Bi-Amping and a sub

[PlanetErik]

Excerpted from the website referenced by EW purporting to proclaim the superiority of active crossovers vs passive:

"Equally important is the selection of the electronic crossover frequency. It must be the same as the original, within a few 10s of hertz. The only exception is where you might obtain information from the manufacturer of the speaker that allows the frequency to be modified. In general, I strongly suggest that you determine the original crossover frequency, and stay with it."

This is the key caveat: How do you obtain this information accurately? Plus, how do you bypass the internal crossover network of just about every home audio loudspeaker to begin with in order to use an external active system? It seems to me that electronic crossovers might be ideal for professional live sound systems or custom home speakers without internal passive crossover networks, but totally impractical to implement on conventional hi-fi loudspeakers.

And indeed, I daresay that the crossover network implementation of a given speaker is the "soul" of that speaker, and represents a rather complex interaction among drivers, cabinet, crossover frequencies, filter slope characteristics, impedance characteristics, etc, etc. You bypass that and you've completely subverted the personality of the speaker, and most likely not for the better.

 

[EchoWars]

How do you obtain this information accurately?

We don't need to...on the front of the crossover is a little dial. Said dial changes the frequency of the crossover point. Simply adjust to what sounds best. However, you certainly can find the impedence/response curve of any speaker and use that information as a starting point.
(edit: On second thought...in order to properly realize the benefits of a biamped system, you do really need to determine the speaker parameters. By all means you can experiment as I suggested to see what sounds best, and that's part of the 'geekyness' and cool-factor of a active system...being able to tweak the system to your own satisfaction. But if you want to emulate the manufacturers response, you will indeed need accurate information, which as I state below, can be determined expermentally)

Plus, how do you bypass the internal crossover network of just about every home audio loudspeaker to begin with in order to use an external active system?

Who was suggesting to bypass anything? On anybody's speaker, must less "every home audio loudspeaker"? I must have missed something.

It seems to me that electronic crossovers might be ideal for professional live sound systems or custom home speakers without internal passive crossover networks, but totally impractical to implement on conventional hi-fi loudspeakers.

Matter of opinion, and perhaps true to some degree. I never once suggested that anyone rip into their speakers and start pulling out crossovers...but if you wanted I could come up with a long list of speakers that would benefit from this.

And indeed, I daresay that the crossover network implementation of a given speaker is the "soul" of that speaker, and represents a rather complex interaction among drivers, cabinet, crossover frequencies, filter slope characteristics, impedance characteristics, etc, etc. You bypass that and you've completely subverted the personality of the speaker, and most likely not for the better.

Italics mine. Unless you have some high-dollar speakers, chances are that the crossover is the weak point. Stuck inside the box...where noone will ever see it, cheap parts such as iron-core inductors and electrolytic capacitors destroy the ability of a speaker to sound it's best. And even when quality parts are used, a passive crossover is always a compromise.

RE: Why mainly used in pro sound systems? Lance Dickason: "Because it (an active crossover) is more complex and expensive than single amplifier/passive crossover systems, it has never been popular in commercial home stereos. It's attributes and benefits, however, make it's use extremely attractive."

You want facts? Not BS opinions, facts from those who have spent their lives dedicated to the study of crossover/speaker/amplifier interaction. Pack a lunch dude..

Advantages of Active Crossover Implimentation

1) Lower IM distortion due to amplifier operation over a more narrow bandwidth, and reduced clipping caused by low frequency overload due to driving only one speaker in a multi-driver system.
(R. Small, 'Crossover Networks and Modulation Distortion", Journal of the Audio Engineering Society (JAES), January 1971)

2) Increased dynamic range. One 60W and one 30W amp in a biamp setup will clip at about the same level as one 175W amplifier with a passive crossover.
(Lovda and Muchow, "Bi-amplification - Power vs. Program Material", Audio, Sepetember, 1975)

3) Improved transient response.
(A.P. Smith, "Electronic Crossover Networks and Their Contribution to Improved Loudspeaker Transient Response", JAES, September, 1971)

4) Better amplifier/speaker coupling for woofers, and avoidance of passive crossover induced tweeter resonances.

