Thinking of making a small combo amp/speaker for my electric cello. Thoughts?

I need a practice amp/speaker for my electric cello. Guitar amp combos are a common solution, but they're intentionally designed to produce a "tone", which isn't great with Cello. Some electric-cellists use PAs or Keyboard speakers, but the used market is no good for those.

I'm looking for driver suggestions. Goals:
  • Similar form factor to my Marshall (480 x 420 x 225), or smaller
  • Not very expensive. No boutique $200 drivers.
  • Flattish in the cello frequency range (65 - 880hz, plus harmonics), I'd probably be fine with it not reaching the full 65hz)

The first option I thought about just using a guitar amp speaker like the Celestion Ten 30 (perhaps mated to a tweeter or small fullrange). Alternatively, a Peerless SDS-160F25PR01 models remarkably well down to 65hz in a small box, but I'm sure there's a catch.

Any recommendations or thoughts? Cello presumably shouldn't produce the same speaker-killing dynamics as electric guitar. I have a spare 60W@8ohm stereo pro-audio amp that I intend to use. I have plenty of guitar effects pedals, so I don't need any built in reverb

A cellist on youtube uses this amp: https://www.thomann.de/gb/dv_mark_ac_101h.htm. I guess that's a target to aim for
 
I thought about just using a guitar amp speaker like the Celestion Ten 30

I do not recommend you use a guitar speaker as they are not designed with a smooth frequency response in mind.

The Peerless looks a good choice as it has a reasonably flat response over the range of the fundamental frequencies of the cello.

Response graph here: https://products.peerless-audio.com/transducer/156

Add a tweeter crossed over above, say 1,500 Hz, to reproduce the cello's harmonic frequencies.
 
How high do the harmonics reach

I have no idea sorry. I'm not really clued in on how instruments make their sound, but my general understanding is that they tend to produce sounds above what is actually capable of being played? An electric cello is a solid body instrument and just uses a piezo pickup under the bridge. Further research indicates that in advanced playing positions it can, in theory, go up to 2093hz.

Add a tweeter crossed over above, say 1,500 Hz, to reproduce the cello's harmonic frequencies.

A Peerless D19TD05 is readily available and might do the trick. I feel like there must be some catch though. Sticking home stereo speakers in a box feels too easy to be true
 
I think standard 2 way speakers intended for home use would be suitable, as the amp is in place.
You might find some for sale in good condition, that will save you a lot of work. A single one may be at 'take it away' price.
Cabinet, crossover, drivers, assembly, trouble shooting and so on.
 
Unnecessary work is the point of hobbies, right? I've built (single driver) speakers before, so I'm not overly concerned about the process of building it.

My real concern is with whether a 2-way home hifi speaker is the correct/ideal way to achieve the goal. Previous research has indicated that hifi speakers are useless in guitar combo amps, so it seems too "easy" for a simple 2-way powered speaker to be best solution for a cello combo amp.

I linked to a Markacoustic AC 101 H as being an ideal benchmark of what I'm going for (minus the effects). That particular speaker is made by a brand that primarily makes bass guitar amps and speakers

edit: Markbass and Markaccoustic speakers both hsave yellow coned drivers, so they may even be the same drivers as their bass amps
 
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Home speakers would probably do it, but if you do try to get any volume beyond apartment levels or just one accident and the tweeters are toast. If you go the home-speaker route I’d seriously suggest using a small 15-30 watt full range as the tweeter. The kind make for a Bluetooth speaker. It will go high enough and be robust enough. A small compression driver/horn would work too, but require about 15 dB of attenuation (It’s the 15 dB pad that gives the power handling, BTW).

My go-to would probably be the Eminence Beta 8, and one of the small PA compression horns (With 8-10 dB of pad). That is a “proper” bass guitar practice rig and would do exactly what you need. Prices have really crept up on those over the years - they used to be 40 bucks. At that price it was a no brainer, today you have to stop and think. There are several similar available for $50-ish - but with about 2dB less sensitivity. You could live with that - it would still be 5-6 dB louder than the home speaker alternative, and zero potential for frying something. A cheap-o alternative would be the BOFU clone, which may be ok without a tweeter.
 
My real concern is with whether a 2-way home hifi speaker is the correct/ideal way to achieve the goal.

The thing to avoid is a speaker driver or speaker system that has an uneven response at the higher frequencies.

The high frequency harmonics are what gives a cello its unique tone and can, in an acoustic cello, reach up to 10,000 Hz.

An uneven response would colour the tone of your cello when you want it to sound natural.

So, it is really a "Hi-Fi" type response you are after.

I don't expect you'll be playing excessively loud, so factors such as loudspeaker power handling and sensitivity will not be much of an issue.

EDIT: Apart from wg_ski's caution regarding the tweeter that is.
 
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You will struggle if $200au seems in the boutique territory, maybe look for some older HiFi speakers wire them in series and connect too your instrument amp.

