Reverse Polarity on K-Horns?

[carlabarla]

My parents' system consisted of Klipschorn speakers with a Dynaco ST-120 solid state amplifier and a Crown IC-150 preamplifier. This system sounded satisfactory to all concerned for about 20 years. Then one channel of the Dynaco died. Rather than having it fixed, I decided that they needed to upgrade to a Rotel RB980BX amplifier. The sound was immediately worse, but the most obvious problem was a hiss coming from the Crown preamp and amplified profusely through the Rotel/Klipschorn combination. I sent the Crown back to the manufacturer to be refurbished. They sent it back and said it was now perfect. The hiss persisted. I bought a Rotel RC980BX to replace it. The hiss is now gone, but the Rotel preamp has no "loudness" button, and no tone controls to tame down any harshness in the upper midrange/vocal area. The K-horns now sound shrill like they never have before, have no bass, and my Mom won't forgive me, PLEASE HELP! I am actually thinking about having the Dynaco fixed and putting the system back to its original configuration. My Mom would never spring for a good SET amp.

Footnote: Someone please explain why when I reversed the polarity of the speaker wires, the K-horns immediately sounded better (i.e., more full bass). In my estimation I have the speakers hooked up backwards, but they definitely sound better?????

[lynnm]

It sounds to me as if , (notwithstanding the reservations about the ST-120of some others in this forum), that the ST-120 has been the most satisfying match for those horns in that listening room. Remember too that this amp had supplied satisfactory service for 20 years. It is difficult for people to switch from 20 happy years of a particular sonic character and then find themselves comfortable with anything different.

Regarding the wiring question I think that you had managed to get the horns out of phase at some point. If the speakers are not properly phased the result will be loss of bass response, a severe degradation of the stereo image and an apparent loss of balance between the bass and midrange drivers - ie the mids may sound unnaturally loud in relation to the bass drivers - which could be interpreted as stridency particularly if the speakers are being driven by an amp that leans a little in the direction of having a slightly hot mid.

It may best to get the ST-120 repaired and mate it back up to the Crown thereby restoring the system to its original configuration. It is maddening but true that sometimes really good components are not always the best match for other really good components and that certain combinations of less than ideal components can sometimes sound better in a particular environment..

[sunnysal]

I think most people would not recommend repairing the ST-120. I had one and I could find no one (ethical that is) willing to fix it due to the fact that it really, really is quite inferior to most newer SS stuff out there. I suspect that the dynaco's somewhat rolled off highs and loose bass combined to make a pleasant sound for you and your family. the newer components have greatly extended frequency extremes and probably tighter bass. to recreate the old sound is going to require either equalization (boost some of the bass frequencies and roll off the highs a little) or an amplifer/preamp combination that does the same thing somewhat for you. what is your budget? you might be able to keep the rotel amp (it is a good unit) and handle the tone control via a new preamp or the addition of an equalizer (does the crown have a loop that could accomodate and equalizer?) regards, tony

btw I agrre with lynns assesment that you probably had the k-horns wired out of phase for a long time.

[artto]

I agree with lynnm. You probably got the polarity mixed up somewhere along the line. And the result would be something akin to what lynnm said.

Its possible that when the Dynaco died, it sent a voltage or current spike backward into the Crown. Something similar happened to me on my bass rig when the preamp section of the bass amp blew. It took out one effects unit that preceded it & "froze" the harmony machine/effects unit which preceded the other effects unit.

I've seen a number of posts in here using Rotel gear. I've never thought much of Rotel. Maybe things have changed over the years as I'm now moving away from playing pro & going back to more "listening" again after many years.

I used to have a Crown IC150. I switched over to an Audio Research tube preamp back in the early 80's. The following is from the Crown IC150 manual:

"The problem of noise can be compounded by the unfortunate truth that power amplifiers will indiscriminately amplify noise along with everything else. If the final amplifier stage of your audio system adds 30Db of gain to the signal, it also increases the noise in the signal by 30Db, which may bring the noise level up to an annoyingly audible level. To make the best of this situation, it is a good idea to keep your power amp below full gain, and provide as of the level as possible with the preamp.

Also in the Trouble Shooting section under High noise or hum:

"(1)Power amp turned wide open (2) Poor connection is associated wiring (3) Ground loops between IC-150 & associated equipment (4) Open ended inputs (ie: shorting plugs removed without having put any input from tuner, phono, etc.)"

RE: Number 3. Ground your system at only one point. Everything else should be using polarized 2-prong plugs (use adapters if you need to) to float the ground levels. The ground will seek its own level. This will help avoid any ground loops between associated equipment.

RE: Number 4. Crown recommended that the IC-150 use shorting plugs on unused inputs to reduce noise. Have the shorting plugs been removed?

The Dynacos never bothered me that much although their older tube equipment is probably more desirable & a better match for K-horns. Rotel? Like I said, Ive never been impressed with their offerings & I dont think they mate well with something like a Klipschorn. But, as we all know, everyone hears things differently, so to each his own. And I concede its been many years since Ive listened to any of their equipment. The Crown IC-150 is known to be a somewhat bright, sometimes edgy sounding unit (which is probably why it seemed to mate well with the Dynaco 120 with its "somewhat rolled-off highs & loose bass" that sunnysal mentioned) . Although its a very quiet unit, even by todays standards. And forget the idea about equalizing anything until you get the noise & polarity problems solved. It will just increase distortion as you try to compensate with additional gain to overcome the cancellation of bass frequencies caused by out-of-phase speaker polarity. And rolling off the highs will not accomplish much for getting rid of the recent noise you have encountered without getting rid of some of the music as well.