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Old 16th January 2008, 01:47 AM   #141
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Quote:
Originally posted by John L


There are probably some ways to get around this. First, the diffuser will have to be large, and curved enough to allow the high frequencies to be dispersed around the room at a lower level, more where the person is sitting.

And second a more efficient compression horn will tend to work better than just a high efficiency tweeter. If you look at all three models Duevel use, they are all high compression horns. HC horns are almost always far more efficient than other tweeters, and should be far better at taking up the slack.

That's just my guess, of course.


Incidentially, that must be the reason why you have that PE tweet facing front and center in your new project.
As I understand it, the human ear is most sensitive as a locator in the 2-6khz range and I think this may be why many true omni's are said to be poor imagers. They disperse all the frequencies in this range, resulting in a lot of reflections and arrival times that are too quick to the listener, unless they are placed the perfect location, usually far from any walls. I believe the hybrid approach offers an excellent in room power response, yet avoides more of the reflection problems that can smear the imaging in that critical region. You will notice that the Beolab 5 is only omni in the front 180, rather than 360. YMMV! :-)

I believe the reason that Duevel uses large compression drivers is that they are high sensitivity and can cross much lower without stress than most dome tweeters. They are also designed to use in horns, whereas domes are not. A compression would probably be good to try. On the negative side, I think most are pretty high in distortion. There are trade-offs for every decision is a speaker design, however.
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Old 16th January 2008, 02:38 AM   #142
John L is offline John L  United States
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One of the things I discovered, while reading the reviews of the Jupiter, is that the reviewers stated that the Jupiter worked best if it was approximately 36" out from the wall or the corner. That made a huge difference. Also, the direction it was turned mattered as well, because the manner in which the sound, coming from the porting made a subtle but vital difference.

This picture give you some idea as to how the Jupiter treats the movement of sound Behind the driver. I had never really paid any attention until I started paying closer attention to some of the pictures.

Click the image to open in full size.

Before this, I had always looked at the bottom of the Jupiter and Bella Luna as just a black area, with no earthly idea as to how it worked down there. But after this picture, I began to notice subtle differences in the cabinet bottoms on some photographs.

With pictures like this, of the bella luna, it is easy to overlook what is happening.

Click the image to open in full size.

It just looks like a flat surface there. But ocassionally there are shots that are more reveiling.

Click the image to open in full size.

There are others, but I have gone through so many pictures of these cabinets, literally hundreds, and cannot keep up with where I saw them all. The point that was brought up earlier about this project being more than just a 'box' issue, is correct.
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Old 16th January 2008, 03:06 AM   #143
John L is offline John L  United States
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Quote:
Originally posted by dlneubec

I believe the reason that Duevel uses large compression drivers is that they are high sensitivity and can cross much lower without stress than most dome tweeters. They are also designed to use in horns, whereas domes are not. A compression would probably be good to try. On the negative side, I think most are pretty high in distortion. There are trade-offs for every decision is a speaker design, however.
I have done some rooting around in that regard, and there are some HC horns that appear to be quite good. But you have to look closely, And be prepared to fork over some nice investment with some. It is easy for some of these to go over $200 each, so picking and choosing is essential.

Here are a couple of pretty good choices. One is the B&C DE250-8 1" Polyimide Horn Driver. Here you can get some idea of it's specs.

Also, there is the B&C DE500-8 1" Neo Titanium Horn Driver. The data sheet is right here.

this Selenium D3305Ti-DPD 2" Titanium Horn Driver, also appears to be a nice one. Here is it's data sheet.

There are plenty of HC horns out there, but so many of them have good curves, IF you are willing to crossover much higher, or if you are willing to compromise. But there are also some very good ones too.

An example of what i am talking about is the Selenium D210Ti 1" Titanium Horn Driver 1-3/8". It's currently on sale at PE, and the price is right, but if you look at it's data sheet, you can see that it is much less than perfect.

But on this first project, I am going to go with the tweeter I mentioned at the first of the thread. If it does not pan out, I will have to go to other extremes.
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Old 16th January 2008, 12:49 PM   #144
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Hi John,

One of my problems with most of the pro type drivers is the lack of independent testing by folks like Zaph, where you can get a direct comparison to more typical home Hi-Fi drivers It would be nice to have that information before you plunked down that kind of cash based on jut the manufacturers published specs.

I've read most of the internet reviews of the Duevel products as well. However, I never read an explanation of what is happening in the black angled areas. What is your take? Are they simply ports? I'm not sure how that clear version illustration applies to reality. BTW, I believe the low end drivers used in the Duevel Bella Luna and Jupiter are PHL drivers, which are pretty pricey.
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Old 16th January 2008, 01:17 PM   #145
John L is offline John L  United States
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I suspect we will need to get Dave back into this discussion. His contribution right here is worth checking out. I think his reference to a "pipe" effect may be a valid one.

Just looking at the Jupiter and it's venting, as it is, tells me that there is more than just porting involved here.

Unfortunately, I cannot copy this, because I have braces dadoed and glued in place which would make this impossible. It's within reason to hope that proper venting and stuffing of the tube will work too.

