Lynn Olson's new speaker project.

[Rajiv]

Hi,

From the long,interesting and informative thread on DiyAudio.

Beyond the Ariel - Page 768 - diyAudio

Looks like Lynn is falling back on a classic design. I run a similar system(15 inch woofer and large format compression driver) and am very interested in knowing how he integrates the super tweeter.I have tried several tweeters and configurations but have not found the right balance.

Nothing all that radical. 15" high efficiency bass driver in a resistive-vent cabinet with attention paid to diffraction reduction, the AH425 Azurahorn with a large-format compression driver, and a high-quality supertweeter.

Preliminary measurements are comparable to the Ariel in the time and frequency domains, with a 7~8 dB gain in efficiency and a headroom increase of 10~15 dB. Sounding good at this point, but much development remains. I hope to make the RMAF deadline, but can't say for sure at this point.

In a way, it is a modern development of the Jim Lansing Iconic that debuted in 1936. Very few music sources back then had content above 8 kHz; at high frequencies, shellac 78's were mostly noise, and the Bell Telephone intercity relays for the AM radio networks were sharp-cut at 8 kHz. A few people could pick up Major Armstrong's Yankee FM Network on the East Coast, but that was about it for wideband (and low distortion) audio. No-one outside of Germany had heard of magnetic tape, and AC biasing had not been invented yet. But the basic format of the Iconic lives on as large-format studio monitors.

Modern LP's, if played with a moving-coil cartridge, have content above 30 kHz, and high-resolution digital extends to 40 kHz and above. So the system uses a supertweeter to extend the bandwidth above the usual horn frequency range.

No, the styling does not echo the Iconic, and the drivers do not use field coils to energize the magnets.

Don't worry, the Ariels will be kept around, doing rear-channel duty if nothing else. The Ariels don't sound boxy at all; they were originally designed to mimic the sound of stacked Quad ESL57's, and they sound very much like electrostats - quick and light on their feet, due to the time response and low diffraction signature (no sharp box edges).

The new speakers sound like really big electrostats, with more dynamic and tonally vivid bass than panel speakers. The "horn" aspect of the presentation is the spatial presentation; the solo performers are in-the-room, not behind the plane of the speakers, as they would be with most electrostats. Pianos sound like they are in the room, not somewhere else, for example. This is most likely is a function of the large radiating area of the bass and horn drivers, along with low IM distortion.

There's also a 70mm Stereophonic Sound widescreen movie aspect to the presentation - it's a big sound, not surprising considering the enormous headroom of the large-format compression driver and the 15" bass driver. Many of you never heard what widescreen movie theaters sounded like in the 1950's and 1960's - completely different than modern THX screech and boom - but the new speakers bring back memories of seeing Ben-Hur, Spartacus, West Side Story, My Fair Lady, and Lawrence of Arabia. I lived in Kobe, Japan, and later Hong Kong, and our family saw these movies in their full 70mm widescreen splendor (and six-channel all-analog mag-track sound) at the Asian premieres.

You can keep your digital-cinema and THX sound; no comparison at all to 70mm Technicolor on a curved screen with three theater speakers (powered by all-analog vacuum-tube electronics) behind the screen. Stereophonic sound was still fairly new in those days, and hearing what sounded like a full symphony orchestra right behind the screen made the audiences gasp in surprise. Nowadays, it's all about very loud SFX explosions and extended battlescenes with obvious-looking CG rendering, not the same thing.

Regards
Rajiv

 

[viren bakhshi]

Hello Rajiv,

So, simplicity wins out in the end, even for Lynn Olson!

His long standing thread was coming out with pretty complex designs earlier. A classic two-way horn - worth emulating!

Viren

 

[Rajiv]

Hi,

Good information for folks trying to add a super tweeter.

Well, if the supertweeter is off to one side, then imaging will be somewhat unstable, since the listener will hear a crossover with different phasing for each ear. Even a slight movement of a few inches to the left or right will shift the relative phasing between horn and supertweeter.

