forum that it is not a good

>idea to stack different models. Does this apply to the A3/A4

>combination?

> On another note, the tweeters in the A3's I just got will

>only work when the switch is in the extended position, normal

>and decrease have no sound. What should I be checking on the

>crossover?

>

>Thanks for your input!

>Fred

In the New Advent series speakers, the A3 and U3 crossovers are identical and the A4 and U4 crossovers are identical. The components of the "3" series and the "4" series crossovers are identical, but the layout is different. The insulation on the "4" series crossover wires is thicker than that used on the "3" series.

NEW ADVENT A4, U4, A3 and U3 Crossover Specifications:

(1) 0.33 mH inductor

(1) 13uF bi-polar electrolytic capacitor

(1) 1ohm 10W sand-cast resistor

(1) 1.5ohm 10W sand-cast resistor

(1) 3-position tweeter switch

(2) binding posts

(1) 20 gauge red wire

(2) 20 gauge green wires

(2) 20 gauge black wires

* The wires are very thin to the extent that they may actually be 22 gauge.

The original crossovers are of made of components which are of marginal quality. A typical overhaul involves replacing the electrolytic capacitors with polypropylene models, replacing the sand-cast resistors with the same type and maybe soldering on some thicker gauge wires. This still leaves the original light-duty inductor and the 3-position switch, which is probably corroded inside. The new sound will be bright on the high end, but without a boost in woofer performance, the job is only half done.

It is my opinion that there is nothing worth salvaging in the original crossover design. A new crossover built with a Jantzen 15-gauge air core inductor, a 6.2uF polypropylene capacitor in parallel with one of 6.8uF value, a 1ohm 12 W Mills wire-wound resistor, heavy-duty binding posts and thicker hookup wire will run circles around the original New Advent crossover. Last year I bid $22 for a pair of A3 crossovers on eBay so that I would have a spare set. This was a complete waste of money, because I also have my original A3 and A4 crossovers which were replaced with crossovers made from the components listed above.

https://home.comcast.net/~newadvent/NewAdventCrossovers.html

There are differences between the A3 and A4 cabinets, as can be seen by clicking on the link below:

https://home.comcast.net/~newadvent/NewAdventCabinets.html

Your second question has already been answered: You most likely have one or two bad resistors, since, when placed in the Extended position, the 3-position switch bypasses the resistors.