I've got an old set of pioneer 8" FR drivers (not guitar speakers). I am planning to get an amplifire (atomic) amp sim pedal. I wanted to build 2 cabinets. I was thinking that it would be good if they could be used for home audio application as well but that isn't 100% necessary. I wont be using these to play loud. The idea is low volume stereo setup with my pedalboard. I noticed the Yamaha THRs use ported design for their tiny little FR speakers. They actually sound not bad at low volumes and I doubt they are flat response design.
I guess the question is, how to design the cabinet for flat response? And is it even necessary if not being used as a monitor setup for recording?
Other question is, can I just use a simple cheap class D amp in this scenario? Basically the amp sim pedal is going to be giving all the character including impulse responses.
I guess the question is, how to design the cabinet for flat response? And is it even necessary if not being used as a monitor setup for recording?
Other question is, can I just use a simple cheap class D amp in this scenario? Basically the amp sim pedal is going to be giving all the character including impulse responses.
Mainstream audio engineers abandoned those dual-cone drivers many, many decades ago, because they are heavily compromised when it comes to full-bandwidth audio. Too big and heavy for good treble, too small and light for good bass, and a poorly controlled transition between the two.
In my limited experience, though, they can work well for guitar. I've tried two different ones, and both were usable.
The first driver I tried was a very inexpensive dual-cone ("full-range") 8-inch driver sold for paging and background music applications. Bass was quite badly lacking, but the very thin cone broke up severely and early, and that actually translated to very interesting and "vocal" sounding clean guitar tones.
The second one I tried was a GRS copy of your Pioneer speakers, also an 8". This one had better bass, but treble was not at all impressive for a supposedly full-range speaker. Efficiency was lower, as well. Still, it was good enough to become a permanent part of a little 2-watt (valve) combo guitar amp I built.
Looking at the "classic" guitar cabinet designs of the past, I would say that most of them had anything but a flat response. Open-back cabs have poor bass response; cabs with multiple drivers (4x10, say) have multiple deep notches in the frequency response; sealed cabs tend to be far too small for the drivers, so they don't have flat bass response either. Then again, those cabs worked very well with the amps they were designed for - flat and full-range was never part of the plan, or the sound.
I don't have a THR, but I do have a couple of Yamaha keyboards. To make their keyboards sound good, Yamaha became masters at the art of getting surprisingly decent near-flat response out of tiny little speakers. They actually use DSP frequency response correction, even in their entry level keyboards. I know this because there is a menu option to turn the DSP frequency response correction off, for those times when the keyboard is plugged into external speakers or P.A.
As for how to design cabinets for flat response, there are free software packages that can help with this. But it isn't always possible, or practical - many cheap speakers have a too-small magnet, with an accompanying bass hump that cannot be made to go away, no matter what size the cabinet. Other cheap speakers will require an impractically large cabinet to get the flattest response they are capable of.
Why not stick each of those Pioneers in the middle of a largish flat baffle (I would initially try it with a large piece of stiff cardboard, say 1 metre square or bigger), and see how they sound with the Amplifire? If you get acceptable sound that way, then you know you can do better with an actual enclosure. And if not, no need to waste any more time and energy going down that particular road.
My other suggestion is to take a quick look at the local thrift stores for boombox speakers. The era of big boom-boxes with separate speaker cabs is long over, and those things often turn up, very cheap, at thrift stores. They may be exactly what you want. I have a pair of old RCA boombox speakers hooked up to a little class-D power amp providing music in the spare bedroom, and they are quite adequate for casual listening.
My one caution about class D power amps is that they tend to sound really nasty if driven to clipping, and not in a good way. So I would suggest making sure the one you use has enough clean power so that you never need to clip it to get the volume levels you want.
Many of those bridge-mode class D modules will deliver some 35-odd watts into a 4 ohm speaker if powered by a (19.5 volt) laptop power brick. Most are also stereo (containing two separate bridge-mode amps), so you can use both your speakers. Something like this should be ample for the usage you describe.
-Gnobuddy
In my limited experience, though, they can work well for guitar. I've tried two different ones, and both were usable.
The first driver I tried was a very inexpensive dual-cone ("full-range") 8-inch driver sold for paging and background music applications. Bass was quite badly lacking, but the very thin cone broke up severely and early, and that actually translated to very interesting and "vocal" sounding clean guitar tones.
The second one I tried was a GRS copy of your Pioneer speakers, also an 8". This one had better bass, but treble was not at all impressive for a supposedly full-range speaker. Efficiency was lower, as well. Still, it was good enough to become a permanent part of a little 2-watt (valve) combo guitar amp I built.
Looking at the "classic" guitar cabinet designs of the past, I would say that most of them had anything but a flat response. Open-back cabs have poor bass response; cabs with multiple drivers (4x10, say) have multiple deep notches in the frequency response; sealed cabs tend to be far too small for the drivers, so they don't have flat bass response either. Then again, those cabs worked very well with the amps they were designed for - flat and full-range was never part of the plan, or the sound.
I don't have a THR, but I do have a couple of Yamaha keyboards. To make their keyboards sound good, Yamaha became masters at the art of getting surprisingly decent near-flat response out of tiny little speakers. They actually use DSP frequency response correction, even in their entry level keyboards. I know this because there is a menu option to turn the DSP frequency response correction off, for those times when the keyboard is plugged into external speakers or P.A.
As for how to design cabinets for flat response, there are free software packages that can help with this. But it isn't always possible, or practical - many cheap speakers have a too-small magnet, with an accompanying bass hump that cannot be made to go away, no matter what size the cabinet. Other cheap speakers will require an impractically large cabinet to get the flattest response they are capable of.
Why not stick each of those Pioneers in the middle of a largish flat baffle (I would initially try it with a large piece of stiff cardboard, say 1 metre square or bigger), and see how they sound with the Amplifire? If you get acceptable sound that way, then you know you can do better with an actual enclosure. And if not, no need to waste any more time and energy going down that particular road.
My other suggestion is to take a quick look at the local thrift stores for boombox speakers. The era of big boom-boxes with separate speaker cabs is long over, and those things often turn up, very cheap, at thrift stores. They may be exactly what you want. I have a pair of old RCA boombox speakers hooked up to a little class-D power amp providing music in the spare bedroom, and they are quite adequate for casual listening.
My one caution about class D power amps is that they tend to sound really nasty if driven to clipping, and not in a good way. So I would suggest making sure the one you use has enough clean power so that you never need to clip it to get the volume levels you want.
Many of those bridge-mode class D modules will deliver some 35-odd watts into a 4 ohm speaker if powered by a (19.5 volt) laptop power brick. Most are also stereo (containing two separate bridge-mode amps), so you can use both your speakers. Something like this should be ample for the usage you describe.
-Gnobuddy
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