Stacking cabs

[lowhand_mike]

[quote name='bass_ferret' post='221564' date='Jun 18 2008, 05:31 PM']I guess this is probably just to keep the cabs the same width [font="Arial Black"]but it might help reduce comb filtering.[/font][/quote]

i guess thats what raggy, and myself were thinking.
or would it be that because they are close to side by side that they still suffer?

[stevie]

[quote name='lowhand_mike' post='221559' date='Jun 18 2008, 05:20 PM']give it a rest guys.

stevie if you can provide a link to prove your point then please do so as it would be informative reading (i'm a geeking it up tonight )

i'm sure if you could actually prove this information then it would be of great benifit to bill

where as bill info has always been well backed up.

otherwise can it. :ph34r:[/quote]

Here you go ,mike. [url="http://www.htguide.com/forum/showthread.php4?t=29184"]http://www.htguide.com/forum/showthread.php4?t=29184[/url]

Have a look at the post from Kal Rubinson, a well respected audio journalist who writes for Stereophile. He says:

"Yes. 1/2 wavelength is the generally accepted spacing maximum.
Dunno about d'Appolito's standard but ANY two drivers spaced more than 1/2 wavelength apart and reproducing the same signals will show destructive (and constructive) interference in the plane OF their displacement."

There's plenty more if you look for it. I'm bowing out of this discussion now, as it is getting nowhere and I've had enough of the insults.

[MythSte]

Im buying a f'king guitar.

[Merton]

[quote name='ste_m3' post='221579' date='Jun 18 2008, 05:49 PM']Im buying a f'king guitar.

[/quote]
Just make sure you use a 2x12 vertically aligned

[JonnyM]

[quote name='alexclaber' post='221461' date='Jun 18 2008, 03:51 PM']Look how many people spend all that money on an iPod and then proceed to listen to it through the original headphones - if only they knew how much better it could sound! To a large degree it's the same with cabs.

Alex[/quote]

Veering off topic, but that's spot on... I love Grado headphones with my iPod, although they reveal the limitations of compressed audio files...

Rather like excellent bass gear revealing the limitations of my playing, (hopefully forcing me to improve ).

[MythSte]

[quote name='Merton' post='221580' date='Jun 18 2008, 05:51 PM']Just make sure you use a 2x12 vertically aligned [/quote]

Fine, I'll sing!

[warwickhunt]

[quote name='JonnyM' post='221581' date='Jun 18 2008, 05:52 PM']Veering off topic, but that's spot on... I love Grado headphones with my iPod, although they reveal the limitations of compressed audio files...

Rather like excellent bass gear revealing the limitations of my playing, ([b]hopefully forcing me to improve[/b] ).[/quote]

Nah! Use gear that flatters your incompetence... that's what I've done for 28 years

[BB2000]

[quote name='stevie' post='221577' date='Jun 18 2008, 05:42 PM']Here you go ,mike. [url="http://www.htguide.com/forum/showthread.php4?t=29184"]http://www.htguide.com/forum/showthread.php4?t=29184[/url]

Have a look at the post from Kal Rubinson, a well respected audio journalist who writes for Stereophile. He says:

"Yes. 1/2 wavelength is the generally accepted spacing maximum.
Dunno about d'Appolito's standard but ANY two drivers spaced more than 1/2 wavelength apart and reproducing the same signals will show destructive (and constructive) interference in the plane OF their displacement."

There's plenty more if you look for it. I'm bowing out of this discussion now, as it is getting nowhere and I've had enough of the insults.[/quote]

Stevie, you need to read a bit more on the subject to understand the physics, before you get the full picture. So does Mr Rubinson.

[bass_ferret]

[quote name='stevie' post='221577' date='Jun 18 2008, 05:42 PM']Here you go ,mike. [url="http://www.htguide.com/forum/showthread.php4?t=29184"]http://www.htguide.com/forum/showthread.php4?t=29184[/url][/quote]
Crikey! Those guys are even nerdier than Alex and Bill. Still the laws of physics are the same whether we are talking about bass cabs or centre speakers for home cinema and lots of centres have two woofers each side of a tweeter (I knew there was a reason why I bought a centre with one co-axial driver).

Anyway back to this wave length stuff; wave length changes with frequency, the speed of sound is a constant so low frequency notes have a longer wave length than high frequency notes, so if I understand this correctly the wave length being discussed here is related to the crossover frequency? And lobing is the same as comb filtering and that is obviously undesirable in a home cinema system otherwise it screws the sound for those not sitting in the hot seat dead centre.

