[Onizukachan]

Correct there is no BW for f3x. He’d be better off looking on the g30 forum. Or buying the g30 subs. If you are going to do something out of the box the need to research and execute is completely on you.

[leon7]

The B&W amplifier is similar to HK in terms of impedance requirements, just more powerfull.
I think i'll go with German Maestro's and come back with feedback.
Thanks everyone for advices.

LE: This is the specs for B&W amp:

7 tweeters, 12.5 W (3 x Nautilus Diamond, 4 x aluminium)

7 mid-range speakers 75 W (7 x Kevlar)

2 bass speaker, 250 watts

[gezzdoc]

Hi folks

I assume the signal to the underseat woofers in an F31 HK system is low-passed....

If so; does anyone know at what frequency?

[Billfitz]

My Hi-Fi signal is low passed around 100-120Hz. It's impossible to be more exact, as the measured response is affected by both the high passing and the EQ.

[J555]

Originally Posted by gezzdoc

Hi folks

I assume the signal to the underseat woofers in an F31 HK system is low-passed....

If so; does anyone know at what frequency?

It is and it does change with coding of certain headunit/amp options. No clue about the frequency, though.

[rcaso26]

I read the whole thread but I dont think this question was asked. I just installed a Bimmertech PP82DSP amp to my Hi-Fi speakers in my 2015 328. I am looking to add Earthquake SWS-8xi 2 ohm underseat subwoofers. I realize a more powerful amp would get the most out of the Earthquakes, but will the Bimmertech amp provide enough power to make the upgrade worthwhile from the stock Hi-Fi underseat subs? The spec list of the Bimmertech PP82DSP is below. Thanks in advance! I'm relatively new to car audio.

Output power RMS / max:
• All channels @ 4 Ohms: ............................................8 x 55 / 110 Watts
• All channels @ 2 Ohms: ............................................4 x 70 / 140 Watts
Frequency range .................................................. ...........20 Hz - 22.000 Hz
Number of input channels.......................................... ......4 x highlevel, 1 x Aux, 1 x SPDIF optical input
DSP resolution........................................ .........................56 Bit
DSP processing power............................................. .......172 MIPS
Total harmonic distortion (THD).......................................< 0,03%
Signal-to-noise ratio............................................. ............> 103 dB
Damping factor............................................ ....................> 50
Input impedance......................................... .....................30 Ohms
Undervoltage detection......................................... ...........9,6 Volts (max. 5 sec. down to 6 Volts)
Dimensions (H x W x D) .................................................. 44 x 185 x 164 mm / 1,73 x 7,28 x 6,46“
Additional features .................................................. .........HD technology with dynamically controlled power
supply, ready for start-/ stop, 56 bit digital signal
processing, internal memory for 2 different sound
setups, USB input, AUX input, optical input, input
for optional remote control, stereo line outputs
with balanced output transformers (floating
ground).

[Billfitz]

It's not just the power, it's also the ability to separately control the output level of the subs and the rest. If you can do that then the amp should work well enough. If not you can always add a separate sub amp.

[rcaso26]

Thanks for the response. Is this sufficient? The amp has 6 separate dip switches, 2 of which control the subwoofers. See below from the PP82DSP manual:

Switch no. 1 Switch no. 2 Amplifier overall gain
OFF OFF 0 dB
ON OFF - 4 dB
OFF ON + 2 dB
ON ON - 2 dB
Affects all eight output channels!

Switch no. 3 Switch no. 4 Subwoofer gain
OFF OFF 0 dB
ON OFF - 4 dB
OFF ON + 2 dB
ON ON - 2 dB

Switch no. 5 Mode switch URC 2A
OFF Mode switch on remote control bypasses MATCH sound optimization if pressed
ON Mode switch on remote control activates AUX input if pressed
Switch no. 5 has no function if remote control is
deactivated via switch no.6

Switch no. 6 remote control URC 2A
OFF remote control deactivated
ON remote control activated

Please note:
It is possible to deactivate / reactivate both Mode switches no. 5 and 6 via the PC-tool software.

[Billfitz]

The voltage sensitivity of the Earthquake woofer is about 4dB less than the OEM, so +2dB gain won't quite do the job, but you should be able to use EQ to get the level up to where you want it.

[barf]

Read through the whole thread...

So i have/had an european base audio F30 and since I'm in Europe it makes sense for me to source used H&K speakers because of ease of install and they are quite cheap here. If i had stock hifi or h&k i would not even bother but the pain of having base audio is too great.
I would have probably gone with full H&K system retrofit but i really can't be bothered with all of the wiring and optical connections etc.

