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

[D-MAN]

JC's will sound better due to the 45 degree fillets at the first 90 degree turn.

One would think.

However, I've been thinking about this particular case... bear with me here...

I am suspicious as to why PWK and Roy would have used full-channel reflectors on all but the front corners of the Jubilee, exactly like the La Scala. Since Roy has never commented on this, left to my own devices, I have come up with some possibilities.

1) It's clear that its not an oversight. PWK did it more than once, and in both cases, it was prior to a change in flare rate.

However, the flare rates in question are opposites, in effect - that is, the LS second flare rate is the higher of the 2, i.e., less reactance, and in the Jubilee, the second flare section is the lower of the 2. The one thing both instances have in common is that a change in reactance follows the non-expanding "capacitive" section. I decided that in the case of the LS, the non-treated fold is specific to reducing the upper band pass, allowing for a 6db 1rst order slope to be used. However, the Jubilee design seems to NOT want to limit the upper bandpass, or does it?...

2) the corner in question occur just before changing flare rates (to a lower one) and after the turn, a non-expanding columnar "connector" section is used which transfers the acoustic resistance from one end of the column to the other end basically intact (discounting losses due to viscosity), and the more constricted flare rate following means an increase in reactance is apparent at the "throat" of the second flare section.

I suspect it has to due with the capacitance of a semi-treated (radius-type reflector) fold which reduces reactance at the throat somewhat and also tends to reduce the upper bandpass as a by-product. I suspect it has more to do with the capacitance at the throat of the second flare rate to match the impedance naturally caused by the subsequent tighter 32 Hz flare rate.

Essentially, it's an impedance-matching device between horn sections of differing flare rates. The question remains, though, does the Jubilee need to restrict any upper bandwidth frequencies? The possibility exists that it may reduce a tendency for "peakiness" in the upper response.

Now, the effect of a full channel reflector at the fold SHOULD maintain the waveform pahse and frequency bandwidth virtually intact around the 90 degree bend. The diliterious effect of hitting the side wall in the 32 Hz flare section will THEN reflect the waveform all over, so what is gained by the full channel reflector is now lost...

So I'm to the point where I think it doesn't actually MATTER which approach is going to work better. I would guess that it is possible that there would be NO HEARABLE DIFFERENCE in the case of the Jubilee.

To further support my case, I have attached an extract from the Jubilee paper, which clearly indiocates that PWK and Roy originally used a full-channel reflector at the front corners. On the Jubilee it was specifically left out...

I find it infinitely interesting that they DID use a radius reflector instead for the 90 deg. fold. I don't really have an acceptable explanation for this except what I surmised above.

Any input would be appreciated...

DM

[DrWho]

lol, now you bring it up!

If I may be so bold...I bet they (Roy and PWK) sat down and calculated what they wanted the horn to do and then modified the design several times until they ended up with something that measured well. Somewhere in the process they were talking to the manufacturing guys where they altered the design a bit to make it easier to build - and in that process some more tweaks were probably implemented. I could totally see them getting rid of the reflector in that process if they felt it didn't make a difference.

[Guest " "]

D-MAN

I noticed that they used it on the core that has the tri-angle shaped dog house but not with the core that uses the lascala shaped dog house.

Clearly, not putting one in it will certainly reduce the upper bandpass as you explain and in doing so, produces a sound, that I can only discribe as a upper mid-bass rumble if the cutoff point and slope used are not a match for the cabinet.

Fortunately, today, with the advent of steeper slope xovers, and the use of active xovers by some, changes to both the cutoff point and the rolloff rate can fine tune this to allow folded horns to reach higher with aout relying on enclosure capacitance.

[D-MAN]

Mike, I can't buy into that - they included a reflector, albeit half the size of a full channel variety. Not much savings there! Same labor is involved.

I think we can agree that it isn't a matter of economics or ease of building!

It's definitely a performance-driven decision, as you suggested, but I would just like to know the EXACT reason, instead of guessing

It could definitely be crossover-driven, too. A design hold-over for a particular crossover point and/or slope contour, maybe. That would also allow for preselected drivers (particularily the midrange) to be used, something PWK was known to design for. That is good thinking. Why didn't I think of that?!

DM

[jwc]

Dana. I appreciate your advice on the use of the Kappa drivers. I anticipate that they will sound the best. I am doing my best not to be overconfident with the results.

My statement, "I guess there could be a chance that the kappas may sound unbelievable in there", is being enthusiatic, not skeptical.

I did do some gross math on those drivers when you first mentioned them. Things such as mass roll off, back volume and throat. It has been awhile and I don't know what I did with the info as I would have purchased them anyway after your suggestion. I believe my math was a Vt around 31 sq inches. I forgot the rest.

Richard. Believe me...IMO you are at the point of diminishing returns. Your setup is awesome. I am not encouraging a sub at all. I have been bouncing around horn subs in my head and just curious.

Guys. You may ask....why didn't I just make the Jubilee clone Just like a Jubilee? Yes I could have. Remeber, I didn't start this thread with the intent of building a Jubilee. The advive was leading me to the Jubilee. I made a few changes that were minor and threw in the reflectors. I'm sure there was good reason besides cost and build to not place the full reflectors by klipsch.

This build is a reflection of the comments in this thread. If anyone had a problem or concern with the full reflector...I guess they should have said something. Dana and others know way more than I and I am going to take their recommendations seriously.

I couldn't have built this thing w/o help so I will do the honor of building it out of respect for those helping me.

I have no regrets for putting that change in there. Looking forward to the results and hearing comments on what difference the reflector made.

