Gradient Axis 7" midwoofer

jr@mac

Visually, the driver very closely resembles the paper cone 7" from Dayton Audio - so I will not make much commentary other than to reiterate that I have always found the Dayton RS aluminum drivers to be ugly as hell, not sure why I find the looks of the paper versions so much more. 

To put to rest the inevitable questions - no, they are not the same driver subjected to "badge engineering". 

The similarities include:

1. Appears to be the same cone material with the exception that I think I remember the Dayton being somewhat "shinier"
2. Same voice coil diameter.
3. Same basket.

Now, perhaps somewhat obviously, the drivers share a common lineage - I don't care who specified what first since odds are, at heart, neither of these drivers contains any technology inherently creative - modern driver design at these price points isn't about who can engineer the next flavor of the month cone material or basket design. Rather, it is who is the most creative at combining off the shelf components into a high quality/value driver. 

Differences are somewhat striking, however. First and foremost is the impedance peak at Fs. The Dayton appears to be about 27 ohms - the Gradient is pushing 200 ohms (!!!). This indicates significant difference in motor design. 

There are differences in Qts. The Dayton advertises 0.34, the Gradient measured at 0.4.  Vas was 22 on Dayton, 18 on Gradient. Fs is higher in the Gradient (51/45) and sensitivity is close at around 90 each). Xmax is listed considerably lower in the Gradient (4mm vs 6mm). They both model very close to each other, with a slight nod in output above and below "the knee" to the Gradient. 

The two drivers are very similar in modeling, so what does the Qms of the Dayton being about 1/9th of the Gradient mean? 



Anyways, here is the free-air impedance sweep for the Gradient:


Here is a 500 and up zoom:


Some measured T/S:

Loudspeaker parameters:

Fs  = 51.07 Hz

Re  = 7.09 ohms[dc]

Le  = 260.27 uH

L2  = 414.76 uH

R2  = 14.16 ohms

Qt  = 0.41

Qes = 0.42

Qms = 11.13

Mms = 12.19 grams

Rms = 0.351322 kg/s

Cms = 0.000797 m/N

Vas = 17.96 liters

Sd= 126.68 cm^2

Bl  = 8.083987 Tm

ETA = 0.54 %

Lp(2.83V/1m) = 89.97 dB

Added Mass Method:

Added mass = 21.00 grams

Diameter= 12.70 cm

Compare to advertised found in this document (get it while you can - MCM has a history of making NLA driver data sheets or even 'sorry NLA' links disappear):

http://www.mcmelectronics.com/content/ProductData/Spec Sheets/55-5595.pdf

Based on the advertised FR curve - the blip in the impedance at around 1250 means there might be some work to do if the driver is crossed closer to 2k than not. 

All in all, for the $13 and change I paid for each of the quad I ordered I am betting they will perform juuuuust fine in a 2-way. 

jr@mac

One other note - I bought these (and the other Gradient stuff) without looking at the data sheets. When MCM advertised it as a "6 inch", I expected it to be the equivalent of the very misnomered Dayton RS "6 inch". What Dayton calls the 6 inch, is actually what Gradient truthfully calls their 5" model - so when I ordered the 5" Gradient, I was expecting a 125mm frame, instead I received a pile of 150mm frame drivers - score. Just a side note, as I have actually butted heads with one of the PE employees over this somewhat deceptive marketing tactic. 

jr@mac

I missed out on the 10" - I actually had them added to this order, but I must have missed the last two by a minute... Dammitshitfuck anyways, I had plans for those bad boys.

kennyk

Damn, I'm bleeding speakers. Is there a 12 step for speaker builders?

jr@mac

I was so proud of myself for unloading almost all of my non-collectible drivers at DDIY, too. Now I have like 2,388 new drivers to look at on my shelf. I am an idiot, is generally the consensus - since I have like 7 hours a week where I am not working these day building speakers is pretty far down the list. But someday... right? Someday, I will use all of these in a glorious summer where I build 13 pairs of speakers. 

D1PP1N

Ill have to check their site again had some stuff in my cart but backed out. The dayton rs270p i jut got at 10.75 and the rs225 are 8.75 so those are close but yeh the rs150 i had was smaller than stated. I dont like that. The drivers do look quite nice JR. Looks like you scored some nice goodies. 

dcibel

jr@mac said:

Differences are somewhat striking, however. First and foremost is the impedance peak at Fs. The Dayton appears to be about 27 ohms - the Gradient is pushing 200 ohms (!!!). This indicates significant difference in motor design. 

I don't believe you are correct in this assumption. The size of a resonant peak is usually determined by the damping, in this case the high Qms is indicating differing suspension structure, not necessary a different motor structure. You will find that a high Qms and high Fs peak go hand in hand.

I'm not saying the motors aren't different, but that the assumption that they are because of the Fs peak is not correct.

dcibel

High Qms is also an indication of a non-conductive voice coil former. The Dayton line uses aluminum.

jr@mac

dcibel said:

High Qms is also an indication of a non-conductive voice coil former. The Dayton line uses aluminum.

Sooooo a significant difference in motor design. 

The two drivers have very close to the same Vas. Soft parts are probably very similar. 

dcibel

jr@mac said:

dcibel said:

High Qms is also an indication of a non-conductive voice coil former. The Dayton line uses aluminum.

Sooooo a significant difference in motor design. 

The two drivers have very close to the same Vas. Soft parts are probably very similar. 

Hey you asked the question

jr@mac said:

The two drivers are very similar in modeling, so what does the Qms of the Dayton being about 1/9th of the Gradient mean?

I guess in my mind I always think of the "motor" as the stationary parts, magnet, pole piece, etc. The significance of the voice coil former is really up to you to decide.

jr@mac

A motor has moving parts. A driver is an electric motor. There are differences in the motor. I didn't ask, I pointed out a difference in the motor is the reason a difference in the Fs peak exists. If there were a significant difference in compliance, I would have investigated that as a factor - there isn't, which is why I focused in the motor. 

Give me some credit, here. If I wanted to engage in condescension, I would pose a question as a newbie at some other forums. 

dcibel

Ok, well you asked what the difference in Qms meant, I even quoted it. If you knew that the difference was the voice coil former you could have just said so in your OP. Anyway, there's nothing else to say here since we both know what we're on about Moving on...

Killa

I call the magnet the "block", electricity/magnetic field the "fuel", and the rest is the "piston"