bass in loudspeakers....

[Ianm2]

hmmm, this is contentious...

having planned to build my own speakers, more a collaboration, I have been thinking long and hard about bass....

Its said p.a. drivers sound bad...????

compared to hifi ones...

I suppose, again one has to look at the design goals, ie. the particular aspects to focus on.

pa woofers are designed for spl, dispersion, and power handling....

hifi, probably flattish response, less cone breakup, and budget pricing.

now there are a number of factors in power handling...

thermal handling...
distortion...
which is related to excursion 1,

and mechanical limitations, again to do with excursion 2, ie you don't want the moving part to go to far back, otherwise, it will hit the back plate, ditto too far forwards, as the coil may go out of the gap, the suspension

but what about bass?

the p.a. drivers are light, to get the spl, (biggish coils and magnets too), and a result is a higher resonant frequency, as this is related to both moving mass and suspension stiffness. So one may assume they may not give bass, BUT I have been informed by an authority they are truly magnificent, sadly, he limits what he tells me so I have to work it all out myself

There are 4 possible factors in bass reproduction I have identified...

a low frequency...

spl at a particular frequency.

the 'push', ie the force the cone drives the air with, so the lighter the cone, and stronger the voice coil and magnet, the more the instananeous acceleration f=MA newton 2nd law., so A= BIL which is F, divided by mass

This is the B(magnet) I ( current) and L( voice coil inductance equation, from physics, force = BIL.

Finally, I think after some thinking through, the most important, I feel, after wondering why on earth hifi speakers with low frequencies in boxes, ie kls3 as an example, (and atc 9" woofers, in a 50 litre box), going down to around 30 hz flat audax hm210CO in a 60-80 litre enclosure, but still not giving the kind of bass I crave, virtually no hifi speakers have given this requirement.

conclusion, simply bass depth isn't sufficient alone and we may be barking up the wrong tree by simply going for extension of low frequencies....

I am convinced its to do with the volume of air moved, ie think of a cylinder, the longer it is, the wider it is, the more air.

this is the diameter of the cone, and the excursion of the voice coil, so, to get real bass, go for a massive amount of displaced air and drive with limitless current( froma big output stage and power supply).

ie large cones, mega long excursion, at high sound pressure levels.

This is my first attempt at a proper speaker design, so, I want to get it right, has anyone else any insights on what they feel gives gut impacting bass, REAL bass? not a limp floppy boofy sea bass fish ?

one day, I will be adding 2 subwoofers with either 18 or even 24" drivers with colossal excursion.

no one to my knowledge has ever said this on the web, so either they don't know, or don't want you to know, or simply won't do it commercially,as it would damage the price structure so they can charge 700-1000 plus quid for a 8, ten or 12" woofer if you are lucky, that is not very rigouressly built , when you can get 2 stonking 18s for around 60 quid each praps more.

[pre65]

Hi-why not a big,high powered,high quality sub woofer ?

there seem to be many speakers capable of excellent mid and high to go with it.

to be honest i personally dont crave megabass and find my KLS3 and Fostex quite satisfying.


Philip

[andrew ivimey]

What kind of a barn do you want to fill with this bass stuff, Ian?

And I wonder then what real 30Hz (with all the rest above high quality music, would sound like)

But surely, (and I know that's not your name ) if you want to go into this way down deep place, you will need and equally way down huge listening space?

[Ianm2]

hi Philip, that's what the twin 18s will be doing one day.

Originally Posted by andrew ivimey

What kind of a barn do you want to fill with this bass stuff, Ian?

And I wonder then what real 30Hz (with all the rest above high quality music, would sound like)

But surely, (and I know that's not your name )

1/ needen't take too much room.

2/ no idea, never really heard real bass from a speaker b4, heard atc 9 inchers, volt 12 inchers, seas 8 inch metals, its gonna be very good indeed, all parts are important, not just bass

3/ ??????????????????

[slowmotion]

For "real" bass down to 30Hz, 2 pro 15" woofers per side in a proper box should do it. I you want to go deeper use subwoofers below 30Hz.

cheers

[Ianm2]

also cabinet help required from seasoned speaker builders, how does one get a perfect 90 degree angle on 2 pieces of large wood, or any other way to stick the thing together?

there is only, from 2 pieces point of view, 3 ways to stick a big panel, top/bottom to front/back, back to front, and front/back to side.

screws and cabinet pins are being considered, too.

