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Old 26th April 2012, 02:55 AM   #1131
irext is offline irext  Australia
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I directly soldered all my connections as I don't particularly trust crimp connections unless they are also soldered. As far as active xover for the Elsinore's after looking at how much design and testing work Joe Ras put into the passive networks and the fact that they are mostly 1st order I can't see how an active one can reproduce let alone improve the results. They would cease to be Elsinore's!
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Old 26th April 2012, 03:03 AM   #1132
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Originally Posted by jdkJake View Post
Boy, that did not take long to reconfigure. Very handy and flexible board you have there to be able to make such dramatic changes so quickly.
I'm very interested to hear what you think of them once you fire yours up. You must be so close you can taste it!
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Old 26th April 2012, 03:19 AM   #1133
jdkJake is offline jdkJake  United States
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Originally Posted by zerotohero View Post
Jake, great harnesses and nice double heatshrinking.
The zip tying of the cable was a nice touch too.

Have you thought about soldering the cable directly to the speaker terminal?
I find it gives a better connection and better sound.
Thanks.

I did think about direct soldering the cable and still might. For the time being at least, I wanted to have the flexibility of easily changing out drivers until everything has been verified operational and settled in.
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Old 26th April 2012, 03:23 AM   #1134
jdkJake is offline jdkJake  United States
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Originally Posted by irext View Post
I'm very interested to hear what you think of them once you fire yours up. You must be so close you can taste it!
Yeah, getting pretty excited. I hope to build up the cross overs this weekend. Just need to clear my plate first at the day job. A most demanding presence right now.

But, it pays for the toys, so, it is hard to complain.
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Old 26th April 2012, 08:01 PM   #1135
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Beautiful job on the cabinets jdkJake! They look gorgeous and professional.

A few questions, will these be in a dedicated 2-channel music only system or HT? What equipment will be driving these? Approx square footage of the listening room?
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Old 27th April 2012, 12:39 AM   #1136
jdkJake is offline jdkJake  United States
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Originally Posted by Heathkit View Post
Beautiful job on the cabinets jdkJake! They look gorgeous and professional.

A few questions, will these be in a dedicated 2-channel music only system or HT? What equipment will be driving these? Approx square footage of the listening room?
Thanks for the kind words.

These will move into my main listening area. They will serve double duty in that space. Once the Hamlet crossovers are finalized, I will be building matched center and rear channels. Equipment will vary as I built these explicitly to experiment with various amplifier topologies. My room size is a bit hard to characterize. While the room is of medium size, it opens up into the rest of the house which makes it very difficult to adequately size the true total square footage. Hence my desire for a "big" design with broad dynamics potential.

We shall see how they do soon.
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Old 27th April 2012, 07:41 AM   #1137
irext is offline irext  Australia
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Originally Posted by tpate View Post
When I was researching my build I saw some posts that indicated that someone was trying an electronic crossover with the Elsinores. He was never satisfied with the results. The crossover is such an integral part of the speakers, such as 6db per octave rolloffs, phasing etc. that I would go with the passive. The Bolserst mod uses a notch filter on the "mids" that you wouldn't be able to do with active.

I too was having trouble with interactions between the inductors and put a 10" post on the crossover board and mounted the iron core inductor on top of it. Not pretty but effective. Got the inductors away from each other and didn't increase the footprint of the crossover board.

Has anyone else tried the Bolserst crossover mods besides Joel? Would be interested in your comments.
DId you notice a significant difference in performance once the inductors were separated?
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Old 27th April 2012, 04:53 PM   #1138
tpate is offline tpate  United States
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I separated the inductors after Bolserst did his measuremnts and indicated that there might be some interactions. At the same time I moved the iron core I did the mods that he suggested. Hence I can't say how much of the change was attributed to the movement of the intuctor. However, the overall sound became much more focused and tighter after the mods.
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Old 27th April 2012, 10:34 PM   #1139
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Originally Posted by irext View Post
I've now rejigged the inductors in my xovers to satisfy the data given by Troels Gravesen. (as best I can given the constraints of my pcb). Many thanks to JdkJake for the link. It'll do for now but I'll definitely have to redo the artwork to satisfy myself. At first listen my impression is better performance at high listening levels which I guess would make sense as the cross coupling would surely be worse at higher levels as the induced fields between the inductors would be greater.
Hello irext,

