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      05-26-2018, 10:42 AM   #45
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What specs do we know about the BMW 'subs', besides impedance of 2 or 3 ohms (?)? I bet we don't know sensitivity....
So to plug in one of those 8ohm ~82 sensitivity subs, would we just need a good amp?

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      05-26-2018, 11:43 AM   #46
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I believe they're 4 ohms. But as I've said, there's only one way to know how any driver will work, that's by using speaker modeling software to compare the results of the original drivers versus potential replacements. That necessitates having the driver Theile-Small specs, which I've not been able to find for the stock drivers. I've also expressed my opinion that no matter what amp and driver you use the size of the under seat enclosures are a major limiting factor. If you want/need significantly better bass than stock a separate amp and trunk mounted sub is the most logical, and probably economical, way to get it.
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      05-26-2018, 02:55 PM   #47
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Quote:
Originally Posted by Billfitz View Post
I believe they're 4 ohms.... I've also expressed my opinion that no matter what amp and driver you use the size of the under seat enclosures are a major limiting factor. If you want/need significantly better bass than stock a separate amp and trunk mounted sub is the most logical, and probably economical, way to get it.
But, but, you said:
"Looking under my seats it appears that you could use a standard driver installed facing down, leaving the vented covers off. The frame/magnet would stick up above floor level, but it looks like there's room enough so that it wouldn't interfere with the seat. That opens up the possibility of using much less expensive but very high quality drivers, for instance:
https://www.parts-express.com/dayton...-coil--295-508
That driver mounting scheme would increase the effective volume of the enclosure for better results. It's not something I'm interested in myself, but it's a viable option to investigate."

I don't want "Brklyn" bass, but something better than the "Hoffman" challenged setup now in my car. I think your above idea, sort of a "free air" mounting (?), could do that. And at ~ 1/2 price of the approved brands...? Hey!

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      05-26-2018, 03:25 PM   #48
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I know what I said, and if I was inclined to make a change that's what I'd do, after I took out one of the stock drivers, measured its Theile-Small specs, modeled it in WinISD 0.7 (http://www.linearteam.org/), then modeled potential replacement drivers to see if any worked better. I'm just not inclined to do so right now.
Reverse mounting isn't free air, which is no enclosure. It just aims the front of the cone into the enclosure instead of upwards toward the seat. That doesn't affect anything, other than allowing one to use a driver that's too deep for the magnet structure to fit into the enclosure. BMW and direct replacements get around that by putting the magnet in front of the cone instead of behind it. That works, but most are outrageously priced, and as I've said none have conclusive data to prove their worth.
If you're the curious sort and want to try it just to see what happens the good news is that very good eight inch woofers can be had for $60 or less. One that might be worth trying is https://www.parts-express.com/dayton...4-ohm--295-376
I don't know if it will fit, you'd have to compare its measurements to the space under the seat. It's a bit of a pig in a poke, but since just about every direct drop-in doesn't post any real specs they are as well.
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      05-26-2018, 05:30 PM   #49
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Thanks Bill,

I appreciate the ideas. Now I guess I have to go under my seats with a tape measure.
Then maybe I can look at those funny Theile parameters....

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      05-26-2018, 09:52 PM   #50
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bavsound ghost or bimmertech alpha one

i didn't feel like starting a new thread for this. has anybody heard both and what are your thoughts? i am not interested in adding an external sub so no need to go there. just interested if either is a worthwhile upgrade over the hk underseat. "don't waste your time and money" is an acceptable answer for me, however a subjective answer like "sounds amazing" is not, i'd need more detail on why it sounds amazing. i have not found specs listed on either companies site. which is more efficient? i'm guessing the 7ohm Alpha1. i personally don't care for punchy and want a smoother roll off, maybe the ghosts? which has better frequency response and plays lower? about the same? thx in advance

edit: lmk of any other hk underseat plug n play replacements to consider

Last edited by alohasurftoad; 05-26-2018 at 10:01 PM..
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      05-26-2018, 10:13 PM   #51
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There are only two ways to give a definitive answer. One is to software model the drivers, which is not an option with no T-S specs. The other is to measure the results, before and after. Purely subjective opinions aren't worth much. People often say 'I know what I'm hearing', but one of the first things you learn in an advanced course in acoustical engineering is that you don't. On that topic:


Not exactly audio related, but still pertinent:


If you think something will sound better it will, especially if you just laid out a few hundred or more for it.
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      05-27-2018, 07:07 AM   #52
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"If you think something will sound better it will, especially if you just laid out a few hundred or more for it."[/QUOTE]

Or if you really want to have some fun, go to an advertising focus group, maybe a beer tasting. Talk about popping bubbles!
So let's pump Bill for more info!

