Tuesday, October 20, 2009

Champion 600 Speaker Upgrade Comparison

I installed four different speakers in my Champion 600 and ran some frequency response sweeps for the sake of comparison.*

What I saw in the graphs pretty much confirmed what I heard in each of them.

First the stock speaker compared to a Jensen Mod:

Champion 600 Stock Speaker vs Jensen Mod

Just as my ear was telling me - the Jensen is a touch more efficient and a touch smoother but they really didn't sound all that different. I found the difference to be hardly worth the upgrade cost.

Here is the Weber alnico with a late breakup cone compared to the stock Champion 600 speaker:

Champion 600 stock speaker vs Weber alnico late break up ribbed cone

Notice that the Weber late breakup alnico is a good bit more efficient than the stock speaker up to about 3K, where it drops off dramatically. This probably accounts for some people experiencing the Weber as dark sounding. What isn't evident from the graph is that in addition to the increased bass response the Weber is more able to handle the bass so it doesn't fart out the way the stock speaker does.

The next graph is interesting. It compares the Weber late break up ribbed cone to the Weber early break up smooth cone:

Weber alnico speaker comparison - late break up ribbed cone vs early break up smooth cone

They're pretty similar in the bass but in the upper mids and treble they're very different. So in addition to the breakup characteristics they have quite different upper range response. Personally I prefer the smooth cone sound - it sounds a bit more vintage to my ear. The ribbed cone sounds tighter and more modern. They both sound great though and are both worth the upgrade.

Here is the smooth cone Weber compared to the stock speaker:

Weber smooth cone early break up alnico compared to the Fender Champion 600 stock speaker

It look much more like the original in the treble response. Kind of like the stock speaker with increased bass and mids (and better bass handling).

Here's plots for all four speakers on the same graph - just for ease of comparison:

Frequency response of all four Champion 600 speakers

Incidentally, I found that the stock grill cloth really does flap around at higher volumes making some nasty farting and flapping along with the low notes. I cut mine out when I cut down the baffleboard for the Weber speaker installation and am looking for something to replace it with.

* These graphs are for the sake of comparison between the speakers. Since they aren't anechoic chamber tests the graphs include the room effects so don't pay to much attention to each tiny peak and dip. They don't show isolated speaker response but work fine to illustrate how the speakers differ from each other under the same room conditions.


MichaelO said...

Try this grill cloth:

I put it in mine and it looks like God and Leo intended!

I have the Weber smooth cone in it and it sounds just the way it appears in your analysis. I put a NOS Hytron power tube and a reissue Tung Sol 12ax7, and it really sings. Appreciate your postings here. Really good stuff!

akavalve said...

Great. Thanks for the pointer.

Nice to have an EE around to keep me honest :)

Anonymous said...

Nice. what software are you using to plot your freq. resp. graphs?

akavalve said...

I use Adobe Audition's FFT tool.

I generated a frequency special frequency sweep with a rate that causes it to graph flat in the FFT. I play that tone through the amp and record with a cheapie omni measurement mic.

I change out the speakers without moving the mic or the amp cab so that the frequency anomalies due to the room response / mic placement will be identical between recordings. So even though they're not as accurate individually as they'd be in an anechoic chamber, they should serve well for the sake of comparison.

Anonymous said...

Thanks for the info. Would wou be willing to share more about your test procedure? I'm quite interested in finding a simple way to compare various speakers without being in a lab environment. You know how hard (not to mention expensive) it is to get access to a true anechoic chamber?

What frequency sweeps are you using in audition?

Thanks again!

akavalve said...

Sure. It's not a perfect method, certainly. It's just meant for rough comparison. Here's how I do it:

The sweep tone is one I generated myself. If you do an FFT on it you get a flat line. I'll send you a .wav copy of it if you like.

I play the sweep tone out of my DAW into a Little Labs IBP which I use as a re-amper to get a level more appropriate for an amp input.

I mic the front of the amp with a Behringer ECM 8000 through a Great River MP2NV and record back into Audition.

