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How to raise the total resistance of a speaker

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Posted on November 27, 2014 at 08:59:01
saki70
Audiophile

Posts: 274
Joined: February 2, 2006
 I see some speaker manufacturers , such as Coincident , producing 10 ohm speakers . And some OTL amp manufacturers , such as Atma-Spere , suggest speakers with higher resistance ratings than 8 ohms .It seems that most of the higher resistance speakers on the market are quite expensive as compared to the more plentiful ones of 8 ohms .
Is it possible to take a manufactured box speaker rated at 8 ohms and raise it to 10 , 12 , 14 or 16 ohms ? If so what is involved ? Could this be done at the time of the original speaker build , by the manufacturer , without too much trouble or expense ?

Thank you
Saki70

 

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RE: How to raise the total resistance of a speaker, posted on November 27, 2014 at 09:47:38
Steve O
Audiophile

Posts: 12383
Location: SE MI
Joined: September 6, 2001
 Not so long ago someone was marketing a toroid auto-transformer to do just what you describe. IIRC, it was designed specifically to take 2-4 ohm speaker loads and effectively raise the impedance into the 8ohm range to be more friendly with tube amps. Since the transformer had multiple taps, many impedance ratios were possible. These may still available. If not, you could probably have something custom wound to your specs.

 

RE: How to raise the total resistance of a speaker, posted on November 27, 2014 at 11:17:04
saki70
Audiophile

Posts: 274
Joined: February 2, 2006
 Thank you Steve .

Is an external device the only way to raise the impedance ?
Is the resistance , driver dependent ? In other words would the manufacturer need to change drivers to raise the resistance of the whole speaker ?

 

RE: How to raise the total resistance of a speaker, posted on November 27, 2014 at 11:26:56
Sebrof
Audiophile

Posts: 634
Location: AusTX
Joined: July 12, 2002
 These are the ones I remember, but I haven't seen much about them lately

 

RE: How to raise the total resistance of a speaker, posted on November 27, 2014 at 13:28:49
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 The reason why there aren't many high impedance speakers, is that when you use a solid state amplifier (as most people do), the amplifier will deliver less power into a higher impedance speaker. A higher impedance speaker won't make the most of a solid state amplifier, and as a result won't sound as good by comparison as a speaker with a lower impedance.

 

RE: How to raise the total resistance of a speaker, posted on November 27, 2014 at 13:39:57
Steve O
Audiophile

Posts: 12383
Location: SE MI
Joined: September 6, 2001
 The impedance of a speaker is an inherent characteristic of its design. To change it would usually require both driver and crossover changes. An external device is the only means I know of to change the impedance of a speaker w/o new drivers and Xover.

 

Those are the ones I remember.., posted on November 27, 2014 at 17:09:32
Steve O
Audiophile

Posts: 12383
Location: SE MI
Joined: September 6, 2001
 ...pricey little devils though.

 

RE: How to raise the total resistance of a speaker, posted on November 27, 2014 at 19:07:06
Duke
Dealer

Posts: 4429
Location: Princeton, Texas
Joined: March 31, 2000
 " A higher impedance speaker won't make the most of a solid state amplifier, and as a result won't sound as good by comparison as a speaker with a lower impedance."

Louder yes; better sound, maybe not.

As long as the amplifier isn't pushed into clipping, it's not necessarily going to sound any better into a low impedance load. In fact, many solid state amplifiers exhibit more benign distortion behavior into a high impedance load.

I make a speaker system that can be user-configured as either a 4-ohm load or a 16-ohm load. Its efficiency is high enough that it can be used either way with most amps. So far, everyone who's tried it both ways prefers the 16 ohm configuration even with solid state amps.

Duke

Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.

 

RE: How to raise the total resistance of a speaker, posted on November 27, 2014 at 19:27:17
Duke
Dealer

Posts: 4429
Location: Princeton, Texas
Joined: March 31, 2000
 In general, the speaker's impedance is established at the design phase, and it's hard to modify it after the fact.

Adding an autoformer, as has been mentioned, is one way.

In theory one could also add series resistance, BUT this will raise the effective Qes of the woofer and therefore the woofer/box interaction changes. And unless the original impedance curve was extremely smooth, the frequency response will probably change a bit. And finally, any additional amplifier power you might get from an OTL amp is wasted in heating up the resistor.

I design speakers specifically to work well with both solid-state amps and Atma-Sphere amps, and this starts with driver choice and continues through the crossover design stage, where a fair amount of attention has to be focused on the impedance curve (as well as on the frequency response curve). Then the enclosure design must take the effects of widely differing amplifier damping factors into account, if it's going to work with amps at both extremes.

