Device to increase impedence - "fry your chicken, not your amp"

[Joe Z]

As you know there have been tons of threads on impedence, can I add a cabinet, etc. I'm currently running two Ampeg 410hlf's (4 ohm, each) with a Markbass 800 tube. It's rated for 4 ohms. Obviously, if you "daisy chain" them or use both outputs on the Markbass, you're at 2 ohms.

I played a gig that way without any problem (and with fingers crossed and understanding the risks and with a backup Markbass cmp 102) UNTIL (between songs) I happened to slap down with my right hand on the strings, near the bridge with sufficient pressure to put a string or two in contact with the pickups (which, admittedly, I keep maybe a touch high). There was a click - not terribly loud, and I didn't think anything of it, until a few seconds later when the next song started....

That song ended within 2 bars as my amp had cut out. I switched off the amp, waited about 5 seconds, turned it on, restarted the song and finished the gig without incident.

I knew the risks were just too high, at that point. The volume of the click was nothing significant, but apparently enough of a draw on the amp to make it cut out.

So, I considered going back to my Ampeg pro 4, getting one 810, getting another 800 tube and running them together, and on and on. Problem is, I really like the Markbass, and I really like the hlf410's, and I really like paying the mortgage.

So, I was talking to one of my oldest friends who I used to play with in the 70's and 80's - he's been running an electronics company for years and used to do all our tech work, build amps, etc. He put together a box (a little bigger than a pack of cigarettes) with a one foot cable coming out with a speakon connector that goes into the amp and two speakon inputs for speakers. It puts the speakers in SERIES and (in my case) doubles the impedence - 8 ohms.

Obviously, you must have the amp off when you connect or disconnect and you must always have BOTH speakers attached and EACH must be able to handle the amp's power. Also, if any speaker goes out they all go - like old Christmas lights.

He sent me the "prototype" and I hooked it up. I expected to notice less power, less volume because I'm running 8, no longer 2 ohms. I did an a/b comparison (took a few seconds to install/take out the unit) but I could not really sense any loss. Max volume seemed the same, tone etc all no change.

The upside, as I see it, is that I know I'm NOT pushing my amp, I know my speakers are in phase, and I know I'm less likely to crap out at a real bad time. It gives me an option, with whatever speakers I have, to increase my impedence.

So...fry your chicken, NOT your amp!!

regards....Joe

[T-Bird]

Hi.

What a relief, I thought this was going to be the umpteenth dummy-load/matching-transformer thread once again .

Series cables and boxes have been there for ages, too bad people don't consider them as an option beacause of the great "loss of power and volume".

Glad to see that You tried it out and found out what countless others have discovered earlier, the tone/power/volume loss is in their imagination.

Regards
Sam

[billfitzmaurice]

Originally Posted by T-Bird

countless others have discovered earlier, the tone/power/volume loss is in their imagination.

Countless maybe, but still vastly outnumbered by the 'I need to get all the watts out of my amp' crowd.

[Jim C]

Originally Posted by T-Bird

Hi.

Series cables and boxes have been there for ages, too bad people don't consider them as an option beacause of the great "loss of power and volume".

I wonder if this is more unique to Europe Sam as I've been a player for over 30 years and have never seen a series box or cable being sold for speaker hookup up before

Great idea for this application

[KJung]

Series can work nicely in a case like this where you have kind of a mismatch between the cabs you own and the head you purchased.

However, as with most things, 'it depends'. With two big 410's and a high powered amp, running at 8ohms will still give you a nice wallup of power, and all that cone area will of course give you quite a bit of volume.

However, with low sensitivity cabs and/or a lower powered head, this solution can definitely be a compromise.

I would actually suggest comparing your 'series' stack at 250 watts per cab with one of those big 4ohm 410's with the full 800 watts going into it. It won't sound quite as big (cone area typically trumps wattage), but my guess is, on the gig when are are wumping, one 4ohm 410 with a wump of power that it can actually use (thermally and most likely mechanically) will IMO and IME get you reasonably close to your massive 'series' rig. You are carrying a LOT of extra weight around for most likely not much more benefit than running one of the cabs with higher wattage.

It all depends. Those who say wattage doesn't matter are just as wrong as those who say more watts is always better

The bigger question is why you would have purchased a head rated to run safely at no lower than 4ohms when you have two large 40hm cabs. There are many heads that could deal with 2ohms, like the Genz Shuttle 12, with two separate power amps, the Carvin B2000 (safe at 2ohms), etc.

[BassmanPaul]

i agree Ken, but this is what happens a lot. Someone will buy an amp without considering what his needs actually are with the speakers he owns.

OP you are VERY lucky that your amp survived the abuse you subjected it to. Others have tried the same thing to their cost. Series boxes are simple to make and use. The problems that can occur is that the crossovers in each cab can react with each other with interesting results especially if the cabs have different manufacturers.

[Joe Z]

Good point about the "why I got the 4 ohm amp in the first place"...Mostly, I just really like the Markbass, it's weight, the sound - a little different from the CMP102 I have, but still good. I proceeded on the assumption that without pushing out the power (keeping volume low) I could manage the risk. That may be true, but I think I noticed the practical application of how little volume change you actually percieve from a given change in power, or actually the inverse of that, which is thinking I'm NOT pulling too much power because it doesn't sound alot louder - hence the meltdown.

GAS was also probably a significant motivating factor.

I have run just the one cab and it's pretty close to running both....and after a few gigs humping both cabs...well, we'll see.

Thanks guys, for the thoughtfull comments.

Joe

[KJung]

Originally Posted by Joe Z

I have run just the one cab and it's pretty close to running both....and after a few gigs humping both cabs...well, we'll see.

You might end up with a 'win win' there. Great head and that particular 410 can handle a wump of power, both thermally and mechanically IMO. That 800 or so watts into that big box at 4ohms must be glorious, and the rather bright and aggressive upper mid voicing of the 800 series Markbass heads probably is a nice yin and yang to the rather dark voicing (IMO) of that particular cab.

[T-Bird]

Hi.

Originally Posted by billfitzmaurice

Countless maybe, but still vastly outnumbered by the 'I need to get all the watts out of my amp' crowd.

Unfortunately You're absolutely correct with that statement.

Originally Posted by Jim C

I wonder if this is more unique to Europe Sam as I've been a player for over 30 years and have never seen a series box or cable being sold for speaker hookup up before

You could be correct about that Jim.

OTOH, all the ones I have seen for sale has been done by shop owners or DIYers, way too easy and inexpensive to manufacture industrially.

The first one I did was when I wanted to run 2 8Ohm cabs with a tube amp that had only 8&16Ohm taps. That was in the early 90's. Since the tubes (and transistors/Fet's) and the amps were pretty expensive, we tried to match the impedances as closely as possible even back then.

Regards
Sam

[Petebass]

Originally Posted by Joe Z

So, I was talking to one of my oldest friends who I used to play with in the 70's and 80's - he's been running an electronics company for years and used to do all our tech work, build amps, etc. He put together a box (a little bigger than a pack of cigarettes) with a one foot cable coming out with a speakon connector that goes into the amp and two speakon inputs for speakers. It puts the speakers in SERIES and (in my case) doubles the impedence - 8 ohms.

If anyone is looking for a commercially made version of this box, check out the speakermate. I bought one years ago and it's a handy little addition to my bag of tricks.

http://www.rainbowmusicshop.com/sher...dels_wide.html