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

[jwc]

Mike. That last paragraph is a good idea. I didn't think to do it like that. I can see how that could be a problem. Man....lots more to the t-nut process than I thought.

The only bummer of not using the driver plates is the limitation I will have with drivers. If the kappa pros don't work...I would have liked to try something else....such as the Pioneer driver from Parts express with the T/S parameters close to the AES paper.

jc

[DrWho]

If the mounting holes on the different drivers don't line up you can

just rotate the driver a little bit and mount it to a seperate set of

holes.

That said, most same diameter drivers I've worked with have the same

bolt patterns - even if it's from different companies. I'm not sure if

T-Nuts are something you can do after the fact, so maybe you might see

if you can get the bolt pattern for the Pioneer driver and pre-isntall

T-Nuts for the application. You shouldn't have to worry too much about

extra holes because the gaskets will cover them up.

[jwc]

Mike.

I had thought of that. However, T-nuts can't be done after the fact.

This is what I'm thinking. Use hole pattern for the Kappa. If woofer doesn't work for this application, will try to use same hole pattern for pioneer or make and MDF 1/2" driver plate to mount in the existinf tinut holes and the driver plate will have new tnut hols for the pioneer. Lots of T-nuts but will work.

This will work also if I decide to stick a 12" passive in there for the bottom "driver". Now I'm really gettin crazy. The Pioneer driver and the Dayton passive are cheap so no biggie.

Hey...here is a fun thing that I wish you would do for me only if you have the time Mike. Just for experimentation purposes, can you plot on WinISD what 1 passive and one Kappa or Pioneer will do in the jub cabinet.

jc

[DrWho]

oh gosh, the plots I posted were already pulled outta my butt and you want me to pull some more crap out? [][][A]

But seriously, you would lose 6dB all around (half as many drivers and

the impedance would double). You would probably lose some HF extension

as well and the vertical polars would go to crap. The tuning point

would drop from 44Hz (two PR's) to 34Hz (one PR).

I do remember Roy mentioning that he designed the Jubilee as two

smaller horns that are stacked on top of each other. I would very

highly recommend splitting the top and bottom horns so that they can

both behave independantly of each other. When you get rid of the second

active driver you pretty much screw up the loading on the horn and the

single driver would see a faster flare rate - which I think would

result in crazy dips and peaks in the frequency response (You would

have to allow the drivers to share the same rear chamber of course).

I'm not sure that's the best way to describe it though but I can

visualize what I'm talking about. By going this route I don't think the

response would be as bad.

An interesting design approach would be to build a bunch of half

Jubilees such that you can arbitrarily change the top and bottom panels

to allow for any number of bins to be attached. It'd be cool as heck to

do four halves: going up you'd have passive active HF horn active

passive. [H] Or maybe do three halves: passive active active HF horn.

The point being the flexibility in case something is awful.

This seems like a rather expensive approach though - considering that

if you wanted more bass you could probably start with a slightly

different design and use drivers that naturally dig lower, but then you

would probably want to put passives on that design too...

Anyways, the next post will have the plot comparing the original with 2 active and 2 passive (purple) and the effects of moving to one driver with one passive (blue). And then is the stock Jubilee for comparison (yellow).

I think it would be slightly representative of the end result, but I

would anticipate more HF roll-off and a wider dispersion up high. I

have a feeling you're gonna end up going 3-way so crossing over on the

low side probably isn't going to be a huge deal for the squaker (since

it won't have to go as high).

One thing I've seen when modelling horns is that you can't arbitrarily

change the rear cabinet volume...I think DMan refers to it as

"reactance nulling" or something to that effect. It seems there is an

optimum volume that results in the most efficiency down low at the

corner of the response - and sometimes going bigger on the rear volume

actually results in less output (so that peak down low might drop down

a few dB).

So in the end I don't think you're gaining very much. You could

actually achieve the same results by EQ'ing the normal Jubilee (note

that the output at 40Hz is essentially the same). The stock Jubilee

would then have a good 10dB less distortion and none of the group delay

stuff from the passive.

[DrWho]

Again, that's:

Yellow = Jubilee

Green = Two drivers, two PR's

Purple = Two drivers, one PR

Orange = One driver, two PR's

Blue = One driver, one PR

(I decided to add a few more since it's easy to do)

[DrWho]

And then here's the sensitivity plots:

Yellow = Jubilee

Green = Two drivers, two PR's

Purple = Two drivers, one PR

Orange = One driver, two PR's

Blue = One driver, one PR

[jwc]

Mike. Don't forget, I'm a Urologist and comments with "butt" and "crap" in them may come across as something I'm am an expert with.

JUST KIDDING!

OK. I agree with all of that post and aware of the things you pointed out. Yes...a bunch of short and wide horns stacked would be a good way to tinker with it. Those plots are helpful eventhough you pulled them out of your Butt. We will see how accurate they are soon enough.

