[CAMSHAFT]

Check it out. I spent a few hours collecting data from all of the past and current subs on the market. The cost may not be correct but most of the T/S should be good.

[johnung]

Originally Posted by CAMSHAFT

Check it out. I spent a few hours collecting data from all of the past and current subs on the market. The cost may not be correct but most of the T/S should be good.

[IMG]https://i45.photobucket.com/albums/f...40.32%20PM.png[/IMG]

Earthquake SWS-8X (4-ohm) and 8Xi (2-ohm) paid $218/pair shipped. Also bought pair of Earthquake spacer rings with wiring terminals in stock BMW location for $20/pair. Well worth it!

[Billfitz]

Originally Posted by CAMSHAFT

most of the T/S should be good.

I don't see any T/S specs on that chart. The lack of published T/S (Thiele/Small) specs for most drivers is the reason why it's impossible to make definitive comparisons between them.

[Kevin @ Integral Audio]

And sadly even what is listed is not accurate (I'm guessing those are all self-reported numbers by the "manufacturers**").

Any of the Sensitivity numbers much above 90dB should be considered highly suspect. The GRS for example is definitely not 96.8dB, and if it actually was you wouldn't want it because to get that high Fs would be so high it would be unusable as a woofer.

The Resistance listed for most of them is the nominal resistance, what actually matters is DCR and an impedance sweep.

The actual Frequency Range is dependent on many other things, and should definitely be ignored.

The power handling numbers also raise an eyebrow, and without seeing the reported test conditions don't mean anything. An accurate RMS power handling number is useful, Peak Power is a pretty useless metric. Most (probably all) of these would be displacement-limited before they hit that number unless they are high-passed.

[Kevin @ Integral Audio]

Originally Posted by Billfitz

I have the Audison specs, that's how I know the OEM Hi-Fi woofer is better. I have the OEM H-Fi woofer specs because I measured mine. I'm not picking on Audison, or anyone else. If their specs show that they have an advantage over OEM I'll say so. I've said so with the SWS Earthquake.

I'd be interested to hear what you're basing that on, or under what conditions you think the Earthquake is better. With the OEM amp (and which, HIFI or HK? In which vehicle?) Or do you mean with different amplification? I can say with absolute certainty that the Earthquake is inferior to the OEM woofer in both output and frequency response when used with the OEM amps, and that it is also inferior to at least some of the other woofers on that list when used with aftermarket amplification.

[Billfitz]

I've addressed that question numerous times, including in this thread.

[Kevin @ Integral Audio]

Originally Posted by Billfitz

I've addressed that question numerous times, including in this thread.

Ha. Well sadly I don't have the time that you seem to have for posting (or searching) on this forum. Wish I did given that I pay for the privilege.

Whatever your assumptions or conditions, what I said holds true.

[CAMSHAFT]

Originally Posted by Billfitz

I don't see any T/S specs on that chart. The lack of published T/S (Thiele/Small) specs for most drivers is the reason why it's impossible to make definitive comparisons between them.

While not listed in the T/S acronym format there are three in my list.

[CAMSHAFT]

Originally Posted by Kevin @ Integral Audio

And sadly even what is listed is not accurate (I'm guessing those are all self-reported numbers by the "manufacturers**").

Yes all were found on the manufacturers site.

Would you like to release yours?

[Billfitz]

Originally Posted by CAMSHAFT

While not listed in the T/S acronym format there are three in my list.

I only see RMS power, Pe. The Thiele/Small specs required to accurately model driver response are Fs, Qes, Qms, Vas, Re, Le and Sd. If you want to know maximum output capability you'll also need Pe and Xmax. There are a few more specs, but you can get by without them, as speaker modeling software will calculate them from those I listed.

[CAMSHAFT]

Originally Posted by Billfitz

I only see RMS power, Pe. The Thiele/Small specs required to accurately model driver response are Fs, Qes, Qms, Vas, Re, Le and Sd. If you want to know maximum output capability you'll also need Pe and Xmax. There are a few more specs, but you can get by without them, as speaker modeling software will calculate them from those I listed.

Keep looking, there are two more.

