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Discussion Starter · #1 ·
Larz617 asked what is a perfect box and how do you go about designing one.. but the thread was hidden and I thought that it might of general interest to others. All comments appreciated..EF.

There is no such thing as a perfect box, because the laws of physics will not allow your ears to be the same as mine or the next person, so I might think I have got it right, but you might think differently.

The volume and dimensions of EVERY box is determined by the speaker parameters and NOTHING else, so in the absence of knowing which speakers you are referring to there is no answer.

A couple of years ago I was well into Bandpass Boxes, they served me well as they are one of the most unforgiving boxes to design especially when using multiple speakers.

I then hit on the idea of "Why can I not have a box that offers all of the best of each of the three main designs and none of the drawbacks".. The box in my car nicknamed the AMG dB1218 was the result.

If you look at the page www.efmax.co.uk/db1218.htm this will give you a clue to what went into it.

Basically it is a designed whereby the box is modelled as a complex Bandpass box which assumes a known air space in your car's trunk/boot. It is then designed in such a way as to make the multiple speakers belief that they are in a sealed box, thus they behave in a very tight punchy and accurate way. Because the box is ported it has all the loudness of such a box and is quite efficient. Because it is modelled as a Bandpass box is goes low.

In the real world I call this type of design a Triple Chamber Dual Reflex Box. It uses either two or three identical speakers. It also has a cousin called a Five Chamber Triple Reflex Box, this uses either three or four identical speakers and it also has a Two Chamber Dual Reflex Sealed or Ported mate.

In ALL the above cases these boxes kick some serious arse.

Recently I did a design for a guy using two 15"JL Audio speakers. I designed the box for SQ yet it still hit 146.6dB at this guy's first competition.

I then did a design for the same guy using the same speakers and this time with SPL in mind, it is estimated that he will hit about 151-153dB with this new design and slightly more power,, this is what he said to me when he fired it up..>>SNIP- Erskine,
I got the box going and at first it was very loud, but now it doesn't seem to be making any noise, the woofers are moving ok...just no noise..also is it a bad sign when blood comes out of your ears. On a more serious note, the box kicks some serious a$$. With the old box my vision blurred while driving, but now I can feel my lungs vibrating as well. I can get a bottle of coke to do bunny hops on my roof and I've developed a few new rattles. All this on only one amp.

What really suprised me was how good the bass sounded when I put on Darude- Sandstorm.

Thanks Again and I look forward to getting you started on the mini box design.

Cheers,
Mark Duffy [[email protected]] <<END SNIP>>

Without a doubt in my mind these designs are the very best that I have come across so far in my history as a Bass Box Designer.

With my box, when you take an in-car RTA reading, this is what you get, 0.00dB @ 28Hz, that is LOW.
139dB @ 300wrms @ 50Hz, that is LOUD
+ 0r - 0.5dB frequency change between 47Hz - 105hz, that is FLAT.
151dB @ 65Hz @ 1650wrms @ 1ohm, that is PRESSURE.

So to me this is the ultimate box design but no doubt there will be those who disagree.

I once had the UK Infinity rep sit in my living room and listen to my home set-up which is a scaled down version of my car audio set-up.. Same brand of speakers just smaller.. In his words "They are like class, I have never listen to a set of speakers so clear and so transparent and with so much accurate and seriously deep bass." I had played him Money from Dark Side of the Moon by Pink Floyd.. He wasn't just impressed he was in shock and declared that he had always thought that their more expensive reference speakers which cost then, something like £7K.UK were the best.

Todate there has been nobody from any of the High End Audio Shops in my area who has listen to these speakers who have disagreed.. But are they the perfect design.. Subjective questions get objective answers..

As for boomy lows... No thank you, I want deep accurate precise hard kicking gut rumbling bass that follows the recorded information to the letter.

As for speaker placement, it is considered that speakers that face a panel beit the side wheel arches or the tailgate itself, will suffer the least from in-car cancellation. This is where the speaker is so far away from a reflective surface that the build up of sound in such a small space cause the sound waves to interfere with each other and thus reduce the overall output from that speaker box, a bit like having two speakers with one wired out of phase. By placing the speaker close to a panel it suffers less from such behaviour.
 

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the 1218 box has some amazing design principles incorperated into it, and am glad to see that someone wants the same bass that i want, with that said, efmx, do you know if it will sound as good with 2 tens and 1 twelve, and if so how would i go about getting a design, or scaling down the perameters so it would sound as good, i would like it to go in a first gen 6, and would love to build one, any help would be greatly appreciated})
 

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Discussion Starter · #3 ·
Getting the dB1218 to work, meant finding two sets of drivers that would produce a behavioural pattern whereby the 18 was almost identical to the two 12's.. That was really, really hard and I have never been able to duplicate again with another set of available drivers.

But all is not lost as the design principles works very well using either two identical or three identical drivers, so three 10's or 12's can cause some real damage.

The design principle is basically " I want SQ and yes I also want SPL" and in this respect it does the job very well.

Once a set of drivers have been chosen then it takes me about 3-4 hours to sit down and get the design sorted for each customer, but to date we have had some seriously impressive results of which I mentioned one guy, Mark Duffy from Northern Ireland and he has kicked some arse with his system and he hasn't even got his main project off the ground yet.
 
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