Does impedance of a speaker change when one bi-amps?

@rickytickytwo  

Yes for speakers with complex impedance dips and peaks there can be a significant change when you biamp. We dont care about the peaks, its the dips that bother the amplifier. Drivers themselves do not dip below their DC resistance. However when combined with inductors and capacitors this is no longer true (unless its 1st order). 

When you separate the high and low crossovers (unstrap them) the impedance of each will improve because it no longer sees the other. 

@erik_squires 

Hi, Ive been reading your blog. Do you really feel this way about stereophile.  Hearing aids? Trick? What is the "stereophile curve
"?

  For a long time I've had trouble matching up Stereophile reviews with my experience of the same speakers. I think I've found the reason why. They aren't reviewing speakers at all. They are reviewing hearing aids pretending to be speakers. This is why they are so expensive. What I mean is that the speakers Stereophile praises would only sound good to some one with hearing loss between 7kHz and 15 kHz, which I lack. It's clear that completely different manufacturers have taken advantage of this "trick."

I'm calling this trick the "Stereophile Curve" and the more I go back in time to look at megabucks speakers rated highly, the more apparent the truth of this curve becomes. Of course, the alternate, benign explanation is that the reviewers have all bought the B&W studio heritage hype, and they have become accustomed to thinking of the B&W 800 series speakers as a neutral reference, which, objectively, they can't be.

@pkvintage

 I have bi amped several systems and never heard a difference that would justify the additional amp. Bi wire, same thing. I did hear a difference with an active 3 way system with an external crossover though. It was a Linn isobarik Brik system. I also copied the the Linn system with 3 Bryston LP2's and a Behringer 3 way analogue crossover. It was awsome. And cool to talk about. :)

Kudos for going the extra mile.I have been promoting multiamping here for years. I designed the Beveridge RM3 crossover which allows easy  changes and has level controls for both outputs. It is all discrete analog. 

 Most here haven't the nerve to so what we have done so they just bad mouth what we are doing. They dont understand the advantage of removing the un-wanted signal Before the amplifier rather than after. They would rather waste their money on expensive crossover components for a less than optimum solution. 

Someting to think about. If the bass voltage is still present in the treble amplifier then the IM it creates is going to be the same. 

Keep at it man, I will support you.

@erik_squires 

bdp24 said..  Beside the advantage of a bi-amped speaker presenting an impedance of less variation to each of the two power amps than one amp sees from a non-bi-amped speaker

This is what I think he is saying. 

The advantage of a bi-amped speaker is that is presents an impedance of less variation to the individual power amps than what one amplifier has to deal with when the high and low drivers are strapped together. 

I think this is easy to confirm. Just think of capacitors and inductors hooked together vs them not. 

I dont see why you say this statement is not true. Seems true to me. I believe bdp is saying that the high and low terminals driven together are a much more difficult load than the high and low terminals strapped together. 

Really the only one’s who should engage in this are those who have speakers specifically designed with active crossover in mind (pro speakers), or who can build their own speakers anyway.

Everyone else is probably going to do it wrong and is far better off with a single amp solution

.
Well they have my permission and I am willing to help. Ye of little faith. 

Is it soooooooo hard to buy a woofer and a tweeter, divide the signal before the amps, choose appropriate amps. 

As far as I am concerned, speaker level crossovers where an ok solution when one had only one amplifier. Now we have lots of ampifiers. A 6,12,18 db/octave analog crossover is childs play. 

bDP24 says  (this is true)

Beside the advantage of a bi-amped speaker presenting an impedance of less variation to each of the two power amps than one amp sees from a non-bi-amped speaker

@erik_squires  says

Sorry @BDP24 this is not really true as you put it. See from my blog post and any simulation, the min to max impedance is MUCH greater with a split crossover.

The overall current load however is always decreased. This may help the power supplies stiffen up.

While active bi-amping is good, it’s also complicated. It’s much easier to get top of the line parts and design in a passive. 

Sorry, erik. BDP24 is correct. Individual drivers have rather smooth impedance curves because they are mass loaded drivers and thats what mass loaded drivers do.. The wild impedance variations we see in complete speakers are due entirely to the passive crossover which we want to eliminate. 

The complication is not a large one and the benefit is enormous.  Any serious audiophile needs to give it a try and we are here to help at www.berkeleyhifischool.com

@bdp24 

Being able to get rid of the speaker-level crossover parts is one of the two reasons for bi-amping (doing so has at least the potential for producing a worthwhile improvement in the sound quality of a loudspeaker). The other is, as Roger Modjeski said above, to separate the low frequencies from the mids/highs in the amplification (giving each it’s own amp, of course), thereby decreasing the potential for the creation of IM distortion in the amp(s).

