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post #61 of 88 Old 07-23-2011, 05:59 AM
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Agree with you on the bass, AJ. It's only a gut feeling, but at the consumer level, I don't think you'd see the same reliability.

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post #62 of 88 Old 07-23-2011, 06:02 AM
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Quote:
Originally Posted by Chu Gai View Post
if you can't afford the repairs on an expensive car, don't buy the car.
If you can't afford the repairs on an expensive active speaker, then don't buy it. Plenty of 'high end' companies have gone under over the years leaving people with electronics that are unservicable, except with the knowledge of a good tech.

Actually having spent a couple of decades working on analogue electronics, I have a slightly different view of what can be done than the average consumer.

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post #63 of 88 Old 07-23-2011, 06:04 AM
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Originally Posted by Chu Gai View Post
Agree with you on the bass, AJ. It's only a gut feeling, but at the consumer level, I don't think you'd see the same reliability.
Why? Where do you think a lot of the electronics for these pro units are made? By elves in Greenland or the similar production lines in PRC?

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post #64 of 88 Old 07-23-2011, 06:58 AM
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The elves are in Ireland. Like I said it's just a gut feeling. The marketplace will decide whether actives develop a significant market share. Let's check back in 5 years.

"I've found that when you want to know the truth about someone that someone is probably the last person you should ask." - Gregory House
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post #65 of 88 Old 07-23-2011, 07:44 AM
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Originally Posted by Chu Gai View Post
The marketplace will decide whether actives develop a significant market share. Let's check back in 5 years.
Who cares? I personally don't give a flying fvck what the market thinks because I'm not selling anything. It is not about what the sheep think but what actually works better. Like I care if anyone thinks McDonalds is actually good food.

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post #66 of 88 Old 07-23-2011, 09:13 AM
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Quote:
Originally Posted by A9X-308 View Post
It may be too early in the morning for me and/or some translation issues, but this isn't making sense to me ATM. What is "impedance distortion"? And I'm not seeing how a higher source Z will make much difference to thermal compression beyond ratiometric values in a source Z/load Z divider. In practical terms, how much difference does what you're suggesting actually make? Got measurements or online articles to explain this effect in speakers?
Well, what I mean by "impedance distortion" specifically is that part of a drivers distortion comes from nonlinearities in the electrical motor system (i.e the impedance is "modulated" as a function of voicecoil position in the motor system). If driven by a pure voltage source this modulation will result in distortion (since sound preassure is proportionate to voicecoil/membrane acceleration, which is proportionate to the current flowing through the voicecoil). The current and hence sound pressure will not be modulated (and distortion will be lowered) if the voicecoil is driven by a pure current source.

Now, when using a pure current drive, it will take care of both the impedance change that comes from the voicecoil inductance as well as the compression due to thermally induced resistive change in the voicecoil.

In real life, however, things are sooo much more complicated due to the fact that any distortion optimization you do this way will also alter the freqency response (ouch!), and the effect of the "distortion control" will vary across the frequency range.

However, if you have the knowledge to design the drivers as well as the XO, you can lower the distortion several dBs in critical frequency bands (I've seen claims of 5-10dB) and maintain a flat frequency response for the finished speaker.

An active filter in combination with distortion optimizing passive network would make real sence, IMHO.

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post #67 of 88 Old 07-23-2011, 09:26 AM
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I'm sure the OP is gone by now. He wanted subjective advice about different routes from London to Rickmansworth, and he got advice on trips to Shanghai, the moon, and Jupiter.

What I can afford, when I can afford it...
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post #68 of 88 Old 07-23-2011, 09:26 AM
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I've seen claims of 5-10dB

I've not. Something to substantiate the claims would be nice.

“You are not special. You are not a beautiful and unique snowflake.” Chuck Palahniuk
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post #69 of 88 Old 07-23-2011, 11:39 AM
 
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Quote:
Originally Posted by Chu Gai View Post

If that's the case, I don't ever see actives making any significant dent in market acceptance.

Active are coming in through a variety of back doors:

(1) Conputer speakers

(2) "Sound Bars" for your new HDTV

(3) Pro and quasi-pro "studio monitors".

