That's what I was getting at... Guessing around 2kw of power and a single driver cab. Just not sure what is available.
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fundamental frequncy cabinet design
- Thread starter Cirk
- Start date
How loud do you think you're going to get at 25hz while being able to fit it in a van? The answer is "not very".
40" x 40" x 18" and 150 Pounds (including amp). Not impossibly big when compared to an 810, for instance. Peak output 133 dB 32-110 Hz, still over 120 dB at 28Hz. Pretty much what I estimated earlier in the thread.
A regular JBL "off the shelf" mid size touring sub, the 2x15" VT4882DP-DA (thats a mouthful...):
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A regular JBL "off the shelf" mid size touring sub, the 2x15" VT4882DP-DA (thats a mouthful...):
[Invalid or Expired Link Removed]
I should've used the word "impractical" instead of "fantasy". The wide, wide world of car audio is full of snake oil. One could install a second alternator just for the amp, at which point it may be more practical, or less costly, to go to the truckstop, buy a power inverter and use a regular amp.
Even with duty cycle, and the efficiency of a smps power supply, you really think you could hit 18,000 watts of amplification from a 120 volt supply and a 20 amp breaker? That's 2400 watts continuously. 1/8 duty cycle isn't quite enough for very low frequency, should be more like 1/3. And what speakers are going to absorb these 18,000 watts that could be moved in any sort of normal automobile?
Not trying to argue really, just some of this stuff seems a bit of a stretch to me. Fun discussion though.
That TC 5400 looks interesting. Gets down to 15hz with a Vas of 8.5 cunic feet. Would I be correct in guessing that means I need an 8.5 cubic foot sealed box?
No, the Vas only relates the stiffness of the suspension in equivalent volume of air. The higher the number, the stiffer it is. Box size is a result of multiple parameters - plus your design goals in terms of response.
According to their website, anywhere from 2 - 8.5 cubic feet depending on what your goals are. The larger ported boxes will go the loudest at the ultra-low frequencies.
There are a number of speaker box design applications (free downloads), as well as multiple interactive websites that you can punch in the specifications of the speaker and see the performance tradeoffs as you change box size, and go between different alignments. It's the best way to achieve your goals, because you can see the direct effects in terms of volume and low frequency extension. Highly recommended!
Thanks for the volume info. I'll see about working with winisd this weeknd. Had a cigar today with Robin from F/A Amps today, working with him on a couple custom preamp pedals for my 12 string Waterstone. He wants to see how this will turn out.
The Vas is a measure of suspension stiffness as was said. I think technically it equates to how much volume of air would be needed, that when compressed down to 1 cubic meter, would supply the same resistive force to movement as the speakers suspension does.
Anyway, higher number means stiffer suspension. Stiffer suspension means greater control over the cone movement, but also factors in to how much power, and motor strength, is needed to move the cone at X times per second ( hertz/frequency/cycles ).
Think of a home stereo sub with soft foam surround and/or spider. Doesn't take much juice to make it jump. Such is good for recorded music which, aside from a few varieties, like classical music, is generally pretty compressed and doesn't have very high transient peaks in it. Pretty low peak to average signal ratio.
Now think of live bass playing. Very dynamic. High transient peaks, sometimes even up to 10x the average signal ratio. Stiff suspension/more control over cone movement is a benefit here. Takes a good deal more power to move it, but has more control over that movement at high power/pressure levels. That, in combination with motor strength and moving mass (how heavy the moving apparatus is), as well as the stiffness of the cone all work together to make the speaker what it is. Change one and you affect all the others.
Compromises, compromises, compromises..........and cool stuff happening.
Anyway, higher number means stiffer suspension. Stiffer suspension means greater control over the cone movement, but also factors in to how much power, and motor strength, is needed to move the cone at X times per second ( hertz/frequency/cycles ).
Think of a home stereo sub with soft foam surround and/or spider. Doesn't take much juice to make it jump. Such is good for recorded music which, aside from a few varieties, like classical music, is generally pretty compressed and doesn't have very high transient peaks in it. Pretty low peak to average signal ratio.
Now think of live bass playing. Very dynamic. High transient peaks, sometimes even up to 10x the average signal ratio. Stiff suspension/more control over cone movement is a benefit here. Takes a good deal more power to move it, but has more control over that movement at high power/pressure levels. That, in combination with motor strength and moving mass (how heavy the moving apparatus is), as well as the stiffness of the cone all work together to make the speaker what it is. Change one and you affect all the others.
Compromises, compromises, compromises..........and cool stuff happening.
Compared to an 810, that's about the size of....... two 810s.
The opening post specified "light and small enough for reasonable transport".
I think you may have an entirely different idea of what "reasonable transport" is.......
I'd love to have a few of those JBL's from that link at my disposal. I'd get some synth pedals, among other things, and proceed to establish some way to make my bass generate tones that would be almost too heavy for EDM 
Hi.
As do I.
