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Multi-Way Conventional loudspeakers with crossovers

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Old 10th June 2007, 08:07 AM   #1011
mige0 is offline mige0  Austria
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Hi



Lynn, it's a blessing and a burden to have such fine ears / perception !

For audio guys life is MUCH easier if you are not too much bothered by listening at signals that are processed by silicone or some less than perfect parts elsewhere on its way from recording to playback. Did you finally work out an acceptable solution for your line stage ? I found power supply concept ( stage by stage !!! ) and ground layout as some of the most crucial points especially with discrete circuits. I once changed a "unlistenable" (- well not quite - ) Naim pre to a really nicely flavoured gear with incredible deep image this way. Even with minimising stages, I ended up with >30 supply lines right to the power supply and even more ground lines to the star point within the pre.
I am very curious what's the outcome at the end of your pretty openly OB design process.
Congratulations to you and all, for a thread that exceeds 1000 very interesting posts.

As for the active versus passive crossover discussion, my findings are that passive crossovers - even build with high quality parts throughout - have kind of coloration that I for myself describe best as lack of some "directness".

MBK, thanks for throwing in your personal experience with line arrays in a domestic context ! I never had special interest or considered to try LAs until this thread and some of your postings.

As for the source size perception, I am not sure that I understand what you mean with "envelope of the low frequency". Is it rise time you are referring to?

My understanding about source size is somehow mixed with the perception of the room size, which means the less early reflections ( that you cant really avoid in listening rooms at home ) the bigger size you get – presumed the recordings you listen to provide reverberation accordingly.



Quote:
A horn and an optical lens are not the same...
We should not over stress analogy, but in terms of concentrating energy to a solid angle its basically has the same effect I think.


Greetings
Michael
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Old 10th June 2007, 09:18 AM   #1012
Salas is offline Salas  Greece
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Quote:
Originally posted by mige0


As for the source size perception, I am not sure that I understand what you mean with "envelope of the low frequency". Is it rise time you are referring to?


Attack,sustain,release, and the mid-high complications?
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Old 10th June 2007, 11:54 AM   #1013
Salas is offline Salas  Greece
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Lynn wrote:

''The perception of parts degradation in passive crossovers vs active crossovers is also individual. There's been a big fad in Europe over the last several years of using the Behringer DCX, either modified or stock, in high-end time-equalized horn systems. At the 2004 ETF, I heard some very high-quality horn systems, and when doing a direct comparison between passive and DCX crossovers, I felt the DCX ruined the sound, flattening out all the subtle details and giving an unpleasant metallic coloration to everything. With the passive crossover, at least things sounded more natural.''

In some older threads I have maintained that the DCX and DBX PA level is completely lo-fi and I have suggested the XTA brand which can be found for about $2000 second hand in perfect condition.

As for line circuits discussed by Lynn, my best design so far is a triode strapped RCA 6V6G smoked glass STbottle running at 22mA 350V B+ with a gain of 7.

At this level of sonic honesty, to use digital and op amps (especially cheap) higher than 200Hz commands oodles of make believe to sound right.
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Old 10th June 2007, 06:24 PM   #1014
mige0 is offline mige0  Austria
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Hi


Quote:
In some older threads I have maintained that the DCX and DBX PA level is completely lo-fi and I have suggested the XTA brand which can be found for about $2000 second hand in perfect condition.

salas, could you point me to that threads please or give a short summary ?
You really mean $ 2000.- for SECOND HAND ( DP 446 ? ) ??


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Old 10th June 2007, 07:36 PM   #1015
Salas is offline Salas  Greece
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There is one XTA DP 226 for $1400 on e-bay right now. See. DP 226 features.

Old thread about multiamping vs passive. Read.
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Old 10th June 2007, 09:47 PM   #1016
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What I find quite striking is just how different individual perceptions are. People who I admire and respect - my dear, departed old friend Bob Sickler of Audionics, Siegfried Linkwitz, who I've met and chatted with at some length, and Earl Geddes - are all pretty accepting of digital, opamps, and Class AB solid-state sound.

I was in that group too until about 1990, when I went the second meeting of Oregon Triode Society and heard a trivially modified Dyna Stereo 70 utterly crush a $3500 Audio Research Classic 60 amplifier. That was a shock - more of a shock when I found out the "modification" was nothing more than converting the ST70 from ultra-linear to triode, nothing more than moving two wires.

