ADS L520 Vintage Speaker Measurements

[MAB]

Here is a test of a pair of ADS L520 speakers. They are a modest 2-way, in a beautifully finished cabinet with removable steel mesh grilles. I think they look fantastic.

The drivers are a soft-dome tweeter and a Stifflite woofer, both are typical of many ADS speakers.

In ADS' literature, they talk about the tweeter.

I used to install car stereos and got great results with ADS auto-sound drivers which used a similar tweeter. I still have a pair in storage. They measure well. A/D/S also provides an in-room measurement of their tweeter:

I measured the raw drivers and will compare the tweeter to their published response.

The L520 is the middle of a modest line of 2-way speakers, I believe they were released in 1980. This pair was originally purchased in 1982.

I'll also test and compare to their specs.
The crossover is at 1.5kHz, 12dB/oct for all models. I see the L620 has a 10" woofer, that should be interesting. While there is no convention for driver size measurements , the so-called 8" woofer in the L520 is more like a 6".

I measured the impedance of the two speakers:

They are 4 Ohm minimum as stated. Not going to be hard to drive. Small impedance mismatch between the two speakers.

I took the drivers out and measured the free air responses:

The woofer has some resonances at 1.3kHz and 2.6kHz.

If I look at the nearfield response of the woofer I see more:

The 1.3kHz resonance in the impedance appears to be the woofer loosing composure, the woofer's response is very rough in the crossover region.

I compared the tweeter's unfiltered response to ADS' published response using WebPlotDigitizer to extract the data from the brochure for comparison:

It's good matching, and great response for a tweeter designed 45 years ago, and ADS was understandably proud to publish the data. I guess they omitted the woofer data...

I put the speaker on a turntable and did series of measurements across Horizontal and Vertical angles.

The woofer is falling to pieces well before the crossover filters it's response. The tweeter didn't seem to have a chance to match the 6" woofer's directivity at 1.5kHz.

In Room Response is not so bad:

It's 10dB down at 35Hz, not -3dB! So the bass extension is overstated. Overall, not too bad tonal balance. It has very nice sounding bass. It should have been a three way, with one of those beautiful ADS dome midranges, but then it would not be quite the budget speaker.

Lastly, here are the horizontal and vertical directivity plots:

The worst I can say is the speaker has muddy midrange. It has good tonal balance, with nice tight and tuneful bass. I played around with placement near a wall and it did significantly enhance the bass as expected, without sounding oppressively or boomy. Plus it looks great.

Attached are the SPIN and CTA-2034 data from VituixCAD.

 

[thewas]

Wow, what a lovely condition, thank you for the measurements!
But they also show the reason that most and the best models of them where the 3-ways like the L710 which I have bought 3 pairs till now (sold two and always regretted after), here are their (really good, so good that ít was the only time DIY magazine didn't change anything on their crossovers) measurements:

Braun L-710

Seit Jahren ist es mir eine Herzensangelegenheit, die Rubrik „Vintage-Hifi “ in der Klang+Ton zu verankern. Wir widmen uns einem Klassiker der Hifi -Geschichte.

www.hifitest.de

 

[Joe Smith]

I have my 520s in my main living room system and they sound great to me! Have a pair of 420s too that I occasionally rotate in to other setups. Both were obtained from a local flipper for about $70 each set. I do have the 520s angled from room corners and up on good solid metal stands to raise them slightly higher than our sectional sofa, so reflections are minimized.

I remain on the hunt for three-way ADS's, but they do not appear very often in the Midwest, seems like they sold better on the coasts.