fe87 mods

[valleyman]

Welll, if you've seen the last OB thread I posted you may know that I want to build one using the alpha 15 and an fe87. They sim very nicely together in a baffle that suits me.

Thing is, once its built, which thankfully wont take long... big fan of the OB built simplicity... I'll want to tune up the fe87.

Basket damping is an obvious one. Closest thing I can find to duct seal here is plumbers putty, but I'm sure its very similar and will do an equally good job. It's cheap too 750g for a couple of pounds.

Puzzlecoat again is an obvious one and mod podge is available here no problem.

I'll probably give Enabling them a go too.

My main question is the dammar coating mod. The main info here related to the fe126/7 and it seems 9 and 17mm in a 6 sectioned ring around the driver works well - at least according to the planet10 peeps who have vastly more experience than I.
This begs the question, where on the fe87 could benefit from this treatment?

Thanks

Edit: forgot one thing. Does anyone know if the 87 has the same dustcap removal problems as the 126/7? I imagine I may want to plug them too...

[chrisb]

Originally posted by valleyman
Welll, if you've seen the last OB thread I posted you may know that I want to build one using the alpha 15 and an fe87. They sim very nicely together in a baffle that suits me.

Thing is, once its built, which thankfully wont take long... big fan of the OB built simplicity... I'll want to tune up the fe87.

Basket damping is an obvious one. Closest thing I can find to duct seal here is plumbers putty, but I'm sure its very similar and will do an equally good job. It's cheap too 750g for a couple of pounds.

I wouldn't recommend plumber's putty in place of duct seal - it'll eventually dry out and likely rattle and flake off- not a good thing inside a speaker cabinet. Dave has samples of thin stamped turntable platters that were treated with Duct-seal over 30yrs ago, and the material is still pliable and sticky - in fact it can be a bit of a dust magnet.

To source duct-seal, try an HVAC supplier. If not successful, then blu-tak or other poster adhesive putties that you'll likely find in a craft shop will work also.

Puzzlecoat again is an obvious one and mod podge is available here no problem.

I'll probably give Enabling them a go too.

My main question is the dammar coating mod. The main info here related to the fe126/7 and it seems 9 and 17mm in a 6 sectioned ring around the driver works well - at least according to the planet10 peeps who have vastly more experience than I.
This begs the question, where on the fe87 could benefit from this treatment?

Thanks

The FF85K certainly benefited from EnAbl treatment on both the main cone an metal "dust cap/tweeter dome".
While sharing the same basket frame and a few other dimensional characteristics, the FE87E is a considerably different driver.


Actually, it would be more appropriate to say that the FF85K is exceptionally different from the standard budget Fostex FE series. Indeed, due to the UDR surround more commonly found in the "Sigma" series, and the huge motor /cone ratio, it's an orphan in the FF series, and quite a stunning little driver within it's limits, but I digress.

Back to topic - there are a couple of methods for determining location of the EnABL blocks (more literally like polka-dots on a driver of this size). I'd suggest you contact Dave directly for some guidance. On drivers of these smaller dimensions, care needs be taken in terms of the type and total mass of material applied to the moving diaphram/cone.

Edit: forgot one thing. Does anyone know if the 87 has the same dustcap removal problems as the 126/7? I imagine I may want to plug them too...

Don't know that, and to be honest, I'm not so sure that you wouldn't be trading away more than you'd gain, particularly with the full EnABL treatment applied to the cap as well (like I said, those particularly will be pretty tiny dots). The geometry of the new center caps on the FE87 / 126 / 127 are quite different, and I suspect contribute to their HF performance. We like to think of the FF85K as a cone tweeter that can be crossed over lower than normal (i.e. 200-300Hz)

[valleyman]

Thanks chris

The plumber's putty I found maintains that it will remain "permanently flexible" and I have seen blu tack in sunlight dry out in a year so I'm not that keen to use it.

I'm 99% certain that the duct seal dave uses simply isnt available here in the UK.

On the plus side, since these drivers will be mounted in an OB, I'll be able to very easily see if there are any problems with the putty drying out.

I probably will contact dave directly about Enabling these, but theres quite a lot of info on it around already, and tbh I expect it wont be long before he chimes in here anyway.

Out of interest, your post seemed to indicate that the FF85k is flat out a better driver than the FE87. Do you believe this to be the case? My basis for choosing the FE87 was the higher Qts and the lack of rising response above 10kHz which tends to bother me.

The other point I was really referring to was the dampening of cone vibration modes. This is achieve on the fe126/7 with the damar coating in 6 sections around the cone 9 and 17mm from the outside edge of the cone. I was wondering if there was wisdom as to where similar treatment should be applied to this smaller cone.

Thanks

[chrisb]

Originally posted by valleyman
Thanks chris

The plumber's putty I found maintains that it will remain "permanently flexible" and I have seen blu tack in sunlight dry out in a year so I'm not that keen to use it.

I'm 99% certain that the duct seal dave uses simply isnt available here in the UK.

On the plus side, since these drivers will be mounted in an OB, I'll be able to very easily see if there are any problems with the putty drying out.

all fair enough

I probably will contact dave directly about Enabling these, but theres quite a lot of info on it around already, and tbh I expect it wont be long before he chimes in here anyway.

yup, probably a matter of only a few hours

Out of interest, your post seemed to indicate that the FF85k is flat out a better driver than the FE87. Do you believe this to be the case?

