Webb Amp question

Darrell Owens · Post by **Darrell Owens** » 14 Nov 2006 9:50 am

I have a Webb amp and the Webb ext. cabinet. The amp has a 4 ohm JBL and the ext cabinet has an 8 ohm JBL. I just noticed the difference in the ohm ratings. Does that create an unbalanced load for the amp when the ext cab is plugged in? If so, what should I do? replace the amp speaker with an 8 ohm JBL or replace the ext cab with a 4 ohm JBL? or does this amp even care?

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Darrell Owens
www.darrellowens.com

Kevin Hatton · Post by **Kevin Hatton** » 14 Nov 2006 10:00 am

Webb amps accept 2,4, or 8 ohm loads. The only difference you will notice is slightly less volume.

Jim Sliff · Post by **Jim Sliff** » 14 Nov 2006 2:08 pm

Are you unhooking the internal speaker to hook up the external cab? If so, I agree with Kevin.

If you're combining the two you're creating an odd load, with one speaker pulling most of the power. Not a good idea for tone - it's going to sound pretty thin.

David Higginbotham · Post by **David Higginbotham** » 14 Nov 2006 2:09 pm

Kevin is correct. The 4 ohm speaker will be a bit louder than the 8 ohm, but no harm will come to the amp. That is exactly what Tommy White uses in his Webb. Twelve inch 8 ohm JBL in the amp and a 4 ohm JBL in the extension.

I would however caution against any lower on the impedance. You can go to another 8 ohm if you wish but not another 4 ohm even tho the Webb says it can operate at a 2 ohm load. That creates a great demand on the amp!
Dave [This message was edited by David Higginbotham on 14 November 2006 at 02:13 PM.]

Darrell Owens · Post by **Darrell Owens** » 14 Nov 2006 6:24 pm

Thanks for the help.

The 4 ohm speaker is in the amp and the 8 ohm speaker is in the ext cabinet. That is the way it came from Webb. I do have another 8 ohm speaker that I could replace the amp speaker. Is that recommended, or should I just leave it alone?

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Darrell Owens www.darrellowens.com [This message was edited by Darrell Owens on 14 November 2006 at 06:26 PM.]

Jim Sliff · Post by **Jim Sliff** » 14 Nov 2006 7:23 pm

I'd replace it.

When pairing speakers, whether series or parallel, it's always better to use the same impedance. Mixing a 4 and 8 ohm always causes tonal problems, as one speaker is carrying more load and the other is being used inefficiently. There's no reason at all to do it that way, unless the extension jack is using specific taps on the output transformer for a particular impedance different from the internal speaker output. That may be the case with the Webb - I've never seen one or a schematic. But the extension jack should be labeled with a specific requirement.

David Higginbotham · Post by **David Higginbotham** » 14 Nov 2006 7:50 pm

Darrell, with all due respect to Jim for his great advice, I would go by the rule "if it ain't broke, don't fix it."

I know Tommy has no tonal problems and I bought this Webb setup from Tommy himself. It was specially made for him by Jimmy Webb with 12 inch speakers rather than 15's. It had the 8 ohm in the amp and 4 ohm in the extension. I did eventually change the speakers in both to 8 ohms only because I preferred the sound of 1203 BW's over the JBL E-120's. I eventually sold the amp & extension and put the JBL's back in.
Dave

Jim Sliff · Post by **Jim Sliff** » 15 Nov 2006 9:26 pm

David, with all due respect - it IS broke that way...he doesn't say how it sounds, but I'd bet a buck it would sound better with the right speaker load, assuming decent speakers were used.

Mike Fried · Post by **Mike Fried** » 15 Nov 2006 11:13 pm

With all due respect to everyone, it's not necessarily "broke" - there are plenty of instances of using two (or more) different impedance loads on one power amp to achieve different volume levels among different speakers, and it sounds to me like in this case it was done "on purpose" by the amp's builder/designer. It could very well be that Tommy wanted a lower volume level from the "near" speaker as his monitor, and more output from the extension cabinet that's not right in his ear. As long as the power amp's minimum impedance load isn't breached, no harm is done, and if it sounds the way the user wants it to sound, leave it alone.[This message was edited by Mike Fried on 15 November 2006 at 11:16 PM.]

Jim Sliff · Post by **Jim Sliff** » 16 Nov 2006 5:33 am

Mike, it doesn't just affect volume, it screws up the tone coming from both speakers. There is all kinds of complicated data about this, but simply it's a really bad electronics practice and will do NOTHING positive for the sound. It *will* sound better with the right impedance; and if volume in one is a problem there are a myriad of ways of handling that, as any sound tech would know.

