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impedance matching box

#2
I don't think there are any boxes that could put more power into your cab. They might pull more out of your amp, but the extra power would be wasted as heat. If that is indeed accurate then they just raise the electric bill and add unneeded stress to your amp....................but I could be wrong. :)
 
#4
I think what he is referring to is a box which - all it really does - is have input options for either series or parallel connection so that you don't have to use a modified cable, just ordinary cabling and you can plug in several cabinets in different combinations to achieve the total impedance load you prefer.

There is no such thing as an impedance matching box that gets you more power as opposed to just absorbing power and turning it into heat. What I mentioned above was just a box that handled the wiring choices for you so you didn't need to carry around modified cabling.
 
#9
line6man said:
Why is the maximum power handling capability of the transformer given in Watts?:confused:
Shouldn't it be in Volt-Amperes, as the impedance is not going to be purely resistive?
Click to expand...

Probably because amplifiers are rated in watts, and anything else would confuse most people :p

EDIT: Or because the transformer will see a purely real input power, even though its own impedance is complex? Again, its been a while since I've done this.
 
#12
GrowlerBox said:
Did that -- still doesn't look like it would do anything useful. There's no advantage to "getting the full power" out of your head if you're not using it to drive speakers.
Click to expand...

The impedance transformer that warnergt references serves two useful purposes:
- it allows you to convert an 8 ohm load to a 4 ohm load, thereby increasing the power output of the amplifier (if it is solid state) under this load and sending most of this increase to the cabinet producing a ~3 db increase in SPL.
- it allows you to convert a 2/4 ohm cabinet combination to 4/8 ohms so that it now meets the minimum impedance requirement of the amplifier. Using combinations of cabinets increases the SPL, so you get more sound pressure with the same power output from the amplifier.

Only a very small amount of power is lost through the transformer. If it didn't do anything useful Udo wouldn't have wasted his time designing the product and bringing it to market.

Jim
 
#14
jsbarber said:
The impedance transformer that warnergt references serves two useful purposes:
- it allows you to convert an 8 ohm load to a 4 ohm load, thereby increasing the power output of the amplifier (if it is solid state) under this load and sending most of this increase to the cabinet producing a ~3 db increase in SPL.
- it allows you to convert a 2/4 ohm cabinet combination to 4/8 ohms so that it now meets the minimum impedance requirement of the amplifier. Using combinations of cabinets increases the SPL, so you get more sound pressure with the same power output from the amplifier.

Only a very small amount of power is lost through the transformer. If it didn't do anything useful Udo wouldn't have wasted his time designing the product and bringing it to market.

Jim
Click to expand...

I'll go along with the second use -- if you have a cabinet that provides a lower impedance than your head can handle and you need to increase it.

With respect to the first "advantage": assuming no losses to heat and a full doubling of the power output into the existing cab by halving its impedance, you would indeed get a 3 dB increase in SPL. Even this is hardly useful in a real setting, in which you would in any case be lucky to get a 2 db increase. As I said, if you're not using the power to drive more speakers, it's wasted effort. I didn't see what it cost on the linked page, but if it's Glockenklang I'd be guessing quite a lot, possibly enough to get another cabinet.
 
#15
jsbarber said:
The impedance transformer that warnergt references serves two useful purposes:
- it allows you to convert an 8 ohm load to a 4 ohm load, thereby increasing the power output of the amplifier (if it is solid state) under this load and sending most of this increase to the cabinet producing a ~3 db increase in SPL.
Click to expand...
That violates at least three laws of physics. It will allow you to run a 4 ohm cab with an amp that has an 8 ohm minimum load rating, which is rare. It cannot deliver more power. And even if it magically could at full power the result would be 2dB additional output, best case, while in most cases there would be no increase. For the price of it and the weight you might as well just get an appropriate amp.
 
#16
billfitzmaurice said:
That violates at least three laws of physics. It will allow you to run a 4 ohm cab with an amp that has an 8 ohm minimum load rating, which is rare. It cannot deliver more power. And even if it magically could at full power the result would be 2dB additional output, best case, while in most cases there would be no increase. For the price of it and the weight you might as well just get an appropriate amp.
Click to expand...

I have a pair of 8 ohm cabinets and a two channel power amplifier which can deliver 400 watts per channel with 4 ohm loads, or 800 watts in bridged mono mode into an 8 ohm load. This transformer allows me to use both cabinets in bridged mono mode and realize the full 800 watt capability of the amplifier, rather than 200 watts into each without the transformer. I have been told it is >90% efficient yielding close to a 3db increase in SPL.

Would you care to list the 3+ laws of physics that are violated?

I really couldn't care less how rare the situation is, it works for me.

Jim
 
#18
billfitzmaurice said:
That violates at least three laws of physics. It will allow you to run a 4 ohm cab with an amp that has an 8 ohm minimum load rating, which is rare. It cannot deliver more power. And even if it magically could at full power the result would be 2dB additional output, best case, while in most cases there would be no increase. For the price of it and the weight you might as well just get an appropriate amp.
Click to expand...

Lets make a few approximations/assumptions, just to simplify the situation:
1)The amplifier is running well above its minimum impedance, so it can supply as much current to the load as needed to match its output voltage (see 2)

2)The amp supplies a constant voltage, and the current (and thus power) is determined by the impedance of the load.


If these assumptions are moderately valid, then by my understanding, the transformer would bump up the voltage to the load, and pull more power from the amp to do this. The amp sees a 4 ohm load, and thus outputs more current (and more power) than if the 8 ohm load were connected directly. (The transformer does not increase the power magically, it just forces the amp to supply more current, which is fine if the amp is still seeing a load above its minimum impedance.)

I'm not disagreeing that the change in output will be significant (I don't really know about that), but it doesn't seem to violate any laws of physics as far as I can tell.
 

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