When I finished the Ariels a year or two later, I auditioned them on something like 30 different amplifiers. I was appalled at how different the amplifiers sounded, and worse, some of the newest, most expensive, and best-reviewed sounded the worst - and some of the rusty old classics sounded remarkably good. Two of the classics that stood out were the Citation II and the Scott LK-150 - the newer, audiophile versions quite commonly had weird colorations (which I now attribute to poor regulation schemes and low-grade circuit boards).

That was a quality of the Ariels that took some adjustment - they were much less tolerant of amplifier quality than 86~88 dB/metre speakers. Low-efficiency speakers just gobble up the watts and aren't too particular about the quality. Huge banks of paralleled Class AB MOSFET or bipolars transistors are just fine with these kinds of speakers - it seems to take 200 watts just to get them to wake up and play music.

The Ariel was quite different. The old standby Audionics CC-2, although a little grainy sounding, was overall pretty neutral and listenable. The simplicity of the output stage, along with the high slew rate and inherent stability, worked in its favor. Much to my surprise, the Crown Macro Reference sounded quite good as well, and had plenty of power too. For some reason, the Pass Aleph 3 didn't work at all, and I never figured out why.

On the tube side of things, most of the audiophile PP pentode amps had funny colorations, as if they were unsuccessfully trying to mimic the sound of old, worn-out vintage gear. I suspected these were deliberate colorations to mask the sound of screechy CD players and harsh-sounding solid-state preamps. Direct-heated triode SET's were all over the place too, although many of them were much, much more transparent than the murky-sounding PP pentode gear.

I found that aiming for the simple goals of low coloration and transparency put me in a fairly small group of audio designers - I guess most of the industry are trying to please the reviewers of the Big Two magazines, who like a hard-edged, unnatural sound. When the magazines say XYZ component is "accurate" the sound to me is mechanical, unnatural, and harsh, and nothing like live acoustical music at all. I think magazine reviewers stopped listening to live classical music at least 20~25 years ago, based on the kinds of equipment they favor in the reviews.

Now that I've met Mike Sanders of Quicksilver Audio, I'm pleased to discover he tunes his amplifiers for a natural sound as well - and he designs both triode and pentode amplifiers. There are a few of us who don't care for the mainstream sound, but aren't ready to start collecting Western Electric, Klangfilm, and Vitavox gear just yet - we're not quite that far out. (Although one of these days I'll indulge myself and get an EMT 930 - that is one nice-sounding turntable!)

Returning to the topic at hand, the new speaker is going to be another 6 dB jump in efficiency, compared to the Ariels. All the things the Ariels did that was different than conventional low-efficiency audiophile speakers, I'll be facing again. The new ones will be firmly on the doorstep of horn territory, and will undoubtedly be just as picky about amplification. This is a certainty - it's the one thing about the new system I know for sure.

P.S. Good quote here from Bill F: "my non-scientific rule of thumb with OBs run much below f-equal is to imagine the volume displacement of an equivalent sealed system and then quadruple it if you want to end up with dynamic headroom". By the way, the volume displacement of a single 21" driver is comparable to three 12" drivers, and it would fit on the baffles we've seen here.
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Old 10th June 2007, 10:14 PM   #1017
Salas is offline Salas  Greece
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Lynn, I dare to air my assumption that we audio people don't really perceive differently, but we perceive selectively. If I just set my mind to prove a speaker concept for instance there is a big danger I will seek fast solutions for drive and control. The primary urge, the focus, is proving a mental structure. Its about mental aesthetics. And if it principally works, wow! Thats the kick I really look for! Mind is a big big con, using us. Happens all the time. Aural sense is an 80% brain process psychoacoustics says. Hammer, anvil and stirrup move the same in my and next man's head, but the individual 'translator' con brain has ideas, education, memory and feeling of its own.
Each of us pursuing individual goals just zooms in a portion of the picture. But some still have the veteran character control not to forget that the goal must be the total picture (music) and not specific technical perfection. Its a twist. We don't seek music many times when making stuff. We seek technical achievement. We get to like the sound of 'technique'. Real danger is that we may get to feel that it is the real thing, and become addicted. We are perverts many times. Its part of the game, but at a point we can get over it. And we have a powerful tool for waking up. Boredom! Non natural may succeed feeling even great, but at a point we get sick. Its like eating in fast food chains only, for too long.
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Old 11th June 2007, 02:53 AM   #1018
MBK is offline MBK  Singapore
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Michael,

just to set the record straight - all my comments on line arrays come from studying the relevant papers and other people's axperiences, because at some point I wanted to build one. But I never did, sorry if it sounded like I had actual experience in line array building. I have plenty of hands-on experience in OB building, and I like to keep up to date with research if I can, that's all.

