Higher Effiency vs Lower Ohm Load

[metalheadjoe 10+ year member]

And the frequency where impedance will peak can be changed by the enclosure. How much the impedance will peak can be changed by the enclosure. By changing orders, we can introduce multiple peaks in response. The impedance will always be higher in an enclosure than free-air/IB, unless there some enclosure affect I'm unaware of.

Are you denying that enclosures change impedance curves?

Impedance is not impacted by enclosures. I thought I was very clear about that. Prove me wrong rather than assuming common misconceptions are facts.

 

[spokey9 5,000+ posts]

I don't understand why everyone is so defensive. I am here to learn and don't mind being corrected

Your article confirms that impedance varies with frequency.

The enclosure affects resonate frequency and that in turns effects impedence across frequencies.

it's part of the reason when you take a true 4 ohm sub (for example) place it in a box and play music the impedence would rarely show 4 ohm. Even with a tone the same sub in the same box would show the 4ohm until the coils started to heat up then you'd see rise there as well.

It's a big reason why you can sometimes cheat an amp by wiring lower than it's rated because the box is part of the driver and affects the impedence the amp will see

 

[metalheadjoe 10+ year member]

The enclosure affects resonate frequency and that in turns effects impedence across frequencies.

it's part of the reason when you take a true 4 ohm sub (for example) place it in a box and play music the impedence would rarely show 4 ohm. Even with a tone the same sub in the same box would show the 4ohm until the coils started to heat up then you'd see rise there as well.

It's a big reason why you can sometimes cheat an amp by wiring lower than it's rated because the box is part of the driver and affects the impedence the amp will see

Resonant frequency can refer to vibrations or electronics. I agree enclosure can impact resonant frequency in terms of vibrations. Vibrations don't have anything to do with impedance. If you are saying a box changes electrical characteristics of a circuit, tell me how. The commonly-quoted misconception is that box impacts impedance, which is the electronics use of the term.

How about this: Tell me how a box impacts impedance without mentioning frequency. It is ACTUALLY proven that impedance is a function of frequency, so let's exclude that and stay focused the "box rise" misconception. Show me a circuit where a sub played at a frequency in box-A has a different impedance than the same sub played at the same frequency in box-B.

 

[spokey9 5,000+ posts]

Considering impedance changes as the coil moves...anything that effects coil movement (like a box) effects impedance...

 

[Jimi77 5,000+ posts]

Here’s impedance plots using speakerboxlite and an Alpine Type R sub. The impedance is altered when the sub is placed in different enclosures.

Red = ported, Green = sealed, Orange = IB/free air, Blue is band pass.

 

[metalheadjoe 10+ year member]

Here’s impedance plots using speakerboxlite and an Alpine Type R sub. The impedance is altered when the sub is placed in different enclosures.

Red = ported, Green = sealed, Orange = IB/free air, Blue is band pass.

View attachment 59107

Why is only one axis labeled? I'm not going to take your word without seeing the original source, because you have switched from discussing to arguing.

Considering impedance changes as the coil moves...anything that effects coil movement (like a box) effects impedance...

Why does impedance change as the coil moves?

I'm willing to be wrong if anyone can conclusively prove it. It's obvious to me that none of you have ever even questioned the concept before, so now you're desperately trying to justify your belief.

 

[Jimi77 5,000+ posts]

Why is only one axis labeled? I'm not going to take your word without seeing the original source, because you have switched from discussing to arguing.

Why does impedance change as the coil moves?

I'm willing to be wrong if anyone can conclusively prove it. It's obvious to me that none of you have ever even questioned the concept before, so now you're desperately trying to justify your belief.

Nobody is desperately trying to justify anything. Box rise is "common knowledge." I can't even count how many times I've plotted different response and impedance curves for different enclosures - probably into the thousands.

The bottom axis is your standard logarithmic frequency response on the x-axis, TBH, I half think you're trolling; I have a hard time believing somebody who has been the hobby 10 years doesn't recognize what the x-axis is despite the missing label. I also have a hard time believing somebody who has been in the hobby for 10 years has never used software to analyze how different enclosures affect response and hasn't seen these graphs before.

Impedance changes because the coil is in magnetic gap and attached to a suspension, so the coil is no longer a simple inductor that responds only to changes in frequency.