In principle, a supertweeter located directly above the horn will have the same phasing issues, since any supertweeter (that isn't coaxial) will be several wavelengths apart at the crossover frequency. If the supertweeter is directly above the horn, though, at least there won't be left/right differences between the ears. What happens instead is a vertical null that comes and goes with shifts in seating height. If the null is at 7 kHz or above, it creates a false impression of additional image height, but not a coloration that is tonal in character. If the null is 5 kHz or lower, tonal colorations are heard, and if the null is 3 kHz or lower, then more severe colorations will arise.

A supertweeter seems to benefit from a 3rd or 4th-order highpass crossover, despite conventional wisdom. The lower the supertweeter reaches into the region where pitch is audible the more noticeable it seems to be - and a supertweeter should never be be directly audible as a driver. All switching it on and off should do is add a touch of sparkle and air at the top - there should never be any tonal shift to the loudspeaker as whole - if there is, the supertweeter is too loud, too peaky, or has too much energy below 7 kHz. It has to remembered that very little spectral energy is above 7~10 kHz, and a moderate-slope crossover has to work against the steep spectral tilt of the original program material.

A simple way to test this is listen to the supertweeter alone - if you can hear what sounds like music coming through, the crossover isn't steep enough, or is too low, or both. All you should hear is an occasional transient - basically, clicks, and not much else. It should like it is doing almost nothing when you listen to it by itself.

Regarding the comment that a 500hz XO CTC is small enough to be "point source", I'm not sure I agree. This has to be determined by subjective experience - preferably with broadband program material like massed chorus, or large-scale symphonic music. Some driver layouts will disappear into a single virtual point source, and others won't, and it doesn't always agree with theory.

I've had bad experiences with large MTM's - it was a struggle to get the 5.5" drivers of the Ariel to sound like a single coherent driver. I've yet to hear a large WMTMW or large WTW sound coherent, regardless of crossover, and I've heard lots of them at hifi shows and at friend's homes. Small phasing differences - on the order of 10~20 degrees between drivers - that are acceptable in a compact MTM sound quite unpleasant in a larger system, and the higher the top woofer is off the ground, the worse it seems to be. It could be that bass coming from above ear height just sounds weird and unnatural to me - it's something I try to avoid in my own designs.

However, personal tolerance for this seems to differ. Plenty of other audiophiles enjoy large WMTMW and large WTW systems, so it could just be me.

Regards
Rajiv

 

[santhosh]

Hi,

Good information for folks trying to add a super tweeter.

Regards
Rajiv

Thanks for sharing this info. I have to tread this path sometime soon (as soon as I find a pair of Altec 288s). Hope to find a Mantaray 902-16HF Supertweeter like this one:
Altec A6/MRII594 any good for hifi?

Also, what other drivers match the timbre of Altecs?

 

[Rajiv]

Hi,

An update.The details of Lynn's peaker.

The basic design is similar to the Lansing Iconic from the 1940's,the difference being the use of the 1.4 inch large format driver instead of the smaller 1 inch driver.

Lynn's design is similar to the Shindo Latour in the use of a large format driver.The Shindo being a copy/very similar to the Westrex 2080 from the 1950's.

Beyond the Ariel - Page 780 - diyAudio

The new loudspeaker is around 99~100 dB/metre/2.83Vrms, with a load between 12~20 ohms over the working range.

The bass driver is an Altec/GPA 416B (Alnico magnet, 16 ohm version), the HF horn is an Azurahorn AH425, the large-format compression driver is either a Radian 745Neo (Neodymium magnet, 16 ohms) or Altec/GPA 288 (Alnico magnet, 16 ohms), and the passive crossovers are 3rd-order lowpass at 700 Hz (transitional between Butterworth and Bessel) for the 15-bass driver, and a 4th-order highpass at 700 Hz (transitional between Bessel and LR4) for the HF driver.

If the Radian 745Neo is used, it needs to be attenuated by 14 dB, which is accomplished with a custom autoformer with a 16-ohm shunt resistor between the autoformer and the lowpass filter. The highpass filter is designed for a 16-ohm resistive load.

The woofer uses a standard Zobel inductance compensator between the lowpass filter and the woofer, and the lowpass network is designed for 12-ohm resistive load.

