Old vs New

[KEW]

I have a couple of old pairs of speakers that have been in storage - a pair of AR3a's and a pair of Epicure EPI-100's. The AR3a's were always better for tight and deep bass, but the EPI's had a better tweeter.
I decided I really need to get rid of some of my speakers and either of these are still bringing a few hundred dollars. But first, I wanted to do a comparo, just to see how the sound of my first decent stereo speakers compared with modern stuff. This was a quick and dirty project, so I grabbed what was easiest to get to or to carry and ended up with the EPI's vs. Paradigm Signature 2. The EPI can be likened to the much more ubiquitous Small Advent Loudspeaker (but before the Advent), it was a good value product of the day, but nothing exotic, by any means. Keeping with the quick and dirty theme, I just used what was in my CD changer (some Linda Ronstadt and Yes, Close to the Edge - nether is a reference quality recording)

I must say, what I heard was absolutely astounding to me!

Of course the Beryllium tweeters of the Sig's had more extension, air and detail, but for bass, the acoustic suspension (sealed) EPI's seemed to totally spank the ported Sig's for resolution!

I had just assumed a top of the line modern speaker from a major manufacturer would beat 30 year old technology on all counts. Go figure!

Furthermore, the overall balance of sound from the EPI was competitive.

So, there it is, my one hour "slam dunk" comparo has now turned into a "next free weekend" project to set these up in my A/B test system and seriously determine how they compare!

 

[TLS Guy]

I have a couple of old pairs of speakers that have been in storage - a pair of AR3a's and a pair of Epicure EPI-100's. The AR3a's were always better for tight and deep bass, but the EPI's had a better tweeter.
I decided I really need to get rid of some of my speakers and either of these are still bringing a few hundred dollars. But first, I wanted to do a comparo, just to see how the sound of my first decent stereo speakers compared with modern stuff. This was a quick and dirty project, so I grabbed what was easiest to get to or to carry and ended up with the EPI's vs. Paradigm Signature 2. The EPI can be likened to the much more ubiquitous Small Advent Loudspeaker (but before the Advent), it was a good value product of the day, but nothing exotic, by any means. Keeping with the quick and dirty theme, I just used what was in my CD changer (some Linda Ronstadt and Yes, Close to the Edge - nether is a reference quality recording)

I must say, what I heard was absolutely astounding to me!

Of course the Beryllium tweeters of the Sig's had more extension, air and detail, but for bass, the acoustic suspension (sealed) EPI's seemed to totally spank the ported Sig's for resolution!

I had just assumed a top of the line modern speaker from a major manufacturer would beat 30 year old technology on all counts. Go figure!

Furthermore, the overall balance of sound from the EPI was competitive.

So, there it is, my one hour "slam dunk" comparo has now turned into a "next free weekend" project to set these up in my A/B test system and seriously determine how they compare!

That should not surprise you, as you have a couple of classics.

The AR3 will need some work. Likely refoaming of the woofers, recapping the crossovers, replacing the speaker level controls, and the tweeters. Improved updated tweeters, are available for the AR3. I did do an AR 3 restoration for a customer a while ago.

I would expect the bass to be better.

The cabinets are wider, so baffle step loss occurs at a much lower frequency.
This is at the expense of imaging, as there are more baffle reflections.

In a sealed enclosure, roll off is 12 db per octave rather than 24 db, so the is more low bass. The woofers are larger then on most of the speakers discussed in these pages.

All this means is that you don't have to suck the life out of receiver amps for the BSC, which on a lot of speakers is incomplete, so it does not suck the life out of receivers.

I have heard quite a few Paradigm speakers now, and have found them to be poorly balanced.

Both of the vintage speakers you have a much better balanced and more musical then any Paradigm speaker I have heard.

Your AR 3 speakers are well worth restoration.

 

[KEW]

Thank you so much for the link to a new tweeter! As many AR 3a's as there are out there, and knowing the tweeters were weak, I thought there must be a replacement available, but my search came up empty!
Can you also recommend replacement level controls?
I refoamed the woofers about 3 years ago, but never hooked them up.
Whether I keep them or not, I figure I'll get my money out of restoration and would far rather sell something which is very good. However, if the tweeters for the AR's works out well enough, I'll keep them and only sell the EPI's!

 

[TLS Guy]

Thank you so much for the link to a new tweeter! As many AR 3a's as there are out there, and knowing the tweeters were weak, I thought there must be a replacement available, but my search came up empty!
Can you also recommend replacement level controls?
I refoamed the woofers about 3 years ago, but never hooked them up.
Whether I keep them or not, I figure I'll get my money out of restoration and would far rather sell something which is very good. However, if the tweeters for the AR's works out well enough, I'll keep them and sell the EPI's!

If I remember correctly, they are 50 ohm wire wound pots, and I think you can get them from the same place as the tweeters.

 

[KEW]

What I found on that site are these two L-pads. They are both labeled as 8 ohms.