[JonnyM]

[quote name='warwickhunt' post='221583' date='Jun 18 2008, 06:01 PM']Nah! Use gear that flatters your incompetence... that's what I've done for 28 years [/quote]

[Bill Fitzmaurice]

[quote name='lowhand_mike' post='221575' date='Jun 18 2008, 12:40 PM']i guess thats what raggy, and myself were thinking.
or would it be that because they are close to side by side that they still suffer?[/quote]
Two factors are at work. The closer the driver centers are to vertical the higher the frequency before combing starts, which happens when the driver centers are more than 1 wavelength apart. Fully vertical there can be no combing, but if the driver only goes to, for instance, 3kHz, then a CTC of four inches is sufficient.
The second factor is the total width of the radiating plane, outer cone edge to outer cone edge. As that exceeds one wavelength the horizontal dispersion angle shrinks, eventually to the point of beaming. So even if combing isn't an issue dispersion is, especially considering that four inch wavelength at 3kHz. Even a single ten will be beaming up that high. Now consider a 2x12 or 4x12 guitar cab with driver CTC on the order of 16 inches and a radiating plane on the order of 22 inches wide, and the 4kHz tones they're pushing with only 3.4 inch wavelengths, and one can hardly tell which is worse, the combing or the beaming.

[gypsymoth]

"which is worse, the combing or the beaming"

doesn't much matter, as people seem to like that sound for whatever reason. of course if you are going to stick a mic in front of it, you'll want the PA as technically perfect as possible in order to replicate the agreeable but less than perefect soundsource as accurately as possible.

[bass_ferret]

Now i am really confused - combing and beaming!

To translate this to the real world - when I was using 2x2x10 we often did gigs where the other guys were complaining I was too loud - yet I could hardly hear myself. I can understand this was due to comb filtering or lobing - I was in a trough that made me turn up.

Since I started using the EBS this has hardly ever happened. Now this could be just chance and I was not standing in the troughs, or it could be that the comb filtering was reduced to such an extent that I never had to turn up past too loud. Or it could be the extra clarity of the EBS rig compared to the Peavey rig meant I could hear myself better irrespective of any acoustic features.

[Bill Fitzmaurice]

[quote name='bass_ferret' post='221834' date='Jun 18 2008, 06:55 PM']Now i am really confused - combing and beaming![/quote]
Beaming is when the dispersion angle is so narrow that you can't hear the mids or highs if you move a foot to either side. It's why you can't hear the guitar cab four feet to your left and four feet in back of you, whilst the poor lady at the table in front of the guitar cab fifty feet into the club stuffs her ears full of napkins in a futile attempt at self-defense.
Combing is when the frequency response of the cab constantly changes as you move across the soundfield and literally doesn't sound the same in any two spots.
The other blokes complaining you were too loud while you couldn't hear yourself probably involved both beaming and room modes, where in the spot you were standing reflected waves off the walls and/or ceiling cancelled out much of your low frequency output, while elsewhere in the room that was not the case.
None of these conditions are at all desirable.

[molan]

Wow, I've just waded through all six pages here - some very interesting stuff

For what it's worth - and I am no expert here, just using my ears - I had a head for a while with a variable crossover and an option to bi-amp. At the time I was running a 1x15 & a 2x10 with the same output going to each. I tried experimenting with the crossover and feeding only the lows to the, tweeterless, 1x15 and the highs to the 2x10.

The amp had a fixed output per channel so I couldn't adjust the power to give the lows a higher output but the variable crossover allowed me to really play with the frequency range. Took a lot of fiddling around from a friendly sound man and moving all over the room to get a different perspective on the sound (I was running a wireless as well at the time) along with a VERY patient drummer but I eventually managed to get something I was fairly happy with.

I was, at the time, really surprised to discover that the final crossover frequency had been set so that almost everything was coming through the 10's and the 15 was really just providing some low end thump.

Having spent all this time setting something up we just pulled the crossover out and ran them as a stereo pair again and all decided that we couldn't really 'hear' enough difference to bother with setting an accurate crossover frequency. The cabs worked 'OK' as a mis-matched pair (they were even different manufacturers) to our uncultured ears.

Funnily enough I've just picked up a pair of mis-matched EBS cabs, a 2x12 & a 2x10 and the sales pitch that finally lured me in was as simple as:
[i]
"The 212 kicks you in the nuts as the 210 hits you in the face!"[/i]

Not very scientific but it worked for me

[lowhand_mike]

i can understand roughly what those guys were saying about wavelengths etc but are they actually talking about speaker positioning (as in speaker enclosures assuming the drivers therein are matched and crossed correctly) within a round for good sound production within a stereo or Home theatre environment? i am assuming they are looking at the best possible placement to get the best possible sound and as such have limits to work to within the bounds of their chosen room.

where-as we are talking about the wave lengths coming from a single box, the bass cab and the frequency range they work in. the only thing they are fighting with is their own drivers IF there are more than 1 and the box and the size of the room they are being used in and how their own wave lengths interact with each other.

i need some clarification on that if possible.

also i have a gig this weekend which is outside, are these points moot in this situation?

i get enough grief at work for being a bit of a geek but i'm taking it to the next level now

[Bill Fitzmaurice]

