Hi Joseph,

Mixing two cabs like that is a no-no for a start. You shouldn't mix two different cab types operating in the same pass band.

Think of an aeroplane trying to fly with two 100 horsepower engines on one wing and a jet engine on the other - that's what you're doing with your combination.

Yes, you see examples of 210 over 115 on the net and sometimes even the manufacturer's brochures give you the idea you can do that, but it doesn't mean to say it's right. There is more info on this subject to be found on either www.billfitzmaurice.info/forum or http://greenboy.us/forum where you can ask questions like you have here.

As far as cutting the wiring in your amp is concerned, I'd get professional advice from a electronic technician beforehand if I were you. Grounding of electricity is not something you want to experiement with or take advice from amateurs off the net.

Sorry if I come across a bit condescending but you did ask for help - it just isn't the sort of answer you might have expected.

PM me if you need to know more

Mo

Mo, I appreciate the reply. I am still a little confused. I thought that as long as they were both 8 ohm cabinets, it was okay. Are you saying that I should either have two, 2x10's or two 1x15's, but not one 2x10 and one 1x15?
Thanks, Joe

Mo is correct, to a point. It has been my experience of bass playing for 45 years that it is perfectly ok to mix and match speaker cabinets. The MAIN thing to watch are the ohms. Two (2) 8 ohm cabs will result in a four (4) ohm resistance across the circuit. If they are wired in parallel that is, which the speaker outputs on the back of amplifiers are, regardless of if they are Speak-ons or 1/4". Also it will not matter if you run both speakers from the head or one from the head the other from the first speaker. Wattage is another consideration. In parallel, the wattage the speakers receive from the amp will be divided by the number of speaker cabs, then each cab will recieve that amount. So, a 400 watt cab in parallel with a 100 watt cab equals 500 watts, but here is another aspect that I think Bo may have been alluding to: In the example I gave, each speaker is handling roughly 250 watts - not good for the 100 watt cab, provided the amp is pushing 500 watts. In the same example, you would want to keep the amp at around 200 watts to prevent damage to the 100 watt cab. Trust me, I have blown my fair share of speakers before this was explained to me by the guy that invented Bruce amps AND the guy that made Emrad amps. To make my point about mixing speaker cab sizes, think about all of the cabs on the market that contain different size speakers inside them, which for bass is nearly ALL of them when you take into account the tweeter or horn as well as the bass drivers.

One more thing - the purpose of Speak-on plugs has nothing to do with hum. They are solely for two (2) purposes: 1. Provide a more secure connection and 2. (most importantly) Get you to spend more money

And lastly, Mo is EXACTLY correct in that your amp grounding problem should only be repaired and/or modified by a professional. You could destroy your amp, all your speakers, and even kill yourself! Not joking here. Look it up - many players have been electrocuted while playing their guitars and basses. The #1 cause? Bad grounding, and that doesn't even take into account getting electrocuted by the charge built up in the capacitors in the amp that can discharge into YOU with one tiny mistake!

Hope this helps...

-Gar

Gar,
I've traditionally run a 4X10 on top of a 1X15 (8 ohms each) forever, and never of the same manufacturer. They sounded fine, looked eclectically cool, and produced a bunch of sound (that I only ever really needed maybe 10 times total). But then, it seemed that when I ran 2 4X10s of the same design, it just seemed, I dunno, fuller. Like maybe I had some odd interference waves at work when I used mismatched cab designs. I think that's what Mo is talking about. Thoughts?

absolutely. There are, as I am sure Mo will agree, some things to take into account. First and foremost is phasing. If the cabs are out of phase, they will tend to cancel each other out. Another is throw. Let's discuss the 3 main types of cab designs. First is called acoustic suspension. This is a sealed cab, no ports. Second, and usually most efficient, it called bass reflex, or ported design. Most bass cabs are this type. These are the cabs that are sealed but have one or more ports, usually in front. Lastly is the folded horn design. The are the cabs the (usually) you cannot see the driver. Some you can see the driver, and they usually have a large square opening beneith the speaker. Ok, each of these cabs will differ in efficiency, decibel to input ratio, and throw. Throw is basically out far out front (or behind) the cab the sound waves come together to produce the best sound, tones, and volume. The throw of cabs typically depends a lot on the design, acoustic suspension being the shortest, bass reflex being next, and folded horn being the longest throw. Throw also has a lot to do with the size and design of the actual driver. A 15" usually has a greater throw than a 10" driver, PLUS two 15" drivers from different manufacturers can have different throws. This is because of variances in voice coil diameter, cone material and thickness, efficiency, even frame design and magnet weight/strength. Anyway, this is why at the very least the elements inside a single cab should be matched up.

