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Cab design ?

fuzzy beard

fuzzy beard

Mar 8, 2011
2,747
31
Aurora, Indiana
#1
Just got home from checking out the new ampeg pf cabs and heads. Found them to be amazing!

But while looking at them i noticed i did not see any baffling? It seemed to be just a box with speakers and some padding around the sides. And from what i have been reading cabs are not suppose to be so simple!

So how do they sound so good and not real boomy? I love the design and concept of the cabs. And had a hard time leaving with out the pf350 and 115.But still a little heavy for what i want. I would love to see a 112 cab offered with the same flip top options.That would bring the weight down and still have the flip top storage and convinence.

But then again i guess there is no reason for a pf112. You could just get a 112 combo.
 
#3
Well, I'm not a design god, but I have some info on speaker design theory at my little website. And I'm interested in this stuff.

Actually a plain sealed or ported speaker doesn't have to be complex, but one of the "upgrades" to the basic design is to make it a lot lighter.
 
#5
What do you mean by the upgrade comment?I dont understand what upgrades would make it lighter?

will33 yes it was lined.I thought baffles where in cabs to cut down sound wave bouncing inside the cab. I didnt know that the front panel was called a baffle. I guess when i hear baffle i think like a fuel tank that has baffles to keep fuel from sloshing around to much. Are all cabs just boxes with a speaker in the front?Granted i know we are not talking about ported cabs.
 
#7
All cabinets are highly dependent upon the parameters of the speakers. Speakers designed for sealed cabinets may not sound as good in ported cabinets, and vice versa.

So, you take a sealed box, make it big enough, put a driver with a high Q in there, and stuff it appropriately, and you'll get a cab that isn't boomy!
 
#9
I'm so not a speaker guru, but I happen to know that the reason for having the padding is to kill standing waves inside the box. In a sealed cab, there should be foam stuffing. In ported cabs, the inside walls should be lined. But it's possible that Ampeg figured that was all they needed to do to kill the standing waves in that cab. The old Portaflex cabs were ported, and only the back wall had any padding in any of them, and that doesn't conform to the rule that all inside walls should be lined, yet when I added padding to the other walls, it didn't make a difference to the tone. That padding on the back wall was enough to do the job.

So maybe the reason they sound amazing is that the existing padding is enough to do the job.
 
#10
Bracing and some sound-absorbent material are usually sufficient to get good sound from a speaker + well-designed box, unless the designer wants to do something fancy like a transmission line. I built literally tons of transmission line speakers as an amateur, and don't think they are cost-effective if labor expense is included (which it is for the pro, but often not for the amateur).
 
#11
JimmyM said:
when I added padding to the other walls, it didn't make a difference to the tone.
Click to expand...
It did, but the only way you'd notice it is if you had both versions side by side to listen to. Lining only the back does about 80% of the job, so lining the sides as well is a relatively minor additional improvement.
 
#12
OP the "techgnology" behind making the cabs lighter is to use thinner plywood and brace it more to make it rigid enough so it doesn't vibrate/resonate. That way of doing it adds a lot of labor cost to the build. People keep buying the simpler/thicker wood boxes so there's no reason for companies to do it on a large scale. Wood density is a factor as well.

T-lines and horns do have internal panels and patterns the may resemble fuel tank baffling a little bit but that stuff's designed in a specific way to direct and enhance soundwaves and specific frequencies. The how's and why's of the way they work is well beyond my pay grade as I'm far from being a god as well. I read up on them and might understand just enough to get myself in trouble or say something stupid. :)

The horn is perhaps the most efficient design and works on the same principle as a tuba taking the little buzz from your lips and turning it into a big deep loud sound. The speaker provides the sound source like your lips did in the tuba and the horn is made of angled wood panels instead of rolled/shaped brass.

I stick to my "regular" boxes and leave the rest to the pro's.
 
#13
billfitzmaurice said:
It did, but the only way you'd notice it is if you had both versions side by side to listen to. Lining only the back does about 80% of the job, so lining the sides as well is a relatively minor additional improvement.
Click to expand...
I will admit that my critical listening skills are maybe not the most superb out there, but I have two B-15 extension cabs that use the same driver, and I honestly couldn't tell the difference. But now that you said this, it makes me want to go try it again and see if I still feel the same way. Probably won't do it, though...I get ambitious about stuff like that for 10 minutes, then I forget about it if I don't immediately do it ;)
 
#14
So why is the front panel called a baffle? In every thing else i know about(deisel mechanic) baffles are used to slow down flow. That being fluid or air. Guess i heard baffle and had my own ideal about what was inside there.

Also what is meant by a good design box? It looked as simple as a box and speakers! I know there is more to cab design or everyone would just build there own. Can anyone link me some cab design reading?

Also anyone else like the flip top 112 ideal? Has it been done?
 
#16
fuzzy beard said:
So why is the front panel called a baffle? In every thing else i know about(deisel mechanic) baffles are used to slow down flow. That being fluid or air. Guess i heard baffle and had my own ideal about what was inside there.

Also what is meant by a good design box? It looked as simple as a box and speakers! I know there is more to cab design or everyone would just build there own. Can anyone link me some cab design reading?

Also anyone else like the flip top 112 ideal? Has it been done?
Click to expand...
Yes, about 50 years ago by Ampeg.
 
#17
Can't do links from a phone but these guys can point you to some good reading. A search will turn up lots of good stuff. There's a good explanation of thiele/small parameters in eminences site. WinISD Pro is a free download program to model woofer/box interaction but you have to know what this stuff means to make use of it.
 
#19
There is nothing wrong with your general understanding of the word, its just that it has a special meaning in speaker designer jargon. The "baffle" in that context is the divider [baffle] between the front and rear sides of the driver... as in infinite baffle:

Loudspeaker enclosure - Wikipedia, the free encyclopedia

or open baffle

Link Removed

OTOH in architectural acoustics a baffle is a panel of a porous absorber material used to diminish the persistence of sound reverberation in a room... which is closer to what your are used to using the word to describe. Don't fight it - its just jargon.

http://www.elektor.fr/StreamFile.lynkx?path=Uploads/Forum/Posts/Playing-With-Baffles.doc
 

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