How I improved the B&O sound quality for free

[39Mustang]

I'm surprised. Usually Sony knows what they are doing, including vehicles.

What's bad about it?

I had the Sony in my 14 Raptor and it sounded tinny and no matter how much you adjusted it the sound was flat. When I ordered my 18 F350 the B&O System wasn't an early option and one reason for the new system is Ford got many complaints from truck owners with $80k trucks with a poor sounding system.

I just want to know exactly what do I need to change this setup

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[GTP]

Thanks GTP. Great deep dive into the car’s audio system.
Knowing what you know now would you just pad the signal to the sub and call it a day?

I already did that. Spend quite a bit of time on it.

Here is the classic series/parallel resistor pad circuit, and the resulting changes to voltage transfer and impedance.

Essentially this is a uniform -12dB drop in the subwoofer output. The impedance looks like a near-perfect 6ohm resistor to each amp channel (i.e. single voice coil). I recommend 25W resistors. <RsRp-pad>

 

[GTP]

Here is my preferred circuit. The parallel resistor is replaced with an inductor. You can see that the voltage transfer function rises with increasing frequency. This is because there is a loss in the ~125-250Hz octave, so I did not want to attenuate that region. Technically I would have to verify the acoustic phase behavior of this circuit with the rest of the system.

<RsLp-pad>

 

[GTP]

Some further comments on my two previous posts:

It would probably be best to build the circuit to insert between the trunk cable harness and the subwoofer enclosure, and fasten it down in that location. No need to crack (literally, lol) open the subwoofer box.

It is not "best practice" to insert any series resistor with the bass driver in a speaker system. It effectively reduces electrical damping from the amp. However, increased impedance makes the speaker "easier" to drive and so that is a good thing.

Ideally, 12-15dB of attenuation would be implemented between the HU and amplifier. I am not even sure that that is still an analog signal. I think the dual-resistor Lpad is the easiest implementation. But still not as easy as the "extreme" tone control settings that I arrived at. I don't intend to implement either of these two circuits in my car. (Again, I am still Forscan ignorant at this time.)

Furthermore, I don't see the need to buy/build up a brute-force approach such as with heavy duty 12# woofer with 2.5" voice coil in a bigger dedicated box and possibly ported. Why? Because I am attenuating the subwoofer to 1/4 its original loudness with the wimpy 1" VC Ford woofer, so why should I develop something even more powerful?

Further, furthermore, I think we should all acknowledge the shortcomings of car audio, beginning with ROAD NOISE, and CABIN ACOUSTICS. They are true and worthy enemies of good sound! Would you like your high-end home system if I came over and pumped in some recorded road noise from my car? Or put up hard reflective surfaces close to the speakers and to yourself? Or reposition your right channel speaker to be twice as far from you as the left? Of course not!

This is why I hold rationally lowered expectations for car audio. I am really just trying to make the Mustang sound less bad. </rant>

 

[39Mustang]

Umm lol way beyond my brain at the moment so all I need to know to switch to B&O is it just speakers and sub or other

 

[GTP]

I realize that I am posting at a pretty high level, and I don't expect everyone to understand everything. However, I DO hope that readers will see that loudspeaker (re)design involves much more than first meets the eye.

I went into deep "lab test" mode just to see what I had to work with, to see where the deficiencies were, and to then see what could be done easy and cheap.

As for converting to a B&O system, there are other threads that are covering that very subject.
I have my own ideas for converting the 9-speaker car to one with subwoofer, and for a reasonable cost.

 

[GTP]

Is there a simple speaker swap that could be made to any of these speakers that would make a day and night difference in sound quality with more clarity and sound value/loudness?

@GT5.0Fan thank you for asking this question. I have been expecting it.

The cheapest speaker driver in my home system is a $300 tweeter. So I am not afraid to spend on high-end drive units ... provided the whole system is accurately tuned, in a decent symmetrical room, and with other good associated gear, yada yada.

But why should I spend money and time swapping out the "cheap" speakers in my car given all the enemies I posted about in #34 above?

The B&O system just needs two things: 1) turn down the sub a lot, and 2) turn off the center channel.
The 9-speaker car needs those two things, plus fading almost all the sound to the front, plus adding a sub.

IMEO, none of our cars needs to have the door/A-pillar speaker units replaced. It is just SO much work, time, and expense for a little improvement when there are those 3 enemies I mentioned in post #34.

 

[Cathul]

Is there a simple speaker swap that could be made to any of these speakers that would make a day and night difference in sound quality with more clarity and sound value/loudness?

