Thanks for suggestions;-
This is the overall cheapest/reasonable I can find;-
https://secure.wilmslow-audio.co.uk...d/684?osCsid=b0ae4c86fef83fae3cebd5c12602e55d
To go better means a large jump in price, though of course two would work well in a narrow cabinet.
My real quandry is that there are some really excellent car LS about, and it is possible to buy 6x9/7x10 coaxials having equal bass performance but complete with phase matched mid/tweeter assemblies, for the same price as (and sometimes less than!) these above drivers.
Eg: Kenwood KFC-E6950 (M6950A,6980ie) are X-max +/-4mm with 6mm pole plate, 31mm coil, Sd 225cm^2, VAS ~23.8l, Qts 0.84 and thus versatile.
Cheers .......... Graham.
This is the overall cheapest/reasonable I can find;-
https://secure.wilmslow-audio.co.uk...d/684?osCsid=b0ae4c86fef83fae3cebd5c12602e55d
To go better means a large jump in price, though of course two would work well in a narrow cabinet.
My real quandry is that there are some really excellent car LS about, and it is possible to buy 6x9/7x10 coaxials having equal bass performance but complete with phase matched mid/tweeter assemblies, for the same price as (and sometimes less than!) these above drivers.
Eg: Kenwood KFC-E6950 (M6950A,6980ie) are X-max +/-4mm with 6mm pole plate, 31mm coil, Sd 225cm^2, VAS ~23.8l, Qts 0.84 and thus versatile.
Cheers .......... Graham.
Svante said:
Hi Svante,
Thanks for posting that - I feel so redeemed!
The similarity between the 2ohm and 4 ohm curves seems consistent with my earlier assertion that if the magnetic coupling between parallel windings is good, it should be equivalent to merely using a fatter, single wire.However, there is one possible difference that I hadn't thought of before: some amplifiers tend to perform a lot differently when presented with a reactive load, compared to a purely resistive load.
At 2ohms: Re = x1 , Le ~= x1
At 4ohms: Re = x2 , Le ~= x1
At 8ohms: Re = x4 , Le ~= x2
(edited...)
The power factor is not the same between all three options, which would suggest that if there are audible differences, they would probably be caused by technical limitations of the amplifier/s rather than some mysterious 'quality' caused by the dual voice-coilness of the speaker.
Cheers,
CeramicMan said:
Hmm... I'd say
At 2ohms: Re = x1 , Le ~= x1
At 4ohms: Re = x2 , Le ~= x1
At 8ohms: Re = x4 , Le ~= x4
CeramicMan said:
If you by power factor mean the ratio between resistive and reactive parts, yes there is a difference. There is nothing magical about the difference though even though it leads to audible differences.
Here is a simulation of the driver in an infinite baffle. The high frequency response is attenuated compared to the measured response curves; this is typical when the driver has pronounced cone break-up (this is not modelled in the simulation).
One can see that the voltage sensitivity (the output level when driven with 2.83 V) is higher for the lower impedances.
One can also see that the power sensitivity (the output level when the driving voltage is scaled according to nominal impedance) is the same for the 2 and 8 ohm versions, but lower in the mid band for the 4 ohm, single coil connection.
An externally hosted image should be here but it was not working when we last tested it.
The point I was making was that LF reproduction quality/damping was clearly better when the cone control was shared between two amplifiers connected to one voice coil each.
This was with approx 65Hz crossover to the sub channel.
Whether any difference would show on an amplitude plot I could not guess.
In other words will the single winding green characteristics retain their same improved response below 100Hz, though with greater SPL when each voice coil is individually driven ?
Cheers .......... Graham.
This was with approx 65Hz crossover to the sub channel.
Whether any difference would show on an amplitude plot I could not guess.
In other words will the single winding green characteristics retain their same improved response below 100Hz, though with greater SPL when each voice coil is individually driven ?
Cheers .......... Graham.
Graham Maynard said:
Svante said:
We have a fourth configuration if we short the second voice coil, that was not tested.
And as the papers from Adire Audio describe it it can also be used to control parameters for the box enclosure.
"Use a dual voice coil driver, and you can use a much wider range of enclosures, and even have a system that can have a "Qts" knob on it, for changing the Qtc of a sealed system on the fly, according to your tastes."
http://www.adireaudio.com/Files/DualVoiceCoilDrivers.pdf
Good LINK you attached Inductor.