Murf (in advertising for ~ 25 yrs....)
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      05-27-2018, 09:05 AM   #53
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More info? Also pertinent:
http://seanolive.blogspot.com/2009/0...o-product.html
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      06-18-2018, 10:50 PM   #54
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Quote:
Originally Posted by Billfitz View Post
There are only two ways to give a definitive answer. One is to software model the drivers, which is not an option with no T-S specs. The other is to measure the results, before and after. Purely subjective opinions aren't worth much. People often say 'I know what I'm hearing', but one of the first things you learn in an advanced course in acoustical engineering is that you don't. On that topic:


Not exactly audio related, but still pertinent:


If you think something will sound better it will, especially if you just laid out a few hundred or more for it.
This is overthinking the issue.

Is anything more important than believing it sounds better? Would you rather have a speaker that measures better but you think it sounds worse?
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      06-19-2018, 08:47 AM   #55
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Quote:
Originally Posted by glennQNYC View Post
Is anything more important than believing it sounds better? Would you rather have a speaker that measures better but you think it sounds worse?
To paraphrase Floyd Toole, 'I've never had a speaker that sounded good that didn't measure good, and I've never had a speaker that measured bad that sounded good'.

BTW, I did get around to measuring the specs on the drivers in my F34:

BMW Hi-Fi Woofer

Fs 51 Hz
Qes 1.00
Qms 3.02
Qts 0.75
Vas 18.4L
Re 2.4 Ohms
Le 0.22 mH
Sd 200 sq cm


BMW Hi-Fi Midbass

Fs 117 Hz
Qes 1.17
Qms 3.56
Qts 0.88
Vas 3 L
Re 3.2 Ohms
Le 0.23 mH
Sd 35 sq cm

If you know what these specs mean and how to use them it's obvious that these drivers are quite good. If not then you're a perfect customer for after-market drivers that are long on promises but short on facts.
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      06-19-2018, 08:54 AM   #56
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Quote:
Originally Posted by Billfitz View Post
Quote:
Originally Posted by glennQNYC View Post
Is anything more important than believing it sounds better? Would you rather have a speaker that measures better but you think it sounds worse?
To paraphrase Floyd Toole, 'I've never had a speaker that sounded good that didn't measure good, and I've never had a speaker that measured bad that sounded good'.

BTW, I did get around to measuring the specs on the drivers in my F34:

BMW Hi-Fi Woofer

Fs 51 Hz
Qes 1.00
Qms 3.02
Qts 0.75
Vas 18.4L
Re 2.4 Ohms
Le 0.22 mH
Sd 200 sq cm


BMW Hi-Fi Midbass

Fs 117 Hz
Qes 1.17
Qms 3.56
Qts 0.88
Vas 3 L
Re 3.2 Ohms
Le 0.23 mH
Sd 35 sq cm

If you know what these specs mean and how to use them it's obvious that these drivers are quite good. If not then you're a perfect customer for after-market drivers that are long on promises but short on facts.
Is anything more important than believing it sounds better?
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      06-19-2018, 09:13 AM   #57
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That same philosophy has been expounded by snake oil merchants since time immemorial.
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      06-20-2018, 09:10 AM   #58
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I've now had experience with the BMW HiFi sub in my wife's X5, my stock H/K sub in my f30, and the new version of the Bavsound Ghost Speaker in my H/K system.

I've sent back the Bavsound as it wasn't really adding anything on the low end, it did however add to the higher mid-range sound which I was not hearing much at all from stock. After going back to the stock H/K sub it is clear that the stock speaker goes lower but overall is not as responsive (sounds muddy). I plan on adding an amp to my stock H/K system with MusicarNW and they think I'll be pretty impressed with what the stock speakers can do when they are properly powered and tuned. Plus taking the low end away from the underseats will make them perform much better (adding JL 10W6).

By the way MusicarNW suggested the Earthquake underseat if you don't plan on adding a sub, it apparently has the best low-end performance in their opinion.
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      06-21-2018, 07:01 AM   #59
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Larry,

I've been running MusicarNW setups in my cars for a few years now. They won't lead you down the wrong path. Living in the same city as them is a serious plus for being in the Portland area.
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      06-21-2018, 09:42 AM   #60
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Quote:
Originally Posted by Larry77 View Post
By the way MusicarNW suggested the Earthquake underseat if you don't plan on adding a sub, it apparently has the best low-end performance in their opinion.
The Earthquake does offer a considerable improvement over the stock woofer provided it has enough power. The blue trace here shows the Earthquake SPL, the red trace the stock BMW woofer SPL, both in half-space in the same BMW enclosure. However, the Earthquake is driven with 150 watts, the BMW with 50 watts:



This chart shows them driven with the same 1.5v signal, and the stock BMW driver is the clear winner:



This points out the First Law of Acoustical Engineering: There's no such thing as a free lunch. Yes, you can make a driver that goes a lot lower than the stock BMW driver, but in return for going lower you lose broadband sensitivity. The Earthquake will work better than stock, but only if you upgrade the amp.
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      06-21-2018, 12:09 PM   #61
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Originally Posted by Larry77 View Post
I've now had experience with the BMW HiFi sub in my wife's X5, my stock H/K sub in my f30, and the new version of the Bavsound Ghost Speaker in my H/K system.

