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30th November 2005, 10:39 PM  #1 
diyAudio Member
Join Date: Nov 2005
Location: Atlanta

Bass Cabinet  little help here
I was given an empty cab Ampeg 4 x10. Currently I run an Ampeg 115 cab out of a 200W Hartke head. I would like to incorporate this new cabinet into the rig. Without going crazy what speakers (brand, wattage, etc) should I get to put into this cab? I am not looking for the best merely something good thats not gonna blow up if I crank it. Thanks for any help.

1st December 2005, 03:22 AM  #2 
diyAudio Member

Of course you can't go wrong with EV or JBL, but the price may be more than what you want to pay. There are plenty of other speakers out there that will do a good job for a reasonable price.
I've had good luck with Eminence and Jensen. Here are some places to look: http://www.usspeaker.com/ http://www.pyleaudio.com/ http://www.partsexpress.com/ http://www.newsensor.com/
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How do I put the smoke back in this thing? 
1st December 2005, 06:30 AM  #3 
diyAudio Member
Join Date: Nov 2005
Location: Atlanta

Thanks Brion. I was more curious about wattages and what not. When I took the cab I was like , I'll just throw some speakers in there...it doesn't work like that though as I am figuring out. But what I am guessing is that if I throw 4 speakers rated for 75W per, that will give me a 300W cab something that the little 200W head can't blow up right?
I guess what I am really looking at is  with a 200W head powering 1 15 speaker if I throw this 4x10 in the mix whats the least I go and still sound good. I don't need a 300W cab if only 100W is going to it right? I just dont understand how this stuff works. 
1st December 2005, 08:46 AM  #4  
diyAudio Member
Join Date: Jul 2005
Location: North Derbyshire

Quote:
Yes, that's the way it works!. 75W per driver is probably about as low as you will get, modern speakers are more likely to be rated at 100W upwards. For guitar use, there are a number of 'reissued' older spec guitar speakers, but these never look like good value to me?. Quote:
If your amp is rated at 200W into 4 ohms, and your existing speaker is 8 ohms, then you currently get 100W to the 15 inch. If you make your 4x10 8 ohm as well, the amp will provide that 100W as well  giving you a total of 200W  and a LOT more volume, because you're pumping a LOT more air!. If your existing speaker is 4 ohm, and the amp is rated at 4 ohms, you can't add the other speaker to it.
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Nigel Goodwin 

1st December 2005, 09:20 AM  #5 
diyAudio Member

speaker wiring 101
I thought I would try and get my 2 cents in. First, find out more about your amp. If it is rated at 200 watts RMS at 4 ohms, it should put out about 100 watts at 8 ohms, as the other fellow suggested. Nowadays most decent solid state bass amps will also push a 2 ohm load. If this is the case with your amp then you might have plenty of power to boot.
I am guessing your single 15 cabinet is probably an 8 ohm load unit. If you purchase 4 10" bass speakers you want to keep in mind how you will wire them all together. Because the wiring method results directly to the impedence and power handling capacity of the cabinet as a single unit. Lets just leave out the single 15" cabinet for now, and talk about the 4 10" speakers. If you get 4  10" 100 watt RMS handling capacity speakers and they are all 8 ohms each, there is two ways you can wire them together, with two very different results. If you wire them all in parallel, in other words, all the positive terminals together and all the negatives terminals together, then you will have a total impedence of 2 ohms. The plus side of this is that, you have tremendous power handling capacity equal to 400 watts RMS, but you will need more power to drive the speakers. If you wire the 4  10 " speakers in series parallel, then you will have a power handling capacity of about 200 watts RMS, but I think that the overall efficiency might be better. If you wire them in series parallel to get a total cabinet impedence of 8 ohms, and your single 15 cabinet is also 8 ohms, then when you plug in both cabinets to the amp, ( assuming the speaker jacks are wired in parallel on the back of the amp ) the total speaker impedence load that the amp will see is 4 ohms. And I am confident that you amp can drive a 4 ohm load. If you wire the 4  10" cabinet in parallel, and the cabinet impedence is only 2 ohms, then I would not recommend that you use both cabinets at the same time. Because the amp will not like to see a 2 ohm load in parallel with an 8 ohm load. Things might get a little funky there. Now, if your single 15" cabinet is only a 4 ohm load, and you can find 4  10" bass speakers that are all 16 ohms each, then this would happen. You could wire the 4  10" speakers in parallel for a total cabinet impedence of 4 ohms. When you plug in both cabinets to the amp, assuming that the speaker output jacks are wired in parallel, then the amp would see a 2 ohm load. And you can look in the owners manual of your amp and it will tell you if it has a power rating at 2 ohms. If it DOES have a power rating at 2 ohms, then it is safe to drive a 2 ohm load, whether it is a single 2 0hm load cabinet, or two 4 ohm cabinets plugged into the back of the amp. Be sure and take a look at the efficiency of the speakers that you are interested in buying. You want to get the most efficient speaker for the money that you can afford. Regardless of voice coil size, magnet weight, and power handling capacity, the efficiency is quite important. www.partsexpress.com might have some decent speakers as well. Aluminum cones will give you a brighter sound and can go just as deep as paper composite cone drivers. I have not seen aluminum cone bass speakers on the market for a while now. I might suggest to go to www.google.com , and type in something like, loudspeaker wiring diagrams, and it should give you a bunch of good info. 
1st December 2005, 03:02 PM  #6  
diyAudio Member
Join Date: Jul 2005
Location: North Derbyshire

