Woofer/Tweeter Installation

firdaus

Member
2002-04-14 12:33 am
A question for all speaker builders:

What material would you use to seal the joints between the driver flanges and the speaker baffle?

I have yet to find someone who covers that to some degree of detail on their websites. I understand that ensuring the edge between the driver flange and the baffle stays airtight is especially critical in vented enclosures.

Looking for some guidance in regards to materials that would be most suited for best results.

Thanks

Firdaus
 

CHRIS8

Disabled Account
2001-12-12 8:47 am
VA, USA
You can use a rope caulk or other similar material, such as Part Express distributes with their drivers. However, this stuff is messy and must be replaced when you ermove the drivers for any reason. The easiest thing to use is closed-cell foam tape. Such as is available from any Wal-Mart or Home Depot. The most common type being a vinyl(grey color) foam available in various thicknesses and widths. The advantage of using the rope caulk type materials is greater isolation(decoupling) from the baffle for mid/midbass drivers, however this is only better slightly, as the fastners compressing the drivdr to the material couple to the enclosure, you can use a highly damped material, such as neoprene in ring/washer form to place between the srewheads and driver frame. Their are ways of decoupling very effectively, but this is not practical unless resonances transmitted to the cabinet are espeicially important to you(they are to me). I have experimented with ways to decouple drivers, but the only ones with a great deal of effectiveness used at least 2 different types of damping, used in thick layers..requiring a ring to mount between the driver and cabinet, having differnt materials on both sides. I have no clue as to what is the most popular diy method for attaching drivers, I really have not paid any attention to that detail. Maybe some others will chime in.

-Chris
 

firdaus

Member
2002-04-14 12:33 am
Does anyone have experience using neoprene ring washers or Cork as a material to make the washers.

Are there any sources anyone knows of, for neoprene sheets and tools to cut washers or do they come precut in differenct sizes.

I am curious as to what namebrand speaker manufacturers have done to solve this problem (never really opened one to see what's used)?

Thanks to you Chris and Scott for your responses.

-firdaus
 
I will 2nd Chris' suggestion of draught exclusion foam tape. Available in many flavours and self-stick.

The idea of decoupling the speaker from the enclosure is one that was tried by KEF and a few other manufacturers, and it results in a bit sloppier bass -- we always found that these enclosures sounded better if the decoupling was removed and the drivers ridgidly attached to the enclosure.

dave
 

CHRIS8

Disabled Account
2001-12-12 8:47 am
VA, USA
"we always found that these enclosures sounded better if the decoupling was removed and the drivers ridgidly attached to the enclosure. "

Indeed, bass band is slightly compromised, that is why I only suggested decoupling for mid/midbass drivers. The signficantly reduced cabinet resoance colorations reduced in midrange are a benefit with effective decoupling. However, in 2 way applications with a mid-bass, then you must compromise.......either taughter bass or cleaner midrange. Ahhhh...choices. :)

Of course, in case of a 3 way---I can not find any reason not to decouple the mid.

-Chris
 

CHRIS8

Disabled Account
2001-12-12 8:47 am
VA, USA
"Are there any sources anyone knows of, for neoprene sheets and tools to cut washers or do they come precut in differenct sizes."

Yes, you can even make gaskets for the driver from about 1/4" thick sheets of soft damped material, such as neoprene. You can get bars, blocks and sheets of various rubber materials(including neoprene) in a variety of densities from:

http://www.mcmaster.com/

For gaskets, about a durometer of 15-20, Shore A is good. For the screw washers, use about a minimum of 40 shore A softness, or the material will keep displacing as you tighten the screw. Do not use a higher durometer, or tighten the screw very much, or the isolation will not be as effective. Use a metal washer between the screw head and rubber. You can also buy small neoprene washers from a hardware store. They come with little metal discs attached, that can be removed. You will need to use 2-3 of them on each screw. I don't remember the exact name of the part, I just look for them and buy them by sight. But, they do specify 'neoprene' on the package. They are about a durometer of 60 or so, a little high, but 3 units per screw is pretty effective. If you choose to cut your washers from sheets, it will be quite a pia. You will need to use leather belt punch to remove the hole for the screw(if you want a clean hole), and cut the OD with an exacto knife.

If you really want to spend the time to do all this, be sure to cut the driver hole deep enough to flush mount the driver, and have the two thick layers of damping, and a ring to seperate them. My last try, I used 2 thick layers of closed vinyl foam..one on the driver hole on cab, and other on the opposite side of seperation ring, and the secondary damping material between driver frame and the other side of seperation ring. But the end result is very effective, with FAR less mechanical vibration transmission to the cabinet. I did not measure with an accelerometer, but in subjective tests, vibration of cabinet, especially the front baffle...was reduced signifanctly. This was on a 1.25" thick front baffle. I do plan to measure the results soon, for a more objective(and accurate) perspective.

