Impedance question two different ohm cabs

gimmeagig

gimmeagig

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Feb 25, 2004
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#1
Hi,

I have a EBS Reidmar 502 It can handle a 2 ohm load. I want to use a 8 ohm and a 4 ohm cab together. The Reidmar has one speakon output only. If I go out of the EBS into cab one and from that into cab two, are those cabs now connected in series?
I know the math but I am confused about series and parallel.Series would give me 12 ohm and at that my amp would be really anemic. I know I want parallel which would give me 2.6 ohms.
So if the Reidmar won't work because it has only one output, I have another EBS amp with two outputs. If I used each output for its own cab, would that be parallel and give me the 2.6 ohms I want?
 
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#4
I would imagine that 99% of all bass cabinets our there are wired in parallel. Plug in one 8-ohm cab and then a second cab, this one a 4-ohm cab, and you are looking at approximately 5.33 ohms (as seen by the amp). Unless the cabinet or the head specifically tell you that they are wired in series (like the old Music Man amps of the late 1980's) I would assume they are parallel.

Keep in mind that the 4-ohm cab will draw 2/3 of the overall power being used and the 8-ohm cab will draw the other 1/3, regardless of how many speakers are within each cab.
 
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#5
One output from an amp to the first speaker, then “daisy-chained” to the second; or, the amp has two outputs and you run two cables from it to two speakers.

Either connection scheme is parallel (unless the amp manufacturer specifies otherwise, as @ezstep noted).

Regards,
Wayne A. Pflughaupt

Ecclesia: Unique Arrangements of Hymns, P&W Standards, and Original Tunes
Administrator, Pedulla Club #45
Administrator, Official Tobias Club #133
Fretless Club #943
Big Cabs Club #23
My Rig: Stage and FOH Friendly
My Basses
 
#6
ezstep said:
I would imagine that 99% of all bass cabinets our there are wired in parallel. Plug in one 8-ohm cab and then a second cab, this one a 4-ohm cab, and you are looking at approximately 5.33 ohms (as seen by the amp). Unless the cabinet or the head specifically tell you that they are wired in series (like the old Music Man amps of the late 1980's) I would assume they are parallel.

Keep in mind that the 4-ohm cab will draw 2/3 of the overall power being used and the 8-ohm cab will draw the other 1/3, regardless of how many speakers are within each cab.
Click to expand...
2.66666 1/impedance A + 1/impedance B = 1/resulting impedance Same as resistors in parallel.
 
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#7
gimmeagig said:
Hi,

I have a EBS Reidmar 502 It can handle a 2 ohm load. I want to use a 8 ohm and a 4 ohm cab together. The Reidmar has one speakon output only. If I go out of the EBS into cab one and from that into cab two, are those cabs now connected in series?
I know the math but I am confused about series and parallel.Series would give me 12 ohm and at that my amp would be really anemic. I know I want parallel which would give me 2.6 ohms.
So if the Reidmar won't work because it has only one output, I have another EBS amp with two outputs. If I used each output for its own cab, would that be parallel and give me the 2.6 ohms I want?
Click to expand...
Checking for series/parallel is easy. If a speaker only works with another one plugged into it, it's wired for series.
 
#8
ezstep said:
I would imagine that 99% of all bass cabinets our there are wired in parallel. Plug in one 8-ohm cab and then a second cab, this one a 4-ohm cab, and you are looking at approximately 5.33 ohms (as seen by the amp). Unless the cabinet or the head specifically tell you that they are wired in series (like the old Music Man amps of the late 1980's) I would assume they are parallel.

Keep in mind that the 4-ohm cab will draw 2/3 of the overall power being used and the 8-ohm cab will draw the other 1/3, regardless of how many speakers are within each cab.
Click to expand...

2.67 ohms is the resulting impedance for
4 ohm & 8 ohm impedances in parallel.

4 x 8 = 32 divided by 4 + 8 = 12
32 / 12 = 2.66666… or 2.67

5.33 ohms happens to be resulting impedance of a 16 ohm impedance in parallel with an 8 ohm impedance.
16x8=128
16+8=24
128 / 24 = 5.33
 
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#9
ezstep said:
I would imagine that 99% of all bass cabinets our there are wired in parallel. Plug in one 8-ohm cab and then a second cab, this one a 4-ohm cab, and you are looking at approximately 5.33 ohms (as seen by the amp)./QUOTE]

How did you come up with a 5.33 ohm combining an 8 and a four old cabinet in parallel? The formula that I found tells me it would be 2.6 ohm.
I wish it was 5.3 because then I could use my Markbass amp in that combination, it can only go down to four ohms. But if the actual resistance is 2.6 then I would blow up the Markbass and that's why I'm looking at using the EBS amp.
Click to expand...
 
