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post #1021 of 1044 Old 01-13-2014, 11:42 AM
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Quote:
Originally Posted by Glimmie View Post


Take it form me as I just went through a painful experience with this over the holidays.

DO NOT USE HIGH POWER AMPS ON BIAMPED TWEETERS!

That sucks, but sounds like you need better amps, or preamps... You might also consider buying (or building) a power sequencer to control turn-on and turn-off automatically. Saved our church speakers more than once...

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post #1022 of 1044 Old 01-13-2014, 11:52 AM
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Quote:
Originally Posted by DonH50 View Post

That sucks, but sounds like you need better amps, or preamps... You might also consider buying (or building) a power sequencer to control turn-on and turn-off automatically. Saved our church speakers more than once...

Got all that. I have a DIY power sequencer but I powered cycled the DSP box more than once because it locked up and bang!

Perhaps I am being paranoid now but $1000 later....

It also doesn't help that I am debugging my MiniDSP system at the same time. And as I built my own AES card for the MiniDSP I did have some clocking problems causing clicks. In hindsight I should have bought some $29 tweeters until the reworked HT system is stable.

Oh well!

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post #1023 of 1044 Old 01-13-2014, 12:05 PM
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Ouch! I need to remember this as getting and playing with a miniDSP is on my "to-do" list. Probably have to add an output circuit to prevent glitches.

Probably after I retire.

In about 183 years. tongue.gif

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #1024 of 1044 Old 01-13-2014, 12:21 PM
 
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Originally Posted by DonH50 
200 W to the lows and 200 W to the highs, yes, but neither driver, high or low, ever sees 400 W. To achieve 400 W drive to any driver you need a 400 W amp.

So basically if using a 200W amp to the highs and 200W to the lows, most of the power to the highs will dissipated in the crossover network? So therefore it's not 'seeing' 200W. If that's true, then why would it blow anything as per Glimmies post? Not sure I understand that.
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post #1025 of 1044 Old 01-13-2014, 01:00 PM
 
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What is the power split between a tweeter, and mid and low frequency driver? Would it be conservative to say that the tweeter sees 30% of the available power in a speaker system?
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post #1026 of 1044 Old 01-13-2014, 01:04 PM
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Quote:
Originally Posted by Heinrich S View Post

So basically if using a 200W amp to the highs and 200W to the lows, most of the power to the highs will dissipated in the crossover network? So therefore it's not 'seeing' 200W. If that's true, then why would it blow anything as per Glimmies post? Not sure I understand that.

Yes, much of the power is "blocked" by the crossover, but that doesn't mean you can't still overload your speaker (especially the tweeter) if you are exceeding their power rating. So, in your example, two passively biamped 200W amps will not equall 400W, but if your speaker is rated at only 150W to begin with, then you can certainly blow your tweeter if you push the amp... the crossover won't protect you from sending too much power to the tweeter. But why anyone would bother bi-amping when one amp already exceeds the power rating of a speaker is beyond me. You'd blow your tweeter even if you didn't biamp. However, some still argue that biamping has other benefits even if there is no increase in power (signal separation, less distortion, etc) but most people on this thread strongly disagree.
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post #1027 of 1044 Old 01-13-2014, 01:11 PM
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Quote:
Originally Posted by Glimmie View Post

Take it form me as I just went through a painful experience with this over the holidays.

DO NOT USE HIGH POWER AMPS ON BIAMPED TWEETERS!

What speakers are you using? Their power rating?
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post #1028 of 1044 Old 01-13-2014, 01:27 PM
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Quote:
Originally Posted by Heinrich S View Post

What is the power split between a tweeter, and mid and low frequency driver? Would it be conservative to say that the tweeter sees 30% of the available power in a speaker system?

It depends greatly upon the crossover point(s) of the driver(s) and source material. Look up Fletcher-Munson loudness contours (or curves) in Wikipedia or someplace to get an idea how we hear over frequency. Bear in mind that 10 dB in the midrange sounds about twice as loud but takes ten times the power.

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post #1029 of 1044 Old 01-13-2014, 02:05 PM
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Originally Posted by stereoforsale View Post

What speakers are you using? Their power rating?

Origional set:
ScanSpeak D2905/9500

First replacement:
ScanSpeak D2905/9700

Current set:
Morel ET338-104

The power handling specified is rather high, like 60W with 200w peaks. But I don't know how they determine that. It surely isn't true RMS. I tried to repair one and re-solder the voice coil where it melted, right at the bond to the wire leading to the terminal. The wire is like silk thread. There is no way that is going to take 60w RMS for more than a few hundred milliseconds at a time. In doing some subsequent research I have read many others have the same conclusion.

