Bass Amps, Speaker cables, ohms, etc...

[brett304]

Not real sure of how to word it... I would like to know the practical take on bass amps and pa stuff... I can't seem to find the approach to this that makes sense so I figured I'd just ask you all...

I have a harke 300 bass amp head... It has a direct out... Do I have to hook up a speaker to use this or is it necessary to have a load attached to the amp at all times??? IOW.. Can I use it direct only for recording??


Also say I have two cabinets... Can I hook up only one at a time?? Do I need to bridge my output??? Not sure what I mean, but for example : "I have a pa speaker that has two 1/4 inch inputs on the back of the cabinet... Can/ should I bridge both sides of an amp through one speaker... Or if I hook up two seperate, do they have to have matching wattages, etc? IOW, can I hook up one 15 in bas cab and a 12 in. pa speaker at the same time?? I'm pretty sure I understand about the part of sending too much wattage to a speaker and basic mis-matching, etc... But not totally sure...

One last piece... I recieved two cabinets with my head... A blown 15 and a two-ten cabinet... All Harke... Can I order/build an enclosure out of my cabinet... I assume definitely... But do these boxes have crossovers built into them optimized to the speaker??? It seems like they would have to in order to make your amp outputs plug and play with multiple enclosures, etc...

I would like to get a real nice speaker and use my harke head untill I can afford to buy a nice head at least six months later... I probably wouldn't need more than 300 watts but I want it to all be really nice...quiet...great for recording both direct (without any room signal) and still have the option of running direct and useing the amp at the same time... both for use as a stage monitor for small shows, or to use the enclosure for a miced version of my signal... ( I love mixing my direct signal with my mics... ) Anyway I'm sure that this shouldn't be a hard question and will probably clear up quite quickly and I'm sure I'm not the only one who would want or expect these options...

Thanks in advance, hopefully someone will see where I'm coming from and why I couldn't just look up all this info... sometimes an explanation from a human works wonders...Thanks... -Brett

 

[Farview]

I have a harke 300 bass amp head... It has a direct out... Do I have to hook up a speaker to use this or is it necessary to have a load attached to the amp at all times??? IOW.. Can I use it direct only for recording??

You would want to check with the people at Hartke. Most solid state amps will work fine without a speaker attatched, but there are exceptions. Make sure yours isn't the exception before you try it.

Also say I have two cabinets... Can I hook up only one at a time?? Do I need to bridge my output??? Not sure what I mean, but for example : "I have a pa speaker that has two 1/4 inch inputs on the back of the cabinet... Can/ should I bridge both sides of an amp through one speaker... Or if I hook up two seperate, do they have to have matching wattages, etc? IOW, can I hook up one 15 in bas cab and a 12 in. pa speaker at the same time?? I'm pretty sure I understand about the part of sending too much wattage to a speaker and basic mis-matching, etc... But not totally sure...

The two 1/4 jacks on the speaker cabinet are for daisy chaining speakers. The amp plugs into one input and you use another speaker cable to plug from the other 1/4 jack to another speaker cabinet. DO NOT PLUG BOTH SIDES OF A POWER AMP INTO THE TWO INPUTS OF ONE CABINET!!!!

As far as the rest of the questions quoted, I'm confused. Are you setting up a bass rig or a PA system? It makes a difference.

One last piece... I recieved two cabinets with my head... A blown 15 and a two-ten cabinet... All Harke... Can I order/build an enclosure out of my cabinet... I assume definitely... But do these boxes have crossovers built into them optimized to the speaker??? It seems like they would have to in order to make your amp outputs plug and play with multiple enclosures, etc...

There are not any crossovers in bass cabinets. (well, the ones with tweeters have a crossover for the tweeter)

I would like to get a real nice speaker and use my harke head untill I can afford to buy a nice head at least six months later... I probably wouldn't need more than 300 watts but I want it to all be really nice...quiet...great for recording both direct (without any room signal) and still have the option of running direct and useing the amp at the same time... both for use as a stage monitor for small shows, or to use the enclosure for a miced version of my signal... ( I love mixing my direct signal with my mics... ) Anyway I'm sure that this shouldn't be a hard question and will probably clear up quite quickly and I'm sure I'm not the only one who would want or expect these options...

The amp has the power, not the speaker. If the amp is 300 watts, get a 300 watt speaker.

