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.

 

[OhSoJoe]

Thanks for your vintage speaker measurements.
I have and enjoy the ADS L470. I posted less sophisticated measurements to audiokarma last year (HERE). The 470 appear a bit brighter than the 520, probably as expected, otherwise very similar.

 

[hedrick]

I have an earlier version, L500. It probably also has the rising bass, as it sounds better with bass turned down a bit, bit it may also be the room. Other speakers also have it. I see no sign of an issue in the crossover with a slow frequency sweep, nor any audible muddiness. It sounds much more transparent than Paradigm studio 20, which has good measured performance from several sources.

 

[mcw]

Did Telarc use ADS speakers for monitoring?

 

[hedrick]

Did Telarc use ADS speakers for monitoring?

yes, although not this model.

 

[suttondesign]

I am pretty sure these were designed by Michael Kelly. He later started Aerial Acoustics.

I bought a pair of L810’s in 1981. I later owned various Aerial models.

 

[jon_s]

Did Telarc use ADS speakers for monitoring?

Late reply but, yes; the 910s were used for the famous 1812 Overture with digitally recorded full-dynamic-range cannons that wrecked everyone's systems back in the day. They used them with Stax DA80M class A monoblocks. Other albums reported use of the BC8s, 980s, 1530s, and even 1590s. IIRC those were used mostly with Threshold amplification.

Another notable studio use of these Braun/ADS style speakers were by George Marino at Sterling Sound, who was said to prefer Braun LV1020 active monitors for mastering back in the day.

I currently have 910s, BC8s, 1230s, 1590s, and Braun LV1020s. All are awesome. I have owned 620s, but also 810s and 980s, which I only got rid of to justify the BC8s and LV1020s (which are more rare but frankly have similar sounds and performance, respectively).

 

[Mr. Widget]

I always liked this era of ADS speakers.

I had a pair of L910s for a few years. The price was a steal... around 2008 they were literally sitting by the curb of a nearby neighbor. I asked to confirm they were really hoping the speakers would disappear and they confirmed that the "large brown boxes" were no longer appreciated or wanted.

I rescued them and enjoyed them for a time, then they went into my basement only to be given away when I moved. I was into them for $150 because I bought the oh so cool looking stands from someone on eBay.

Not mine, but they looked like these.

 

[thewas]

Since one year I added a pair of L810 to my collection (had only L710 and smaller ones before) and with mainly some EQ in the bass region as my room is very bass absorbing they sound astonishing good, even more if you consider they are more then 50 years old! A good friend of mine who owns the big cardioid Geithain RK921 and used to have Neumann KH420 says its one of the best stereo setups he has ever heard.

 

[jon_s]

I had a thought and wanted to come back to this...

In Room Response is not so bad:
View attachment 408338
It's 10dB down at 35Hz, not -3dB!

How much was your wall reinforcing this measurement? I would not be surprised if the bass extension spec included a full +6dB rear wall bonus, given how speakers were assumed to be used back in the day. Or, at least, being -9dB from 92dB spec would align with that.

 

[MAB]

I had a thought and wanted to come back to this...


How much was your wall reinforcing this measurement? I would not be surprised if the bass extension spec included a full +6dB rear wall bonus, given how speakers were assumed to be used back in the day. Or, at least, being -9dB from 92dB spec would align with that.

I make quasi-anechoic measurements. I measure bass response and sum that with gated high frequency measurements that I take using a turntable to rotate the speaker between each measurement. I do it in VituixCAD, the details are here:

https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_Measurement_REW.pdf

Yes, close to a wall will result in higher bass output. Assuming I did the summation correctly , placing the speaker near the wall should give a bass boost over my estimated in-room response.

 

[Juhazi]

MAB, what distance and gating settings did you use in measurements? I suppose you don't have Klippel NFS.

Room response does not show any modes or late reflections, how is that possible?

 

[MAB]

MAB, what distance and gating settings did you use in measurements? I suppose you don't have Klippel NFS.

Room response does not show any modes or late reflections, how is that possible?

No, I have a cheap home-made turntable and a mic. Instead of scanning, I rotate in cylindrical coordinates.

I used 1 meter for these A/D/S.
I don't recall the gating.
You don't need a near-field scanner. Just a turntable and a mic.
As posted above, VituixCAD has a step-by-step guide.
There is also a tutorial here:

How to make quasi-anechoic speaker measurements/spinoramas with REW and VituixCAD

NOTE from ASR staff: The following content has useful tips and details, but as REW and VituixCAD continue to be actively upgraded, some parts of this thread may be obsolete. Be sure to consult the respective software sites for the latest updates. Quasi-anechoic measurements are a way to...

www.audiosciencereview.com

And a discussion of the math here:

Understanding How the Klippel NFS Works

Questions regarding how the Klippel NFS works are raised in many of Amir's speaker reviews. Thomas has suggested starting a thread on this topics and here I am. I am starting this thread with a brief description of the basic principles behind the NFS. You can find much further details on the...

www.audiosciencereview.com

The method isn't perfect. Ageve does a better job than me in controlling for things like reflections off the mic stand. Larger speakers become difficult, the radiator in spherical coordinates no longer is a good approximation. But I get response directionally similar to measurements with a Klippel.