[Larry77]

I just upgraded my Harmon Kardon f30 under-seat sub to a Bavsound Ghost sub and I'm wondering if the Harmon Kardon sub I had is better than my wife's HiFi under-seat sub in her e70 X5? If it is I'll swap them as mine were working fine.

Obviously I'll just take a look if nobody knows but thought I'd ask to see if I can save the trouble. Her HiFi bass was definitely subpar to my H/K bass in sound but I'm not sure if the difference is the amp behind it or the speaker itself?

[Billfitz]

The main limiting factor to what the under seat woofers can do is the size of the enclosures, so a driver swap may have little to no effect. The difference with the H-K is probably mainly attributable to the additional amp power and the EQ of the H-K. Even if the H-K driver has longer excursion, allowing it to handle more power than the hi-fi woofer, that might not make any difference without having the higher power of the H-K amp.

[alohasurftoad]

The f30 hk underseat is 8ohm. If your wife's hifi underseat is of lower resistance ie 4ohm, the stock hifi amp will struggle even more to push the hk.

[m95roadster]

Originally Posted by Billfitz

The main limiting factor to what the under seat woofers can do is the size of the enclosures, so a driver swap may have little to no effect. The difference with the H-K is probably mainly attributable to the additional amp power and the EQ of the H-K. Even if the H-K driver has longer excursion, allowing it to handle more power than the hi-fi woofer, that might not make any difference without having the higher power of the H-K amp.

Actually, the factory sub enclosure is not an actual enclosure, but really a baffle. If you notice in the pic there are rectangular cut outs which vent to the outside. So in reality the subs are in an infinite baffle.

[reddemon73]

Is it worth it to swap out hk subs with the bimmertech ones?

[Billfitz]

Originally Posted by m95roadster

Actually, the factory sub enclosure is not an actual enclosure, but really a baffle. If you notice in the pic there are rectangular cut outs which vent to the outside. So in reality the subs are in an infinite baffle.

It is an enclosure, in two parts, one part being that box that the driver is mounted to, the other the door sill compartment that the box vents into. Technically speaking that is an infinite baffle by the classic definition, which is when the front an rear waves do not meet, although today that term is usually applied to drivers mounted between rooms in a house wall or ceiling, or on a car rear shelf.

[m95roadster]

Originally Posted by Billfitz

It is an enclosure, in two parts, one part being that box that the driver is mounted to, the other the door sill compartment that the box vents into. Technically speaking that is an infinite baffle by the classic definition, which is when the front an rear waves do not meet, although today that term is usually applied to drivers mounted between rooms in a house wall or ceiling, or on a car rear shelf.

So is the door sill compartment completely sealed? If so, what do you think is the total airspace (ballpark)?

OP, sorry for thread derailing...

[Billfitz]

I would imagine it's sealed, otherwise puddles would be a bitch. How tightly it's sealed, or how tight the joint is between the box and the sill is, I can't say. I doubt it's even a cubic foot total, adequate for what it does, but just. Response is better than you'd think. Mine's a hi-fi and with a pink noise source the woofers run fairly flat to 40Hz, are down 10dB at 30Hz. That's going through the system, so it includes the response shaping built into the amp. I've never been curious enough to go through the hassle of moving a seat to test one direct for both response and to get the full T/S specs. I would if I was considering a replacement, so I'd know if a replacement was better, but then I'd have to know the specs on potential replacements, which are pretty much impossible to get.

[IK6SPEED]

Originally Posted by Larry77

I just upgraded my Harmon Kardon f30 under-seat sub to a Bavsound Ghost sub and I'm wondering if the Harmon Kardon sub I had is better than my wife's HiFi under-seat sub in her e70 X5? If it is I'll swap them as mine were working fine.

Obviously I'll just take a look if nobody knows but thought I'd ask to see if I can save the trouble. Her HiFi bass was definitely subpar to my H/K bass in sound but I'm not sure if the difference is the amp behind it or the speaker itself?

To begin with, none of the BMW (or BavSound) are actually sub-woofers as they cannot create frequencies that low.

[BEM-S4]

Originally Posted by IK6SPEED

To begin with, none of the BMW (or BavSound) are actually sub-woofers as they cannot create frequencies that low.

I think a lot of folks just call them subs since it's easier and that's what Bavsound and others call them.

For anyone upgrading the amp I HIGHLY recommend taking the extra $15 and 5 mins to prewire RCA and remote wire in case you want to add an in trunk sub someday. You can then install that without ripping your trunk apart again.

Additional upside your local speaker shop may let you demo a powered all in one box from JL or something since you'd just plug it in which would take 30 seconds.

[Larry77]

If I search each vehicle on Bavsound's site they both call for the same Ghost sub as an upgrade. I didn't have any question that the H/K sub would fit in my wife's HiFi X5, I'm just wondering if the stock "subs" are different at all?