I use a pair of Edifier S3000PRO for my syth, easily loud enough for home use with very reasonable sound quality
 
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About around electric bass.
Most of what is heard is 3000 Hz and upper detail 6 to 8000 Hz

lowend can get there but is harmonics so 30 Hz but what is heard
around octave higher 60 Hz

So 12" is good start and if wanting 2 way
12 " with a 5" or 6" mid.

If practice only could get pretty nice response.
For live or busking High Spl could be smooth with 2 way
and then high-end is whatever the 6" is.

" average" generic enclosure for 12" be about 45 to 55 liters
then 10" be around 25 to 35 liters.
exact size depends on speaker choice and would just use
Common QB3 or BB4 alignment

Guitar speakers have high SPL but they would go into distortion rather quick

GRS 10PT-8 for 10" or GRS 12PT-8 for 12"

both could be crossed to a 6" midrange for 2 way.
GRS 6PT-8
 
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The first option I thought about just using a guitar amp speaker like the Celestion Ten 30 (perhaps mated to a tweeter or small fullrange). Alternatively, a Peerless SDS-160F25PR01 models remarkably well down to 65hz in a small box, but I'm sure there's a catch.
I have a spare 60W@8ohm stereo pro-audio amp that I intend to use.
The "catch" with the Peerless SDS-160F25PR0 would be the low sensitivity, it would only do around 106dB with 60 watts, while the Celestion Ten 30 has about 8dB more sensitivity in the top end.
 
Cello presumably shouldn't produce the same speaker-killing dynamics as electric guitar.
I don't know about that (FYI Currently listening to Derksen, Cris. LAND BACH [06'36] Julia MacLaine (cello), Preludes Analekta AN28914 ).

Unfortunately, Hoffman's Iron Law applies. How loud do you need to go? There's a real trade off between efficiency, f3 and flatness

Hi Fi speakers are meant to be flat, but $200 won't buy you much and that's before you add crossover components, wood and woodwork.

I'd really suggest going around to a bunch of cash convertors or similar and listen to a bunch of amps and speaker boxes to see what you like the sound of.
 
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A piezo pickup is going to need a preamp with super-high input impedance, correct? I assume you have that sorted out already. What are you using? LR Baggs? Fishman?

The rest is power amp and speaker (which includes the crossover network diving the frequencies between the woofer and tweeter). There are really good active PA speakers these days, which would give you a 2-way with the amps and a properly designed crossover built in. The QSC K10 is well respected, or JBL EON 710 perhaps. You could also scrounge a power amp of some kind (maybe a used Hafler, QSC or similar) and the very inexpensive ($150 each) Behringer B212XL portable PA speaker (12" woofer, compression driver horn tweeter). These everyman PA speakers are popular with the home theater crowd because their frequency response is as accurate as most hi-fi speakers. The don't go below 100Hz in the bass, but for 'cello that shouldn't be too much of a problem. You could probably use EQ to boost the mid-bass to taste (60Hz to 200Hz region). That would be pretty much indestructible unless you crank 'it to the hilt onstage.

If you want more delicacy of tone you could try an active studio monitor like the JBL LSR308mk2 (8" 2-way, $250 for one of them, which is the speaker, crossover and amplifiers all in one). The problem with that would be the reduced power handling capability and max loudness compared to PA speakers.

If you're going to build your own speaker and use a miniDSP or similar to do an active crossover, then yes, you could purchase a separate woofer and compression driver with horn/waveguide for the tweeter, and design, build, test the crossover until it's right. That would give you a top-flight high-SPL monitor. That would require a lot more work, though.
 
Others have said this, if you want to get going fast pick either a powered or passive, if you really want to
use the amp that you have, PA speaker.
Passive: https://www.crutchfield.com/p_855JRX215/JBL-JRX215.html
Powered: https://www.crutchfield.com/p_855IRX12BT/JBL-IRX112BT.html

If you really want to DIY it an econowave is an obvious choice.
The Advent Econowave uses the same horn as in the above passive PA speaker but it is rather expensive to build
and is not efficient. You could do more of a PA version with the Dayton PA310 woofer that is also documented.

It is a lot of work to build the box etc. and you can often find solid state sealed box (or ported) bass amps
from Fender for under $100 on ebay and other places. Just use the box and anything else that's useful from it.

Here's a smaller/cheaper econowave but I don't think the woofer is large enough for any serious playing, perhaps
double up on the woofers or choose an 8 or 10". He does a very nice design work:
https://www.mtg-designs.com/diy-speaker-plans/vbs-6-2
Here's a 10" based design: https://www.mtg-designs.com/diy-speaker-plans/vbs-10-2
More:
https://www.mtg-designs.com/diy-speaker-plans

It only makes sense to DIY if you really enjoy the work because you'll never match component costs
that a large company gets by buying in bulk.