#2481
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Again, thanks. I probably need much higher sensitivity than that for a true DHT SET like the 45 SET from Dennis, so these need to be horn-based. My Tektons are 98 dB's theoretically and probably net out at around 94-95 in reality, so good for my current needs.
Last edited by Musica Amantem; 09-19-2016 at 03:37 PM. |
#2482
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I'm pretty sure the original Dynaco A25 measured at around 84-85dB. I owned a pair for 5 years, they were not very efficient.
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#2483
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I can't agree with you on that one. I used a 6wpc Tripath amp on a pair and they were definitely higher than 85dB. They have a 10" alnico paper woofer running no crossover with a low end that stops around 45hz or so. The modern replacement for this driver is 89dB, with what appears to be 10 ohm impedance and a low of 8 ohms. The A25XL used a more efficient woofer and got 92-93dB.
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#2484
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I just found the ancient Stereophile review of the Dynaco A25. For years I've been seeing people refer to them as having a 90dB sensitivity. Now I know why. In their measurements they state that they achieved a SPL of 90dB at 6'. So there's that 90dB figure. And this measurement would suggest that their true efficiency would be 93dB at 1M.
However, a careful reading of the article shows that the 90dB figure was when they were driving the speaker with 10 watts, not 1. So if we take that estimate of 93dB @ 1M with 10 Watts, that would be 83dB @ 1M with 1 watt. Check Page 7 of this publication: http://www.updatemydynaco.com/docume...acoReviews.pdf Elsewhere in that publication they refer to the A25 as being only a little more efficient than an AR 3A. I also found two references as to when the old High Fidelty magazine reviewed them and measured the A25 at 82dB. Last edited by Bombadil; 09-19-2016 at 04:00 PM. |
#2485
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The other issue is, going horn-loaded is opening another can of worms, with all sorts of issues, mainly the physical volume required for these devices to work well at low frequencies (and the expense). A more practical approach seems to be combining horns for the highs and mids and use a fast dynamic driver for the bass. The tricky part of true DHT SET enjoyment is not the availability of amp design talent but what speakers would really do justice to them and still be affordable. I believe it is a much tougher objective for an audio engineer or genius artisan to develop a practical and affordable, well-sounding, horn-based speaker than a true DHT SET.
No wonder the bug stops at 5 Watts SET Pentodes/Beam-Tetrodes strapped as Triodes, as you can still apply conventional, mass-produced, high sensitivity speaker technology to them and get away with it. Last edited by Musica Amantem; 09-19-2016 at 04:56 PM. |
#2486
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What do you want a speaker to do? This may sound odd but have you considered a headphone amp for large Scale music? As a kid I attended the Chicago Symphony. It was amazing. I have never been able to create that at home. Last edited by FloridaBoy; 09-19-2016 at 07:03 PM. |
#2487
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It has been a while and I do not recall your setup. What are your room dimensions, listening volume, primary genre,...? I was seriously contemplating a pair of Zus to mate up with the PSE I have on order from Dennis, though this bit of dialog here of late has me discouraged. I may have some Omega Omnis in my future instead. |
#2488
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#2489
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I think a difficulty many of us face is trying to get high efficiency speakers to do too much. Unless we commit to some some fairly physically imposing speakers, we usually end up in some sort of compromise. High efficiency usually comes at the expense of deep bass; the horn size to produce a true bass wave is enormous, and it is difficult to get a high efficiency direct radiator to move that kind of air.
It is also difficult to make an uncompromised full range speaker. They usually have a rising response in the midband that is hard to match at the top end. Omega speakers are no different in that regard, just better at it than most (I'm looking at you, Fostex). The best way to think about a full range driver is that it is in reality a wide range driver, with compromises on the bottom and top ends of the frequency spectrum. However, this crossoverless, wide range driver can sound really, really good and is a pretty easy load for the amplifier. Peter has addressed some of these shortcomings by going active: he runs servo-driven midbass subs, actual subs, and upward-facing tweeters on the top. He uses a line-level crossover, cutting the main drivers (Omega Super Alnico Monitors) in above the midbass, probably relieving them of half the acoustic power, letting his 5-10 watt amp behave like a 10-20 watt amp. I'm quite sure he never wants for more power. I use a couple different pairs of Omega's as well, but am working on a "big rig" speaker. The main driver is an Altec 414C (97dB efficient, 8 ohms, runs without crossover from 40hz to 4,000hz). This driver cover the entire vocal range. Above 4,000Hz, I will use an Altec 802d (nominally 106dB, 8 ohms, but probably about 100dB in the range I will be using it) with a 1st order crossover bringing it in at 6-8,000Hz. The 802 is mounted on an Altec 32A horn - an odd bent horn derived from the WE 32A horn. This bent horn is suitable for use in smaller spaces like studios or listening rooms (in contrast to other Altec horns which were designed to be used in theaters). The enclosure is more or less an Altec 614 of 3.3 to 4 cu ft tuned to 40-50Hz. I don't anticipate using a subwoofer in my small room, but if I did I would go with Peter's choice of Rhythmik servo subwoofer(s). If that sounds like a lot of effort using expensive, hard to find (and sometimes no longer in production) parts, you could go with Peter's method of efficient single driver with active subwoofers, or you could find a nice pair of Klipsch speakers (Heresy, Cornwall, Forte, Chorus, or LaScala) and update them with nicer crossovers and diaphragms. If you choose Heresy's or LaScala's you'll probably still want bass reinforcement, but you'll never want for power. |
#2490
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Quote:
I used a 6A5 single ended amp before I the Inspire. The 6A5 is basically a 2A3 with a 6.3V heater which is center tapped for the cathode and has cathode sleeves to reduce hum. The 6A5 amp had very slightly tighter bass, but was noisier and became congested sounding at a lower volume. I don't listen to it much since I got the Inspire. Dennis' amp is better all-around and doesn't need unobtainium tubes. My Inspire is the 6L6 variety. I use it with Triangle Antal 30th Anniversary speakers which are about 91 dB efficient. They're three ways with a spun aluminum horn tweeter, paper cone midrange and two 8" plastic woofers. I preferred these to Harbeth Compact 7s and the smallest Devores. The tubeset I like best is GE 6V6G with a 7AF7 driver and Magnevox 5Y3 rectifier. This is only about 5 watts, but good enough for most music. When I need to play something really big, I put in a couple of recent Gold Lion KT88s. |
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