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Old 3rd June 2007, 06:39 AM   #941
Salas is online now Salas  Greece
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Is timbral discontinuity from amp to amp something that you factor in, Lynn?
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Old 3rd June 2007, 07:46 AM   #942
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Default Driver edge diffraction

Given that pro-sound drivers will be used:

Any thoughts on addressing diffraction from the drivers(s) gasket(s) -- While there are exceptions, most prosound woofers have a pretty chunky face gasket. Can enABL really address this? Flush-mounting still doesn't address what happens where the surround hits the gasket.

I was especially curious about this when coaxes were still in the picture. 'Still seems relevant with the WR playing waaay into the midrange.

If this has been discussed elsewhere, kindly redirect me to wherever!

Thanks!
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Old 3rd June 2007, 08:20 AM   #943
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Quote:
Originally posted by salas
Is timbral discontinuity from amp to amp something that you factor in, Lynn?
Not in the usual audiophile mix-n-match way - "this sounds good, let's try it with this" - but from a more analytical perspective.

Any amp that's worth considering is going to be quite flat from at least 15 Hz to 30 kHz, at a minimum. So the coloration we hear is a function of amplifier distortion, nothing else. These distortions can have quite subtle causes and may measure at extremely low levels, or even evade current measurement techniques. That doesn't mean they're not there, though.

On a subjective basis, amplifier colorations affect different parts of the spectrum. This is to be expected - HF distortions are correlated to nonlinear current delivery into capacitive loads (which may themselves be nonlinear), Class AB switching transitions, and current-gain variations as complementary and paralleled devices switch on and off.

LF colorations correlate with power-supply artifacts and storage mechanisms, especially time constants that are similar to the beat-rate of music - LF feedback instability can enter here as well. In solid-state, gradual shifts in operating temperatures at the silicon die (within the package) will also shift beta (gain) and HF rolloff characteristics - these are called memory effects.

Rather than have all the amplifiers be the same, it makes sense to use them in the frequency ranges where they have ample headroom and low distortion. Tube amps of any type are hard-pressed to deliver 350 watts to a subwoofer at 20 Hz. Similarly, a 200-watt Class AB transistor amplifier isn't the ideal choice for a compression driver.

My criteria is "intrinsic linearity". With no feedback and no "helper" circuits, how linear is the circuit, at what power level, in which frequency range? Is the distortion low or high-order? If the intrinsic distortion is 10%, it doesn't matter if the amplifier is a SET amp being operated at much too low of a frequency or Class AB solid-state amp at 1 milliwatt and no feedback to conceal the AB transition.

It's easy to scale the power requirements of a widerange dipole. The tweeter doesn't care about 1/f transitions, and needs only a few watts - of the highest quality possible, since IM artifacts fall into the most audible frequency range.

From 1 kHz on down, we're starting to need more power - the center of the power spectrum is between 200 and 500 Hz, sometimes called the "melody region". Choice of power amp in this region is going to be highly subjective. Some people like the Class AB high-feedback MOSFET or bipolar-transistor sound. Some people are into Class D. Others like traditional PP pentode amps.

The subwoofers need to be designed as an integrated system, with dedicated amplifiers that have superb DC and LF performance. The Rythmik is probably the head of the class here, with integral servo feedback to compensate for dynamic driver nonlinearities.

I see no problem with 350 watts of Class AB power for the subs, 30~60 watts of PP KT88 power for the midbass, and 300B DHT power for the mids and HF ranges. As a matter of fact, that describes the power lineup of some of the best systems I've heard around here.

But there are some hard-core SPL lovers who use 300-watt prosound amps with Klipschorns or Altec Voice of the Theaters - many of the denizens of Audio Asylum are big fans of this approach. If 130 dB is really important to you, of course, you're not going to waste your time with dipoles, but go straight for an all-horn system with serious PA credentials.

There's also a middle ground of audiophiles who like high-end transistor amps. Amps like this don't do anything for me, with one or two exceptions - the LNPA150 and Gary Pimm's low-power MOSFET amplifiers. I can't think of any others. Plenty of folks like exotic transistor amps, and if that's your taste, go for it!

But keep in mind this speaker is going to be pretty efficient - 97 dB/metre/watt at the minimum, and more likely 100 dB/metre/watt. That's 20X as efficient as most audiophile speakers. So whichever amplifier you choose, it should sound good at milliwatt and microwatt levels.
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Old 3rd June 2007, 09:26 AM   #944
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Lynn ... Sorry you are laid up. Recover quickly.

Bad news for you, but is great that you have taken time to get into my favorite "Pro speaker OB's". I am a P.Audio coax fan. Will take weeks to read it all. More than greatly appreciated.
Low Q drivers are a hard one to sell to my buddies as they are stuck in Qts = 1.0 land. I love the soggy sound on some.
Would you be kind enough to give the good and bad points of adding inline resistors to gain Q when it is necessary to bring the F3 lower?
If already mentioned will you link to post?

