Ported v sealed

[Kevin Dean]

6 hours ago, JohnDaBass said:

Kevin,

Now you have got the speaker out of the cab, and with your trusty cordless screwdriver to hand 😉, you may as well line the inside with some acoustic furry stuff to dampen the cab even more!

This raises a question , If a cab needs loads of foam does this mean they cocked up the design ?

[Bill Fitzmaurice]

It doesn't need loads of foam, but it should be fully lined, and since it wasn't then yes, they cocked up the design. The bracing is sparse as well.

[Kevin Dean]

11 hours ago, Bill Fitzmaurice said:

It doesn't need loads of foam, but it should be fully lined, and since it wasn't then yes, they cocked up the design. The bracing is sparse as well.

But wouldn't adding foam change the sound  that I already like ?

[Bill Fitzmaurice]

13 hours ago, Kevin Dean said:

Yes I don't think mine needs it

It does. Nearly all speakers do.

My old Barefaced cabs had quite a bit in them though ?

There's the right way to build a cab, and there's the cheap way. BF does it the right way.

[Phil Starr]

Hi Kevin, as a second opinion I'd say that stuffing an enclosure is a complex subject, I still haven't seen a complete mathematical model for this and adding damping materials is done in differing ways in different cabs to achieve a variety of outcomes. Dacron is a very light material and when thin nearly acoustically transparent. There's no doubt that it affects the response of the cab and generally flattens the response by damping resonances but the effects aren't huge unless you achieve reasonably high densities, you'd probably want at least a kilo of stuffing in your cab, keep it away from the ports. As to whether it will improve the sound of your cab I suggest you try it and stick with whatever treatment gives the sound you prefer.

The bracing does look a bit haphazard though.

[Bill Fitzmaurice]

8 minutes ago, Phil Starr said:

 I'd say that stuffing an enclosure is a complex subject, I still haven't seen a complete mathematical model for this

In WinISD 0.7 the effect of both lining and stuffing is seen when you alter Qa from the default value 100, a bare cab, to 50 for a lined cab, 10 for a stuffed cab and 5 for stuffed and compressed. However, as is the case with all WinISD modeling, the results are only fully accurate within the range of pure pistonic function, to roughly 2 octaves above the cab F3. Stuffing, especially when compressed, lowers the cab Q, so the effect on the low frequency response will be seen in the charts. Lining mainly affects the midrange, so it's primary effect is not reflected in the charts. It is seen in measured charts as a significant smoothing of midrange response. 

[Kevin Dean]

Are you saying that it needs damping because it's now ported ?   Ref the bracing , having City & Guilds in Ship building I would normally agree if it was just normal ply or what ever BF use  but it's 15mm marine ply & the whole cab only weights in at 37lbs including the Sica driver & steel grill .

[Kevin Dean]

Right I'm getting some damping & if I don't like te result whould should I send the invoice to ?

[Phil Starr]

19 minutes ago, Bill Fitzmaurice said:

In WinISD 0.7 the effect of both lining and stuffing is seen when you alter Qa from the default value 100, a bare cab, to 50 for a lined cab, 10 for a stuffed cab and 5 for stuffed and compressed. However, as is the case with all WinISD modeling, the results are only fully accurate within the range of pure pistonic function, to roughly 2 octaves above the cab F3. Stuffing, especially when compressed, lowers the cab Q, so the effect on the low frequency response will be seen in the charts. Lining mainly affects the midrange, so it's primary effect is not reflected in the charts. It is seen in measured charts as a significant smoothing of midrange response. 

Hi Bill looks like our posts crossed. there's no doubts about the effects you mention or that the Q of the cab is changed by filling the airspace but I've seen all sorts of claims for 'damping' from the use of high density materials to kill panel resonances through placement to kill standing waves within the cab and so on and so on. We'll both be aware of some of the claims and counter claims about damping materials. Without decent software and test gear it's not an easy thing to be able to say put x amount of stuffing in this part of your cab. Some of the treatments I've seen in commercial cabs leaves the impression that they've done it just so it looks right. 

Kevin, my advice is to find an old polyester filled duvet and experiment with the material in that, Dacron is just the brand name. using the material to hand lets you do a lot of experimenting at little or no cost.