Imo, ime, ymmv.

Duke


Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.

 

RE: How to raise the total resistance of a speaker, posted on November 27, 2014 at 20:45:14
hahax@verizon.net
Audiophile

Posts: 4310
Location: New Jersey
Joined: March 22, 2006
 You could put a resistor in series with the speaker input although I wouldn't recommend it. This is essentially the same as using long runs of very thin speaker wire which isn't a great idea. But then I think of my Sunfire amp with current and voltage outputs. The current output has a series resister to increase the output impedance(decreasing the damping factor). Carver did this to make the Sunfire sound more like a tube amp although if your speakers can be biwired he recommends using the voltage output for the bass(for better control) and the current output for the rest of the audio spectrum. As a friend likes to say - color me perfect.

 

RE: How to raise the total resistance of a speaker, posted on November 28, 2014 at 03:50:20
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
 Saki,

"Is it possible to take a manufactured box speaker rated at 8 ohms and raise it to 10 , 12 , 14 or 16 ohms?"

My short answer is no. I don't know if you meant to restrict this to OTL amps, but I would answer your question a different way, and I think it is the other side of the coin of what Maxhifi said.

The Tanny Red is valued by tube guys, because it is 16ohms, which means it is three decibels more efficient, which means that your power requirement just got cut in half. Also the higher impedence load is easier for a vacuum tube to handle, so the two go together. People usually don't run SS into high imp. and they usually don't run tubes into low imp.

Jamie



Big speakers and little amps blew my mind!

 

RE: How to raise the total resistance of a speaker, posted on November 28, 2014 at 03:58:39
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
 "I make a speaker system that can be user-configured as either a 4-ohm load or a 16-ohm load."

I like that. It makes a speaker flexible.


Big speakers and little amps blew my mind!

 

RE: How to raise the total resistance of a speaker, posted on November 28, 2014 at 04:36:32
kyle
Audiophile

Posts: 1839
Location: London Ontario
Joined: September 29, 1999
 Being a 16ohm speaker doesn't make the Red 3dB more efficient. There are other reasons, like sound quality, that make the Tannoys a popular speaker.

 

RE: How to raise the total resistance of a speaker, posted on November 28, 2014 at 05:20:41
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
 "Being a 16ohm speaker doesn't make the Red 3dB more efficient."

Can we agree that it is 16ohms and it is 3db more efficient?

"There are other reasons, like sound quality, that make the Tannoys a popular speaker."


That is true.


Big speakers and little amps blew my mind!

 

3dB more efficient than what?..., posted on November 28, 2014 at 06:06:38
Steve O
Audiophile

Posts: 12383
Location: SE MI
Joined: September 6, 2001
 Basic efficiency and impedance are two independent characteristics.

 

RE: 3dB more efficient than what?..., posted on November 28, 2014 at 07:04:02
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
 "Basic efficiency and impedance are two independent characteristics. "

That's why they have two different words for them.

I'm in no mood to get in a debate about the efficiency gain of a 16ohm speaker that is run by a tube amp, as opposed to an 8ohm speaker. Google didn't bring the proof easily to hand.

You win.

Pardon me if I carry on my merry way.


Big speakers and little amps blew my mind!

 

It's not a win/lose situation..., posted on November 28, 2014 at 08:11:33
Steve O
Audiophile

Posts: 12383
Location: SE MI
Joined: September 6, 2001
 ...I just don't understand the basis of your claim regarding the relationship betw eff and impedance or what your "reference" for this claim might be. Kinda surprised Google wasn't too helpful. ;-)

 

RE: It's not a win/lose situation..., posted on November 28, 2014 at 10:23:54
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
 I wish I had the technical answer for you, but I don't. Maybe someone who has a better technical background understands the argument will chime in.

As I understand it; using a tube amp, and all else being equal, a 16ohm driver will be 3db more efficient than an 8ohm driver.

People usually think in SS terms, where if you go from 8ohm to 4ohm, then you pick up power. But with tube amps it runs in the other direction. You pick up power as you increase impedence, up to a point where there is a dimishing rate of return, which is why you don't see 32ohm drivers. Although you once did see them when tubes were king.

Jamie



Big speakers and little amps blew my mind!

 

RE: How to raise the total resistance of a speaker, posted on November 28, 2014 at 10:57:49
saki70
Audiophile

Posts: 274
Joined: February 2, 2006
 Mr. Steady ;
No not OTL's only , actually SET's . I am seeking a SET friendly speaker , with at least a 10" woofer , that is not akin to a kegerator .
I don't have a lot of money to buy the usual suspects so I was looking for alternatives .