Thanks, Zene (Vancouver, WA ... and I do make trips to Jamac/Audionics).
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Old 3rd June 2007, 03:29 PM   #945
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Hello,


Quote:
P.S. I received an e-mail from Lowther America recently, and they mentioned that there's a version of the Lowther with no whizzer cone - an obvious candidate for a ribbon tweeter to take over at 8 kHz. For those allergic to horns, the Lowther+ribbon would certainly be an alternative in the 1 kHz-on-up range. Now THAT would be an offbeat speaker - a trio or quartet of ToneTubby guitar speakers for the bass, MB, and low-midrange, and a whizzerless Lowther above that.

I wonder if the lowther could go lower than 1Khz, say 500-300Hz or something, without having significant distorsions. I ask this because I have no experience but I've noticed for example Mr.'s Martin King OB project using a lowther that down. Probably I'm alergic to crossovers in the 300Hz-5000Hz region or something... this would explain why I prefer a "fullrange" version.

The problem is that I think the lowther has a small Xmax for going that low. Mr.'s King simulations though reveal a small displacement for the lowther around 100Hz (well under 1mm, but of course with a cross point of 100Hz, 4th order HP filter).

I guess that a better option would be the Supravox 285-2000 exc. widerange. This 12", 102dB (!), whizzerless driver with plenty Xmax, would blend well with alnico TT, low-midrange driver. Over 5-8Khz a ribbon tweeter could jump in, or a good alnico supertweeter.

Lowther Open Baffle

Supravox 285
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Old 3rd June 2007, 11:24 PM   #946
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Quote:
Originally posted by Zene Gillette
Lynn ... Sorry you are laid up. Recover quickly.

Bad news for you, but is great that you have taken time to get into my favorite "Pro speaker OB's". I am a P.Audio coax fan. Will take weeks to read it all. More than greatly appreciated.
Low Q drivers are a hard one to sell to my buddies as they are stuck in Qts = 1.0 land. I love the soggy sound on some.
Would you be kind enough to give the good and bad points of adding inline resistors to gain Q when it is necessary to bring the F3 lower?
If already mentioned will you link to post?

Thanks, Zene (Vancouver, WA ... and I do make trips to Jamac/Audionics).

Which PAudio's have you used? Impressions? I thought many models seemed quite nice for the price. In fact I'm using the WN8S as a mid in a PA dipole here: OB simulation
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Old 4th June 2007, 01:50 AM   #947
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Sorry about the delay, the motherboard (and/or power supply) on my Mac Dual 2.7GHz G5 failed last night. This was the one and only overclocked model Apple ever made, complete with liquid cooling. I was wondering when it was going to fail, considering the peak temperatures on the processors were 70~73 deg C, and the idle temps were above 40 deg C.

After seeing those temps, I bought 3 years of AppleCare, and the tech comes to the house and does an on-the-spot repair, free of charge. He's going to earn his fee from Apple when he has to disassemble the complex liquid-cooling system to get at the motherboard. Fortunately, it didn't spring a leak - the coolant is a bright-green goo, a startling (and ominous) sight to see leaking out of any computer. I'll be using my TiBook laptop for the next few days.

-------

Wish the impulse response and CSD of the Supravox was better - those aren't very good measurements. FR is nice and flat, though, and people really seem to like the sound of the field-coil Supravox and Fertin fullrange speakers. The few times I've heard them at the ETF and RMAF, they didn't leave much of an impression - I really need to audition them more seriously this year at the RMAF show.

Lowther, everyone's favorite love-em-or-hate-em speaker (like Decca cartridges) I do know, being friends with Tony Glynn back when I lived in Oregon in the Nineties. Lowthers keep amazing me - they measure so bad, yet they can sound so right, especially in a Big Fun rear-horn or Oris or Azurahorn front horn. Not what I'd call neutral or low-coloration, but really entertaining sound, with big thrills when the planets are all in alignment. It's the last part ...

As for excursion, they're kind of like paper-cone compression drivers, with huge magnets, and very light diaphragms. Horn-loading all the way, baby! So I'm kind of conflicted about the best way to use them - a 300 Hz crossover is obviously going to stop any kind of visible movement and keep the VC in the gap, so from an engineering viewpoint, it's the obvious thing to do.

But ... I've heard the same (both 6 and 8-inch versions) drivers in standard enclosures and horns, and the horn versions are just so much more dynamic, despite sometimes annoying colorations. The biggest difference was with the 6-inch Alnico driver, which sounds petite, very clear, and miniaturized on a standard enclosure. On a Azurahorn AH-204, they sound BIG and very impressive, nothing miniature about the sound at all, with Altec VOTT dynamics. The presentation is completely different, and I would say heavily favors horn loading.