5) Better crossover performance working into a constant impedence level (no reference needed...if you know Ohms Law, and have ever looked at the impedence curve of any speaker, this one explains itself)

6) Better subjective sound quality than high-level (passive) networks.
(D.C. Read, "Using a Single Bass Speaker in a Stereo System", Wireless World, November 1974

7) Easier control over driver sensitivity differences. One potentiometer for gain control takes the place of inefficient and often poorly chosen power resistors in the passive network.

8) Easier manipulation of phase, time delay, resonance, and various kinds of shaping, contouring, and equalization.
(S. Linkwitz, " Active Crossover Networks for Noncoincident Drivers", JAES, Jan/Feb 1976; "Passive Crossover Networks for Noncoincident Drivers", JAES, March 1978)

The last two papers are huge. I have those JAES issues (somewhere....), please note the name of the author...the very man who virtually wrote the book on passive crossover design goes on in more detail than most care to examine why passive crossovers are and always will be a compromise inferior to an active network. Regarding the rest, I have read most of them at one time or another.

Now...I am NOT suggesting that ANYONE rip their speakers apart, yank out the network, and replace with an active setup. On high-dollar speakers it would be pure folly. On cheap speakers, it's a waste of time. Secondly, to biamp properly requires intimate knowledge of the drivers and their characteristics. All of these characteristics can be determined experimentally, and if one was so inclined, nearly any speaker could be reverse-engineered and improved by the addition of a active network. It is absolutely not a project for the uninitiated or the clueless.

RE: The original speakers in question, the B&W 604's. I have been led to believe that these were designed with the ablility to biamp in mind. A simple email to B&W will probably result in an answer as to the best crossover frequency suggestion...if they are indeed biamp ready.

 

[PlanetErik]

EW Quote: "Now...I am NOT suggesting that ANYONE rip their speakers apart, yank out the network, and replace with an active setup. On high-dollar speakers it would be pure folly. On cheap speakers, it's a waste of time. Secondly, to biamp properly requires intimate knowledge of the drivers and their characteristics. All of these characteristics can be determined experimentally, and if one was so inclined, nearly any speaker could be reverse-engineered and improved by the addition of a active network. It is absolutely not a project for the uninitiated or the clueless."
___________________________________________________

Exactly, that was my point. It is almost always impractical. My original reply was prompted by your rather needlessly heavy-handed response when Fred suggested that perhaps it would be better to leave well enough alone, or as you later said that "on high-dollar speakers it would be pure folly".

No need to get your t___ts in an uproar. I figure that the loudspeakers in question have pretty decent passive crossovers and the additional complexity of incorporating an active network would very likely not be worth the trouble.

Incidently, even active filters use those so-called crappy parts such as inductors and electrolytic capacitors. How else can you create a frequency-selective circuit? Op-amps and/or transistors alone won't filter by themselves. And, undoubtedly many published papers can be cited detailing the less-than-desirable audio characteristics of op-amps.

My advice? KISS - keep it simple stup..., err sir.

 

[EchoWars]

Incidently, even active filters use those so-called crappy parts such as inductors and electrolytic capacitors. How else can you create a frequency-selective circuit?

In an active circuit, no inductors. And electrolytics are necessary only in the power supply...not in the signal path. You're out of your league here...

And, undoubtedly many published papers can be cited detailing the less-than-desirable audio characteristics of op-amps.

What you will find are a slew of biased opinions 'published' all over the web, and in audio magazines....arguments from fools who tout the benefits of $500 AC cables and drawing on CD's with green felt-tip pens. I challenge you to locate one paper in a respected scientific journal pointing out the shortcomings of a properly implemented opamp design. Just one... Facts, not opinions. And whatever supposed 'shortcomings' exist in opamps, they pale by comparison to those found in passive filters.

