here is some info on box building I have found while web surfing
"CAR BASS BOXES.
sound off info.
It is amazing what you can do with six inch speakers, especially when space is tight or you are working to a budget or just don't want to give up your boot.
Each of these three designs will sit at the back of your car without any fuss.
They will produce a full, warm and amazing bass note.
The theme can be varied, so to can the size but the results are always good.
From:- H9" x L24" x W9" @ 75wrms - from £195.00
A SIMPLE BAND PASS BOX AS REVIEWED BY MAX POWER, JULY 97.
Quasi-Horn Loaded 6th Order Bandpass Box 1 x 6" 100wrms. Port from rear chamber to centre chamber tuned for bass extension. Ports from centre chamber to top chamber tuned for power handling. Ports from top chamber tuned for upper bass and SPL properties.
The basic fact is this. Most bass boxes makers make crap boxes. They try and seduce you with fancy graphics on boxes that haven't got a hope in hell of working because they are designed wrong. They forget that what you really want is box that sounds good and drops serious bass. I've heard people say you can't have loud bass, and accurate bass, and low bass. Wrong!
A lot of people will often run to a sealed box, they seem convinced that this is a safe bet, often it is, but more often it is usually the fact, that the maker wasn't prepared to do their job properly and earn their money, they just want a quick return on their capital. The day any major company starts to employ people like me, then that is the day I go out of business. Hands up to marketing hype, for as long as there is bollocks and [censored], AMG will be around to mop up the [censored] and at least offer people another perspective on audio life.
If you want you can have an AMG bass box, that will literally blow your breath and your mates away. I can and have proved it.
AMG bass boxes have already proved themselves. MAX POWER July 97, a very popular British Car Magazine, with a typical readership of about 1.5 million people, have had the pleasure of testing one of our boxes.
Just check the facts from Adam Raynor, MAX POWER, a man who is up front and bull [censored] free. If it stinks he'll tell you, but if he says it's good you better believe him.
We didn't send them a box with a 10" or 12" or even a 15" speaker, even though we knew this was what they would have preferred. We didn't even make the box especially for the review, no I went and asked a previous customer if I could borrow the box out of her car whilst she wasn't using it, so we sent them a bass box with a 6", yes a six inch speaker. This was a bit like being told that there is a race between two Porsches and you asking if you can put your old banger in. And then beating them.
With the exception of the box being a little untidy due to other people getting their hands on it during it's six months of use, a factor that has been noted and corrected, its overall performance was unmistakable. 90/100 for sound quality. 90/100 for bass reproduction. 75/100 for power handling,...this is just a box with a Eminence 289 6in speaker in it...!
A box the reporter says that can be used for sound off's and still impress your mates with and that it was just a 6" begs one to ask what AMG could do with bigger speakers.
And I quote " The box arrived with loads of info and the results back it up. Erskine Fenty bass boxes kick arse and drop bass".
Well if you would like to find out more just keep reading or just contact us.
The following review was done using 2 HiFonics - Son Of Colossus Bass Amp. These amps are serious, even more serious than my Kenwood 1023 Custom Amp. All this on a test rig that was purposely built to get to the truth behind all that marketing hype that goes on out there.
Check the speck, see for yourself, what is truth? What is bollocks?
Our car bass boxes are design around two simple principles. Point of reference or SPL.
WATCH OUT FOR OUR NEW DOUBLE CHAMBER DUAL REFLEX BOX USING THE NEW PRO CAR AUDIO SPEAKER FROM EMINENCE.
THE LTD RANGE..
Built like a RF Power, runs like a Vega Stroker, sounds better than a JL.
And cost a mere fraction of any of the above.
DOUBLE CHAMBER 6TH ORDER DUAL REFLEX BOX
I am being a little bias here, Eminence Europe did ask me if I would mind doing the exclusive designs for their three new speakers, the LTD 10, LTD 12, LTD 15. Now why do you think Eminence, the worlds biggest supplier of loudspeakers would ask little known company like AMG to do this. Fact is if you ring Emincence UK and asked them anything about loudspeakers enclosures for their speakers, they don't go to their fine technical department, they politely tell you my name and give you my number and ask you to ring me...And with respect I answer all of these calls honestly.