I can totally see the ohm difference argument though. So they might be drawing less from her amp right, if her subs were 4ohm putting an 8 ohm sub in there would put out less sound at the same volume. It's been awhile since I've built custom stereos but I remember looking for amps that are stable at lower ohms so that they put out more sound with less watts. Maybe I have it backwards in my head?

By the way the Bavsound Ghost "subs" in my H/K f30 so far are much more accurate and are giving me a TON more of the lower mid frequency that was so lacking. They haven't opened up yet so the lower end is not as good as stock yet, I expect they will be.

[Billfitz]

Originally Posted by Larry77

I remember looking for amps that are stable at lower ohms so that they put out more sound with less watts. Maybe I have it backwards in my head?

Yes, that is backwards. How loud a speaker goes has nothing to do with watts, it has to do with volts. The distance that the cone moves is proportional to the voltage applied and the voice coil impedance. With a lower impedance coil the cone will move further for the same applied voltage, so it will go louder with the same amp. However, when you lower the impedance you increase the current draw. That's where the impedance rating of the amp comes into play. If you run a driver with a lower impedance than the amp is rated for that can overheat the amp, worst case causing it to shut down or even be damaged.

By the way the Bavsound Ghost "subs" in my H/K f30 so far are much more accurate and are giving me a TON more of the lower mid frequency that was so lacking. They haven't opened up yet so the lower end is not as good as stock yet

Those are subjective observations that would not be confirmed with measurements. The woofers don't contribute enough in the lower mids for there to be any difference. On the low end, whatever driver break in that occurs will occur within a maximum of 40 hours use, while the difference that occurs after break in is too slight to be heard in most cases. I suspect you've been influenced by the Bavsound advertising, which is long on claims but short...as in non-existent...on real engineering data to back them up. In my business (I'm an acoustical engineer) we'd say that their marketing department is writing checks that their engineering department can't cash.

[Larry77]

Originally Posted by Billfitz

when you lower the impedance you increase the current draw. That's where the impedance rating of the amp comes into play. If you run a driver with a lower impedance than the amp is rated for that can overheat the amp, worst case causing it to shut down or even be damaged.


Those are subjective observations that would not be confirmed with measurements. The woofers don't contribute enough in the lower mids for there to be any difference. On the low end, whatever driver break in that occurs will occur within a maximum of 40 hours use, while the difference that occurs after break in is too slight to be heard in most cases. I suspect you've been influenced by the Bavsound advertising, which is long on claims but short...as in non-existent...on real engineering data to back them up. In my business (I'm an acoustical engineer) we'd say that their marketing department is writing checks that their engineering department can't cash.

Wow, thanks for the very technical response but it seems what I was trying to say is true (just used wrong terms). If her car had a 4 ohm sub and I put my 8 ohm in it, the amp would not have to work harder as someone mentioned. Wouldn't it actually work less hard and provide less output? Do you know if the subs are different between the H/K system and the HiFi?

While my observations are not measured, I don't think you can argue that I'm hearing frequencies that were not there with the stock subs. I listened to songs that I have listened to dozens of times in my car using the same method and I'm hearing parts of the song that weren't there. The deeper bass is tighter but not as loud at the same volume. In my experience over the years I could always here a change in bass when the subs finally started to open up. I am not in the camp that thinks Bavsound speakers are end all be all, but they are a very easy swap and they do improve the sound by making it "richer" and less fatiguing for sure (from my Stage 1 install in my wife's HiFi X5).

[Larry77]

Correction, I just looked closer the Bavsound Ghost Sub for her HiFi X5 is actually 2 ohm, so my stock 7 ohm would likely sound like crap in there. Never mind, answered my own question...

[Billfitz]

Originally Posted by Larry77

If her car had a 4 ohm sub and I put my 8 ohm in it, the amp would not have to work harder as someone mentioned. Wouldn't it actually work less hard and provide less output?

It wouldn't go as loud with the same signal, because the cone wouldn't move as far with the same voltage input. The amp wouldn't be working as hard in terms of the current output, but that's not necessarily a plus, especially if you just turn up the bass EQ to compensate for it. That could lead to higher levels of distortion.

Do you know if the subs are different between the H/K system and the HiFi?

The part numbers are different, but as to how the specs might differ that's anyone's guess.

While my observations are not measured, I don't think you can argue that I'm hearing frequencies that were not there with the stock subs.

