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  • Building a little guitar practice amp (driver advice)

    So I'm going to be building a little amp for guitar practice. I love the flexibility of a software amp but getting tired of it running off my computer. So I want to build a little self contained unit with a d/t-amp and a usb interface to a tablet. (don't worry I've got all that figured out)

    My question is drivers. I'm going to be building a stereo amp, I think, just in case I ever want to plug in an aux source. Originally I was going to just use c-notes but they are out of stock for months and I don't really need all that for what's going to be a guitar amp for 99.9% of the time.

    I was looking at these drivers (around $50 for a pair): The 4" full range ones are about $15 more for the pair.... are they worth it? Any other 4-6" drivers I should be considering? This is never going to be for anything other than playing for myself in a 12'x12'ish room. Thanks!
    Last edited by nikbrown; 05-06-2020, 11:07 AM.

  • #2
    Eminence 620H or 820H, or Celestion Eight 15. Guitar amp drivers and PA drivers aren't the same.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #3
      Originally posted by billfitzmaurice View Post
      Eminence 620H or 820H, or Celestion Eight 15. Guitar amp drivers and PA drivers aren't the same.
      Thanks! I can do a little 2x8 cabinet with the Celestion's. I have a little SMSL SA50 50Wx2 Class D Amp laying around I was going to build into my cabinet to drive them. See any problems with that?

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      • #4
        You'll need a pre-amp too, one made for guitar.
        www.billfitzmaurice.com
        www.billfitzmaurice.info/forum

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        • #5
          Originally posted by billfitzmaurice View Post
          You'll need a pre-amp too, one made for guitar.
          Yea I'll be running the guitar into an iRig UA... it will work with an Android tablet to process the signal from the guitar and then apply various peddle and amp affects to the signal and then push it out of the headphone jack on the iRig.
          https://www.ikmultimedia.com/products/irigua/

          I'll go out of the headphone jack, into the SMSL SA50 amp, and into the drivers. At least that's the plan

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          • #6
            If your looking for a small starter amp, PE sells a Diy amp. Part # 249-404. That would pair with one speaker.

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            • #7
              Originally posted by Jake View Post
              If your looking for a small starter amp, PE sells a Diy amp. Part # 249-404. That would pair with one speaker.
              Thanks for the suggestion but the whole point of this project is to let a tablet and amp emulator app handle the processing of the signal.

              I have had a couple of inexpensive real guitar amps but haven't been happy with their sound profiles for anything but a clean tone. Because of that I've been doing most of my playing utilizing Aplitube or Logic pro on my computers. This project will allow me to have a small portable practice amp with the full processing brains of Amplitube on a tablet.

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              • #8
                Usually music reproduction (and PA) speakers are made to have a somewhat flat frequency response at the cost of losing some efficiency while guitar speakers will have a noticeable peak around 1.5-3.5k that's part of their sound rather than something to be fine-tuned away...they're meant to have "character" rather than aiming to be flat. Guitar speakers are also generally a solid 5-10db more efficient, so they're noticeably louder watt-per-watt.

                The Dayton PA165, however, happens to be about as efficient as the Celestion 8" and also has a somewhat similar 5db peak in the mids (though it's a little lower frequency around 1.5 rather than 2.5K). The pa165 also claims a higher wattage handling ability than most small practice amp speakers. The dedicated guitar speakers can still have other differences, like planned breakup/distortion characteristics, but if you're limited to a smaller 6" size or a $20x2 budget the PA165 is far from the worst option.
                The RS100 and most other regular music reproduction speakers (and most other PA speakers) will sound quiet and fizzy and boring when used as a guitar amp speaker.
                My first 2way build

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                • #9
                  Originally posted by LOUT View Post
                  Usually music reproduction (and PA) speakers are made to have a somewhat flat frequency response at the cost of losing some efficiency while guitar speakers will have a noticeable peak around 1.5-3.5k that's part of their sound rather than something to be fine-tuned away...they're meant to have "character" rather than aiming to be flat. Guitar speakers are also generally a solid 5-10db more efficient, so they're noticeably louder watt-per-watt.