Re: speaker wiring 101
Quote:
What it DOES affect is the power from a specific amplifier, basically (and assuming no losses) an amplifier that can put 100W into 8 ohms, will give 200W into 4 ohms, or 400W into 2 ohms, or 50W into 16 ohms, or 25W into 32 ohms. With four 8 ohm speakers you can wire the cabinet as either 8 ohms (preferable), 2 ohms, or 32 ohms  nothing else!. You also need to check carefully if you're going to wire them all in parallel for 2 ohms, most amps won't handle this, although some modern ones do?  however, even if it's specified to feed 2 ohms, you're stressing the amp a LOT more doing so.
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Nigel Goodwin 

1st December 2005, 03:53 PM  #7 
diyAudio Member
Join Date: Mar 2001
Location: High Point, NC

If it's one of the sealed SVT 4x10, just find some original SVT drivers on Ebay. They show up monthly, usually cheap. NewSensor has 32ohm SVT replacements from ElectroHarmonix. Right now there are 2 sets of 4 used SVT 10s on Ebay. If vented box, Eminence Beta should be fine.

2nd December 2005, 06:07 AM  #8 
diyAudio Member

Upon visiting Hartke Amp's website I have seen that the most current units are rated at 4 and 8 ohms only. So I would not try to run two 4 ohms cabinets with your amp.
With regards to Nigel and his assumption that my ENTIRE paragraph is incorrect, let me say this: 4  8 ohm speakers wired in parallel equals a 2 ohm load. 4  8 ohm speakers wired in series equals a 32 ohm load. 4  8 ohm speakers wired in series  parallel equals an 8 ohm load. I think Nigel and I both agree on the above statements. It is the power handling capabilities of each wiring method that Nigel and I differ to agree upon. If all the speakers are rated at 100 watts RMS each, he says that all three wiring methods will handle 400 watts RMS each. I agree that the parallel configuration will handle 400 watts RMS. Lets look at the series configuration now. We are going to take 400 Watts RMS and run it into that setup. As you know that first speaker is connected directly to the hot output of the amp and here comes a 400 watt RMS signal to the hot terminal of that speaker, and it is rated at only 100 watts RMS. Get my drift ? And same with the series parallel configuration. Those first two speakers that are capable of handling 200 watts RMS because their hot terminals are in parallel, are going to get a 400 watt RMS blast to them. But the parallel configuration has all four hot terminals of the speakers wired together. And each speaker is rated at 100 watts RMS, so at least in my mind can handle the 400 watt signal. I will admit I am old school, having built the bulk of my guitar cabinets when JBL used real ALNICO for their magnets. And most of my learning came from JBL manuals on speaker wiring and cabinet design and construction. So where am I wrong? Perhaps Nigel can explain with the correct maths so I can understand about this power handling thing. Nigel, can you show me the correct maths to prove that 4  100 watt RMS speakers wired in series will handle 400 watts RMS without melting the first speaker ? I am in Zhengzhou, Henan Province, China. Now I am going to kick back and enjoy a nice cup of premium organic green tea and wait for your reply. 
2nd December 2005, 08:59 AM  #9  
diyAudio Member
Join Date: Jul 2005
Location: North Derbyshire

Quote:
The maths is simple, for a start consider the speakers as 8 ohm resistors in series parallel. In this configuration each speaker has half the voltage across it (because it's in series with an identical 8 ohm speaker). Each pair of series speakers also has half the current through it, because the two series pairs are in parallel. To calculate power you use W=VxV/R, to calculate voltage you rearrange the formula as V = Squareroot(WxR) so for 400W and 8 ohms you get 56.57V. With the two speakers in series each speaker will get half of that voltage, that is 28.285V. So applying VxV/R we get 100W in each speaker. You can do exactly the same calculations using the current as well, it's a VERY simple electrical calculation (not even electronic).
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Nigel Goodwin 

2nd December 2005, 12:10 PM  #10 
diyAudio Member

Nigel. Thanks for the explanation regarding the series parallel wiring configuration. But I was asking about the wiring of the series configuration.
In my simple mind ( like I said before, I am old school ) I can understand how four resistors wired in parallel will handle four times as much power. And the overall impedence is 25 % of one resistor. But if you have four identical value resistors in series ( not series parallel ), the first resistor sees the brunt of the wattage of the incoming signal. I have always thought that when 4 identical speakers ( or resistors ) are wired in series, the impedence is four times that of one speaker, but the power handling capacity ( maximum wattage input ) that it will handle is equal to only one speaker. Can you show me the maths to support your theory that 4 identical speakers wired in SERIES will handle the same amount of power as 4 identical speakers wired in parallel ? 
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