# Speaker / impedance question.

Discussion in 'Amps and Cabs [BG]' started by Matthew Bryson, Mar 4, 2004.

1. ### Matthew BrysonGuest

Jul 30, 2001
I have a 2 x 15" cab that I got used. It needs one speaker re-coned and both speakers are out of it. I have a guy lined up who can re-cone the speaker and then I hope to be able to install the speakers myself. I have a few questions. First off - how do I make the connections? I'm assuming that I just solder the wires to the little tabs on the speakers, am I right? I don't need any special kind of solder or some special connector do I? My second question is regarding how exactly I wire things up. I figured I can get a wiring diagram from any number of sources - I just need to know whether to wire the speakers series or parallel to achieve the original ratings for the cab of 400 watts and 4 ohms. So, I did just a little bit of reading, and then checked the speakers to see if I could determine their impedance. I expected them to be either 4 or 8 ohms depending on how they were to be wired - but I found that they seem to be 6 ohms. Can anybody explain and tell me how the speakers should be wired?

2. ### pbdCommercial User

Jul 17, 2003
Metro Detroit
owner Procables N Sound
They make quick connect tabs for the speaker attachment. this way you won't have to heat up the soldering iron to remove or rewire them. If you do solder just use a standard 60/40 solder. I would wire them parallel. + of jack goes to each + of speaker same with -'s.

Series would be + of jack to plus of speaker A then - of speaker A to + of speaker B then - of speaker B to - of jack. It would be more efficient parallel.

Maybe someone else can give you the math why....

3. ### Matthew BrysonGuest

Jul 30, 2001

Can anybody else help explain this to me?

4. ### ostrzoskrzydly

Jul 1, 2003
There's no way you can wire them for 4 ohms, only 3 or 12.
Parallel is more efficient because it results in lower impedance.
Power is equal to difference of potentials(voltage) multiplied by current (amperage)
Ohm's Law says that the current is equal to voltage divided by impedance(for AC) or resistance (for DC). Since we're talking about AC here, it's equal to voltage divided by impedance.
Thus power is equal to square voltage divided by impedance = the smaller the impedance the bigger the power.
in symbols:
P=U*I
I=U/R
P=(U^2)/R

5. ### Matthew BrysonGuest

Jul 30, 2001

That's what I thought. So, on the back of the cab it says: 400 watts program / 4 ohms - and on a faded sticker on the speaker magnet it says 6 ohms. (6 and an upside down horse shoe thing) Should I assume that these are not the speakers that came in the cab? I wonder if they are even anything that I can really use?

6. ### ostrzoskrzydly

Jul 1, 2003
hrm, maybe it's 9 ? that'd make 4,5 which would generally be passable as 4,
are the speakers even 200 watts each ?
maybe those 6s used to be 8s but the sticker got faded so that it looks so...
what cab and what speakers are those ?

7. ### Matthew BrysonGuest

Jul 30, 2001
I have no idea

Yeah, I thought about that - but they really look like 6's, not parts of 8's...

Yamaha - which by the way, I've had a hard time finding any other Yamaha bass cabs around... I've wondered if it wasn't maybe really a keyboard or PA cab that somebody used as a bass cab - the prev. owner said it was a great full range bass cab, but he had it loaded with Black Widows.

8. ### ostrzoskrzydly

Jul 1, 2003
That's weird. Does it have a horn ? What happened to the BWs he had in it ? Chances are he just threw in some random speakers he had lying around :/ What does it exactly say on the speaker sticker ?

9. ### seanmI'd kill for a Nobel Peace Prize!Supporting Member

Feb 19, 2004
How did you measure the speakers? A multimeter will generally measure low since it is measuring DC resistence rather than impedance. 6 ohms is in the right range for an 8 ohm speaker. Maybe the 6 is the actual reading put on during QA?

Can your amp handle 2 ohms? If so, wire them in parrallel and don't wory about it, but don't add a second cab.

10. ### Matthew BrysonGuest

Jul 30, 2001
No, no horn - by full range I meant that the prev owner said it sounded good as a stand alone bass cab. I probably used the wrong word there - my bad.

The cab is definately Yamaha, or at least the handles and jack plate are becasue they say Yamaha on them - and the speakers have big Yamaha symbols on the dust caps. I have every reason to beleive that these are the original speakers for the cab - and the jack plate says 4 ohms...

The cab was actually given to me / traded by a guy who had inherted it from the old bass player of his band (the guy quit playing when he quit the band - gave away the 215 and a Hartke 3500 to new dude...) ...the guy that I got it from used BW's in it (he kept them) - I think he bought the BW's becasue of the blown speaker. I'm not sure if he blew the speaker or if it was the guy before him - I don't know if he ever used the Yamaha speakers. but I have no reason to think that he'd just throw in some random speakers to fool me - I really think they are the original speakers - or at least he thinks thaye are. And thet really seem to say 6 ohms (on both - looks like it to my wife too...) ...but, I suppose they could be 8's that are worn to look like 6's (on both?) ...this is all I know - I don't have the speakers with me to get any more info off of them.

11. ### Matthew BrysonGuest

Jul 30, 2001
I looked at a faded old sticker on the speaker magnet...

I don't know what that means

Actually, I don't have an amp. I just got the cab - I need to get the speaker re-coned and the speakers re-installed then I'll buy an amp head.

12. ### Petebass

Dec 22, 2002
QLD Australia
I always worry with speakers from era's gone by. Nowdays if it's a 15, chances are is was a bass speaker or PA. In the early days, guitarists used to believe that big speakers sounded big, so a few companies experimented with guitar cabs with 15's and 18's.

There's too many variables going on here. If it were me, I'd be posting the cab measusements and trying to find a couple of 15's that will match the cab.

Does the cab have any ports at the moment?

13. ### Matthew BrysonGuest

Jul 30, 2001
Yes, the cab has two ports.

The cab seems pretty small for a 2 x 15 - but I have no experience with big bass cabs.

The speakers appear to be the stock speakers for the cab.

The jack plate says 400 watts program (200 noise / 800 peak) and 4 ohms.

The last owner gigged the cab for two years powered by a Hartke 3500 although he had BW's in at the time.

The speakers seem to say 6 ohm on them.

I am very very confused

14. ### MJ5150ModeratorStaff MemberSupporting Member

Apr 12, 2001
Olympia, WA
I am the previous owner of this cab......

I used this cab for over a year with the exact speakers in it that are in your possession right now.....Yamaha speakers. Before I had the cab, the guy that gave it to me used it for a bass guitar also. The guy before HIM used it for a bass guitar as well. For the past four years, it was powered by that Hartke head I told you about. Before that, I am unaware what was used to power it.

The bottom speaker was damaged while I was using it. I played in a L-O-U-D rock band, and was pushing that cab full force for about an hour. After a set, we all heard this strange buzzing, and with the help of our drummer found it to be the speaker. I took it to a reputable music store in town, and they told me it needed to be reconed. I did not want to wait for that, so I asked about a new 15. Dude showed me the BW, and let me hear one in another cab. So, I bought one that day. Dude from the music store tells me it is not a good idea to have two different speakers in one cab, so I went back and bought the second BW. Those BW's are currently in my possession for two 115 cabs I am making.

All I can say is that cab performed for three years flawlessly with the Hartke 3500. It was always loud enough for me, and the last guy.

-Mike