#11
WayneP said:
One output from an amp to the first speaker, then “daisy-chained” to the second; or, the amp has two outputs and you run two cables from it to two speakers.

Either connection scheme is parallel (unless the amp manufacturer specifies otherwise, as @ezstep noted).

Regards,
Wayne A. Pflughaupt

Ecclesia: Unique Arrangements of Hymns, P&W Standards, and Original Tunes
Administrator, Pedulla Club #45
Administrator, Official Tobias Club #133
Fretless Club #943
Big Cabs Club #23
My Rig: Stage and FOH Friendly
My Basses
Click to expand...

Mebbe only having one coffee on top of last night's old-fashions is affecting me but,
"One output from an amp to the first speaker, then “daisy-chained” to the second ..." I picture as
Amp---cab---cab, which would be series, no?
 
#13
gimmeagig said:
Hi,

I have a EBS Reidmar 502 It can handle a 2 ohm load. I want to use a 8 ohm and a 4 ohm cab together. The Reidmar has one speakon output only. If I go out of the EBS into cab one and from that into cab two, are those cabs now connected in series?
I know the math but I am confused about series and parallel.Series would give me 12 ohm and at that my amp would be really anemic. I know I want parallel which would give me 2.6 ohms.
So if the Reidmar won't work because it has only one output, I have another EBS amp with two outputs. If I used each output for its own cab, would that be parallel and give me the 2.6 ohms I want?
Click to expand...
I have an old Sunn cab from the 80's that has both parallel and series outputs, but you never see that now days. Industry standard connections are parallel connections, not series.

With a parallel connection it doesn't matter if you plug both cabs into the amp or one cab into the amp and the second cab into the first cab. Those are all parallel connections. Using one 8Ω cab with one 4Ω cab in a parallel connection results in a 2.67ohm load on the amp. The Amp will see that same ohm load regardless of whether both cabs are plugged into the amp or one into the amp and the second daisy-chained into the first cab. It will be 2.67Ω anyway you hook it up.
 
#14
vvvmmm said:
Mebbe only having one coffee on top of last night's old-fashions is affecting me but,
"One output from an amp to the first speaker, then “daisy-chained” to the second ..." I picture as
Amp---cab---cab, which would be series, no?
Click to expand...
No, parallel.
 
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#16
gimmeagig said:
I have another question I have two 4 ohm cabs plus one 8 ohm cab. What would be the impedance if I had all of those in parallel?
Click to expand...
Less than 2 ohms, no single channel power amp I am aware of can safely drive this combination.
 
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#17
vvvmmm said:
Mebbe only having one coffee on top of last night's old-fashions is affecting me but,
"One output from an amp to the first speaker, then “daisy-chained” to the second ..." I picture as
Amp---cab---cab, which would be series, no?
Click to expand...

Nope, parallel.

It’s actually difficult to accomplish a series connection between two cabinets. It would require some custom wiring that you would have to make yourself. Unless some manufacturer somewhere makes something off-the-shelf specifically for that purpose. But this is Talkbass – if it’s out there, someone here knows about it!

Here’s two speakers wired in series. As you can see, the (+) of one speaker connects to the (-) of the other:

iu

Now, here’s a group of speakers all connected parallel. All the (+) share the same connection, as do the (-).

iu

So it is with connecting two speakers to the amplifier. Even if “daisy chained,” the (+) and (-) are ultimately all connected to each other. So, parallel.

You have the same thing when the amp has dual speaker jacks, because the jacks are connected parallel internally.

Thus, either connection scheme is parallel.

Make sense?

Regards,
Wayne A. Pflughaupt

Ecclesia: Unique Arrangements of Hymns, P&W Standards, and Original Tunes
Administrator, Pedulla Club #45
Administrator, Official Tobias Club #133
Fretless Club #943
Big Cabs Club #23
My Rig: Stage and FOH Friendly
My Basses
 
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#19
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