This gets us back to headroom. Many many posts ago, I startled readers with a design target of 120 dB SPL. That doesn't mean I'm going to use a 100~200 watt amplifier; no, that's not happening except for the subwoofer. When I mentioned that figure (which is still a design target), that was headroom for the speaker, not what I was planning for the system as a whole.

My Karna amplifiers are good for 16 watts Class A1 at 0.1% distortion, and 32 watts Class A2 at 3% distortion - with very little high-order distortion components. But the 18Sound or ToneTubby 12-inch widerange drivers, along with the Radian compression driver, can handle far more. That's headroom. Even if you don't use it, it's there. You can hear that it's there - it's obvious, the speaker never sounds stressed or like it's even trying very hard. The immense peaks that come through make that obvious, like a big torquey V8 when you get on the freeway. Tap the accelerator, and you GO! The same for a speaker with 10 to 15 dB of reserve headroom - there's a sense of power in reserve.

I like headroom in electronics, too. John Atwood's Artemis phono preamp can put out 60 volts RMS at the output jacks. Think about that for a while. The driver stage of the Karna is a PP 45 DHT running in Class A with transformer coupling - it can cheerfully drive the grids of the 300B's 30 volts positive with no transition visible on the scope. That's headroom.

Moving on the diffraction/driver mounting question, and the choice of crossover. Well, I listened to the Summa's at the RMAF, and although I couldn't draw any conclusions about tonality thanks to the bottom-dollar Pioneer HT receiver and DVD player, it was obvious that system integration was outstanding, and smoothness and coherence of the off-axis measurements were borne out in listening. Earl Geddes chose to cross his 15" driver and 15" mouth horn around 1 kHz (one wavelength at 1 kHz) - and it sounded very well integrated to me.

So I don't think 1~1.2 kHz is a high crossover at all. I was very happy with the sound and tonality of the Bastani Apollo, and the Apollo 12" woofer free-runs with no crossover all the way up to 6 kHz - and I thought it sounded great, much better than the small-driver audiophile speakers in the other rooms.

As for mounting, my preference, as always, is for flush mounting of the front surface of the driver frame on the front baffle, so yes, you do have to make a precision-fit rebate cut with a router. It works very well for the Ariel with its 3.8 kHz crossover, and it should work even better at one-third the frequency.
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Old 4th June 2007, 03:55 AM   #948
Salas is online now Salas  Greece
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Quote:
Originally posted by Lynn Olson


Not in the usual audiophile mix-n-match way - "this sounds good, let's try it with this" - but from a more analytical perspective.


From 1 kHz on down, we're starting to need more power - the center of the power spectrum is between 200 and 500 Hz, sometimes called the "melody region". Choice of power amp in this region is going to be highly subjective. Some people like the Class AB high-feedback MOSFET or bipolar-transistor sound. Some people are into Class D. Others like traditional PP pentode amps.

You did factor in amp variations validly. Wanted to know your approach. Thanks Lynn.


In the School Of Sound Recording when I was 20 they told us that the 200-800Hz band is called the 'power range' and carries the body of music. Must be similar to the term 'melody region' it seems, only a bit wider.
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Old 4th June 2007, 04:01 AM   #949
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Lynn,

Wait about three weeks and then get back to Lowther America on drivers. They will have the first EnABL'ed EX series drivers by then. I processed a DX pair and sent them off to Limono just last week. Easily the most vivid drivers I have ever experienced. Absolutely not a sound dropped, period.

Can't speak to dynamic range but the treated DX drivers had completely quit shouting when driven hard. Just got louder and seemed quite comfortable about it. I was not so comfortable, I was measuring 107 dB peaks and 100 dB avg SPL on my trusty RS junk. Resolution was just like you get from expensive, narrow band tractix horns and excellent compression drivers, but with tremendous depth.

I am quite serious when I say I have never had this much information in my listening room, especially with this kind of dynamics and persuasive color.

We will have to see what Jon thinks and whether or not he will loan them back out, once he gets his hands on these brand new EX models.

Bud
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Old 4th June 2007, 07:28 AM   #950
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Auqerpro ...
Have limited listening with P.Audio BM12CX38 12" coax on temporary OB's. Thought it had promise. Only heard with 2 T-amps and was way underpowered.
Getting new/better panel ready for it now. That's why I'm here to get ideas. Hafler 120 amp for the cone and a Super T (coming soon for the tweeter) with Ashly active crossover to play with frequencies.
One or two per side (yet to get) P.Audio E15-200S woofers for OB bass with the coax 12's.

Also have P150/2226 (JBL clone) to use in all horn bass bin and a pair of E12-200S woofers I have no idea what I got them for.

Both systems ready by 2016 at my present rate.

Zene
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