Restomoding a pair of Vintage Advent Baby Advent II Speakers

May 11, 2018

#250

Gentle reader,

Yes, this is my 250th post. When I started this blogging stuff, oh so long ago, it was just something to fool around with. I had no idea people would not only read my words and look at my photos, but that so many really enjoy it! It truly warms my heart. Thank you.

I have never owned any ADVENT speakers. They are one of several speaker lines from the 1950's and 1960's that were ones sought out by music fans. Unlike Klipsch, Altec Lansing and other names that made speakers so efficient that a few watts would drive them very loudly, ADVENT speakers used the then new, "Acoustic Suspension" concept which used sealed speaker boxes stuffed with fiberglass and required more power to get to loud levels. But, the sound they did produce and the low bass they made certainly made many fans around the world.

Whether these Baby Advent II speakers which are from 1992 were made by the same company is unknown to me. They retailed for $200.00 then, around $320.00 in 2018 dollars. I found them at a thrift store and immediately saw the usual deteriorated foam surrounds on the woofers. But I was not discouraged. For $11.99, they came home with me. Plus, they were made right here in the USA.

I gently played music through them to confirm all four drivers worked. They did. At first, I was going to just replace the foam surrounds, but then they have those cheap spring terminals that I can't stand. removing one revealed they also have their crossovers integrated with the terminals. So, I decided to upgrade the crossovers as well. Parts Express: Speakers, Amplifiers, Audio Parts and Solutions to the rescue. They crossover at 4,500 Hertz and to get that exact crossover meant ponying up more money, but hopefully, the sound will be worth it.

As you can see, they exhibit typical foam rot. In case you do not know what that foam is for, a brief explanation: The speaker cone which is glued to the coil (beneath that cap in the center) must be kept centered AND the front of the cone's sound must be kept separate from the sound coming from the rear of the cone. Many speaker makers choose foam rubber over rubber itself. Usually for cost purposes. 

Above are the Dynaco A25XL speakers as they were when I first opened the box. Despite the dirt, notice the surrounds on these woofers are rubber. These speakers are from around 1977. Rubber is not prone to rotting like foam is. Note also the screens below the woofers. They hold a "Critically damped" amount of fiberglass. Dynaco calls this method of venting their cabinets, "Aperiodic" and state that no sounds emit from these vents. But enough about that.

Let's take a look at what ADVENT chose for the crossover for the Baby Advent II speakers. Specs state that their crossover point is 4,500 Kilohertz. Which means anything below that frequency comes out of their woofers and above comes out of their tweeters. 

Below, on the right, is the ADVENT crossover. A coil is glued to the terminal housing, a square ceramic resistor (white thing) and a capacitor make up the three components. The capacitor stops any sound below 4,500Hz from reaching the tweeter. The coil stops any sound above 4,500Hz from reaching the woofer.
Now, look at the replacement from Part Express. Despite the obvious size increase, the components are many and much larger too. The blue wires are so the crossover can be used with either 4 Ohm speakers or 8 Ohm models. These measured 6.5 Ohms, so I left it on the 8 Ohm plug. See the two different types of coils? Plus three capacitors. These babies are not cheap in price or quality. 

Their crossover is mounted to the inside of the speaker terminals. I hate those types of speaker terminals and always convert my speakers to banana/binding post terminals. Since their crossover cannot be used with the replacement terminals (below, right) I needed new ones.

The new round terminals fit perfectly and work so well.

Parts Express thinks of everything and that includes having a wooden plate riveted to the fiberglass board the components are mounted to. Thus, I was able to glue it to the back wall on the inside of the cabinets above the new terminal.

This is what it looks like all wired. I waited for the glue to dry, of course. ADVENT made the wires for the tweeter extra long so that the fiberglass insulation can be installed and still allow the tweeter to be connected to the crossover.

Before and after soldering the wires to the terminals.

Since the color stripe on Advent's wiring is not easily seen, I used a black marker to color the negative terminals on the driver's wires.

Along with crimping, I soldered the wires to the terminal as seen above. Below, shows the fiberglass reinstalled in the cabinets. I poked a hole for the woofer's wires to be able to connect to the woofers.

