hifi speakers for a tiny guitar cab?

[clengman]

Hi,

New to this forum. New to DIY amp-building in general in fact, but I have an idea I just can't shake and I'm hoping I can get a little helpful information here. 🙂

I recently bought a vox ac4TV mini amp. In case you're not familiar with it it's a 4W Class A tube amp. It comes in 3 different combo versions 6", 8" and 10" speaker or a head and 1x12 cab. I was originally planning to buy the head and cab version, but saw the 1x6 combo on sale for $115 (hard to beat). I thought the small speaker might be useful for low volume so I went for it, intending to get an extension cab for it as well.

So... I like the amp a lot, but I'm not wild about the 6" speaker. It's not quiet enough to be useful as a quiet amp and it doesn't sound as full (obviously) as a 1x12 or 2x10 cab would.

So... I'd like to build myself a couple speaker cabinets. One will be a very conventional semi-open-backed pine 2x10 cab. This will be my nice-sounding cab for rockin' out when my family is awake.

For the second, I'd like to use a couple small hifi woofers (for instance hivi m3ns) to build a low-volume cabinet for nighttime use. I figure the lower sensitivity and smaller cone area will give me much lower volume compared to the 6" speaker that came in the ac4tv.

I realize these are not ideal speakers for an instrument amp application. It doesn't bother me that they won't sound terrific. I just want it to sound okay and to be less loud.

So... my question is: How do I design the enclosure (In terms of box volume? sealed or ported? port-size?) to get the optimal performance out of these speakers?

Another question: Are there any other 3-4" speakers that might be better suited to this application? (ie should I be looking for high or low Qts? anything else to look at?)

Thanks for looking!

 

[toprepairman]

The resonances in the cabinet are an important part of the sound, so build lightly with an open back and thin (6mm) plywood.
Best drive unit for this would be the 'woofer' from a cheap hifi speaker eg a panasonic (technics). you are besf off with one that has a paper cone and surround, NOT one with a rubber or foam surround. You should be able to find something suitable from a skip.

 

[leadbelly]

My general guidelines would be to use an open backed cabinet, and pick a driver with Qts > 0.7 and Le < 0.9; that will be pretty decent for guitar. I have to disagree with the previous comment, a woofer is not going to be good in general (but you might find one that has a low Le); look at PA, fullrange, MI drivers 1st.

 

[clengman]

Thanks!

So something like this: Overview of M3N Drivers_HiVi,Inc might work okay? There's a 4 inch version as well.

 

[Andrew Eckhardt]

Naw, something like this:

Dayton Audio PA130-8 5" Full Range PA Driver 295-010

MCM Audio Select 5'' Full Range Monitor Driver | 55-1595 (551595) | MCM Audio Select

With no worries about a bit of power loss you could add some series resistance to these to raise the Q. In that case the PE unit has better bottom end and maybe a bit more "guitar speaker - like" response.

After better reading your post, I'd recommend you're not likely to get more "fullness" by using a smaller speaker.

 

[Andrew Eckhardt]

You could try something like this:

Goldwood GW-1038/PA 10" Guitar Speaker 290-390

It has a low resonant frequency in guitar speaker terms, which might give you a heavier bottom end while burning some power overall. I have no idea how the top end sound might agree with you.

 

[Printer2]

Depending what you like I would suggest a 70v 8" public address speaker. Something like this

Radio Shack 40-1271 Fullrange Speaker Driver

If you want it quieter get an L pad for the speaker. I have been messing around with an amp I am putting together through two guitar speakers and a 8" similar to this one. For the bedroom (ok I converted the bedroom to a music room) I like it better than the 10" and 12" guitar speakers I have.

 

[clengman]

Depending what you like I would suggest a 70v 8" public address speaker. Something like this

Radio Shack 40-1271 Fullrange Speaker Driver

If you want it quieter get an L pad for the speaker. I have been messing around with an amp I am putting together through two guitar speakers and a 8" similar to this one. For the bedroom (ok I converted the bedroom to a music room) I like it better than the 10" and 12" guitar speakers I have.

I looked up l-pads and I think I get the idea. My amp actually has an attenuator to cut it from 4W to 1W to 0.1W. Is that the same as an l-pad?

 

[clengman]

So I appreciate the input so far. I'm not sure I understand, though. I don't have any design specs for the speaker that came with my amp, but I think it's on the low-efficiency end of the spectrum as guitar speakers go. Probably in the low 90s. I don't have anything to back this up except for some speculation I've seen around the webs that the AC4TVmini was intended to be a low volume version of the amp and probably has a low sensitivity speaker. So I'm thinking the volume of most of these PA speakers will probably be pretty similar to the one I've got already. It won't really accomplish what I'm trying to do.