No need to get your t___ts in an uproar.

No uproar here. I'm simply pointing out that you are obviously uninformed and uneducated in these matters. If you want to debate a topic, you'd better understand it first.

I figure that the loudspeakers in question have pretty decent passive crossovers and the additional complexity of incorporating an active network would very likely not be worth the trouble.

Perhaps not, but part of the fun of the audio hobby is experimenting with new things...else we'd all be listening to Bose Wave radios and calling it Hi-Fi.

My advice? KISS - keep it simple stup..., err sir.

Well, now that we've stooped to ad-homm attacks, I can assume that you've run out of constructive and intellegent things to say. If you wanted to discuss the pro's and con's of the matter in a more-or-less constructive manner, I'd be willing to do so. But I'm not really willing to participate in a banter of name calling and ad-homms. They have no place on this board.

 

[RobV]

Originally posted by EchoWars
...part of the fun of the audio hobby is experimenting with new things...

I couldn't agree with you more. I think we all agree that messing with speakers like B/F's superbly engineered Ren 90s would be crazy. However, I haven't found the 'holy grail' of loudspeakers like Fred has.

My stereo speakers are my own creation, and have evolved over the last two years. They started life as BIC dv62si bookshelf speakers.... first I upgraded the (coil & cap) crossovers and added extra damping.... a few months later, new tweeters.

I decided to add an active crossover after reading Rod Elliott's article and many others like it that explained the numerous advantages. (oh yeah, that second Sansui BA-F1 amp that was not being used had something to do with it. At the time I also upgraded the woofer and reinforced the cabinet with a brace and gross amounts of epoxy inside it. Banana plug bi-amp terminals are easy to add.

All quality raw speaker manufacturers provide graphs that detail frequency response, impedence curves, dispersion and efficiency. It's not hard to match drivers with the information they provide.

I really like how they sound, but I've got my eye on a few ribbon tweeters... :scratch2:

Many of us do like to tinker with our system, always trying something new.... It's a hobby.

RobV

 

[PlanetErik]

Really, no uproar here?

We were talking about an existing commercial hi-fi louspeaker intended for use in the home. I am certainly not discouraging experimentation or audio hobby fun. My claim was that active crossovers were overkill for this particular situation.

You really sound like a fun-loving guy, EW. Please, spare me the righteous indignation because I tweaked you rather gently with the KISS remark. No one is calling you any names. On the other hand, your assertions about my being uneducated and uninformed, and suggestions that I am not worthy of engaging you in discussion are pretty ludicrous, if not downright insulting. You know nothing about my level of education, or my professional background, or anything about me for that matter. Your comments about "arguments from fools" reveal your arrogance.

Apparently you're the final authority on audio, and everyone else is just a biased fool. So there are no shortcomings to a properly implemented opamp design? It's just the ideal component like the textbooks say, and its audio performance is beyond reproach, isn't that right EW? How dare anyone suggest otherwise. Now if we could only have an op-amp loudspeaker and get rid of that crappy loudspeaker inductance and capacitance. That would undoubtedly be audio nirvana.

Pardon my sarcasm EW, but you're pretty thin-skinned for guy who thinks nothing of riding rough-shod over other people's opinions.

 

[EchoWars]

LOL!! No thin-skin here. Take all the pot-shots you like...it'll only amuse me and cause this thread to be locked.

My comment about being uninformed and uneducated in these matters is not intended as a personal insult. The fact that you do not seem to be familiar with the topology of an active filter lead me to believe this. Either you know, or you don't. Apparently you don't or you wouldn't have posted the comment about inductors and electrolytics in active filters. And I can only guess about your level of education...you may have a PH.D in english, but your education is apparently not in electronics engineering.

There are shitty opamps and very very good opamps. All have their pluses and minuses. The best ones indeed approach being near-ideal devices, and are capable of a sound quality that easily rivals any discrete design.