I have not had good results with refoaming woofers in the past. So, instead of buying generic new foam via eBay, I chose to buy from Parts Express. They have a kit with specialized glue, swabs to apply it, premium foam, replacement dust caps and coil shims. Plus, directions. I now see what I was doing wrong in the past.

Here is the first woofer stripped of the front gasket (why do they even install those anymore?) and the destroyed old foam.

Here is my solution to raise the cone in order to safely scrape the old foam and glue from the metal speaker housing. NOTE: These woofers are "long throw" which means they move back and forth a considerable distance over most woofers. Most will not be able to sit this high.

Since they move so far, ADVENT used dust caps that allow air movement from the piston/cylinder area to escape through the dust caps. This presented a problem since the replacement caps are sold plastic or pressed paper. 
I got lucky with the first one and managed to get the new foam installed with the cone still centered. It played fine and sounded great. Below is the results.

The second woofer, all though I did it exactly the same way, it ended up a little crooked and buzzed while playing. 

Above are the tools I used: Folding utility knife with razor blades. A straight-edge razor scraper with it's own blades and plenty of spares of both kinds of blades
Faced with removing the front gasket and just-glued on new foam, I had to try a different tack. (Tack? That's what sailboats due when sailing against the wind.) So, I got out one of my trusty Xacto knife kits and chose what is essentially a tiny putty knife blade. I carefully worked it between the foam and the metal and slowly worked my way round the speaker until all was freed. 
The breathable caps seem to be made of finely woven fiberglass and I carefully cut around the base with a standard Xacto blade. Divine intervention suggested that I cut a hole just smaller than the diameter of the freed cap in one of the paper dust caps. This I did and using the same speaker glue, I carefully merged the two.

Yes, they look different. Keep the grilles on.

Using the supplied shims (it did not occur to me to photograph that) I carefully slid three in between the coil and metal pole piece of the magnet. These keep the "spider" exactly perpendicular to the pole piece. Plus, I was able to raise the cone again with the knowledge that it was not going to get crooked this time. 
Following the same steps I reglued the foam to the metal frame. By first lowering the cone until the foam just touched the metal. Once dry, I reattached the front gasket. Once reinstalled (the next day) in the cabinet, I hooked it up and tried it out. No bad sounds but plenty of great ones!
Last step was installing the new hybrid dust cap, above. Once that was done and dried, I taped off the black portions of the cabinets and began the laborious process of sanding off the old finish and stain from the top and bottom cabinet caps.

 Here is the post-sanded compared to the old finish.

You may have seen my blog post detailing all the remodeling that I'm doing to our house. Included in that is converting wall-to-wall carpet covered pine stair tread to new solid oak stair treads with white painted risers.

We are very pleased with the results. I have since replaced the foyer floor with acacia wood flooring and begun the stairs leading down. Anyway, I have stained the top and bottom plates with the same stain as the stairs.    

These are the tops after staining.

 The extent I went to, to protect the black veneers.

 Just LOOK at that grain! I believe it is oak.

Here they are from the front. The CFL lighting above the workbench renders the wood a different shade than they really are.  

Here they are in the room I call my "office". They are sitting atop my Cerwin-Vega! LS-12 speakers. By far the most efficient of my five pairs of speakers with certainly the best bass response.

I'm listening to Alex Bugnon, pronounced boon-yon, CD titled 107 Degrees in the Shade right now through these newly completed speakers. I must tell you, they sound FANTASTIC! The new crossovers are certainly worth their price. I'm blown away. These are keeper speakers! And here they are now ensconced atop my Klipsch KG4s.

UPDATE: I decided to use these as front speakers with my more efficient Dynaco A25XL speakers as surrounds. The music being routed by a Dynaco QD-2 five channel surround sound passive device. It is a stunning combination!

This photo was prior to the Advents joining the system. Also, the Dynaco speakers are up on stands now. 

I was given these specifications for the Advent Baby Advent II speakers:

Freq response: (+/- 3dB): 60Hz – 21KHz
Impedance: 6 ohms nominal
Power Handling: 50 watts RMS, 150 watts peak
Sensitivity: 89 dB
Crossover freq: 4500 Hz
Woofer: 6.5 “, Tweeter: .75" Mylar dome

Those explain the long-throw woofers and awesome sound. They were made to handle a LOT of power. And they do! 

Thank you once again for taking the time to read my humble blog.

Scott

UPDATED: October 26, 2018