Speaker cabinet sound - basics for noob

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pure.fusion

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Hi all,

Yes, my mind goes around and around on the speaker, isolation box and tone issue....

A buddy of mine came over on the weekend and we recorded a whole bunch of different amps and pedals over 4 hours - it was fun, and an eye opener.

For me, he plugged into my Fender Blues Jr a separate, custom built speaker cabinet with a 12" Lorantz speaker in it and what a sound it made. Unfortunately, I think I prefer the Lorantz sound of the his over the stock Fender.

Anyway, basics!. If I wanted to buy a 12" driver (choosing from the *large* array of possibilities (the next issue!)) and stick it in a box, HOW MUCH does that box change the speaker's sound? Big time? Some? None?

The Blues Jr cab is open back. If I mimic the cabinet shape of the BJ (for example) in MDF but leave off the back sections, will this have a significant bearing on the sound?

The bottom line is, I buy a 12" driver, I either put the speaker in an Isolation box and mic up, or I put the speaker in a MFD cabinet the same dimensions as the BJ, then put the whole thing in a larger box to keep it quiet.

What the hell, it's only space and the cost of the MDF (and the cost of the speaker of course).

The outcome: I (and my wife) get quiet recording and practice. I get a nicer tone from a new speaker. The BJ stays untouched and intact in case I want to sell it and buy a valve head).

Please let fly with the theories, physics lessons and rotten tomatoes!

Cheers,
FM
 
I think you should build a full, dual 4 X12 stack and point it out the window, and let the neighbors worry about it! :D
 
But you asked a question so I'll tell you what I think I know.

First, on the subject of cabinet construction. Yes, you can just duplicate the dimensions of the BJ box, make a box out of MDF, and as long as it's well put together it will sound just fine. MDF is a great construction material for speakers, as long as they are not going to be subjected to the elements or thown into the back of a van regularly. I recommend 3/4".

Mimic the back side of the BJ with your box design and you'll have a similar-sounding box. Close it up and you will get a bit less efficient system, spl-wise, along with a more front-focused sound and tighter bass with maybe a little less ultimate bass extension into the low frequencies.

Iso boxes - I dunno. If you throw your small speaker cab into a bigger, insulated box you will get a very dry, sterile sound and you will need to add room ambience (if you want it) with FX. That may be an acceptable tradeoff for you just to get your volume down. Instead of an iso box you could just clear out some floor space in a smallish clothes closet and mic up the cabinet in there.

Closed-back vs open-back in an iso box? I have no clue but I would guess that the attributes of an open-back cab would pretty much disappear inside an iso box. It would be easy enough to build two backs for your speaker cab, though, and experiment.

Good luck. :)
 
In my experience, open-backed cabinets have more high-end freqency response than closed back cabinets. Closed back cabinets have a much more defined and tight midrange, which may or may not be what you want.

I play a Fender Hot Rod Deville and a H&K 20w amp through an avatar 2x12 closed back cabinet. If I just play through the close back cabinet, I find that when playing live my guitar doesn't have the 'energy' I expect from a live rock and roll show. But when I use just the DeVille, you have to really crank the mids to cut through the mix. The solution for me is to use both.

When recording though, I record almost exclusively through the Avatar, but I'm usually driving it with the DeVille.

Hope that helps.
 
Zaphod B said:
I think you should build a full, dual 4 X12 stack and point it out the window, and let the neighbors worry about it! :D
Click to expand...

Hehehehe. You're a bad man...

I dunno. I'll let you know what happens, if it happens.....

I'll probably go the Isolation box on it's own first. It's the easiest to try. One big box with a speaker in the centre of if. If it sounds crap, I'll go option B.

FM
 
pure.fusion said:
Hehehehe. You're a bad man...

I dunno. I'll let you know what happens, if it happens.....

I'll probably go the Isolation box on it's own first. It's the easiest to try. One big box with a speaker in the centre of if. If it sounds crap, I'll go option B.

FM
Click to expand...

A while back I built a giant box with a lid. It's purpose was to serve as a giant ISO box being able to fit a computer speaker all the way up to a 4x12. I sealed the corners to keep air from leaking and planned on putting OC705 or some other absorbing material where ever I could in it.
I haven't gotten to the point of getting the absorbing material in it yet but now that I've learned much much more about acoustics I realize it probably wasn't the best idea in the world.