I see receivers as also wll on their way onto the endangered species list.
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post #70 of 88 Old 07-23-2011, 12:36 PM
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Quote:
Originally Posted by terry j View Post

nahh, not using them, but they can wait till then. You prob need the space!

Quick point on converting a factory speaker to active. WE might be able to do it easily enough, but the average audiophile (specially those into the 'tweaks'???)

Forget it. They are almost universally of the opinion measurements don't matter anyway! So take the effort to learn about measurements (as you need to)??

Forget about it.

(Tess, where do you fit into this?? What are your thoughts here?)

And as chu pointed out, they also lose the ability of 'vast' upgrades thru amps blah blah blah.

Make no mistake, I think they are major obstacles.

I think you are stereotyping. The active XO audiophile crowd is growing, objectivists do not have a monopoly on audio knowledge.

I am entertaining doing this myself with my next speakers (Chase SHO-10), or the ones following that, which I will construct myself along the lines of the Econowave. Yes I will have to throw aside the passive network, as well as my integrated amp, buy a preamp, active XO and two stereo amplifiers. It will take time, but I already have a handle on how it all works after being a "doof doof" installer for 19 years. I was into SQ, not SPL.

First I am going to get a dedicated laptop, mic, pre, REW (yes I am going to work on my room first, this is more important than passive vs. active) and then pick and choose relevant software for dialing in the actives. On my budget, this isn't going to happen overnight. I may decide in the end that the passives are all right. Geddes is good to go with passives, so is LeJeune and Parham.

That said, the advantages of active over passive are undeniable. The problem is not that your typical "audiophool" cannot be bothered to convert because of some archaic beliefs, it is because the general public at large is satisfied with the status quo.

This puts people like yourself at the fringe, Terry. There is the cost of separate drivers, amps, XO's, processors, build out, the learning curve, the set up time involved, most people will not bother themselves with that. Think home theater, not just 2 channel. Very complex for the average Joe. That type of dedication is for hobbyists.

I would like to see the consumer audio market lean more towards a preamplifier/signal processor with powered speakers type of system. You buy a speaker, it comes with a dedicated XO and amp, you plug it into the preamp and go. Unfortunately, right now it is cost prohibitive from a manufacturing and customer service point of view. Putting those manufacturing processes in place, and the engineering support those processes need to get started, isn't supported by the market. It won't pay off and will fail. Maintaining these products when they break will cost more, also not a popular prospect. Yes, I do realize that systems like these already exist (TACT for example). Complex and costly, supported only by fringe enthusiasts.

People don't care, what they have now works. Is it as good as it could or should be? No.

"Women and cats will do as they please, and men and dogs should relax and get used to the idea." -Robert A. Heinlein
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post #71 of 88 Old 07-23-2011, 12:46 PM
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Quote:
Originally Posted by Chu Gai View Post

How would consumers react when they start reading the electronic crossover is warranties for 2 years? Or that 5 years later the board can't be replaced because it's been discontinued. Or that it can't be serviced.

Agreed. This is part of what I am trying to convey.

"Women and cats will do as they please, and men and dogs should relax and get used to the idea." -Robert A. Heinlein
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post #72 of 88 Old 07-23-2011, 12:53 PM
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Quote:
Originally Posted by AJinFLA View Post

Don't follow the logic here Chu. Zillions of active monitors/PA speakers are sold in the pro world. Gigs and livelihoods can depend on them. If failure rate concern is as you characterized it, one would think there would be very little market of active PA/monitors no?

These active monitors have been around for years and still haven't caught on in the domestic market. Remember the Paradigm Active 20/40's? Great speakers... long out of production. Sad, isn't it? So what can we do about this?


Quote:


btw, if an active system sounds markedly better than a passive one, it would only be indicative of incompetence of passive design, not passive design per se. Insert caveats here.
Needless to say, IMO, non-active (passive) bass in just plain silly.

Agreed, I use passives between my mids and highs (in my car or my house), but my bass is always active. Still, the advantages that are afforded active bass can be applied to high FR drivers, too.

That said, I think passives do a fine job if designed competently.

"Women and cats will do as they please, and men and dogs should relax and get used to the idea." -Robert A. Heinlein
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post #73 of 88 Old 07-23-2011, 01:18 PM
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Quote:
Originally Posted by arnyk View Post

I see receivers as also wll on their way onto the endangered species list.

