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filter on the tweeter?
Active (line-level) crossovers, passive line-level crossovers. Or with series and parallel spkr level passive crossovers.
Any differences at all between these topologies?
Also, how effective are the high-pass elements at protecting a tweeter, or midrange driver from excess power, e.g. from a pulled IC when we forget to shut the amp down / turn it down?
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Follow Ups:
I need to learn to ask what I meant! ;-)!
Thanks for all your efforts so far, though.
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Capacitors will protect the tweeter from DC and low frequencies.
They will do nothing whatsoever to protect a tweeter from a clipping or otherwise faulty SS amp as this tends to produce white noise which contains all frequencies at full power.
They will also not protect a tweeter from transients which tend to be high frequency in their very nature ie the faster the signals rise time the higher the frequencies it must contain.
The XOs in 3-way, "true-ribbon" Maggies are engineered with:
* an external section (bass LP/mid HP) and
* an internal section (mid LP/ribbon HP).
The external section was housed in a little box which, in the older models like my IIIas, sat on the floor; the internal section sat in a rebate in the MDF frame, underneath the bass/mid driver.
So the ribbon signal already had to pass through a large series cap in the Mid/HP filter, before it got to the ribbon HP series cap. Magnepan set up the overall XO this way for good reasons but one good tweak was to use a wire for the ribbon that bypassed the mid HP filter and went straight from the external XO input, to the mid/ribbon input terminal. (So the ribbon signal only passed through the (relatively small) ribbon series cap - however, you had to adjust other compoenent values, as well.)
Re. your other Qs:
Active (line-level) crossovers, passive line-level crossovers. Or with series and parallel spkr level passive crossovers.
Any differences at all between these topologies?
Line-level active ... is what I use on my Maggies. It enables the amps - particularly the bass amp - to have an iron grip on the drivers (there being no series inductors "in the way"). It also provides gain to compensate for driver efficiency differences or different amp gains.
Line level passive (PLLXO) ... theoretically less signal degradation than with an active XO and enables the amps to be directly connected to the drivers. But it only has loss (no gain) and for slopes greater than 6dB, you get excessive loss.
Series vs. parallel speaker-level XOs. Again, series tend to only be used in a 6dB-slope XO. In a 6dB XO, I think the engineers would say that series would have identical sound to parallel (and, in fact, uses the same component values, just differently arranged) ... however, people who listen to the music would say series sounds better. :-))
I have read some exposition saying series deals with back-EMF from the bass driver better than a parallel XO.
Peter Gunn, on these pages, has made quite a career of using 6dB series XOs on all models of Maggies (including 20.1s), as he noticed that the old SMG/SMGa - which were the only models until the recent X.7s to use a series XO - sounded very musical.
Also, how effective are the high-pass elements at protecting a tweeter, or midrange driver from excess power, e.g. from a pulled IC when we forget to shut the amp down / turn it down?
Even one series cap used for a 6dB HP filter should protect the driver from amplifier "thumps" ... but, please note, I don't even use a series cap for my true-ribbons - the mid & ribbon amps are directly connected.
Regards,
Andy
Unless you have the ability to change or modify any possible previous "filter" it's a moot point. What comes out of your amp/preamp is what you have to work with.
A passive networks capacitors will protect the tweeter from DC and any AC below the passband depending on the slope. Active no DC protection at all which is why many use DC protection capacitors when running compression drivers in an active set-up
Rob
Jeezzz. I bet hundreds for the average Rock & Roll analog board run multi tape machine and mixed album.
At least for digital mixing and mastering it should be less of an issue in some ways?
Edits: 08/07/12
The signal could "see filters" prior to transcription to media, digital filters in disc playback. (Or an "RIAA" equalization filter playing vinyl.) And various analog filters as it passes through the line stage and power amp. And even cables could have "filter networks" (MIT).
So the answer to the question could vary from zero to over 10, depending on the system setup.
I did mean after it leaves the power amp in the case of the two passive spkr level crossover types, and after it leaves the pre-amp in the case of both types of line-level crossovers.
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
"I did mean after it leaves the power amp in the case of the two passive spkr level crossover types, and after it leaves the pre-amp in the case of both types of line-level crossovers."
It depends on the "order" of the crossover filter. Some crossovers are first order, where it's either an inductor or capacitor filtering the tweeter. Second order is two elements, inductor-capacitor or capacitor-inductor. (Two caps or two inductors can also be used, via intermediate resistor.) Third order is cap-ind-cap or ind-cap-ind. And so on. The higher order means less interference between the drivers (steeper filter slopes), but the signal travels through more devices, which could degrade sound.