Thank you to all for the terrific information . I have learned something today !

Happy Tunes
saki70

 

RE: How to raise the total resistance of a speaker, posted on November 28, 2014 at 11:09:24
rws
Audiophile

Posts: 303
Location: Minnesota
Joined: September 7, 2004
 would this be the "speltz Zero autoformers?

I think his website is zeroimpedance.com






"Sometime I will have to give account of myself. How would the Father in heaven judge me if I followed others and not Him", Anton Bruckner

 

RE: How to raise the total resistance of a speaker, posted on November 28, 2014 at 11:11:12
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
 Cool! You may have to await a final verdict as to whether I am full of s*%t or not. :)

Jamie

Big speakers and little amps blew my mind!

 

RE: It's not a win/lose situation..., posted on November 28, 2014 at 19:02:42
kyle
Audiophile

Posts: 1839
Location: London Ontario
Joined: September 29, 1999
 If you have a circuit with an output transformer with a 2.5K Primary and an 8 ohm secondary and another identical circuit with a 2.5K transformer with a 16 ohm secondary with each connected to an appropriate speaker load, the power output will be the same. You can stack the speakers in a number of ways and you can rephrase the question in any number of ways but your initial question on the HiEff board remains the same. You don't get 3dB magically.
There's no free lunch.

 

RE: It's not a win/lose situation..., posted on November 29, 2014 at 03:04:04
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
 "There's no free lunch."

Yes, that's always seems to be the case.

"you can rephrase the question in any number of ways"

Once more into the breach;

Then why does a solid state amp put out more wattage the lower the speaker impedence? It's almost like a free lunch.


Big speakers and little amps blew my mind!

 

RE: How to raise the total resistance of a speaker, posted on November 30, 2014 at 18:57:43
Don Reid
Audiophile

Posts: 890
Location: Rural NW Georgia
Joined: February 2, 2001
Contributor
  Since: April 1, 2010
 Maxhifi wrote: "The reason why there aren't many high impedance speakers, is that when you use a solid state amplifier (as most people do), the amplifier will deliver less power into a higher impedance speaker. A higher impedance speaker won't make the most of a solid state amplifier, and as a result won't sound as good by comparison as a speaker with a lower impedance."

Like so many things in both life and audio your statement is true except for when it is not. As an example my Pass built First Watt F-3 solid state amplifiers are rated for a output of 15 watts into eight ohms but only 10 watts into either four or sixteen ohms.
I dream of an America where a chicken can cross the road without having it's motives questioned.

 

More Wattage, posted on December 1, 2014 at 08:46:03
Inmate51
 Watts is a measure of energy used and is a derivative/result of Ohm's Law. Current, voltage and resistance determine watts. This is ONE reason why great amplifiers are designed to produce "more than adequate" current - to deal with low resistance speakers.

Just because an amp/speaker circuit can consume 8 billion watts driving a 2 ohm load doesn't mean that it's louder than an amp/speaker circuit which only consumes 1 billion watts into an 8 ohm load.

And let's not forget the speaker's reactive component.

:)

 

RE: How to raise the total resistance of a speaker, posted on December 1, 2014 at 20:55:56
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 What an awesome anplifier to own, yes of course I was making a generalization, I am not sure what mechanism limits current in the Pass amp but it doesn't matter, that is clearly a very specialized (and interesting) design. I have always wanted to hear a Pass amplifier, I really think his design philosophy is cool.

 

But answering Mr Steady's question a little more directly..., posted on December 2, 2014 at 19:20:08
Steve O
Audiophile

Posts: 12383
Location: SE MI
Joined: September 6, 2001
 ...at a high level, the reason a solid state amp might appear to put out more power into lower impedances is that it tends to approximate an ideal voltage source. i.e. zero output impedance/infinite current delivery capability. So...if our voltage source amp can deliver say, 16W into 16ohms, that's 16V across the 16 ohm load. Drop the load to 8 ohms and the 16V remains constant so now we have 16^2/8=32W. Drop the load to 4 ohms and we get 64W and so on. Few amps have the output stage or PS beef to actually accomplish doubling of power when impedance is halved but the trend is present. As always, there are exceptions, notably the Mac SS amps with autoformer outputs. These tend to deliver the same power into any load that matches the tap impedance...just like a transformer coupled tube output stage.

Since this is a high level discussion, we'll avoid the issue of non-optimum primary to secondary coupling that occurs with most OPTs incorporating tapped secondarys when used with the lower impedance taps. I believe this is what gives rise to the impression that transformer coupled tube amps do better delivering power to high impedance loads.

 

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