These LTD speakers are designed to work in small boxes and they drop bass like a brick falling from hell. They don't just go low they produce some serious SPL, all this from a speaker using a cast alloy chassis, dual voice coils and twin gold plated binding posts and of course starting with a 10" speaker that can really handle 300wrms. Umm, yes, my kinda speaker ah!
Car Hi Fi have now got one of our boxes with a LTD 10 in it, I will keep this page posted of their forth coming review, personally can't see how I can do any worse than the Max Power review as Bandpass boxes are a lot easier to get wrong....News Flash..sorted...Feb 98 issue..wicked review..
A Sample of Some of AMG Designs.
2 x 6"x9" [sealed box] + 1 x 12" in a bandpass box
2 x 12" in an Isobaric bandpass box.
1 x 18" in a 10" high bandpass box.
SPL PRO Box.
Made from 25mm HDP + sound deadening pads
+ 18mm MDF + "Barrier Mat".
TRI-CHAMBER ISOBARIC 6TH ORDER BANDPASS
This is just one of our many designs, using 10", 12" or 15" speakers.
QUIN-CHAMBER TRIPLE ISOBARIC, COMPOUND LOADED 6TH ORDER BANDPASS SPL BASS BOX.
And this is another one of our many designs, for more info have a look in "News "
AMG design and build box only,
customer's own speakers from £185.00 . .
Box designs from 1 x 8",150w @ £195.00.
to 12 x 15" 6000w @ £6500.00.
Sometimes, because of my love for Bandpass Boxes I get carried away, so for a more objective overview of bass boxes in general, here is an essay from JL Audio.
http://tutorials.jlaudio.comThese essays are the material of JL Audio and herein is an edited version of their tutorials, these essays also include material from the AMG.
The Sealed Enclosure In a sealed enclosure, the woofer is tightly controlled by a trapped volume of air in the enclosure which acts as a spring (hence the name "air-suspension.") The woofer must literally pull the air with it as it moves outward thus decreasing the air pressure inside the box and compress the air inside the box when it moves inward, which increases the air pressure inside the box. Since the air pressure inside the box seeks to equal the barometric pressure of the atmosphere, it acts as a controlling force over the motion of the speaker.
The more the speaker moves inward or outward, the greater the pressure exerted by the air-spring of the sealed enclosure in the opposite direction.
The relationship between the parameters of the speaker being used and the volume of air inside the enclosure dictates the performance of the sealed subwoofer system.
By making the box larger, the air spring limits cone motion less and allows the system to play lower and with flatter overall response (low Qtc) at the expense of power handling.
If you go too large, however, you begin to lose efficiency in order to gain the additional low frequency extension. By making the box smaller, the air spring exerts more control and limits cone motion at low frequencies which increases power handling but does not let the system play as low and produces a more peaked response (higher Qtc.)
For any speaker competently designed for sealed box applications there is a range of enclosure volumes that will produce good high-fidelity sound. Changing the enclosure volume within that range can fine-tune the response to suit the tastes of the listener and/or the acoustic properties of the vehicle.
Ported enclosures. A.N. Thiele and Richard Small are generally credited with having done the most definitive work in this area, which is why enclosure and speaker parameters are commonly referred to as Thiele-Small parameters.
The coupling of a port or duct to the air inside the enclosure allows the subwoofer system to take advantage of the work being done by the rear of the woofer cone to reinforce the low-frequency response.
The resonant characteristics of the column of air in a port, when installed in a given box, are adjusted by altering its resistance to motion, which is accomplished by the dimensions of the port. In some designs, instead of a port, a changing speaker cone with no motor assembly or a flat diaphragm is used to achieve the same effect. This is known as a passive radiator.
In a ported enclosure, there is a delicate relationship between the volume of air in the box, the resonant effect of the port, and the parameters of the speaker being used. When these three factors are correctly integrated, the rear output wave of the speaker is delayed just enough so that when it comes out of the port, it is in relative phase with the wave being produced by the front of the speaker. The result is constructive output from the port limited to a desired low- frequency range.
