Lowering Peerless 830669 30Hz resonance

[F575M]

I have just purchased four Peerless 830669. Will painting the cone and foam surround with a suitable substance such as the glue used in fitting the gasket, diluted, lower the resonance frequency and help protect the surround?

Cheers,

[walpurgis]

Self defeating to an extent. Painting 'Plastiflex' type materials on cones will add mass and potentially lower resonance, but painting the same on surrounds will make those slghtly stiffer and raise resonance.

I use Allene's Original Tacky Glue for doping. It gives a slightly tacky to touch finish similar that on KEF bextrene cones and Tannoy 'Tannoplas' foam cone surrounds.

Diluting it for use on paper cones is not a good idea in my view. That causes it to soak in rather than provide a coating.

[fatmarley]

The surround should be rubber, so no need to protect it.

To lower fs, I'd add weight to the cone. I'd most likely sit the driver flat on It's magnet and pour some neoprene glue around the outside of the dustcap.

Why do you want to lower fs?

Edit:
Just remembered that there Is an online calculator somewhere. Just put the T/S parameters In and your desired weight and It will show you the changes.

[F575M]

According to Gradient's driver replacement recommendations for the Gradient SW-63 subwoofer, the 830669 has a resonant frequency (30 Hz) that intrudes into the audio band that I will be using [QUAD ESL-63].

Diaphragm Mass Inc. Airload (Mms)74.11g
Maximum Linear Excursion (Xmax)8.3 mm
Surface Area of Cone (Sd)522.8 cm²
Qts 0.54 Fs 31 Hz

[fatmarley]

According to Gradient's driver replacement recommendations for the Gradient SW-63 subwoofer, the 830669 has a resonant frequency (30 Hz) that intrudes into the audio band that I will be using [QUAD ESL-63].

Diaphragm Mass Inc. Airload (Mms)74.11g
Maximum Linear Excursion (Xmax)8.3 mm
Surface Area of Cone (Sd)522.8 cm²
Qts 0.54 Fs 31 Hz

Not sure why an fs of 30hz would "Intrude into the audio band". It has a 9db peak around 2k but that shouldn't be a problem.

For open baffle use 'Qts' is the figure to look at. In a sealed box, you'd look at that figure combined with the frequency response and try to design a box with a flat response. With open baffle, It Isn't any different. For a flat response with that driver a 'Q' of 0.8 to 0.85 looks nice to me.

If you add 90 grams to the cone, you'll get a 'Q' of 0.8, and an fs of 20.8hz but spl will go from 86.8db (1w/1m) to 79.89db.

Added mass calculator - LINK (http://www.mh-audio.nl/tunewoofer.asp)

[F575M]

Thank you so much for the mass calculator link.

Cheers,

Horacio

[F575M]

Is this the glue you that used for doping, does it glide easily?

Cheers,

Horacio

[walpurgis]

No. The clear tacky glue is useless for speakers (handy for other things though).

This is the correct one:

https://s3.postimg.org/bftstzikz/mxcp10614859_1.jpg (https://postimages.org/)

It paints on easily.

[F575M]

Thanks, just one coat is enough?

[walpurgis]

Maybe. Or maybe two.

I use one coat on Tannoy surrounds and have been known to need two on paper cones if they are a bit absorbant like Goodmans felted paper. It's not something I'd do normally though. Better to select a driver that meets requirements to start with really.

By the way. This glue is good for restoring KEF bextrene cone doping that has started lifting off.

[F575M]

"Better to select a driver that meets requirements to start with really". It is not that easy, Gradient used the Peerless 831812, made in Denmark, which has been discontinued years ago. Replacements were the 830500 and later the 831857, both drivers have been discontinued too.

The only choices are the 830845 and the 830669. Generally woofer and especially subwoofer drivers are designed for closed or bass reflex cabinets. Requirements for open baffle are different. Moving mass is one example. In a boxed design a given amount (usually very high in subwoofers) of moving mass is needed in order to get low cutoff frequency. In open baffle designs very low moving mass is of benefit, too high mass produces only harmful vibrations in baffle structure.

Parameters of 830845 look feasible for the SW-63, moving mass is on the high side and the radiating area of 830845 is slightly smaller than that of 830669. The displacement volume is not so much bigger than greater max. excursion indicates. On paper the 830845 should work fine, but Gradient still recommends the 830669. As you probably know, all Peerless drivers, including 830669 and 830845 are made in China, unfortunately, no more in Denmark for years.

Cheers,

Horacio

[fatmarley]

This Is probably the best 12" woofer for open baffle use. Acoustic Elegance Dipole12 (http://aespeakers.com/shop/dipole/dipole12/) - Not cheap though.

[F575M]

John Janowitz of AE tried to convince me to buy the Dipole 12-D8 at $339 a piece. The 12" AE driver is definitely more capable than the Peerless, but is not "higher quality", unless you define "quality" by price alone. Three Peerless will cost less than one AE and handily outperform it. The build quality on the Peerless is as high as the AE, it's just made at giant factories in China, vs hand made by one person here in US.