Speaker suggestion needed!

[boodle]

Hello, new member here.

I am a guitar player (don't start throwing things...I have never even made a bass player joke before... except that one about how many bass players it takes to...well, never you mind that one) and I am getting more into bass.

I recently purchased an SWR Basic Black combo online based on a memory of one a friend has.

It is 120W 1-15" with a tweeter crossed at 5K. If you plug in an extension cab (8 ohm) the power increases to 160W (total 4 ohm load) for increased headroom and more SPL when needed.

I am interested in putting a new speaker into a ported 1-12 that I have that is currently housing a Celestion G12K-85. A fine guitar speaker, but it can't handle significant low end without distorting in very unpleasant ways.

So, here is the question...what 12 can I put in that cab, if any, that will compliment the 15 and tweeter in the BB? I thought about cutting a new baffle in the 112 to house 1 or 2 10" speakers, but the baffle is dado jointed into the body of the cabinet, so I am stuck with the 12" baffle.

I would assume that there is a reason that bass players usually use 10's and 15's and tweeters most often and don't use 12's unless it is a small cab or combo for smaller gigs. In my relatively few searches of cabinets I haven't seen a 12 and a 15 used together ever.

I would rather not buy another cab if I can avoid it and just get a (hopefully cost effective) 12 that will augment the 15 and tweeter.

Any and all thoughts welcome.

[will33]

Would need the internal measurements of the cabinet and the ports to make any useful suggestions.

[boodle]

Will33, thanks for the reply.

Here are the deets of the cab:
Interior volume: 1.38 cu.ft. (8.5"X19"X14.75")
3" round port X 3.75" length

If online calculators are correct, it is tuned to 48 Hz.

So, is it a viable bass cab with the Basic Black's 15 and, if so, any speaker suggestions?

[GrowlerBox]

Just off the top of my head, that looks way small for a 15" (or a 12" for that matter). I'll be interested to hear from the designers what they'd do here.

[billfitzmaurice]

Originally Posted by GrowlerBox

Just off the top of my head, that looks way small for a 15" (or a 12" for that matter). I'll be interested to hear from the designers what they'd do here.

Correct. Just about right for many tens, though.

[boodle]

Thanks for the replies. It was originally a guitar cab. It has a cutout for a 12" and it is front mount. I would consider cutting a ring that mounted a 10" in the original 12" cutout if that is the best solution. I would love to hear the "why's" of that being the best solution as I am a physics teacher and I love to hear the "why's".

[billfitzmaurice]

Originally Posted by boodle

I would love to hear the "why's" of that being the best solution as I am a physics teacher and I love to hear the "why's".

Understanding Loudspeaker Data | Eminence Speaker
LinearTeam
The Speaker Building Bible - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com

[boodle]

Bill,
Thanks for the links. I have done some reading and have a decent overview of the variables involved. Most accurately, I would say that I have an increased intuition of the problem at hand, but since I lack experience in speaker design, I lack any clear direction as to a starting point for drive choice in my particular circumstance. (My experience is more in the electronics of guitars, amps, and pedals.) FYI, I could not get to the LinearTeam site at work. Will read later.

So, given my existing box (data above) can you point me in direction to start ruling out drivers? I am happy to just concentrate on 10's. (I can modify the 12" cutout to take a 10" with a simple ring.)

It would seem that a calculation of Qtc for a 10 in my cabinet would be a place to start. Is it possible to get a Qtc of .707 from a 10 with my port and internal dimensions? If I have understood what I have read, I need to select a drive first and then calculate (based on the reading about shareware and subsequent calculations). If I have understood, a Qtc of 0.707 gives me a decent shot at having a cabinet that will reproduce a broad frequency spectrum without undue boxiness or undefined bass.
(I also understand that one variable will not guarantee that the sound will be deemed "good" by me.)

One final note: the Basic Black showed up yesterday and I have played with it some. I compared it alone to both cabinets together (with the Celestian G12K-85) and liked the sound of it alone better. Too much mid content with the 12" and less bass coherence. As expected, it did have more headroom. Actually, a surprising amount more headroom and volume. More cone, more air, more SPL/Watt.

Long response, so thanks for your patience. Any help is always appreciated.

Tim

[billfitzmaurice]

Originally Posted by boodle

It would seem that a calculation of Qtc for a 10 in my cabinet would be a place to start. Is it possible to get a Qtc of .707 from a 10 with my port and internal dimensions? If I have understood what I have read, I need to select a drive first and then calculate (based on the reading about shareware and subsequent calculations). If I have understood, a Qtc of 0.707 gives me a decent shot at having a cabinet that will reproduce a broad frequency spectrum without undue boxiness or undefined bass.

Vented cabs don't use a Qtc calc.
The way to choose a driver is to model it in WinISD Alpha Pro, adjust the vent and box size for the desired low end response, check the maximum SPL chart and maximum power charts to see if the displacement limited power handling is OK, and check the manufacturer driver data sheet SPL chart to see response above 200Hz.
IMO adding a ten to augment a 15 when it's only a 120w amp won't accomplish much. But that depends on the fifteen, you'd be surprised how many of them are displacement limited to 75 watts or less.