                  The Dayton PA165, however, happens to be about as efficient as the Celestion 8" and also has a somewhat similar 5db peak in the mids (though it's a little lower frequency around 1.5 rather than 2.5K). The pa165 also claims a higher wattage handling ability than most small practice amp speakers. The dedicated guitar speakers can still have other differences, like planned breakup/distortion characteristics, but if you're limited to a smaller 6" size or a $20x2 budget the PA165 is far from the worst option.
                  The RS100 and most other regular music reproduction speakers (and most other PA speakers) will sound quiet and fizzy and boring when used as a guitar amp speaker.
                  Thank you for really solid information!!! I'll probably get the Celestion 8's.

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                  • #10
                    Originally posted by LOUT View Post
                    Usually music reproduction (and PA) speakers are made to have a somewhat flat frequency response at the cost of losing some efficiency while guitar speakers will have a noticeable peak around 1.5-3.5k that's part of their sound rather than something to be fine-tuned away...they're meant to have "character" rather than aiming to be flat. Guitar speakers are also generally a solid 5-10db more efficient, so they're noticeably louder watt-per-watt.

                    The Dayton PA165, however, happens to be about as efficient as the Celestion 8" and also has a somewhat similar 5db peak in the mids (though it's a little lower frequency around 1.5 rather than 2.5K). The pa165 also claims a higher wattage handling ability than most small practice amp speakers. The dedicated guitar speakers can still have other differences, like planned breakup/distortion characteristics, but if you're limited to a smaller 6" size or a $20x2 budget the PA165 is far from the worst option.
                    The RS100 and most other regular music reproduction speakers (and most other PA speakers) will sound quiet and fizzy and boring when used as a guitar amp speaker.
                    So I talked with IK multimedia the makers of AmpliTube (the amp emulation software) and here was their .02:

                    “Since AmpliTube is emulating the whole chain including the speaker cabinet, you would want to use a full range speaker. The sound is already imbued with coloration from the emulated gear including the speaker/cab so you would not want to further color the sound or limit the frequency range.“

                    So I guess I’m back to a full range speaker. 🤷🏼‍♂️

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                    • #11
                      FYI: Your 50 W x 2 amp will only reach 50 W per channel if: (a) You have a 24 V power supply; and (b) Your using a 4 ohm speakers. Using 12 V and 8 ohm speakers will yield ~8 W per channel. Double to 16 W per channel with 4 ohm speakers. 24 V and 8 ohm speakers will yield 33 W per channel. Power out is dependence on the PS voltage and the speaker impedance, not the marketing spiel. Those wattage examples are rms and with < 1% THD.

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                      • #12
                        Originally posted by nikbrown View Post
                        So I talked with IK multimedia the makers of AmpliTube (the amp emulation software) and here was their .02:
                        “Since AmpliTube is emulating the whole chain including the speaker cabinet, you would want to use a full range speaker. The sound is already imbued with coloration from the emulated gear including the speaker/cab so you would not want to further color the sound or limit the frequency range.“
                        So I guess I’m back to a full range speaker. 🤷🏼‍♂️
                        Many of these emulation/effects processors will let you customize your sound including turning effects off/on depending on what sound you want from it. If your version of AmpliTube lets you turn off/bypass speaker modelling (or if one or more of their cab models happens to be a little flat and fizzy sounding when played through a pair of headphones or whatever you have on hand), then you may still be better suited with something like the Celestion 8" (or the Dayton PA165 in a pinch) because they'll add some mids character and tame some fizz AND give you a noticeable volume boost compared to a normal flat-frequency speaker setup.