What you want means you definitely need a DSP for setting appropriate crossovers, time alignment and (most important) equalizing each speaker individually. Further this means a new amp after the DSP and a subwoofer to prevent the midbass speakers to distort heavily from trying to play deep bass.
A DSP and an amp can even make the stock speakers sound really, really good, but again, a DSP, an amp and a Subwoofer are the minimum things needed to really tune in the system.

 

[GTP]

I agree with @Cathul. But another critical missing ingredient for that solution is knowledge and experience, or the research to gain it. There are SO many parameters and means to control them that it is not quick or easy for a beginner to achieve a known-valid solution to a proper alignment. Furthermore one absolutely needs acoustic measurement capability so that one is not "flying blind" during the development process. Again, there is the challenge of getting test signals into the car from the acoustic measurement system.

 

[StangTime]

Again, there is the challenge of getting test signals into the car from the acoustic measurement system.

I use these. https://www.audiocheck.net/testtones_highdefinitionaudio.php
Just download and copy to USB memory stick and play in the car.

 

[CS19]

I corrected my earlier post to say that I had the 9-speaker system in my 2016 Mustang, not 12-speakers. It is true that the 9-speaker car is lacking bass, and there is not a zero-cost solution for that.



I will investigate the Surround mode a little more soon. I can hear a different spatial thing going on. I will put my mic right over the center speaker and verify if it gets turned off in this mode. I can return to this post with that info.

Yes, the surround sound gives excellent 2 channel instrument imaging/positioning. Now my 1960's psychedelic rock sounds awesome! LOL. I did notice that it's necessary to have the volume up to around 12 to get the upper frequency range to sound "right". By all means let us know how the Surround setting worked out for you!

 

[Clump]

Have not been doing much driving with the corona lock down, but today I spent an hour+ in my B&O Ranger. Keeping GTP's settings I switched between stereo and surround mode during quite a few different songs. I played a few from Sirius, but mostly 256KB MP3s from a flash drive.

It seems that surround mode reduces the center speaker output, or perhaps it narrows the frequencies sent to it. To me surround mode sounds better and removes some harshness. It may be a similar effect to removing the center speaker.

These settings definitely need some more volume than my old settings. Really enjoying the sound now. The improvement is really remarkable.

Thanks GTP for all the work that went into this!

 

[CS19]

This could be a function of "cold" weather but I'm noticing a problem with the B+O radio. Whenever I turn the volume or channel selector, it used to immediately change either volume or channel with one click. Now, it sometimes takes 2 clicks before a change and when it does that, the sound completely stops, momentarily, and comes back on. This happens no matter the CD or radio. Anyone else have this happen?

 

[Clump]

Spent some quality time in the Mustang, finally. Love these settings! I don't notice any real difference with the balance centered, or moved to the passenger side, so leaving it centered.

Surround definitely has an effect on the center speaker. There's a harshness in Stereo mode that goes away in Surround.

I noticed that at the same volume setting the Mustang B&O system is quite a bit louder than the Ranger B&O system.

 

[GTP]

I filled the sub enclosure with about 8 oz of fiber-fil.

TLDR: The purpose of stuffing the sub box is to slightly reduce distorted midrange sounds.

Myths about fiber-fil:

1. Yes, it affects the bass response, but negligibly so. It does not really "dampen" the response much.
2. Poly batting sheets against speaker cabinet walls is not effective at virtually all frequencies. Cheap imported speakers with 1/2" thick particle board walls have this stapled to the insides, but it is probably just to check off a line item on someone's QC list.
3. Poly-fil really only helps in the interior, middle, areas on the enclosure and not at the walls. This is because the air velocity is highest in the middle, and zero at the walls.
4. Poly-fil that completely fills the interior of a box is effective to dampen traveling waves. Traveling waves do not develop until the frequency is above that for which 2 parallel walls compose a full wavelength. For example, 13" inside width has a full wave at about 1000Hz, and traveling waves only begin to develop above that. IOW, the poly-fil is not effective for a small subwoofer that operates below 100Hz. However, it is cheap, and it doesn't hurt for those quieter frequencies at and above the crossover point. You can test this by putting your ear right up to a port in a home speaker (floor standing speaker is best choice for this experiment), and play music at low volume. You can hear some really nasty sounds from inside the box! This is the reason why better sounding speakers always have the port located on the rear panel.
5. By all means, fill the inside of your home ported floor speakers. Just be sure to keep it clear from the port opening, because air velocities are quite high in that area. This is what I do for my designs.

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