That makes sense, and it's a nice simplification.
I thought it was also interesting to see what the corresponding predicted changes in (infinite baffle) driver frequency response are. Unfortunately, there is no trustworthy way to predict the treble response because there are too many variables (cone breakup, etc), so I only know how to calculate the bass response.
There is still a big missing piece, i.e. the acoustic response in an actual guitar speaker cab. I suspect that many open-back cabs, particularly smaller ones, will roll off deep bass so much that changes in bass response due to amplifier output resistance may become irrelevant. (But treble response changes due to voice coil inductance interacting with amplifier Zo may still be audible.)
But I think you've already got most of the meat off the bones. We're just picking at scraps now.
-Gnobuddy
Try my "3 A.M" Simple Attenuator, lets you play full blast at 3 AM with the baby sleeping on the next room.
This one is for 30/40W amps, you can use a 25W main resistor ... or just use a 50W one and play it real safe.
Mount the main reistor on standoffs allowing air circulation around it and place it inside a perforated case for ventilation, it becomes quite hot.
The others ... no big deal.
You can build it "fixed" or use a rotary switch to change attenuation.
I´ve sold over 100 of them, very useful in the modern appartment life with "sensitive neighbours"
I made the same one, integrated it in my EL86 amp, it sounds beautiful at room levels! Nice and crunchy, thanks again for this wonderful, yet simple design!
To bump the old thread, I came across this attenuator implementation.
The logic being (in the Pos100) that you try to insert a "dead" speaker as a load, effectively one without a cone, just a reactance emulating the speaker coil.
I always thought it would be appropriate to try to emulate a correct "impedance", using reactive components to construct an equivalent speaker model as a total load. Having said that, I think it should be enough for my ears and likings to just use resistors to suck the power.
Reading this thread (post #18 and JMFahey's implementation) I understand that the resistor approach has proven effective. My question is, since the values depend on the output impedance of the amp, so they would vary from amp to amp (or even presence setting for the ones that alter the NFB path for this - perhaps to very little effect of course), isn't it an amp-specific design?
Could the design I attach be more effective in actual use in that it would cover more amps?
The logic being (in the Pos100) that you try to insert a "dead" speaker as a load, effectively one without a cone, just a reactance emulating the speaker coil.
I always thought it would be appropriate to try to emulate a correct "impedance", using reactive components to construct an equivalent speaker model as a total load. Having said that, I think it should be enough for my ears and likings to just use resistors to suck the power.
Reading this thread (post #18 and JMFahey's implementation) I understand that the resistor approach has proven effective. My question is, since the values depend on the output impedance of the amp, so they would vary from amp to amp (or even presence setting for the ones that alter the NFB path for this - perhaps to very little effect of course), isn't it an amp-specific design?
Could the design I attach be more effective in actual use in that it would cover more amps?
Depends how golden your ears are. The amp designs varry, NFB verses non-NFB. Why is it some say this speaker sucks and another it is fantastic? Part is the NFB keeping the amp well behaved (at least below clipping) where you get a non-NFB amp trying to keep power constant in a varying impedance therefore getting a rise in response either end. For the purists (Go to the Marshall site) you have a lot of tweaking. "Oh the treble is a little down", well turn the treble or presence up on your amp. "I don't want to do that." Well, then you need a more complicated attenuator.For some of us a simpler attenuator works fine. I just want an attenuator with two reductions settings.
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I was posting in this thread before, but my attenuator designs have moved along so im posting again. Adding a reactive coil, in the right way, helps a lot to maintain the responsiveness of the amp as you play harder and softer, as well as the basic tone, and its not expensive (the coil is about $10)
If you are building, and on a budget, check out our thread. Its 82 pages but just look at page 1 post 1, and the design M2. Its been build dozens of times now, and its about $100 in parts for the full version. It has been tested on many amps of many types, and it seems to adapt to them, maintaining the tone very closely right down to very low levels
Simple Attenuators - Design And Testing | MarshallForum.com
If you are building, and on a budget, check out our thread. Its 82 pages but just look at page 1 post 1, and the design M2. Its been build dozens of times now, and its about $100 in parts for the full version. It has been tested on many amps of many types, and it seems to adapt to them, maintaining the tone very closely right down to very low levels
Simple Attenuators - Design And Testing | MarshallForum.com
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In my younger days and with a very narrow budget, I used heating elements from washing machines. I do not recal the exact ohmic values, but I had about 10 of these. Connected in series and/or parallel, I managed to have an aprox load for any amplifier at that time (2 - 32 Ohms)
They can handle a lot of power and immerged in water, even more.
But do not hang your whatever test cables on these as they will melt to a solid block of plastic.
Cheap and eficient.
They can handle a lot of power and immerged in water, even more.
But do not hang your whatever test cables on these as they will melt to a solid block of plastic.
Cheap and eficient.
I doubt thats a good idea, as with such a transformer, you change the load to the guitar amp. the whole idea is to lower the SPL without changing the load to the amp.
Hi all after reading this thread, i have created a new topic about some attenuators i have built. https://www.diyaudio.com/community/threads/attenuators-t-pads-level-and-tonality.381958/