L-Pads

 

[KEW]

Thanks TLSGuy, for getting me re-enthused on this project. I found some good links for restoration of AR 3a.
Restoring the AR-3a | The Classic Speaker Pages
They recommend this as a replacement pot, so I think I'm good!
RHS15R - OHMITE - RHEOSTAT, WIREWOUND, 15OHM, 25W | Newark

 

[Swerd]

For what its worth, Dennis Murphy once published his frequency response measurement of the AR3a MurphyBlaster Productions

I recently restored a pair of the classic Acoustic Research AR3a speakers, circa 1970. The deep bass is still very impressive, but by modern standards, the crossover is pretty primitive, and that, together with the ad hoc driver placement resulted in severe cancellation modes in the mid-highs. The woofer also had a big hump at the top of its range, which colored the sound. Still, it sounds better than you might think.

 

[3db]

For what its worth, Dennis Murphy once published his frequency response measurement of the AR3a MurphyBlaster Productions

So a flat frequency response isn't necessarily a good thing subjectively speaking?

 

[KEW]

For what its worth, Dennis Murphy once published his frequency response measurement of the AR3a MurphyBlaster Productions

Thanks.

That is a little perplexing because I remember seeing much better FR curves when it was still being sold. Am I correct in saying they were not smoothed if the plots had sharp corners?

Here are two measurements referenced by an Audioholics article showing AR's research involving the 3a.
Identifying Legitimately High Fidelity Loudspeakers: Power Response & Baffle Step — Reviews and News from Audioholics

The above curves of the famous AR-3a from 1968 clearly show that. In the top figure, the 3a is in a pure 2 Pi environment (“bookshelf,” surrounded by books), and its LF-to-midrange response is smooth and predictable.

Welcome any comments on this!

 

[KEW]

Maybe a partial explanation lies in the last sentence of the page linked above:

So all those near-field considerations like driver alignment, cabinet diffraction, phase relationships, etc. are far less important in real world listening conditions than their theoretical importance might suggest.

 

[Swerd]

So a flat frequency response isn't necessarily a good thing subjectively speaking?

That is a little perplexing because I remember seeing much better FR curves when it was still being sold. Am I correct in saying they were not smoothed if the plots had sharp corners?

I wouldn't make any major conclusions based on these different FR curves, other than they were made by methods that may have had little in common.

• One was made in 1968 and the other was done in the last 10 years give or take.
• There almost certainly physical differences in the room and measuring hardware between these two measurements.
• I am 100% certain that there were software differences.

There were likely other method-based differences too. For example, I assume Dennis Murphy made these FR curves similar to others I have seen him perform – the speaker was mounted vertically on a stand out in the middle of a room with the test microphone about 1 or 2 meters away, mounted on a boom stand. The 1968 AR curves may have been done with the cabinet mounted horizontally. That could account for several large peaks and valleys that Dennis got and AR didn't.

Dennis usually avoids curve smoothing. He would probably say why do the measurement if you want to mask the results.

Some of the large valleys in his "Room Response" curve are due to lower frequency room reflections. It starts at 20 Hz. The "On-Axis Anechoic" curve doesn't go lower than 200 Hz.

The two AR curves clearly show what "baffle step response" looks like. Compared to Figure 5 (the speaker is essentially mounted in-wall), Figure 9 shows the FR curve steps up beginning at about 300 Hz. If you listened to it standing out in the open, the bass below 300 Hz would sound puny and weak in comparison.

 

[KEW]

Dennis usually avoids curve smoothing. He would probably say why do the measurement if you want to mask the results.

I didn't mean to imply Dennis smoothed his curves.
The question I was posing is "Is it correct to believe the curves AR made in '68 had little or no smoothing based on how jagged the lines in this plot are".
On reflection, there probably wasn't much curve smoothing. That would wear out a slide rule pretty quick!

 

[AcuDefTechGuy]

I have heard quite a few Paradigm speakers now, and have found them to be poorly balanced.

Although Paradigm measure very well, especially the Signature series.

 

[TLS Guy]

What I found on that site are these two L-pads. They are both labeled as 8 ohms.

L-Pads

You are relying on an old man's memory.

I'm pretty certain the pots were higher than 8 ohm, so the 25 ohm ones should be fine.

 

[Swerd]

I didn't mean to imply Dennis smoothed his curves.
The question I was posing is "Is it correct to believe the curves AR made in '68 had little or no smoothing based on how jagged the lines in this plot are".

And I didn't mean to suggest that Dennis or AR added smoothing to the curves. I know what Dennis usually does. I can't speak for AR in 1968, but considering the absence of computers that can add smoothing with a mouse click, I doubt if they did anything intentional that reduced their resolution. In those days, curve smoothing was done by switching to a dull pencil.

On reflection, there probably wasn't much curve smoothing. That would wear out a slide rule pretty quick!

LOL

AR's FR curves actually look rather good. I wondered just how they could have done that without computers and their built-in iterative calculations and Fourier transforms. Did they run a continuous sweep of frequencies and record the sound without any data processing? I wonder how long it took to generate one good FR curve?

I know that Dennis's PC generates a series of white noise pulses that get converted to analog and are sent out to the speaker. The microphone picks up the sound, the computer digitizes it, and processes it to the FR curve we see. It all happens nearly instantaneously, and no slide rules are harmed in the process.

 

[KEW]

I wanted to re-emphasize, the thing that shocked me was improved resolution of bass - not the extension.
The EPI's I listened to have an 8-1/4" woofer.
I definitely want to hear these in a better A/B scenario With more time to figure out specifically why I heard such a difference. I set this up in a smaller spare room. It may be that the Sigs played lower and excited a room resonance that obscured detail.