Pretty light and pretty compact if You compare them with anything in their price range.
Will fit easily in anything that is usually used in transporting pro-PA no less.
As for the Ampeg 810 comparison, I'd assume (didn't do the math) it would take at least 5 of 'em to equal the performance of that JBL on their overlapping requency range.
Probably 20 on the frequency range the JBL is intended to.
So, light and compact even by that comparison.
If one would be ignorant enough to compare a purpose designed pro audio sub to a virtually non-designed MI cab that is
.
Regards
Sam
As do I.
Pretty light and pretty compact if You compare them with anything in their price range.
Will fit easily in anything that is usually used in transporting pro-PA no less.
As for the Ampeg 810 comparison, I'd assume (didn't do the math) it would take at least 5 of 'em to equal the performance of that JBL on their overlapping requency range.
Probably 20 on the frequency range the JBL is intended to.
So, light and compact even by that comparison.
If one would be ignorant enough to compare a purpose designed pro audio sub to a virtually non-designed MI cab that is
.Regards
Sam
Please note - in the opening post of this thread, Cirk is looking for a cabinet in the size and weight range of a typical bass guitar backline cabinet that will do ~25Hz continuosly at gig levels. "Gig level" is rather subjective, but I generally take that to mean 125-130db at 1 meter.
There is no such speaker cabinet. Given current speaker technology, it is not possible.
Are there any speaker cabinets, of any size and weight that will do this? Sure.
And while that JBL sub that's referred to is very nice, even at the size of two 810s (and most of the weight) it actually falls pretty short of the performance specified in the opening post - it's rolling off pretty hard in the 25hz range, down 10db@28Hz. Read the spec sheet. Do the math. That's 123db peak output at 28Hz, 120db continous. About half the volume level the OP specified, and more than double the size and weight desired.
Care to try again?
There is no such speaker cabinet.
If you could build a subwoofer that was the size of an 810, weighed less than 100 pounds, and would do 25hz@130db continuously, the pro sound industry would beat a path to your door and you'd be a very wealthy person.
If you're throwing the size and weight limitations out the door, then sure, there are lots of subs out there that will do this job.
...and you'd be wrong. An Ampeg 810 is very efficient in it's normal frequency range. Varies a little by model, but usually in the range of 105-107db@1m.
The JBL referenced is about 96db@1m, even up into the range that the Ampeg covers, so you'd need about 8 of those JBL subs to get as loud as an Ampeg 810.
That's about right.
If we're disregarding size and weight limitations, I'd go for [Invalid or Expired Link Removed]
or this......
Tom Danley's stuff is about as good as it gets.
Those current requirements are a little misleading.
6 amps at 120 volts is 720 watts. Period.
So JBL is actually assuming an RMS signal, not a continuous signal, without saying so.
6 amps per system is a good "real world" estimate, but there is no way to generate 1700 watts of power continuously from 6 amp@120volts.
And that system is still far short of what was specified in the opening post.
That last octave below open E (41hz) is very hard to cover. It can be done, but it's big, and heavy, and expensive. And basically just not feasible on a typical backline.
Is there any possibility running 1700W Continuous out of the system? Unless the signal is a pure sine wave I'd doubt it is possible. But even a sine wave has to be adjusted/gained very carefully up to the rated level of 1700W Continuous (because it may not as easy as it looks like).
Any different steady signal which contains of higher crest then a sine wave (for example a sawtooth) would knock down the Continous rating down to significant smaller ratings. Hence there are lots of dynamics in Audio programs as well, the actual yield of watts is far more less then any sine Continuous rating may prevent to expect.
Even if the system would be fed with a sine wave at the lows, to be save all along the line demands for some Headroom, at least of 3dB.
AC Current Requirement: 6A per system at 120V, 3A per system at 240V
Which calculates to 720 Watt average (RMS), IMO that is a very lot of because the ability of 3400W Peak provides sufficient Headroom for dynamic and transients. Short term transients/peaks are very typical to all kinds of Audio programs and speech.
That's right but it depends. It depends on what shall be considered in particular. It is possible to consider the sufficient headroom for a given Audio Program which may expressed as Peak Power capability, or by the other hand the long term average power consumption which may be expressed as RMS
That also depends because the term RMS very often may be used for anything.
RMS may be used to specify the output power of an amplifier as well as to specify the power handling of a cab. However the signal to which the term RMS refers to in particular are very different animals.
That's right but, although it not possible with 6A it would not be possible even with 12A, because a real world Audio program is not comparable to a sine wave, however both signals may be expressed by the term RMS.
RMS don't tells anything about crest. IMO that is the main reason causing lots of confusions all around audio reinforcement.
That's absolutely right, no doubt about it.
I tried to provide some information that regards to current consuption. Based on PWM (Class-D) topology it is these days not unusual to specify a current/power consumption at the line socket that calculates to appro 1/4 of the rated output power headroom-capability. Gallien Krueger and PowerSoft and Hoellstern come into my mind in this context.