I hope this is the answer you're looking for. If not, you might want to provide more specifics.
"I did mean after it leaves the power amp in the case of the two passive spkr level crossover types, and after it leaves the pre-amp in the case of both types of line-level crossovers."
Ok, so you're not concerned with the processing that's done during the production, correct?
***************
Saving the planet, one milliwatt at a time.
Well, in a few months I might be able to for a very few recordings.
I'll be joining (I hope) a small team of volunteer recording folk for live acoustic concerts for our local community arts radio station here in Canberra. We occasionally do direct broadcasts, too.
I'll be learning about the ORTF array for a while, then IF I can afford a mixer a pair of omnis coincident with each cardioid. Later still I'd like to try M-S technique. Requires a Figure 8 and one cardioid, same make / series IIRC - or a matching omni and a figure 8. And a portable dematrixer - given that I'll be wanting to check the balance on phones. and for post production to L & R.
We'll each be responsible for editing and producing our concerts for later broadcast.
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
"I'll be learning about the ORTF array for a while, then IF I can afford a mixer a pair of omnis coincident with each cardioid. Later still I'd like to try M-S technique. Requires a Figure 8 and one cardioid, same make / series IIRC - or a matching omni and a figure 8. And a portable dematrixer - given that I'll be wanting to check the balance on phones. and for post production to L & R. "
That is excellent!!!!
Just know that this has been researched/studied for quite a long time. You would do well to look for articles and papers on the topic.
Still, it's always good when a student pursues the basics of recording, and I hope that you will bring something new to the topic!!
And quite a few other published articles, in fact I've probably bought quite a few single issues of magazines I'd not otherwise buy, because there was a stereo miking article in that issue.I can forget things like the size of the Decca Tree array, but there you go I am over 60!
I've borrowed most of the books on the subject of recording and acoustics in the National Library, the local public library system, and from the University of Canberra where I was once a tutor in 'systems'. I'm now a Life-Member there.
I think I understand 'proximity effect' for example, and how different stereo miking arrays are written down as working.
But, I am looking forward to really learning - which only can happen through doing - and anticipate having to read quite a bit of it all over again in consequence. But then my reading will be more directed.
I am lucky that my system then and still is, capable of revealing what kind of stereo miking was used. A long-term friend is the recording engineer at our Canberra School of Music. He has a single capsule stereo mike hanging above the stage of the School's Lewellyn Hall. One of teh better big halls around.
I have heard some of the tapes he made of concerts, like one of the Academy of Ancient Music, and brought his old Revox G36 here. I had a Hi-Fi VHS recording which I'd set-up on the VCR's timer before my wife and I went to the concert.
We and my wife agreed that we could easily hear the one extra mike used by the ABC to spot-light the soloist Anthony Pay (?) who was playing the basset-clarinet in WAM's 'Clarinet' Concerto, for which it was actually written.
On the night, live, the instrument disappeared 'into the mix' when the orchestral tuttis got loud and Pay was joining in outside his solo score but on the ABC's direct broadcast you could just hear it as a distinct sound even then. Level too high?
For someone who didn't know the score but familiar with the piece from other performances, they might have thought it was strange, or a newly found score. Engineer / producer decision?
The coincident-only - 'bootlegged!' - tape was more like the sound we heard at the concert, in that Pay and his instrument blended back in as as he did on the night, when he wasn't soloing. The engineer's tape was at least as enjoyable in every other way and had more depth, probably because height can exaggerate that with a stereo array.
I am hoping to play around with how that single capsule mike can be moved around on its wires/ropes, and borrow some of the mikes he has available.
Canberra has a lot of live acoustic music going on, some of it free or available to us old folk for a discount, and it's not always being recorded IME. Do a deal with them for a copy, and I'd probably get in for free! ;-)!
This was a memorable concert for another reason, it was in 1988 and I had the day before resigned from the civil service and gone out on my own as a consultant to companies needing to put a case to government on issues to do with industry protection, tariffs, dumping etc.
I took Patricia to the National Gallery near where I worked for lunch and in the restaurant was Christopher Hogwood and the concert manager of Llewellyn Hall. My wife was adamant that I shouldn't go over and talk to them, thinking I'd gush.....
I said, 'Hullo, you are Christopher Hogwood aren't you!' ..... 'Thankyou for your music!" and went and rejoined Patricia. The waiter came a bit alter and they had us join them and they paid for lunch. This was before William Christie and Les Arts Florissant really took off and Hogwood was very interested in what I thought of French Baroque music and its future market.
Chris gave us good tickets right near where the reviewer's used to sit and passes for the after party for the next night's concert.
