How much bass is too much bass?

[michael hurd]

I would spend the bulk of your money on adding sound deadening materials to the inside of the cab, this will help tenfold towards getting good sound, no one likes rattles and buzzes. $ 400 spent here will make a world of difference.

You can do most all that work yourself without having to pay a shop... if you can use simple hand tools and remove most of the interior ( the dash can stay ) then you can do it.

Foam tape or a poly tape between plastic pieces can eliminate squeaks from plastic trim panels, which is a problem in these trucks.

Good door speakers can sound quite decent driven off of the factory deck, I would keep the factory rear speakers, this is not money spent well, since I turn them down to the point where they are barely audible.

If you go to a concert, do you turn around and face the back of the auditorium? Of course, you hear some reflected sound in a large venue, but it is delayed in time, as well as having very little high frequency information.

This could be reproduced in a vehicle if you have a processor that is capable of delay and have the rear speakers on an amplifier.

However, diminishing returns are at play here... you are talking a lot more complexity and a lot more cost.

 

[michael hurd]

Power: how much is too much / overkill?

In the pro sound world, 10 db is the accepted 'standard' for headroom, IE: if the requirements for 'X' volume is say 200 watts, they will use an amplifier that is capable of 2000 watts into that load. Of course, their systems are quite locked down with limiters, compressors and so on, along with very careful operation and set up. This keeps the amplifiers almost idling along, with plenty of reserve power for transients, as well as thermal operation headroom.

I would use a minimum of 3 db headroom in an automotive application, this is 2x the power.

 

[michael hurd]

Finally, how much is too much.... this is... especially considering the lack of ear protection. Even with ear protection, they would experience > 110 db at the eardrum through bone conduction, approximately 40 db down from what would enter the ear canal.

http://www.youtube.com/watch?feature=player_embedded&v=CkQ5sU40mLA

 

[michael hurd]

I had a relatively simple SPL set up in my old Accord that I tossed together for one weekend of fun, I ended up taking 2nd place by less than 2 db, and I was on stock electrical with 1kw worth of amplifier.

 

[boy&hisdogs]

In your post, you mention that you don't want to attract thieves. Pretty simple, if you keep the volume reasonable driving around, with the windows UP, use the factory head unit with a line output converter, have the amp and driver out of sight, you should have zero problems.

This does a good job of keeping the CHP away too I would imagine.

To answer your questions... there are many factors at play on how loud a system will play. Efficiency ( not to be confused with sensitivity [ voltage sensitivity ] ) plays a large part in this.

2nd: Bandwidth.

If you want to reproduce sound flat into the single digits, without having excess intermodulation distortion ( where simultaneous frequencies are being played, and the cone excursion from the low frequency modulates the upper frequency up and down in frequency )

This requires large radiating area, and / or reduced bandwidth. Ported ( also known as vented ) enclosures reduce cone motion at the Fb, this can add extra output, however they require a proper high pass filter to keep the driver from destroying itself if out of band signals below the tuning frequency are played.

The ported enclosure is not a trivial concept, and simply plugging woofer 'A' into a generic box yields far from optimum results. There is simulation software available to help in the design, but it's learning curve is relatively steep. I use WinISD to model enclosures, Unibox is another commonly used software package. Both are freeware that run on Windows platforms, you may be able to use them on Linux / Mac through emulation.

Sealed enclosures are relatively simple to construct, and are quite forgiving to errors in volume. Low frequency protection for the driver is good, they require no high pass filter, however they are the least efficient type of enclosure.

The way a ported box works, is the air mass in the port acts like a mass on a spring: it resonates at a certain frequency, tapering off on either side. The width of the port contribution is called the 'q'. Adding foam / fiberglass inside the enclosure can slightly widen the bandwidth of the port. ( where it works effectively )

Changing the diameter and length of the port changes the mass / spring relationship. Changing the enclosure volume ( also taking the port displacement and woofer displacement into consideration ) while keeping the port size the same also changes the tuning frequency.

In small enclosures, it is easy to have a gross error in volume calculation, which will cause errors in the tuning frequency.

Bandpass enclosures: these types of enclosures can be of a few different types, but for the sake of discussion, we will simplify it. In the 4th order bandpass, the woofer is in a sealed enclosure, that fires into another chamber that has a port. ALL output is through the port. They have fairly decent efficiency over a very limited bandwidth, are much more difficult to construct.

Bandpass enclosures have gross errors when it comes to phase response, and these also have large amounts of group delay. [ some frequencies are delayed with respect to others ]


To expand further, if space is a primary concern [ to most people that is the most important aspect ] then a sealed enclosure is your best bet. These are the most power hungry types of enclosures, especially small sealed boxes. Efficiency is rather low, albeit a raw driver with 89/db/w can in a sealed box, with the 'cabin gain' of a vehicle exceed 100 db/w in an vehicle.

With 128 watts on tap, you can exceed 120 db.

For the first time enclosure builder, I would not mess with attempting a ported box, a bandpass or a horn. These are the equivalents of the first time carpenter building a home without knowing how to.

For the best performance, I highly recommend a means of adjusting the phase relationship of the subwoofer to the main door speakers. You can adjust 180 degrees by simply swapping the wires at the output terminals at the amplifier or the enclosure itself. This can get you close, but there are other electronic means to vary the phase by few degrees.

Simply put with correct phase relationship, there will be no 'hole' where the door speakers drop off and the subwoofer starts operation. This also has to do with level, and the upper roll off on the subwoofer.

I had already decided on a sealed box for those very reasons, but that post was absolutely fascinating. (I'm an engineering student). Is there a good writeup or website you could recommend if I wanted to learn more about this?