Bi-amping need not be complicated and difficult. And, it can be cheaper than replacing stock speaker-level x/o parts with those pricey boutique ones. Not only that, you can use a brute-force amp on the woofers if you want, with a nice tube amp for the mids and highs. I first bi-amped with a pair of Magneplanar Tympani T-I loudspeakers in 1973, using the ARC passive x/o designed specifically for that task. Nelson Pass makes a great electronic x/o, but it’s not cheap. Fortunately he also makes (or made, it has just been discontinued) a modestly-priced 2-way x/o, the First Watt B4. It provides 1st/2nd/3rd/and 4th order filters in 25Hz increments from 25Hz to 3200Hz. All discrete (no opamps, no ic’s), retail price $1500. Reno Hi-Fi may have one left, I don’t know. For DIY’ers, it will soon be available as a kit

.

Thank you bdp. I am in total agreement. We may have to do some education on this. There are many crossovers out there. My Beveridge RM-3 shows up now and then for a few hundred dollars.

I have recently made some 2nd and 4th order Linkwitz-Riley PC boards that use a quad op amp. I will supply a TL-074 but any quad opamp will work. 

@imhififan 

IMO, parametric equalizer pair with active crossover can make a huge improvement!

I like the crossover of course. Many audiophiles will shy away from the EQ.  I see no need in adding anything digital either.

One can easily select a crossover point simply from the response curves now available for all drivers. I still go to Madisound first. They appear to have everything with good documentation. 

If people want to start discussing how to select drivers I'm up for it. We might even have a serious conversation and get something done.

HiFi was once and experimenter's hobby. I hope to bring some of that back. 

@steve59 

WOW, you guys complicated that conversation.

My Integrated amp rated at 250/8-425/4 shut down driving my power hungry speakers that have 2 pair of binding posts on back they’re 4 way 6 ohm rated and manufacturer recommends 500 watts. My question for the experts assuming I can get the amps output levels matched is, Would my integrated be less likely to overheat at the same spl if I added a 2nd amp, removing the strap to horizontally bi amp the speakers? also if I got output levels matched would amps of identical power be necessary or could I wire a pair of 350 mono's to the bass of each speaker and use the int to drive the top end?

Sometimes getting technical gets to the answer far better than a stack of nontechnical thought.

 When I tried to run my  ESLs off a high quality integrated I learned a lot. For instance the rated power is only deliverable into a resistive load. Anything reactive shut the amp down and a message came up  "check for shorted speaker wires"  That speaks volumes. The amp thinks anything below X ohms is a short. 

After reading the manual carefully I found that we could selectd 4 or 8 ohms but that did not affect the output power at all, only where the protection cut in. Selecting 4 was worse than 8 and shut downn sooner. This is not the behavior of a good solid amplifier.

Integrateds are not rough and ready power amps in general. 250/425 watts is power amp land and I mean big power amp land. How much does your amp weigh? Would you care to tell us its model? 
Sounds like a simple case of amplifier does not like speaker. A second amp will help indeed. Let the current integrated take the lighter load. 

Have you found an impedace curve for the speaker. Usually you can just google its name + impedance curve using images.

@byfwyne

So the bottom line is that there seems to be something to be said for light loading.

It was rather obvious to me from the start. The tubes love it.

Does anyone have any questions about why it works so well? The distortion reduction is usually 5 to 1 or more and the damping (regulation) doubles. Noise goes down 3 dB. All you give up is imaginary headroom.

For the record, almost all passive crossovers also include some form of EQ. If you plan to remove and replace a passive crossover you need to be prepared to do both.

A local speaker builder brought over a pair of his speakers without crossover for me to play with bi amping. The drivers are a $225 Scanspeak woofer and $60 Tweeter. $225 woofers only show up in $10,000 speakers. Most of the price of a complete speaker is in the cabinet and margin for the dealer. When an interested party took at a $10,000 speaker, priced out the components and found the drivers plus crossover to be about $1,000 or less. Its just the economics of the speaker business.

The drivers my local guy had chosen had such flat response that no EQ is needed nor does he build any into his series crossover. The impedance was amazingly constant and he feels this is the main virtue of his speaker. If a speaker has a flat impedance curve then damping is not so big an issue. Good drivers have pretty flat response, that is what you are paying for. 

I have never found a need to add EQ to a bi-amp system if the drivers are good quaity. Besides, in a bi-amp system you already have a woofer and tweeter control (you need only one) to adjust the tonal balance which I do at my own pleasure. The knob is right next to the volume control which I also adjust for my own pleasure. Its all so simple, but so hard to get across. I have to climb the wall of marketing just to get someone's ear. 

@shkong78 

Yes, turn them off when not listening. The cap died due to continued high temperature. Electrolytic caps do that.

@steve59 

I found a review at Sound Stage mag. Looks like a nice amp. This is interesting, from the review   https://www.soundstagehifi.com/index.php/equipment-reviews/934-hegel-music-systems-h360-dac-integrat...

  Like its predecessor, the H360 boasts a whopping 250Wpc into 8 ohms, or 420Wpc into 4 ohms. Its damping factor is over 4000 -- four times that of the H300. It should have no difficulty driving just about any pair of speakers it’s hooked up to.

I see he is impressed with daming factors that are very large and 4 times larger is, 4 times better?. We know 1000 or 4000 makes no difference. 

If you trip the thermal something has to be done. Can you now put your hand on the heatsinks after extended playing? If not you are still too hot.