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Realistic Optimus 21/ ADS L620 Comparo

Stuart Pedaso said:
My Optimus-21 aren't convenient to access just now, though reverse calculating from published "46 square inches" of cone radiating area gives the effective diameter of 7.65 inches. Tandy may have used cone diameter inside the surround for this calculation. :dunno:

Marketing does play fast and loose with speaker size. This is a 3016Aa used in Optimus-5B and Nova-8B and described as a 12 inch woofer.

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It's exactly 11 inches across the basket, 10 inches outer surround diameter and the cone diameter is just 8.5 inches inside the surround.
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I guess they measured corner to corner. :biggrin:
Other brands of speakers I've had and have measure close or right on to the specs given, measuring the surround diameter.
It does seem RS played fast and loose with some of there measurements.
 
I need to bring out the ADS L620s and see how the 21 compete. If I do it in the next few days I will measure the woofers to see how ADS classified a "10" in woofer.
 
I got the caps for the 21s yesterday. I will see if I can get off my lazy ass and get them recapped today.
 
Good deal. The last few parts finely showed up so I can try and finish that preamp I'm building. Ill.be getting to it a little later o e the coffee kicks in.
 
Lavane said:
Good deal. The last few parts finely showed up so I can try and finish that preamp I'm building. Ill.be getting to it a little later o e the coffee kicks in.
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Our freaking dogs wake our happy asses up about 5 every morning.....I am on my second round of caffeine about now.
 
OK! I got the 21 recapped this morning. The new caps are yuuuuge compared to the old ones as can be seen in the pictures below. I have recapped about 18 sets over the years and all of the ones I have done have sounded different.......but in the vast majority of them the difference has been small. The biggest difference, and improvement were the Nova 8Bs I did a couple of years ago. They went from sounding ok to WHAM! These 21 went from sound pretty darn good to pretty freaking good! The highs are clear and more detailed than before. The bass was already tight and fast so no real change that I can tell.

For peeps that dont think vintage speakers can sound anywhere close to new ones, or just really damn well, they need to hear them with fresh modern caps.

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Oh, I used the weird Alien nano tape to hold the caps down. The stuff strange but it really works well and is easier to use than glue.
 
I wrestled out the ADS L620s so I could do an A/B comparison with the 21s. I made sure to stand at ear level (since the 21s are on top of the 620s and that gives them an advantage) to listen to each and tried to judge each in soundstage, detail, midrange and bass. Here goes:

With the 21s ability to set up which side a speaker is on, the soundstage is a bit wider than the dome tweeter ADS'....but both have a really nice soundstage.

For detail the Realistics win hands down. I have the HF comp switch in "high" and the ADS speakers have not been capped but I was surprised at how much better the detail was in the 21s. I never thought the ADS speakers needed to be capped but now I think I will do it.

Midrange is also a win for the 21s, they just have a fuller midrange.......similar but not quite up to the sometimes overwhelming mids in the Nova 8Bs. The ADS' seemed like they were a bit empty.

Bass is a draw at the volumes I listen to. Probably at extreme volumes the 620s would out perform the Realistics. I expected the ADS units would smack the 21s in this area but they did not, yet another surprise.

@Lavane and I have talked about the subject a lot over the years of how simple the Realistic crosovers are and what cheap caps they used when new. The 21s crossover is a bit more complicated than usual since it has the changeable mirroring but it is still really simple. Put on some good quality modern caps and WOW they sound very modern.

A size comparison between the two. BTW both have really nice walnut veneer.

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Interesting review. I own a pair of the 620’s and think quite highly of them. They are not anywhere close to being my main players but are very good for what they are. I have not personally listened to every vintage 10” 2 way but I have listened to many and have owned more than a few . IMO, I have heard none better than perhaps the BA A-100’s. I also own a very good selection of 10” 3 ways including the likes of Yamaha 670’s, AR 92’s, JBL L80t’s, BA A-150’s, Ohm C2’s. The ADS 620’s give away very little. I am also quite confident they dig a bit deeper than the 58 hz the 21’s are rated for. You mention you have a large bedroom with the speakers mounted in the corners, how far apart? How far is your listening position from the center point of the speakers? What does the manufacturer recommend? Placement and following manufacturers recommendations has as much or more influence on the sound than the speaker itself. If placed outside of the manufacturer’s recommendations, IMO, this should be noted in a review. Along with musical genre for the comparison. Big difference in whether someone is listening to soft jazz, chamber music or hard rock. Here is my placement when listening to my 620’s, driven by rebuilt Kenwood or Sansui power, moderate volumes playing classic rock, classic country or outlaw country. They sound very little like yourIMG_1851.jpeg review.
 
blademan13 said:
Interesting review. I own a pair of the 620’s and think quite highly of them. They are not anywhere close to being my main players but are very good for what they are. I have not personally listened to every vintage 10” 2 way but I have listened to many and have owned more than a few . IMO, I have heard none better than perhaps the BA A-100’s. I also own a very good selection of 10” 3 ways including the likes of Yamaha 670’s, AR 92’s, JBL L80t’s, BA A-150’s, Ohm C2’s. The ADS 620’s give away very little. I am also quite confident they dig a bit deeper than the 58 hz the 21’s are rated for. You mention you have a large bedroom with the speakers mounted in the corners, how far apart? How far is your listening position from the center point of the speakers? What does the manufacturer recommend? Placement and following manufacturers recommendations has as much or more influence on the sound than the speaker itself. If placed outside of the manufacturer’s recommendations, IMO, this should be noted in a review. Along with musical genre for the comparison. Big difference in whether someone is listening to soft jazz, chamber music or hard rock. Here is my placement when listening to my 620’s, driven by rebuilt Kenwood or Sansui power, moderate volumes playing classic rock, classic country or outlaw country. They sound very little like yourView attachment 3135446 review.
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The speakers are about 21 feet apart toed in to put the sweet spot in the middle of our king size bed. Any speaker in these systems have great bass.

The 620s are great speakers and I really like them. My surprise was that the Realistics stood toe to toe with them.

My current crop of 10 in units are Marantz Imperial 6, Nova 7B, OLAs, Optimus 21 and the L 620s. I recently have gotten rid of Polk Monitor 10s and 7Bs .

My favorites by a hair are still the Imperials, especially at the volume I listen. But all of the ones I have now are all great speakers. They all sound a bit different with none standing out that much.
 
Oh, about "manufacturers recommended placement"; this is not a scientific review and since both companies that made the items in this review are out of business, getting such specs is problematic.
 
I would really like to find a nice pair of Imperial 6’s but they are quite hard to come by. Can’t say I have ever heard a bad thing about them.
 
blademan13 said:
I would really like to find a nice pair of Imperial 6’s but they are quite hard to come by. Can’t say I have ever heard a bad thing about them.
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I have better speakers, but my Imperial 6's ain't going anywhere.
They're so easy to listen to, sound great and even sound good at low volumes without tone controls or a loudness control. They do great with SS or tubes too. I have mine connected to a small 17wpc tube amp. Its a great combo.
 

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My Imperials live in my front system. My new Marantz 7025 amp and 1990 vintage Kenwood pre and tuner are a great match for them.......but then I have never heard them NOT to be a great match for any system. Easy to drive but they love power as well.

The 21s image better, but not by much. The Imperials take them on bass however. The Imperials are just so freaking competent in all areas,

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