 

[brett304]

Thanks

Okay, so my first stop would be the manual... I'll see what I can learn from it... But I'm thinking that since its a solid state with a tube preamp stage its probably going to be okay... Also on the direct out question, "Does it have a set output or will the master volume still control the output onto the direct out?"

So thanks for the answer on the bridgeing question...BUT can anyone tell me whether each side of the output on a dual channel amp (either bass or pa as I have both) needs to have both sides balanced.... Left rated at 350 and the right at 250... I know its safer for them to be, but how does this work?

Also anyone on the building my cabinet and ordering a bass amp capable speaker.... I would really like one really nice 12 to start... I want as clean as possible signal for recording (really important to not have scratch and hum, etc... I figure with a nice enough speaker and a real clean amp I'll be fine... I think that the enclosure should suffice rather than spend 800 on a "bagend brand" level speaker enclosure? Then only to have to spend that much on a head just to take advantage of my nice new homeade enclosure... Anyone on that????

Also for my purposes I'm assuming based off the really nice ampeg or gallien kruger lines that I would want to get an amp and speaker rated more like 600 watts... Could I continue to use my 300 watt head temporarily untill I could then save some more money? Impedences? etc... Make financial sense, real life application, etc...? Anyone? Thanks... -B

 

[Farview]

So thanks for the answer on the bridgeing question...BUT can anyone tell me whether each side of the output on a dual channel amp (either bass or pa as I have both) needs to have both sides balanced.... Left rated at 350 and the right at 250... I know its safer for them to be, but how does this work?

Each channel of the amp is independent. It is really two different amps in the same box. The amp is the power source. The wattage of the speaker is how much power the speaker will handle. If you put a 300 watt amp on a 100 watt speaker, you will blow the speaker. (if you turn it all the way up)

You don't have to have matched speakers on either side of the amp because you don't necessarily have the same signal going through both sides of the amp.

Also anyone on the building my cabinet and ordering a bass amp capable speaker.... I would really like one really nice 12 to start...

There aren't that many 12 inch bass speakers. 10's, 15's and 18's are the norm.

I want as clean as possible signal for recording (really important to not have scratch and hum, etc... I figure with a nice enough speaker and a real clean amp I'll be fine... I think that the enclosure should suffice rather than spend 800 on a "bagend brand" level speaker enclosure? Then only to have to spend that much on a head just to take advantage of my nice new homeade enclosure... Anyone on that????

The scratch and hum would come from the amp. It has nothing to do with the speaker.

Also for my purposes I'm assuming based off the really nice ampeg or gallien kruger lines that I would want to get an amp and speaker rated more like 600 watts... Could I continue to use my 300 watt head temporarily untill I could then save some more money? Impedences? etc... Make financial sense, real life application, etc...? Anyone? Thanks... -B

You can use a 600 watt speaker with a 300 amp without a problem.

 

[brett304]

again...

Thanks for the answers provided.... I still have some questions... I have both a pa amp and a bass amp... The PA amp has a seperate rotary dial for the output of the amp... And I could see that theory working there... However my bass amp doesnt have seperate dials for the output...

 

[Farview]

Thanks for the answers provided.... I still have some questions... I have both a pa amp and a bass amp... The PA amp has a seperate rotary dial for the output of the amp... And I could see that theory working there... However my bass amp doesnt have seperate dials for the output...

The bass amp is only one amplifier. It might have two speaker outputs, but it is only one amp, so it has one volume control.

The PA amp is two separate amplifiers in one case, that's why it has two volume controls.

 

[brett304]

On again

Okay... daisy chaining, does that split the wattage to each speaker??? And if it does split it, does it do it into halves or otherwise?? Can you then have two 10s and two 12s... one of each on each channel and if so does it change how much power goes to each enclosure?

Anybody have any suggestions on diy or should I move that question to another forum?

I'll need this info and knowledge in order to build my own setup and would like to figure it out for troubleshooting purposes when/if something goes wrong or just to be creative with my setup... For example could I use my pa speakers with my bass amp? The amp says its capable of operating at 4 oms or at 8 but 8 is its default.... My speakers are 250 watts at 8 ohms.. So as I understand it, my speaker will be fine as long as I don't turn it up too loud.. Mainly I'd just like to test how my amp sounds without the blown hartke cabinets... Try it out and see, consider how it would sound for recording, etc...