Also, maybe Scottmoose can give his input as well.
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Old 21st January 2008, 03:31 PM   #146
John L is offline John L  United States
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While I was glueing up other parts of the cabinet, I happened to think of the big difference between the Titebond II and the Better Bond Heat Lock glue. I learned the hard way, on this project, about what to look for with regards to what the glue looks like when it dries.

Click the image to open in full size.

As you can see, the Better Bond dries to a very dark colour, and unless you are using a dark veneer, or dark stain, it is not the best product for your veneering needs. The Titebond, on the other hand, dries to a much ligher shade, and will not be noticed, in the joints, as will the Better Bond.

For this reason, I recommend the Titebond II glue for ironing on veneer, except in the rarest of instances. And as a further plus, a gallon of Titebond II costs $18.99 at Lowes, while the Better Bond costs $34.95. Clearly a major consideration of about $15.
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Old 21st January 2008, 04:04 PM   #147
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I have now gotten to the point in the project where I need to be thinking about the diffusion lense and the driver setup. Here is where I stand today.

Click the image to open in full size.

All the preliminary work is complete with the cabinets and the bases. When everything else is finished, I will come back and clean up any over-application of shellac in places, and reapply several more coats. Then I will repaint the bases two or three more coats.

I will also add that I have another class scheduled with the lathe instructor for all day Wednesday. Hopefully I will have the proceedure down pat enough to complete a pair of lenses. If not, I will go back for a third session.

Almost everything is tentively complete on the top cap of the cabinets. Here is what the caps looked like before routing out the hole for the driver.

Click the image to open in full size.

I had tried to get the fit as snug as possible, but later learned that this is unnecessary, and even not recommended. A seal running around the inside and under the cap will work just as well.

And here is what a cap looks like with the hole routed out and a reinforcement underneath the cap. In this picture you can clearly see my foul-up with the dado cuts, which I talked about earlier. I had filled in the cut with other plywood and applied enough glue to make it completely saturated in the stuff. It shouldn't be going anywhere, but it certainly looks terrible and I Know about my foul-up. I cannot guarantee that I will never do that again either.

Here is the cap turned upside down, with the inner cabinet exposed. I used the OSB because I had plenty of it setting around as scrap, and I needed something to help brace the bolts that would be holding down the driver. it should also add stiffness to the cap.

Click the image to open in full size.

All the cleats were cut at approximately the correct angle, and were glued and screwed to the lip of the rabbet cut-out of the cabinet. Once my speaker mounting kits arrive, I will drill a hole centered near the edge of each wall, that goes into each cleat, and use it for bolting down the cap to the top of the cabinet. Also, for versatility, it can be unbolted and removed for changing out the driver in the future, if desired.

Click the image to open in full size.

Here is the other cabinet that does not have the foul-up.

Click the image to open in full size.

In the cap finishing department I had tried to come up with the most practical and best looking way to finish the cap. Origionally, I thought that some form of black plastic "L" shaped edging would be nice for finishing off the top of the cabinet. By using an Exacto knife and cutting angles, plus scoring the inside of the plastic, I would bend the edging evenly around the cabinet top. Unfortunately that did not work, because the plastic kept breaking on me at the scored areas, so I finally had to give that up. My thoughts of having a nice even trim around the top of the cabinet were dashed there.

However, I finally came up on the idea of just acquiring some black Plastic Laminate, and using contact cement to glue it to the top, and having an overlap, which could then be trimmed off once the lid was placed on top. The P/L would fit perfectly along the top, and I could adjust it to match the edges by shifting the lid around a little bit before tightening the speaker mounting bolts securely.

This is where I am at the present. The weather is just too cold to be out there in the snow, on the back deck, painting on contact cement. I'll have to wait until it gets above the freezing point, and all this global warming melts away.
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Old 21st January 2008, 04:04 PM   #148
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Hi John,

Have you or anyone else tried Titebond III for the iron on method? I'm curious to kow what difference it would make versus II.
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Old 21st January 2008, 04:16 PM   #149
John L is offline John L  United States
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Quote:
Originally posted by dlneubec
Hi John,

Have you or anyone else tried Titebond III for the iron on method? I'm curious to kow what difference it would make versus II.
No, but I have closely eye-balled it over at Lowes. And it is almost the same dark colour as the Better Bond glue. If I let it dry, it too would dry quite dark. I'll take a pass on as well.

I know what Titebond II looks like dry, and I also know that it works almost as well as the Better Bond, because there are more than enough testimonials about it on the internet. And it costs about 40% less than the Better Bond brand. And while Titebond II is not 100% waterproof, it is good enough for just about any application.
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Old 21st January 2008, 04:47 PM   #150
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Hi John,

I've used TB III many times and it dries about the same color as it starts. It is not nearly as dark as that one you posted in the Arby's bottle. I think it might possibly be a better color for all but the lightest woods, like Birch, Maple, Aspen, etc., assuming it works as well with the iron on glue method. I used it to egde glue up a Maple baffle (with biscuits) and it is barely detectable. I can take a photo if anyone is interested.
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