This low frequency reinforcement is one of the big advantages of a really well designed ported system. Using the work of the rear of the cone in a constructive manner means that a gain in efficiency of about 3dB over a broad band in the sub-bass range can be achieved as compared to a sealed enclosure using the same woofer.
The other big advantage is that the interaction of the port, the enclosure and the speaker's resonant characteristics also reduces cone motion and, therefore, distortion at higher volume levels in the frequency range controlled by the port.
The down side is that at frequencies below the tuning of the port, the speaker gradually begins to act as if it were not enclosed at all (more on this later.)
The increased output combined with reduced distortion in the "meat" of the bass range (30-80Hz) is a big reason why many home speakers and high-power sound reinforcement systems use ported enclosures for low frequency reproduction. The vast majority of recording studios also use ported enclosures as monitors for the same reasons.
The rules governing the behaviour and proper design of ported speaker systems are considerably more complex than those for sealed enclosures. For this reason, it is a good practice to follow the advice of the speaker manufacturer or an experienced enclosure designer when it comes to designing a ported system.
It is very easy to screw up a ported box if you just guess at the size and length of the port or the tuning frequency for the box. Not only will a poorly designed box sound bad, but it can easily damage the speaker if it is played hard.
Bandpass Enclosures....now we are talking bass!!
http://tutorials.jlaudio.comThese essays are the material of JL Audio and herein is an edited version of their tutorials, these essays also include material from AMG.
These enclosures seem to be the latest rage in the car audio world. It would probably surprise many people to know that these designs have been around for many years. The first patent for a bandpass enclosure was filed in 1934 by Andre d'Alton. In the last ten years, interest has been renewed in these enclosure designs and substantial strides have been made in defining their behaviour.
Many home sub/satellite speaker systems currently use bandpass designs for low frequency reproduction. Designs from Bose, KEF, AR, and many others have become very popular in home audio circles.
In a bandpass box design, the woofer no longer plays directly into the listening area. Instead, the entire output of the subwoofer system is produced through the port or ports. In a conventional sealed or ported subwoofer system the low-frequency extension is controlled by the interaction of the speaker and the enclosure design, but the high frequency response is a result of the speaker's natural frequency response capability (unless limited by a crossover.)
In a bandpass enclosure, the front of the speaker fires into a chamber which is tuned by a port. This ported front chamber acts as a low pass filter which acoustically limits the high frequency response of the subwoofer system.
The name "bandpass" is really pretty descriptive in that it refers to the fact that the enclosure will only allow a certain frequency "band" (range) to "pass" into the listening environment.
So what? Couldn't the same thing be accomplished by placing a low pass crossover on the subwoofer system? Yes, it could, but a bandpass enclosure can produce significant performance benefits in terms of efficiency and/or deep bass extension that would not be possible in conventional designs of equal size.
By adjusting the volumes of the front and rear chambers and the tuning of the port or ports, significant performance trade-offs can be created.
When box parameters are adjusted for a narrower bandwidth, the efficiency of the subwoofer system within that bandwidth increases and can reach gains of up to 8dB (sometimes even higher.) As box parameters are adjusted for wider bandwidths, very impressive low-frequency extension can be produced from extremely compact enclosures at the expense of efficiency and good transient response.
Intermediate bandwidths can also be designed which create a modest compromise between all these characteristics. As if that is not confusing enough, within each bandwidth range, the designer can also manipulate box parameters to shift the range of operation up or down the sub-bass range which also has an effect on efficiency.
As you can see, bandpass enclosures can have very different sound characteristics based on the designer's choice of box parameters. As such, it is not always possible to make blanket statements as to the performance benefits and drawbacks of bandpass enclosures in general.
One characteristic of bandpass enclosures which is universal is that they exert greater control over cone motion over a wider frequency band than conventional designs. Due to controlled, rapidly changing air pressure on either side of the woofer, the woofer is capable of producing high levels of acoustic output without physically moving very much. This means that the
woofer is less likely to encounter excursion limits in the main part of the sub-bass range.
However, just because the cone isn't moving as much doesn't mean that the speaker's motor assembly isn't still trying to drive the cone hard; it just means that the speaker cone is encountering resistance to motion.