Some results for tonight. Bought #10 x 32 5/16 T-nuts. Pounded some in some 3/4 inch MDF. Placed a #10 x 32 1 1/4 inch machine screw with a lock with a #10 lock washer and washer. Drilled a hole just the size of the t-nut although slightly smaller than 5/16.

So what happens? The screw isn't long enough for the Kappa pro. The mounting rim on the driver is too thick....again...thicker than a K33. Will run to HD tommorrow and get a 1 1/2 screw.

So the below picture is of the front two panels with ramps. I win the DUFUS award for not cutting out enough ramps....see the one missing. Oh well. These aren't screwed and glued on yet.

Guess what! The holes for the driver aren't close to any ramps. Excited about this....no t-nuts under ramps.

jc

[jwc]

stacked

[rigma]

You can use these threaded inserts that can be installed from the speaker side. I have used them in hardwood and ply with great success. Never had one pull or back out. I have not used them with MFD so you would need to ask about that but I would think it would be fine. You just drill the right size hole and screw them in with a allen wrench.

rigma

http://www.stafast.com/products/inserts.html

http://www.ezlok.com/InsertsWood/softWood.html

[jwc]

I considered that idea. But you are right...MDF?...could be a problem.

The t-nut thing worked out great. I did stick a little gorilla glue there. Only a little as this stuff expands. I didn't put it in the hole as I was afraid some of the glue would get on the threads.

Dennis was right. Test all the t-nuts with a screw to make sure they are "ok". One of them was a dud and I would have been bummed if I would have found out later.

Now the predrilled holes weren't 5/16. I did them a little smaller so that the t-nut would fit tight. I also wanted to keep the t-nut from going in crooked.

Hammered them in and then ran the screws through all of them to "pull" them into the baffle. Did them tighter than what I would do a driver.

Again...used the 1 1/2" screw. I think 1 1/4" will work with a K33.

jc

[jwc]

Here is the baffle side opposite drivers.

[jwc]

OK. Here is the back of the front board with the ramps and splitters mounted. Also is the first turn on one side with a reflector. Here you go Dana!

Now you can also see one of the braces. I would recommend placing all braces on the "braced panel" prior to mounting the panel. There will be a total of two on that one.

Good ole Elmers wood glue and the usual #6 x 1 1/4 screws.

jc

[jwc]

Another view

[jwc]

Ok. Here is the front side of the front board. All those ramps were glued and screwed. The splitters have a bunch glue only and shoved in place.

All the above will be "sealed" and small spaces "filled" with rubber nails. They will also get more screws on the other side when I place the baffle.

The screws were flush mounted. Will fill later...much later after testing (if I like the results).

[jwc]

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

[DizRotus]

jc said, "Mike. Don't forget, I'm a Urologist . . . "

jc is that true? If so, is it normal to still wake up with back (kidney) pain every morning three weeks after that hideous 10" pigtailed stent was removed?

BTW, I heard that the uertal stent was invented by that guy who flew the kite with the key in the rain. It's known as a Urethra Franklin.

But seriously, I've followed your project with great interest. When time, money and residual kidney stone pain permit, I plan to do something similar. Until then I've got two NIB Crites CW1526 woofers that you could try. To satisfy my curiosity, Id be willing to pay the freight one way if you pay to return them when done.

Regards,

Edited April 19, 2016 by DizRotus

[jwc]

Now that is even funnier.

Yep. Still can hurt. May have a dried out blood clot in the ureter somewhere. Have seen it take that long to "get back to normal".

Just put one up a lady 4 hours ago with a kidney full of stones. Now she has a temp of 102. I may have to send her to ICU. Not much sleep for me tonight.

Enough Urology before people get grossed out. I've had people start asking questions about details and then get nauseated and faint. Especially men in 20's and 30's.

Diz. Those are 15" woofers. I need 12". I have some in some "tall Cornwalls". It would be nice to put those in a "low rider" sub cabinet. People chit chat about a horn sub for the jub. I may take you up on that offer for another project.[<)]

jc

[DizRotus]

jc-<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

As soon as I posted the offer for the CW1526s it occurred to me that you need 12 inchers. Since Ill not get around to using the CW1526s any time soon, the offer to lend them still stands.

FWIW, in my past life I defended med mal cases. Now as a small business owner I avoid lawyers as much as possible. Thanks for the reassurance regarding the lingering pain. Normally free advice is worth what you pay for it, but in this case its comforting to hear that its not an unheard of situation. If I werent getting slightly better every day Id be concerned.

When it became necessary to involve a Urologist to manage the kidney stone problem, my internist suggested the practice of Drs . Peters & Gonzales. When Dr. Gonzales first met with me in the hospital I was somewhat confused . . . there was nothing wrong with my Gonzales. :-)

[DrWho]

A Urologist eh? Here I thought you were a proctologist...

So would a 15" driver physically fit in the cabinet? I've done some ratios on your pics and it looks like it would be real close. More a morbid curiousity question than anything else really...

Btw, the woodworking looks very nice so far - well beyond my abilities.

[jwc]

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