[Billfitz]

Price isn't a T/S spec, neither is sensitivity. DC resistance (Re) is, but the figures you have listed aren't DCR, they're nominal impedance (Z). Z isn't used in speaker modeling calculation, because its value varies with frequency. The actual impedance of a typical 4 ohm rated driver, for instance, will range from a minimum of perhaps 2.5 ohms to as high as 50 ohms or more at Fs. Frequency range isn't a spec, nor is peak power.

[johnung]

Originally Posted by Billfitz

Price isn't a T/S spec, neither is sensitivity. DC resistance (Re) is, but the figures you have listed aren't DCR, they're nominal impedance (Z). Z isn't used in speaker modeling calculation, because its value varies with frequency. The actual impedance of a typical 4 ohm rated driver, for instance, will range from a minimum of perhaps 2.5 ohms to as high as 50 ohms or more at Fs. Frequency range isn't a spec, nor is peak power.

What T/S specs do you have for the stock subs and the Earthquake SWS? The specs that I have for the SWS don't list T/S specifically. They do list:
Revc. (Ohms) 3.500, Fo. (Hz) 30.394, Sd.(msqM) 22.000, BL. (TM) 6.210, Qms. 3.987, Qes.0.804, Qts. 0.669, SPLo. (dB) 86.7, Vas. (Ltr) 27.830, Xmas (mm) 23

Speaker diameter 8"
Mounting depth 2 1/8"
Cut out 7 7/8" or 8 1/8" (unclear)
Weight 8 lbs
Voice coil diameter 1.5"
Aluminum bobbin
Power RMS 150W
Power MAX 300W
Revc for SWS-8X = 3.76 Ohms
Revc for SWS-8Xi = 1.76 Ohms

[Billfitz]

Those are the SWS T/S specs. They don't mention T/S in the manual where they're published, probably assuming that anyone who knows what they mean also knows what they are.
My hi-fi woofers measured as Fs 51 Hz, Qes 1.00, Qms 3.02, Vas 18.4L, Re 2.4 Ohms, Le 0.22 mH, Sd 200 sq cm. You can see that the most significant difference between them is Fs, 30Hz versus 51Hz. To put the significance of that in layman's terms the mass of the moving parts of the SWS is more, 53g versus 30g for the OEM, so it resonates at a lower frequency. That allows the SWS to play lower than OEM. The trade off is that more moving mass requires more power to move it. That's compounded by the higher Re of the SWS, so it takes 2.5 watts into the SWS to reach the same level as the OEM reaches with only 1 watt.

[pete in fate]

These show to fit as well. They lower the bass response to 25hz from the factory 50hz.
https://www.infinityspeakers.com/sub...Woofer+8s.html

[Billfitz]

The Infinity Flex 8S doesn't go lower than the OEM hi-fi woofer. This compares both in the same OEM enclosure, both driven with 1 watt input:



Even with more power than the stock amp the Infinity is no better than OEM. While the voice coil power rating is 150 watts its 4.7mm maximum excursion limits it to only 25 watts capacity in the lows before distortion becomes excessive.

[CAMSHAFT]

Originally Posted by Billfitz

Price isn't a T/S spec, neither is sensitivity. DC resistance (Re) is, but the figures you have listed aren't DCR, they're nominal impedance (Z). Z isn't used in speaker modeling calculation, because its value varies with frequency. The actual impedance of a typical 4 ohm rated driver, for instance, will range from a minimum of perhaps 2.5 ohms to as high as 50 ohms or more at Fs. Frequency range isn't a spec, nor is peak power.

Fs and Znom are on there...

[Kevin @ Integral Audio]

Originally Posted by CAMSHAFT

Yes all were found on the manufacturers site.

Would you like to release yours?

I'll do better than that. I'll post ours as well those for most if not all of the others being discussed here. It'll be part of a larger set of posts as well as probably some giveaways or something.

I understand that folks are desperate for info that will tell them something about the quality of what they are buying, but T/S params are really NOT that info. Generally speaking T/S params describe whether or not a speaker is suitable to a particular task [think: the difference between a 300HP 4cyl twin turbo and a 300HP 10cyl truck diesel]. They are what are called small-signal parameters - other than Xmax they are taken with minimal movement of the voicecoil (and Xmax usually can't be trusted). The reason they don't really tell you anything about quality (again, for the most part) is that they a) they assume linear behaviour and b) they only describe the low frequency behaviour of the driver. If you want an indicator of quality, you want to see frequency response and distortion measurements. Flat frequency response, well-behaved off-axis response, and low distortion all within the passband are your indicators of quality. And those only tell you if there ARE problems, they don't tell you WHY. For that you need Klippel or Dumax that will tell you that, for example, there is a significant asymmetry in motor force factor (Bl) because of a flaw in the motor design. The only thing professional designers use published T/S params for is deciding whether or not to order samples, assuming you are using an off-the-shelf design in the first place. We always measure ourselves and measure multiple samples, and then move on from there.

