Picking a Speaker for an Existing Cab

[Guitar_Steve]

I may not be phrasing my search query correctly, as I'm sure there's information on this subject out there on the Google, but everything I turn up involves building a speaker box around a speaker and not the other way around.

Is there a program or an easily referenced spec sheet where I can input the specific internal dimensions of my cabinet and get suggestions for an optimal speaker to use in it? My knowledge on the subject is a little lacking. I've built cabinets based on suggestions on Eminence's website for a given speaker, but I've never gone so far as to create models in winxd, et. al.

So, the cabinet in question is an Avatar single 12 cube. It's a guitar speaker cabinet, but it has a closed back, and four 3-4 inch diameter ports in each corner on the baffle. I'm not currently able to take measurements, but from memory, I think it's somewhere around 12-13 inches cubed internally with some bracing.

I only intend to use this for bedroom-volume practice or the occasional acoustic songwriting sessions with my band, but I would like it to be efficient and capable of louder-than-bedroom-volume use. Possibly good enough for mic'd recording.

Sorry for the long post for a simple question. I don't mind suggestions on which speaker is best, but I would ultimately like to learn best practice for finding an optimal speaker given specific cabinet dimensions.

 

[Guitar_Steve]

Does anybody have any input on this?

 

[Redbrangus]

The actual answer to your question is no, to my knowledge, there is no program or app in which you can input a box internal volume and port data and have it output recommendations for a specific driver. But if you think about it, there are only a few manufacturers that make appropriate drivers, and each of them makes only a handful of different 12-inch drivers, of which, only a couple in each line are likely candidates. So how hard is it to model 6 or 8 different drivers in your box? That said, here are a couple of observations: you really need to get accurate measurements; if it is indeed only about 1 cu.ft., that will narrow down your options. I have difficulty imagining a box with 1 cu.ft. internal volume that still has room for 4 x 3-4 dia. ports. And are they just ports, or are they ducted ports? And if so, how long are they? There is software out there that will at least tell you to what frequency the box is currently tuned to if you have accurate internal volume and port measurements, I think, but we need other TB'ers to chime in with that.

On that subject, a vented, closed-back box sounds more like a bass cab than a guitar speaker to me anyway...have you tried playing your bass through it with the speaker that's in it? What does that sound like?

 

[Guitar_Steve]

I looked at it yesterday on my way out the door and it is for sure larger than 12" cubed. I'll get a solid measurement this evening. The ports are just holes in the baffle. I'm 90% sure that it's a guitar cab, labeled Avatar G112. It has a guitar speaker in it, and a cursory search in the webs found the exact one I have (see attachment). So I guess the answer is to pick a few speakers and model them with my cab dimensions?

 

[basscooker]

Yeah, sorry you just gotta put in the time and model the likely candidates. Once you have actual dimensions, the field will narrow a bit because most spec sheets at least give you a starting point on recommended cab volume.

"Ported" guitar cabs aren't unheard of, just not common. I admit that whenever someone says "guitar cab" and then goes on to mention ports; my first reaction is to assume the box was designed as a bass cab. Is there any evidence that the ports were not originally there?

Anyway, budget? Willing to duct the ports or seal some (or all) of them?

Retrofitting a cab can result in "ok"; but with sacrifices. Designing or using a proven design more often provides a better result even though there are trade-offs and compromises in lieu of sacrifices.

No one says you wont get good results... It's just fewer headaches to start with a driver and build around it, albeit more time consuming.

 

[Guitar_Steve]

Maybe I ought to check with Avatar to see what their specs are. It was my understanding that GXXX labeled cabinets are guitar cabs. This doesn't look like it was modified after the fact. No specific budget. Whatever the cost of a 12" speaker may be. And of course I'm willing do any modifications up to building an entire cab around a speaker of my choice. My initial idea was to seal off the ports and make it a sealed cab, but whatever works.

I'll take measurements and post some pictures this evening. Maybe it is a bass cab afterall and there's already a speaker out that for which it was designed

 

[basscooker]

Good approach, really. But with the stated purpose in your OP, the best question hasnt been answered yet, though asked: how's the cab as-is? For your bedroom and a quiet song-writing jam, you might be golden with what you already have.

I second the idea of sealing it up if it can't work as it is now. There's surely a good bass 12" for about 1cuft sealed.

 

[Guitar_Steve]

It works for quiet playing for sure, but the tone isn't very mid focused. Also it will fart out at slightly higher volume. The speaker in it now is a Celestion G12T-75, which I think the previous owner just slapped it in there to sell it. I got it off of my guitar player in a trade because he needed a better cab than that one, which he bought solely because it was red.