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.


https://i.ytimg.com/vi/zPzXpHJga_k/maxresdefault.jpg

Well, it would come down to more of an availability issue IMO. I find that the Model 19 and the 604-8G's are very close in their sound. I had them set up head to head in a small room in my old house, on the order of 12' x 12', and the 604s came out ahead in this size room because they had slightly more coherent sound due to their "point source" configuration. For your size room, the Model 19 might be a little better, due to improved cohesiveness of the two way design at listening distance. However, I'd take whichever I could find first after a hard listen. There's nothing wrong with Vals either, but they have less of a high end than the 19's, due to the 806A compression driver as compared to the 19's 802/902 driver. The 19s were considered Altec's pinnacle for home speakers, while the 604s were the studio reference monitor for decades.

http://i443.photobucket.com/albums/q...c/CIMG7998.jpg

Note that the use of an 828 cabinet for 604s isn't typical, but actually works pretty well in practice.

Funny story, I had the 19s in the dining room first, then added the 604s/828s when the wife wasn't home. It took her 5 days to realize that the 19s had grown a new head. Needless to say, we didn't actually eat in the dining room much.....

My wife is pretty accepting but I do think that would push it a bit far. Thanks for sharing. I am celebrating my 10 year anniversary today and this makes me wonder if after 10 years I could push the WAF a bit further.

You never know until you try. Tis better to beg for forgiveness than ask for permission...

The Altec Valencia is often recommended, but the 511/811 horn is generally considered to be one step better than dog poop. The 416 woofer also needs to be crossed over less than 1200 hz to avoid HF nasties.

A lot of people - including Joe Roberts and Joseph Esmilla - believe the Altec 414/802 combination is best suited for domestic use. The 414 works with vented cabinets of 3-4 cubic feet, and in most rooms the Altec 614 cabinet will work. The 802 can be used on a number of horns, but a lot of people like the Altec 32A or 32B horn. Joe Esmilla has a well developed crossover design for this combination in two forms: a two way and a high-pass only that allows the 414 to run full range. Alternatively, Joe Roberts advocates letting the 414 run without crossover and using a single cap to cross over the 802 at 6-8khz. You'll need an lpad, autoformer or other means to pad down the 802 by 3-6 dB.

Full disclosure: I just finished gathering parts for such a set up. Even buying used and scavenging it is not an inexpensive project. If I recall correctly, I have about $1,400 in parts, not counting wire, binding posts and cabinetry. However, the closest commercially available (if you want to call a speaker made from vintage parts "commercially available") is the Shindo Petite LaTour, which retails for over $20k. I figure by the time I'm done I will be into the speakers for about $2,500.

There's a pair of Altec Valencia speakers for sale on CL in my area. They look near mint. Using a 602d 15".

I listened to some big Altecs some years ago and they weren't my cup of tea. More recently I had a chance to listen to the 879A Santanas and they didn't stir my drink either, although I understand that they tend to not be very highly regarded. They did have the original 420A drivers and bi-flex cone. Guy sold them off for just $225.

On the whole, I've never been a big fan of horns. Even the K-horn. But I did hear a setup a few years back at CEDIA using horns which sounded very good. I've since forgotten which brand they were. I still remember what they looked like, a big horn and a tweeter horn, all painted in primer gray.

Unless horns are specifically designed for the domestic environment it takes some dedicated modification to make them work. Bear in mind that most big horn (Altec, JBL, et al) were designed as theater speakers or for sound reinforcement. In other words, they were designed for fill big spaces with high sound pressure levels. They don't usually work out of the box for a 200 square foot room. There are a lot of sources on the 'net on how to make them work, but it takes an investment of time and money, mostly in selecting the appropriate crossover implementation.

If you're not looking for that level of commitment, Klipsch products were typically designed principally as domestic speakers. While the quality of the drivers (and horns) is not up to that of Altec, they work very well when tweaked. A successful design is Bob Crites' Cornscala design, which combines the 15" vented bass of the Cornwall with the LaScala mid and top end. There are four different configurations and they reputed to work very well.

Edgar horns? Horns have to be done right or.....:sigh:

How much are they listed for?

I putzed around with Bozak 302A's in the past. My anti-high end phase. Not for me.


http://i66.tinypic.com/32zj6ep.jpg

PWK and Rudy Bozak. They were at a trade show and this was a publicity shot.

So, in general terms, horn-based loudspeakers for smallish listening rooms are either too expensive or vintage needing a lot of work to adapt them to specific needs and requirements.

I guess 45 SET dreams are out of the question ...

Thanks for the information!

All those horn-based alternatives are out of production (vintage). What about new ones like Klipsch Heressy III or even Cornwall III? The idea of having a competent 102+ dB sensitive pair of speakers is appealing if one is interested in exploring the realm of true DHT SET's. Zu Audio's Soul at 99 dB's looks interesting and affordable (somewhat) but what if at the end of the day these turn out not SET friendly either? I know Omegas are not SET friendly as these never go above 95 dB's (even if their crossovers are lenient).

