Mismatched impedances

[Orion22b]

I have a Hartke A100 head unit and found listing for a 3 speaker 4ohm peavy amp. The A100 head is 100W and 8ohms would plugging it into a 4 ohm cabinet cause any problems other than lowered volume, and is there a way to rewire the amp to match the impedance of the speaker. Thanks!

 

[Hoochie Coochie Man]

Page 6 of the owners manual says that the output jack is used to connect the internal "8 ohm" speaker.

The owners manual makes no statement that the A100 can power a four ohm load.

https://storage.googleapis.com/hartke-production/uploads/documents/A70-100_ownman_v1s.pdf

There is no practical way to modify it to drive a four ohm load if it was not designed to do so.

 

[agedhorse]

That amp is not capable of safely driving anything less than an 8 ohm load.

 

[RandomKaren]

3 speaker 4 ohm cab? I remember a Trace Elliot 3x12, but nothing like that from Peavey.

 

[Wasnex]

I have a Hartke A100 head unit and found listing for a 3 speaker 4ohm peavy amp. The A100 head is 100W and 8ohms would plugging it into a 4 ohm cabinet cause any problems other than lowered volume, and is there a way to rewire the amp to match the impedance of the speaker. Thanks!

Really hard to understand what you are asking, but I am reasonably confident the answer is no .

Hartke A100 is 8 ohms minimum. It should be safe pushing a higher impedance, but not lower. AFAIK the actual impedance of the output section is actually much lower than 8 ohms. However, in general impedance matching is not relevant with solid state amps.

Impedance matching relates to tube amps, which typically use an output transformer (OT) to match the low impedance of the speaker(s) to the high impedance of the output tubes. There are some tube amps that can be rewired to drive different impedances. For example the Sunn 2000s had 4, 8, and 16 ohm output taps, but only two of the taps were hooked up at any given time. A Sunn 2000S can be set up for 4 and 8 ohm outputs or 8 and 16 ohm outputs.

I can think of a Peavey cab one might think of as three speakers at 4 ohms (1820):

Let's break down the model numbers: AFAIK 18" is the size of the woofer and 20 means it has two 10" (mid) drivers. The 18 is 4 ohms and the 10s combined are also 4 ohms. It has a crossover that splits the signal in high and low frequencies. Since both sections are 4 ohms, you can not push either with your Hartke.


Peavey also made a 3620 with two 18s. The 3620 is also 4 ohms.

 

[agedhorse]

The answer is still no.

 

[JohnnyChatter]

I have a Hartke A100 head unit and found listing for a 3 speaker 4ohm peavy amp. The A100 head is 100W and 8ohms would plugging it into a 4 ohm cabinet cause any problems other than lowered volume, and is there a way to rewire the amp to match the impedance of the speaker. Thanks!

Juice isn't worth the squeeze. Look for an 8 ohm cab and please don't try to rewire your amp… It's not very hard to accidentally hurt yourself.

 

[Makten]

It has nothing with "matching" to do. That particular amplifier can give its maximum current at 8 Ohms. Any lower than that, the current will be too high and the amp will get fried. Don't even think about trying.

 

[BassDaddySky]

So yeah, you need to match the cab to the amp.
You can plug higher ohm into the amp.
But not the other way 'round.
You need 8ohm total load or higher

Example, 8ohm cab into a 4ohm Amp is ok.
16 Into 4 is ok
4 into 4 ok
2 into 4 no Bueno!

 

[jefframm]

For the OP, the simple way to think of this is the lower the impedance of the "load" in this case the bass cabinet (the 4 ohm vs. the 8 ohm), the easier it is for the amplifier to send more current to the speaker. Some amps are designed to handle varying "loads" - but you always want to err on the side of caution. As a post above mentioned, if the amp in question wasn't designed to handle the increased current output, you could "fry" it - meaning that any number / type of components could fail if they aren't designed to handle the higher current output.

Just remember that the lower the impedance of the cabinet, the less resistance there is for current flow. You'll also frequently see that some amps will give a power rating for 8 ohm loads and a higher power rating for 4 ohm (or less) loads. That's the principal we're talking about in action. A simple example would be an amp that is rated at 350 watts into an 8 ohm load, and 500 watts into a 4 ohm load. Very common these days on newer amp designs. In those cases, the internal components are spec'ed to handle the higher current.

 

[Orion22b]

Ah thanks for all the replies, looking at other threads on similar topics I think I got the wrong idea on this topic, I'm looking for a cabinet with a matching impedance now.

 

[Orion22b]

3 speaker 4 ohm cab? I remember a Trace Elliot 3x12, but nothing like that from Peavey.

It's a peavy megabox, from what little I can find of it online I'm assuming it's either from the 90's or 2000's and it's very obscure. Listing for it is on vinted for £75 if anyone wants it since it seems like I'm looking for a different cab now

 

[agedhorse]

Matching impedance means something very different.

You need to look for a cabinet that's greater than or equal to the amp's minimum safe load. This is 8 ohms or higher.

 

[RandomKaren]

It's a peavy megabox, from what little I can find of it online I'm assuming it's either from the 90's or 2000's and it's very obscure. Listing for it is on vinted for £75 if anyone wants it since it seems like I'm looking for a different cab now

I found it, the Peavey 1516. Quite large and only 200 watts power handling. You could rewire it to be 16 ohms but then you wouldn't get the full power out of the Hartke. Thread on it here Peavey 1516 (old) cab

 

[agedhorse]

I found it, the Peavey 1516. Quite large and only 200 watts power handling. You could rewire it to be 16 ohms but then you wouldn't get the full power out of the Hartke. Thread on it here Peavey 1516 (old) cab

You can't rewire this cabinet to be any other impedance than the nominal 4 ohms that it was built as. The 8" drivers are crossed over and they must be used with the crossover in place.