So, why does are rig sound "fuller" when using two of the same cabs? Because the throw is the same for both cabs, therefore wherever you stand, you are getting roughly twice the sound pressure level. This is why Mo says it is a no no to mix and match cabs. And I completely agree.

But...all this is assuming a few things. 1: You intend to always stack your rig in the Marshall fashion, and 2: you do not own a decibel meter.

When I was actually performing on a regular basis, I would first "test the room" with the meter and an output tone of A 440. I would generally set my 18" folded horns (2) as far back as possible. These provide a deep bass (very deep) that would rattle beers off table and blow out a match at 10 feet. I would move my sealed Altecs, 2-15's in each x 2 cabs, about halfway up the stage on either side facing more in than towards the audiance. Lastly I would place my single cab with 2-15's, a bass reflex design, pretty much right behind me pointed straight out. This setup varied with the actual room. Then of course there was whatever the soundman did through the PA.

Anyway, the point is this: It ain't carved in stone. Depending on the sound you want, you might find yourself mixing up any number of cabs. The simple solution for solid clear bass, follow Mo's advice and do NOT mix and match. To taylor your sound, experiment. If you look at my AB homepage you can see part of the rig I used to run through, manely one of the Altec stacks.

....Are you saying that I should either have two, 2x10's or two 1x15's, but not one 2x10 and one 1x15?... Yep - precisely, so long as the cabs are identical design with identical drivers.

Again, I urge you frequent the forums I have referred you to so you will see it's just not my personal opinion (as some people here may consider I am biased because I build speaker cabinets ) but it is fact for good reason. I have also given you two forums so that there is no bias. Ask your question in either one of them or both..

If you were to put 2 identical 210s together for example alongside a 210 and a 115, you'd certainly tell the difference when compared. It's not as easy gauging the difference if they're not side by side at the same moment/venue to compare which is why some people say 210 x 115 is OK.

I had a 115 cab many years ago and a friend of mine was lucky to get the Aguilar agency. He brought a 210 and a 210 around 'to compliment my 115' and offered me a very special deal. For some reason it just sounded lousy when I mixed the cabs but never understood why at the time. It was only after research ( which lead me to cab building ) that I found out the do's and don't based on audio science and research rather than guesswork, following all the other sheep or marketing ploys.

Good luck

Whoops - meant "my friend brought a 210 and a 212"

Mo! You're the cab master! So... I just bought a MarkBass 1X12 combo. Lots of power, but I want to push more air in the larger clubs -so I'm looking for an extra cab to stack. I was originally looking for a 4X10 to stick underneath it, but am reminded of our discussions regarding same. What are my choices? A single 1X12 cab? A 2X12? Several large fake cabs so it at least LOOKS like I'm a bass god? As an aside, I am mightily impressed with this little bitty combo.

You could add another 112 cab exactly the same, and put it on top. Provided the design parameters are the same ( exactly twice the size and same two drivers ) you could add a 212 BUT your amp would have to be capable of handling 2 ohms and if you were driving that real hard ( that would be awfully loud ) then that would not be such a great idea.

Depending on the SPL charts ( if the manufacturer wold ever provide you one ) then the 410 without the 212 may be a better solution.

As mentioned to the OP, it pays to run the options side by side to A/B properly and then you can really tell the difference.

Hope that helps PM me if you need more info.

Thanks to all of you. I appreciate your help. I will read the other postings. One last question then, If the head puts out 450 watts @ 4 ohms, would it be better (and less expensive) to find a single 4 ohm cabinet, or get two matching 8 ohm cabinets?

Thanks, Joe

If you have a cab of 8ohms, you're better getting another exact same cab of 8 ohms and stack vertically. Run the cabs parallel and it's 4 ohms for the amp.

Remember, you get extra dB purely by coupling the two cabs ( ie putting them on top of each other )

If your cab is already 4 ohms, then get another cab of 4 ohms and run them in series ( 8 ohms ) - the extra dB of the coupling still applies.

Getting the most watt outs of your amp is a complete misnomer and don't get sucked into that practice. Volume is mostly about displacement and cabs properly designed for their drivers ( speakers ) Again, if you're interested in the right way to do things, I urge you to study more at one or both of the forums I have recommended.

Mo

Cheers

Mo, This has been most enlightening! The science of sound! I often wondered why an old 70's tall cab with one 15 ((not mine but I played through it a few times) probably 4 feet tall) with a 150 watt built in head could throw monster bass sound. The cab was built for it - a bear to move but it was sculpted to make bass sound. And I am struggling with 450 watts and a 15 and 2 10's. To be direct, to get the sound that I want, and what I have had in the past, I am going to start over. I've had "said" rig for about 3 years now and have never been happy with it. I am going to sell it or trade it in and get the the right pieces from the get-go. With your advice and input I know I will know what to look for with future gear.
Mucho apreciado
Joe

buy an ampeg a tube amp and solve all your problems.