[Bill Fitzmaurice]

1 hour ago, Kevin Dean said:

Are you saying that it needs damping because it's now ported ?   Ref the bracing , having City & Guilds in Ship building I would normally agree if it was just normal ply or what ever BF use  but it's 15mm marine ply & the whole cab only weights in at 37lbs including the Sica driver & steel grill .

It needs damping because if it's not damped waves from the back of the cone reflect off the panels back to the cone, meeting it at various angles of phase, causing peaks and valleys in the speaker response. That's the case with all speakers. This isn't a debatable topic, it's Acoustical Engineering 101, first semester. Un-braced 15mm plywood is insufficient to make the cabinet panels inert. The only difference between Marine plywood and standard grade is the use of waterproof glue. What does matter is the number of plies, which is responsible for stiffness. A single brace connecting the middle of two opposing panels gives the same result as doubling the panel thickness. That's Civil Engineering 101, first semester. Giving the cab designer the benefit of the doubt I'll venture he may have studied acoustical and civil engineering and specified how to correctly build the cab, but the bean counter who over-ruled him in favor of saving a few quid certainly did not.

Edited March 21, 2018 by Bill Fitzmaurice

[Dan Dare]

41 minutes ago, Bill Fitzmaurice said:

It needs damping because if it's not damped waves from the back of the cone reflect off the panels back to the cone, meeting it at various angles of phase, causing peaks and valleys in the speaker response. That's the case with all speakers. This isn't a debatable topic, it's Acoustical Engineering 101, first semester. Un-braced 15mm plywood is insufficient to make the cabinet panels inert. The only difference between Marine plywood and standard grade is the use of waterproof glue. What does matter is the number of plies, which is responsible for stiffness. A single brace connecting the middle of two opposing panels gives the same result as doubling the panel thickness. That's Civil Engineering 101, first semester. Giving the cab designer the benefit of the doubt I'll venture he may have studied acoustical and civil engineering and specified how to correctly build the cab, but the bean counter who over-ruled him in favor of saving a few quid certainly did not.

Bill, do you think it worth lining a cab with those shaped foam acoustic tiles? They're expensive, but is it worth the cost?

Edited March 21, 2018 by Dan Dare

[Kevin Dean]

48 minutes ago, Bill Fitzmaurice said:

It needs damping because if it's not damped waves from the back of the cone reflect off the panels back to the cone, meeting it at various angles of phase, causing peaks and valleys in the speaker response. That's the case with all speakers. This isn't a debatable topic, it's Acoustical Engineering 101, first semester. Un-braced 15mm plywood is insufficient to make the cabinet panels inert. The only difference between Marine plywood and standard grade is the use of waterproof glue. What does matter is the number of plies, which is responsible for stiffness. A single brace connecting the middle of two opposing panels gives the same result as doubling the panel thickness. That's Civil Engineering 101, first semester. Giving the cab designer the benefit of the doubt I'll venture he may have studied acoustical and civil engineering and specified how to correctly build the cab, but the bean counter who over-ruled him in favor of saving a few quid certainly did not.

 

There is quite a bit of difference between Marine ply  not just the glue .

BS 1088

Although a British Standard, it is used by marine plywood manufacturers world wide. The plywood does not have to be of British Manufacture. It is an extensive document which details all characteristics of the plywood.

