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Post subject: Bass Cabinets & Sonic Damping
Posted: Fri Sep 06, 2013 9:17 am
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Your thoughts?

I am thinking of lining my Rumble 75 Combo with Sonic Barrier

http://www.parts-express.com/brand/sonic-barrier/494

1/2" foam on the back and vinyl sheeting on the sides and top.

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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Fri Sep 06, 2013 11:07 am
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I'd go with something thicker. I've used this stuff for the past couple of years and it works great. I use Super 77 to attach it. Every cab I've lined with it has become far less "honky" in the low midrange and upper bass.

If there's already some damping in there from the factory, and if it's not junk, then putting damping everywhere (except the baffle board of course) may offer only limited additional benefit. You may even wind up with an overdamped (dead) box. Tough to say without actually trying it. You get the most benefit by lining one wall, typically the rear one. Lining the remaining walls may still provide some benefit, but only incremental.

Hope this helps.

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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Fri Sep 06, 2013 11:53 am
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Thanks Craig, but that thick eggcrate foam is just going to take up far too much space inside such a small and crazily angled box. There really is no midrange honkiness at all. The combo is very well designed anyway you approach it. It doesn't rattle at all even at high volume levels, and given proper EQ it doesn't boom or honk.

What I am hoping to achieve is a more tightly focused bottom and additional midrange punch. $50 to line an unlined M.D.F. cab isn't too much to spend really if there is a tangable sonic payoff.

It will most likely void my warranty, but I've had this amp well over a year now, and it's been rock solid all along.

An Eminence Beta12A-8 might also find it's way in. :wink:

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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Fri Sep 06, 2013 4:53 pm
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Never heard of this stuff before. "Speaker Cabinet Coating - Acoust-X Sound Damping Coating"

http://store.acrytech.com/Speaker-Cabinet-Coating-Acoust-X-Sound-Damping-Coating.html

$27/gal

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2017 Lefty American Professional Precision
2018 Rumble Studio 40 Combo
2016 Rumble 200 Combo
One day they shall name a GREAT city after me, and they shall call it LINNINGRAD


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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Sat Sep 07, 2013 5:18 pm
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What are you looking to do with this, change the tonality?

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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Sat Sep 07, 2013 6:25 pm
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CPL wrote:
What are you looking to do with this, change the tonality?


Not the tonality in totality, but hoping to futher tighten; define, clarify, and focus the tone.

By not having reflected sound waves bouncing around inside a naked unlined cabinet by damping/absorbing stray sound. From what I have been reading the only sound you want is what is coming off the front of the speaker cone, and that the only thing that should be moving in and out of the tuned ports is air, and not sound. The lining also increases the apparent volume of the cabinet. How that works, I don't know.

So what I'm looking for is better overall sound quality. A tighter more focused bottom and punchier mids are desired. Better balance across the frequency range within the limitations of the speaker & cabinet design. Fortunately I'm not trying to make a silk purse out of a sow's ear. The Rumble 75 is an excellent sounding combo. I just want to put some lipstick on this pig so to speak.

So this is a kind of ongoing experiment. Just tossing an Auralex GRAMMA under the Rumble really made a very positive sonic difference. So putting $40 into good quality acoustic inslutation/damping material could be a very cost effective way to make your Rumble sound better!

Or it could be folly. I'll let you know! :wink:

I am not going to change woofers at this point. The exisiting speaker has a very solid low end and is not flabby or boomy in anyway. It exhibits excellently quick response/punch/thrust. One change at a time.

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2016 Rumble 200 Combo
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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Sun Sep 08, 2013 9:50 am
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linnin wrote:
The lining also increases the apparent volume of the cabinet. How that works, I don't know.
.

I'd be interested in knowing more about that notion myself. Until you made this comment I was thinking it would reduce the volume of the cabinet.

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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Sun Sep 08, 2013 10:43 am
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BMW-KTM wrote:
linnin wrote:
The lining also increases the apparent volume of the cabinet. How that works, I don't know.
.

I'd be interested in knowing more about that notion myself. Until you made this comment I was thinking it would reduce the volume of the cabinet.


Physically the volume of the cabinet is reduced, but acoustically, however, it is counter-intuative giving the same effect of a larger cabinet by means of eliminating standing waves and damping/absorbing reflected waves from ricocheting around inside the cab.

Ideally you want air and only air moving in and out of your cabs tuned ports. Also the only sound you hear is coming only from the woofer's cone. Being 'denizens of the the deep' we know low Hz freqs penetrate concrete walls with ease, so you are going to get some sound coming through cab itself, but good damping will minimize that anomaly.