I've sent back the Bavsound as it wasn't really adding anything on the low end, it did however add to the higher mid-range sound which I was not hearing much at all from stock. After going back to the stock H/K sub it is clear that the stock speaker goes lower but overall is not as responsive (sounds muddy).
This is an example of the limitations of making definitive conclusions from modeling frequency response graphs alone. T/S parameters only tell part of the story. If it were that easy there would be no need for real-world testing. Moral of the story is trust your ears above all else. There is no substitute for a real-world experience.
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      06-21-2018, 12:37 PM   #62
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Quote:
Originally Posted by Billfitz View Post
The Earthquake does offer a considerable improvement over the stock woofer provided it has enough power. The blue trace here shows the Earthquake SPL, the red trace the stock BMW woofer SPL, both in half-space in the same BMW enclosure. However, the Earthquake is driven with 150 watts, the BMW with 50 watts:



This chart shows them driven with the same 1.5v signal, and the stock BMW driver is the clear winner:



This points out the First Law of Acoustical Engineering: There's no such thing as a free lunch. Yes, you can make a driver that goes a lot lower than the stock BMW driver, but in return for going lower you lose broadband sensitivity. The Earthquake will work better than stock, but only if you upgrade the amp.
Interesting. When you say the second chart shows them driven with the same signal, that means the same amp, for both? I've heard from quite a few people that even just switching the stock underseat subs with the Earthquakes should improve the bass, even with the stock amp.

So you're saying that won't be the case?

If you do upgrade just the speakers, what does it mean in layman terms when you say "you lose broadband sensitivity"? I don't know how to read these charts...
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      06-21-2018, 01:13 PM   #63
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The lower chart compares them with the same amp, same signal, same setting. The subjective result would be that the Earthquake would sound much thinner, with the volume significantly reduced, compared to the stock driver with the stock amp. In order to take advantage of what the Earthquake can do it needs a lot more power, and you'd need an amp that allows separate volume control over the woofers relative to the other speakers.
People who say that the Earthquake improves matters with the stock amp are succumbing to sighted expectation and placebo effect. The science is never wrong, whether you understand it or not. That doesn't mean that professional acoustical engineers like myself don't listen to the results, that is after all the entire point. But knowing the science allows us to take sighted expectation and placebo effect out of the equation.
Reading SPL charts isn't at all difficult. http://www.centerpointaudio.com/HowT...onseGraph.aspx
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      06-21-2018, 03:15 PM   #64
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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?
Would this be a good thing?

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      06-21-2018, 03:27 PM   #65
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Quote:
Originally Posted by Billfitz View Post
The lower chart compares them with the same amp, same signal, same setting. The subjective result would be that the Earthquake would sound much thinner, with the volume significantly reduced, compared to the stock driver with the stock amp. In order to take advantage of what the Earthquake can do it needs a lot more power, and you'd need an amp that allows separate volume control over the woofers relative to the other speakers.

People who say that the Earthquake improves matters with the stock amp are succumbing to sighted expectation and placebo effect. The science is never wrong, whether you understand it or not. That doesn't mean that professional acoustical engineers like myself don't listen to the results, that is after all the entire point. But knowing the science allows us to take sighted expectation and placebo effect out of the equation.
Reading SPL charts isn't at all difficult.

http://www.centerpointaudio.com/HowT...onseGraph.aspx
Wow, surprised to get such completely opposite opinions. I realize also you probably think it's not an opinion, but rather facts.

So if I'm understanding the chart, apples to apples, swapping in the Earthquake speakers, you'll get marginally better bass up to 50 Hz, but then it drops off a lot. Is that right? To the average person's ear, that would be noticeable and an overall negative experience?

***

I own a set of SWS-8X speakers (4 ohm) in boxes I never got around to installing in my 335. I'm getting the M2 in a few months, which comes with the HK (option 674) system in it. There's no plug and play harness like for other BMW systems that lets me add an amp just to power the subs AFAIK, so adding an amp isn't a possibility.

I figured if I could use my SWS's, that would be a bonus, instead of selling them. So I asked Technic who is a bit of a guru around the forums (when he used to post a lot) about whether they'd work, and he said to me:

The SWS-8 and spacers will work in your M2. We do not offer a 674 harness to power only the woofers. The SWS-8X should work better than the OEM woofers with the OEM HK amp in the M2 ZCP...

So I was going to take his advice and swap them in when I got the car, instead of selling the SWS's, but you've got me stumped what to do...

***

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?

I see even Bavsound's upgrade uses 2 ohm speakers:

https://www.bavsound.com/Product/bsd...rade-pair-2ohm
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      06-21-2018, 05:57 PM   #66
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Quote:
Originally Posted by Lotus99 View Post
...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?

I see even Bavsound's upgrade uses 2 ohm speakers:

https://www.bavsound.com/Product/bsd...rade-pair-2ohm
https://www.amazon.com/Earthquake-So...p?ie=UTF8&th=1

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