TL;DR: T/S params (assuming they can be trusted) really only tell you if the speaker can do a particular job; Freq Resp and Distortion tell you if it does the job well; and Klippel/Dumax/other can tell you why it is or isn't doing the job well.

At the end of the day the quality of a individual speaker comes down to three things: quality of the design/engineering, quality of materials, and quality of manufacturing. T/S params give almost no clues about any of those. And - most importantly - all other things being equal the systems design has a much greater impact on final sound quality than an individual driver. For better or worse, the majority of our customers are audio professionals of one sort or another. None of them ask me for T/S parameters. Ever. They know they aren't of any use. What gives them confidence that our systems will deliver the results they want? They look at our crossovers and realize that we are designing truly vehicle-specific crossovers. They see our midrange and instantly recognize that it is a version of the ScanSpeak 10F, a known quality driver. They see our measurement process and realize we actually understand what is happening acoustically inside the vehicle, etc.

I hate to say it but this thread is a great example of why we haven't bothered publishing any T/S or other data. The data tends to be misunderstood, misinterpreted, or misused. It isn't what you should be using to make a decision. Give me some time and I'll put together and post all the data we've got, as a complete picture.

[jedi-knight83]

Interesting reading... and I think I'm going to re install my OEM 'hi-fi' speakers to see if there is any difference.

I have a UK F31 with the 'hi-fi' option.
I installed Rainbow IL-C4.2 door components and Rainbow IL-S8F underseats = Not much difference.
Then I installed the Match up7bmw amp = a noticeable if not groundbreaking improvement (Still feed I need to play with the DSP to get the most out of it)

One thing I've realised now though having read this thread is that the up7bmw outputs the sub channels in 2ohm. I'm not sure what impedance the Rainbow IL-S8F subs are though? I believe they are 4ohm.

What is the negative reality of running a 4ohm sub with the 2ohm amp output?

Would I be better off getting 2ohm subs?

Thanks in advance.

[jedi-knight83]

Just to add. It looks like the OEM set up for the "hifi" system is that the underseats were 2ohm and the doors were 4ohm.

So in theory, my old OEM subs at 2 ohm will be better than these Rainbow S8F's at 4ohm?

[Billfitz]

Originally Posted by jedi-knight83

What is the negative reality of running a 4ohm sub with the 2ohm amp output?

There is no 2 ohm output. What the amp impedance spec refers to is the lowest impedance load that it can safely handle. You shouldn't use a load smaller than the amp rating, you may use a load that's higher.

Would I be better off getting 2ohm subs?

Maybe, maybe not. If all else is equal a 2 ohm driver will be louder, by 3dB, than a 4 ohm driver with the same signal input. The problem is that all else is seldom equal. Also, the maximum output of 2 ohm versus 4 ohm drivers is the same, again if all else is equal, when both are driven to their maximum capacity. The advantage to 2 ohms there is that it takes 0.7 times the drive voltage at 2 ohms to reach that maximum compared to 4 ohms. The disadvantage is that 2 ohms takes twice the current. So if you have an amp that's long on voltage capacity but shy on current it's better off using 4 ohm drivers. Conversely, if you want to run 2 ohm drivers your amp doesn't need as much voltage capacity but it does need higher current capacity.
I can't say if your OEM woofers are 2 ohm or not, but mine (USA Hi-Fi option S676) are nominally 4 ohm, with 2.4ohm DCR. I can't find any data on your Rainbows, only the usual unsubstantiated advertising blather.

[zeikei]

Originally Posted by Billfitz

I can't say if your OEM woofers are 2 ohm or not, but mine (USA Hi-Fi option S676) are nominally 4 ohm, with 2.4ohm DCR.

I have always thought they are 2 ohm nominal like it says in the sticker?