The rest of the ones I've seen in the marketplace are really expensive. The Klipschhorns seem too massive and expensive for my intended application also (new ones are unaffordable whereas vintage require lots of ugrading investments which a neofyte like me would not even know where to start)

Yep, it seems this DHT SET business is taking me nowhere and I'm too old already to start learning a DIY trade. Maybe I should stick to the Beam-Tetrode strapped as a Triode and call it a day. Dennis's stuff sounds wonderful anyway, so I guess I'm just wasting my and your time with these crazy thoughts. Sorry!

BTW, I understand the physics involved in those OB concept statements, but that is not what I had in mind. I need testimonials from real-people having hands-on experience using OB's and recommending (if at all feasible for my application) a current market offer deemed suitable. My Tekton Lore 2.0, (not the other models) are particularly good in my setup, just not SET friendly as much as I thought and I was thinking maybe an OB would improve on these, but seeing their rated sensitivity (in general) there may not be many high sensitivity alternatives around either.

Finally, I may need to concentrate in a wonderful set of subwoofers to replace my aging single Velodyne to assist my gear in yielding better bass and dynamics. Of course, replacing speakers for me is very expensive given logistics costs (about a 50% mark-up over a nominal $1,000 set of speakers, more or less).

I apologize for my ramblings, you have been quite helpful and patient. Thanks!

Crossovers are not a factor. Most of his speakers are single driver. He has started with a 1.5 way with two drivers. One driver is full range and has no crossover. The other only has a 500hz low pass filter. His single driver Alnicos are 8 ohm 95db, but these 1.5 ways are 4 ohm 99db. I would be going this route if I didn't already have my active two way, two cabinet system from him (with Rythmik woofer and plate amp).

Trouble is, they are getting expensive.


I can relate living in Alaska! What makes your logistics expensive?

They add bass and midbass, but don't expect higher overall output with your tube amp.

The Super 3i's (93/94.5?) with 2 watts (EL84 set) was more than plenty for me.

The design would at least help with added dynamics I would think. I can't recall, did you have 1.5's or have a chance to hear them?

I've got the KT-150 SEP but, even when running tubes that give five wpc, I never found it lacking with SAMs (similar sensitivity). The WolfEar Audio Kitoki SET with EL-84's was fine also at 1.5wpc.

Take a look at the First Watt products page amplifiers rated outputs into 8 ohms and 4 ohms.
Which ones do you think might benefit from a 4 ohm speaker load?
All of them or just some of them?

As far as FW goes, and given the same speakers either way, the answer is some. The question though, is what happens with Inspires when given 8 vs. 4 ohm load?

Also, there is the increase in sensitivity along with the reduction in impedance when we change speakers, so it doesn't seem so simple.

The increase in sensitivity comes from an increase in current which now assumes 2 watts produced from the same voltage.
Efficiency has not increased. The 1w/1m number remains unchanged.

Tube amps that have more than one pair of output taps (2/4/8/16) are able to provide about the same power when matched to the speaker load.
Music Reference RM-200 test "the amplifier clips at its specified power of 100Wpc when the load impedance is equal to the nominal tap value; the lowest distortion, but also reduced maximum power, occur when the load impedance is much higher than the tap value,"
Distortion goes up and power goes down when the load impedance is lower than the tap value.
I believe damping factor also goes down, whereas light loading (like an 8 ohm speaker on a 4 ohm tap) increases it.

I believe the Inspire amps (like most tube amps with only one pair of outputs) will lose some power as you go above and below 8 ohms.

I can attest to two things: Omega speakers are very SET-friendly, and they sound wonderful with my 421a amp and both my Inspire amps. In contrast to most of the current Tekton speakers, Omega's use purpose-built drivers intended from the outset to be driven by low power amplifiers, most frequently paired with Decware Zen Triode amps (2 wpc) by dealers and long term owners. The current Tektons use prosound drivers that, while sensitive, seem to need a little more juice to get up and go. That is not uncommon: some JBL's and most Tannoy's share this characteristic as well.

If I were in Musica Amamtem's shoes, I would perhaps follow this approach:

1. Keep the triode-wired Inspire amp and Inspire preamp. It is easy to obsess over the SET 45 amp, but I don't think that is where most performance gains are to be had right now.

2. Pick up a pair of Omega Super 3i monitors. They really get you to about 85% of what Omega can get you. The Super Alnico's are nice (I own both) but the Super 3's are quicker and a bit better on the top end. They are also far less expensive and work very well in a small room, particularly in the near field. No one will ever believe that this medium sized bookshelf speaker with a single small driver is making all that sound.

3. Pick up one (or two) Rhythmik servo subwoofers. You could choose the dual 8" which are quicker and allow crossing over as high as 200hz, or the F12G (GR Research paper driver), which is still a lightweight cone. The latter has the advantage of being able to be connected at line level and speaker level. Some people feel that subwoofers integrate better when driven off the speaker output of the main amp, especially tube amps, as is takes on a bit of the character of the main amp.