Determining placement and orientation for minimum coupling between coils by ear:
Rules of thumb to minimize coupling basically boil down to 1) distance is good, 2) if you can’t get distance, proper axis orientation can help.
Here is another useful link on the subject with measurement:
Inductor Coil Crosstalk Basics — Reviews and News from Audioholics

For those without oscilloscopes or LCR meters, determining levels of goodness for these rules of thumb and any other arrangement can be done in a rather simple manner. Tools needed are a pair of headphones, amplifier, 4 ohm 20W resistor, and a signal generator or test disk. Hook the leads of one inductor to your headphones. Hook the leads of the second inductor to the amplifier with the 4 ohm resistor in series with one of the connecting wires. Play a 1kHz – 2kHz signal thru the amplifier. Usually < 10Watt is adequate to hear a strong tone in the headphones when the two coils are placed in close proximity to each other.

Listening to the amplitude of the tone, you can get a feel for how distance and orientation affects the coupling. You will find that at close distances minimizing the coupling thru axis orientation can be quite critical of angle adjustment.


Considerations for iron core inductors:
I noticed you had two 9mH iron core inductors hooked in series to get the required 18mH. However, when the iron cores of two inductors are positioned in-line and close together there is considerable mutual inductance generated thru coupling.

Attachment #1: Actual inductance measurements for two series connected 6mH inductors
(A) Where coupling is minimized by axis orientation, total inductance = 12mH
(B) Where mutual inductance is additive, total inductance = ~23mH
(C) Where mutual inductance is subtractive, total inductance = ~10mH

Case (B) can be used to your advantage when creating larger value inductors from two small ones. The gap between the cores can be adjusted to give a value anywhere between 2 to 4 times the individual inductances. For example, Attachment #2 shows an 18mH test inductor I build from the two 6mH inductors carefully spaced apart be MDF blocks.

So, depending on the orientation of your 9mH inductors I would estimate the total inductance is probably either ~23mH or ~16mH; not the 18mH you were going for. The good news is that this inductor is only used for impedance compensation "up-stream" of the woofer crossover and has fairly non-critical tuning. But, something to keep in mind if you ever use inductors like this for critical areas of a crossover.

Another thing to point out about case (C) is that the magnetic fields from the two inductors are bucking against each other. This results in a strong flux field shooting radially outward from the gap between the cores. So, positioning other inductors near this area is not a good idea. You can confirm this by listening to the tone from a coil placed in this area. Case (C) will produce considerable louder tones in the headphones than case (B). Attachment #3 is an attempt to graphically depict the behavior of the flux fields for cases (B) & (C).


Old tricks rediscovered:
While playing around with coil placement, you may accidentally stumble on the fact that there is another orientation besides orthogonal axes that will minimize coupling between coils. If you start with two coils spaced slightly apart and oriented in the same direction and then rotate both of them at the same time in the same direction, you will find somewhere in the 50deg – 60deg range the coupling completely disappears. The exact “magic” angle depends on the coil diameter and length, and is pretty easy to find by ear with the technique described above. This behavior was patented by Hazeltine (US 1577421) in the early 1920s for use in cascaded RF amplifiers in early unshielded radios. See Attachment 4 & 5. The cool thing is that you can line up any number of similar sized/shaped coils at the same spacing and angle and there will be minimal coupling between any/all of them.
Attached Images
File Type: gif coils_iron_03.gif (42.8 KB, 422 views)
File Type: jpg 18mH.jpg (24.5 KB, 411 views)
File Type: gif coils_iron_04.gif (30.1 KB, 416 views)
File Type: gif magic_angle.gif (151.3 KB, 412 views)
File Type: jpg neutrodyne.jpg (36.2 KB, 390 views)
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Old 28th April 2012, 05:49 AM   #1140
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Originally Posted by irext View Post
As far as active xover for the Elsinore's after looking at how much design and testing work Joe Ras put into the passive networks and the fact that they are mostly 1st order I can't see how an active one can reproduce let alone improve the results. They would cease to be Elsinore's!
Thanks for that.
It looks like I will stay with the original passive crossover plan then.

Its a shame as I have two Rotel rb1080 power amps (was thinking of getting a third) but I can still bi-amp.

Maybe I'll even experiment with passive crossover for the mids and highs, and active for the mids and bass?

What are your thoughts?
My current crossover is a nakamichi ec100 two way with seperate power supply.
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