No inband equalization is required for either the woofer or HF horn system. The system is time-aligned with all drivers in-phase; the lip (outer edge) of the AH425, by lucky coincidence, is about 1/2" forward of the front face of the bass cabinet, with about 2" of vertical spacing between the top of the cabinet and lower edge of the AH425. The bass cabinet is about 4.5 cubic feet and uses a resistive vent.

I hate to disagree with Bill, but the Alnico 416B (Classic Series) sounds just amazing - going out on a limb here, but it's the best bass driver I've ever heard. The first thing you notice are the vivid tone colors of the instruments, and the in-the-room naturalness of the singers. I really wouldn't want to give that up to save $100 on the driver. Relative to the other costs of the speaker, including deluxe crossover parts, the AH425, and the compression driver, that's not really a major saving.

(Comment on magnet sound: if you can hear the difference between nickel-core, M6-core, and amorphous-core transformers, you most certainly will hear the difference between driver magnets. It's a very similar kind of sound. Alnico, to me, sounds a lot like nickel-core transformers, with lots of sparkle and immediacy to the sound.)

I've not heard a Model 19, but the hallmarks of this speaker are the delicacy and immediacy of the Alnico-magnet bass, the midrange effortlessness of the large-format compression driver, and the silky-smooth and unhornlike sound of the LeCleach' T=0.707 horn.

This may sound weird, but in terms of the presentation, the new speaker is kind of halfway between a wall-sized electrostat and a Klipschorn. Spatial impression is very deep, with performers in-the-room, but the performing acoustic going back about 30 feet or so. But the dominant impression is the vividness of tone colors, subtle dynamic shadings, and what seems like unlimited headroom (in reality, about 10 dB better than commercial audiophile speakers).

One thing I've learned from this project is that horns are far more sensitive to crossover adjustments than direct-radiator drivers. The low-slope (1st and 2nd-order) crossovers had more IM distortion than I could accept, even with the large-format compression driver. Twiddling with the corner shape was also quite audible as well - the more conventional Butterworth alignments had noticeable energy pile-ups near the crossover frequency, which impaired driver integration and led to a sense of spectral tilting. I gradually went to softer and softer corner-frequency shapes until the impression of energy pile-ups went away - basically, fiddling with the group delay until it fell below a perceptual threshold. Filters that are transitional between Bessel and Linkwitz-Riley 4th-order seem to work fine.

As to the difference in sound between alnico and ferrite magnets I agree with Lynn.

This thread is very informative on all aspects of audio.Very interesting take on designing a hybrid tube/SS amp.

Along those lines, there's nothing to stop anyone - particularly in this intrepid forum - from combining the Susan final stage with the first stage of the Amity amplifier. In other words, 1:1 Input Transformer -> PP 5687, 7119, ECC99 -> 1:1 IT Transformer -> PP MOSFET followers -> Output Transformer.

The gain structure would avoid any need for step-up transformers - the input and IT could both be 1:1 - and distortion from the PP 5687, 7119, ECC99 drivers would be very low. The driver tubes would use a modest 120V to 150V B+ voltage, avoiding the more troublesome B+ supplies in the 450 to 550V range. And isolated supplies for the driver and output sections absolutely sounds better than shared supplies.

A more exotic version would use a 1:2 Input Transformer -> PP 45, 2A3 -> 1:2 IT Transformer -> PP MOSFET followers -> Output Transformer. This driver would have (much) lower distortion and more dynamic drive characteristics. The B+ would be raised to the 200~250V range for the best possible dynamic range and slew rate from the balanced pair of direct-heated triodes.

If the builder wants to go all the way with this design, I would recommend shunt regulation for the driver stage - fortunately, since the final stage is an ultrahigh-gain MOSFET follower, there's less need for regulation in the power stage (since the followers have inherently high power-supply rejection as well as inherent balance from using matched pairs). Gary Pimm's shunt regulators have extremely high PSRR, well under 1pF capacitance, as well as excellent reliability (they can withstand 1KV transients).

That's a complete hybrid amplifier; anyone interested?