I'd really like to get a pair of speakers (because I need a 16 ohm load and I very rarely see any 16 ohm speakers.) with a total cone area that's considerably less than the area of the 6" speaker I have (a 2x3 cab would be 4.5pi as opposed to 9pi for the 1x6) and with sensitivity in the low 80s. This is just to bring my volume down noticeably. I realize that 3" speakers aren't going to sound fantastic, but for pete's sake, the only amp I've played through for the past 10 years prior to getting my little vox is a smoky cigarette pack amp. I'm really not expecting much. I'll be happy if it sounds like a guitar at all and is quiet enough not to bother my wife watching TV in the next room.

Like I said above, I'll also be building a 2x10 to use when I'm not going to bother anybody. That'll be the cab that gets the good speakers and gives me all my rockstar boners. All the little cab has to do is be little. 🙂

 

[cyclecamper]

I once made a small very low-power tube practice amp with a small head and a pair of JBL LE8T-H 8" full-range speakers in a sealed cabinet. It sounded absolutely great; not too loud. Problem eventually was the crappy foam surrounds. I'll never use speakers with foam surrounds again after refoaming hundreds. But how about any semi-pro 10 in a sealed box? Don't be afraid of sealed boxes, especially when you say you want it quiet! But it's all personal...I love the sound of an SVT for guitar or bass, so I love lots of 10's for playing and one or two 10's for practice. I also love the sound of the poly 6.5 speakers (again in sealed cabinets) in the ampeg SVTHE806...I used to play out with 4 of those cabs, 32 drivers, but practice with just one cabinet. But you probably couldn't ask a more personal question and will get disagreement and agreement no matter what you do. The good news is that with only a few watts you don't have the normal worry for hi-fi speakers doing guitar duty, which is burning them out.

But really it's a unique opportunity to use a really good full-range speaker in a good sealed cabinet, going just for great tone. If only that LE8T-H has a cloth surround...two had good treble and bass. I used to have a long monitor with 6 of them, great to practice with. Think full-range. Have fun, good luck. The only problem with most small practice amps is that they also scrimp on the preamp.

 

[Andrew Eckhardt]

"I looked up l-pads and I think I get the idea. My amp actually has an attenuator to cut it from 4W to 1W to 0.1W."

Okay, so now you really got me. Is the 0.1W selection still too loud?

The attenuation could actually be an L-pad or different taps on the output transformer.

You could get one of those 8" ceiling speakers mentioned earlier with a 70V line transformer (some are available w/transformer for about the same price as the raw speaker), and really dial down the output signal.

 

[Keriwena]

0.1W through a typical guitar speaker is about 90dB. That's loud to non-musicians.

I'm going to recommend headphones. I use Audio Technica M30s. I like them more than my M40s (which do sound better with recordings) as they're lighter and don't fall off when I bend down to adjust a pedal. Natch, they need to be closed-back headphones. They may feel weird at first, but just pretend you're in a studio. In fact, it's good to practice playing with cans on.

The problem with levels as low as you're going for is the acoustic sound of the strings drowns out the amp.

 

[flieslikeabeagl]

The problem with levels as low as you're going for is the acoustic sound of the strings drowns out the amp.

Not if you play a solid-body, and play with some finesse, i.e. you don't whale on the poor guitar like Pete Townshend in a bad mood. 😀

I tried an AC4TV (with the 10" speaker) and when pushed into distortion (which is what the thing is intended for) it was indeed too loud for bedroom use at night, even at the 0.1 W setting. Mine went back to the store for a refund because I didn't like the boxy tone.

I currently use a 15 W Fender Super Champ XD, to which I've added an L-pad. With the L-pad I can dial the volume level down low enough to be able to play late at night without disturbing my wife in the next room. I've played both solid-body (Strat and Les Paul type guitars) and semi-solid (ES 335 type) guitars through the amp in this way, and the acoustic sound of the guitar(s) has not been a problem.

One more tip - for really low-volume playing, position the loudspeaker fairly close to your ears. Don't put it on the floor 10 feet away as you usually do. Raise it up and put it on a table or something, so it's within a few feet of your ears, preferably not far below ear level, and pointed at your face. You'll now experience the magic of near-field listening (same thing that makes near-field monitors okay for audio mixing engineers), and you'll find you have plenty of volume and good bass at your ears, while there is very little sound far from the speakers.