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post #1030 of 1044 Old 01-14-2014, 08:20 PM
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Quote:
Originally Posted by Heinrich S View Post

So basically if using a 200W amp to the highs and 200W to the lows, most of the power to the highs will dissipated in the crossover network? So therefore it's not 'seeing' 200W. If that's true, then why would it blow anything as per Glimmies post? Not sure I understand that.

No, it's not dissipated in the crossover. That power of which you speak is never created because of the crossover's high impedance to the out of band frequencies where that power is contained.

Just because there is a knob doesn't mean you should turn it.
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post #1031 of 1044 Old 01-14-2014, 08:31 PM
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Quote:
Originally Posted by Glimmie View Post

Take it form me as I just went through a painful experience with this over the holidays.

DO NOT USE HIGH POWER AMPS ON BIAMPED TWEETERS!

I put a four channel QSC theater amp with 170w RMS per channel on my LCR tweeters. Hey, they only need a few watts but I have this nice compact amp sitting around that cosmetically matches the other power amps I am using. Now TWO sets of new tweeters later I am using some rebuilt old Hafler SE120s at 60w per channel. And even that's too much so I am looking at some 20w class A designs long term.

The problem is that all it takes is a digital error (click) or two or an improper turnoff sequence where there's a thump and your tweeters are gone. Fuses are useless. After the origional tweeters went out I put 1.5amp fast blow fuses on the new tweeters. Well those new $200 ScanSpeak tweeters did a great job protecting those expensive fuses!

Another trick I am also using now is to have a 33uf capacitor in series with the tweeters. This rolls off the low end to about -3db @ 700hz. This is far enough from the 1800hz crossover point not to cause significant phase shift. But it will offer some protection against low frequencies getting to the tweeters. Yes, the active crossover does this too but consider a turn on or off thump or some other anomaly on the tweeter amp. The active crossover won't protect against that.

Before all this nonsense I was using 10 watt tube amps on the tweeters and never had an issue in 10 years of biamping. I guess the cost of re-tubing every year was not that much after all! rolleyes.gif

Sure...but your problem is with real biamping. With passive biamping, the sort that's the main topic of this thread, it's a whole different story.

Just because there is a knob doesn't mean you should turn it.
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post #1032 of 1044 Old 01-15-2014, 11:26 AM
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Originally Posted by whoaru99 View Post

Sure...but your problem is with real biamping. With passive biamping, the sort that's the main topic of this thread, it's a whole different story.

Yes, that's correct. I just want to warn people that when you remove the crossover or otherwise tie a larger power amp directly to a tweeter you really need to be careful. I have come to the conclusion that tweeter specs most likely assume a passive crossover will be used.

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post #1033 of 1044 Old 03-28-2014, 12:41 AM
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I wish I would have read this thread before the big mistake I just made! I am hoping someone here can help me. Despite loving how my system sounded already, I just bi-amped my Boston VR3's to my Onkyo SR-707. It appears from reading this thread I would have heard no difference is sound quality even if I had wired everything correctly - which I did not. I read about bi-amping earlier today and despite reading about removing the jumper bars before bi-amping, in my excitement to hear the so-called improvement in clarity I forgot to remove them. So while I was giving them my first test listen I switched to "bi-amp" mode on the receiver and noticed an immediate drop in volume but a noticeable increase in sound clarity vs the normal mode. So I turned the volume up a bit and noticed that every time the bass hit the lights in the room were dimming. I knew something was wrong at that point but I didn't know what it was, so I paused for a minute to try to think of how to correct the problem. As I was thinking the receiver's protection mechanism kicked in and shut off the receiver. This startled me a bit, but I figured that there probably wasn't any real damage done. I then realized I hadn't followed the clearly stated directions, I removed the jumper bars. I powered everything back to find that my left speaker now was quieter and had far less high frequency response. Now I must say I don't know what exactly it sounds like when a speaker is blown, but I don't think that is what happened because the left speaker doesn't distort (at least in a traditional sense), it just sounds different (muddier, lower volume and much less tweeter brightness). Does anyone know what I did or how to fix it? Are there any electronics in the speaker that  protect it from blowing but may not be able to prevent the tone from being permanently damaged? Any response would be appreciated. I am rightfully really beating myself up for being so stupid. I am just hoping that I don't have to ship the whole tower to Boston because it is difficult to explain what the issue is without hearing it next to a properly functioning VR3 next to it. At this point I'm just hoping that there is a crossover or some type of protection mechanism in the speaker that will save me from having to buy a whole new speaker, especially since they don't even make VR3's anymore. Anyway I will stop rambling and hope that someone can help. Thanks in advance for any direction you can give me! 