• The BS 1088 standard is a marine plywood specification that applies to plywood made from untreated tropical hardwood veneers that have a stated level of resistance to fungus growth.
• BS 1088 plywood must use a glue, which has been tested and shown to be highly resistant to weather, micro-organisms, cold and boiling water, steam and dry heat. There are standard BS tests for the glue.
• The Face Veneers must have a solid surface without open defects. Face veneers must be free of knots except "sound pin" knots, (no more than six in any one square foot,) the average of pin knots cannot exceed 2 per square foot over the whole surface of the plywood sheet. The grain in the veneers should be reasonably regular. Edge joints are limited, and end joints are not permitted.
• Core veneers requirements are similar to face veneers except that slits are allowed as long as they are small. Pin knots and edge joints are also allowed. As in face veneer, end joints are forbidden.
• Manufacturing Defects are strictly controlled. Poor bonds, overlaps and pleats, and gaps in faces are not allowed. Gaps may be filled using veneer inserts glued with appropriate adhesive.
• The Moisture content of the plywood must fall between 6% and 14% when it leaves the factory.
• Boards will be equally sanded on both sides.
• Finished size The length or width of a standard sized sheet can not be less than the stated size nor more than 6.3 mm (0.25") larger.
• Squareness -- The lengths of the diagonals of a sheet shall not vary by more than 0.25% of the length of the diagonal.
• Thickness tolerances:
  4 mm +.02/-0.6 ; 6 mm +.04/-0.65 ; 9 mm +.06/-0.75 ; 12 mm +.09/-0.82 15 mm +.1/-0.9 ; 18 mm +.12/-0.98 ; 22 mm +.16/-1.08 ; 25 mm +1.8/-1.16
• Face Veneer thickness -- For any three-ply construction, each veneer sheet will not be any thinner than 1/8 of the total thickness of veneers assembled dry. Multi-Ply Construction-- This applies to boards thicker than 4.8 mm (3/16")
  Each face veneer shall be a minimum of 1.3 mm and not thicker than 3.8 mm. Each core veneer shall be no thicker than 4.8 mm

[Bill Fitzmaurice]

35 minutes ago, Dan Dare said:

Bill, do you think it worth lining a cab with those shaped foam acoustic tiles? They're expensive, but is it worth the cost?

No. Egg crate foam gets its name, and look, from real egg crates, which once were used to line the walls of studios, not to absorb sound waves but to diffuse them. When acoustical foam was invented the look was copied, but ill-advisedly. Foam can't diffuse sound waves, as that requires that they reflect off the foam, which they do not. In terms of absorption flat foam works better, as that is determined by the actual amount of foam. The air contained in the spaces between the egg crate foam dimples doesn't do anything. 

Quote

There is quite a bit of difference between Marine ply  not just the glue

That may be of significance if you're building a boat, but it matters not a whit with a speaker. Baltic (also known as Finnish or Russian) Birch is the preferred material for speakers .

Edited March 21, 2018 by Bill Fitzmaurice

[Kevin Dean]

19 hours ago, Bill Fitzmaurice said:

That may be of significance if you're building a boat, but it matters not a whit with a speaker. Baltic (also known as Finnish or Russian) Birch is the preferred material for speakers .

It makes a difference to  the integrity of the cabinet & how well any screws or pins hold . 

Edited March 22, 2018 by Kevin Dean

[Lozz196]

16 hours ago, Bill Fitzmaurice said:

It needs damping because if it's not damped waves from the back of the cone reflect off the panels back to the cone, meeting it at various angles of phase, causing peaks and valleys in the speaker response. That's the case with all speakers. This isn't a debatable topic, it's Acoustical Engineering 101, first semester. Un-braced 15mm plywood is insufficient to make the cabinet panels inert. The only difference between Marine plywood and standard grade is the use of waterproof glue. What does matter is the number of plies, which is responsible for stiffness. A single brace connecting the middle of two opposing panels gives the same result as doubling the panel thickness. That's Civil Engineering 101, first semester. Giving the cab designer the benefit of the doubt I'll venture he may have studied acoustical and civil engineering and specified how to correctly build the cab, but the bean counter who over-ruled him in favor of saving a few quid certainly did not.

Well that`s helped with my decision to put some damping material in, thanks Bill. I`ll update on this post once I`ve got round to it.

[fleabag]

19 hours ago, Kevin Dean said:

It makes a difference to  the integrity of the cabinet & how well any screws or pins hold . 

The stress and strain in a bass cab is not the same as  the stress and strain endured by a boat. You dont need marine ply for a cab

You're hardly going to notice a difference using non marine ply in a bass cab, unless you accidently punt it into the ocean

[Bill Fitzmaurice]

34 minutes ago, fleabag said:

The stress and strain in a bass cab is not the same as  the stress and strain endured by a boat. You dont need marine ply for a cab

You're hardly going to notice a difference using non marine ply in a bass cab, unless you accidently punt it into the ocean

There's no advantage to using marine plywood other than to the marketing department. But if you're going to argue about whether marine plywood is a better material than Baltic Birch you might want to consider one of the other main industries that uses it: Aircraft construction. The Ashdown marketing department should be bragging about useful features, such as building their cabs from 12mm plywood braced so that it works as well as unbraced 24mm plywood, and fully lining their cabs with damping to deliver better tone. But that would mean they'd also have to have those features.

