I believe it comes down the fact that an amplifier & loudspeaker have to be considered as a system. In today's world, or at least not that long ago, a significant majority of speakers assummed a voltage source amplifier & hence tended to work best with any random amp that was more or less a voltage source/low output impedance. ie a chiken & egg thing.
But as diyers we are not constrained by many of the marketing considerations that typical retail oriented manufactures are constrained by.
Having a variable transimpedance amplifer here, and a wide range of speakers -- many of them built without the "gonna be driven with a voltage source" paradym, it is very clear that for every loudspeaker there is an appropriate output impedance, many of mine tend to like highish output impedances.
dave
Parts shipped from DK today. Give the mail a few days and a few days to get them in. To keep entertained, I am putting in the schematic for the RB-951 and RA 840 to see if there is any trend. Rotel was nice enough to leave the values off a few parts in the schematic, so I have to open it up to see. It has a few things in the schematic I don't quite understand yet. I will study before I ask.
Dave,
I experimented with current drive and motional feedback back in the 80's and this was hardly the beginning.
The fundamental problems of "Voltage drive" to speakers have been documented for a long time, however as with so many other issues in audio (useless measurements like THD, (T)IMD, Dumping Factor etc) the audio engineering community by and large has elected to follow the course often ascribed to the majestic Struthio camelus; that is to burry it's collective head in the sand and hope those beastly anderdenker (differentthinkers) will eventually go away, a hope in which they have generally so far been confirmed.
Ciao T
I experimented with current drive and motional feedback back in the 80's and this was hardly the beginning.
The fundamental problems of "Voltage drive" to speakers have been documented for a long time, however as with so many other issues in audio (useless measurements like THD, (T)IMD, Dumping Factor etc) the audio engineering community by and large has elected to follow the course often ascribed to the majestic Struthio camelus; that is to burry it's collective head in the sand and hope those beastly anderdenker (differentthinkers) will eventually go away, a hope in which they have generally so far been confirmed.
Ciao T
Some old posts you made on the subject, and a long talk with an old WE engineer that started me thinking about current drive.
dave
I did not experiment with current drive, but theoretically it should work well if enclosure is stiff and well damped. I experimented with feedback by acceleration. It worked extremely well, but I neglected rumble filter and damaged the driver. Later I experimented with negative impedance, it works almost as good as feedback by acceleration, however in terms of frequency response only. If to go for lower distortions I would go for current drive, but I have too much of other work to do now...
This point of view is a common one at present, but it is oversimplified, as usually.
I have got numerous confirmations, that output impedance alone does not describe amp-speaker interaction, there are also differences in how exactly amp damps out the speaker back emf, there is a kind of transient reaction of an amp on the back emf applied.
Given two different amps (on with current NFB and another with voltage NFB, for instance) have the same output impedance, with the same speakers, they produce quite a different bass.
And if one amp, having 0,5 Ohms output impedance, produces more articulated bass than another amp with 0,05 Ohms output impedance, this does not mean that speaker crossovers were optimized for 0,5 Ohms. Most probably, this means that the first amp has more beneficial transient reaction on back emf.
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Of course it is more complex than that. How much the backEMF screws up the amps performance is another factor, and i think what you are trying to desctibe.
dave
I should have the impedance modulus schematic somewhere, I'll dive into my log and God help me.
The bottom line is: nominally 8 Ohms, minimum 6.5 Ohms at 220 Hz, worst case phase shift -25 degrees, reflex principle with port tuned to 38 Hz for best low response linearity.
As for B&M Acoustics, no wonder you couldn't find anything, as they have ceased trading some years ago. A very sad story. B&M are the initials of the two partners who founded the company around 1994. Now, "B" (Blaža) was the moneyman, looking out for the financial side, and "M" (Mirko) was the sonic brains, and I daresay, a hell of a brain. Also a well beloved friend of mine.
Anyway, I took some of my ideas to "M", mostly related to speaker upgradeability, how to take it in steps from a classic passive system to a bi-, tri-amped and eventually all the way to fully active. We got down to it and had the box in three weeks of hard work. After that, it took us just short of six months and like 60-70 auditioning sessions to get the crossover just right, involving a panel of more than 20 people (not all at once, though), about evenly spread from professors at the School of Music, University of Belgrade, to rock musicians.
We did it, and my pair bears the proud serial number of "00001". And sales started to take off, "M" had people actually driving down from Belgium and Netherlands to hear them, and all of thzem went back home with a pair, two with actually two pairs.
End of fairy tale here. "B", who was a motorcycle freak (with wild driving only on races, not on the streets), had an accident on what was to be his last race. Today, he is 100% paralyzed from neck down, lives in a wheelchair with plasitc bags underneath it for excrement, and must be hand fed every 20 miutes or so. Horror as one cannot imagine. Perfectly aware of everything, his spinal chord was severed by the crash. This caused a radical change of his personality, and a friendship of over 22 years was severed. The company dragged on for a few months after "M" left, but evetually wound down.
That's why there's no more data on them. One of the greatest pities and regrets I have ever had in my life, I believe a true loss all around.