This resistance can be very hard on speakers, especially when crazy car audiophiles are at the controls. The conflict between the force generated by the motor assembly and the air pressure in the enclosure can impose extreme stress on the glue joints and suspensions of the woofers. You can literally tear a speaker apart in a bandpass enclosure if you apply too much power. Because the speaker is not moving as much and because noises are masked by the front chamber, it is also very difficult to hear when a woofer is in serious trouble.
Many people have been known to crank bandpass enclosures up and blow the speaker to bits within a few minutes because they did not realise that the speaker was having a heart attack.
Choosing the right amount of power and carefully setting amplifier gains is very important in order to ensure long- term reliability. This is true for any bass box.
Bandpass enclosures can be divided into two basic types: single- reflex and dual-reflex. In a single reflex design, the rear chamber is sealed and the front chamber is ported. In a dual-reflex design, both front and rear chambers are ported into the listening area. A variation of the dual reflex and single reflex, known as "series tuned," has a port which connects the rear and front chambers.
The differences between single reflex and dual reflex bandpasses are similar to the differences between sealed and ported enclosures. A single reflex typically exhibits a shallower low frequency roll off rate (approx. 12dB/octave) and better transient response. A dual reflex is more efficient and controls cone-motion over a wider range but typically has a sharper (18-24dB/octave) low frequency roll-off.
Because of the difference in low frequency roll off rates, a dual reflex usually has to be larger in size to produce the same low frequency extension as a single reflex design.
As compared to more conventional enclosure designs, bandpass enclosures are very complex to design and build. Best left to experts who know how to make you happy rather than how to make money.
The rules governing the performance of bandpass enclosures leave no room for error. Slight volume miscalculations or sloppy construction can turn a good design into a poor performing box.
Integrating the proper size port or ports can be extremely challenging and often renders designs that looked great on paper completely impractical. The design of these boxes should definitely be left to people with extensive enclosure building experience.
http://tutorials.jlaudio.comThese essays are the material of JL Audio and herein is an edited version of their tutorials, these essays also include material from AMG
Isobaric Loading.
Isobaric loading has become pretty popular for car audio use in the last few years. Again this is not a new concept, having been originally introduced by Harry Olson in the early 1950's. Technically, "isobaric" is not really an enclosure type; it is a loading method.
This loading method involves the coupling of two woofers to work together as one unit. This is typically accomplished either by placing two woofers face to face or by coupling two woofers with a small chamber. The result of coupling the two speakers is that the coupled pair (iso-group) can now produce the same frequency response in half the box volume as a single speaker of the same type would require.
For example, if a speaker is optimised for performance in a 1 cu.ft. sealed enclosure, one iso-group of the same speakers can achieve the same low frequency extension and overall response characteristics in a 0.5 cu.ft. sealed enclosure.
There is, of course, a penalty involved. Whenever you use isobaric loading, you are sacrificing 3dB of efficiency compared to a single driver in twice the air space. In practical terms, this is not usually a big deal since the power handling is doubled (two speakers instead of one) and the impedance is typically cut in half if we parallel the two speakers (twice the power, assuming the amplifier can deliver the necessary current.) The end result is about the same output as the single driver in the bigger box but at twice the amplifier power (and twice the speaker cost.)
Isobaric loading can be used within any enclosure type, including bandpass designs. The ported and bandpass isobaric designs can be difficult to design and build due to very small enclosures with large port requirements.
Isobaric bandpass designs, in particular, can be literally impossible to build with certain speakers.
There are some things to look out for with each type of isobaric design, such as mechanical noise and uneven heat dissipation which can present potential sound quality and reliability problems. All the methods which involve opposite cone motion require that the speakers be wired in reverse polarity relative to each other. These designs also provide a performance advantage in that their opposed cone motion averages out suspension non linearities (differences in inward and outward suspension control,) which reduces distortion.
If you are strapped for space and can afford the extra speakers and more complex enclosure, the ability to have a compact subwoofer system with no real sacrifice in performance is well worth the extra effort and expense. On the other hand, if you have a lot of space and are looking to get the maximum amount of output without sacrificing sound quality, using multiple iso-groups can give you the best cone area/box volume ratio while still retaining good fidelity.
There are several different isobaric loading configurations to choose from, so which is the right one for you? This is a loaded question that quite often has no clear-cut answer.