In this case, the user doesn't know that it will sound better done right, so he likely thinks it sounds like how it's supposed to. But it WILL sound better with the right loads.

(edited for non-content typo)[This message was edited by Jim Sliff on 16 November 2006 at 05:38 PM.]

Darrell Owens · Post by **Darrell Owens** » 16 Nov 2006 11:41 am

I appreciate the input from everyone.

I have always tried to keep the ohm ratings balanced when adding extra speakers to an amp. I was surprised when I saw the Webb had a 4 ohm speaker and an 8 ohm ext cab. I don't know if it was a mis-match, or if there was a reason Mr Webb loaded them this way.

There is a slight volume difference in the two speakers, but there is no audible change of tone with or without the ext speaker. At least, I cannot hear it, and I have been accused of having "dog ears".

It sounds like the preferred "fix" is to change out the 4 ohm speaker in the amp to an 8 ohm to match the ext cabinet. I may give that a try just to see if it makes a difference.

Darrell Owens

Mike Fried · Post by **Mike Fried** » 16 Nov 2006 3:49 pm

Jim, are you saying that the amp's builder/designer (Jim Webb) didn't know what he was doing when he put this rig together??? I'm not making up my "opinion" on this matter - I do have many years of profesional experience as a fulltime tech (at Matchless Amps for one) and as a fulltime player, and I can assure you there are plenty of designers out there that know more than either of us who have done exactly what was done here. Running two otherwise identical speakers of different impedances out of the same source will do nothing more than provide a different SPL from each, especially if they're in two different enclosures. If you can provide data to the contrary, I'd like to see it.[This message was edited by Mike Fried on 16 November 2006 at 03:50 PM.][This message was edited by Mike Fried on 16 November 2006 at 03:52 PM.]

Mike Wheeler · Post by **Mike Wheeler** » 16 Nov 2006 5:00 pm

I agree with Mike. Now, if they are two completely different designed speakers, ie. a JBL and a EV, then yes they will have unmatched sonic qualities. A mix like that might cause a descerning player some various tonal difficulties. But it's not because of the impedances that they'll sound different.

And, yes, I am aware of the tonal and SPL differences between a 12" and 15" JBL, but I believe the mixture of the two JBLs would be very acceptable to almost any steel picker.

Jim Sliff · Post by **Jim Sliff** » 16 Nov 2006 5:59 pm

Mike(s) - I am not going to spend time digging it up, but many references on the subject have ben posted on alt.guitar.amps, ampworkshop, and many forums including the Fender forum with posts by Fender amp folks, including Ritchie Fliegler, and most of the techs who participate in such forums. It's a common question on guitar forums, and the answer is as I have given it.

You can kowtow to Mr. Webb all you want, but he can't chang the laws of electronics. The math is what it is...heck, and I don't even LIKE math!

Mark Sampson didn't design Matchless amps, nor the original Bad Cats, to work with unbalanced loads. Top Hat, Dr. Z., Ken Fischer...you get the sam advice from all corners. Most give very exact specifications for extension speaker impedance, to ensure a match is maintained. Fender stresses the point with the '64 Vibroverb custom because of the modified BF circuit.

An imbalanced load is an imbalanced load, and SPL is NOT the only thing affected. Harmonic content is significantly affected...at least in amps that sound good to start with.

If Webb designed it to be run WITH the extension cabinet mismatched, then the OT is designed for something other than 4 or 8 ohms, and he tweaked the tone circuits to compensate for the loss of bass and midrange hump that WILL end up emanating from the speaker receiving less of a power hit.

And if that's true, then REMOVING the extension cabinet will foul the tone of the remaining speaker, which now is getting a signal meant for something else.

You can't have your cake and eat it too - unless he figured out a way to hit each speaker with the same power and EQ, AND have the same tonal quality exist when the extra one was removed. If he did, I'd like to give him some rocks to squeeze into gold as well.

Without switching parts of the circuit, it is impossible for it to work. It MAY sound OK to some people, and especially with nothing but clean tones. But IF the amp is capable of any decent overdrive tones (always shaky in a SS amp) the tone will go to hell in a handbasket.

Given most steel players play clean all the time, it would not be as noticeable a problem. But it doesn't go away, and you could scope the output to each speaker and see the difference easily.

