Extension Cab for MKIV combo

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jimidle1980
Mark I
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Extension Cab for MKIV combo

Post by jimidle1980 » Mon Oct 12, 2015 7:04 am

My apologies if this has been covered elsewhere! I've recently acquired a MKIV combo, which I love (early A version with EV black shadow speaker). I'm thinking that the sound would be even better with an extension cab (meatier maybe, for want of a better word!). I'm in the UK so mesa cabs are very expensive new and quite rare second hand (plus I've not heard good things about the C90 speaker), but orange cabs seem a bit more competitive. Can someone tell me if pairing the combo EV speaker with a closed back orange 1 x 12 (V30) would lead to good results? Or would you recommend something else?

Thanks!

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Markedman
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Re: Extension Cab for MKIV combo

Post by Markedman » Mon Oct 12, 2015 7:38 am

To me, the more speakers, the better the sound. A 4x12 cabinet with that amp is pure heaven but an extension speaker in a closed back cabinet will definitely give you a thicker sound. I also hated the way the C90 sounded when I had a IV and switched to a EV speaker. I pair my 1X12 open back cab with a theile 1X12 cabinet which works brilliantly.
JP2C, Mark llC++ DG, Mark IV-A/B.

jimidle1980
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Re: Extension Cab for MKIV combo

Post by jimidle1980 » Mon Oct 12, 2015 7:48 am

OK cool thanks :-) So if I purchase the v30 orange cab, please can you give me some advice on how I would connect the extension cab (the orange is a 16 ohm cab)? Which speaker output (in terms of ohms) should I use? And would the EV speaker in the combo need to remain connected to the 8 ohm output? I'm guessing the fact that the v30 is only rated at 60w doesn't matter if there are 2 speakers connected, right?

Thanks a lot!

MrMarkIII
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Re: Extension Cab for MKIV combo

Post by MrMarkIII » Mon Oct 12, 2015 7:25 pm

OK, couple things.
First, you have one 16 ohm speaker and one 8 ohm speaker. On a Mark IV, you're going to want to hook each speaker up to each of the two "4 ohm" speaker out jacks. These are designed to hook up two 8 ohm speakers (or two 8 ohm cabs). Normally, you would un-plug the internal combo speaker (in your case, the EV), and re-plug it into one of the "4 ohm" jacks, and plug an 8 ohm extension cab into the other "4 ohm" jack. You would then leave the "8 ohm" jack empty. (Please don't be tempted to experiment with this empty speaker jack until you learn a bit more about speaker impedances and how to avoid blowing up your amp by going too low in speaker output impedance.)
Ahem.
Unfortunately, with two different speaker impedances (8 & 16 ohms), what happens is the lower impedance is going to get more power, because it has lower resistance.

To wit: One 8 ohm (A) and one 16 ohm (B) in parallel equals:
Amp output = 85 watts
Total Impedance = 5.33 Ω
Speaker A Power = 56.66 Watts (into 8 ohms)
Speaker B Power = 28.33 Watts (into 16 ohms)

The bit about "Total Impedance" is rather important. You don't want to go below 2 ohms total, so on this issue you would be OK, as you are between 8 ohms (ideal) and 4 ohms (a 100% mis-match, the maximum allowable).

You won't break anything doing this, so try it out and find out if the changes to the sound suit you. Report your findings here. We'll wait...

My two cents worth is, find a Thiele with a C90. Put the C90 in the combo, and the EV in the cab. Enjoy.

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Markedman
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Re: Extension Cab for MKIV combo

Post by Markedman » Mon Oct 12, 2015 7:33 pm

I would use the two 4 ohm outputs for the cabinets. You could use the 8 ohm output for the 16 ohm cabinet and plug in the 8 ohm cabinet into the 4 ohm output without any harm to your amp or tubes, you may prefer that tone, it's slightly different. The worst way to run it would be to plug the 8 ohm cabinet into the 8 ohm output and the 16 ohm cabinet into the 4 ohm output. That won't hurt your amp but you will overheat the tubes therefore shortening their lifespan considerably.
JP2C, Mark llC++ DG, Mark IV-A/B.

gts
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Re: Extension Cab for MKIV combo

Post by gts » Tue Oct 13, 2015 1:02 pm

IMHO I don't think the V30 is going to do match up well with an EV.
In fact it'll likely get overpowered by the EV due to how efficient the EV is versus the V30.
In general I've never like V30's with a Mark series amp. (Others may have a more generous view)

Your best bet would be to pair the combo with an EV loaded Thiele.

jimidle1980
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Re: Extension Cab for MKIV combo

Post by jimidle1980 » Wed Oct 14, 2015 7:48 am

Thanks guys...I think I'm gonna hold out for a used Thiele cab.

sduck
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Re: Extension Cab for MKIV combo

Post by sduck » Wed Oct 14, 2015 10:29 pm

jimidle1980 wrote:Thanks guys...I think I'm gonna hold out for a used Thiele cab.
This is your best option - I have one, and it's a killer combination.

HBob
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Re: Extension Cab for MKIV combo

Post by HBob » Fri Oct 16, 2015 8:31 am

I have a MK IV combo with the EV and run an old Sovtek 4x12 pine cabinet with Eminence "V30" style speakers in it. Sounds really great to me. A lot better than just the EV.

jimidle1980
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Re: Extension Cab for MKIV combo

Post by jimidle1980 » Wed Oct 28, 2015 7:37 am

Would a 1 x 12 extension cab with open back be a good option (one has come up locally)? Speaker is EVM12L. Or is a closed back recommended? I would be using in conjunction with the combo speaker

gts
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Re: Extension Cab for MKIV combo

Post by gts » Wed Oct 28, 2015 1:01 pm

jimidle1980 wrote:Would a 1 x 12 extension cab with open back be a good option (one has come up locally)? Speaker is EVM12L. Or is a closed back recommended? I would be using in conjunction with the combo speaker
A Thiele would be better to use with the open back combo (or a Thiele in combination with an open back 1x12).

As for the open back 1x12 nearby:
If it's a good deal grab it. Keep the EV12L and sell the empty 1x12.
Get a Thiele and put the EV12L in the Thiele.

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