Keystone Sub Using 18,15,&12 Inch Speakers

[Djim]

Hi Art,

The dip around 55Hz is the result of the usual modelling errors. The problem is the peak around 40Hz. In your measurement it is almost flat between 55 Hz down to 42 Hz (+/- ½ dB). If you compare with the Xoc1-TH18 for instance you see a similar error, the measurements rolls of earlier.

You can correct the cone volume like TB46 did (I'll use his inputs). If you do so, you also have to correct the pathlength since adding a value in ATC needs a correction in Horn Segment . You also need a correction for the raising inductance of the VC. In other words an inductance correction related to frequency.

Of course the Response you will get is only usable in the lowest part of the response to see what happens around the low corner. As you can see the bump at 40Hz is gone and also the dip at 55Hz, in a similar way like your measurement.

[GForce2]

Hello Art,
I stumbled onto a thread on SoundForums that led me to this Keystone project. I'm still reading through the thread, but I think I'm going to take it on. I'm wondering what your current favored 18 is? I'm leaning toward the B&C 18TBW100, as I read (your post) that it's a good ceramic substitute for the 18SW115. Unless there's something else you recommend. Does the design dictate 4 or 8 ohm, or is that up to me? The largest amp I envision using would be the QSC PL380, which is 1250w @8, or 2500w@4.

This looks like a very straightforward build. How much time are people spending?

Although I built a house, I've never built a speaker cab. Are these cabs held together with super tough glue and trim nails, or is there more to it than that?

Thanks again for sharing this project!

Grant

[weltersys]

Grant,

The B&C 18TBW100 would be a good lower cost alternative to the 18SW115.
In either case, I'd go with the 4 ohm version, 2500 watts is still not as much power as they will take. I bridge a Crest CA9 into each of mine, probably around 2-3K watts peak, and I'd like another 3 dB of power.
Langston Holland bridged a QSC PL380 (about 5K + peak) in to his 4 ohm DSL TH-118, and said that really got it going. Josh Ricci put around 10K into his B&C 21SW115 before tearing up the cone...

Although trim nails and glue are probably adequate, I always use screws and yellow glue (Tightbond II or Elmer's) for road cabinets with four horsepower kicking around inside. With as warped as the Aruca plywood I generally use is after making it from the tropics to the high desert, the screws (and a ton of clamps) help pull the wood back in line.

Build time varies with experience. I just built a tapped horn sub similar in size and complexity to the Keystone for my back yard, it took about 9 hours including applying wood filler, sanding, two coats of paint, stretching grill cloth, wiring and loading speakers.
Building a pair (or more) of speakers compared to one can save a little time per cabinet, but I'd figure estimating around 20 hours for a pair would be reasonable since you already have wood butcher skills but no speaker cabinet experience.

Art

[maxo]

Originally Posted by tb46

Hi Art,

I added your comments in note form to the drawing, if you find anything else, or want to add anything let me know.

Regards,

oliver no drawings for the dual lab 12... how do u fit those in to the baffle...??

[tb46]

Hi maxo,

The internal width was 25" (or so, depending on the wood thickness), and they should fit nicely side by side where the 18" is in the drawing.

Regards,

[maxo]

Originally Posted by tb46

Hi maxo,

The internal width was 25" (or so, depending on the wood thickness), and they should fit nicely side by side where the 18" is in the drawing.

Regards,

ic,
so if you look at the cab facing the mouth the drivers must be side to side or
one behind the other
Max.

[weltersys]

Originally Posted by maxo

ic,
so if you look at the cab facing the mouth the drivers must be side to side or
one behind the other
Max.

Max,
I made an adapter plate to fit the two 12" over the existing hole cut for the 18".
Looking at the cabinet with the 45 inch dimension vertical, the two Lab 12" were mounted side by side horizontally.

I would recommend the B&C 18TBW100 over a pair of Lab 12, better performance and less $$ and weight.

Art

[maxo]

that bc driver looks great... hey the keystone what kind of design is and what are the diference with the bjorno 3015lf tqw sub published here...just wondering as they look similar inside

[weltersys]

Originally Posted by maxo

that bc driver looks great... hey the keystone what kind of design is and what are the diference with the bjorno 3015lf tqw sub published here...just wondering as they look similar inside

The Keystone design would commonly be referred to as a tapped horn.
Bjorno is very giving with simulations, and has posted hundreds of designs, you would have to link me the one your question is about for me to say what the difference is.

After hearing the gross distortion the Eminence 4015LF had when driven near Xmax in the Keystone, I would not want to consider the lighter 3015LF for a low frequency, high power TH.

That said, harmonic distortion makes a speaker sound a lot louder than it is, many seem to enjoy it.

[maxo]

Originally Posted by weltersys

The Keystone design would commonly be referred to as a tapped horn.
Bjorno is very giving with simulations, and has posted hundreds of designs, you would have to link me the one your question is about for me to say what the difference is.

After hearing the gross distortion the Eminence 4015LF had when driven near Xmax in the Keystone, I would not want to consider the lighter 3015LF for a low frequency, high power TH.

That said, harmonic distortion makes a speaker sound a lot louder than it is, many seem to enjoy it.

this is the one
3015lf TH @ 35-40hz but only 20" deep help