I Should Know This, But I Don't!

[buskersball 0]

I am running a pair of db tops with 8ohm JBL 15" speakers in. I also use a pair of HZ subs (just one coil) at 8ohms.

My amp/mixer is a Dynacord Powermate

 

I can wire the subs to have both coils working, which would then produce a load of 4 ohm...so I would have 8ohm tops and 4 ohm subs...and both coils would be working in each sub.

 

Is there any advantage in doing this? ie Would the subs be louder with both coils working?

 

(The Dynacord allows 3 x 8ohm speakers per channel...so presumably goes down to 2 ohm or thereabouts)

Thanks in advance

[Stephen_N.I. 0]

I don't think you're right in what your saying.

 

If you wire a 4 ohm load in parallel to both coils you present a 2 ohm load on the amplifier, therefore making life a bit easier on it.

 

Do a google search to confirm this.

[buskersball 0]

I don't think you're right in what your saying.

 

If you wire a 4 ohm load in parallel to both coils you present a 2 ohm load on the amplifier, therefore making life a bit easier on it.

 

Do a google search to confirm this.

 

The HZ sub contains a driver with two coils. Each is rated at 300w and 8ohm. According to HZ if you connect them together this makes a 4 ohm, 600w bin. What difference (apart from the increased power rating) would it make to the sound...would it be more efficient and how would it affect the 8 ohm tops/amp output?

 

[TonyB 0]

Looking at the spec of the Dynacord Powermate, you can either have dual output (stereo) or single channel output (mono)

 

Two sockets are for the stereo output and the single socket is for mono output. You can either use stereo or mono but not both together.

 

The amp will also only go to 4 Ohms. If wiring the sub for two coil gives 4 ohms, with 8 ohm tops, the total impedance will be 2.67 ohms which the amp will not cope with.

 

But there are exceptions which depend on how the sub crossover is wired.

 

For example, the Peavey pro sub is 4 ohms and it is designed that connecting a 4 ohm top to the sub, the amp will still see 4 ohms.

 

If the HZ sub is designed similarly, then you may be okay but you need to check the sub spec. One way to tell is if the sub has an "input" and "output" socket for the speakers.

 

If you can plug the top into either socket in the sub then chances are the series rule will apply and the amp will see 2.66 ohms.

Edited March 17, 2008 by TonyB

[buskersball 0]

 

 

The amp will also only go to 4 Ohms. If wiring the sub for two coil gives 4 ohms, with 8 ohm tops, the total impedance will be 2.67 ohms which the amp will not cope with.

 

.

 

According to the Dynacord manual it is possible to connect 3 x 8ohm speakers to each channel. Its a Powermate 1000

The back of the HZ bins have 4 speakons. Two are for coil 1, and 2 are for coil2. If you wanna use coil 2 you connect the speakons to the -1 and -2 inputs of channel two. According to HZ if you take a lead out of coil1 and put it into coil 2 it makes the whole cab 600w and 4ohm.

I'd then be running 600w, 8 ohm tops and 600w 4 ohm subs. Would this sound better, worse, or the same?

Are 3 x 8ohm speakers equivalent to 1 8ohm and 1 4ohm in parallel?

 

[TonyB 0]

According to the Dynacord manual it is possible to connect 3 x 8ohm speakers to each channel. Its a Powermate 1000

The back of the HZ bins have 4 speakons. Two are for coil 1, and 2 are for coil2. If you wanna use coil 2 you connect the speakons to the -1 and -2 inputs of channel two. According to HZ if you take a lead out of coil1 and put it into coil 2 it makes the whole cab 600w and 4ohm.

I'd then be running 600w, 8 ohm tops and 600w 4 ohm subs. Would this sound better, worse, or the same?

Are 3 x 8ohm speakers equivalent to 1 8ohm and 1 4ohm in parallel?

 

That makes a difference! I was looking at the Powermate 600. The 1000 says that it can safely handle 2 x 870 watts into 2.66 ohms".

 

Yes the bass will sound louder as there will be a bigger cone area thumping it out.

 

Yes 3 x 8 ohm speakers gives the same impedance as 1 x 8 ohm + 1 x 4 ohm i.e. 2.67 ohms

 

 

[buskersball 0]

That makes a difference! I was looking at the Powermate 600. The 1000 says that it can safely handle 2 x 870 watts into 2.66 ohms".

 

Yes the bass will sound louder as there will be a bigger cone area thumping it out.

 

Yes 3 x 8 ohm speakers gives the same impedance as 1 x 8 ohm + 1 x 4 ohm i.e. 2.67 ohms

 

Gracias!

I'll give it a try this weekend...at the moment the JBL's are overpowering the HZs (although I'm being fussy!)

This may redress the balance

 

[nigelwright7557 0]

Gracias!

I'll give it a try this weekend...at the moment the JBL's are overpowering the HZs (although I'm being fussy!)

This may redress the balance

 

The power output obviously comes from a transformer then pwoer supply circuit then through the output transistors to the speakers.

 

If the impedance is too low then too much current will be taken before the maximum voltage output possible is reached. This will probably blow fuses (if fitted! ) or fry the output transsitors.

 

If the impedance is too high then maximum volts will be reached but maximum current wont be achieved.

 

This means there is an optimum speaker impedance.

On most disco amps this is 4 ohms but can go down to 2 ohms or less on very high power amps.

 

[nigelwright7557 0]

The HZ sub contains a driver with two coils. Each is rated at 300w and 8ohm. According to HZ if you connect them together this makes a 4 ohm, 600w bin. What difference (apart from the increased power rating) would it make to the sound...would it be more efficient and how would it affect the 8 ohm tops/amp output?

 

Surely it depends on how you wire the coils ?

 

If they are wired in parallel then you get 4 ohms.

If you wire them in series you get 16 ohms.