[Lotus99]

Originally Posted by Littlebear

https://www.amazon.com/Earthquake-So...p?ie=UTF8&th=1

Murf

Thanks, I know that the Earthquake subs come in a 2 ohm variety - I said that much in my post. I don't understand your point.

Are you saying the 4 ohm subs won't be a drop in replacement for the existing HK ones, if they are 2 ohm, if they'll still run off the OEM amp?

[Littlebear]

My only point is you can drop in 2 or 4 ohm units, depending on your upgraded amp, of course.
Really, I would wait to see if Bill says something....

Murf

[Billfitz]

Originally Posted by Littlebear

There is very little room under the front seat for fabrication. But to increase the volume of the underseat enclosure, could a circular spacer be made to push the driver up an inch or two, maybe out of MDF?

When I pulled a woofer to measure the Theile-Small specs I saw that the enclosure fits under the outer seat rail, so there's no real room to increase the box size. It's not necessary anyway, the sill that the enclosure shares space with gives sufficient volume for the driver to work well.

The one thing I was confused about with his advice was this: the SWS-8X's I have are 4 ohm, not the 2 ohm 8XI speakers. I thought though that the newer OEM subs were the 2 ohm variety? If that's true, how can I drop in 4 ohm speakers in place of 2 ohm ones?

If you want to use 2 ohm drivers the amp has to be able to work into a 2 ohm load safely. The OEM drivers aren't 2 ohm, thought they're closer to 3 ohms than 4. I wouldn't chance 2 ohm drivers with the OEM amp. The hi-fi amp doesn't have enough power to drive the SWS well enough to make the swap useful. The H-K amp might, but that depends on the H-K woofer specs, which may or may not be the same as the hi-fi woofer.

[Lotus99]

Originally Posted by Billfitz

If you want to use 2 ohm drivers the amp has to be able to work into a 2 ohm load safely. The OEM drivers aren't 2 ohm, thought they're closer to 3 ohms than 4. I wouldn't chance 2 ohm drivers with the OEM amp. The hi-fi amp doesn't have enough power to drive the SWS well enough to make the swap useful. The H-K amp might, but that depends on the H-K woofer specs, which may or may not be the same as the hi-fi woofer.

No, I don't want to use 2 ohm drivers... I already have the 4 ohm SWS-8X speakers.

I was just wondering whether I could follow Technic's advice and swap the stock ones with these, because I was under the impression that the stock subs are 2 ohm. And if they would in fact sound better, as he thinks.

Since there's no harness currently out there that allows you to add an amp to power the underseat subs, LIKE THIS they would still be running off the OEM HK amp.


PS If simply swapping speakers and using the same amp isn't going to yield much more bass, then is their claim of doubling bass just fluff?

https://www.bavsound.com/Product/bsd...rade-pair-2ohm

[Billfitz]

Originally Posted by Lotus99

I was just wondering whether I could follow Technic's advice and swap the stock ones with these, because I was under the impression that the stock subs are 2 ohm.

My hi-fi woofers that I measured aren't 2 ohms. Their resistance is 2.4 ohms, which translates to about 3.4 ohms impedance. I haven't measured H-K woofers, because I don't have them. If the H-K amp can handle a 2 ohm load then logically H-K would have specified 2 ohm woofers, but trying to get definitive specs is like pulling teeth from a worm.

If simply swapping speakers and using the same amp isn't going to yield much more bass, then is their claim of doubling bass just fluff?

Probably. You can get lower frequency extension with higher output, but not without increasing power. You can get higher output without increasing power, but it won't go as low. You can go lower without increasing power, but it won't go as loud. There's always a trade off, and there are no magic drivers. They all have to conform to the same laws of physics.

[Lotus99]

Originally Posted by Billfitz

My hi-fi woofers that I measured aren't 2 ohms. Their resistance is 2.4 ohms, which translates to about 3.4 ohms impedance. I haven't measured H-K woofers, because I don't have them. If the H-K amp can handle a 2 ohm load then logically H-K would have specified 2 ohm woofers, but trying to get definitive specs is like pulling teeth from a worm.

Probably. You can get lower frequency extension with higher output, but not without increasing power. You can get higher output without increasing power, but it won't go as low. You can go lower without increasing power, but it won't go as loud. There's always a trade off, and there are no magic drivers. They all have to conform to the same laws of physics.