Graph generated in speakerboxlite. At 41hz all 4 enclosures have a different impedance.

 

[metalheadjoe 10+ year member]

Nobody is desperately trying to justify anything. Box rise is "common knowledge." I can't even count how many times I've plotted different response and impedance curves for different enclosures - probably into the thousands.

The bottom axis is your standard logarithmic frequency response on the x-axis, TBH, I half think you're trolling; I have a hard time believing somebody who has been the hobby 10 years doesn't recognize what the x-axis is despite the missing label. I also have a hard time believing somebody who has been in the hobby for 10 years has never used software to analyze how different enclosures affect response and hasn't seen these graphs before.

Impedance changes because the coil is in magnetic gap and attached to a suspension, so the coil is no longer a simple inductor that responds only to changes in frequency.

Graph generated in speakerboxlite. At 41hz all 4 enclosures have a different impedance.

View attachment 59111

Now I think your graph is silly. You're saying that boxes increase impedance, and impedance is steady from 200hz and up? Please show me the math.

 

[spokey9 5,000+ posts]

It's a super simple thing to test for yourself...hook your dmm to a sub and push on the cone

 

[metalheadjoe 10+ year member]

It's a super simple thing to test for yourself...hook your dmm to a sub and push on the cone

You running out of logic?

 

[Jimi77 5,000+ posts]

Now I think your graph is silly. You're saying that boxes increase impedance, and impedance is steady from 200hz and up? Please show me the math.

No, I'm not saying that impedance is steady from 200hz and up. The software doesn't bother to plot it since we would normally crossover electronically and don't care about response above ~100hz. Inductance would be merely be a 1st order LPF with impedance approaching infinity with ever increasing frequency. As I said before, you're probably just trolling since it appears you're familiar with what an impedance curve should look like and when the VC's inductance should start acting as an LPF.

You can download Winisd or whatever software is available to observe how manipulating enclosures changes the impedance curve. Of course if were actually concerned about this issue, you would just do your own modeling, google search, etc. I think you're probably just arguing for arguing's sake.

Is LEAP good enough for you?

 

[Jimi77 5,000+ posts]

It's a super simple thing to test for yourself...hook your dmm to a sub and push on the cone

If he has non-inductive resistor (out of an old crossover network), he could build a simple voltage dividing network and run test tones/sine sweeps and watch the impedance change in real time. Could even do it with the sub in the enclosure (preferably ported) vs free-air. It's a little bit of effort, but dude seems damned and determined to not believe what anybody else has to say on the matter.

 

[Jimi77 5,000+ posts]

Hopefully these are useful links to anybody concerned about the effects of enclosures on impedance.

DIYaudio discussion about effects of enclosure on impedance with graphs.

Enclosure changes driver impedance

I am building a battery powered audio system which uses a TPA3116 based Class D amplifier running at 24v and powering a pair of 4 ohm Dayton Audio ND91-4 full range drivers. Audio input to the amp comes from a DSP and averages 1 VRMS. I have built several sealed enclosures for the system. The...

www.diyaudio.com

Winspeakerz demonstrating how impedance, FR and phase change with enclosure.

About WinSpeakerz: Loudspeaker Design software for Windows

Loudspeaker design software for Windows. Purchase WinSpeakerz and Introduction to Loudspeaker Design.

trueaudio.com

Winspeakerz offers a impedance calculator with their software suite, which of course wouldn't be necessary if impedance wasn't altered by the enclosure.

True Audio: About Loudspeaker Design Software

Loudspeaker design software for Windows and Macintosh. Purchase WinSpeakerz, MacSpeakerz and Introduction to Loudspeaker Design.

trueaudio.com

 

[spokey9 5,000+ posts]

You running out of logic?

Tru it and see what happens...

 

[metalheadjoe 10+ year member]

 

[Kybassbwoy]

I'll always opt for an amp that makes what I need (or a little more) at 4ohms and twice what I need at 1 ohm. Everything plays nicer at 4 ohms when it can do much more at 1 or 2. Size is no longer a "huge" factor (pun intended) anymore and power is cheap. Unless one cannot afford too, that's the way I roll.

This x2, exactly. It's been my experience that 4 ohm operation sounds better to the ear. Never more than 2 ohms for me, and 4 is better. Worth the cost