Anyway currently I have:
*Audiocontrol LC6i high-low converter
*H&K underseat subs
*H&K door speakers with tweeters

So right now i'm thinking of 6 channels which LC6i supports fine, 2x front, 2x rear, 2x sub.
I would code the headunit for Hi-Fi option code so EQ would be more flat.
I have found such information from BMW technical documents:
Top HiFi amplifiers are audio amplifiers with partially active frequency diplexers. Active frequency diplexers achieve better acoustic results than passive frequency diplexers.

The Top Hi-Fi amplifier (AMPT) is a control unit on the MOST network which has the following functions:

Audio amplifier for tweeters and mid-range speakers 4 x 40 watts (alternatively 8 x 45 watts)
Audio amplifier for bass speakers 2 x 70 watts (alternatively 2 x 125 watts)
Vehicle-specific equalizing
Speed-dependent equalizing
Volume-dependent equalizing

Underseat woofers:
So according to this data for underseat woofers I would need 2x125W @ 8Ohm channels from an amplifier(minimum). The problem is that most amplifiers have the possibility of either LPF or HPF but not bandpass. What i have found is that i should be running HPF @ 60Hz because the woofers wont operate under 60Hz well and i would not even want them to (with going to SWS-8) since of small enclosure anyway. LPF @ 120Hz because of attenuation. I really do not want to buy an DSP yet because that would mean for me to go "fully invested" to this audio install and this is not something i'm ready for quite yet. So will i get a lot of problems with only running HPF @ 60Hz?

Mid+tweeter
Would use HPF @ 120Hz along with possibly replacing the capacitors with Billfitz recommendations taken from the other thread. I presume the channel is 45W. So i would require 2 ohm @ 45W minimum.

Subwoofer
Possibly would additionally be running 200W subwoofer in the rear left quarterpanel in the trunk LPF @ 60Hz.

So what you think. Mainly i'm worried about underseat woofer bandpass but i have no idea how it would sound in real life if i didnt limit higher frequencies. The factory base audio underseat woofers were in parallel with door speakers anyway...

[Billfitz]

If you don't high pass the underseats they will distort trying to handle frequencies below 50-60Hz. The reason Earthquakes work so much better than pretty much anything else is that they have much lower resonant frequency and longer excursion, which allows them to go low. BMW gets around this by using band pass filters on the underseat amp channels. That's why using a different underseat, even Earthquakes, is a waste of time with the BMW amp. The woofers can't deliver what the amp isn't providing.

[barf]

Originally Posted by Billfitz

If you don't high pass the underseats they will distort trying to handle frequencies below 50-60Hz. The reason Earthquakes work so much better than pretty much anything else is that they have much lower resonant frequency and longer excursion, which allows them to go low. BMW gets around this by using band pass filters on the underseat amp channels. That's why using a different underseat, even Earthquakes, is a waste of time with the BMW amp. The woofers can't deliver what the amp isn't providing.

I will be running 50-60Hz HPF but i can't bandpass since amp only has either LPF or HPF and i do not have DSP yet.

Anyway what you think about running underseats as mono? I think would not be much difference since they are under the butt anyway and running quite low frequencies.
The reason why i ask is because the amp i have for underseat woofers has RMS 240W @ 4 ohm 1 channel or 2x80W @ 4ohm so it would make much more sense for me to run underseat woofers in parallel as bridged mono resulting in 4Ohm impedance for the amp. I would later use this amp for trunk subwoofer if i go that route and then would get a better amp that can handle these 8 Ohm HK underseat woofers as stereo.
These lower power amps have a hard time with higher impedance because of output voltage, for 2 ohm can get higher power... Should have went with Hi-Fi woofers with 2 ohm imp, would have been easier on amp...

[Billfitz]

Underseats, and for that matter all subs, are always in mono. They may be powered by separate amp channels, but the low frequency content is summed to mono in the recording mastering process.

[Onizukachan]

Unless you play tracks with stereo bass Bill. I have a lot them.one of my favorites is “Electronic Music (stereo bass)” by Bass Mekanik (aka Neil Case). Some depeche has stereo bass some Van Halen does. A lot of orchestra recordings do.


However as bill implied, if they are crossovered low enough (sub 80 hz imo, others think 100) then it becomes very difficult to localize the source of the bass and your Brain will interpret the source as the same place as the high frequencies so running them in mono can work.

This assumes you have no harmonics/distortion occurring which would give away the location.

