Large Advent/Dynaco A35 Double

[Guest kevemaher]

I have an idea how to use the strengths of each of these fine speakers. I have a pair of both lying around collecting dust just crying to be used. I'd like some comments on the idea below.

In my opinion, the Large Advent has great bass extension, but a poor tweeter. The A35 does not go too deep, but has a very smooth mid and nice highs.

So I'm thinking of stacking them. Turn the Advent woofer side up, put in an active xover at 50, 90, or 180Hz (12dB/octave) using an auto sub xover and power with a decent 100W transistor amp (I have an old Carver and a Bryston 3B). Put the A35 on top, run it full range, powered by a CJ MV-75 tube amp. This mod will cost less than $50 and has a built in level control. Preamp is Apt Preamp 2 (with two line level outputs).

Advent internal treeter connections will have to be cut and the coil on the woofer bypassed.

By the way, Pete B's deconstruction of the Advent shows a 1.6mH coil on the 4.7 ohm woofer. This provides a first order LPF with 3dB at about 450 Hz. This sounds way too low. The 0.3mH coil on a later rev gives a more reasonable 2500Hx xover. Am I missing something?

I will have to open the box.

Kevin

[Pete B]

I have an idea how to use the strengths of each of these fine speakers. I have a pair of both lying around collecting dust just crying to be used. I'd like some comments on the idea below.

In my opinion, the Large Advent has great bass extension, but a poor tweeter. The A35 does not go too deep, but has a very smooth mid and nice highs.

So I'm thinking of stacking them. Turn the Advent woofer side up, put in an active xover at 50, 90, or 180Hz (12dB/octave) using an auto sub xover and power with a decent 100W transistor amp (I have an old Carver and a Bryston 3B). Put the A35 on top, run it full range, powered by a CJ MV-75 tube amp. This mod will cost less than $50 and has a built in level control. Preamp is Apt Preamp 2 (with two line level outputs).

Advent internal treeter connections will have to be cut and the coil on the woofer bypassed.

By the way, Pete B's deconstruction of the Advent shows a 1.6mH coil on the 4.7 ohm woofer. This provides a first order LPF with 3dB at about 450 Hz. This sounds way too low. The 0.3mH coil on a later rev gives a more reasonable 2500Hx xover. Am I missing something?

I will have to open the box.

Kevin

You're missing baffle step in your calculation, and the fact that the load is not

resistive but rather inductive around the crossover point. The 1.6 mH coil

does provide some baffle step compensation, however because of the crossover

design the increased output around 1 kHz makes the BSC in the

woofer XO less than effective. The later inductor does very little as I have

commented in other threads. You really have to measure, or simulate,

the transfer function as loaded by the driver impedance.

The tweeter in the A-35 is quite a dated design that rolls off fairly early at the

top end.

[Horswispr]

I might just try stacking them wide open, as (I think) folks did with Advents back in the day. The Dynaco tweeters are old, but I still think they sound pretty smooth, especially if recapped with regular 5% Solen or Dayton 5.1s. Let us know how it sounds if you do it.