DVDs with digital audio soundtracks didn't arrive in the US until the Summer of 1997. Until then all surround sound receivers used Dolby Prologic to extract surround effects from stereo analog sources like video tape and television. Forgotten today is that rear channels of the Prologic effect only produced thin, ambient sound. As a result, the receivers of the era might supply 50-100 watts to the front speakers, but the rears channels were limited to 25 watts max. Even the Yamaha RX-V0170 which was the flagship surround receiver of the era at $1300 msrp only supplied 30 watts per rear channel. As a result the surround sound speakers sold by companies tended to be small, poor quality and with low 87-89db/watt sensitivity. Typically they were just small bookshelf speakers that companies craftily renamed to take advantage of the surround sound bandwagon. So when Dolby Digital appeared on DVD with six dynamic full-range channels it made the fragile, lightweight, surround speakers on the market obsolete overnight.

Klipsch came to the rescue and in 1999 released the RS3 which used a two 1" Tractrix horn tweeters and a single 6.5" woofer. Response was listed as 49-20khz with a sensitivity of 95db/ 1 watt.

In 2001 Klipsch upgraded the speaker to the RS3 II which is said to have been one of the best selling surrounds in the US. The sensitivity (95db), woofer and tweeter sizes were the same as the RS3 but the response was narrower at 60-20khz. The cabinet dimensions were the same as before and at nearly 19 inches wide and at 12 pounds was very large for the period.

In 2003 the RS35 appeared. Advertised features were "Very high sensitivity and power handling" and "180° dispersion". Peak power had increased to 500w and response was a tighter 81-20khz with 97b efficiency. The tweeters and woofer were the same dimensions as before but the horns were smaller in diameter. The cabinets were smaller at 15.75 inches wide while the weight dropped to 9.6 pounds. The smaller size and weight made it easier to mount on the wall or put on rear stands.

In 2007 I bought a new pair of RS35s which I still use in my 7.1 home theater.

The tuned ports increase bass output

TWEETERS
Over the years Klipsch has used both Titanium and Aluminum 1" dome tweeters in their Reference speakers. It has been said that Klipsch typically used the same tweeter voice-coil across several models. This practice is common for speaker companies and makes good business sense. Tweeters only receive a few watts even at very high volumes and don't carry as much information as the midrange and woofer. This means that within a speaker series there isn't a valid reason for a company to use different tweeters unless truly necessary. This would explain why there are several similar Klipsch 1" tweeters from this period with slightly different part numbers. It appears that Klipsch simply changed the tweeter faceplate depending on the mounting flange needed for a particular horn. Luckily, Klipsch added a feature which identifies the ones used in high performance models: a heat sink.

Each RS35 uses two K-137 1" Titanium dome horn-loaded tweeters and I recently noticed that one tweeter had lower output than the others, I must have clipped it over the years. Electrically all four tweeters measured 5.6 ohms DC but something was wrong on the bad one. Yet Klipsch didn't intend this tweeter to be opened for inspection: the voice-coil was epoxied in at the factory. I saw no way to take it apart without ruining it.

Replacement K-137 tweeters were scarce even back in 2006 and have long been unavailable. However, in 2025 I saw a Klipsch tweeter I thought could work as a replacement: the 1" Titanium #1011956 said to be used in the RS-52/42 II surround and RC500 center. These speakers are rated up to 500 w peak with 96db efficiency giving this tweeter good provenance.

My stock K-137 measured at 5.6 ohms DC, the #1011956 at 5.4 ohms DC. The magnet on the #1011956 is a slightly larger diameter as well. I reused the horn gasket from the old one and it bolted identically into the RS35 horn. Despite the RS35 being "8 ohm compatible" from the speaker jacks it measured 3.6 ohms while the repaired speaker was 3.4. Playing a variety of full-range recordings I was unable to detect any difference between original and new tweeter in volume, voicing or timbre. With the tweeter restored my room feels more balanced and the soundfield is more coherent and accurate.

BELOW: Typical for Klipsch is a heavy duty crossover compared to the simple ones used by other brands of the period. The cap on the top is a 28uf 100V 5% metalized polyester cap with a 3 ohm 10W resistor and air coil.

6.0uf and 1.5uf 100V 5% caps and iron core coil are on the lower level.

4 LAWS OF THE KLIPSCH UNIVERSE   High efficiency with low distortion Wide dynamic range Controlled directivity Flat frequency response   - Klipsch website 2025

As an example of their 4 Laws, ten years ago Klipsch sold the matched "RF62" speaker package. Every speaker (Front, Center, Rears) was rated at 97db@1W. But several years ago highly efficient surrounds were mysteriously dropped from their lineup. Of the remaining three, the RP-502SII is 94db while the RP-500SA and R-40SA sensitivity is not rated. Klipsch still sells bundled 5.1 speaker packages but the surround speakers included have de-evolved back to small, inefficient bookshelf speakers(!?) I find it very puzzling that Klipsch continues to sell highly sensitive front and centers (97db+) but chose to only downgrade their surrounds. Why the mismatch? I suspect the intent is to alter the model of home theater to focus on Atmos, smart TVs and Soundbars. The key question is who is actually driving the direction of modern home theater. Is it the hardware companies who produce speakers and electronics, Dolby and DTS, the streaming industry, or something else?

Klipsch holds the patents to their own designs and is losing an opportunity here. Instead of focusing only on Atmos, if they reissued a surround speaker with an output of 97db/1W for the countless 5.1/7.1 systems still out there it would redominate the market. This would also create a product for the Heritage speaker owners who seem completely forgotten when it comes to matched home theater speakers. Perhaps they are worried that once people get a taste of efficient surrounds they won't want to buy lesser models. A race to the bottom is always wrong.