I'm reminded of when G-K came out with a new line of neo cabs  a few years back, unbraced and unlined. Someone on Talkbass exposed them. G-Ks response, from Bob Gallien himself, was that they had tested the cabs with and without proper bracing and damping and that their testers preferred them unbraced and unlined. Said testers must have been students at Gallaudet University. Numerous owners of the G-Ks added bracing and damping, with about a 95% to 5% consensus that they worked much better after the alteration. Bob Gallien didn't comment again on the subject, but in very short order the cabs got a 'II' designation, this time braced and lined.

[fleabag]

That'll be a big 'ooops' from Bob Gallien then

[Kevin Dean]

Interested to hear that The Foo Fighters have just been A/B ing Ashdown against  Barefaced & chose Ashdown 

[Lozz196]

Yeah, Nate Mendel has used Ashdown for years. I suppose it`s always worth checking out new gear - hey, it`s not like us on here don`t - but appears that there`s something that Ashdown provides which Barefaced doesn`t. Having had cabs from both companies, and currently using Ashdown,  I`d be interested to find out what made NM stick with Ashdown.

[BigRedX]

9 hours ago, Lozz196 said:

 I`d be interested to find out what made NM stick with Ashdown.

Money probably. 

Lets face it whatever amp and cabs he uses it's only for show. In the studio the bass will be DI'd and tracked via some esoteric vintage valve pre-amp and live the sound will be completely FoH PA for the audience and in-ears for the musicians. The choice of amp and cabs makes zero contribution to the sound either recorded or live, so he might as well go for a brand that's going to give him the best deal and keep his name in the eye of other bass players.

While I'm sure that Barefaced would love the publicity that a big name player like Nate Mandel would bring, from what I can see they are already selling cabs as quickly as they can make them and probably don't have the resources to support the extra demands a player like NM will require.

[Ashdown Engineering]

1 hour ago, BigRedX said:

Money probably. 

Lets face it whatever amp and cabs he uses it's only for show. In the studio the bass will be DI'd and tracked via some esoteric vintage valve pre-amp and live the sound will be completely FoH PA for the audience and in-ears for the musicians. The choice of amp and cabs makes zero contribution to the sound either recorded or live, so he might as well go for a brand that's going to give him the best deal and keep his name in the eye of other bass players.

While I'm sure that Barefaced would love the publicity that a big name player like Nate Mandel would bring, from what I can see they are already selling cabs as quickly as they can make them and probably don't have the resources to support the extra demands a player like NM will require.

'Money probably.' - Nope, I think it's fairly safe to say money isn't a huge concern for Nate or any member of the Foo Fighters these days... Unlike many brands today we don't give any free gear to any Artists and Nate pays for his Ashdown gear the same as any other artist. Pic of their payment for Nates last rig attached for you. As you'll see that's money coming in not out...

'In the studio the bass will be DI'd and tracked via some esoteric vintage valve pre-amp' Nope again. Usually it's a mix of Mic and DI from his ABM 900 Head, an old B-15 combo thrown in once in awhile and his BTA 400 as well. It's been this way for the past 15 years.

'The choice of amp and cabs makes zero contribution to the sound either recorded or live' - Really?!?  Wow that's quite a statement, if that's the case then I'm not sure what we're all doing here to be honest....

 As for testing gear vs ours... The Foo's do this every touring cycle, as you can imagine being in one of the biggest bands in the world Nate is constantly getting gear offered to him, they usually get all the gear together from a multitude of brands for a week of testing during their pre production, after this Nate will pick what he wants to use for that tour. Always a nervous few days from our point of view to be honest but touch wood we have always come out on top. Not for reasons of money or support or promotional purposes but because that's what Nate chooses...

 

[Lozz196]

Great response from Ashdown, and what it says to me in a nutshell is that he simply prefers the sound of their gear to other brands. Which is the way it should be imo.

[bartelby]

Gotta give Ashdown their dues, they're great at responding...

 

[Kevin Dean]

is that a Stranglers  rat logo on the bottom of His Rig ? ..;)