At AMG Audio, we do not recommend the use of isobaric loading to just anyone...we do not believe that the more subwoofers that you can shoe-horn into any given volume of air produces the best results. In fact, we're sure you've seen plenty of examples to support this line of thinking.
Piggy-back tunnel loading.
The piggy-back tunnel loaded isobaric configuration is probably the second most popular isobaric arrangement in use today (the first being the face-to-face or "clamshell" configuration. It is cosmetically easier to integrate into the vehicle (as it does not have any potentially ugly subwoofer baskets protruding into the vehicle) but unfortunately this
aesthetic benefit is offset by several important detractors:
1.The coupled air between the two drivers adds to the moving mass of the system and thus results in a less than optimal coupling between the drivers. Remember that the idea is to get these two subwoofers to act as one driver, and by adding a springy mass between them this ideal is somewhat compromised. Some might find that this leads to a beneficial lowering of the system Q, but more often than not this effect is quite undesirable as it makes response predictions more difficult.
2.The coupling chamber negates one of the primary benefits of isoloading small enclosure size. By the time we account for the displacement of this coupling tunnel in determining the gross volume of the blue chamber, the enclosure starts to approach the volume required by a single conventionally mounted driver.
3.Since the drivers are both firing in the same direction, there we do not reap the benefit of cancelled driver non-linearities as we would with a design implementing a push-pull configuration.
4.The driver whose magnet structure is housed in the coupling tunnel is in a highly unfavourable cooling environment and will be subject to power compression at lower levels. Basically, the drivers will be more or less
equal performers at first, but as things start to heat up and the impedance of the front driver rises due to rising voice coil temperatures, the drivers start to fight each other to some degree rather than complement one another. This results in increasingly non-linear behaviour with possible unpleasant audible side effects (e.g. sloppy transient behaviour).
In essence, this configuration is more of a cosmetic design more than anything else, and we recommend that it not be used, especially for high-powered applications where the thermal power handling of the drivers would be called into serious question.
Back-to-back tunnel loading.
This design was thought up by someone who wanted to reap the advantages of cancelling driver non-linearities without having to resort to the "clamshell" loading and it's inherent cosmetic problem (namely that of hiding an exposed subwoofer basket). This design, like its cousin the tunnel loaded isobaric also has several detractions that make it an undesirable choice.
1. It shares the same problems with the added springy mass of air that couples the two drivers but with the back-to-back isoload, this problem is made even worse by the fact that the coupling chamber is now even larger, adding more moving mass and springiness over the tunnel load and thus making frequency response predictions even more difficult.
2. The increased coupling chamber means that the new volume and thus the entire enclosure must be even larger, even more closely approaching the volume of a conventionally loaded single subwoofer. In a home this might not be a problem, but in the vehicle where space is at a premium, this is a definite disadvantage!
3. Now that both magnet structures are in identical cooling environments, they will more closely track each other's performance but unfortunately, now we have two heat dissipating structures in the same tiny enclosure which will greatly reduce the thermal power handling of both drivers, not to mention the fact that as the air heats up, it expands thus pushing each of the subs outward and thus further limiting output by reducing each driver's potential excursion!
While the original creator of this design should be given a pat on the back for creativity, it is definitely not an alignment that we recommend under any circumstances.
"Clamshell" loading.
The face-to-face or "clamshell" configuration as it commonly called is the most compact and therefore the most practical isobaric loading method to use considering the tight confines of the average automobile. This configuration also provides the beneficial side effect of cancelling driver non-linearities.
If there is one recurring theme in engineering it's that Mother Nature is lazy. She has made it a law that anything at rest wants to stay at rest and similarly anything in motion would much rather stay in motion in a straight line. Such is life in general and a speaker's dynamics are no exception. It's called the law of inertia and there is no escape.
When a subwoofer does its job, it is called upon to compress and rarefy the air in the listening environment many times per second and more often than not is required to do so over great distances. This places a great strain on the cone itself as it fights to retain its shape in the face of intense acceleration and deceleration. Ideally, a speaker's cone would be infinitely rigid and wouldn't deform under any circumstances, but obviously a perfect world this is not so we have to deal with the consequences of fighting Mother Nature.