So that's what I think I know. Ha! :lol: Someone that really knows, such as Craig P., will show up to correct me.

Good acoustic insulation reduces or eliminates: mudiness; boominess, and honkiness. At best it will give a tighter and more clearly defined bottom end while also focusing the low mids. Or so I've read. The proof will be in the results of this project. At any rate it can't be a bad thing to judiciously line a bare bass box with some high quality acoustic damping material.

_________________
2012 Lefty American Standard Jazz
2017 Lefty American Professional Precision
2018 Rumble Studio 40 Combo
2016 Rumble 200 Combo
One day they shall name a GREAT city after me, and they shall call it LINNINGRAD


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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Sun Sep 08, 2013 12:47 pm
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My old Peavey 2x15 cab, that I still have, was lined with what looked to be fibergalss insulation. Mice made me yank much if it out. Cab sound like crap now. I am thinking of getting a few mats of insulation and stapling them back in. Not using the cab now, but it is a project I want to get to.

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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Sun Sep 08, 2013 3:40 pm
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modwiz wrote:
My old Peavey 2x15 cab, that I still have, was lined with what looked to be fibergalss insulation. Mice made me yank much if it out. Cab sound like crap now. I am thinking of getting a few mats of insulation and stapling them back in. Not using the cab now, but it is a project I want to get to.


I remember those old Peavey 2x15 cabs when the were new! Guess what?! They sounded like crap then too!!!

Congratulations. You've just been...

LINNINIZED!

Quick! Call The Cops!

I'm pretty sure you get a free t-shirt from Fender.

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2017 Lefty American Professional Precision
2018 Rumble Studio 40 Combo
2016 Rumble 200 Combo
One day they shall name a GREAT city after me, and they shall call it LINNINGRAD


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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Sun Sep 08, 2013 5:32 pm
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linnin wrote:
modwiz wrote:
My old Peavey 2x15 cab, that I still have, was lined with what looked to be fibergalss insulation. Mice made me yank much if it out. Cab sound like crap now. I am thinking of getting a few mats of insulation and stapling them back in. Not using the cab now, but it is a project I want to get to.


I remember those old Peavey 2x15 cabs when the were new! Guess what?! They sounded like crap then too!!!

Congratulations. You've just been...

LINNINIZED!

Quick! Call The Cops!

I'm pretty sure you get a free t-shirt from Fender.


Thanks. You might have saved me some work. :D

Call the cops. Sorry, not looking to get tasered. Fender T-shirt has to be 100% cotton or it's a no go.

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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Mon Sep 09, 2013 6:23 am
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OK, the order is in. 1 sheet of 1 1/4" 3-layer composite Sonic Barrier for the back of the cab, and 1/2" sonic barrier for the sides. May have enough to line the top. Bottom to remain naked, as that is where the porting is. This should work nicely even if a bit spendy at $70 shipped.

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2018 Rumble Studio 40 Combo
2016 Rumble 200 Combo
One day they shall name a GREAT city after me, and they shall call it LINNINGRAD


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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Mon Sep 09, 2013 6:42 am
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In the pre-Thiele/Small days, manufacturers did the best they could with repeated cycles of build/test, build/test, build/test. (Let the wood chips fly where they may.) Sometimes they blew it big time, but sometimes they actually blundered into truth. I've never been a fan of porting schemes where a hunk of wood is hogged out of the baffle board (effectively a port with a length of 0.75"). That's not a port; that's a hunk of wood hogged out of a baffle board. More often than not, pulling a stunt like that only gives you a boom box that shouts out one note, while the others are just a muddy wash. Some respected manufacturers made a couple of those. Not a fan, never was.

However, in the '70s Peavey made a criminally-disrespected 2x15 cab that had only two really significant flaws: it wasn't internally damped, and its drivers were the era's typical crap CTS or Eminence square magnet jobs that couldn't manage more than 1 mm or so of stroke before they gave up with mighty farting. (Or burned their puny voice coils first.)

That cab was the 215. No suffix; just the 215.

The way Peavey designed that cab holds up well today. The trap they did NOT fall into, which almost all ported bass cab manufacturers still fall into today (yep, even the boutique makers) was making the cab too large. Designing a bass cab large in order to get flattest possible extension into the bass region -- a nod to players with B strings on their instruments -- is unwise in my opinion, because all that does is increase the likelihood of driver overexcursion at the low end when the cab is loaded with anything less than a premium driver. When I say premium driver, I'm talking about drivers than can go way over your average brand-name driver's 4-5 mm Xmax. (And few factory drivers can manage even that.)