-Chris
 

CHRIS8

Disabled Account
2001-12-12 8:47 am
VA, USA
"These with silicone calk would be very effecive in isolating your woofer"

Silicone caulk has very poor damping properties. Though, certainly a better result than direct coupling, but not very effective. Also, quite a mess would be created using this, or more labor fabricating a mold to make a gasket. Plastic fastners: I would recommend against these. I doubt you could even tighten the driver down adequately not to slip after a short period of time when the enclosure is right side up, or get a suitalbe amount of compression to create an air tight seal.

"I would think that vibrations would want to be transfered to the cabinet as fast and easy as possible."

The point is to reduce the amount of vibration transmitted to the enclosure, not delay it. Ideally, one would also mass load the rear of the driver(magnet/frame structure) to some sort of weight/structure, also decoupled from the cabinet in order to provide a path for the higher amplitude resonances now present on the frame/motor of driver. But, in my subjective experiences simply isolating the mid driver still results in significant improvement. Adding damping material(even to cast frames) to the frame is a good idea when decoupling the driver without using some sort of mass/anchoar attached to the frame in addition. I find that standard bitomous and mineral filled vinyl damping sheet material works good on the frame.

Of course, decoupling is not required and could be considered a preference. Just like transient perfect crossovers are a preference. Some like it, some don't. However, decoupling WILL reduce the amplitude of cabinet resonances, overall.

-Chris
 
Not sure why I was thinking about the vinyl screws but a very thin bead of clear silicone put down before a driver is screwed down to the baffle privides a very good stable gasket that can be very thin. It is also fairly easy to get the driver off later.It is also a lot less messy than the putty type caulk strings. I needed to seal a baffle to a box but wanted to be able to get it off so I could change drivers because they needed to be mounted on the inside, so I put a glaze of vasoline down before the silicone so I wouldn't glue it in.
 
Aha! I also need some short advice on mounting my Monacor SPH-60X's in my cabinet. I did a search for "glue drivers baffle screws" and found this thread.

I just put one of them in a cardbord box of 34.2 liters, to test how it sounds.
The highs sound a bit harsh, but I think they just need some running in. Bass starts to roll off at 100Hz in this large box, but it sounds promising. However, I notice the bass is rather directional (as are the highs, but this was to be expected with a whizzer cone:), so there are airleaks in the cardbord box. But I think the screws aren't keeping an airtight seal *around* the SPH-60X. The bass sounds a bit like "open baffle", so I believe that in the final cabinet, screws aren't enough.

So my question is: should I glue the driver (+ screws!) to the final front baffle to keep it airtight?

Thanks for the advice.

A short piece of rope was also mentioned here, maybe that would be better to try first, but what rope? My SPH-212 woofer came with a rubber band, pitty the SPH-60X's didn't.
 
Bill Fitzpatrick said:
silicon rubber

yesterday something crossed my mind: Play-Dough! (I think it's called that way in the U.S.)

It will fill the airgaps, is mouldable and it doesn't hardens (too much), so if I ever need to take the drivers out ...
I think I'll take the type you use to prevent waterleaks while doing DIY plumbing. More neutral color. ;)

The inside of the cabinet will be silicon rubbered with leftovers.

Now if it just would stop raining here in Belgium, then I could start with it ... :rolleyes:
 
Cordraconis said:

yesterday something crossed my mind: Play-Dough! (I think it's called that way in the U.S.)
(...)
Now if it just would stop raining here in Belgium, then I could start with it ... :rolleyes:

We managed to put two cabinets together in those 4 days! yeey! :)

Well, I'm still playing them in as I type, but they reach suprisingly low (F3 of 60Hz, 9 liter cabinet), albeit there is not so much "power" in the bass. It's there, (rather directive it seems)and thats all. Anyhow, this thread is about construction, so here are my experiences about that:

- The baffle cutout was 120mm diameter, and this was confirmed by measuring the driver. The datafile on the internet however said 122mm diameter. The cutouts required more than sanding (grating is the right word?), so 120mm could have been a little too tight after all. After a few tries each driver fitted perfectly.
- I put the play-dough *around* the cutout, not inside since that was already a tight fit. The thickness of the continuous ring was about 1/3 pensil, and that was too much. Like a spaghetty-string would have been better. Now some dough is protruding from under the front plate. More liquid dough could also be used as it required quite some pressure to put the driver in. It seals everything off very effectively, as unscrewing the plate doesn't affect the bass.
- I won't make the duct for the BR out of wood anymore, but from a plastic plumbing tube. Now it's made of two 170mm*31mm, and two 170mm*92mm pieces, glued together to make 20mm*80mm cross section. (the Triplex is 12mm thick). It took one extra day (25% time!) to glue these together, and the swastika-like layout was difficult to put the woodclamps on :cannotbe:.