How do you voice your amp to the speaker and cabinet?

[Decko]

Hi AGers,

I finally completed my 4th amp build. It is another 2 watter with Trainwreck front end.
Sounds nice...a bit bright but I attribute that to being a new build.

My choice speaker is the Greenback for this amp design.

I loaded two greenbacks in an Avatar 2X12 cabinet open back and the tones are there. (8 ohms) Punchy and clear with nice amounts of bass thump and tightness. Overdriven tone is chewy and raucous.

I then took one Greenback and placed it in a 1X12 closed back cabinet and it sounded terrible. (16 ohms) The low end sounded unfocused and muddy. I was surprised! I thought closed back cabinets produced a tighter overall output.

I also experimented with a 4X12 cabinet. Sounds full. Nice but very different from the first 2 enclosures.

Then I started farting around with G12H 30's, Celestion Golds, Fender stock speakers, Eminence, etc.

These exercises have been fun yet frustrating!

Having said all this, I have concluded that choices in both enclosures and speakers are a huge part of the overall architecture of tone scuplting. A whole different world.

My experiments have all been "trial and error" so I have to buy and try.

How do you voice your amps to your speakers? Is there a more scientific approach? How do you know which speakers sound good with what amp designs? Are there basic speaker, enclosure amp standards for tones/genres?

Thanks,
Danny

[iknowjohnny]

To me all that means is you decide on a speaker you want to use, then when designing the amp you simply do whatever sounds best to you. Just having that speaker in it will automatically cause you to voice the amp to the speaker because you are tweaking component values and design to get the best tone out of it. And the speaker is putting it's signature into the sound which will cause you to tweak values differently to get the tone you want then if you had a different speaker.

Heres an example of what i mean. lets say you have a speaker with high end thats a bit too much. Naturally when you are designing the amp, assuming the high end is too much for what you want you will do some tweaks that will reduce highs. Maybe a large grid stopper or such. Now had you picked a dark sounding speaker you wouldn't have made that tweak because then the amp would be too dark. so as you see, the speaker will to some degree dictate how you design the amp, and to me that is designing around a speaker. But if the speaker is somewhat flat then the amp may be more neutral to speaker choice. I use a EV and i think maybe that may be why my amp seems to sound good with any speaker i've tried. But say you design around a speaker with a huge midrange dip. You would tend to make the amp more midrangy in the design. then if someone put a speaker in it that already has a lot of midrange, especially in the same region, it might sound horrible because you now have a huge mid hump. Thats how i see designing around a speaker anyways.

[Decko]

I appreciate your response Johnny. Maybe I am going at this hobby the wrong way. My primary focus has been about the amp then the speaker. What you are saying makes complete sense. The different speakers or drivers on the market operate well within their given specifications. It would then be my job to design or tune my amp to maximize the performance of the speaker. Find that sweet spot!

Could you recommend a good tutorial or book that speaks of the tweaks and or amp design optimization as it relates to different type of speakers? For example: a 12 inch Alnico works best with this amp layout or Altechs work great around this type of design. Something that can help me to realize the "tweakable" component values in various sections within the amp with a direct emphasis on driver response?

Thanks,
Danny

[RevD]

A handy tool for quickly tweaking and auditioning different preamp/bypass resistor values is a resistor sub box. Basically (sorry for the explanation if you know what it is, some might not use them) its a rotary switch with various pre-amp resistors (they make them for larger power circuits as well and also Capacitor substitution boxes) and a pair of alligator clips. You clip it in circuit and dial away until you tune it to where you want it, note the value and solder it in. Makes it so much faster than say putting the resistor in, shoving a toothpick in the turret to hold it in and then powering it up and trying it, powering down, draining and repeating. Just thought I'd mention it, good info too on tuning to a speaker, I often forget about that stuff and would be disappointed how a cab would sound. I guess in some ways I'm lucky I'm rather poor, that way I have less to choose from haha. Good luck with it.

Regards,

D.

[Torquil]

Could you recommend a good tutorial or book that speaks of the tweaks and or amp design optimization as it relates to different type of speakers? For example: a 12 inch Alnico works best with this amp layout or Altechs work great around this type of design. Something that can help me to realize the "tweakable" component values in various sections within the amp with a direct emphasis on driver response?

I would think that what works best with what design is very subjective. And there are probably large differences between different speakers even if they have the same magnetic material, e.g. baffle stiffness, the amount of moving mass and magnet strength, and the cabinet size/type would have a large influence itself.

I think the simplest consideration is frequency response, which you can tweak almost everywhere in the amp, especially in the tone stack.

You might check out how global negative feedback changes the interaction between amp and speaker:

http://www.aikenamps.com/GlobalNegativeFeedback.htm

Of course, the differences between behaviour in different speakers/cabinets is too complex to compensate for exactly in the amp.

Regarding frequency response, you could even tailor your amp for recording by e.g. making a recording using your mic of choice, and analyze the results. In this case you might not want the amp to sound ideal in the room, but ideal through the mic instead (probably different).

[breakfastbuddy]

download the tonestack calculator so you can see what kind of values you need in your tonestack
here is the page
http://www.duncanamps.com/software.html

[Structo]

Yes it can be frustrating.
I think most of us have probably chased speakers and cabs over the years.
I think more than likely, we discover a speaker that we like a lot then try to tune the amp to work with that.

Or we know that certain speaker sound good with certain styles of amps, like Fender Blackfaces and Jensens.
I really like the EVM 12L Classics and have an open backed 2 x 12 with those.
The cab can make a big difference too.

The hard thing to remember when you are new at this is to give the combination a fair chance before changing it.
Get those speakers broke in as well as let the amp settle in before making drastic and costly decisions.

I hate to think how many speakers are gotten rid of because the person didn't understand how much they will mellow after some hours on them and lose that that harshness that comes with new stiff cones.

It can be a trial and error thing and sometimes takes years to find what sounds good to you.
The main thing is to have fun, enjoy the process and learn from it.

[billyz]

In my experience, low wattage amps perform best with lighter weight speakers. A sealed cab can require a more powerful amp to get the speaker moving , especially on the low end. at the other end, a speaker like an EV needs a 60-100watt amp to really drive it well, otherwise it sounds constipated with a lower wattage amp.
It is not the weight of the frame but the weight of the cone paper, and stiffness of the spider etc. that is one reason old Celestions sound better than modern reissues, The modern ones have heavier cones.

If you try to drive a light weigh speaker from a bigger amp , the speaker will fall apart and eventually fail, the low end is a mess.
a small amp into a heavier speaker will sound thin and tight. It is a balancing act .

the cabinet becomes the speaker as well. It should enhance the speaker, but a poor choice can hinder.

The wattage of the speaker has a lot to do with the voicecoil. Old Jbl's had pretty lightweight cones but very large magnets and very efficient voicecoils, but they were rated for no more than 60 w or even 30 w.

the speaker and cab can make a huge difference in the sound quality. bigger than a capacitor or resistor change, tube change etc. there is a synergy between amp and speaker.
which came first, the chicken?