Thanks again... -Brett

 

[Dani Pace]

Just a few general tips about PAs and speakers... Whatever you do to one side (output) do to the other. Always turn off the power before plugging any speaker in or disconecting any and be sure the load is balanced on each side before turning the power back on. When you plug a second speaker into the second jack on a speaker you will be making a parallel conection (two 8 ohm speakers in parallel makes a 4 ohm load on the amp.) If you conect speakers this way to one side of the output, you must also conect speakers the same way to the other side in order to keep the load on the pa amp balanced.

 

[gecko zzed]

Not real sure of how to word it... I would like to know the practical take on bass amps and pa stuff... I can't seem to find the approach to this that makes sense so I figured I'd just ask you all...

I have a harke 300 bass amp head... It has a direct out... Do I have to hook up a speaker to use this or is it necessary to have a load attached to the amp at all times??? IOW.. Can I use it direct only for recording??


Also say I have two cabinets... Can I hook up only one at a time?? Do I need to bridge my output??? Not sure what I mean, but for example : "I have a pa speaker that has two 1/4 inch inputs on the back of the cabinet... Can/ should I bridge both sides of an amp through one speaker... Or if I hook up two seperate, do they have to have matching wattages, etc? IOW, can I hook up one 15 in bas cab and a 12 in. pa speaker at the same time?? I'm pretty sure I understand about the part of sending too much wattage to a speaker and basic mis-matching, etc... But not totally sure...

One last piece... I recieved two cabinets with my head... A blown 15 and a two-ten cabinet... All Harke... Can I order/build an enclosure out of my cabinet... I assume definitely... But do these boxes have crossovers built into them optimized to the speaker??? It seems like they would have to in order to make your amp outputs plug and play with multiple enclosures, etc...

I would like to get a real nice speaker and use my harke head untill I can afford to buy a nice head at least six months later... I probably wouldn't need more than 300 watts but I want it to all be really nice...quiet...great for recording both direct (without any room signal) and still have the option of running direct and useing the amp at the same time... both for use as a stage monitor for small shows, or to use the enclosure for a miced version of my signal... ( I love mixing my direct signal with my mics... ) Anyway I'm sure that this shouldn't be a hard question and will probably clear up quite quickly and I'm sure I'm not the only one who would want or expect these options...

Thanks in advance, hopefully someone will see where I'm coming from and why I couldn't just look up all this info... sometimes an explanation from a human works wonders...Thanks... -Brett

Let's tackle all this one step at a time:

1 The Hartke head with a line out is most likely to be okay by using this without speakers attached. However, discretion is the better part of credit cards, so check the manual.

2 The Hartke sounds like it has two speaker outputs, so yes, you can hook up two speakers. Again, check your manual, but I expect that these outputs are connected in parallel, which means that you can connect up two cabinets, both rated at 8 ohms, and the amp will 'see' 4 ohms which is usually safe for most contemporary amps. If you are not familiar with electronics and this seems strange, this is Ohm's law (for two impedances in parallel, 1/R = 1/r1 + 1/r2 (where R is the final impedance, and r1 and r2 are the impedances of the two speakers respectively)).

3 In terms of the power rating of the speakers, you can hook up pretty well what you like. You can drive a 50 watt speaker fine with that head . . . but, if you give it too much level (which can happen with big boomy bass notes or sudden transient slaps) you can wreck it. Perversely, hooking up a speaker with a higher power rating than the amp can cause more grief, because you can overdrive the amp without noticing it as easily . . . it is often more expensive to replace a blown amp than a blown speaker.

4 Your PA head is (as someone else noted) virtually two separate power amps in one box (unless it has a bridging option . . . but it would be wise to steer clear of this). This means each side can have different cabinets and different loads.

 

[Lt. Bob]

also ..... if you're gonna hook the bass amp to a PA speaker ..... you'd best be careful 'cause if you hit it too hard, you're likely to blow the horn which wasn't meant for bass guitar.
And you won't really see what it'll sound like as a bass rig 'cause a PA speaker is voiced very differently than a bass speaker.
And 300 watts is usually getting into the range of 'just enough' for bass. depending on what you do, you may not need more.
If you're doing loud band gigs with a pounding drummer, then I'd also want 600 watts so I'd have enough headroom. But I do quite a few gigs with an old 200 watt GK ...... it does fine unless it's a pretty loud gig, then it gets strained.

 

[Farview]

Okay... daisy chaining, does that split the wattage to each speaker??? And if it does split it, does it do it into halves or otherwise?? Can you then have two 10s and two 12s... one of each on each channel and if so does it change how much power goes to each enclosure?