As an aside, I was at a Guitar Center earlier tonight. The "used gear" section was crammed with numerous 4x12 speaker cabs and big, powerful guitar amp heads. Clearly, most musicians are finding they have neither the space nor the deaf neighbours necessary to use these monsters, so they're trading them in for smaller, lower-power setups.

-Flieslikeabeagle

 

[flieslikeabeagl]

I forgot to say, over on TDPRI.com (Telecaster forum) the conventional wisdom is that the AC4TV can indeed drive an 8 ohm load, and do so very happily. Apparently the transformer winding ratios and tube plate impedances and current levels actually work out right for an 8 ohm load, rather than the 16 ohm one the factory chose to install.

-Flieslikeabeagle

 

[clengman]

I tried out a couple champ models as I was shopping and I just didn't like any of them. I can see why they're popular. It really does seem like a good all-around package. It just wasn't what I was looking for. I just lurve the simplicity and playability of little my ac4! It requires zero fiddling around. I just turn it on and let it rip.

I tried a little experiment last week. I had a couple very old 3-way surround speakers in my attic with 8 ohm 3" midwoofers. The foam surrounds were toast, so I "fixed them up" with a little duct tape and mounted them in a scrap of 1/2" plywood. It's pretty ugly-looking. I should post a pic just to give throne a good laugh. This was just proof of principle for me. The volume was exactly what I was looking for, and the sound wasn't that bad. I've pretty much decided to go ahead with my project. I think I'll use the hivi m3n drivers I've been looking at. They have a frequency range and T-S parameters that are similar to what I've seen for guitar speakers. I'm pretty sure it'll do what I want it to do.

Just by the way, I'm not sure why so many people say that the ac4tv doesn't have enough clean headroom our it's only good for crunch/overdrive. Set at 4W with the volume at 1/3 to 1/2 and the volume on my guitar rolled off a hair I get gorgeous cleans with plenty of volume for "in the living room" playing. This is even with humbuckers.

 

[sreten]

For the second, I'd like to use a couple small hifi woofers (for instance hivi m3ns) to build a low-volume cabinet for nighttime use. I figure the lower sensitivity and smaller cone area will give me much lower volume compared to the 6" speaker that came in the ac4tv.

I realize these are not ideal speakers for an instrument amp application. It doesn't bother me that they won't sound terrific. I just want it to sound okay and to be less loud.

So... my question is: How do I design the enclosure (In terms of box volume? sealed or ported? port-size?) to get the optimal performance out of these speakers?

Another question: Are there any other 3-4" speakers that might be better suited to this application? (ie should I be looking for high or low Qts? anything else to look at?)

Thanks for looking!

Hi,

1) you don't need two drivers

2) as its small go for sealed

3) oodles of choice for low efficiency drivers

4) IMO if you don't like the 6.5" and that is sealed consider
simply replacing it with a car type reduction ring with :
Aurasound NS525-255-8A 5.25" Paper Cone 8 Ohm: Madisound Speaker Store
or if its open backed chuck in two of these :
http://www.madisoundspeakerstore.com/approx-3-fullrange/aurasound-ns3-194-16a-3-paper-cone-16-ohm/
will be easier in the latter case to make a new baffle, using original covering.

rgds, sreten.

 

[Illusus]

I like using recycled speakers for my small guitar amp builds. Full range speakers from older cars, old radios, televisions, ghetto blasters...etc. the older the better for tone. Something with a paper cone and accordion surround and an alnico magnet should give you a nice tone. A larger speaker used with an L-pad will stretch your mileage. It will retain it's tone when played quietly but will give you the option to rock out a bit when the fancy strikes you. I'm sure you can find something at your local Salvation Army. They will cost next to nothing, no shipping or waiting and cheap enough to experiment with many different drivers if you build a removable baffle. You can make several interchangeable baffles, each with a different driver. I find this approach is high on fun factor too. Playing speaker hunter is a fun way to spend a Sunday. YMMV...I'm becoming an old nerd 😀.

A little headphone amp and headphones is a good recommendation for your situation.

 

[clengman]

Hi,

1) you don't need two drivers

2) as its small go for sealed

3) oodles of choice for low efficiency drivers

4) IMO if you don't like the 6.5" and that is sealed consider
simply replacing it with a car type reduction ring with :
Aurasound NS525-255-8A 5.25" Paper Cone 8 Ohm: Madisound Speaker Store
or if its open backed chuck in two of these :
Aurasound NS3-194-16A 3" Paper Cone 16 ohm: Madisound Speaker Store
will be easier in the latter case to make a new baffle, using original covering.

rgds, sreten.

