[Billfitz]

Didn't I already show you the midrange frd in a PM? All crossovers work best when optimized for the frequency response (frd) and impedance (zma) of the drivers.

[RocketBoots]

You did! It was just the frd of the mid. Quite decent. No zma or T/S parameters, no data on the tweeter. No worries, I don't need them; was just curious.

[btx3M40]

I have a 2020 G01 M40 and other than the bass I find the HiFi system to be OK for what it is - Im not looking for higher SPL. I want the subs to go deeper with less boomy / resonant mid-bass. I’ve thought about adding a JL sub to the underfloor area, but I really like having that space for storing the old man crap I like to have in the car - tool kit, inflator for snows, wash products, etc. While this thread and other have clearly outline the limits in what can be achieved under seat, I’m hoping an incremental step will be enough.

So here is what I have in mind:
Technics add-a-sub harness: https://technicpnp.com/product/hifi-...-systems-copy/
Kicker Key 500.1 amp https://www.kicker.com/key-5001-1-ch...mart-amplifier
SWS 8xi: http://earthquakesound.com/index.php...rs/item/sws8xi

I’m a bit skeptical about the auto eq given there is no mic to measure the response - and little detail on their “AI tuning”. I’ve tried to find a DSP subwoofer amp but having seen any others - I could use a 2 channel full DSP amp but they can get pricy enough that it staets making more sense to to step up to a 7 channel amp - which is more $$. I had luck adding a small 8” JL sub into a modified factory sub box I got off eBay to my E53 X5 a number a years ago and I’m hoping I can find a simple upgrade for this system.

[Billfitz]

I can't comment on the Kicker amp other than to say it appears to have adequate power for a pair of Earthquake subs. Technically it should be able to power a pair of the 2 ohm version, being rated for 1 ohm operation, but I'm reticent about running any amp at its minimum load rating. I'd be inclined to use a pair of 4 ohm drivers, for a 2 ohm load. Shop around on both the amp and speakers, there's no reason to pay retail.

[mike082802]

i have harmon kardon and looking to pick up a set of sws8, there is a set of the 4 ohm local, i saw this MB Quart NA2-400.1 Compact 400 watt Mono Amp and would pair with a lci2 or wavetech link 2, just wondering how this compares to the audiocontrol acm1.300

https://www.amazon.com/dp/B06VT7XSYC...v_ov_lig_dp_it

thanks

[J555]

Originally Posted by mike082802

i have harmon kardon and looking to pick up a set of sws8, there is a set of the 4 ohm local, i saw this MB Quart NA2-400.1 Compact 400 watt Mono Amp and would pair with a lci2 or wavetech link 2, just wondering how this compares to the audiocontrol acm1.300

https://www.amazon.com/dp/B06VT7XSYC...v_ov_lig_dp_it

thanks

Why do you plan using a mono amp to feed two stereo woofers?

[btx3M40]

Originally Posted by J555

Why do you plan using a mono amp to feed two stereo woofers?

Frequencies below 200 hz or so are non-directional — the two woofers can be connected in parallel then connected to the mono output of the amp

[J555]

Originally Posted by btx3M40

Frequencies below 200 hz or so are non-directional — the two woofers can be connected in parallel then connected to the mono output of the amp

I thought the sound becomes directional at lower frequency. Anyway, asked out of curiosity, as you can hear and feel the stereo from the woofers and personally would definitely keep it.

[Billfitz]

Originally Posted by btx3M40

Frequencies below 200 hz or so are non-directional

It's not solely that they're not directionally locatable, it's because since they're not directionally locatable the low frequencies on recordings have been summed to mono since the 1980s. What makes low frequencies seem to be coming from the left, right or center isn't the low frequencies, it's the harmonics of those low frequencies, which are radiated by the rest of the speakers.

[mike082802]

Originally Posted by Billfitz

It's not solely that they're not directionally locatable, it's because since they're not directionally locatable the low frequencies on recordings have been summed to mono since the 1980s. What makes low frequencies seem to be coming from the left, right or center isn't the low frequencies, it's the harmonics of those low frequencies, which are radiated by the rest of the speakers.

any experience with the mbquart amp i mentioned or thoughts on it as compared to the audiocontrol as you seem to have a lot of knowledge?

[Billfitz]

No personal experience. Johnung vouches for his AudioControl. https://f30.bimmerpost.com/forums/sh....php?t=1730058

[adc]

Originally Posted by Billfitz

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.

Where does this correlation come from?

I realize I’m quoting an old post but I’m curious...

[adc]

Originally Posted by 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.

Not quite so.

I have the HK L7 system in my car and did the following incremental changes:
1. First I swapped the door sail panel tweeters for a nice set of silk tweeters, to get rid of what I perceived to be unbearable OEM harshness (causing listening fatigue) in the high frequency spectrum. Result was only about 50% of expectation, most likely because I didn’t properly match the new tweeters to the amp, xover and mid ranges.
2. Swapped the door fronts with BavSound stage 1, bought here used on the forum. This actually increased the volume for highs a bit, but also improved the clarity. Voices became clearer, harshness was gone but I ended up tweaking the EQ to bring down the highs (personal preference). Result was about 75% of expectation, definitely worth it at secondhand prices.
3. Swapped underseat mid woofers with Earthquake SWS, can’t recall which version but most probably the 4 ohm ones. After tweaking the EQ, bass was improved in the following perceived way: a little bit lower (could be placebo) and a lot tighter (more punch, more responsive, less muddy). Result was about 85% of expectation.
4. Swapped all rear speakers and the center channel with speakers packaged specifically for the L7 by a US eBay seller. Could be Dayton speakers or something else I’m not sure and he’s not saying. Minor improvements in clarity only noticeable when sitting in the rear seats. Result was about 30% of expectation but they were cheap compared to BavSound so I decided to just leave them in.