Darrell Owens · Post by **Darrell Owens** » 16 Nov 2006 7:08 pm

Well, I agree with Jim in that you can't change the math, but after trying various combinations, thre is no way to make this amp sound bad. I tried two identical JBL 8 ohm speakers and the amp sounded great. I tried only the 4 ohm speaker in the amp and that was great, then added the 8 ohm ext with the amp and that was the best sound.

The two 8 ohm JBLs were K-130s and they were a little darker than the E-130's

The 4 ohm JBL E-130 in the amp alone was brighter and perhaps a bit louder.

The 4 ohm E-130 speaker in the amp and the 8 ohm E-130 speaker in the Webb ext cab was really the best sound. I cannot tell whether is was a different sound or just more of it. It didn't seem to change the tone of the amp, just added more depth in the room.

NOw here is another question - Is there a difference in the JBL K-130 and the JBL E-130?

Mike Fried · Post by **Mike Fried** » 16 Nov 2006 7:16 pm

Jim, your entire argument (as well as the content of the message boards you refer to) pertains to amps with an output transformer, which the Webb DOES NOT have. Its output is transistor-coupled, and virtually none of the factors you mention (all of which I'm very aware of) apply. If we were discussing tube amps, you'd have a valid point, but we're not. As for "cowtowing" to Mr. Webb, you betcha I'll defer to the designer of such a successful and superior product - when you design a better SS amp I'll cowtow to you too!

John Macy · Post by **John Macy** » 16 Nov 2006 7:18 pm

My 66 Fender Super Reverb always sounds best to me when one of the 10" speakers is disconnected. I'm sure it is imbalanced, but man, does it sound good. Whenever I hook up the fourth speaker I am always disappointed...

David Higginbotham · Post by **David Higginbotham** » 16 Nov 2006 7:23 pm

Yes, there is a difference in the K's & E's. They have different types of magnets. You can do a search in the electronics section to get the specific details.

Your observations of the difference in sound between the two speakers is very common. The K's will be a little darker and smoother in tone than the E's. The E's I find better for that "old timey" sound. But, they are just too harsh sounding for my personal preference. You can cut glass with them if you turn up the treble.

I just installed a K-130-4 ohm in a Carvin VX-112 tube amp two days ago. Very good sound indeed!

I have had five Webb amps and have tried the E's, K's, & BW 1501's. I find the K's gave the smoothest and best overall sound. One thing for sure about the Webbs, they are hard to beat for the sound!
Dave

Mike Fried · Post by **Mike Fried** » 16 Nov 2006 7:24 pm

Darrell, to answer your JBL question, the K130 has an Alnico magnet and is rated for less power (the exact spec is questionable) than the E130, which has a ceramic magnet. Most people prefer the sound of the K-series speakers, but they are prone to blow with amps rated at more than 100wrms or so. Some people have used 8-ohm K130s with Webbs and big Peaveys, as the 8-ohm load brings the amp's power output down to a safer level for that speaker. The loss of electrical power output is pretty much offset by that speaker's superior effeciency, so little if any actual volume is lost.[This message was edited by Mike Fried on 16 November 2006 at 07:30 PM.]

David Higginbotham · Post by **David Higginbotham** » 16 Nov 2006 7:33 pm

Exactly what Mike said! The power rating on the K series is suppose to be 150 watts & the power rating on the E series is suppose to be 300 watts. Now, as Mike mentioned, these are questionable ratings. He gave the best advice of using the 8 ohm K series. That would bring the 225 watts of the Webb down to about 165 watts or so. But as long as you keep the volume level less than five with a 4 ohm, I think you will ok.
Dave

Tom Bradshaw · Post by **Tom Bradshaw** » 16 Nov 2006 7:48 pm

I received a private email from Darrell, asking for my point of view on his inquiry. I feel that all those who have posted here have a far better grip on this subject than I do (or ever will). My primary source of information about the Webb amps comes from its major designer, George Moore. He has also been responsible for all of the updates on the amp over the years (but there hasn't been many). George is currently a design engineer for the Nady Company. I lured George back to do the final testing of the Webb amps that I will be offering in the coming year. I will share this post with him and will report back what input he offers. George is a very busy fellow and can only provide me with a few hours per week.

I knew Jim Webb for over 30 years. He had no training in electronics. Other than knowing what kind of sound he was after, he learned by quizzing his own technicians. I'm doing the same thing with George as I try to educate myself about amp building. I want to perpetuate the good sound of the Webb, and in any way possible, improve upon it. I feel I'm making progress at that with my current efforts.