I always appreciate input, thanks! Let me see if I can explain my thought process a little better. The primary reason that I'm thinking about a pair of drivers is impedance matching. My amp puts out maximum 4W into 16 ohms. Most of the drivers I see are either 8 or 4 ohms. Actually the second one you recommended is the first 16 ohm hi fi driver I've seen. I have added that one to the list I'm considering. Regarding the first driver you recommended: since it's 8 ohm, the amp will be outputting double the power that it would be into a 16 ohm load. I'm pretty sure a 5" 8 ohm speaker will be louder than the 6" 16 ohm speaker I'm using now.

As for item two: I'm not necessarily going for small. This rig is very rarely going to leave the "conservatory." My design right now is for a large 1x12 or 2x10 (30"h x 22"w x 15"d or thereabouts) and a matching combo to set on top of the big cabinet. The combo will be around 15"h x 20"w x 15"d and will contain both the original 16 ohm 6" speaker and whatever low volume speaker solution I settle on. It'll be switchable between these two speaker configurations. Anyways... I'm thinking of this more as a piece of furniture for the music room. It doesn't have to be small or transportable.

I am thinking now that if I choose something with qts around 1.0 (similar to a guitar speaker) I can put it in a largish box and play around with open, partial-open, sealed options just like I plan to do with my large extension cabinet with real guitar speakers. Does that make sense or is there some other factor I'm missing?

Finally... Thanks for pointing me toward the madisound website. It has come up a few times in my searches, but I hadn't really done much browsing of their inventory. They do have a lot to choose from.

 

[clengman]

I like using recycled speakers for my small guitar amp builds. Full range speakers from older cars, old radios, televisions, ghetto blasters...etc. the older the better for tone. Something with a paper cone and accordion surround and an alnico magnet should give you a nice tone. A larger speaker used with an L-pad will stretch your mileage. It will retain it's tone when played quietly but will give you the option to rock out a bit when the fancy strikes you. I'm sure you can find something at your local Salvation Army. They will cost next to nothing, no shipping or waiting and cheap enough to experiment with many different drivers if you build a removable baffle. You can make several interchangeable baffles, each with a different driver. I find this approach is high on fun factor too. Playing speaker hunter is a fun way to spend a Sunday. YMMV...I'm becoming an old nerd 😀.

A little headphone amp and headphones is a good recommendation for your situation.

I wish I had more time and patience for scavenging vintage stuff. That definitely seems like it'd be a good way to go, but I think I'm more likely to just buy something new off the shelf. The majority of my time on this project is going to be devoted to woodworking. I have tons of 90-year-old clear pine 1x4 bead board that I scavenged when I remodeled the third floor of my house. I'm jointing it by hand and gluing it up for panels for cabinets. I think it may take a while. 🙂

I know a headset amp would be easy and good for practicing without bothering anybody, but it's just not as much fun, is it?

 

[sreten]

My design right now is for a large 1x12 or 2x10 (30"h x 22"w x 15"d or thereabouts) and a matching combo to set on top of the big cabinet. The combo will be around 15"h x 20"w x 15"d and will contain both the original 16 ohm 6" speaker and whatever low volume speaker solution I settle on. It'll be switchable between these two speaker configurations. Anyways... I'm thinking of this more as a piece of furniture for the music room. It doesn't have to be small or transportable.

I am thinking now that if I choose something with qts around 1.0 (similar to a guitar speaker) I can put it in a largish box and play around with open, partial-open, sealed options just like I plan to do with my large extension cabinet with real guitar speakers. Does that make sense or is there some other factor I'm missing?

.

Hi,

That box size is massive for a 2x10 or 1x12, I you won't find any
drivers for guitar that would remotely need such a large box.

Your combo also seems pointlessly massive, why ?

A very small open backed cabinet will have no bass, inevitably.

Just take a look at classic guitar cabinets and don't stray
too much from them, most of them are good compromises.

That 8 ohm 5" driver will likely not make as much noise as
the 16 ohm 6.5" driver because it has far more excursion
capability and bass which reduces efficiency.

IMO that 5" does have a response somewhat like a guitar
speaker, and should work well in a small sealed box, YMMV.

Your amplifier won't output 8 watts into 8 ohms, if its optimised
for 16 ohms it will put out less into a 8 ohm speakers, say 3W.

You seem to be trying to cover all bases. IMO you can't.
Keep it simple and do it well. Choose open backed or
closed and get appropriate drivers.

Also note 4 drivers compared to one driver will be 6dB louder,
i.e. a 4x10 compared to a 1x10 with 4W sounds like 16W.

rgds, sreten.