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Old 17th September 2013, 12:03 AM   #1611
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Elsinore Cabinets for Sale

Elsinore Speaker Project Cabinets for Sale
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Old 17th September 2013, 01:00 AM   #1612
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Woofers for the Excellent JR Mini Speakers

NOS Peerless 832873 5-1/4 Nomex Woofers for sale
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Old 20th September 2013, 12:43 PM   #1613
ABO is offline ABO  Netherlands
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Default Someone willing to build cabinets?

Given that I am in Europe and that shipping costs for Elsinore cabinets across the Atlantic would be inhibitive I have to pass on Joels offer. It is however an offer I would gladly accept otherwise since I have no woodworking skills whatsoever.
So, if someone in Holland area (western Germany and perhaps Belgium would probably be close enough as well) is willing and able to build nice quality cabinets for me, please send me a PM. I will be looking for a paint finish that I will apply myself.
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Old 26th September 2013, 02:03 AM   #1614
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I have 11 waveguides that need to be Powdered.. $160 per pair..
They are the type that mount over the mounted tweeter..

This is the last batch of them and hopefully a member start making them for future..

If interested, Please let me know..

Joel
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Old 5th October 2013, 11:38 PM   #1615
dimkatr is offline dimkatr  Sweden
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Default Joe Rasmussen Approach to Crossover

Hello to everybody!

Although a member for some time, this is my first post. I take the opportunity to say "thank you!" to all of you participating here for a better audio experience and understanding!

Having read many times Joe Rasmussen's article "Joe Rasmussen Approach to Crossover", I believe that a different set of sketches, concerning drivers' movement when they are connected to Butterworth crossovers, may show in a more accurate way what the author is proposing.

1. Rest point, no comments!

2. In Joe's sketch, both drivers are moving forward. Since there is the BW characteristic 90 degrees phase lag, I propose the alternative sketch. Is there any reason the lag appears in the second quarter of the signal's cycle?

3. In the third sketch the mid driver is still moving forward, its excursion is doubled, although, I think, it should return to its rest point. Therefore, another sketch proposal.

4. The 3rd cycle.

5. The 4th cycle.

6. The fifth stage of movement, concerning only the mid driver as it returns to its rest point alone, since the tweeter has already reached its own in the previous stage.


Do I miss something important?

I would appreciate a lot your comments, especially Joe's.
I just hope that I do not duplicate someone else's same or similar thoughts already posted here. I could not locate something similar in this long thread.

Best regards

Dimitris
Attached Images
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File Type: gif Rev 2nd_90.gif (2.4 KB, 300 views)
File Type: gif Rev 3rd_90.gif (2.8 KB, 299 views)
File Type: gif Rev 4th_90.gif (2.6 KB, 297 views)
File Type: gif Rev 5th_phase_remainder.gif (2.5 KB, 11 views)
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Old 10th October 2013, 08:27 AM   #1616
Fasen is offline Fasen  Denmark
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Which of the XT25's are used in the mini monitor?
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Old 10th October 2013, 10:10 AM   #1617
dondiba is offline dondiba  France
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Default wave guides

hi
i'm interessted by a pair but i'm afraid of the shipping cost to france
is someone willing to sell a pair of wave guides from europe?
thank you
dondiba
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Old 10th October 2013, 12:51 PM   #1618
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hello,

I edited and posted the woofer and tweeter model number for mini in the swap meet thread.
Joe Rasmussen Mini Monitors $350 complete

Shipping waveguides to France is $25 ground

I have only 3 waveguides remaining so extra one for Center: $200 pus shipping..

I have a kit of parts in swap meet in the cabinet sale.. The kit inlcludes waveguides but if someone should be interested in the kit without the waveguides then that will make one more pair available..

Thanks, Joel
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Old 10th October 2013, 02:34 PM   #1619
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Quote:
Originally Posted by dimkatr View Post

Do I miss something important?
I am not sure what the question is?

The sketches you posted do not match what is on my website.

The fact that one driver starts from a resting position equal to the baffle and the other does not, it has to be understood what is represented is a slice in time, not just a signal burst of one cycle.

Let's say that it is a 3KHz sine wave and the crossover is also at that frequency. Let us also say that both MidBass driver and Tweeter have the same Sd, the total surface area (in reality they don't, but that need not concern us for this excercise) and that one driver has a high-pass filter and the other a low-pass filter, single-pole. Then the representation is correct.

Click the image to open in full size.

This is NOT the starting point of excitation - this is a constant sine wave already in motion. This is a "book-ended" cycle.

Click the image to open in full size.

Both drivers move forward, being excited by the same signal, but with different but complementary filters. The top driver is now at it's maximum forward posistion. Because the other bottom driver is 90 degrees out of sync, it will be in the middle position and continuing to move forward as the next quarter cycle demonstrates.

Click the image to open in full size.

The upper driver moves backward and the bottom driver continues to go forward. While in the first quarter of the cycle, where both drivers were moving forwarding, they were summing positive (additive). But in this cycle, they are not adding, but are cancelling. Zero output results.

The next cycle the will again sum.

Click the image to open in full size.

While they are now moving backwards together, the are still summing - not cancelling.

Now we have the final quarter.

Click the image to open in full size.

Once again cancelling and back to the original position. We have gone through the entire 360 degrees of the cycle.

So Butterworth cancels out half the output, every second quarter of the cycle results in no output.

But that is of course only the beginning, because in real life the MidBass is starting to beam considerable at 3KHz and it is part of the Tweeter's job description to fill in the failing off axis response in the MidBass, and it cannot do that with any degree of success. So with Butterworth, we can only aim at a flat response on axis, whereas off axis there will be a considerable lack of energy. This means that Butterworth cannot have a flat power response into the room. And yes, it is very much audible, it also cause a perceivable discintinuity between the two drivers. To use fellow loudspeaker designer (and long-time friend) Brad Serhan's wonderful description, "it is about getting the stitch right" and if you get that right, you end up with a crossover that virtually does a disappearing act.

There are other considerations as well. Note that, in the above example, when the first quarter of the cycle, the perpendicular axis is aiming down, and in the third quarter it is upwards? Now consider that indeed the Tweeter and Midbass do not have the same radiating area, can you see that Butterworth also has vertical symmetry problems.

All I am demonstrating is why I avoid doing Butterworth designs.

Cheers, Joe

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Last edited by Joe Rasmussen; 10th October 2013 at 02:37 PM. Reason: spelling.
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Old 10th October 2013, 03:38 PM   #1620
dimkatr is offline dimkatr  Sweden
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Quote:
Originally Posted by Joe Rasmussen View Post
The fact that one driver starts from a resting position equal to the baffle and the other does not, it has to be understood what is represented is a slice in time, not just a signal burst of one cycle.

This is NOT the starting point of excitation - this is a constant sine wave already in motion. This is a "book-ended" cycle.
.

I regret the above were not clear to me...

Now I fully understand and agree with your thinking.

Thanks for the clarification!

Best regards
Dimitris
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