                        A regular speaker by itself will still naturally lack a lot of highs/treble either way unless you also add a tweeter or use a smaller 2-3inch fullway speaker, so I don't think you'll see a huge difference there compared to a smallish guitar speaker which will also lack some highs. Also, these smaller guitar speakers (and the PA165) don't have the full 10-15db peak in their mids and plummeting highs afterward, instead they have a more subdued 5-8db peak in the mids and a gentler fall-off in their highs afterward, so they're unlikely to sound nasal/honky when paired with a cab modeller.
                        Pairing a cab model with something like a 12inch Celestion Greenback would likely sound pretty obnoxious, but adding some cab modelling (if you can't simply turn that effect off) onto a small 8inch guitar speaker or something with similar character should be fine.

                        If you're okay playing at very low volume levels for practice, I don't think a regular speaker and a good speaker/cab modeller will hurt anything, but if your speaker/cab modeller is kinda subtle or you'd like to rock out a little louder then I think a guitar speaker (or the pa165 because of it's similar character) will be a better choice.

                        IF this is all sounding like too much, keep in mind that because you'll be using a speaker without a tweeter/fullrange either way, and you'll have a cab simulator, NONE of these should sound terrible. You're bound to have a fun little practice setup either way, so don't sweat it too much.



                        Millsonemike's info about different amplifiers is also a really good point. I still like the 50/50 amp idea compared to the Dayton Footnote amps (which can also be power supply limited plus they're capped at 5watts). I've noticed a lot of reviewers using these smaller chip amps with low-power supplies or batteries get surprised by how quickly they reach max volume and start to distort and they end up thinking something is wrong with the amp.
                        The positive side with the 50/50 is you're still probably able to provide a single speaker with 5-10watts even if you're starting with a relatively weak powersupply, and upgrading to something nicer (or grabbing a laptop 90watt supply if you have an old one laying around) can push its headroom up a decent ways.


                        I mostly keep bringing up volume stuff (despite this being a practice setup) because I feel like it can be annoying playing through something that's a little too quiet and having your strings twang/click loud enough to be easily heard over a too-quiet system when you get a little carried away. Electric guitar sounds kinda poo unplugged, and the closest person (most able to hear the guitar's "accoustic" sound) is the player. I don't like hearing that plucky sound over top of a practice amp, so I'm assuming others don't either. Having some extra volume will also be important if you (or anyone you practice with sometimes) likes to sing.
                        This is my own bias, so take it all with plenty of salt.
                        My first 2way build

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                        • #13
                          So and update on my little project...
                          I'm building a speaker cab specifically for my iRig. The iRig will be connected to an Android tablet and a little SMSL SA50 (50w Class-D amp). The iRig will take the guitar signal send it to the android tablet to be modeled and then back out the headphone jack (now in stereo) to the amp.

                          I will have 2x 8ohm speakers in my cab.

                          The SMSL SA50 delivers up to 22 Watts into two 4 Ohm stereo speakers at low distortion. It will drive 8 Ohm speakers up to 19 Watts at low distortion. More than that and the amplifier starts clipping which means that distortion shoots up. At 50 Watts the amp produces 10% distortion.



                          So here is what I'm thinking and I just wanted to run it by you guys. If I ever use my cab with a regular guitar amp head I'll wire the speakers in series for a 16ohm load.

                          For this little class-d amp I could wire them in parallel for mono with a 4 Ohm load. Or I can wire it as a stereo cab with each channel having an 8 Ohm load. I'll thinking that wiring for stereo would be better in this case (since the iRig is more of less just copying the mono channel)? Anyone have any thoughts on this?

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                          • #14
                            Nice joinery. Are you going to cover that with amp wrap? Or blue metalflake pleated vinyl (Kustom)? IME, the SA-50 is good until about 12 o'clock on the knob.

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                            • #15
                              Originally posted by djg View Post
                              Nice joinery. Are you going to cover that with amp wrap? Or blue metalflake pleated vinyl (Kustom)? IME, the SA-50 is good until about 12 o'clock on the knob.
                              Finished up my little project.... Went with the Celestion eight 15's .... maybe not quite as accurate as using a full range driver in this case but it means I can use my cab with regular guitar amps as well.
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