Markbass

[WAYNESWORLD]

Sorry if this is the wrong place if not could you direct me to the right one.

My question is if a CMD 121h combo is 8 ohm and both speaker and driver are 8 ohm  which I thought they were how does that work. Can the crossover within the cab sort this out? Or are the speaker and horn 4 ohm and run in series  which means if the horn blows does this have an effect on the overall ohms.please forgive my ignorance but I would like to be educated on this subject. Thanks

[BassBunny]

The way speaker cabs that have a main driver/speaker and tweeter/horn work is that there is a crossover network in circuit. This feeds certain frequencies to either main speaker or the horn, depending on the crossover design, so only one is actually in circuit at any one time.

The speaker and horn would generally be the same impedance so no matter which one is actually in circuit the amp sees the same impedance.

[WAYNESWORLD]

Thanks for that. I think I understand. So what you saying is regardless of the speaker and the horn driver both being 8 ohms once the signal hits the amp it only see’s 8 ohms because of the crossover. So am I correct in assuming that if the speaker was fed direct to the amp bypassing the crossover and another  connection the horn through the crossover would this would give a total of 4 ohm load for the  cab. Thanks.

 

[Dad3353]

6 minutes ago, WAYNESWORLD said:

Thanks for that. I think I understand. So what you saying is regardless of the speaker and the horn driver both being 8 ohms once the signal hits the amp it only see’s 8 ohms because of the crossover. So am I correct in assuming that if the speaker was fed direct to the amp bypassing the crossover and another  connection the horn through the crossover would this would give a total of 4 ohm load for the  cab. Thanks.

 

That's probably close to what would happen; it has to be said that these '8 Ohm' figures are not absolute, but in fact vary according to the frequencies and currents applied, and are really just 'nominal'. I'm guessing that there's an un-asked question here somewhere; what problem or issue are you thinking of solving in this way..? Why do these impedance figures matter to you..? 

[BassBunny]

13 minutes ago, WAYNESWORLD said:

Thanks for that. I think I understand. So what you saying is regardless of the speaker and the horn driver both being 8 ohms once the signal hits the amp it only see’s 8 ohms because of the crossover. So am I correct in assuming that if the speaker was fed direct to the amp bypassing the crossover and another  connection the horn through the crossover would this would give a total of 4 ohm load for the  cab. Thanks.

 

As @Dad3353has already explained that is pretty much the case but if you connected the speaker and horn in that way, bypassing the crossover, the horn would probably last a nanosecond before imploding when you started playing.

[Dad3353]

1 minute ago, BassBunny said:

As @Dad3353has already explained that is pretty much the case but if you connected the speaker and horn in that way, bypassing the crossover, the horn would probably last a nanosecond before imploding when you started playing.

 

I read it as keeping the crossover to the horn (so still 'protected...), but connecting the bass speaker directly. I'm wondering what benefit is being looked for in that scenario. The speaker would receive high frequencies which it could not produce well (that's the horn's job...), so why do it..?

[BassBunny]

34 minutes ago, Dad3353 said:

 

I read it as keeping the crossover to the horn (so still 'protected...), but connecting the bass speaker directly. I'm wondering what benefit is being looked for in that scenario. The speaker would receive high frequencies which it could not produce well (that's the horn's job...), so why do it..?

Ah, my bad. I didn't read it properly. In that case I can only assume the op is trying to present 4 ohms to the amp to try an get the full output of the amp. But not a very elegant solution.

[Dad3353]

3 minutes ago, BassBunny said:

Ah, my bad. I didn't read it properly. In that case I can only assume the op is trying to present 4 ohms to the amp to try an get the full output of the amp. But not a very elegant solution.

 

In that scenario, the speaker would receive half of the power delivered, the other half going into the crossover. Net phonic result : nowt, no more volume than the speaker being driven by the crossover.

[WAYNESWORLD]

Hi guys thanks so much.I must explain the reason for the question. Not looking for any net gain just pure interest in expanding my knowledge. I’ve got a Mark CMD 112 h bass which works perfectly on its own but when linked to another  MB cab of same spec the combo has a tendency to cut out the internal speaker/ horn whilst still powering the extension cab.I’ve read of this happening a lot of times in various forums.. The combo is new so could always be returned to be checked. All cables connections sockets  internal wiring to both crossovers have been checked. As far as amp settings go please believe I know what I’m doing and understand overdriving the pre amp and also any thermal cut outs that could occur. The only thing I haven’t give a go is a different cab which probably is a good idea. I appreciate all your input folks thanks again.

 

[yorks5stringer]

Sounds as if there is a problem as I have a CMD 121P which I occassionally link to a NY121 cab to no detriment to either. This then takes the ouput from 300W to 500W which is what is designed to happen.

Edited January 29, 2023 by yorks5stringer

[Dad3353]

15 minutes ago, WAYNESWORLD said:

Hi guys thanks so much.I must explain the reason for the question. ...

 

When you write '... has a tendency to cut out..., do you mean that sometimes it does; at other times it doesn't..? If so, it's definitely an intermittent, faulty, external speaker connection, as that should either always happen (by design...) or never happen (which is a more 'normal' behaviour...). Being new, I'd take or send it back for repair/replacement. I wouldn't get into esoteric fiddling about; there's something wrong which should not be wrong on a new amp.

Edited January 29, 2023 by Dad3353

[WAYNESWORLD]

Hi guys thanks so much.I must explain the reason for the question. Not looking for any net gain just pure interest in expanding my knowledge. I’ve got a Mark CMD 112 h bass which works perfectly when linked to another  MB cab of same spec the combo has a tendency to cut out the internal speaker/ horn. I’ve read of this happening a lot of times. The combo is new. 

[WAYNESWORLD]

2 hours ago, Dad3353 said:

 

When you write '... has a tendency to cut out..., do you mean that sometimes it does; at other times it doesn't..? If so, it's definitely an intermittent, faulty, external speaker connection, as that should either always happen (by design...) or never happen (which is a more 'normal' behaviour...). Being new, I'd take or send it back for repair/replacement. I wouldn't get into esoteric fiddling about; there's something wrong which should not be wrong on a new amp.

Think you’re right. May try a different cab just to be sure before returning the combo.Thanks for your input much appreciated.