Geez... Never thought this would become so complicated. Considering how many people have done these upgrades on the 3 series, I figured this would be an easy ask!

So would this plan work? When I get the car, I pull out the subs, and see what's the sticker on them say for impedence? I've seen pictures posted of subs, like this one, so it should say on it?

Bottom line, if they are in fact 2 ohm subs, then it's not a good idea to swap in my 4 ohm subs, right?



***

And I'm surprised to hear that about the Bavsound speakers... What you say makes sense. I guess they're trying to say that their speakers are somehow more efficient, so with the same power, can put out a lot more bass. And that's just not technically possible you figure?

I can see stretching things a bit, but $600 is really expensive if you're not really get much for it. They offer a 100 day in car trial though, which I'd be surprised they do, if they aren't really confident in their product?

[Littlebear]

Originally Posted by Billfitz

... the sill that the enclosure shares space with gives sufficient volume for the driver to work well.

Since the box is of a decent size, and I have two amps in already that are 2ohm safe (I think, I'll check), I think the 'moderately priced' Earthquake SWS8 looks like it should be an improvement in my car.

Murf

[bri1042]

In my three BMW's, all of which have been worked on by MusicarNW, the only Bass solution I ended up being happy with was Jehnert woofers under the seats and a trunk sub for real bass. I had Earthquakes in my e90 and, while they did play lower, they created a mid-bass hole at the hand-off to the mid-range speakers. Trunk sub to Jehnerts to upgraded mid's and tweets, tuned by MusicarNW. It was not cheap, but it has been the best car audio solution I have ever experienced.

Note: the Mid Bass "hole" was clearly in the range of male vocalists with deeper voices. Example: Dave Gahan of Depeche Mode didn't really sound like himself. I was warned about this when we did the Earthquakes but didn't take it that seriously. I wasn't entirely awful, but it wasn't good.

[Billfitz]

Originally Posted by Lotus99

Geez... Never thought this would become so complicated. Considering how many people have done these upgrades on the 3 series, I figured this would be an easy ask!

How many of them measured the results? I don't know what my industry colleagues are driving, but even if some have BMWs it doesn't seem that they're members here.

When I get the car, I pull out the subs, and see what's the sticker on them say for impedence? I've seen pictures posted of subs, like this one, so it should say on it?

It may have a sticker that shows impedance, it may not. Mine don't.

Bottom line, if they are in fact 2 ohm subs, then it's not a good idea to swap in my 4 ohm subs, right?

4 ohm drivers won't be as loud as 2 ohm, by 3dB to be precise. If you've got enough power to overcome that all well and good, but 3dB is a doubling of power.

I guess they're trying to say that their speakers are somehow more efficient, so with the same power, can put out a lot more bass. And that's just not technically possible you figure?

It's not. To go lower requires a higher mass cone, and that reduces sensitivity. That's what the Earthquake driver does. That lower sensitivity must be offset with more power. You can use a more powerful magnet structure to get higher sensitivity, but only if you also increase the size of the enclosure. You can use a lower mass cone to increase sensitivity, but then it won't go as low. You can get 3dB more sensitivity with a 2 ohm voice coil instead of a 4 ohm voice coil, but only if the amp is 2 ohm capable.

[Larry77]

I'm not sure if all H/K systems have the same under seat speakers but mine are around 7 ohm, not the mentioned 2 ohm. When I replaced them with Bavsound's they sold me their 8 ohm version.

[Lotus99]

Originally Posted by Billfitz

How many of them measured the results? I don't know what my industry colleagues are driving, but even if some have BMWs it doesn't seem that they're members here.

It may have a sticker that shows impedance, it may not. Mine don't.

4 ohm drivers won't be as loud as 2 ohm, by 3dB to be precise. If you've got enough power to overcome that all well and good, but 3dB is a doubling of power.

It's not. To go lower requires a higher mass cone, and that reduces sensitivity. That's what the Earthquake driver does. That lower sensitivity must be offset with more power. You can use a more powerful magnet structure to get higher sensitivity, but only if you also increase the size of the enclosure. You can use a lower mass cone to increase sensitivity, but then it won't go as low. You can get 3dB more sensitivity with a 2 ohm voice coil instead of a 4 ohm voice coil, but only if the amp is 2 ohm capable.

