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Seas tweeter conversions - head to head

Posted by Bold Eagle (A) on July 11, 2015 at 14:06:41

This will probably be my last post on this subject, as I think I've pretty well beat it to death.

Anyhow, I got out my A-B switching box, connected up my second pair of matched cables, and ran side by side comparisons on the three pair of speakers I have (SEAS 27TBFC/G & SEAS A26RE4 in an Advent cabinet; SEAS 27TBFC/G & 25F-EW in a JBL L-110 cabinet; and SEAS 27 TDFC & KLH 17 woofers in a KLH 17 cabinet). In each case it was one of the others Vs the Advent boxes. The Advents are on 15" stands, so the others were set on something to get the tweeters at the same height.

The results? The Advents and JBLs sound nearly identical. The Advent cabinets are Acoustic Suspension (sealed and filled), and the JBL boxes are ported and partially filled, so the bass is very close, and the mids and highs sound identical to me. Except that the imaging is a little different because the Advents are a mirror imaged pair, and the JBL's have the drivers mounted closer to the right side in both cabinets. So when you switch, the center image jumps over a little. I find that the JBL's always worked better with more toe in on the right hand speaker.

The Advents Vs KLH 17's did show some differences. The mids are pretty close; but the tweeters are a little different and that is audible as a subtle difference in piano, female vocals, and percussion like the hammer dulcimer. The biggest difference is the lack of authority in the KLH bass when they are up on stands, and that makes the balance a little thin. They do better on the floor or on low risers; which is how I used them when I first got them. The Advent and JBL cabinets with their significantly lower bass tuning have a better overall balance.

In closing, I'd like to explain why I have used the L-110 cabinets for this. The fact is, the woofers were swiped when I sent them out to be refoamed over 20 years ago. Since then, I have tried a number of different woofers with only moderate success. Then one of the JBL 033 tweeters died. They are no longer available, so SEAS tweeters were adapted. By that time, the crossover was changed, and only the midranges were JBL. Sound was OK; but not great. At that point, I disconnected the midrange and tried them as a version of the Dynaco A25XL with SEAS 25F-EW woofers and SEAS tweeters. That was a noticeable improvement. Back when they were configured as a 3 way with SEAS 25F-EW woofers, JBL LE5-10 mids and JBL 033 tweeters, E-Stat visited me and we did a listening session with my mirror imaged and crossover modified Original Advents, and then the JBL's with the SEAS woofers. He noted a lack of coherence due to a sudden change in directivity between the midrange and tweeter. That crossover point was about 4500 Hz, and that's too high for a 5". Turning the speaker into a two way with a relatively low crossover actually improved the coherence and gives a seamless transition between woofer and tweeter.

Jerry

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