RETRO-MEASURE: Spendor SA1 (1976) monitor bookshelf speakers (The foam tweeter ring tweak!? And on "Listen For Yourself!".)

 

For this week's blog post, let's have a look at another "retro-measure"! This time, I had the opportunity to listen and test out the early-version Spendor SA1 speaker which hails from 1976. Remember that over the years, Spendor has released newer versions of this "classic"; most recently around 2009 as reviewed here in Stereophile.

This is another speaker I borrowed from my friend linnrd and I spoke about it back in late 2019 when I visited his place. This time, let's have a proper listen with measurements and compare the performance objectively and subjectively!

The "Spendor Mini Monitor Type SA1" came out just before the classic BBC LS3/5A design around 1975. Like the LS3/5A, these monitors were designed to be used in mobile recording vehicles.

As you can see in the image above, these are indeed >40-year-old speakers! There are cosmetic discolorations of the teak veneer but it's still looking quite good for something of this vintage, the box itself is constructed with birch internally I believe.

It's a 2-way closed speaker with 3/4" Son Audax tweeter and 6" Bextrene (polystyrene) mid-woofer. Crossover is at 3kHz.

As you can see, on the back, this is fitted with 5-way binding posts and can accept banana plugs. The Spendor stickers taped over the binding posts have long disappeared it looks like.

Dimensions are: 8.5" wide x 12" tall x 8.5" deep. Weighing just over 13lbs each.

Here's a closer look at the drivers on this old speaker. Notice the irregular texture on the surface of the doped Bextrene cone. Not the prettiest workmanship but this is the mid-'70s consumer tech!

Something else to note here is the presence of a foam ring around the tweeter! It reminds me of the squarish foam surrounding LS3/5A speaker tweeters to reduce cabinet edge diffraction. Interestingly, looking around the Internet, I could not find pictures of other old SA1's with this foam surround which looks quite old. I asked linnrd and got confirmation that indeed this foam ring was a later addition so for the main measurements, I'll take this off. I guess these were supposed to be some kind of "tweak" to improve sound.

The speaker grilles are cut out of a wood sheets covered in fabric. Plastic pin inserts secure them to the speakers:

I. Measurements

Alrighty then, here's a picture of the speaker ready for testing in the basement. Notice the foam ring around the tweeter removed; I actually measured with and without the ring to see what difference it made. As usual, the speaker was powered with my Emotiva XPA-1L amplifier. The DAC used for tone-generation is the Topping D10.

With foam ring around tweeter removed.

As passive speakers, it's good to start with impedance and sensitivity:

Impedance looks good and goes down to 7.6Ω at the lowest level, around 250Hz. Notice the EPDR (Equivalent Peak Dissipation Resistance) will dip down to 4.5Ω which is certainly not extremely low. There are 2 resonance peaks correlating with the 2 drivers at 66Hz and 1.3kHz. I don't see any discontinuities or irregularities in the impedance and phase curves at all! This suggests a well-dampened enclosure with minimal anomalous resonances.

Sensitivity calculated by average gated amplitude between 500Hz to 7kHz with a 2.83V sine sweep tone gives me a value of 85.4dB/2.83V/m. I believe these speakers were rated at 85dB/W/m so we're certainly in the ballpark. We can see from the +/-3dB red lines on the sensitivity calculation just how flat the frequency response appears.

Here's the CTA-2034A-inspired "qSpin" result:

As usual, my graphs are set to 25dB/decade aspect ratio with a Y-axis range of 30dB. The Spendor SA1 looks very good on the "qSpin"! The output level was measured at around 80dB SPL average on-axis and the "listening window" shows us that there is a bit of an accentuation up at 13.5kHz of about +2dB. There's a slight upper-mid and presence dip of about -2dB (4-5kHz). Bass has a -3dB point around 65Hz and -6dB of just above 50Hz. Certainly good for a relatively small, acoustic suspension speaker with a 6" woofer.

The Directivity Index looks like there's quite even dispersion into 10kHz and then the speaker narrows and "beams" into 20kHz which is not unusual. We can see this in the polar maps:

Below 10kHz horizontally, we see a nice and wide +/-60° dispersion pattern. On the vertical axis, it looks like it's best to listen between slightly above the speaker to around -15° for best sound. Furthermore on the vertical axis, you can see the effect of the crossover at 3kHz.

Along the time domain, here's the speaker step response:

Both tweeter and mid/woofer are arranged in positive acoustic polarity. The step response with its slight irregularity at 250µs suggests that the acoustic "center" is just below the tweeter axis and fits with the suggestion from the polar map that it might be best to listen to these speakers sitting with ear-level between the tweeter and mid/woofer.

The cumulative spectral decay "waterfall" graph looks good as well:

Again, this adds to the evidence that the enclosure is very well dampened with no concerns around resonance issues. You can compare this to the Radio Shack Minimus 7 which had a comparatively poor spectral decay.

