I've heard this effect before. It sounds like a "tinkling" sound as the tubes warm up. I don't hear it with my current amps (or recent amps) but did in the KT-90's in my converted Luxman MB3045 amps I have more than 20 years ago.

Just sounded like thermal expansion.

I'll probably pick up a pair of 6L6-somethings at some point to try out. Maybe a 6P3S-3 or a Sovtek 6L6WGC (the first cousin of the 6P3S-e) or 6L6WXT+ or something like that.

What I would really like to hear would be a pair of KT-150s. I keep reading about how much punch and definition these have.

Don't know if I will try any 6550, I like my KT-88 a lot. Not convinced that any 6550 would sound better. Many high-end manufacturers have moved away from 6550 to various KT-type tubes.

Unfortunately an unexpected change of resident (my leased condo sold out from under me) and an upcoming lengthy vacation, will mean that after tomorrow, my amp will be going into storage for at least 6 weeks.

What he said. It isn't an issue. Thermal expansion is unavoidable and as long as it doesn't enter the audio chain just ignore it and know that your tubes are "warming up".

I have all 3 but keep coming back to the black bottle. The UK is a nice tube for the $$. The grey bottle has the most detail. The black is more full sounding. I have old production too but they don't see much use. YMMV.

Well, I don't purport myself to be a speaker expert, although I have a fair amount of hard won knowledge in the Altec realm. Anyways, to the best of my understanding, OB speakers have the advantage of the dipole effect, at least in any driver that's open to the rear as most woofers are. I have a set of Infinity RSIIb's that also ports some of the EMIT/EMIMs to the rear as well. They require placement away from walls to sound their best. Here's a nice summary from the Linkwitz Lab website

Open baffle speakers are inefficient in terms of the mechanical movement that is required to create a given level of sound. This not only applies to speaker cones but also to panel vibrations.


•Open baffle loudspeakers reproduce bass with less room interaction. It is more articulate than from box speakers.


•If dipole behavior covers the full frequency range, then the room response becomes perceptually masked by the direct sound.


•The radiation from the rear of the cone must not be absorbed, but the distance to the nearest reflecting/diffusing surface should be at least 3' (1 m).


•An open baffle circumvents the box problems of delayed radiation through cone and enclosure panels. They occur typically in the mid-frequency range and are difficult to suppress.


•Large panel radiators or long line radiators suffer from severe lobing at higher frequencies. It manifests in critical room and listener placement.


•Even though a dipole requires a 6 dB/oct boost towards low frequencies, it takes little power to drive it to maximum excursion at its lowest bass frequencies. Amplifier power could be an issue as frequency increases, where it requires higher cone acceleration to reach Xmax. Thus SPL is limited by driver volume displacement at the very lowest frequencies and becomes amplifier limited as frequency increases.


•Realistic bass levels can be obtained from dynamic drivers in open baffles, not from panels. For extreme SPL requirements the number of drivers could get very large and, therefore, below 50 Hz they are more economically replaced by sealed box subwoofers.


•At frequencies where a 8" driver would become directional it has wider frontal dispersion for an open baffle than if the baffle were closed in the back.


•Open baffle speakers reach deeper into the room and are less subject to the room response if their polar response is well behaved.


•ORION exemplifies open baffle loudspeaker design in terms of polar response control and dynamic range. It circumvents the limitations of large panel radiators and yields a small package.


•The low masses of the moving parts in an ESL, a planar magnetic, or a ribbon driver are necessary to generate useful sound pressure levels. The force generated by an electrostatic or planar magnetic motor is weak. Since SPL is proportional to air volume acceleration, and moving parts Acceleration is Force divided by Mass, the mass has to be lower if the force is too weak to generate sufficient acceleration. Furthermore, since excursion is limited with these drivers the radiating area has to be large to move a sufficient air volume.. These relationships seem to be difficult to grasp by audiophiles. Marketing departments and even some designers like to tout low mass as an inherent benefit giving greater "speed" or frequency response to their speaker, when it is only affecting sensitivity in SPL/W.


•It is difficult to screw up an open baffle speaker design to where it sounds worse than your typical box speaker.




The Inspire OB speakers sound wonderful in a relatively small space, perhaps 12' x 12' in my estimation. Of course this is a function of the room's acoustic properties, placement, source material, and of course, the upstream electronics.


I have no opinion, since I am unfamiliar with these speakers.

How do you define affordable?

I've been chasing good horn speakers for quite awhile, and as previously mentioned, am partial to Altec. However, if you can afford $250-$500 I would look for a set of Frazier Mark V's with the horn, not the bullet tweeter, a set of Klipsch Forte IIs, or possibly a cheap set of Cornwalls. Altec Boleros are also reputed to be very nice, but I have no personal experience with them. If you can swing up to $1000, I've bought Altec Model 19's and two pair of Altec 604-8Gs for this amount. Occasionally you can find Khorns for the same amount. My Khorns sound sublime on a SET 45 amp and Citation IV pre amp...

I hope to be able to make it. Originally I was supposed to be at the beach, but that trip may be postponed. Given some lead time, I should be able to bring a wide selection of tubes. Fair warning though. Dennis and I tend to sit and listen to the same three or four songs over and over again, since we know these tracks by heart, and use them to evaluate differences in tube sonics. Also, make sure to remind him about your amp at least three to four days in advance so that you can hopefully ensure it's presence upon your arrival....

Thanks for the input, just what I was looking for!

The 'CV-181' tubes are all quite good. ice lake audio and h salience is where they came from. Good vendors. Be sure you are getting premium grade on the black and gray.

So,
If you had to pick one Altec system to hunt down for a moderate sized room, 19x15x10.5, what be your choice. Have always been intrigued by the idea of trying an older horn system but wouldn't know where to start looking.

CoGT3.......You may want to consider the Altec Valencia. I owned a pair for nearly 10 years that I powered with a McIntosh MA230 integrated amplifier, solid state preamp with 30 watts per channel tube power amp. I never had to drive the MA230 hard to get room filling volume. The Altec Valencia is a fine speaker and looks good, too.


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