Of course dissipation is not as simplistic as stated due to loading angle of the LS system varying with frequency, but the independently controlable damping is a clever idea.
However, connect that second winding to an identical low impedance amplifier carrying the same output and you get the same reduced system 'Q' figures. This being better than driving using a single amplifier with driver voice coils wired in parallel.
Any way you can simulate this Svante ?
Cheers ......... Graham.
Of course dissipation is not as simplistic as stated due to loading angle of the LS system varying with frequency, but the independently controlable damping is a clever idea.
However, connect that second winding to an identical low impedance amplifier carrying the same output and you get the same reduced system 'Q' figures. This being better than driving using a single amplifier with driver voice coils wired in parallel.
Any way you can simulate this Svante ?
Cheers ......... Graham.
Inductor said:
Yes, this configuration is an even greater waste of energy, since heat will be generated in the second coil and it will act as a "break" being constantly on.
It is true that this will result in a "knob for Qts" but there are far more efficient ways of doing the same thing electronically in the amplifier. Adding an adjustable resistance over the secondary coil is nice for laboratory purposes, but equipping the amplifier with an adjustable output resistance is better. If this is achieved through a current sensing resistor and positive or negative feedback, it gives a far wider range of Qts adjustment, and near zero power/efficiency loss.
Graham Maynard said:
Hmm, I probably could, but it would require some serious re-writing of Basta!. I have thought about it previously, but the limited use for it has stopped me from doing so. It IS possible to simulate the effects by changing Qts and some other parameters to new values (just as I did with the three cases above).
Just came across this - has a DVC entry.
Not entirely correct !!!
Also assumption made of perfect amplifiers, which is not necessarily the case when some can have considerable phase shifted damping control wrt input, or LF weakness through the power rails.
http://www.geocities.com/f4ier/speaker.htm
Not entirely correct !!!
Also assumption made of perfect amplifiers, which is not necessarily the case when some can have considerable phase shifted damping control wrt input, or LF weakness through the power rails.
http://www.geocities.com/f4ier/speaker.htm
Graham Maynard said:
Yes, in particular the Le values are wrong, see above.
I think, however that it is reasonable to assume an ideal amplifier when dealing with these things, partly because feedback in the typical amplifier makes it near ideal at low frequencies, partly because the effects of different ways of connecting DVCs is easier to understand that way.
The output impedance* of the amplifier is a separate issue.
*The output impedance is often referred to as a damping factor. I don't like this, it is too easy to misinterpret it. For example, 1 damping factor of 200 is not twice as good as a damping factor of 100. It only means that the output impedance is 8/200=0.04 ohms instead of 8/100=0.08 ohms. When it is realised that this resistance is connected in series with the loudspeaker cables, and more important, Re, it is clear that the small change from 0.04 to 0.08 ohms is practically neglectible. Yet the damping factor was "twice as good".
...now I am drifting OT...
series or parallel how to?
I'm trying to figure out how to wire my dual voice coil woofer (M&K--early 90's) and the new M&K VX-1250 plate amp I just bought.
It may be helpful to know that the original M&K sub amp was 125w, whereas the new VX-1250 is rated for 250w (180 watts @ 8 ohms, 272 watts @ 4 ohms).
The amp has a single set of speaker leads out (red & black), but my woofer has two sets of leads in = dual voice coil, right?
So, am I supposed to wire it in series or parallel? How can I tell which one?
What would happen if I just hooked up one of the vc's and left the other un-powered?
I know just enough electronics lingo to get me into trouble, so, please advise exactly what series v. parallel wiring looks like!
Sorry to not know something that basic, but that's why I am here at DIY Audio.
Thanks for any help,
Phil
I'm trying to figure out how to wire my dual voice coil woofer (M&K--early 90's) and the new M&K VX-1250 plate amp I just bought.
It may be helpful to know that the original M&K sub amp was 125w, whereas the new VX-1250 is rated for 250w (180 watts @ 8 ohms, 272 watts @ 4 ohms).
The amp has a single set of speaker leads out (red & black), but my woofer has two sets of leads in = dual voice coil, right?
So, am I supposed to wire it in series or parallel? How can I tell which one?
What would happen if I just hooked up one of the vc's and left the other un-powered?
I know just enough electronics lingo to get me into trouble, so, please advise exactly what series v. parallel wiring looks like!
Sorry to not know something that basic, but that's why I am here at DIY Audio.
Thanks for any help,
Phil
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