Take a Look at this Impedance and Phase Measurement

[TimW]

What do you think?

Easy or difficult to power?

Does the phase response look reasonable?

Can you guess what speakers these are?

I'm posting this and asking these questions because I don't really understand how to interpret these kinds of graphs. I have a basic understanding of impedance, this speaker dips down to almost 5 ohms in some bass frequencies. I would think it could be rated as a 6 ohm nominal speaker. I don't understand what the phase graph is telling me. I also notice small anomalies just under 40 Hz and just over 300 Hz. From what I understand these are most likely to be cabinet resonances.

 

[kaka89]

I asked the same question yesterday in another thread and got reply in here:
https://www.audiosciencereview.com/...br-62-speaker-review.12232/page-3#post-357898

My understanding is, you don't want to have phase shift and low impedance at the same time.

 

[RayDunzl]

Can you guess what speakers these are?

Nope.

Easy or difficult to power?

"Easier" than these:

 

[TimW]

So if we look at the impedance dip at around 250 Hz, the phase looks to be very close to 0 degrees at that point. However the phase curve at this point is at an angle, not flat. I guess I don't understand whether I should just be paying attention to actual phase degree, the angle of the phase curve at that point, or both. And how can I tell if it is really severe or benign?

I think I understand that you don't want to have low impedance dips along with steep phase angles because this makes for a difficult amplifier load. But I don't know how to identify this from the graph. I have listened to these speakers with various amplifiers, maybe they are not that difficult of a load, but I haven't heard much of any difference between the amplifiers. That has been my experience with most amplifier comparisons, no audible difference aside from noise levels and volume limit at the onset of clipping. Should I expect to hear other differences between amplifiers if they are both presented with a very difficult load? I'm just trying to wrap my head around why this is important.

 

[TimW]

Nope.



"Easier" than these:

View attachment 55864

The impedance dips very low. The phase graph is steep and far from 0 at that 60 Hz dip. I can imagine that would be difficult.

 

[RayDunzl]

However the phase curve at this point is at an angle, not flat. I guess I don't understand whether I should just be paying attention to actual phase degree,

The "degree" is the "angle". I wouldn't consider the slope of the line to be a consideration. For instance, at the worst angle the slope is flat (peak or trough).

And how can I tell if it is really severe or benign?

It seems to be a measure of amplifier stress. See link below.

I'm just trying to wrap my head around why this is important

Maybe read through this - https://sound-au.com/patd.htm

 

[TimW]

Thanks @RayDunzl

I actually became more interested in this topic because I'm building a modulus-86 amp, so this article is particularly applicable.

 

[SIY]

What do you think?

Easy or difficult to power?

Does the phase response look reasonable?

Can you guess what speakers these are?

I'm posting this and asking these questions because I don't really understand how to interpret these kinds of graphs. I have a basic understanding of impedance, this speaker dips down to almost 5 ohms in some bass frequencies. I would think it could be rated as a 6 ohm nominal speaker. I don't understand what the phase graph is telling me. I also notice small anomalies just under 40 Hz and just over 300 Hz. From what I understand these are most likely to be cabinet resonances.
View attachment 55863

Since this is a reflex, the glitches could also be port resonances.

 

[Doodski]

If you want some proper formal text on the matters. This is very good and essential reading. It can be found in most university libraries. The hardcopy is usually about $150.00 new for a large I think ~ 1300 page textbook.
https://www.amazon.ca/Principles-Electric-Circuits-Thomas-Floyd/dp/9332573883

https://www.academia.edu/40378782/P...urrent_Version_9th_Edition_by_Thomas_L._Floyd

 

[SIY]

Oh, and the slightly overdamped box (tuned to about 70 Hz) suggests that these will badly need subwoofers.

 

[solderdude]

What do you think?

Easy or difficult to power?

Easy for an amplifier that is designed to drive 4 Ohm speakers

Does the phase response look reasonable?

+/- 45 degree electrical phase isn't problematic.
The acoustical phase will be very different and is much more important

Can you guess what speakers these are?

No, should we ? All speakers measure differently.

 

[TimW]

No, should we ? All speakers measure differently.

I just threw that question in for fun.

But I would also like to add that the measurement was of a modified speaker. Here is the measurement of one of my unmodified units. Compared to the modified unit, the impedance of this one dips slightly lower in bass frequencies. Looks about equally difficult/easy to drive no?

Interestingly the glitches/wiggles happen at different frequencies.

 

[TimW]

Oh, and the slightly overdamped box (tuned to about 70 Hz) suggests that these will badly need subwoofers.

How do you know it is overdamped?

 

[SIY]

How do you know it is overdamped?

The relative magnitudes of the two peaks characteristic of a reflex.