As the cone pushes outward, it is somewhat flattened out as it attempts to kick-start the air in front of it into motion. Likewise, the cone is deformed the other way when the cone returns and attempts to compress the air in the subwoofer enclosure. The extent of this deformation is a function of the cone's geometry, construction and the amount of power with which the subwoofer is driven. A good engineer will design his cones such that this effect is minimised but there is only so much engineers can do if he's to make an affordable product.
For many years now, bandpass enclosures have been quite popular both for their aesthetics and performance. A properly designed, constructed and implemented bandpass enclosure can and often will out-perform the same driver or drivers in a more conventional sealed or ported design in
terms of sheer output and/or low-frequency extension. A bandpass alignment also allows the installer to funnel a potentially large amount of low-frequency energy into the vehicle's cabin through a relatively small opening.
This can be particularly useful in some vehicles such as European sedans whose tank-like construction does not facilitate a satisfactory transfer of low-frequency energy from the trunk into the cabin.
Some companies only use single-reflex bandpass designs (as opposed to dual-reflex or series-tuned bandpass designs). Cubic foot for cubic foot a single reflex-bandpass, characterised by a sealed "rear" chamber(s) and ported "front" chamber(s), typically offer better transient response and low frequency extension than will its more elaborate cousins. In addition, while still a fairly difficult system to construct properly, single-reflex designs are a bit more forgiving of minor errors in calculation and assembly when compared to more sophisticated bandpass types.
All things considered, we have found that single-reflex designs offer the best combination of reasonable enclosure size, good transient response and predictable behaviour for those who want a bandpass box but not the design hassle. At AMG Audio we have perfected, over time, the art of designing 6th Order and Tri-chamber Bandpass Boxes and their equal in isobaric form.
http://tutorials.jlaudio.comThese essays are the material of JL Audio and herein is an edited version of their tutorials, these essays also include material from AMG.
So how do they work?
A bandpass enclosure is, by definition, simply a sealed or vented rear enclosure with an acoustical filter in front of it that serves to limit the upper-end of the driver's frequency response. This natural limiting of the high-frequency response of the system makes the selection of mid-bass drivers critical. If your vehicle cannot fit larger mid bass drivers (such as a 6 1/2" or larger) then a bandpass enclosure is probably not the best choice for you.
Using a bandpass enclosure, especially a 4th Order box, with insufficient mid-bass reinforcement will lead to sluggish, sloppy, muddy, impact-less low frequency response. In short it will sound like a soggy pancake hitting a cardboard box.
Once adequate mid-bass reinforcement has been selected to complement the sub-system it will be necessary to add additional electronic filtering to further limit the upper bass frequencies.
REVIEWS OF AMG PRODUCTS.
This is what other people have said about us.
Music Mart, UK, May 1997, by Gary Cooper.
Max Power, UK, July 1997, by Adam Rayner.
After this review there were still many who refused to believe that a well design box with a six inch speaker could out perform a [censored] box with bigger speakers in it..well you can believe what you want, but the fact speak for themselves. There were some who said it was a fix, that I cheated, well there is no point arguing with people whose perception of life is based on their own tabloid mentality.
Car Hi If, UK, February 1998, by Jack Clayton.
This review highlighted how a well designed ten speaker can perform on both an SQ and SPL level and do it with conviction, just look at some of the other reviews of 10's from the same magazine. Check this out, same magazine, same test equipment, over the last 6 mths. Boston Acoustics RS210B, 2 x 10" [131.0dB] cost £75 more than the AMG Box. Kicker KDCX108, 2 x 10" [130.2dB] cost £85 more than the AMG Box Rockford Fosgate RFB122, 2 x 12" [129.0dB] cost £125 more than the AMG Box MTX T510X3, 3 x 10" [131.0dB] cost £245 more than the AMG Box AMG Bass Box,1 x10" [132.9dB] and a bloody good write up.
FAST CAR, JULY 1998, by ADAM RAYNOR.
I was really looking forward to this review,I had hoped that the testing would be more in depth, but I appreciate that printing space can be tight. A review which covered the lowness of the bass, the hardness of the bass, the SPL output from a 3v input and a max SPL would have been fun.
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