The Rhythmik subs are also available without enclosures if shipping costs are a concern. The recommended designs are straightforward sealed enclosures that could be easily built locally.

A pair of Omega Super 3i's and a single Rhythmik subwoofer will cost less than the Inspire SET amp and will likely bring much more musical enjoyment. I have no doubt the 45 amp is a step up in the right circumstances, but my feeling is right now you would not receive benefit with your existing speakers.

This is true when speaker impedance is the only variable. In the case of the High Output Omega speakers, the number of speaker drivers in close proximity are doubled. The elec sensitivity of the speakers increases by 6dB with a 3dB in speaker efficiency. There may be question of the flatness of frequency response with two drivers, but that is another question.

Correct, in theory; I forgot the 3 dBs in the passband of the second driver (thanks), but the other 3 dBs (from top to bottom) is actually somewhere between 1-3 dBs with most solid state amplifiers. IME with tube amps there is no difference in the overall output of the speaker system, not like say going from 90 dB 8 ohm speakers to 93 dB 8 ohm speakers.

Edited for clarification.

:thumbsup:

This is also a PITA because I cannot sell my legacy systems overseas for the same reason.

All valid points and again, I'm not trying to replace my beloved Triode-strapped Inspire KT88 amp or wonderful LP-27a preamp.

Until now I naively thought the sensitivity figures correlated with low power amp capabilities ... Tuns out a 95 dB at 8 Ohms (Omega) is SET friendly and Tekton at 98 dB's is not. Go figure!

I turned down the Omegas Super 3i's or actually the floorstanding Super XRLS 3i and went for the Tekton's because of an expected lack of body to the sound with such a small diameter driver. Fast but lean, was my reasoning. Of couse at the time I did not know the Lore 2.0 would turn out power hungry in spite of their nominal sensitiviity rating. This is no problem at all with my current gear, plenty of power except maybe with 6V6's, but uncapable to adapt to a true SET.

BTW, Tekton's use the Eminence drivers. Any thoughts on the Zu Souls?

Thanks for the pointers!

DHT done right is excellent. But the output tubes are much more $ than pentodes. I'm no longer interested. YMMV

I really don't think you realize how good the Inspire gear you have it yet. No condescension intended.

BTW, Tekton's use the Eminence drivers. Any thoughts on the Zu Souls?

Sometime published specs are a numbers game. My Klipsch H 3's are 99 db on paper. 58hz is the bottom and I don't feel like I need to bother integrating a subwoofer. I have not seen measurements from and independent source. One review says they really lit up with 30 watts. For the past few days I have been using Pope 6V6GT's, CV181 copper base and an 80 rectifier with excellent results. Not at all anemic. Volume never above 10 o'clock. Same amp and pre as yours. I know there are better speakers but I can happily live with what I have.

I've not heard souls so no comment. You may just need to experiment more with tubes and caps. I'd work with what you have a little longer. :thumbsup:

I find the Omega's interesting but have not heard them.

I am interested in Zu as well. I have Omega Super 7 mkII monitors, which i really like, in my office. I am dreaming toward another system at the house with some floor standers. I was more thinking toward the Omens. I am a sucker for a good deal and like the comment above about the Omega 3i giving 85% of the Omega experience I have a sense the Omens may give something similar toward the Zu. I would love to hear any thoughts on the Zus in general.

I bought a pair of those on the auction site for $150 from a private seller. They are excellent. The seller bought 4 pairs from Grant for a Cary SLP05. I'm sure he tired of them B4 they settled in. They still needed more hours when I got them.

There are other sellers of the grade A tubes. Ice Lake Audio and h salience are two that I've bought from.

I found a good deal on a pair of 1981 Heresy's a couple of years back. Didn't expect to like them because (in my limited experience) I hadn't heard a pair of Klipsch that I had liked before. I was pleasantly surprised using my 2 watt set EL84 and while obviously they don't go real deep, I didn't use a sub with them in a 14' x 11' room.

Way too often the published specs are a numbers game. :icon_thumbsdown:

The Super 7 MK II monitors have the larger, 7" drivers. These should have more body to the sound than the 4.5" drivers of the Super 3i's, and yet the "Ferrite" nature of the driver is more mundane, so I did not consider them at all at the time. I was again probably wrong.

My Tekton Lore 2.0's sound wonderful with the right setup. I know these would benefit from more power but in a small listening room and near-field settings, that is not possible. I have all the volume (SPL) I need with the 6L6 and KT88 output tubes.

Good points too! Agreed. I understand the alleged CV181 from Psvane are really 6SN7's in disguise, which makes them all the more safe for the Inspire

Have you considered the Tekton designs OB? He is offering them at a pretty great deal at the moment $1700 delivered.... Unfortunately my room constraints aren't conducive to these at the moment....