There are electronics/audio subjects that I know very well...and others of which I know little. Active and passive filtering and their interactions with motor design happen to be subjects that I have studied in some detail. So I will allow myself a bit of 'arrogance' here. On many other electronics subjects I will simply bow to those with more education and experiance (and the list of these subjects is long).

As to my being a 'fun' guy, well...you probably won't find my phone number written on the walls on many women's restrooms, but I have my moments. :

By no stretch of the imagination did I intend to insult you (but I'll take pot-shots at the $500 power cable guys and green felt tip morons all day long...). But it seems to have turned out that way, so I'll end by apologising for my inadvertent indiscretions and urge you to track down a few of the JAES articles I referenced in my earlier posts, or research the subject a bit on the web.

Since we have all apparently had our say, this thread has been throughly trashed, and ruffled feathers abound...I'd say we're done here.

 

[fliphandywork]

PlanetErik... PLEASE READ>

Way to ruin a great thread... JUNIOR. Go somewhere else or learn your place. Thanks JUNIOR.

BaH BYe

 

[PlanetErik]

EchoWars, you're absolutely right - 'nuff said, and a tip of my cap to you.

Flip, I read your condescending message. It came through loud and clear. I will honor your "dismissal".

Oh, and one more thing Flip, a flip of something else to you (use your imagination) as a farewell gesture.

Buh bye,
"Junior"

 

[fliphandywork]

You will be missed...

 

[BeatleFred]

Unfortunately, I must say that I disapprove of many comments Ive read in this entire thread. I think its time for me to set things straight here by doing some -> where are you, Flip?

Flip, allow me to remind you that I am the Moderator of this forum, so its not YOUR place to dismiss anyone here. (as you did with PE).
Do you understand that? If he said or did anything to merit expulsion from the 'E.S.' Message Board, then I shall be the one make that determination. Please keep it in mind for future reference. I hope that we're now clear on this point.

As for your hi fi setup, I looked over your original post again in the other thread regarding the BA-5000, as well as re-reading thru the (mostly) unnecessary technical banter in the previous messages of this thread. Here are the thoughts I now offer to you and that will be all I have to say in this matter, the rest is up to you to do whatever you want:

There should be no confusion about whether your speakers are biamp-capable, as E.W. seemed to be unsure about. Its not clear to me why EW would state the speakers are at risk to be damaged if you were to biamp them. Its quite simple- look at the photo I provided at the bottom of this message. If your speakers have TWO sets of terminals in the back like these do, then THEY CAN be biamped. Otherwise, what are they for? for crying out loud.

Perhaps EW's confusion stems from the fact that a simple step in the biamping process was not previously mentioned that I assumed was already known. And that is, when you biamp your speakers, you MUST first remove the shorting straps on the back of the speaker terminals (which separates the bass and midrange/tweeter sections of the crossover when the straps are removed). If you forget and then biamp, then its a case of I imagine your B&W's have shorting straps similar to my Infinity Renaissance 90's which are gold-plated straps that you might be able to make out in the photo below (the photo is not of the actual speaker I own, my Ren 90's have a blonde oak cabinet).

I already provided some information to you (or anyone else interested)that can be read Online so I suggest you keep reading and keep learning and ultimately decide for yourself what you think is best to hook up your audio system. I merely pointed out a way that you could biamp your system without complexity by using a 2nd 9090DB and a preamp with two pairs of output terminals- if you were so inclined to acquire another 9090DB and preamp, that is. And an external crossover is NOT a requirement in this arrangement! However, as I also stated early on, since EW is working on your 9090DB, and everyone else here has been quite pleased with the results of his work when they've sent their equipment to him, then its quite likely you will be content when you get the receiver back from him and find that there's really no need to get another 9090DB, let alone a huge BA-5000, or biamp anything for that matter- especially if the B&W speakers you have are quite reputable and you also have a subwoofer. So, what is it then that you feel the need to accomplish and why does the thread have to go into unnecessary theoretical discussions on active filters, crossovers, etc...??