As soon as a mainstream/leadin brand like B&W, Paradigm, Polk, Harman, or Klipsch comes out with budget active speakers, entry-level pre-pros will penetrate the market. Most modern receivers have two-bit amp sections anyways - doing away with them just make sense.

And with bi/tri amped systems, marketers still add up wattage. "30 + 50 + 100 watt amps for 190 watts of powers " (p.s. it adds to 180)
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post #74 of 88 Old 07-23-2011, 01:22 PM
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Deceased:

http://www.stereophile.com/standloudspeakers/597/
http://www.soundstage.com/revequip/p...m_active40.htm

It will take a paradigm shift to bring speakers like this back. No pun intended.

"Women and cats will do as they please, and men and dogs should relax and get used to the idea." -Robert A. Heinlein
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post #75 of 88 Old 07-23-2011, 01:44 PM
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Quote:
Originally Posted by A9X-308 View Post

I've seen claims of 5-10dB

I've not. Something to substantiate the claims would be nice.

Sure.

Here's an example using a Seas CA18RLY 6.5" mid/bass driver. The measurement is particularly interesting since the sound pressure at the measurement microphone is kept (nearly) constant during the whole frequency range using a minimum phase digital equalizing filter calculated using the Hilbert transform of the raw frequency response.

Now, the first graph show the CA18RLY driven directly by a competently designed SS power amp (=low output impedance).

The second graph ("-S") shows the exact same setup but with a 0.8mH coil in series, and the third graph ("-S2")shows the setup using two 0.8mH coils in series with the CA18RLY.

As you can see, there is a significant reduction in distortion from the driver in in the midrange where the nonlinearities in the motor system inductance is contributing to the distortion significantly (the mass controlled range).
LL
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LL

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post #76 of 88 Old 07-23-2011, 02:58 PM
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Hi Tess

Quote:
Originally Posted by tesseract67 View Post

I think you are stereotyping. The active XO audiophile crowd is growing, objectivists do not have a monopoly on audio knowledge.

Really? Well no more stereotyping than this bit..

Quote:


This puts people like yourself at the fringe, Terry. There is the cost of separate drivers, amps, XO's, processors, build out, the learning curve, the set up time involved, most people will not bother themselves with that. Think home theater, not just 2 channel. Very complex for the average Joe. That type of dedication is for hobbyists.

Which is precisely what I said earlier no?

And yes, those ARE the reasons that converting a passive manufactured speaker to active is, and will remain, rare. Not to mention warranty etc etc, resale value...


What happened to your idea of getting the gedde's speakers? Did that change along the line?

Just to backtrack a little, pray tell what audio science knowledge do the subjectivists bring to the table? You know, stuff that has not had to be force fed down their throats, which takes years...stuff that does not come straight out of a marketing promo?

You agree that active bass in needed, well YOU would be in a minority of subjectivists, you realise that? Most ARE of the opinion 'bugger the measurements, if it sounds good it is good'.

And you can acclimatise to a sound you know, no matter how shocking the bass response is..and 99% of the subjectivist out there will have shocking bass. Yet they are blissfully unaware (not a bad thing I spose!) and yet will prattle on about fast and slow bass, small bass drivers being faster than large bass drivers...

C/mon Tess, the world of the average subjectivist is a muddle of poorly understood and just plain wrong audio 'wisdom'.

If you personally don't fall into that camp then great, how about helping *us* next time we attempt to educamate some of these bloke eh?



Quote:
Originally Posted by AJinFLA View Post


btw, if an active system sounds markedly better than a passive one, it would only be indicative of incompetence of passive design, not passive design per se. Insert caveats here.
Needless to say, IMO, non-active (passive) bass in just plain silly.

[Can I say I very much like the new improved AJ? That is now TWO posts in a couple of days that was well argued, yet without any withering putdown of someone else or the rabid expousal of 'I am right and all others are wrong'. Not that what I think is of much importance]

I too want to back up one of these points. There seems to be a thought of mind that going active automatically ensures it will 'murder the passive variant'.

Just another of these mindsets we see in audio.

