Cornwalls - 4 Ohm vs. 8 Ohm

[richieb]

I have seen that several forum members run a variety of Klipsch models at 4 Ohm. On my Cayin tube amp both 4 and 8 Ohm is available. Will it do any harm or, what is the advantage by switching from 8 to 4 Ohms to run my Cornwalls?

Always looking for that little edge.

[DeanG Crossovers]

Not an easy question to answer. You should try both and see what sounds best. There will be a difference.

The old Klipsch networks are reactive as hell. You might consider using some swamping resistors with the Cayin. Get yourself two 15 ohm 12 watt resistors, and use one for each channel -- strapping each in parallel with the amp's 4 ohm outputs.

[Klipsch RF7]

Dean,

What would you recommend for the RF-7's?

[mopar dave]

i'v tried both 4 and 8 ohm with my cornwalls and could honestly tell no difference. my networks have hovland caps and aircore inductors. dave

[BillH2121]

test

[BillH2121]

Dean - I'm also interested in the 4 ohm v. 8 ohm for RF-7s. Does it matter whether power is from ss or tube amp?

[Daddy Dee]

----------------

On 1/1/2005 11:55:54 PM DeanG wrote:

Not an easy question to answer. You should try both and see what sounds best. There will be a difference.

The old Klipsch networks are reactive as hell. You might consider using some swamping resistors with the Cayin. Get yourself two 15 ohm 12 watt resistors, and use one for each channel -- strapping each in parallel with the amp's 4 ohm outputs.

----------------

Dean,

When you talk about the old Klipsch networks being reactive, what do you mean by that? Also, wondering about how the swamping resistor works.

Thanks. BTW, you know my technical knowlege base is REALLY limited, so please type real slow when you have a chance to answer.

[leok]

Easy question to answer:

Use the lowest ohm output your amp has to offer. (if your amp has a 4 Ohm output, use it.) Plenty of reasons why ..

Leo

[DeanG Crossovers]

O.K. the following was written about the Chorus, and is typical of the older Klipsch speakers.

"The speaker's impedance varied widely, from a minimum of 4 ohms at 140 Hz to a maximum of 70 ohms at 2100 Hz. There were smaller peaks of 40 ohms at 26 Hz and 28 ohms at 75 Hz, and there was a dip to 5 ohms at 52 Hz. By conventional rating methods, it is a 4-ohm speaker, although its impedance is well above that value over most of the audio range. In view of this, its 8-ohm rating seems reasonable."

So, the impedance curve goes down, waaaay up, with up's and down's in the middle. Tube amps like benign impedance curves, and SET amps more so than any of them. In fact, a SET amp will actually track an impedance curve like the one above. Simply put, with many tube amps, and impedance curves like the ones in the older networks -- the speaker will deliver non-flat response. This is probably the main downside of voltage driven amps as opposed to current driven (SS).

The swamping resistor smooths out the impedance of the speaker, and helps the amp out. The downside here is that the resistor chews up some power. Basically, you lose about 3db of sensitivity. No free lunch -- but it does sound better. Of course, you need some power to do this. I wouldn't recommend doing it with the OTL.

[BillH2121]

Dean - would you recommend trying 4 ohms with my Mac 2105 and RF-7s?

[DeanG Crossovers]

RF-7's should definitely be on the 4 ohm taps of a tube amp.

[Daddy Dee]

Thanks Deano.

[Klipsch RF7]

----------------

On 1/2/2005 10:08:53 PM DeanG wrote:

RF-7's should definitely be on the 4 ohm taps of a tube amp.

----------------

Dean, how bout the KG 5.5's?

[DeanG Crossovers]

Don't know. You would have to try both ways.

[Dflip]

I prefer the sound from the 4 ohm tap with my McIntosh MC-30 and Cornwalls. It provides a better bass end and this option was recommended to me by several other owners of the MC-30's. I agree with their opinion.

Don

[dodger]

The 4 ohm tap was suggested to me. I did notice an improvemrnt. Used on both tube and SS McIntosh.

dodger

[tkot]

the 4 ohm setting will produce more power, but, it may also cause the amp to run hotter or even overheat under long term high power uses, such as pounding the tunes at a party

jay

[dodger]

----------------

On 1/3/2005 12:55:18 AM tkot wrote:

the 4 ohm setting will produce more power, but, it may also cause the amp to run hotter or even overheat under long term high power uses, such as pounding the tunes at a party

jay

----------------

To be honest, I have not found overheating. It may be my combination, but with Klipsch as efficient as they are, that luckily has not been an issue.

dodger

[leok]

tkot,

Using the lower impedance output reduces (increases impedance) the AC or audio load seen by the output tubes. On the other hand, the plate voltage swing increases. The DC or bias load stays the same. If the amp is operating Class-A, however, the impact on output tube dissipation is minimal .. might actually be less (too early for that kind of math).

Leo

[Cleve]

----------------

On 1/3/2005 1:00:32 AM dodger wrote:

----------------

On 1/3/2005 12:55:18 AM tkot wrote:

the 4 ohm setting will produce more power, but, it may also cause the amp to run hotter or even overheat under long term high power uses, such as pounding the tunes at a party

jay

----------------

To be honest, I have not found overheating. It may be my combination, but with Klipsch as efficient as they are, that luckily has not been an issue.

dodger

----------------

Hmmmm, my McIntosh Mc2205 produces somewhat LESS heat with the Klipsch's hooked to the 4 ohm autoformer taps, compared to the 8 ohm. Subjective sound levels on the 4 ohm tap is slightly higher too (I'll have to measure it later today, since I now own a sound level meter)