That same afternoon I'd been invited to a cocktail party by the President of the Specialty Chemicals Manufacturers Association of Australia. Because I'd resolved an anomaly in rates of tariff applying to the same product but with different fibres for his company Cussons, Australia.
By 'tabling' a Tariff Amendment in 'the House' resolving the anomaly using the then Gov'ts stated policy of no anomalies of that kind as the reason and, as usual with Tariff Amendments, not a murmur from the members or later the Senators. He'd also taken me to lunch and had written me a recommendation for me to use in my marketing.I was greeted by the president, given a drink, and taken over to a group which turned out to have a few senior guys from my Department (of Industry). One of whom, recently but no longer my boss, said in surprise "What are ~you~ doing here, Tim?!" So, I nodded at our host and winked, and he told him.
And then I said, 'I think I know how the system works, don't you?!'. Stunned silence, and then one of the directors under him in his new Branch, said, "I think we've been underestimating you, Tim!".
I walked form the hotel to the Hall, met Patricia and went to the concert and after party.
Chris H. later sent me an autograpphed copy of his book on Handel.
Memories, eh?! ;-)
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Edits: 08/07/12 08/07/12
Ever tried a Soundfield mic to record?
I also have quite a few articles on the research, the patents and the mike itself.
Nearly all of them are hard copies and alas my printer is only partly compatible with W7, so with the only driver I could find for Vista? it won't scan.
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
We've had one at college and they can be quite remarkable at conveying the space the recording took place in.
If I had the cash I don't think I'd bother with Decca trees and suchlike anymore.
Although I'd always have space for the Neumann head…
but there's the decode box as well. Longgg cables ......
:-)!
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Over here they cost between £3800 and £5400 depending on model including the decoder.Which is actually a little bit less than the Neumann KU 100 artificial head and no more than a vintage Neumann U87 or such like or a new Blue tube condenser.
PS: Calrec spun off Soundfield in '93 into a separate company, similar to Bruel&Kjaer spinning off recording mics to DPM to concentrate their efforts on measuring systems.
Edits: 08/09/12 08/09/12
Hey Timster, THAT was a GREAT story!!You and MarantzGuy (on the Tape Trail forum) need to have a talk. :)
Here's your "assignment": Record a performance using ALL "typical" microphone placement techniques - XY, ORTF, A-B, Decca Tree, M/S, spot-miking, etc. You'll need to use high quality mics, preferably the same brand, or, better yet, the ones most typically use for each setup. Use BOTH cardioid and omni for the A-B setup. You'll need at least sixteen mics and tracks to do this. Record at 24 bits (for maximum sn) and 88.1 or 96 sampling (for time resolution). Use good stuff.
I've given this assignment to other budding recording "engineers". It's an eye-opener. (I put "engineers" in quotes because, at last count, there is no recording engineering 4-year degree program, yet we continue to use the term.)
One tip: Pick-up pattern characteristics are critical. That's all I'm sayin'.
You might want to look at this web page for a bit of insight. It's not in-depth, but is a good introduction:
http://www.youramerica.net/recordingtechniques-part1.htmAlso, microphone manufacturer Schoeps has a very good synopsis of various techniques. Sorry, I don't have the web page address handy - just google Schoeps microphone technique, and you'll be close to it.
Edits: 08/07/12
Audiences here are intolerant of mike forests.
BUT if we used a Calrec Sound-Field mike we could generate all those, except the spaced omnis and Tree.
I think I'll start with ORTF and grow from there, eh?
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
"how effective are the high-pass elements at protecting a tweeter, or midrange driver from excess power, e.g. from a pulled IC when we forget to shut the amp down / turn it down?"
In general further the transient is from the filter passband the better. I'd assume that the tweeter will be fine, the midrange probably although it depends on the filter detail and the woofer toast if the transient is "DC" and it isn't fused.
As you can tell I tend to worry about it a bit also... Dummy loads or series resistors that you short after things are stable can be cheap insurance.
Rick
I had DC in my system once. Fortunately, nothing melted. (See link to old post.)
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
"Dumb Q'n how many filters..."
I'm not sure what Q'n means.
Probably just a typo, but I can't figure it out.
Maybe it's an Aussie thing. ;)
okay? :-)!
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Ah, "question". Why didn't you say so? :)
How many filters? Well, I guess that depends on how many tracks and how much SP went on before it got to the final product.
Unless it was one of my (or MarantzGuy's) recordings, it probably went through the proverbial wringer before it got to you, so, no worries about it sounding "real" - just listen and have fun.
:)
And I prefer recordings that are the least futzed with, but even they can use eq on the mikes.I'm doing another quite complex typing job and wanted to be fast.
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Edits: 08/06/12
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