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post #1034 of 1044 Old 03-28-2014, 05:30 AM
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Swap loudspeakers. if the problem moves with the loudspeaker it's the loudspeaker. If not it is the amplifier.

By not removing the jumpers you tied the amplifier outputs together. This can cause damage to the amplifier.
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post #1035 of 1044 Old 03-28-2014, 06:29 AM
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Quote:
Originally Posted by Glimmie View Post

Yes, that's correct. I just want to warn people that when you remove the crossover or otherwise tie a larger power amp directly to a tweeter you really need to be careful. I have come to the conclusion that tweeter specs most likely assume a passive crossover will be used.

Yes, one must be careful but if one is it's perfectly alright to actively biamp with miniDSPs which I do. I've blown a tweeter but just once over several years and that was by error on my part. It was a $200 Scanspeak tweeter.
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post #1036 of 1044 Old 03-28-2014, 08:26 AM
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Thank you Frank Derks. I will try that as soon as I get home. I kind of hope it's the receiver as I think I can replace it with something similar for less money or at least with less hassle. Thanks again. 

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post #1037 of 1044 Old 03-30-2014, 06:28 AM
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This thread had 1,000 posts in its initial 3 months.
Sorta answered the bi-amping Q and consensus is:
-waste of time if using passive crossover
-worthwhile if using active crossover

Should be made a sticky for future easy reference


Via Mikes brain/thumb interface, LLAP
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post #1038 of 1044 Old 03-30-2014, 08:48 AM
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I don't think it makes sense to recommend active biamplification to home audio users unless they know what they are doing and the people asking the question in this forum don't know what they are doing. I think most amateurs would be likely to make things worse rather than better. The best advice to a home audio user is to stay completely away from it.
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post #1039 of 1044 Old 04-02-2014, 01:50 PM
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Quote:
Originally Posted by FMW View Post

I don't think it makes sense to recommend active biamplification to home audio users unless they know what they are doing and the people asking the question in this forum don't know what they are doing. I think most amateurs would be likely to make things worse rather than better. The best advice to a home audio user is to stay completely away from it.

agreed!

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post #1040 of 1044 Old 05-03-2014, 02:36 PM
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If you don't mind, help me confirm I have this right:

take, for instance, a pair Monitor Audio RS6 towers.
(Frequency range: 38Hz–30kHz. Sensitivity: 91dB/W/m. Nominal impedance: 6 ohms. Power handling: 120W RMS)

and two Adcom 555 II amps.
(where each amp is rated at 200 watts per channel into 8 Ω from 20 - 20,000 Hz at less than 0.04% THD, both channels driven, yet some have said its conservatively rated and truly outputs upwards of 270x2)

Scenario A: using one amp only
Questions:
* In this scenario, given the 6ohm speakers and their 120w RMS power handling spec, is it too much amp for these speakers in a harmful way (might blow the speakers), or in a wasteful way (wasting electricity, generating unneessary heat, not using the amps true capabilities), or is it not "too much amp" at all and is somehow a beneficial pairing? My thinking at this time is that it's a "wasteful" pairing but largely harmless.
* Further, how much is this amp really putting out to 6ohm speakers?

Scenario B: using two identical amps in a passive bi-amp setup
Questions:
* In this scenario, given my hypothesis that even one of these amps is basically just more amp than necessary to drive such speakers, and as such even one of these amps isn't being fully utilized, is it correct to say that running two of these amps in a passive bi-amp way is even more wasteful or unnecessary (at best) and potentially harmful to the speakers even more so than running one amp only?
* Also, is it the general consensus (amongst objectivists) that running two of these amps into these speakers in a passive bi-amp mode is most likely to garner no appreciable difference in sound quality or volume if a real series of double blind tests were performed?
* And lastly, is there any tangible benefit to bi-amping these amps to these speakers at all, beyond perceived "cool-factor" notions? Such as, and this is a stretch, perhaps using two amps but not driving them hard somehow extends the lifespan of said amps, or some such?