You may, you may not. That's one of the benefits to taking measurements, which are at least a full magnitude of order better at identifying what's there than our ears. I've been a sound professional for over 40 years and I still follow Reagan's Rule with respect to what I think I'm hearing: Trust, but verify. No one is immune to sighted expectation. For example, watch this, starting at the 2:45 mark:

[alohasurftoad]

it was me that said the thing about impedance (called it resistance, knew that wasn't the right word) haha. back in the day (in my younger years) i had 2ohm subs driven by 2ohm stable amplifiers. i recalled high impedance speakers needing a lot of power but didn't understand the physics behind it.

never too old to learn something, thx Billfitz

[Billfitz]

FWIW 2 ohm drivers and even the occasional 1 ohm driver used to be fairly common in auto sound. Before the advent of modern power amplifiers with voltage step-up power supplies the voltage swing of amps was limited by the 12v power. With maybe 8 to 10 volts maximum capability even 4 ohm drivers wouldn't go all that loud; as a matter of reference 10 volts into 4 ohms is only 25 watts. That same 10v into 2 ohms is 50 watts, and 100 watts into 1 ohm. The downside was the high current demands all around, on not only the amp, but on the car battery, alternator, and all the associated wiring. As soon as amps with voltage step-up power supplies were available, so that even with the car 12v supply you could still get 30v or more from the amp, the move was made away from very low impedance drivers.

[IK6SPEED]

Originally Posted by Larry77

While my observations are not measured, I don't think you can argue that I'm hearing frequencies that were not there with the stock subs. I listened to songs that I have listened to dozens of times in my car using the same method and I'm hearing parts of the song that weren't there. The deeper bass is tighter but not as loud at the same volume. In my experience over the years I could always here a change in bass when the subs finally started to open up. I am not in the camp that thinks Bavsound speakers are end all be all, but they are a very easy swap and they do improve the sound by making it "richer" and less fatiguing for sure (from my Stage 1 install in my wife's HiFi X5).

You might be hearing things in the higher of octave 2 (64hz) and most likely in 3 (128hz) and 4 (256hz) of human hearing as these speakers are woofers only (and subwoofers in false and deceptive advertising) while the other speakers in the car are midrange and high end tweeters.

But you are not hearing ANYTHING in the lower octave range (32hz) that subwoofers are used to produce bass notes.

You cannot change the laws of physics of what is required to produce the longer wavelength low frequency. If one had the ability to change the laws of physics, one would not need to put 1 subwoofer in trunk as 2 under seats could easily accomplish the sound.

[Larry77]

Interesting video, I'm going to watch the whole thing at some point.

What I can say about the Bavsound stage 1 and Ghost Speaker upgrade so far on my H/K f30, it sounds a lot "richer" and sounds similar to some aftermarket systems I've built in the past as far as tone (probably a dozen over the years). It obviously doesn't have the power or the sound quality of some of my higher end systems, but it definitely does NOT have the tinny fatiguing sound of the stock H/K system. The build quality of the Bavsound speakers are DEFINITELY a step up from the crap H/K speakers. I still am missing a lot of the deep tones and I agree that the ghost speakers are probably not going to open up a lot so I'll probably end up with an "add a sub" upgrade from Misicar NW in the future.

So far, I think the upgrade was well worth it and if I were to blindly sit in a stock H/K system compared to a Bavsound stage 1 with the ghost speaker upgrade I guarantee you I could tell the difference (as the video suggested).

[Billfitz]

Originally Posted by Larry77

if I were to blindly sit in a stock H/K system compared to a Bavsound stage 1 with the ghost speaker upgrade I guarantee you I could tell the difference (as the video suggested).

Watch it again, that's not what it suggested. Here's another take on the same subject. Note who the author works for:
http://seanolive.blogspot.com/2009/0...o-product.html

The only totally subjective testing that's valid, because it removes any possibility of cognitive bias, is double blind, where neither the person taking the test nor the person administering it is aware of what's being tested. As noted in the video a surprising percentage of people will honestly think they hear the difference between two systems even when it's actually not two systems, but in reality the same system.

[Soul_Glo]

Originally Posted by Larry77

Interesting video, I'm going to watch the whole thing at some point.

What I can say about the Bavsound stage 1 and Ghost Speaker upgrade so far on my H/K f30, it sounds a lot "richer" and sounds similar to some aftermarket systems I've built in the past as far as tone (probably a dozen over the years). It obviously doesn't have the power or the sound quality of some of my higher end systems, but it definitely does NOT have the tinny fatiguing sound of the stock H/K system. The build quality of the Bavsound speakers are DEFINITELY a step up from the crap H/K speakers. I still am missing a lot of the deep tones and I agree that the ghost speakers are probably not going to open up a lot so I'll probably end up with an "add a sub" upgrade from Misicar NW in the future.

So far, I think the upgrade was well worth it and if I were to blindly sit in a stock H/K system compared to a Bavsound stage 1 with the ghost speaker upgrade I guarantee you I could tell the difference (as the video suggested).

The bav sound are even better on an amp like fischer or bimmertech

[Larry77]

Originally Posted by Surg_Capt_R

The bav sound are even better on an amp like fischer or bimmertech

Right but that is not a direct replacement option for the H/K stock system.