Apparent souce width (ASW): it's a complicated issue, and most research comes from either concert hall acoustics considerations or from people who'd like to simulate soundfields. All effects are frequency dependent and several effects mix together.

According to Lexicon's Griesinger, ASW is strongly influenced by rise time of a note: shorter rise times sound smaller, and we are talking of ranges starting at 10 ms. My inaccurate "envelope" comment should have referred to "rise time".

Then, in actual architecture, come reflections and reverberation, but they must fit in particular time windows to be useful. Too short, and it sounds closed-in (especially below 1.5 ms). 10-15 ms or more should be the goal. But reflections in the 50-150 ms range make intelligibility suffer, because this time window corresponds to the average gaps during speech.

According to soundfield simulation research, the inter-aural correlation coefficient is ultimately responsible for the size impression: decorrelated phase/time delays lead to a more spacious impression, easy to verify if you compare correlated and uncorrelated pink noise in stereo - the correlated one sounds like a small point source, the decorrelated one seems to fill the entire room.

Finally, in general, HF sources sound smaller than LF sources, and soft sources sound smaller than loud sources.

Unfortunately when I was reviewing this I realized that much of it applies more to architecture than speaker building. The delays involved, from 10 ms and up, can't (hopefully!) come from the speaker. We can only try to avoid time-delayed very early reflections at the speaker's edges, below 0.6 to 0.7 ms, ideally up to 1.5 ms but that would call for a very large speaker. On the simpler side, having low bass at all and in correct loudness, will already help with size perception.

I also have a nagging suspicion that it's the imperfections in the reproduction chain that improve space and size impression: say low channel separation and phase tracking, as presumably in LP's, might actually and unwittingly provide a certain amount of crossfeed and decorrelated time delays that make the sound spacious (!!). Same goes for the time delays involved when listening to line arrays, dues to the different distances to different parts of the line, or the delayed reflections from large diameter horn mouths.

Conversely by the way if any room-speaker-listening position combination sounds "large" the imaging shouldn't be so good (mucho reflections), and vice versa - say widerange drivers in the nearfield, perfect imaging but small-sounding.

In other words I suspect that truly accurate reproduction without reflections probably sounds just like headphones: flat and dull. Because that's what's on most recordings .

FWIW I finally found the sketch on time delay perception, from a presentation by Begault et al., attached.

References:

David Griesinger on space perception
Ptard et al on source wideness
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File Type: jpg delay and echo times begault 2002.jpg (61.5 KB, 965 views)
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Old 11th June 2007, 02:57 AM   #1019
MBK is offline MBK  Singapore
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Lynn,

actually SL does make some references to the problems of SS amps, especially the crossover distortion that would not show up in normal THD plots, and vary with level as well. That might also be a prime candidate as to why high sensitivity drivers could be more picky of amps, they would amplify the crossover distortions because the overall power level is lower to begin with to achieve a given SPL.
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Old 11th June 2007, 08:06 AM   #1020
fiacono is offline fiacono  Australia
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Default 18 and 21 inch drivers

Hi Lynn,

Looking at 18” and 21” drives (as you mentioned) I formulated the table below (click on image) considering the Mms, Sd and the BL factor, and also included the TT to compare.

I am no expert and just learning from these posts.

The 18” Beyma 18G50 has the best ratio’s
My question is that could it replace 2 x 12” drivers or even replace the 3 X 12” drivers and use one TT 12” Alnico for the WR driver and the Neo Pro 5i tweeter for the HF.

I’m considering of building a cheap version for now, any comments appreciated.

Frank
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File Type: pdf speakers.pdf (29.9 KB, 126 views)
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