Dynamics-wise, here's the multitone burst test for linearity between 70dB SPL to 100dB SPL, normalized to 0 at 85dB SPL:

At most around 1dB error across the 30dB range; not the best I've seen but I don't think the ears would mind at all.

Next up, let's look at distortions, here are some THD and IMD graphs:

The THD sweep graph looks quite typical of most speakers with portions of the spectrum showing more harmonic distortion. For this speaker, we see a little more THD between 2-3kHz. Otherwise, harmonic distortion remains well controlled below 1% (-40dB).

As for IMD, I must say that I am impressed by these 300/1300Hz IMD measurements from 60dB SPL to 90dB SPL! Consistently <1% distortion across the 4 output levels... Good stuff, especially given that these are >40 years old; I guess it's "broken in" but not "broken down"! :-)

Let's compare the stereo speaker pair I borrowed:

Overall, I like what I'm seeing here! Even after 40 years, we're still seeing maybe ~1dB difference in the frequency response between the two speakers. The impedance remains well matched. And the CSD likewise suggests that both enclosures are equivalently free from strong resonances.

A couple of final measurements. First, here's the difference between having the grille on versus taking it off:

It looks like the grille will dampen that 13.5kHz accentuation a little bit but otherwise, it functions quite transparently at least straight on tweeter axis.

And how about that add-on foam ring "tweak" stuck around the tweeter I showed above? Here's the "qSpin" graph with "tweeter ring" in place:

Compared to the "stock" SA1, notice that the foam ring introduced a suck-out into 9kHz on the order of -6dB and we also see a concomitant distortion in the Directivity Index. Here's what happened to the polar maps:

Notice the effect that a "tweak" like this had on speaker performance, easily demonstrable objectively even if one might not be able to hear it well (especially if one has limited high-frequency acuity). Needless to say, I would very much suggest that these foam rings be taken off the speaker unless one truly wants to suppress a significant portion of the frequencies in the "brilliance" audible spectrum. I suppose if  I listened to a lot of very poorly recorded/produced music with very harsh high frequency content, these might help. Even if I wanted to do this, a thinner ring would have been less heavy-handed, I suspect. :-)

Anyone know if it was popular to stick tweeter "diffraction rings" on back in the day?

II. Subjective

As in the picture above, I was listening to the Spendor SA1 with the foam rings in place as well as after taking them off prior to performing the measurements for about a week. The set-up is my usual, consisting of a combination of the Roon Server --> Raspberry Pi 4 streamer --> RME ADI-2 Pro FS R Black Edition DAC --> Emotiva XSP-1 preamp --> DIY Hypex nCore NC252MP amplifier. All hooked up with XLR balanced cables and DIY speaker cables.

You know how people say that "long-term listening" is the only way to know if something is good? In my experience this is untrue. Assuming one is playing a familiar song in a familiar room, I believe you can tell when you hear a great product within moments. This was what I felt about the Spendor SA1 even with the foam rings in place initially. The first song I listened to was Jennifer Warnes' "Bird On A Wire" (Famous Blue Raincoat) and by the end of the song, I knew I had to call my dad to come over and listen to these as he is particularly interested in vintage gear.

Simply beautiful, clean, balanced midrange right from the first notes and lyrics! These are really sweet speakers for vocals which I found rendered the human voice with a sense of reality and clarity that is highly desirable. The sense of "presence" was excellent on Roy Orbison's last album Mystery Girl with his unique vocals, and haunting sense of melancholy on songs like "In The Real World". I love how easy it was to emotionally connect to the music through these speakers and be transported back to a time when I first discovered Orbison's voice and became familiar with his work.

While sub-bass is too much of a reach, the bass on these speaker sound really good to me. Definitely not overaccentuated and certainly adequate to capture most of even large-scale performances. For example, I had a listen to Telarc's Erich Kunzel & Cincinnati Symphony Orchestra earlier version of the 1812 Overture with cannons and all. Excellent reproduction of the wide dynamic range, and even the cannons sounded reasonably credible even if not reaching fully deep enough in the audio spectrum. 

Taking the foam tweeter ring off liberated the perceived high-frequencies. A few weeks ago I watched and loved the new Pixar movie Soul with the family. Recently I bought a copy of the Soul soundtrack and love the juxtaposition of jazz compositions and piano work of Jon Batiste to represent the Earthly realm beside the ethereal score from Trent Reznor and Atticus Ross of the spiritual "beyond". The tracks "Falling", "Run/Astral Plane" and "Terry Time Too" benefitted nicely from taking the foam ring off by adding a bit more sparkle. I can see why some people might like to recess the "brilliance" portion of the audio spectrum and perceive this as creating a "warmer" sound that might be less fatiguing. That's fine so long as one understands the mechanism and recognizes the effect is not due to some magic. Without sticking any foam around the tweeter, this effect can be created by using a peak/dip parametric EQ of -6dB at 9kHz, Q value of 2.

