Bass horn ideas again. A possible build. Need criticism.

[mark1101]

JC,

You really moved fast on this project. How would you rate the build difficulty thus far? It looks like you are sailing right through.

[jwc]

Actually. It really isn't that hard. I think the "back" may be a challenge.

What you see there in the garage is what I did over two hours. You have to realize though that the "inners" of that cabinet has been on my mind now for a couple of months. Also, I have a certain way of doing things that are a little automatic and swift. Such as predrilling holes for the #6 screws and then modify the hole for a "recessed" screw so that is buried. I could have the dern thing together in a days time if I had that kinda time.

You guys would laugh at how I do stuff if you watched me. I use crude tools and techniques. I don't even have a shop per se. The products are typically overbuilt.

Mark. Givin more thought of coming this way? I got my Blueberry Extreme this weekend. My two channel set up now is AH! CD, Music Hall MM-5 TT, Blueberry X, McIntosh Mc252, and the dbbs.

Let me know

jc

[D-MAN]

I have the Eminence Kappa pros on hand and the cheapo Pioneer woofers coming.

Anyone want to take a stab at which ones will work best?

I won't get to work on this much this week. October is the month of "gettin er done".

jc

Is this a trick question?! Of course the Kappa-Pros. You should have saved your money with the Pioneers. Or better yet, just send it to me, since you clearly have more than you know what to do with!

But seriously, the power bandwidths will be quite different between the two pairs. It depends on the "sound" you prefer, but I'll bet that you'll end up preferring the Kappas.

DM

[jwc]

Dana.

The reason I got those Pioneers is because Roy reinterated the importance of a Driver with T/S parameters like the ones in the AES paper.

The Kappas are smokes and blows better than the Pioneers in general. T/S much different. However, I would like to prove a point. The Pioneers aren't that expensive.

I read through BFD's thread again this weekend and I still don't know what drivers he chose. That thread died.....darn shame.

[mark1101]

JC,

I still plan to come when my son has his track meets. Can't remember the dates right now, but we discussed.

Yeah.....your work looks pretty crude....no good tools......yeah[] If your not careful you're going to dull your scalpel.[]

My grandfather used to say that it's easy to do good work with the right tools. The real craftsman is the guy that can do it without them.

So......what do you think of a tube front end compared to s/s?

[jwc]

I'll email you regarding those dates. I saved the email. I just realized those meets aren't this month but next month.

The Tube pre is definately different. It is taking me a little to get used to. I think I am going to like it though. I don't want to throw too many opinions out there just yet but I will say that there definatley is no harshness or too bright. I am happy that there is minimal hum or hiss too.

jc

[D-MAN]

T/S "matches" don't always sound the same. The specs are made up from ratios, and even though the number might be the same, the underlying specs that made up that value can be wildly different, especially total Q!

DM

[D-MAN]

Sorry to say that there is no way a 15" will fit. Maybe in Gil's "Base of the Earth" cabinets.

The baffle will only fit a driver 12 inch. The drivers are typically 12 1/8. The internal width of this baffle is 12 1/4. Tight quarters huh?

Honestly, this "w" style cabinet can easily be adjusted to fit two 15" or two 18" drivers.

Gosh...if I just had the time....we could try all that out.

jc

I wouldn't say "easily". I've designed 3 different 15" twin horns now, and I'm pretty much sick of it!

It depends on the throat size/Vb (and hence, the drivers) you want to use, so basically one-size does not fit all!

However, I think I've pretty much covered the gamut of available drivers appropriate to the application!

I expect them to be around 108+db or so.

DM

[jwc]

Let me clarify my point of "easily". This is just from a construction point of view.

On Graph paper, I scaled out ~140cm horns for 15" and 18". Then calculated using different throat sizes to get me to 140cm horn length. Yes I would then have varying Fc depending on the throat. Can't say i'm sick of it but I could be doing it all wrong. Fun to think I might be doing it right.

Yes, The driver dictated the throat. Say for instance the Eminence 18" Magnum HO would require a 105 sq inch throat but its buddy Eminence 18" Magnum LF would need to be much smaller....thus a much longer horn. The Eminence 18 Sigma Pro and Eminence Magnum HO seem to want the same size throat and could be "grossly" interchanged.

The dual Em. 18 Mag HO in a "w" horn would be a beast. Only about 6 inches wider than the Jubilee. Could sound like crap too!

You know, come to think of it, I thought at one point I calculated the 12 kappa pro calling far a smaller throat than what was in the AES paper. I'm at work....not in front of me.

Oh well. All in all...you can tell be my posts that probably the "experimenting" is getting a hold of me and logic slides a little.

jc

[DrWho]

I've heard from quite a few people that linear scaling of horns never works...like you can't just arbitrarily change every dimension by the same factor to make space for larger drivers.

[D-MAN]

Scaling works if everything is scaled according to wavelength, i.e., you can scale up and down as dictated by the change in wavelength (longer or shorter).

However, the thing to remember is that the MOUTH SIZE doesn't change for changing throat sizes (drivers) unless you change the Fc (wavelength, etc.). So technically, unless scaling for a different Fc, the scale thing doesn't work.

Anyway, the whole thing goes out the window when you change throat or Vb by itself and retain the same Fc and mouth size, because the channel lengths and widths change.

If you want to size competively with the Jubilee, that is a whole other can of worms...

The geometry has a limit as to what the channel widths can be supported, and so does the mouth size. A large throat and/or larger channels cannot fit into the folding geometry.

The whole thing could be made bigger, of course, but who wants that? There is a point of diminishing returns - why not settle for the dual 12" driver Jubilee, if you have to make too many compromises?

Where that point lies, I will leave to you...

My design criteria was to stay in the same footprint as the original Jubilee as closely as possible. It can be done, but's a pain (I won't say exactly where)!

DM

[jwc]

Some updated photos. I actually had about an hour and a half to work on them tonight.

Here is first turn with me mounting one reflector. 4 braces are mounted. the reflector is bunches of glue....no screws.

[jwc]

upclose

[jwc]

Here is the baffle with first turn panels mounted. The opposite woofer side is up.

[jwc]

Here is the same thing turned over to show where the woofers will be mounted.

[jwc]

Notice here where the lines are for the ramps. Now the ramps aren't on this side. This is the woofer side. The reason they are drawn there is to show that the woofer holes/t-nuts aren't lined up with any ramp.

Also, this will serve as a guide as to where I will predrill some holes when mounting this to the front board with the ramps. Therefore, this will screw and glue onto to ramps. I will need to bury those screws and cover with rubber nails. Then smooth out slightly with sand paper in order to keep a good seal of the woofer with the baffle.

[jwc]

I guess the next step is to start layering the acoustic paint. I special ordered about 4 cans.

Then I can stack the two.

Good night

[jwc]

Did this during my lunch. This is the part that will be the most difficult

[jwc]

.

[bodcaw boy]

so THAT is how one goes together.....

berryroy boy