[Billfitz]

When you can locate the source of low frequency instruments or effects it's from hearing the harmonics, not the fundamentals. Being able to directionally locate any sound requires a significant degree of phase shift of the sound as heard by the right and left ears. The brain uses that phase difference to triangulate the direction of the source. When the distance between your ears is a significant portion of a wavelength enough phase shift, the result of the different arrival times at each ear, exists. That doesn't happen below 100Hz or so, where wavelengths are 12 feet or longer.

[moskito99]

I used to have default cheap stereo system with no amp and no tweeters in my e60.

I exchanged all speakers for used logic7 ones incl the subs plus added tweeters in front and back. Also I added an I-SOTEC amp (320W, 4x 80w, 4x 40w rms), but left cables as they are.

I coded from stereo to hifi (which made a HUGE difference, because stereo system is just breadband speakers and once you change to logic7 or others all is messed up unless you code your system to "hifi").

my question: I am using used logic7 subs....Are there alternatives worth looking into for a good price, or should I just stick to my logic7 subs?

THANKS!

[Billfitz]

Search 'SWS Earthquake'. You don't have to go very far, there are plenty of references just within this thread, as well as quite a few other threads.

[NealfromNZ]

In terms of this guide a couple of items need to be added when going with other choices.

The space between the mounting face of the woofer enclosure to seat rail is 78mm when considered considering conventional speaker drivers with magnet underneath.

I looked at a new driver ) SI TM8 that had a 58 millimeter depth which would have needed a 1 inch spacer. ( 25 mm ) and 12 mm of basket to top of surround . At linear xmax it needed a further 5mm clearance.

Basically it wouldn’t work without spacers under the seat mounting point.

The AD W800neo is also a driver that needs the seat mounting height raised when amplified to xmax. That should be mentioned on the first page as adding washers / spacers to set mounts is illegal in many countries.Many would
also consider this a safety tradeoff.

More recent additions to the woofer list
ESB and Morel also have additions for drop in bass and ideal when adding amplification on mid bass ( 180rms )As with any 8 inch choice these are more mid bass than sub

ESB have published their TS Specs. Morel need to do the same..

ESB

https://www.esbcar.com/bmw-sub-1


Morel

https://morel.com.au/ip-bmw-sub-82/
.

[Billfitz]

The ESB isn't the equal of the Earthquake. I've yet to come across anything that is, including the Stereo Integrity TM8 and Audio Development W800 Neo.

[NealfromNZ]

A Car audio SQ world champ and judge runs the ESBs in one of their vehicles ( wife’s). One of the better underseat drop in solutions from SQ pov in his humble opinion. Not cheap though.

Haven’t seen any reviews on the morels or any info on any one who’s installed.

Plenty of people remove the SVSs in search of higher quality and detail in mid bass performance. Often go AD W800 neos or focal utopia 8wm if they have deep pockets. But these are all cases where a subwoofer is used rather than lower F3 in the bmw underseat enclosure is sort.

Utopia link

https://www.focal.com/en/car-audio/c...-m/woofers/8wm
.

Erin has done a tech review on the AD w800 neos. Interesting is the xmax on these. Typically 4mm in desired range. Distortion performance looks very good. But unlikely to end up in my car due to spacing issue.

https://www.erinsaudiocorner.com/dri...pment_w800neo/

[Billfitz]

Originally Posted by NealfromNZ

Plenty of people remove the SVSs in search of higher quality and detail in mid bass performance.

That makes no sense. There is no 'quality and detail' in the pass band where the underseat woofers operate. That takes place well above 120 Hz. What they would get is higher sensitivity, which you'd want if you have a trunk sub. But if they had a trunk sub they never should have installed the SVS in the first place. Where sensitivity from 50-120Hz is concerned the stock woofer is as good as any.

I see nothing special about the Utopia, other than a silly price. 'Climbing up to the high mids' has no value when the underseats don't go to the high mids.

I'm familiar with Erin's testing of the W800 Neo. The THD is pretty bad, reaching 10% at less than half the mechanically calculated xmax. That might not cause a problem in practice, since the under seat location will acoustically filter out much of the above pass band harmonics that make up most of that THD. But still it shouldn't be happening. Erin sums it up by saying "This is a midbass driver. It is not a mid/woofer."

[NealfromNZ]

Thanks Bill. I think the owners that have swapped them out are using the underseat woofers in the 70 - 150 / 200 range to better blend in with door mids .

My S/h HKs have arrived so will try before putting anything else in. Next will be amp choice which will have 200 watts peak roughly at 8 ohms.

Interesting to compare the Base (6.5s )audio case verse Hifi / HK . HKs are substantial heaver and far more ridge. Baffle port has substantially wider and less square edges. Base audio are quite flimsy by comparison. The woofer looks very budget.