Regards
Rajiv

 

[Rajiv]

Hi,

Another interesting post. Sounds like an interesting digital set up.

What do Altecs sound like? Well, they're the auditory equivalent of a brilliant Colorado day minutes before a sudden storm. Sparkling. Vivid. Dynamic.

Yes, I heard not one, but TWO great systems on my trip. David Robinson's, editor of Positive Feedback Online, who had the all-up MBL system (preamp, amp, and speakers) with an astonishing front end: a USB DSD DAC that played both 1X DSD and even more remarkable, 2X DSD, all from a laptop with the most astonishing copies of mastertapes I've ever heard. All of your favorites, going back to the Seventies and Sixties, but in fidelity that was indistinguishable from an Ampex ATR-100 playing the original mastertape - not a second-generation copy. Many recordings that I had thought had screwed-up mastertapes were crystal clear, and revealed a level of artistry from the performers that I didn't know they had. More to be shown by David at the Rocky Mountain Festival in a couple of weeks.

Gary Pimm had a DAW-based system with J River software playing the 44.1/16 and 88.2/24 files, routed through a software rack that had third-party VST plug-ins for crossover and equalization functions. An Echo Layla with modified analog electronics took care of the DAC conversion. As usual, the sound was great, but I told Gary, "Go Alnico, man, you won't go back, trust me on this". Since he's got a pair of Altec 604's and a pair of Electro-Voice 15's in his basement, he can just try a pair of each and see which he likes best. Or better yet, swap the 604's, which are very very difficult to design crossovers for, for a pair of 416's with Alnico magnets. He'd probably come out ahead in the trade, and the 416's are way better than anything from Eminence.

The low and infra-bass from Gary's system is the best I've ever heard, bar none. We were playing the soundtrack from the London Olympics opening ceremony, and the sound of that giant bell shook the whole house. Crystal clear stop-starts, not like subwoofer bass at all, and an unlimited sense of power. Pretty amazing.

Regards
Rajiv

 

[odyssey]

Rajiv
In your experience, at what frequencies is a supertweeter a must? I mean if your main driver does 10K, is that sufficient, how about 12K or 15k?

 

[corElement]

I'm glad I got to experience the joy of vintage cinema halls before they were eliminated by the new badly implemented digital multiplexes.

I agree, huge 70mm curved screens and theatre speakers were a lot more involving as compared to modern day screech and booms.

But at the same time, LED cinema hall screen and iMAX screens obliterate the old screens on video quality and contrast.

 

[Rajiv]

Rajiv
In your experience, at what frequencies is a supertweeter a must? I mean if your main driver does 10K, is that sufficient, how about 12K or 15k?

Hi,

Sridhar, to my ears if the driver starts to roll of from around 10khz it sounds a little muted and soft. High energy transients lose their impact. However if the driver/speaker is well balanced i.e. it does not go too low but is designed to compensate for the HF roll off the speaker can sound very good.

My experience with the Ampex 620 amplispeaker is the basis of my statement.The 620 uses a JBL 8 inch full range driver similar to the Altec /WE 755. The Ampex 620 does not go very low (70hz) and the roll off is from around 10K but it is such a coherent unit and musicaly satisfying that I did not miss the extention at the frequency extremes when I listened to it.
However it may not be everyones cup of tea.

If I were to add a tweeter to the 620 then I will have to also extend the LF to compensate for the extended HF.Otherwise the sound loses balance and sounds bright. Yes,I have tried and found that it is best to leave it as the designer intended. I think the same will apply to other drivers/speakers also.

620 ampex HiFi-Do McIntosh/JBL/audio-technica/Jeff Rowland/Accuphase


The Altecs and Tannoy Golds go up to 15K and to me they sound good .There is not much musical information at these frequiencies but harmonics that give that bit of "air" to the reproduction.I have been playing around with different tweeters/supertweeters to get that 'air' in my system but finding the right combination to match the Altec/Tannoy drivers is proving elusive.

I can get the Tannoy supertweeters or the expensive Fostex and the other recomended tweeters but they are overpriced in my opinion and for me the fun is the experimenting.

Regards
Rajiv