Here is a final view w/o the top and bottom. I almost hate to seal it off as I will never be able to see in there again.[]

jc

[jwc]

,,,,,

[WMcD]

I'm sure you're thinking this way too, but don't forget wheels. These little darlings are heavy. And there is the issue of a parking spot in a room. I learned this from building the K-Horns.

This is worth describing to bystanders, here.

Like you, I built them on a B&D WorkMate. Eventually you have to rotate them down on to the shop floor. I bought five heavy duty castors for each at HD. The person who invented the wheel had a good idea. Smile.

I see that you're thinking about a simple hatch on the top and bottom. This brings up the issue of what structure will be sitting on your carpet.

In my case, I kept the wheels on. But they do dimple carpet. I see that owners of real Jubilee have used some sort of gusset. A triangular piece of ply in the corner to take the load. I used hardboard.

Best,

Gil

[seti]

,,,,,

I would dam near sell my sould for building skills like yours. Great work..

[D-MAN]

Get out the paint... before you put the top/bottoms on... seems like it would be easier for doing the inside channels...

DM

[jwc]

I'm gonna hold off on the painting. I know it will be tougher with top and bottom but I think I can swing it.

Got the drivers out tonight. Both fit in the same T-nut holes. I am really liking this T-nut thing.

The Pioneer driver is a smaller driver and is easier to fit in the chamber. The 1 1/4" screw is the way to go with these vs the 1 1/2" for the kappas. Both screws again #10 x 32 with a lock washer and flat washer.

[jwc]

The The Eminence Kappa Pro one is up close

Pioneer 51F in the back

[jwc]

Pioneer in front here

[jwc]

Markings for the lid. The cutout is the easy part. The driver hole will be easy too. Gotta think about the driver hole covers a little more.

Do you think it would be ok to use 1/2" MDF for the covers with 4 T-nuts?

[DrWho]

4 would be a bare minimum. How do you plan to have this door seal? Just plain old gasketing material?

[Coytee]

I'm being more serious than silly here...

If the hatch works the way I *think* it works (max opening with routed 1/2" or so edge for the 'lip' to hold the hatch...)

I'd wonder if you'd have enough meat there for the T nuts? My suspicion is you wouldn't (but I may be wrong on several presumptions)

What if you simply used another ENTIRE sheet on top, this way you could use T nuts, attach it 24 places and it would add (yet another) ton of weight to this thing? The top would then be double thick (and bottom I suppose) but would also be a single solid piece instead of having to drill so close to the edge of the MDF.

I know there are numerous impractacalities about that idea but it might solve some other impractacalities, like drilling too close to the edge and the T-nuts not holding (presuming there's enough room for them to line up to the door hatch) or worse, as I know you know, using screws.

You're going to need a hoist to move this thing!!

[]

I've already thought of another deviation of my idea but won't beat a dying horse []

[jwc]

I won't use a router to have a flat surface like yours or like Gil's cabinet.

I'm at work and I will explain the best I can,

The door/hatch will be a cut out bigger than the driver chamber opening. There will be 4 T-nuts mounted on the underside of the top and bottom of the cabinet. The door will have 4 holes in it that will allow 4 screws to "fasten" the door down to the 4 T-nuts in the top or bottom.

Yes, I was planning on god ole cheap gasket or window sealer on the underside of the door.

jc

[Coytee]

I didn't realize you were not going to have a flat surface. Your idea is essentially what I was saying but you're going to cut off the excess material (pounds []) I was trying to give a flat surface.

I don't see why it woudln't work then as long as you've got good material to hold the T-nuts.

Might be interesting when it comes time to put something on top though?

Now get back to work!

[]

[DrWho]

Where are you going to isntall the T-Nuts? they only work when the screw compresses into the wood when the screw is tightened. I see a bunch of vertical stuff right now which means you'd need a screw that goes through the length of the cabinet. Am I missing something? Will you be putting on a top panel that covers the entire speaker, but has a cutout for the driver access that is slightly smaller than the actual? (providing room for the T-Nuts). It looks like a tight fit so maybe the T-Nuts need to move out a bit further and be pre-drilled (going over right after the 45 degree deflectors).

If you wanted to be crazy insane with the hatch you could build it such that you have a "funneled" lip that insets into the driver hatch with a top section that is larger and covers the hatch. The reason for the funneling is to prevent the sealing crap on the inside from getting pushed down while also providing a tighter seal. You will also want sealing crap underneathe all of the top part (regardless of the configuration) to prevent buzzing when the cabinet vibrates.

[D-MAN]

I think the way the stock one does it is the way I have mine, the flush-mount inset variety.

That means the access panel is the same thickness as the top/bottom and is screwed to a "lip" set inside the back chamber to line it up flush.

There are several ways of accomplishing the access panel - Gil did the "heavy" approach and doubled the top/bottom panels to create the lip.

Mine uses 3/4" strips along the inside walls of the back chamber.

Then there is the overset-type as seen on the stock Khorn and LS where the panel is oversized and is screwed directly into the top/bottom (in this case). Overset is the easiest to do, of course. In the case of the Jubilee, I don't see a problem as long as the panel is appropriately large so that it forms a solid surface to support the cabinet on the bottom.

Entirely up to you which one you go with.

[D-MAN]

The flush mount variety shown with access panel in place. The panel is 5/8 veneered both sides. It does not vibrate much at all. The terminal connectors on the access panel (as shown) are probably not such a good idea on the Jubilee, IMO.

Notice the number of screws used to tighten the access panel down! Do NOT skimp on the number of screws, or you'll be sorry. It is suprizing how much force the driver has, and how small of a gap that air can squeeze out of.

Did you know that the thing can actually have water-tight seals, but STILL leak air?

DM