I haven't heard either the FE87E, (or it's "fraternal twin" the FE83E) so no opinion on that - but I can say that if you're thinking of OB, that's the first quick listen we gave to the FF85K before Dave spent the time on refining the EnABL treatment.

Once treated, we've had great response to their performance in a "micro" sized enclosure, with powered woofers, XO's around 200 or so IIRC.

My basis for choosing the FE87 was the higher Qts and the lack of rising response above 10kHz which tends to bother me
The other point I was really referring to was the dampening of cone vibration modes. This is achieve on the fe126/7 with the damar coating in 6 sections around the cone 9 and 17mm from the outside edge of the cone. I was wondering if there was wisdom as to where similar treatment should be applied to this smaller cone.

Thanks

Dave can best describe how the damar pattern was derived, which attentive readers would remember that we'd been avidly promoting long before Bud's original post proferring the EnABL technology to the DIY community. Indeed there doesn't even appear to be consensus among all builders that the FE126/7 have the specific resonance issues that the damar treatment addresses, independently of the EnABL.

It should be pointed out that after receiving the first pair of FE127s treated by Bud, we did more than a few weeks of comparative listening to various combinations of EnABL alone, and this earlier treatment to reach our current conclusion - that as regards the two drivers in question (FE126/7), the two treatments are definitely synergetic.

To the best of my limited knowledge, there has been no published "wisdom*" on this subject regarding the smaller Fostex drivers in question.

*totally non sequitur, but every time I encounter that word, I flash back to the halcyon days of my twenty-something, and the timeless brilliance of FZ:


Information is not knowledge
Knowledge is not wisdom
Wisdom is not truth
Truth is not beauty
Beauty is not love
Love is not music
Music is THE BEST...

Wisdom is the domain of the Wis
(which is extinct).



can you image the fun he'd have had during the past 8yrs?


oh, yes the hounz did enhale

[valleyman]

Dave actually attributes the exact position of the damar mod to MarkMcK (http://fullrangedriver.com/forum/viewtopic.php?id=535) though it is long before my time I have no doubt you guys came up with the damar treatment first and Mark's comments just helped to fine tune it. I'd be interested in how those figures of 9 and 17mm were reached - I should read that thread Dave references.

Failing finding any scientific basis for how they were derived or if it is beyond my scope to do the calculations I will likely just downsize the 126/127 positions for the smaller driver. Can't imagine it would do much harm and I quite like the look too!

[planet10]

The damar mod was our attempt to quell the resonances that Mark found... he never did divulge how he fived them.

Since no resonance studies have been done on the smaller drivers, we wouldn't know where to work so best to do nothing. Light puzzlecoat on the cone, and EnABL. The newest non-whizzer cone drivers don't seem to benefit much if any vrs an EnaBLed dome -- after 40 years of plugging away art the same basic cone/dome Fostex dramatically revised the e series. The older Fostexes do benefit. Phase plugs for the latest FE83/97/103/107.126/127 are mainly appropriate to replace poked in dust-caps (althou it seems it might be worth playing with a concave dome if yours do get finger-poked.

dave

[REC1]

I have Martins OBs with the FE87. very good performance considering the simplicity. Took some dinking with position in the room but will get down to the low 50s if positioned correctly.

All i can state is they do what i want.

Try some insulation pipe wrap or a water snake with a slit around the edges, this lowers the recieved edge diffraction greatly.

ron

[sreten]

Originally posted by chrisb


I wouldn't recommend plumber's putty in place of duct seal
- it'll eventually dry out and likely rattle and flake off -

D

Hi, i think you have your glaziers and plumbers confused, /sreten.

http://www.geocel.co.uk/dynpdfs/250.pdf : looks like duct seal to me

[valleyman]

Thanks all. I have the benefit of using my computer as the only source so I can actually "fix" a lot of speakers quite easily by using th iTunes EQ. Much as I think iTunes is a terrible piece of software (for windows anyway), the interface is great and surprisingly the EQ is very good. Most other software I've tried immediately introduces horrible distortion when you try to use the equaliser, but iTunes does very well. I'm sure with the EQ I can have them playing well into the 40s without issue.

I'm glad in a way that I dont have to remove the dust caps. Saves my drivers their greatest risk...

I'm still uncertain about the damar to control the cone resonances... as I said, I like the look, and you apply it in fairly thick swathes so I might be tempted to "guess" at where they should go and give it a try hoping the swathes will get the key areas.

I have my doubts about how much the pipe around the edges trick would actually help with diffraction. To my knowledge much greater rounding is required to have a significant impact on edge diffraction, but in fairness, you've tried it and I haven't so I certainly won't rule out what you say. The point is moot anyway as aesthetics pretty much put it out of the question... I dont really want that around the edge of my speakers. They will see my roundover bit though, but thats really just an aesthetic thing again.

It does bring an idea to mind though... I wont be trying it as the baffle is only an inch wider than the 15" driver I'm using, but a pair of OBs using several sheets of flexi-ply stuck together on a gently curving frame could work quite nicely. I'd be surprised if someone hasnt done it before though..

[REC1]

have my doubts about how much the pipe around the edges trick would actually help with diffraction. To my knowledge much greater rounding is required to have a significant impact on edge diffraction

Its not the radius of the material, its the sound absorbation of the diffracted energy from the sharp edges.

ron