At each step I “isolated” the frequency range I was trying to improve via the inbuilt EQ and upgraded just one side of the car at a time. I played music I was familiar with and alternated the balance from left to right, eyes closed, to try to hear improvements. The idea being that if none were detected I’d just swap back to stock. But I definitely found differences, most time for the better and in no uncertain terms.

My friend with his L7 equipped M4 was recently available to compare, and we both find my updated system “better”. Areas we both agree are improved is midrange clarity, upper frequency reduced listening fatigue, and punchier/snappier bass.

To summarize at least with the L7 amp which allows EQ tweaking and sports more power compared to the standard HiFi, changes 2 & 3 above were worth it to me.

If anyone in the DC a area wants to pop in and have a listen, compare to your car, just send me a PM.

[Billfitz]

Originally Posted by adc

Where does this correlation come from?
I realize I’m quoting an old post but I’m curious...

Search 'Hoffman's Iron Law'. It's why you're not getting out of your Earthquakes what you would if they were separately powered.

[OcmRz3r]

Originally Posted by Billfitz

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.

Originally Posted by adc

Where does this correlation come from?

I realize I’m quoting an old post but I’m curious...

Billfitz seems to have gotten that backwards - higher BL (i.e. stronger motor) allows a reduction in enclosure size. The problem is that higher BL increases electrical damping (Qes), reducing sensitivity around and above Fc (closed box system resonant frequency).

An often-used analogy for understanding speaker mechanics is a weight on the end of a spring. If you pull down on the weight and let go, the weight will bounce back and forth at a steady frequency - this is Fs. Increase the weight and the frequency slows down. Decrease the stiffness of the spring and the frequency slows down. Weight in the speaker is anything that moves - cone, dustcap, a portion of the spider and surround, voicecoil and former. The spring is the suspension (and also the air in the enclosure). This stiffness in the suspension is the compliance, T/S params C and Vas. Reducing the size of the enclosure increases that stiffness, but the stronger BL can compensate for that.

A good transducer designer increases the cone or other moving mass only as a last resort. You want the lightest cone possible, but the cone needs to be rigid enough and damped enough. 1/4in thick steel is obviously overkill, but tissue paper won't do either. This is one of the areas in transducer design that doesn't involve negative trade-offs with other parameters - a good light, stiff, damped cone is always better. It just requires better materials and better design, and usually more money.

[OcmRz3r]

Originally Posted by btx3M40

Frequencies below 200 hz or so are non-directional

Originally Posted by J555

I thought the sound becomes directional at lower frequency.

Worth noting that there is a difference between "directional" and localizable. Directional is a function of the ratio of the wavelength to the size of the speaker radiating the sound. As the wavelength gets short relative to the size of the speaker, the radiation pattern becomes increasingly narrow. This is called beaming, and has nothing to do with frequency, at least in theory - a 50 foot diameter speaker would beam subwoofer frequencies.

Localization on the other hand has to do with how our ears and brain function and figure out where a sound is coming from.

[Billfitz]

Originally Posted by OcmRz3r

Billfitz seems to have gotten that backwards - higher BL (i.e. stronger motor) allows a reduction in enclosure size.

Higher BL doesn't increase Qes, it lowers it. Higher BL/lower Qes allows a reduction in enclosure size, but at the cost of low frequency sensitivity. Compensating for that loss of low frequency sensitivity requires more power, and the requisite Xmax and Pe to make use of it. It still comes down to Hoffman's Iron Law being inviolable. With respect to the goal of a speaker that's small, goes low and has high sensitivity, you can have any two of those properties, but you can't have all three.

[adc]

Based on some posts in this thread, the HK L7 OEM amplifier puts out significantly more power than the HiFi amp. The highest I've read here, by someone who seems a lot more authoritative than me, is 125W / 8 Ohm.

If this is correct, would it explain the empirical observation of those who have installed SWS or other non-OEM mid woofers in the underseat locations, and found improvements?

Meaning, assuming that a "better" speaker is one that goes lower at the expense of sensitivity.

[Billfitz]

The SWS goes lower than stock, and most other replacements. Technically the L7 will make better use of its capabilities than the Hi-Fi amp. However, for the SWS to operate optimally one must drive it considerably harder than the stock woofer. There's no provision in the system to independently control the woofer and midrange/tweeter levels. To some extent the EQ may be used to send a higher level signal to the woofers, but it's not a perfect solution. Separately amplifying the woofers gives that ability, while the accompanying reduction of the load on the L7 power supply provides additional headroom to the midrange/tweeter amps, reducing distortion.

[adc]

Originally Posted by Billfitz

The SWS goes lower than stock, and most other replacements. Technically the L7 will make better use of its capabilities than the Hi-Fi amp. However, for the SWS to operate optimally one must drive it considerably harder than the stock woofer. There's no provision in the system to independently control the woofer and midrange/tweeter levels. To some extent the EQ may be used to send a higher level signal to the woofers, but it's not a perfect solution. Separately amplifying the woofers gives that ability, while the accompanying reduction of the load on the L7 power supply provides additional headroom to the midrange/tweeter amps, reducing distortion.

The EQ probably has +/- 6dB if not more on each frequency band, so I'd say it is reasonably effective.

When the weather warms up I'll conduct an experiment with my friend. We'll play some type of pink noise in both cars, and record the output with a phone app. Assuming there is a good Android phone app for this.

[Hansie]

Think a decent mic is more important than an app.

[adc]

Originally Posted by Hansie

Think a decent mic is more important than an app.

I can get one if there is any recommendation. My Samsung has the classic mic/headphone jack so it should not be a hard burden.

Any idea which mic to get?