[G.Axiom]

Ian,


My 2 €cents for decent PA-drivers.
Used for a while now a pair of 15 inch RCFL15P530:s, and I am very happy with them. Some braggin now, but in the present dipole configuration they generate most believebale, fastest, slammiest, most accurate and tuneful low extension-which honestly colud be some more extended- I ever heard. First time only now it is on par with what Axiom 80's can do.
I think that this mostly has somethin to do not only the dipole configuration, but also that very short linear excursion, not long. What longer linear excursion, that slower transient response and --oscillations after the trasient--, please forgive me my vocabulary

Havn't ever tried any domesticated drivers, but somehow I suspect that could be just waste of time, "peerless-range". At least, it is very hard to find any home audio woofers with good (100dB) sensitivity, at any price point. Perhaps AER or Supravox......
Just remember: not all PA-drivers sound good, just like not all old TT:s and tone arms sound good...
If you feel like let down with that PA-driver there is advantage of very reasonable second hand value of PA-gear. Any pro audio guy feel drivers bought from someones living room just like unused.

I've been thinkin about two RCF:s per channel, in series for higher impedance... just 4 15-inchers with 100dB sensisivity, thats a minimal requirement to play some music in your livig room
( I some miss that sensitivity they lost when moved from closed boxes to baffles)

Ahh, Brazilians has this very nice hit drum called "surdo", that is that --mmmmmph-----mmmmph--- you usually hear below samba orchestra. There might be four guys playin such instrument, two players on each side and other guys silencing the drums membrance. They could have very hard or very soft drum sticks, it can be slapped with hand or fist, its very nice and versatile instrument.
It just hurts most audio systems a little. Specially when several suchs on same band, doubled with kick drums and bass guitars...

Edit:
"the p.a. drivers are light, to get the spl, (biggish coils and magnets too), and a result is a higher resonant frequency, as this is related to both moving mass and suspension stiffness. So one may assume they may not give bass, BUT I have been informed by an authority they are truly magnificent,"
I generally agree with your authority. Low resonant freqvency usually means rubber surround, and bad sensitivity and transient response.

[Rupert]

Ah yes, real bass, I can understand your need Ian! In the early eighties I used to run a fairly large PA with some friends. I think my more recent interest in Hifi and my expectations of it have always suffered a little from this. There is nothing quite like standing in front of a PA stack with a dozen or so thousand watts of amplification behind it, not hifi but the sheer power and visceral thrill and of course the bass, I can assure you PAs produce bass. Funnily enough I have struggled to achieved this experience with my domestic hifi in my living room!!!

Yes you are right of course Andrew, PAs have an advantage, being used in large venues, there are limits to what you can achieve in a small space, because of the relatively small volume of air and restricted fundamental modes etc. etc. A PA stack does not sound the same in your living room, I know, tried it, and before you ask, no the neighbours were not impressed. It was spectacularly loud though. The drive units in a stack of PA speakers also have the advantage of coupling together, the area of their cones effectively combined and there ability to produce bass increased. Things have no doubt moved on but we always favoured JBL and Gauss drive units, they were always a significant cut above the rest (do Gauss still exist?). We never used drivers over 18".

I don't think think achieving the lowest freq possible is where the best bass experience lies unless you are into organ music or some synth stuff. Most instruments, including bass guitars and kick drums don't go anything like as low as 30hz or even 50hz.

Anyway I'm just getting nostalgic and not really helping the cause of living room mega bass and will shut up, but good luck.

Rupert

[Darren D]

Umm, yes Ian, real bass = good

I use 12" drivers in my "normal" speakers and a single 15" sub 45Hz and below with a summed signal via a SS amp.

I don't know if it's real bass? But I wouldn't want to live without it.

Have a hankering to try an 18" speaker and also believe size and short throw to be one of the keys.

[G.Axiom]

Originally Posted by Rupert

...

Anyway I'm just getting nostalgic and not really helping the cause of living room mega bass and will shut up, but good luck.

Rupert

Rupert, If I understud correctly Ian was asking whether it could be possible to build a system with PA-drivers and good low exstension, not PA-drivers and PA-sound.
My experience is that it is possible. I got very good results with my experiments, and let me assure you, I wouldnt be writing this if the sound produced hadnt some very special properties, and being compeletely dissimilar to any PA-system.