Since the basic idea was mine, "M" adopted my name for it - 1041 Monitor. Actually, it's my little hommage to JBL's 4312 Monitor, which I tried to pruchase several times in my life, only to fail for whatever reason. "10" is for the 10 inch aerogel woofer, "4" is for the 4 inch aerogel midrange and logically, "1" is for the 1 inch titanium dome tweeter.
This is it:
As you can imagine, there is no chance of me ever getting rid of it. I actually keep spare drivers in my cupboard; I was called the ultimate freak because of it, but now that Son Audax has ceased to exist, I wonder what those same people would call me now?
On sample size - agreed, not so much about the number of units as about the fact that it's the same manufacturer, but that was all I had. Anyway, my point was that you can use any technology to this or that end - I don't particularly like tubes, but I've heard some wonderful tube audio products, I don't much like MOSFETs, but I've heard some great products, etc. You can make great and awful products with ANY technology, no matter how antiquated or progerssive it may be on its own. Those who really KNOW will find a way to put it good use.
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Isn't the term "klugscheiser" (excuse the spelling) a wonderful, wonderful German term for oh so many modern "gurus"?
Roughly translated as "wisdom shi**ers".
I am constantly reminded of Clint Eastwood and his comment - opinions are like a** holes, everybody's got one.
And the stereotype has it that Germans have no sense of humor ...
This word proves just how wrong that stereotype is. That one and several others regarding Germans and Austrians, too. People ask for Danish bakery products, and having been in Denmark, Austria (where I have relatives, my grandmother was pure Vienese for 7 centuries, family name Schniedershitz - hi, gk7, my 25% countryman
) and Germany, let me tell you folks that a short stroll in Vienna, Munich and elsewhere around 8 in the morning will have you drooling, and if you should walk into a bakery, you're done for the day. Copenhagen, nice as it is, doesn't even begin to compare.Thorsten, gk7, am I telling the truth?
Hi,
Well, I do like Schwarzwälder Kirschtorte and kalter hund, but I'm also partial to an Apple Danish, a Sakura Cake, a Blueberry Muffin, Boston Pie, Beijing Dao Xiang Chun black Cake with nuts and many other baked products.
IMNSHO, it is really the bread and beer in most places, compared to Germany, that really lets them down.
Ciao T
Well, I do like Schwarzwälder Kirschtorte and kalter hund, but I'm also partial to an Apple Danish, a Sakura Cake, a Blueberry Muffin, Boston Pie, Beijing Dao Xiang Chun black Cake with nuts and many other baked products.
IMNSHO, it is really the bread and beer in most places, compared to Germany, that really lets them down.
Ciao T
Gee, Thorsten, how terribly you suffer day in, day out ...
"IMNSHO" = In My Not So Honest Opinion" ?
Bread - a resounding YES on that. NOBODY I have ever seen in my life has as many types of somehow always fresh bread as the Germans do, at least the Bavarians in Munich. Every time I go there, I am amazed anew.
A word of caution to the uninitiated - be VERY careful with German wholemeal dark types of bread. It's legalized dope, you can't eat just one slice, you have to have at least two, and of each type on the table. It's so tasty that you don't even need the butter (which is as good as New Zealand prime choice, if not better, the Alpen type especially). You can have the breakfast of your life even in mediocre hotels, let alone the good ones, but 30 to 45 minutes later, things happen.
You experience extreme slew rate limiting, with intermodulation gallore, and you discover just how fast you can sprint back to the room, in search of a toilet.
Honest! Happened to both wife and myself way back in 1986, and remember, we are from Serbia, our national cuisine usually has the lot of you Westeners doing that over here because it heavy and hard, but tasty like hell. Now, if we sprint back, you guys fly back.I am now tempted to say you don't really know what bread is until you've been to Germany. I surrender to this temptation.
Stereotypes are usually untrue and sometimes a little malicious. For example, most Europeans will say that Amercan beer is junk. And it is, if you think of Budweiser and Miller, but don't forget Beck's, whichs is German, and which also has its breweries in USA. And those near Boston have the blessing of John Adams beer, which I am pleased to say was one of the best beers I have ever tasted, at least in 1991, when I drank it last.
And as everybody knows, life in the Solar system would not be possible without Louisianna's Tabasco sauce - which is why I keep a bottle of it in my bag at literarlly all times, day and night. Had it in my bag since 1967, when I was inhumanely exposed to British cuisine for three dreary years. But also to British jams and marmelades, I'll bet money the best on this world, and British biscuits, salty, neutral and sweet ones, also the best I have ever had. Got addicted to McVittie's Jaffa Cakes there and never stopped, thank God a local company makes 'em under licence.
Last but not least, Britain has by far, and I mean BY FAR the best cider in this corner of the universe. French cider is pi**water, don't even think about it.
As for local, well, it's useless to brag, you just have to try it yourself. It's truly extremely varied, but is definitely meat based. The best comment on it was delivered by one Jay Huntignton III, professor and PhD, pre-Catrina of New Orleans, now somewhere in its suburbs. After about 20 minutes at the lunch table, he was puffing and panting, mumbling: "My cholesterol levels will never be the same!", but still going strong. And Jay is a southern boy, well intiated in spicy and heavy food stuffs.
Your survial kit for Serbia are two boxes of Alka Seltzer.
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