Question about speaker response graphs

Gary Cosden · From: Florida, USA

I recently bought an ’86 Fender Dual Showman head and Ken Fox worked his magic on it. I am liking it more and more as time goes by. So far I have not sorted out a speaker cabinet for it and I have just played it through the 15” Black Widow in my Nashville 400 which sounds good but I am leaning towards trying an Eminence Delta Pro 12A. One issue is the Dual Showman has a 4 ohm output and the 12As only come as 8 ohm speakers. I could do a 2 12 cabinet and end up with 4 ohms But I still wonder why no one seems to use 10” speakers with PSG. I guess back in the day the old 4 10 Bassman amps were somewhat popular but I can’t think of a single player today who uses 10” speakers. This brings me to my question about speaker response curves. I know enough to be dangerous when it comes to interpreting them so I am asking those of you who may be willing to offer their insight.
Here is the graph for an Eminence Delta Pro 12:

Here is the graph for an Eminence Delta 10:

It seems to me that judging by the graphs alone they ought to be pretty similar sounding speakers. How much can you hang your hat on the response curves when it comes to speaker tone?
Any one out there actually using 10s?

David Doggett · Posted 24 Sep 2009 10:13 pm

Those charts are not as similar as you might think. Our ears are most sensitive to the mid frequencies, say 200-1000 Hz. The 10 chart is much lower in dbs in that range. So you will tread on the volume pedal heavier. That will drive those treble frequencies, say 11k-15K Hz off the chart. That agrees with my experience with 10s for steel. They are very piercing in the treble range. They sound great to me for guitar. The guitar player in my band plays a Vibrolux 2x10 and sounds great. But with my psg it sounds too trebly. Likewise with the 1x10 Princeton I have. Maybe it's because we only have a bridge pickup on most pedal steels, but most steelers prefer 15s. 12s are okay. But 10s are just too shrill for most of us. But, forget the charts, and don't take my word for it. Find something with 10s and plug your steel into it and see for yourself. A few people like them. But 15s are very standard for psg, and for good reasons. It's not just about the stronger lows with the bigger speakers - the whole voice of the speaker is shifted lower, and you can hear it in the highs.

Richard Damron · From: Gallatin, Tennessee, USA (deceased)

David -

I think that I can shed a little light on your response and, perhaps, take you to task on one point.

First - One must assume that the measured sound pressure levels are taken with the speaker driven at maximum, rated, INPUT power which, as I'm certain you know, is NOT the same as the sound pressure level measured at the output of the speaker. It would appear, then, that the power handling capability of the "10" is much less than that of the "12". Given that, it is obvious that any attempt (treading on the volume pedal) to make the Delta 10 perform at a level with the Delta Pro 12 may well result in the destruction of the speaker - mechanical limitations at the low end being a major factor - UNLESS both speakers are being driven identically and at a level less than the maximum of the "10" in which case one can make a valid comparison.

I've taken the liberty to superimpose the two curves so as to get a RELATIVE idea of the differences in their responses. They are remarkedly similar - with one exception. The "12" exhibits a relatively smooth rise from the range of, say, 200-500 Hz up to the peak in the range of 2Khz - 4Khz. The "10", on the other hand, tends to start out flat in that same 200-500Hz range but has that nasty dip at about 650Hz before rising dramatically to its peak in roughly the same range as that of the "12". It may be this marked discontinuity in the response curve of the "10" which manifests itself in a perceived "shrillness" whereas the "12" tends to fill in this "hole". There is, however, a caveat which should be issued with regards the above. We are viewing the response curves of only two, selected, speakers. The availability of such curves associated with several different speakers would most likely be very informative.

Secondly - All such response curves are plotted - for convenience sake - on a logarithmic scale. I think that you've misread the scale. In the response curve of the "10", the small peak above the "UM" in the word "Forum" below the curve occurs at 10Khz. Neither of these speakers shows any considerable output above, say, 5 or 6Khz. Nor were they designed to do so. Smaller speakers (generally) and tweeters handle the higher range. Given that, any reference to frequencies in the "11-15Khz" range is a moot point. They are simply not there - relative to the response in mid-range.