Then I do a frequency plot on the recorded audio.

There are two drawbacks.

First, the measurements only serve for comparison between speakers in the same situation. Because the room response and amplifier settings are included they reveal differences between speakers more than actual characteristics of individual speakers.

Secondly, you can't change the setup AT ALL between measurements - so unless you have some kind of permanent setup you have to take a group of measurements all in one session. If you decide to add another speaker to the group at a later time you need to run sweeps on all of them again to ensure accurate comparison.

Matt said...

Thanks for sharing your "quick & dirty" method.

For many of the comparisons I'd do, this is more than enough to get a rough picture of what I'm hearing from the speakers.

And sure, I'd really appreciate your sweep as a .wav file if you'd be willing to send it.

Thanks again!

HaYES said...

I'm currently looking at the weber alnicos for upgrades. What's the difference in the amount of break up, distortion in the early and late webers? Where do they start to break up on both the low and high gain channels? I was considering the fully ribbed late speaker but after seeing your charts I don't like the huge drop offs in the highs and am reconsidering. Would you expect the partially ribbed to be somewhat of a balance in terms of frequency response (same general bass, more mids than the early but less drop off in the high frequencies than the late) or is that not how it works? I love your blog, thanks so much and I hope there may be more to come someday.


akavalve said...

I haven't done a close comparison of the two distortion wise, but I think the amp itself breaks up pretty early so no speaker is going to give a whole lot more headroom.

To my ear any difference there might have been in speaker breakup was swamped by the difference in frequency response and the breakup of the amp itself.

I lent the ribbed Weber to a friend recently and he did find it too dark.

Though I haven't had one myself, I believe your instinct is correct regarding the partly ribbed cone.

I find the smooth cone to be a nice match myself.

whatsgoingonhere said...

I really enjoy your blog, and it's got a lot of info that I have been looking for and haven't found. Thanks a lot for showing how to be SAFE around the amps - I've heard some advice from people about how to discharge caps that I never wanted to try because my spidey sense was tingling.

But, I have a question you may be able to answer about speakers. How about a 4x6" cab? I have an ampeg 4x10" for my bass, and I was reading on their site that 4x10 can push more air and support deeper frequencies (I suppose) better than 3x15 and a lot of other combinations you think would be better but aren't (at least that's what it sounded like...?). So, I was wondering, would a 4x6" be able to help improve that bass response and keep a great clarity for something like recording. Maybe you've tried it...?

whatsgoingonhere said...

Sorry, but the speaker question was in reference to the Champ 600 mods, as I've got a champ 600 and want to explore it's possibilities.

Also, do you know a way to have an external speaker output that can allow the inside speaker to operate while the external is plugged in? I would suppose it would be easy to add a jack near the vol knob for an external that can BYPASS the internal speaker.

Also, have you tried any transformer upgrades? I was checking out the weber homepage's offerings of transformers, and they have some that seem they could work out pretty well, and even add extra possibilities for impedance outs. I've heard one person say the reason the amp hum is that the trannies are too close together in the stock amp, but then I've heard about changing to a tranny with a DC filament to reduce hum. I don't completely understand why either option would reduce hum, but perhaps you do. It would be cool to have some extra impedance outs though...

Anonymous said...

Hi aka valve,
I really appreciate your work and have had a lot of fun executing many of your mods. I have put a 8" inch Jensen MOD in my Gretch 5222 by just offsetting it slightly on the baffle. Sounds fantastic to me. The 8" Weber looked to have magnet clearance problem for changing o.t.tube. I have a faint sizzle through the speaker at times when striking bass notes. Any ideas what might cause this?
Thanks Gary@thesoundworks.com

Anonymous said...

where is the speaker output jack on the 600 located?

Guitar Man said...

This is a great comparison with effect use of graphs and great analysis. As an old doc of education, it is right up my ally, not to mention the great subject matter-- near and dear! Well, please join my blog if you get a chance. I am not as well established as you are. Thanks.