[quote name='lowhand_mike' post='222016' date='Jun 19 2008, 06:31 AM']i can understand roughly what those guys were saying about wavelengths etc but are they actually talking about speaker positioning....where-as we are talking about the wave lengths coming from a single box,.[/quote]Both. The rules that apply for placement of speakers within a room also apply to drivers within a cabinet. Just think of the cabinet as a room within which drivers reside, and that what differs between the two scenarios is the size of the 'room'.
[quote]centre speakers for home cinema and lots of centres have two woofers each side of a tweeter[/quote] Same rules, you need to cross the woofers to the tweeter no higher than the 1 wavelength center to center distance between the woofers. But that only addresses combing, not dispersion, which is better on the horizontal plane with the woofers vertical. The inability to place woofers vertically below a TV is problematic, but can be compensated for by having them in a concave array.

Edited June 19, 2008 by Bill Fitzmaurice

[lowhand_mike]

[quote name='Bill Fitzmaurice' post='222168' date='Jun 19 2008, 02:20 PM']The inability to place woofers vertically below a TV is problematic, but can be compensated for by having them in a concave array.[/quote]

the same as in cross firing?

think i'm slowly getting this

[gypsymoth]

it is perhaps worth noting that all these problems were recognised waaay back, which is why Pink Floyd worked with WEM on their early stage set up, and as someone might have mentioned, Alembic was created. the Rickenbacker 4x12 from '69 is a large trapezoid, bottom two speakers vertical and the top two horizontal in the wider portion.

I think the easily transported smaller boxes won out at least partially because of the improvements in PA's. if you are not sticking a mic in front of one speaker then it's balancing transport size with sound quality. and if you are ....

or maybe it's visual image/sounds just like whoever,. which seems to be very important in the vox/marshall markets.

[Bill Fitzmaurice]

[quote name='lowhand_mike' post='222228' date='Jun 19 2008, 10:27 AM']the same as in cross firing?[/quote]
+1, though you don't have to limit yourself to a pair of drivers, you can use four or more to get the added sensitivity of an array.

[quote]it is perhaps worth noting that all these problems were recognised waaay back[/quote]+1, though waaay back starts in 1927, when films added sound. Until the 1970s most of the innovations in sound technology were driven by what was the single largest industry that employed sound reproduction, and that was the moving picture industry. The shift away from the movie industry as the leader in the field started with the introduction of the VCR, which made home theater a reality. In terms of units sold home theater now accounts for the largest slice of the audio pie.

[gypsymoth]

we didn't have electric bass guitars in 1927, so the "issues" in this context weren't really recognized until the excitement of a P-bass through a bassman faded a bit and the limitations noticed. still, for many, the fender/fender combination is IT and is unbeatable - because that is what this contraption is supposed to sound like - technically right or not.

[Bill Fitzmaurice]

[quote name='gypsymoth' post='222372' date='Jun 19 2008, 01:27 PM']the fender/fender combination is IT and is unbeatable - because that is what this contraption is supposed to sound like - technically right or not.[/quote]My first Fender/Fender wasn't first generation, but close enough to it, 1965 Jazz/Bassman, bought new. The damn thing farted out on the first low E I hit and every one subsequent. Never satisfied with how inept it was at actually producing useful bass I studied audio engineering to find out why. Today I owe my livelihood to Leo Fender's never having done the same.

[gypsymoth]

please note I said "for many". one has to recognise this - even if, like you and I, it's not what we prefer.
I'll tell you what I can't stand - ampegs with 8x10's. I sure hate being told I should get one.

[bass_ferret]

[quote name='gypsymoth' post='222470' date='Jun 19 2008, 08:34 PM']I'll tell you what I can't stand - ampegs with 8x10's. I sure hate being told I should get one.[/quote]
tell them you will play it but they can carry it! That should see them off

[tauzero]

[quote name='stevie' post='221577' date='Jun 18 2008, 05:42 PM']Here you go ,mike. [url="http://www.htguide.com/forum/showthread.php4?t=29184"]http://www.htguide.com/forum/showthread.php4?t=29184[/url]

Have a look at the post from Kal Rubinson, a well respected audio journalist who writes for Stereophile. He says:

"Yes. 1/2 wavelength is the generally accepted spacing maximum.
Dunno about d'Appolito's standard but ANY two drivers spaced more than 1/2 wavelength apart and reproducing the same signals will show destructive (and constructive) interference in the plane OF their displacement."[/quote]

If they're 1/2 wavelength apart, a little thinking about the geometry of the two drivers and the listener's ear will show that the only place you can get phase cancellation will be if you are in line with them, ie. at 90 degrees to the speaker axis. If they're .7 wavelength apart, you'd get phase cancellation outside 45 degrees off-axis. You can only get phase cancellation over the whole arc in front of the speakers with 1 wavelength separation, if my quick scribblings and mental arithmetic is correct.