A well designed and executed passive can do a damned fine job too. And in many cases simply doing a 'bit for bit' swap to active (same xover points, slopes yada yada) will not actually realise a sonic benefit.

To my way of thinking it is only by utilising the 'extras' that active can bring that we move ahead.

One last one, WHY is active bass the only way? Here it is once, and Tess just before.

Active per se on the bass, schmactive. It in itself won't do any better job than passive (or if so why so)
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post #77 of 88 Old 07-23-2011, 03:32 PM
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Quote:
Originally Posted by terry j View Post

Really? Well no more stereotyping than this bit..

It's a fact. Most people will not bother themselves with that. How is that stereotyping? Full on active systems are complicated and the realm of hobbyists. Besides, you are just thinking 2 channel I suspect... think home theater.

Quote:


What happened to your idea of getting the gedde's speakers? Did that change along the line?

Geddes has priced himself out of my range, I can't even afford the once affordable Nathan. The SHO-10 should give me much of what the GedLees offer, in fact one GedLee owner has compared the SHO-10 favorably against the Abbey. I have no illusions of parity between the two, but I can come close, save money, and have it now instead of a year or two from now.

Quote:


Just to backtrack a little, pray tell what audio science knowledge do the subjectivists bring to the table? You know, stuff that has not had to be force fed down their throats, which takes years...stuff that does not come straight out of a marketing promo?

You agree that active bass in needed, well YOU would be in a minority of subjectivists, you realise that? Most ARE of the opinion 'bugger the measurements, if it sounds good it is good'.

And you can acclimatise to a sound you know, no matter how shocking the bass response is..and 99% of the subjectivist out there will have shocking bass. Yet they are blissfully unaware (not a bad thing I spose!) and yet will prattle on about fast and slow bass, small bass drivers being faster than large bass drivers...

C/mon Tess, the world of the average subjectivist is a muddle of poorly understood and just plain wrong audio 'wisdom'.

If you personally don't fall into that camp then great, how about helping *us* next time we attempt to educamate some of these bloke eh?

THIS is stereotyping.

Quote:


[Can I say I very much like the new improved AJ? That is now TWO posts in a couple of days that was well argued, yet without any withering putdown of someone else or the rabid expousal of 'I am right and all others are wrong'. Not that what I think is of much importance]

Perhaps he has realized the folly of his ways? Naaaah. He has a market to break into. I'd still drink a beer with the bastid.

Quote:


I too want to back up one of these points. There seems to be a thought of mind that going active automatically ensures it will 'murder the passive variant'.

Just another of these mindsets we see in audio.

A well designed and executed passive can do a damned fine job too. And in many cases simply doing a 'bit for bit' swap to active (same xover points, slopes yada yada) will not actually realise a sonic benefit.

To my way of thinking it is only by utilising the 'extras' that active can bring that we move ahead.

One last one, WHY is active bass the only way? Here it is once, and Tess just before.

Active per se on the bass, schmactive. It in itself won't do any better job than passive (or if so why so)

I didn't say active bass was the only way. I said that I do it. I almost put the caveat in there that this is on the fringe of the hobby, but it is not. Active bass has become very popular. Were it not for an all in one solution (almost, HT runs an LFE feed which depends upon the pre/pro), if active sub bass were to depend on separate drivers/XO/amp, it wouldn't be as prevalent.

Another simple fact is, mids and highs do well with like placement, bass has it's own demands. It makes sense to isolate them, not only in physical space but electrically as well. All in one subwoofer solutions have made this easy and popular. I don't see any commercial all in one active XO/amp/tweeter or XO/amp/mid solutions out there, so passives rule the day in those applications.

"Women and cats will do as they please, and men and dogs should relax and get used to the idea." -Robert A. Heinlein
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post #78 of 88 Old 07-23-2011, 04:04 PM
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Quote:
Originally Posted by tesseract67 View Post

It's a fact. Most people will not bother themselves with that. How is that stereotyping? Full on active systems are complicated and the realm of hobbyists. Besides, you are just thinking 2 channel I suspect... think home theater.

Ahh, I see my mistake. When I said the following

Quote:
Originally Posted by terry j View Post

Quick point on converting a factory speaker to active. WE might be able to do it easily enough, but the average audiophile (specially those into the 'tweaks'???)