My sense concerning this 8- + 4-ohm speaker topic only comes from experience in life: "Likes attract; opposites repel"; "Oil and water don't mix"; etc. So why go out of your way to create a mismatch problem? Why not just use two 4-ohm speakers or two 8-ohm speakers and avoid the potential for problems and electronic conflicts? If you want one speaker to be louder than another, get a technician to engineer a volume regulator for one of them and set that volume to what you want?

I'll try to get an answer from George and post it next week. ...Tom

Jim Sliff · Post by **Jim Sliff** » 16 Nov 2006 7:51 pm

Mike - OK, now THAT makes more sense.

Personally, I wouldn't be too interested in an amp with no OT (which is the heart of amps that have them, and where a lot of the tone/warmth comes from...plus saturation in some cases) - so I can see where the difference would be minimal (there's STILL going to be some - but not enough to really notice, since the amp HAS to be played clean).

When you mentioned a background at Matchless, it was a bit misleading, since the amp you are talking about is obviously a completely different animal.

However, even solid-state amp makers will tell you that mismatches can result in unwanted distortion and loss of power...transformer or no transformer. Those things affect tone. It might not be real noticable...but it's still a technical error.

And Mike - you might notice from Tom's post that Webb wasn't an engineer NOR the amp's designer. Interesting that you are adamantly defending and claiming knowledge of an amp whose "maker" you have wrong. It would appear Webb was the owner - and not on the technical side. ???[This message was edited by Jim Sliff on 16 November 2006 at 08:00 PM.]

Mike Fried · Post by **Mike Fried** » 16 Nov 2006 10:21 pm

Jim, rather than continuing what seems to be a pi$$ing contest over who's right and will get in the last word, I will admit that I did not know who the actual designer of the Webb was, if you will admit it's irrelevant to the facts under discussion.

I am, however, very familiar with the amplifier, having owned a couple of them and serviced a number more. I guess you're entitled to your prejudice against them based on their lack of an OT (have you ever actually played through one? Funny, I own a number of prime BF Fenders and a couple of Matchlesses, and I still think the Webb is a great-sounding steel amp, and I'm hardly alone in that opinion), but whatever hypothetical "problem" may or may not exist with this speaker mismatch won't require throwing money at with a speaker replacement or any other technical "fix". If it sounds good (and I think its owner knows that better than either of us), use it, as there's no harm to be concerned with from that speaker configuration. That, as I recall, was the original question. If Tom finds out something different from its designer re. that question, I will cowtow to whomever, and I will be very, very surprised.

That said, the only concern I'd have in running a Webb under 4 ohms (regardless of whether it's two 4s, an 8 & a 4, or whatever) is heat, as many Webbs do tend to run pretty warm. I'd keep an eye on that if/when driving the amp hard with both speakers, especially in a warm environment. I actually installed 120vac muffin fans (mounted on the inside of the top back panel) in a couple of them that saw a lot of outdoor use with 2 and 4-ohm loads. The issue there isn't really a potential breakdown as much as preserving component life as well as possible.

Mike Wheeler · Post by **Mike Wheeler** » 17 Nov 2006 4:51 am

Of course it makes more sense, the context of the original post was SS, not tubes. Not every post is about tube amps, Jim. They are, in many ways, very different from each other, and advice about one doesn't necessarily apply to the other. The average picker doesn't understand the electronics inside these boxes, so it becomes necessary for techs, like us, to answer questions carefully.

Jim Sliff · Post by **Jim Sliff** » 17 Nov 2006 5:26 am

Mike Wheeler - except it STILL makes a difference, and it's STILL technically not correct. There's more obvious impact in a transformer-coupled circuit, but the transistors also want to see a specific impedance on the other end, and it CAN create distortion and volume loss - how much depends on the design, but there will ALWAYS be SOME.

My point was correct no matter which type it is - it's merely less noticable in some SS circuits when run clean. If you dime that amp and compare a mismatched set with a correctly matched set of speakers, I'd bet there would be at minimum a slight, but noticable, difference in tone.

And no, unfortunately I have not played one. Here in the hotbed of steel (j/k) we don't have stores that stock any steel equipment at all.

The impedance match all depends on how critical your ear is, and how well dialed-in you like your equipment to be. But I don't know of a single other SS amp maker who recommends that practice, either the designer discovered how to do something no one else can do or to his ear it didn't matter.