Thanks, and I know these questions cover more than passive bi-amping, but I'm trying to make sure I am grasping the current state of opinions (and/or facts) on such matters.

Admittedly, I'm having to shake off a lot of misperceptions and old knowledge as I wrestle with my own subjective vs objective tendencies, and come to terms with the fact that most of what people said about such things over the years was wrong, and places like this have done wonders to dispell various myths and the like.
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post #1041 of 1044 Old 05-03-2014, 03:08 PM
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LoS.

A1: Speakers are not like fuses where they blow when you exceed their rating. Power ahndling is a rating that takes some time too exceed. At normal levels most of the time you'll only be supplying a couple of watts to a speaker, so any high powered amp is 'wasted', but if you have too much you can turn it down, but if you have too little, you can't turn it up. Don't give further thought to it.
A2: Dunno. Google. However even if they do put out 270W that is only 1.3dB above 200W.

B1: Unnecessary, but not harmful.
B2: No appreciable difference
B3: No benefit at all. I don't see how using two amps to do the job of one makes it 'cool' in any way.
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post #1042 of 1044 Old 05-03-2014, 05:37 PM
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Quote:
Originally Posted by A9X-308 View Post

... I don't see how using two amps to do the job of one makes it 'cool' in any way.
But it will get warm with two heat sources. wink.gifbiggrin.gif
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post #1043 of 1044 Old 05-04-2014, 02:26 AM
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But it will get warm with two heat sources. wink.gifbiggrin.gif
OK. Passive biamping my have the benefit in some environments of increasing the temperature in the listening room by adding inefficient space heating.
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post #1044 of 1044 Old 05-04-2014, 07:33 AM
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Quote:
Originally Posted by LoverOfSongs View Post

If you don't mind, help me confirm I have this right:

take, for instance, a pair Monitor Audio RS6 towers.
(Frequency range: 38Hz–30kHz. Sensitivity: 91dB/W/m. Nominal impedance: 6 ohms. Power handling: 120W RMS)

and two Adcom 555 II amps.
(where each amp is rated at 200 watts per channel into 8 Ω from 20 - 20,000 Hz at less than 0.04% THD, both channels driven, yet some have said its conservatively rated and truly outputs upwards of 270x2)

Scenario A: using one amp only
Questions:
* In this scenario, given the 6ohm speakers and their 120w RMS power handling spec, is it too much amp for these speakers in a harmful way (might blow the speakers), or in a wasteful way (wasting electricity, generating unneessary heat, not using the amps true capabilities), or is it not "too much amp" at all and is somehow a beneficial pairing? My thinking at this time is that it's a "wasteful" pairing but largely harmless.
* Further, how much is this amp really putting out to 6ohm speakers?.

how much power an amp puts out depends on the volume control setting and the content being played. No amp puts out full power all the time. When it is silent between songs, the amp should put out zero power, for example. And a whisper at 70 dB requires only one percent of the power needed to play back a semiloud sound effect at 90 dB. theoretically at "reference level" at the highest possible level for digital media (called 0 dBFS - full scale) each speaker would be at 105 dB, requiring almost forty times the power needed for the semiloud 90 dB effect. If the 70 dB whisper (that's a bit louder than normal conversation levels, btw) requires a tenth of a watt, the 90 dB sound would require 10 watts and the 105 dB sound almost 400 watts. While those peaks may be very brief and might not destroy your speakers even at 300 or 400 watts, the speakers themselves likely stop responding linearly (that is they don't get as much louder as the incoming signal calls for and distort more) somewhere around half their (thermal) power rating . . . so even with the huge power, assuming we had it, the Monitors (not to mention my little Paradigm Studio 10s will actually never fully reproduce the all out assault of a loud explosion at reference. Luckily for me, my listening habits are more conservative, seldom reaching 15 dB below reference, so in my example my peaks at 90 dB would require 10 whole watts. And that's all an amp will deliver, whether it's capability is 40 watts or 500 watts . . . .

Moreover, amp power is not something that just cuts off. Amps are rated to supply a specific power into a stated load at a specific level of distortion. Keep turning up and the amp will make more power at higher distortion. Absent competent testing, it's not really possible to precisely know what an amp will do into an untested/unspecified impedance. If you have both an 8 ohm rating and a 4 ohm rating you can rest assured the 6 ohm power will be between those two numbers. Otherwise it's safe to assume it's a bit more than the 8ohm rating.
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