Forget it. They are almost universally of the opinion measurements don't matter anyway! So take the effort to learn about measurements (as you need to)??

Forget about it.
.

I actually meant the very thing you posted..in other words I just misremembered what I actually said and only remembered what I meant to say. And we agree, the average joe does not want to, or not interested in, learning what it takes to convert a passive to active.

BUT, whether or not you feel it is stereotyping, I completely hold to my statements that most out there do not care about the measurements. YOU are an exception Tess, not the rule. And, if I may, it seems to me you yourself have moved quite a lot in the few years I have 'known' you. Not an insult, but perhaps you have not quite realised that?



Quote:


Geddes has priced himself out of my range, I can't even afford the once affordable Nathan. The SHO-10 should give me much of what the GedLees offer, in fact one GedLee owner has compared the SHO-10 favorably against the Abbey. I have no illusions of parity between the two, but I can come close, save money, and have it now instead of a year or two from now.

Ahh, ok. The prices have gone up then eh?

Quote:


Perhaps he has realized the folly of his ways? Naaaah. He has a market to break into. I'd still drink a beer with the bastid.

I suspect it could very well be that he now has to present an acceptable face to the public. Hmm, would THAT not be an eye opener to him?

Just for larfs I should go and check out his de facto sales thread on AC, see the new AJ in all his friendly splendidness.

Actually, even based on the very small recent sampling of the new and improved, he is very much more effective! If they stay the same way, I look forward to more of it. They are now helpful, thoughtful and instead of ensuring automatic dismissal from most, they now penetrate and invite inspection.

Very small sample size, but I like the new version very much.



Quote:



Another simple fact is, mids and highs do well with like placement, bass has it's own demands. It makes sense to isolate them, not only in physical space but electrically as well. All in one subwoofer solutions have made this easy and popular. I don't see any commercial all in one active XO/amp/tweeter or XO/amp/mid solutions out there, so passives rule the day in those applications.

Sorry bout 'the only' way bit, was not intended to be that broad. Still, this argument above whilst true, seems to me to be more an argument for seperate subs, rather than active per se.

So again (to any and all) active per se on the bass? What does that alone bring?
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post #79 of 88 Old 07-23-2011, 04:20 PM
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Quote:
Originally Posted by terry j View Post

BUT, whether or not you feel it is stereotyping, I completely hold to my statements that most out there do not care about the measurements. YOU are an exception Tess, not the rule. And, if I may, it seems to me you yourself have moved quite a lot in the few years I have 'known' you. Not an insult, but perhaps you have not quite realised that?

No slight taken, I thank you. I am here to learn and share.

Quote:


Sorry bout 'the only' way bit, was not intended to be that broad. Still, this argument above whilst true, seems to me to be more an argument for seperate subs, rather than active per se.

So again (to any and all) active per se on the bass? What does that alone bring?

When you biamp, clipping the woofer will not be heard in the tweeter, in simplest terms. Good solid electrical reasoning. (I do digress here, as I run my mains full range. Still, I realize the same electrical advantage in my pseudo biamp system).

Mids and high drivers generally like to be well away from room boundaries, bass driver like boundary reinforcement. Good solid physical reasoning.

Terry, you already know this!

"Women and cats will do as they please, and men and dogs should relax and get used to the idea." -Robert A. Heinlein
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post #80 of 88 Old 07-23-2011, 04:43 PM
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Quote:
Originally Posted by tesseract67 View Post

When you biamp, clipping the woofer will not be heard in the tweeter, in simplest terms. Good solid electrical reasoning. (I do digress here, as I run my mains full range. Still, I realize the same electrical advantage in my pseudo biamp system).

Mids and high drivers generally like to be well away from room boundaries, bass driver like boundary reinforcement. Good solid physical reasoning.

Terry, you already know this!

Clip the woofer?

Well, get a better woofer! (or amp, whatever, that is just adequate engineering for the job)

Yep, good solid physical reasoning, put the (seperate) subs in the best position, the mids in theirs.

Nothing (yet) about active bass.