Thanks Bill. I think I'm starting to get the picture… If I am going to swap in new subwoofers, I need to first figure out the impedance on the OEM ones, and then best try to match them with the new ones. I want to avoid for the reasons above putting in 4 ohm speakers when 2 ohms are there, being driven presumably by a 2 ohm amp.

So if they're 4 ohms, I'm golden. If they're 2 ohm, then I'll have to sell my current set, and buy 2 ohm speakers to swap in. Whether then I get an improved bass response, and by how much to be worth it, is another question.

Right?

[Billfitz]

Originally Posted by Lotus99

Whether then I get an improved bass response, and by how much to be worth it, is another question.

Assuming the H-K woofers have similar specs to the hi-fi woofers you'd get better bass response with the SWS, but only if driven with enough power. Ideally you'd have separate amp volume controls for the woofers versus the mids and tweeters, but you don't. You can get around that to some extent with the H-K EQ, since what EQ does is to vary the amp output at each EQ frequency. But EQ can only do so much, because it eats up power. Even a 3dB EQ boost doubles the power the amp must provide, while a 6dB boost quadruples it. That's one more reason why if you want to get real piss-off the neighborhood bass it takes a trunk mounted sub with its own dedicated high power amp.

[Littlebear]

Originally Posted by Billfitz

... Ideally you'd have separate amp volume controls for the woofers versus the mids and tweeters, but you don't.

Pls forgive my ignorance, but won't the gain controls do this on a good amp?

I found specs on 2 replacement "subwoofers"!

Audiotec Fischer Match MW 8BMW-D:.
200 / 400 Watts
Frequency response 25 - 140 Hz
Impedance (Z) 2 Ohms
DC resistance (Re) 3.4 Ohms
Voice coil diameter (Ø) 42.5 mm
Voice coil winding height 12.5 mm
Max. linear excursion (Xmax) +/- 4.0 mm
Cone area (Sd) 214 cm²
Moving mass (Mms) 44.2 g
Mechanical resistance (Rms) 0.74 kg/s
Resonance frequency (Fs) 46 Hz
Mechanical Q factor (Qms) 4.45
Electrical Q factor (Qes) 0.59
Total Q factor (Qts) 0.52
Compliance (Cms) 272 μm/N
Equivalent air volume (Vas) 17.3 L
Force factor (B*l) 8.6 Tm
Voice coil inductance (Le) 1.1 mH
Efficiency 1W / 1m (SPL) 90 dB
Compatibility:
Suitable for all BMW model ranges with under-seat subwoofers

Doesn't play too high, but....


Earthquake:
Model: SWS-8X
EAN: 0-168975-910189
Size: 8" high performance sub
Fs: 20-300Hz
Max Power: 300W
RMS Power: 150W
Impedance: 4Ω
Sensitivity: 86.7dB
Qes: 1.372
Qms: 3.158
Qts: 0.957
Rvc= 3.400 Ohm
Sd=22.000m M²
Md= 50.000g
BL=5.837 T-M
No= 0.086%
SPLo= 81.4 dB
Vas= 716.361m Ft3
Cms= 295.150u M/N
Krm= 4.722m Ohm
Erm= 0.687
Mms= 55.805g
Mmd= 53.929m Kg
Kxm= 204.955m H
Exm= 0.257

Murf

[Billfitz]

I was referring to the BMW amp.
The Audiotech woofer has similar response to the stock BMW hi-fi woofer, but it's a bit less sensitive, so it won't go as loud with the same amp volume. It's not 2 ohm, it's 4 ohm. You can tell that by the Re, which is 3.4 ohms. Re is always lower than Z, never higher. The 200 watt rating is moot, the short 4mm xmax limits it to only 50 watts input at 50Hz before the cone runs out of travel. All things considered the BMW driver is better. Neither the Audiotec nor BMW go all that high, they're not supposed to. The mids take over around 120Hz.

[Littlebear]

Thanks Bill,
I can't find any specs on any other woofs. I thought these Audiotechs spec'd close to the Earthquake.
I'm surprised the little mids cross as low as ~ 120hz. Some of these 8" woofs go up to 200hz. Does that help with integration to the mids?