My only concern is that with high SPL's the sound will still bounce around way to much inside the box even with a given amount of absorption thus making the sound you get from the mic "boxy"

I'd be grateful if you let me know the results you get from your ISO box tests.
 
ocnor said:
Save yourself the grief and go with option B. http://www.mercenary.com/pdi09figudib.html
Click to expand...

but what about the sound of the speaker? That counts for some of your tone, yeah? How the speaker vibrates? The waya greenback has "early breakup" and some other brand doesn't?

I think i'd prefer the boxy sound over the lack of realism.

Having said that, I probably can't even identify a "boxy" sound yet :p

Aparrently my Blues Jr has one. Sounds fine to me...

FM
 
pure.fusion said:
Having said that, I probably can't even identify a "boxy" sound yet :p
Click to expand...

take your amp and stick it in an empty coat closet with a mic anywhere you prefer.
jam on it a little and listen to it through monitors.
that's a boxy sound.
 
Ahh, that's bad news.

So, any box I build that's smaller than a coat closet will sound boxy, any larger and I may as well not build one.

Maybe we try the minimal approach....

http://www.nasaomusic.com/galerie/Aufnahmeraum/Aufn6.JPG

... type thing and add effects.

Maybe I should post a sample and get your opinion on the sound as it is now. What's the best way to post MP3's at the forum?

FM
 
Hmmm, I can help a bit:

- the acoustics of an enclosure are the same at low or high SPL

- enclosing an amp in a bigger enclosure is not quite the same thing as enclosing a speaker in an enclosure of that size. It gets complicated, but for an open-back cabinet, there is no net increase in pressure inside the enclosure as the moment of the speaker cone cancels out front-to-back. If you put a sealed box inside a sealed box, you will still mostly be subject to the loading from the smaller sealed box. If the larger enclosure is heavily damped, then of course its effects are lessened. If you put a ported enclosure inside a larger enclosure, it could get a bit more complicated but I'd still think the smaller enclosure would have the dominant acoustic effect--I think the larger box size would be too large to have as significant an effect as the ported enclosure. And of course, there is still damping to consider. Now, if the smaller box takes up most of the volume of the larger box, then that would not be true.
 
mshilarious said:
Hmmm, I can help a bit:

- the acoustics of an enclosure are the same at low or high SPL

- enclosing an amp in a bigger enclosure is not quite the same thing as enclosing a speaker in an enclosure of that size. It gets complicated, but for an open-back cabinet, there is no net increase in pressure inside the enclosure as the moment of the speaker cone cancels out front-to-back. If you put a sealed box inside a sealed box, you will still mostly be subject to the loading from the smaller sealed box. If the larger enclosure is heavily damped, then of course its effects are lessened. If you put a ported enclosure inside a larger enclosure, it could get a bit more complicated but I'd still think the smaller enclosure would have the dominant acoustic effect--I think the larger box size would be too large to have as significant an effect as the ported enclosure. And of course, there is still damping to consider. Now, if the smaller box takes up most of the volume of the larger box, then that would not be true.
Click to expand...

Urm..... let me digest that for a while..... there's likely to be questions....
 
mshilarious said:
Hmmm, I can help a bit:

- the acoustics of an enclosure are the same at low or high SPL

- enclosing an amp in a bigger enclosure is not quite the same thing as enclosing a speaker in an enclosure of that size. It gets complicated, but for an open-back cabinet, there is no net increase in pressure inside the enclosure as the moment of the speaker cone cancels out front-to-back. If you put a sealed box inside a sealed box, you will still mostly be subject to the loading from the smaller sealed box. If the larger enclosure is heavily damped, then of course its effects are lessened. If you put a ported enclosure inside a larger enclosure, it could get a bit more complicated but I'd still think the smaller enclosure would have the dominant acoustic effect--I think the larger box size would be too large to have as significant an effect as the ported enclosure. And of course, there is still damping to consider. Now, if the smaller box takes up most of the volume of the larger box, then that would not be true.
Click to expand...

We need to talk, bud :mad:
 
mshilarious said:
It gets complicated, but for an open-back cabinet, there is no net increase in pressure inside the enclosure as the moment of the speaker cone cancels out front-to-back.
Click to expand...

So, to be extra specific here, does the above include the situation where I have part of the back of the "Open back" cabinet covered by wood? (About 1/2 of the back is covered in Blues Jr) Does this still count as "open cabinet" ? Will it make any difference to the sound if I remove or keep the half piece of rear covering?

As for the rest, I'm having trouble relating.

I should do more research on ISO boxes but from what I can tell so far, to keep the noise level down, they are sealed. So there is effectively one big box, separated into two sections by a speaker with (i can't beleive this) no air flow between the two halves. Can you comment on this?


FM
 
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