If there are any questions about the capabilities/limitations of your speaker model, I suggest looking thru the Owners/Operating manual (which I presume you do own) because the appropriate information should be in there. If you feel you need more Info, simply contact B&W (or Martin Logan), explain to them the equipment you have, what you propose to do, and see what their response is. Do you think B&W would say that the X-over in their speaker is not good enough and that you must use an external x-over to perform biamplification?, I doubt it. Have you gone to the site www.audioreview.com and read the comments written there by other B&W speaker Owners in the Reviews section? I dont have the time now to read all the posted messages, but I did see the DM 603 S3 and DM 604 S3 listed on A.R. (yours is a 603 S4, you say?) - well then, read the owner comments and see if they biamp their system, I'm sure you can pick up alot of useful info there. Dont you think another actual B&W speaker owner could advise you better than we can here at A.K. if you were to contact him and ask?

Also - You mentioned that you already biwire your system with Audioquest cables. Ok- SO--- what were the results? Did you notice any significant difference in terms of improved sound quality when you biwired? Perhaps the result of that might provide something for us to go on in terms of whether biamping would then yield any further improvements.

As for your subwoofer- if you couldve provided a photo of the back of it for us, it wouldve been helpful, rather than my having to search Online for it to help you out with your questions. Doesnt the Martin Logan subwoofer manual have any digrams that explain how to hook it up?

Depending on what connections the subwoofer has, you have various ways of hooking it up to the rest of your system. Doesnt the M.L. manual depict cables running from an amplifier/receiver's L & R channel speaker terminals to the subwoofer's L & R speaker terminals , which in turn conect to the L & R terminals of your main speakers? (which would be your B & W's). So...... I already did give you the hookup method for vertical biamping. Simply make a digram on a piece of paper of those instructions-the diagram will then make it much easier to visualize the setup. Do you see how one amp drives the left speaker and one amp drives the right? Well, you can designate either the amp's left or right channel to connect to the B & W's Low terminals. Pick either one and then be consistent with it thereafter. I think I chose Left to go to the Low when I wrote the instructions. So, just take one 9090DB in power amp mode and connect its Left + and - terminals to the subwoofer's Left + and - speaker terminal. Then take the 2nd 9090DB and connect its Left + and - terminals to the subwoofers's Right + and - terminals. Now run another set of cables (hopefully thin enough to fit) from the subwoofer's Left & Right terminals, to the L & R Woofer terminals respectively on the B & W speakers. Now you have the subwoofer connected in the path to work simultaneously with both B& W speakers. As for the Tweeter sections in both B & W's - obviously you are not connecting the subwoofer in there. So, you just complete the hookup by taking the Right + and - on both of the 9090DB's and send them to the Tweeter terminals on each B & W speaker- 9090DB #1 to Left B & W and 9090DB #2 to Right B & W. And there you have it If thats still not good enough for ya, then knock yerself out further and acquire a 2nd subwoofer and run one subwoofer thru the B&W left spkr and and the other sunwoofer to the B&W right. These are some of your choices and and at this point, I feel I have expended enough energy to explain the matter. Quite honestly, I think you should just wait to get the receiver back from EW and try it out, it should be more than sufficient w/o you having to delve into more amps, biamping etc..

As for any Engineering matters- all I can say is I am interested in obtaining Vol 32, # 6, June 1984 JAES in order to read "Balanced Bridge Amplifier" by Sansui Engineers S. Takahishi & S. Tanaka. If you come across it EW, let me know.

Sincerely,

B/F

 

[BeatleFred]

Ps- During the course of writing the above message, I was distracted by a phone call and I overlooked a typo. RE: the photo & shorting straps. Since the photo depicts the speaker being biamped, then as I mentioned, the strap plate that ties the two sections together is removed. Thus, you WONT see it in the photo.

B/F

 

[fliphandywork]

Understood my friends. Thanks!