So we still be lookin'....

Murf

[Billfitz]

Originally Posted by Littlebear

Some of these 8" woofs go up to 200hz. Does that help with integration to the mids?

You don't want them to go much higher than 120Hz, because then the wavelengths get short enough to be directionally locatable. The reason why sub placement under the seats works is that you can't detect where their output is coming from, maintaining the imaging that makes the door speakers seem to be the only sound sources.

[brikabrak]

Originally Posted by Lotus99

No, I don't want to use 2 ohm drivers... I already have the 4 ohm SWS-8X speakers.

I was just wondering whether I could follow Technic's advice and swap the stock ones with these, because I was under the impression that the stock subs are 2 ohm. And if they would in fact sound better, as he thinks.

Since there's no harness currently out there that allows you to add an amp to power the underseat subs, LIKE THIS they would still be running off the OEM HK amp.


PS If simply swapping speakers and using the same amp isn't going to yield much more bass, then is their claim of doubling bass just fluff?

https://www.bavsound.com/Product/bsd...rade-pair-2ohm

I just installed the earthquake 2 ohms set today with the stock hifi amp and they sound superb.

I can't imagine them sounding better than they do.

[Littlebear]

Originally Posted by Billfitz

You don't want them to go much higher than 120Hz, because then the wavelengths get short enough to be directionally locatable. The reason why sub placement under the seats works is that you can't detect where their output is coming from, maintaining the imaging that makes the door speakers seem to be the only sound sources.

And my replacement door mids say they go down to ~ 110hz.
In my case, the language of this discussion is a little off. I really don't like big subwoofers. Even my living room 3-ways, tuned at the Brooklyn Navy Yard, top out at 10". The best integrated 8" underseat drivers, making a nice 3-way, is wot I want!

Murf

[Billfitz]

Until presented with objective data to prove otherwise I'm inclined to believe that the OEM woofers give as good a result as is possible with the OEM amplification. Most of the reason why it's widely assumed that an aftermarket woofer will work better is because they're expensive, but so are the stock woofers.

[Dog Face Pony Soldier]

Originally Posted by Billfitz

I'm inclined to believe that the OEM woofers give as good a result as is possible with the OEM amplification.

I agree with this. There are undeniable advantages to designing speakers, amplification and signal processing as a set.

[Littlebear]

Originally Posted by Billfitz

... I'm inclined to believe that the OEM woofers give as good a result as is possible with the OEM amplification.

Sure am glad I got rid of that OEM amp; that thing is tiny!

Now I have a JLAudio & an RF.

Murf

[Lotus99]

Originally Posted by Billfitz

Assuming the H-K woofers have similar specs to the hi-fi woofers you'd get better bass response with the SWS, but only if driven with enough power. Ideally you'd have separate amp volume controls for the woofers versus the mids and tweeters, but you don't. You can get around that to some extent with the H-K EQ, since what EQ does is to vary the amp output at each EQ frequency. But EQ can only do so much, because it eats up power. Even a 3dB EQ boost doubles the power the amp must provide, while a 6dB boost quadruples it. That's one more reason why if you want to get real piss-off the neighborhood bass it takes a trunk mounted sub with its own dedicated high power amp.

I would have loved to have something like this available for this car. This is the harness (or equivalent, depending on your car and system) that many people use and it allows you to have an amp in the trunk, but use it along with the stock harness and wiring to power just the underseat subs. Super stealth, cost effective and not a PITA.

I take it nothing like that exists right now for the M2 with the HK system? When I asked Technic, he said he doesn't have one, because the HK system is digital. And then someone else says it's NOT digital...

Originally Posted by cookiesowns

And to the comment about the HK system being digital on the M2.. that is not true.

The M2 gets the peasant HK system, it is not MOST bus based. The bimmertech amp will work:

https://www.bimmer-tech.net/speakers...ifier-for-bmw/

The one below is described as:

This one is used to add a trunk sub/amp to the OEM amp. Remote signal included. Please note that this harness is not compatible with Digital/MOST Top HiFi/HK/Logic7 OEM systems.

HiFi (676)/HK (674) add-a-sub harness/LOC