Of course I know tess! I don't disagree about using active bass, I do it myself. But I am arguing it is not active on it's own that brings the benefit, so what does?
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post #81 of 88 Old 07-23-2011, 05:11 PM
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My only bi-amping experience is with a pair of Klipsch XF-48 Floorstanding Speakers . . . which are also actives:
Quote:


SPECIFICATIONS
AMPLIFIER: HF: Class A/B, LF: Class D [POWER: 100W|360W peak]
FREQUENCY RESPONSE: 40Hz-23kHz +/-3dB
HIGH FREQ CROSSOVER: 2550Hz
LOW FREQUENCY EXTENSION: 33Hz


I typically run the XF-48s as LARGE, either "pseudo bi-amped" with a SUB (both 'Y-connected' to the AVR's L|R Main PreOuts, and AVR configured SUB=NO), or with a SUB 'conventionally' attached to the AVR's SUB PreOut (and the AVR configured SUB=YES and ExtraBass=ON); the XF-48 has a very well behaved|smooth roll-off to handle any Bass input below the speaker's actual frequency reproduction floor. I select whichever of the two configurations produces the smoother Bass response (as a function of the room geometry).

The only 'negative' I have for the XF-48 is that its performance is sensitive to the distance from the closest wall . . . but that seems UNLIKELY to be related to its active|bi-amped nature given the speaker's effective frequency reproduction floor performance of 33Hz. Other than that, the XF-48 performs pretty much like all my other speakers.

And the big plus is that the XF-48 runs really COLD as a consequence of the optimized on-board amps.

Count me "happy".

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post #82 of 88 Old 07-23-2011, 05:35 PM
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Originally Posted by terry j View Post

Clip the woofer?

Amp. Clip the woofer's output.

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Well, get a better woofer! (or amp, whatever, that is just adequate engineering for the job)

The woofer's greater power draw and lower sensitivity is usually the culprit when the amp clips. Better amp, better driver... regardless it is better still to separate them electrically so the tweeter cannot reproduce the HF hash that is generated by clipping. That is adequate engineering for the job.

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Yep, good solid physical reasoning, put the (seperate) subs in the best position, the mids in theirs.

Nothing (yet) about active bass.

Of course I know tess! I don't disagree about using active bass, I do it myself. But I am arguing it is not active on it's own that brings the benefit, so what does?

Oh, you must be getting at signal processing. What else could there be besides the physical and electrical benefits? I don't need to EQ for flat response, I do use an active XO for low pass. I use multi subs and full range mains to knock down the room modes under the Schroeder frequency. But I get your point.

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post #83 of 88 Old 07-23-2011, 05:58 PM
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Yeah, that was it Tess!

All the rest is just engineering as you have shown. I really do agree with AJs point about well engineered passives.

So it's not active as such that brings the benefits, it's the extras (Ithat you may or may not need, you don't seem to need it for getting flat bass response for example) that active brings to nthe table.

IMO and IME (with a few experiments)

ETA

And, as mentioned before, to the average audiophile, in a lot of cases it is 'pointless' to measure the system, if you cannot or will not do anything about it. Why bother? In that case, it IS of 'academic interest only'
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post #84 of 88 Old 07-23-2011, 06:36 PM
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In spite of all that, I still find much to admire in simplicity.

http://www.audiocircle.com/index.php...a=view;id=1335

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post #85 of 88 Old 07-23-2011, 07:05 PM
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Sure.

Here's an example using a Seas CA18RLY 6.5" mid/bass driver. The measurement is particularly interesting since the sound pressure at the measurement microphone is kept (nearly) constant during the whole frequency range using a minimum phase digital equalizing filter calculated using the Hilbert transform of the raw frequency response.

Now, the first graph show the CA18RLY driven directly by a competently designed SS power amp (=low output impedance).

The second graph ("-S") shows the exact same setup but with a 0.8mH coil in series, and the third graph ("-S2")shows the setup using two 0.8mH coils in series with the CA18RLY.

As you can see, there is a significant reduction in distortion from the driver in in the midrange where the nonlinearities in the motor system inductance is contributing to the distortion significantly (the mass controlled range).

Interesting.

Do you know the R of the coil(s)?
Also are there other similar tests you can link to with different drivers? Or similarly with resistors rather than inductors?

I've read the Pass and Hawksford stuff on high Z sources in the past, but they were much higher source Z from memory but I'll revisit them over the next few days as I have time.