It splits the power equally if the impedance of both speakers is the same. The size and the power rating of the speaker doesn't have any effect on this.

Anybody have any suggestions on diy or should I move that question to another forum?

You might want to save yourself some money and heartache and just buy a used bass cabinet. I don't want to discourage you, but there is a little more to this and you need more background to do this right.

I'll need this info and knowledge in order to build my own setup and would like to figure it out for troubleshooting purposes when/if something goes wrong or just to be creative with my setup... For example could I use my pa speakers with my bass amp?

You can, but it will sound like crap. The design of the speaker and the box it is in is different for a PA application than it is for a bass rig. You might notice that a popular ampeg bass cabinet has eight 10 inch speakers in it- you will never find a PA cabinet like that. If the PA cabinet has a tweeter, your bass amp will blow it across the room.

The amp says its capable of operating at 4 oms or at 8 but 8 is its default.... My speakers are 250 watts at 8 ohms.. So as I understand it, my speaker will be fine as long as I don't turn it up too loud.. Mainly I'd just like to test how my amp sounds without the blown hartke cabinets... Try it out and see, consider how it would sound for recording, etc...

Remember that if you run the amp at 4 ohms, you get twice as much power. If you hook two 8 ohm cabinets together, you will end up with a 4 ohm load.

 

[ggunn]

...this is Ohm's law (for two impedances in parallel, 1/R = 1/r1 + 1/r2 (where R is the final impedance, and r1 and r2 are the impedances of the two speakers respectively)).

Actually, it's not. Ohm's Law is V = IR (voltage is equal to current times resistance). Your math is correct, but it's not Ohm's Law.

 

[brett304]

Thanks again...

Sorry I haven't been very clear at times... I do my best to communicate and sometimes it just doesn't come out properly...Thanks for sticking with me... Anyway I'm still not sure how I want to proceed....

Last night I opened up my two ten cabinet and looked at how it was hooked up and it was exactly as I expected... Four wires that ran the two speakers to the input.. You mentioned that I shouldn't diy my cabinet, but I'm not sure why... I found speakers online for the purpose that seemed as if they'd be completely plug and play... I would like to try to keep the boxes and put my own speakers in there... Then I'm thinking that I'd like to buy a nice GK or Ampeg head to run it...

I know I said 300 watt, but its actually the 350 watt setup... The Transporter 3500 series... (sorry I wasn't trying to mislead anyone)... I havent been able to find the manual at all.. I did however find out that there are two versions of this amp... Still have more research to do, but i know it doesn't use tubes on the output section...

I'm thinking about going the 600 watt direction with the amp driving two tens and one 15... Any suggestions on how to approach this? If the answer is still buy one, then say it... The main thing is that I'll eventually need to learn this when I blow speakers on an amp or pa setup in the future...

Not very good with math or certain technical issues, but put it into real-life application terms, and I'll usually get it... Thanks for the answer on wiring into parallel... I still don't get how it divides up the power...But I will just always keep both sides equal (shouldn't be that hard right?)...

Still not sure on how to approach testing this equipment... Still haven't tried the direct line out thing yet...Better safer than sorry... The speakers are however definitely blown on the 15 and 1 or both of the tens... Thanks for any help and keep on... Thanks for filling the gaps in my understanding... -Brett

 

[Farview]

Some of the confusion is because this should really be 4 separate threads:

1. PA setup
2. Recording bass rig setup
3. Cabinet construction
4. Cabinet wiring

I understand that you are trying to use PA cabinets and amplifiers as part of a bass rig, but all of these concepts are not really related. It might be easier if you started a separate thread for each of the subjects.

 

[brett304]

Bass Setup...

On the bass setup... I don't want to use my pa speakers for that purpose... But I would like to test my bass head properly... I can't do that with my blown enclosures and wanted to try it on my PA speakers...

I do have a question on cabinet wiring, but not construction...

In order to find the answer I'm looking for maybe it would be better to ask it like this...

"If i have my 350 watt head with two outputs on it... One output to a 2 ten cab. and one to a 1 fifteen cab.. How much power would each speaker recieve and what must they be rated at... "

That is the current question... The later question would be on a 600 watt setup...

"If I wanted to buy a 600 watt head with two outputs and I wanted it to run a 1 fifteen cab. and a 2 ten cab., what wattages would each speaker need to be rated, etc..."