I know that manufactures give minimum and maximum volumes for enclosures, but is there a way to calculate the optimum based on this or anything else besides just trial and error? I'm really only concerned with sealed of course. What about the shape of the enclosure? Would a cube, thin/flatter rectangle, triangle, or other shape make an audible difference in the end result? Assuming that they are all the same volume.

What about speaker efficiency? Is there a way to calculate bang per watt per dollar just by manufacture specs?

And would you agree with RynoHarris that a down-firing box would be best? I like the idea of the protection it would provide if nothing else.

 

[boy&hisdogs]

I had a relatively simple SPL set up in my old Accord that I tossed together for one weekend of fun, I ended up taking 2nd place by less than 2 db, and I was on stock electrical with 1kw worth of amplifier.

If I were shooting for more "felt" than "heard", then would SPL be my main focus? And how would one go about calculating this?

 

[boy&hisdogs]

So let's say I'm going to go with a single sub, down firing, sealed enclosure. We'll say 10", 4 ohm, DVC for comparison's sake. I whipped up this spreadsheet, most of the info is from Crutchfield.

You must be registered for see images attach

What do you guys think? The kicker, being 2-3 times as powerful as the rest, as well as having nearly the lowest response and middle sensitivity seems like it would make it the winner, but I'll let the experts call this one. Any other good, sub-$200, shallow mount subs I'm forgetting?

 

[michael hurd]

This does a good job of keeping the CHP away too I would imagine.



I had already decided on a sealed box for those very reasons, but that post was absolutely fascinating. (I'm an engineering student). Is there a good writeup or website you could recommend if I wanted to learn more about this?

I know that manufactures give minimum and maximum volumes for enclosures, but is there a way to calculate the optimum based on this or anything else besides just trial and error? I'm really only concerned with sealed of course. What about the shape of the enclosure? Would a cube, thin/flatter rectangle, triangle, or other shape make an audible difference in the end result? Assuming that they are all the same volume.

What about speaker efficiency? Is there a way to calculate bang per watt per dollar just by manufacture specs?

And would you agree with RynoHarris that a down-firing box would be best? I like the idea of the protection it would provide if nothing else.

I am friends with a few engineers in the audio world, particularly in transducer ( speaker ) design. These people are the nuts and bolts people that use FEA (Finite Element Analysis) , FEMM (Finite Element Magnetic Method) as well as build parts on rapid prototyping machines like SLA. ( Stereo Lithography Apparatus )

The audio world is actually quite small.

As far as a website to recommend, there are many... you have to be able to sort through the BS to get to the really good information, and most sites with good information will leave you feeling like you tried to take a sip from a fire hose at full tilt.

As far as calculating the optimum enclosure volume, you need at the minimum a full set of parameters, and a working knowledge of simulation software. This simulation is based on small signal levels, and it does not fully represent the performance of the driver / box combination at high signal levels.

As the voice coil heats up, motor strength falls off, and the driver 'likes' a bit bigger enclosure. The suspension that returns the coil to it's rest position can have asymmetric behavior. ( meaning the restorative force is different on the out stroke vs. the in stroke ) The suspension system can also have poor linearity period. The surround can also have a large effect on the performance, both in terms of temperature and stroke.

Rubber surrounds become very stiff in cold weather, making the compliance less than when at room temperature or above. A foam surround can have less issues with this, but old formulations did not last with exposure to sunlight, ozone and just plain time. Modern day foam surrounds are of a different material, and has much better longevity.

In the frequencies we are talking about, it does not make any difference in the shape of the enclosure to the sound quality. This is more important for midrange frequencies, where the wavelengths are shorter, and you can have baffle diffraction issues.

As far as 'efficiency' goes it is set in stone by Hoffman's Iron Law: http://sites.psu.edu/speakerdesign/2013/01/24/hoffmans-iron-laws-of-speaker-building/

You can pick any 2 out of the 3: there is no free lunch.

As far as figuring out bang for the buck, there is no real way to do that other than measurement. Subjective opinions mean nothing.

A downfiring box is fine, you end up with a bit of free low pass filtering that way, IE: rolls off the top end of the response some, but will not affect low frequencies. HOWEVER, you must make sure that the weight of the diaphragm / coil combination is not enough that it will cause sag over an extended period of time. There are calculators to figure this out.

 

[michael hurd]

If I were shooting for more "felt" than "heard", then would SPL be my main focus? And how would one go about calculating this?

If you want it to be felt more than heard, you want more emphasis on the low frequencies.... this sort of goes against your requirement of not rattling the doors and so on.

If you want impact like being in a club or at a concert, this would be from high sound pressure levels in the 80 hz range, not necessarily 'low end' think 'chest wall vibrating'. The sound systems employed have very high sound pressure levels, but nothing below 35 hz, as that pesky guy Hoffman creeps back into the equation. They are constrained by amplifier power, and truck pack dimensions. Hence, their trade off is bass extension.

Acoustic size also plays a part in how we perceive low frequencies... it basically boils down to having enough radiating area, efficiency and amplifier power. ( the last two are tied together, but that's another subject )

Something like an Aura bass shaker can also give you more tactile sensation, I would not use them alone, but in concert with a decent subwoofer. When the levels are set correctly, they give a totally different sensation.

They are basically like a crude linear actuator.... when bolted to something, and given an appropriate audio signal from an amplifier they vibrate. Unlike a subwoofer, they do not have to displace air, they can be directly coupled to 'you'.

 

[michael hurd]

Not to be nit-picky but most of the real shallow mount subs aren't that great. They have limited output capability both long term and peak output because of the relatively short stroke, motor strength ( both in terms of the magnetic flux density, coil winding volume, type and diameter ) and a lack of thermal mass. The suspension has to have compromises as well. ( packaging )

JL's shallow mount sub has a big voice coil and good motor / suspension design, however it is quite expensive. If you can go with a bit deeper subwoofer driver, your options open up.