It would also be interesting to see the same test performed on something like the AE TD6M which has <10% of the Le of that Seas.

However, I'm still not seeing anything that would show a significant reduction in power compression this way.

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post #86 of 88 Old 07-24-2011, 01:37 AM
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Originally Posted by A9X-308 View Post

Interesting.

Do you know the R of the coil(s)?
Also are there other similar tests you can link to with different drivers? Or similarly with resistors rather than inductors?

Sorry, No. At least none made wih constat SPL technique (which IMO is a much more relevant measurement than if you allow the SPL to vary).

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However, I'm still not seeing anything that would show a significant reduction in power compression this way.

Well, power compression is (to me) really a "collection" of different compression mechanisms coming into play when leaving the "small signal" range. The three main mechanisms are BL (motor force) compression, Cms (compliance) compression and thermal (Re) compression.

What actually happens in a passive XO is that it gradually transfer the drive mode of the driver from predominantly "voltage control" to predominantly "current control", acting more like a current source than a voltage source. In effect this means that in this range, any distortion due to impedance changes in the driver will be supressed. It dosn't matter if it is position dependant inductance changes (like motor system nonlinearities) or purely resistive changes (like thermally induced power compression). The current drive will help counteract all impedance induced artifacts.

The positive effects on the thermal compression are hard to quantify because you usually have to play for extended periods of time at "high levels" for thermal power compression to set in. Depending on how the driver is used (frequency range, etc.) it could mean that the other power compression mechanisms start to dominate the power compression contribution before thermal compression becomes a problem.

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post #87 of 88 Old 07-24-2011, 04:04 AM
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^^ Short response for now. I don't see how a small variation in source impedance comes anywhere near to being a current source, which is part of the reason I asked about R of the inductors. Using typical commercial values, it is nowhere near a current source in my eyes until it is so great it completely swamps driver impedance.

As it stands as presented, it is an interesting data point on a single driver and ource combination, but so far not convincing me it is all that worthwhile. And definitely not convincing it is universally applicable, especially I think with drivers with excellent Bl/X linearity.

If I had more time and interest, I would be interested to try something like the Elliott adjustable Zout amps and a number of drivers and Zout to test with. Too many projects already, and once the theatre is complete, I'll be moving on to other things, non audio.

Power compression has always been expressed as the loss in SPL for a given heating and Re variation, at least in the pro area where it is more commonly discussed. I'm still not seeing that there will be that much difference with the test results you supplied above, vis a vis simply band limiting to the same extent electronically before the power amp and the same power and time applied to the voice coil.

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post #88 of 88 Old 07-24-2011, 02:53 PM
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^^ Short response for now. I don't see how a small variation in source impedance comes anywhere near to being a current source, which is part of the reason I asked about R of the inductors. Using typical commercial values, it is nowhere near a current source in my eyes until it is so great it completely swamps driver impedance.

As it stands as presented, it is an interesting data point on a single driver and ource combination, but so far not convincing me it is all that worthwhile. And definitely not convincing it is universally applicable, especially I think with drivers with excellent Bl/X linearity.
It's a complex subject with many ifs and buts, and a subject that very fast gets very complicated. But, basically it dosn't have to be an ideal current drive to reap the benefits. The impedance seen by the driver is essentially that of the impedance from the series inductance. Now, any deviation from a pure voltage drive, however, will help supressing the part of the distortion that comes from the motor system inductance nonlinearities (which for most drivers contribute a significant part of the distortion in the mass controlled frequency range of the driver).

In fact, IMO, from a nonlinear distortion perspective it makes little sense to use low impedance driving of a dynamic driver, because the membrane force is dictated by F=Bil -the force is dictated by the position of the coil and the current flowing through the coil, not the voltage over it.

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I'm still not seeing that there will be that much difference with the test results you supplied above, vis a vis simply band limiting to the same extent electronically before the power amp and the same power and time applied to the voice coil.
I don't agree at all . Power compression (thermal compression) is (from a driver perspective) caused by the impedance of the voicecoil changing due to the temperature of the coil. If you drive with voltage, the current through the voicecoil will depend on the coil temperature, where as if using a higher impedance drive, the current through the coil would be less affected by the temperature and thus counteracting the power compression artifacts.

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