Open or Closed back cab - cannot hear the diff's

[SirJackdeFuzz]

OK, so i have a Blues Jr. with a semi open back cab.

Openning is 15,5cmx42cm . . . FWIW.

I got this great idea, of making it a closed back cab, to see if it will make a big diff !
Got a piece of Pine that fill the gap perfectly, with just a wee hole for the elecrtical cord. Man, i even added a nice wooden handle to this, "temp-hole-stopper".

So, i started to play . . .


. . . with, & with-out. Then, with, & with-out, again, with, & with-out, and so the afternoon came and went, and i still can not heat ANY DIFF's !!!

Can anyone please tell me why i could not hear a diff in tone or any diff in the sound what so ever !!!

I am starting to feel stupid !

The amp was 1 foot away from a wall, then 6 feet away from the wall, and the vol was on 75-80%. (the whole time it stood on a 1 foot high wooden stand on a carpet) Also used my Epi LP & Artcore full-hollow.

THANX GUYS !

 

[marvar]

Re: Open or Closed back cab - cannot hear the diff's

The differece would be more in projection than actual tone, play the cab open standing 10 feet away, and then move left and right from center. then play it closed the same distance, same movement. If you don't hear a difference, have your hearing checked.

 

[tone4days]

Re: Open or Closed back cab - cannot hear the diff's

try the same experiment with the amp on the floor and let us know how it goes

 

[SirJackdeFuzz]

Re: Open or Closed back cab - cannot hear the diff's

Thanx guys - that might help, as the whole time, i stood either 6 feet or about 12-14 feet away, but dead centre.

Never moved side to side though !

 

[SirJackdeFuzz]

Re: Open or Closed back cab - cannot hear the diff's

OK, this is what i noticed so far !


Got the girlfriend to help out this afternoon.

Vol. on about 50-60% this time round !
Amp again 6 feet from nearest wall !

I sat flat on my @r$e, 7-8 feet back, and about 4-5 feet to the left.
Centre of speaker a few inches lower than my ear-hight.
Started playing with back closed, and 1min into jamming, the gf took it out as fast as she was shown (good girl !).

Low and behold. I HEARD THE DIFF's !!!

ERMmmmmmmm . . . not a big diff. but yes, there was a slight diff. in the charataristic (sp?) in the way the sound got produced (projected, more correct term ?).

So we carried on for the better part of 10min.
Then off, then on, then back again, then way !
I really thought there would be a much bigger tonal variety in the sound !?

And guess what . . .

. . . i prefer the open back more to the closed back.

I just sounds more , ermmmm . . . "open" and alive to my ears !

I do not think that anyone will notice the diff. in the crappy little venue (100 person max. capacity) that we play in. Seeing that almost everyone is 16-26, and non muso's to boot !

So, looks like my amp will stay open back, untill i get a SuperSonic/Bassman/Deluxe Reverb/Mesa LoneStar - but i think they too, are all open-backs !

 

[kmcguitars]

Re: Open or Closed back cab - cannot hear the diff's

Simply closing up the back of a combo is not going to give you your desired effect IMO. Good Closed back Cabs are designed w/t the proper depth to project sound.

 

[bungalowbill]

Re: Open or Closed back cab - cannot hear the diff's

Simply closing up the back of a combo is not going to give you your desired effect IMO. Good Closed back Cabs are designed w/t the proper depth to project sound.

+1 .....and if you close the back of a JR for a length of time, it could become overheated and have some negative effects. Get a closed back cab for it.

 

[Curly]

Re: Open or Closed back cab - cannot hear the diff's

I agree ... the best way to A/ B would be to try a regular 1x12 cab.

the BJ is a little boxy sounding due to the smallish cab, but it is still a great little amp

 

[Robert S.]

Re: Open or Closed back cab - cannot hear the diff's

I closed the backs on my Mesa 112s and the difference was huge. I lost a lot of top end and the tone was very muddy.

With the Mesa 112s it makes a huge difference.

 

[WhoFan]

Re: Open or Closed back cab - cannot hear the diff's

I love adding the closed back 1x12 to my Classic 30 open back combo.... the closed back 1x12 adds bass for some reason.. very nice.... best of both worlds.. maybe the same could be true for a Blues JR

 

[Kivitel]

Re: Open or Closed back cab - cannot hear the diff's

An open back turns the speaker into a dipole - ie the sound coming off the back of the cone is exactly out of phase with that coming off the front. Now, this can be a good thing because it makes everything sound more open (since there isn't a sealed volume on the back of the speaker acting as a spring against it's movement). However, what does happen is that the two sound waves, coming off the front and back, since they are out of phase, will cancel each other out roughly in line with the plane of the speaker (ie off to the side). This can be nice as it will sometimes have the affect of attenuating reflections off the back wall - but you definitely want to have the thing away from that wall.

The walls on the side of the speaker, of course, muddle that effect, so you gain a weird sort of open-ness with some weird dead spots in the room, and bass won't be as good, unless the baffle is somewhere near the size of the minimum hz you want to get (the length of an 80hz wave of course being way larger than any speaker cabinet).

Anyway the difference between hifi and guitar is that in guitar all the mistakes and innacuracies that don't affect responsiveness or practicality actually add to 'tone' and 'grit' and whatever else.

One thing you should be aware of is the affect of standing waves in your room. Basically, if you have a speaker that is in the middle of one wall of a rectangular room, and you have it producing a tone which has the same wave-length as some whole number divisor of the length of that room, the waves coming off the back wall will at that one frequency not cancel each-other out when they reflect - instead they will be perfectly in phase, getting louder and louder and louder for that one freq. This is why in certain clubs the bass is just unbearable for like one or two specific notes.

The trick to avoiding this is assymetry. Just put everything at weird angles.

ymmv, btw I just got up and my slight lack of expertise combined with my lack of ability to think clearly isn't helping. My advice is this: keep the back open so you can stuff cords and **** in there. If you want to make a bass-reflex cab that actually works it will take a hell of a lot more math than most people are willing to learn.

 

[That90'sGuy]

Re: Open or Closed back cab - cannot hear the diff's

Yep, I agree with everything said here. Open cabs are well, open sounding. Closed back cabs typically have more lowend focus and punch, but they may be too compressed for some.