Hope that clears up my confusion... Thanks again... -Brett

 

[Farview]

On the bass setup... I don't want to use my pa speakers for that purpose... But I would like to test my bass head properly... I can't do that with my blown enclosures and wanted to try it on my PA speakers...

Now I get it! You can try it with the PA cabinets, but if there is a tweeter in the cabinet, don't turn it up too loud or you will blow it.

"If i have my 350 watt head with two outputs on it... One output to a 2 ten cab. and one to a 1 fifteen cab.. How much power would each speaker recieve and what must they be rated at... "

You want the 2x10 and the 1x15 cabnets to both have the same impedance. That way they will split the power equally. Since they will split the power equally, each cabinet will have to be rated for at least 175 watts.

Sometimes people get confused because they think of the 2x10 cabinet as two speakers. But when the two speakers are wired together, they become one thing.

"If I wanted to buy a 600 watt head with two outputs and I wanted it to run a 1 fifteen cab. and a 2 ten cab., what wattages would each speaker need to be rated, etc..."

Here is where it gets tricky. The amplifier will only put out 600 watts at a certain impedance. If that impedance is 4 ohms (for example) you would need two 8 ohm cabinets that could handle 300 watts each.

If you had two 16 ohm cabinets, you would be running the amp at 8 ohms. At 8 ohms, the amp is only pushing 300 watts.... At 2 ohms (two 4 ohm cabinets) the amp would be pushing 1200 watts...

So the ratings need to change depending on the impedance.

 

[brett304]

And Again....

Hey thanks, I've almost got the impedence thing now and how too subtract, etc. to get my values for building such a system... The extra confusion has come in on that I've been asking for use with the setup I have now, for the build I'd like to do, and for basic understand for use in later situations... Sorry again for not being clear...

Originally Posted by brett304
"If i have my 350 watt head with two outputs on it... One output to a 2 ten cab. and one to a 1 fifteen cab.. How much power would each speaker recieve and what must they be rated at... "

You want the 2x10 and the 1x15 cabnets to both have the same impedance. That way they will split the power equally. Since they will split the power equally, each cabinet will have to be rated for at least 175 watts.

Sometimes people get confused because they think of the 2x10 cabinet as two speakers. But when the two speakers are wired together, they become one thing.

So, if each cabinet is rated at 175 watts, how much would each speaker have to be rated at, etc, in relation to building???

 

[brett304]

Also..

Also, which style of cab. is usually better for recording with a mic? Ported or closed? Anyone have any ideas?

I would consider switching to a 1 15 in. system with a real nice tweeter and a ported box if it were likely to be nicer!?! Also what about an adjustable crossover point adjustment somewhere on the outside of the box.... Could be a really interesting tone adjustment I'm assuming!

 

[ggunn]

Not very good with math or certain technical issues, but put it into real-life application terms, and I'll usually get it... Thanks for the answer on wiring into parallel... I still don't get how it divides up the power...But I will just always keep both sides equal (shouldn't be that hard right?)...

When speakers are connected in parallel, the power that they get from the amp is inversely proportional to their impedance ratio. For example, if you have a 16 ohm speaker connected in parallel with an 8 ohm speaker (a total impedance of 16/3 = 5.33... ohms), the 16 ohm speaker will get 1/3 the power of the amp and the 8 ohm speaker will get 2/3 the power. Half the impedance => twice the power.

Note that that doesn't mean that the 8 ohm speaker will be necessarily louder; speaker efficiency is also a factor. It just means that twice the power will be dissipated in the voice coil of the 8 ohm speaker and you have to figure power ratings acordingly.

 

[Farview]

Also, which style of cab. is usually better for recording with a mic? Ported or closed? Anyone have any ideas?

It doesn't matter. Which ever cabinet will give you the sound you are looking for will be the one to mic.

I would consider switching to a 1 15 in. system with a real nice tweeter and a ported box if it were likely to be nicer!?!

I've never seen a 15 with a tweeter, the tweeters are normally in cabinets with 10 inch speakers. Personally, I find the tweeters to be pretty useless in bass cabinets, but that's just me.

Also what about an adjustable crossover point adjustment somewhere on the outside of the box.... Could be a really interesting tone adjustment I'm assuming!

Crossover for what? The only reason to have a crossover would be if you added a tweeter to the cabinet. Even then, there really isn't all that much sound (that you want) above 3k for the tweeter to reproduce. Being able to adjust the crossover frequency would be pretty useless.