Designing a cab large to permit volume fundamentals from a B-stringed instrument is fine if you're sure the application will include, somewhere in the signal chain, a steep high-pass filter matched to the cab's capabilities. I'm talking about 18 dB/octave or steeper. The problem is, you can't be sure there'll be one. In fact, you can make a safe bet there won't. Most players have no clue what a high-pass filter is; most of the ones who do don't see the need to bother. That is, until they experience a good dose of cone crease, at which point they'll blame the manufacturer instead of looking in the mirror.

Anyway, Peavey's 215 design, in my opinion, was brilliant because it split the difference between driver protection (small cab) and bass extension (large cab). At effectively 2.6 cubic feet per half -- the cab is, after all, two totally separate 1x15 cabs -- the response can be flat to 70, -3 dB at 60, and -9 dB at 40. Nothing to write home about, you say? You'd be right, except in the real world you really don't need better bass extension than that. (Read up on overtones and the concept of missing fundamental and you'll get it.) Lest you still doubt, I refer you to the SVT cab's response curve. The SVT is no slouch when it comes to bass impact, and you can hit it hard with almost any head you can imagine. Give me driver protection over bass extension any way. Job Number One for any bass cab is that it's got to make it through the gig unscathed. This is another reason why SVT cabs are so popular as backlines. They survive exposure to ignorance.

Suppose I told you I could design and build you a 215 cab that would be louder than anything you've ever heard, sound better than anything you've ever heard, hit your club's dancers harder than anything you've ever heard, would take a 5-string in stride, could handle its drivers' full thermal voice coil burnout rating all the way down to low (open) B without hitting their Xmax, and you could use that cab with any amp up to 800 watts RMS? (SVT you say? Hah. Bring on that puny little thing.) Oh yeah: and be twice as efficient as your average 215 or 810, so your amp would sound twice as loud? Well, my box design would be very close to the 215. Internal size would be similar. I'd make only a couple of minor porting changes, I'd add some bracing, I'd install thick foam lining on all surfaces, and I'd change the phone jack to Speakon. Oh yeah, and the cab would be 25% lighter, too.

My point is that the 215 cab would work acceptably with just the addition of the internal lining and the Speakon, without the rest of the changes -- because the platform is valid as is.

So, in my opinion, Peavey came real close to nailing it with the 215. If that Peavey cab you have is a 215, and not one of its later/larger variants, don't be too quick to snub it. It's a rough-cut diamond.

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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Mon Sep 09, 2013 3:52 pm
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craig.p wrote:
So, in my opinion, Peavey came real close to nailing it with the 215. If that Peavey cab you have is a 215, and not one of its later/larger variants, don't be too quick to snub it. It's a rough-cut diamond.


Thanks for the history and information. I obtained my cab in either '75 or '76. It was second hand and at least a year old when I got it. I was surprised to see the detail that is going on in that cabinet. The extra wood sure adds weight. The original wheels are still on there. The wheels are wood. I got mine with two EV 15's. I still have one of them. The other is a Seismic audio replacement. I guess playing with it can't cost too much unless I start needing to find the "perfect" speaker(s). I perfectly good idea sound-wise. However, the fiscal danger aspect looms in the equation.

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http://www.reverbnation.com/modwiz


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Post subject: Re: Bass Cabinets & Sonic Damping
Posted: Thu Sep 12, 2013 10:40 pm
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linnin wrote:
BMW-KTM wrote:
linnin wrote:
The lining also increases the apparent volume of the cabinet. How that works, I don't know.
.

I'd be interested in knowing more about that notion myself. Until you made this comment I was thinking it would reduce the volume of the cabinet.


Physically the volume of the cabinet is reduced, but acoustically, however, it is counter-intuative giving the same effect of a larger cabinet by means of eliminating standing waves and damping/absorbing reflected waves from ricocheting around inside the cab.

Ideally you want air and only air moving in and out of your cabs tuned ports. Also the only sound you hear is coming only from the woofer's cone. Being 'denizens of the the deep' we know low Hz freqs penetrate concrete walls with ease, so you are going to get some sound coming through cab itself, but good damping will minimize that anomaly.

So that's what I think I know. Ha! :lol: Someone that really knows, such as Craig P., will show up to correct me.

Good acoustic insulation reduces or eliminates: mudiness; boominess, and honkiness. At best it will give a tighter and more clearly defined bottom end while also focusing the low mids. Or so I've read. The proof will be in the results of this project. At any rate it can't be a bad thing to judiciously line a bare bass box with some high quality acoustic damping material.


That's interesting to see what comes out of it all. I've never really knew a lot about tinkering this stuff, but here is a good place to learn how and what comes from it.

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