One other new album I got recently was the 2CD set from the Eagles - Live From The Forum MMXVIII [2018]. While sadly this was recorded after the passing of Glenn Frey in 2016, Henley, Schmit, and Walsh were excellent and Deacon Frey and Vince Gill ("Don't Let Our Love Start Slippin' Away" is fun) performed alongside nicely. I appreciate that the recording maintained a good dynamic range of DR11 average although unfortunately, the production is of poorer quality than the excellent Hell Freezes Over from 1994. Definitely this is not worthy of "hi-res" (I don't think any live performances with an audience making noise are anyway). I've heard folks complain about the surround mix on the BluRay as well. The CD at least sounds decent and the presentation through these Spendor SA1's re-created a good sense of "surround" imaging of the band up front and illusion of being in the audience. This album can be a bit dull sounding so the foam tweeter ring is detrimental IMO.

I spent time with various other pop, classical and electronica albums as well which I'll reserve from spilling any more keystrokes on. All-in-all, a very satisfactory bookshelf-sized speaker!

III. Summary

I'm impressed! I don't think there's much more to say.

Spencer Hughes obviously knew what he was doing when he designed these back in the early 1970's and went into production by the mid-'70s. Given the vintage, I think it's natural to also think about the venerable BBC LS3/5A speakers of the day and the many fans of those speakers still (great site dedicated to LS3/5A). Remember that the LS3/5A is based on a smaller 5" mid/woofer; the SA1's 6" mid/woofer would/could/should achieve better bass extension. Maybe one of these days I'll have the opportunity to have one of those here at home for a listen and compare.

An inexpensive modern design similar to the Spendor SA1 might be something like the NHT SuperOne 2.1 speaker  (<US$180 each) - 2-way, closed box, similar dimensions, slightly larger 6.5" mid/woofer. I've heard good things about these, again maybe something I can check out in the future.

With the reasonable <100Hz extension that the SA1 provides, I think it would not be too hard to match these with a nice subwoofer in the living room crossed over around 80Hz and achieve some remarkable full-range playback. With a sensitivity of 85dB/W/m and good impedance profile, amplifier matching should not be difficult. If fact, it sounded great on my desktop with the SMSL SA300 Class D amp with only 30W into 8Ω although I would advocate for a good 100W amp for the living room to achieve that extra dynamic extension. If you haven't tried, it's worth estimating your amplifier power needs.

Of note, the results here look different from what was found in the Stereophile measurement of the new Spendor SA1 released in 2009. Lots of differences in terms of materials used for the drivers, enclosure design, crossover is different, and even the dimensions are different. Other than name and sealed-box design, I'm not sure what is even similar about these speakers.

Thanks again to linnrd for giving me the opportunity to listen and test these speakers!

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To end, I just wanted to spend a few minutes talking about that foam "diffraction ring" around the tweeter that was added by the original owner. Remember that over the years, people have used these in speaker designs, for example, here's a discussion of the application of this kind of "tweak" to the Acarian Alón Li'l Rascal Mk II speaker (see Addendum and also the Measurement changes) back in 2003.

Obviously the foam pad applied around the Spendor's tweeter resulted in profound effects which in my opinion were clearly undesirable.

If we were to talk to the previous owner who applied the tweak, he might have told us that the foam rings made a huge beneficial difference for him. While I would not be able to refute his subjective judgement or his experiential claims, to show you in the measurements what this tweak did to the sound I hope is a much more powerful disincentive to try doing such a thing knowing the effect regardless of what any one or more person(s) might testify! Again this is the power of taking an objective mindset and to seek facts rather than be satisfied with opinions.

An argument some audiophiles suggest is to "Listen for yourself!" to whatever tweak or supposed-beneficial products come our way. I obviously would not disagree either since personal experience counts for a lot on an individual level. But in practice, we obviously can't try everything the Industry produces or claims. Even if we were to buy a $1000 cable and likely return it due to lack of value, one would still have spent money at least on shipping costs assuming there were no international taxes or restocking fees. Better that we insist that companies come up with data and demonstrate the value of their products for us as consumers to consider first before anyone puts money down. Otherwise, the default position to take is that the product (and such companies) should be ignored if no evidence is forthcoming in my opinion.

Lastly for this week, reader Joe Pop sent me a link to this recent article by Brent Butterworth "The New Standard That Killed the Loudness War". It's reminiscent of this article by Ian Shepherd years ago in 2009 about loudness normalization with Spotify and the "end" of the Loudness War. Sadly, since 2009 there have been innumerable severely dynamically compressed new music for my liking. Well, let's hope it works out this time around. :-)

Take care and enjoy the music, audiophiles!