To Gary, I can only suggest that you settle on a speaker with the smoothest, flattest, response over the frequency range of interest and with a power output - sound pressure level in conjunction with an appropriate power amplifier - to suit your needs. In my view - and within reason - a speaker should not color that which is fed to it - the "breaking-in" concept notwithstanding. It will, therefore, reasonably reproduce anything generated by the instrument and associated electronics. That is, unless you enjoy the sound of a speaker breaking up at higher power levels. NOT.

Hope this helps.

Respectfully,

Richard

Georg Sørtun · From: Mandal, Agder, Norway

Allow me to add...

Such sensitivity/frequency curves are normally measured at a short distance with the speaker mounted in a standard-sized "plate" with a 1 Watt RMS input sweep. If those curves were for full power input, one would hardly hear those speakers even up close on stage.

A normal "instrument" speaker has a sensitivity in the 90 - 105 db range for midrange for that particular speaker. The higher sensitivity the better, as long as the speaker is of a reasonably good quality and don't break up too easily.

Of those two the 12" looks better, but that's just one of the many measurements one need for making good judgment of what it's suited for. Thus; I won't/can't tell you which one will work best for your particular need.

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Take it from me, the curves of the two speakers you've shown are literally worlds apart. At just about any given frequency, the Delta Pro 12" is showing 5-10db more output. That translates into a speaker that is easily twice as loud (with the same input signal), and that is quite a significant difference (like going from a 25 watt amp to a 100 watt amp). Other important factors such as transient response, capacitance curves, and back EMF aren't illustrated, so it's difficult to say what the tonal differences would be unless we knew more about the amp and speaker enclosure that would be used.

David Mason · From: Cambridge, MD, USA

If you look at the "curves" from any other speaker, it's going to look "similar" - but as others have pointed out, the little differences sound huge. No speaker is going to plot a frequency response curve that looks like a cantaloupe or Batman or something.

P.S. I just bought a Eminence Beta 12A and so far, I'm happy - it's sold as a bass speaker, and that's what you want for PSG, unless shattering wineglasses is part of your schtick.

David Doggett · Posted 26 Sep 2009 9:44 am

I'll admit, just eyeballing those charts and imagining what they sound like is dicey. I'm working backwards. I have compared 10s, 12s, and 15s plugged into the same amp. Fender tube amps from the '70s and earlier have phone plugs on their speaker cords. With an extension speaker cord and double female adapter, I can plug the 10s of a Princeton or Vibrolux, or the 12s of a Pro or Twin, or a JBL 15 I have in a Pro Reverb, all into any of those amps, or into a Dual
Showman Reverb head.

So I'm hearing all the speakers in their open back Fender cabinets, but using the same amp chassis for all of them. They have three very different voices to me, beyond the differences between brands and models of the same size. For pedal steel, the 10s I have tried sound shrill compared to 12s, and 15s have an even deeper voice.

Actually listening to the speakers is all that counts for me. I'm just looking at those charts and trying to guess how they explain the differences I hear.

You can use multiple 10s to get the same volume output as 1x12 or 2x12 or 1x15 or 2x15. So you can move the same amount of air. But it's moving with a different frequency spectrum. The different voices I hear from the different sized speakers don't change by adding additional speakers of the same size, they just get louder with the same unique voice.

I just don't think you can base a decision like this on looking at charts and what other people say. Some people will always come on here and say they use 10s and like them. Others will say they like 12s. And most pedal steelers prefer 15s.

I actually prefer 12s for rock and blues on pedal steel. They cut through the mix better, and sound more guitar-like. I prefer 15s for country and jazz. The highs are a little thicker, and the lows have that organ-like fullness. I haven't found any use for 10s for pedal steel, but I like them for a clean or "chimey" guitar tone. You just have to try different stuff and suit yourself.

Gary Cosden · From: Florida, USA

Thanks to all who responded. Donny - I think you expounded on my one reservation regarding the comparison of the two graphs. You are right in that 5-10db difference is huge indeed although (I should have said this up front) I was thinking more along the lines of a 2 10 cabinet vs a 1 12 cabinet so the ~30% more cone area may well negate a lot of that. In any event I can't afford to do too much experimenting so I will probably go with either a (2) 12 cabinet or 2 (1) 12
cabinets with a 4 ohm 12 in each. My Dual Showman has a 4 ohm output with a 2 Ohm tap via a switching jack so I can actually run 2 4 ohm loads on it. Decisions decisions.

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