Can someone explain this impedance curve?

U130421

Disabled Account
2015-12-16 2:00 pm
This is the impedance of TAD ME1 measured by Stereophile magazine . What is the 20Hz resonance?
 

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YSDR

Member
2013-11-24 8:13 pm
That is the lower (in frequency) of the two impedance peak caused by the reflex loading.
The higher in frequency peak are probably damped by an impedance correcting LCR circuit to avoid peaking in the frequency response caused by the lowpass filter.
 

Galu

Member
2018-04-17 6:50 pm
The rear radiation from this woofer exits the cabinet through small openings on each side that feed into narrow slots that vent to the outside at the enclosure's front and rear. TAD calls this bass-loading design bidirectional ADS, for Aero-Dynamic Slot.
Not a conventional type of loading, but it looks to me like there is bass reflex action going on with a tuning frequency of around 40Hz as indicated by the impedance dip at that frequency.

The upper bass reflex hump (small in amplitude) occurs at around 50Hz and the lower bass reflex hump (large in amplitude) occurs at around 20Hz.
 

U130421

Disabled Account
2015-12-16 2:00 pm
I am trying to understand how the TAD CE1 does down to 34hz with 82db efficiency while using a high efficiency midrange driver as Eminence beta 8 type. For me this driver must have an efficient of at least 98db with resonance of about 70hz . From the impedance curve of TAD ME1 which uses the same driver is it possible to find out how it is attenuated/equalized.
 

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Think i know.

The ideal ported has a double impendence spikes approximately the same height.

I think to box is way larger than it needs to be.

Usually we see the right of the 2 spikes higher than the left, indicating the box is too small.


Maybe an ebs ported chart would be similar (bigger than needed, maybe tuning near f9 instead of f3).
 
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U130421

Disabled Account
2015-12-16 2:00 pm
That woofer has most likely 85dB sensitivity, which dictates overall efficiency of the speaker. To attenuate mid and tweeter is easy.
98 dB? Where did you pulled this number from?
It has a gigantic neodymium magnet driving light weight diagram, compare it with Eminence beta8 95db. I have 99db 12" neodymium woofer 4" voice coil with much smaller magnet.
 
It has a gigantic neodymium magnet driving light weight diagram, compare it with Eminence beta8 95db.
I have 99db 12" neodymium woofer 4" voice coil with much smaller magnet.
So you are *assuming* 98dB :eek: without any measurement to back that claim :confused:

Not the same, and FWIW deduct 3dB from "numbers" published by Eminence.

Their curves are fine, though, and faithfully reflect what I´m saying.
 

U130421

Disabled Account
2015-12-16 2:00 pm
So you are *assuming* 98dB :eek: without any measurement to back that claim :confused:

Not the same, and FWIW deduct 3dB from "numbers" published by Eminence.

Their curves are fine, though, and faithfully reflect what I´m saying.
I wish I had the specifications of this driver . My purpose is to estimate from different data I dispose. This is P audio SN8mb , it has a tiny neodymium magnet inside the voice coil of 2", with 2mm VC overhangs it has 95db efficiency. To have a 82db efficiency, either the diagram is heavy subwoofer with powerful magnet or light diagram with tiny magnet. The TAD driver with double plied surround, is a high efficiency midrange. I don't have slightest doubt it has a passive equalization that I am trying to find out, to replicate.
 

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giralfino

Member
2009-02-28 9:20 pm
I had a look at the Stereophile measurements. They estimate 86.2dB/2.83V/m for the speaker. Looking at the overall FR it is pretty evident that the manufacturer choose an almost full baffle step correction, so the "real" efficiency of the woofer should be around 90dB, maybe 91dB but not more. Your claim of 95dB simply doesn't make sense as no sensible manufacturer would attenuate a woofer.
What the speaker outputs at 34Hz depends heavily on the tuning. If you look at the graphs published, the tuning is at around 40Hz and the FR drops below 50Hz. My estimate is that at around 34Hz the speaker is at around 70dB, down 15dB from reference.

Ralf
 

U130421

Disabled Account
2015-12-16 2:00 pm
I had a look at the Stereophile measurements. They estimate 86.2dB/2.83V/m for the speaker. Looking at the overall FR it is pretty evident that the manufacturer choose an almost full baffle step correction, so the "real" efficiency of the woofer should be around 90dB, maybe 91dB but not more. Your claim of 95dB simply doesn't make sense as no sensible manufacturer would attenuate a woofer.
What the speaker outputs at 34Hz depends heavily on the tuning. If you look at the graphs published, the tuning is at around 40Hz and the FR drops below 50Hz. My estimate is that at around 34Hz the speaker is at around 70dB, down 15dB from reference.

Ralf
The speaker I am analyzing is CE1 has 82db efficiency 85db sensitivity 4 ohms woofer cut frequency 250hz. , no measurements I could find but that of ME1.
 

giralfino

Member
2009-02-28 9:20 pm
OK I see now, but you are confusing everyone if you ask something on a graph of a ME1, and then later you are referring to a different speaker.
Anyway, without any evidence but the manufacturer specs, I’d say that the CE1 woofer efficiency should be comparable to the ME1 at around 90-91dB, the final 85dB of the speaker is due to a baffle step compensation. The 34Hz of the speaker can easily be the -10dB point and not the -3dB point as you are thinking.
How the -10dB point relates to reference depends more on the tuning than on the driver alone (shallow vs steep slope).

Ralf