Paper-In-Oil Capacitors?? Wooden Horn?

[DerekTheGreat]

Here's the listing for a custom set of UREI 811A's:
https://www.usaudiomart.com/details/...pair-speakers/

In the description the seller states:
"
..Original Time Aligned networks re-capped with NOS Soviet era paper-in-oil capacitors all matched within 1% of factory specs..
"

But why? I've never heard anyone doing this before so if there are any benefits, someone please enlighten me.

Also, what benefit would a fella get from swapping his plastic horn for a custom wooden one? Would those benefits be worth the effort and expense?

Cheers,

Derek

[rusty jefferson]

Derek,

The fellow who makes those horns is a member here with the username eso. There are some thread discussions about these. The grey diffraction foam appears to be a recent addition/update to his wood horns for UREIs.

Your crossovers also were rebuilt with closely matched film capacitors (KZK), and Mills resistors.

[DerekTheGreat]

Ah, that's pretty cool. I guess wood dampens more than plastic? I love the blue, coupled with the bright edges of the woofers the Ureis are fabulous looking.

Oh, that's good to know. Man, you did everything on 'em. Much appreciated, I think I'll be buried next to them when I go.

[eso]

The wood horns came about partially influenced by Yuichi Arai's old web page where he had made a wooden horn for very rare Gauss duplex drivers, and also the realization that I could fairly easily recreate the Urei B series duplex as both the PAS woofers and JBL 2425H drivers were cheap and plentiful. But finding NOS Urei horns in good shape is quite difficult.

The 811As for sale were in rough shape when I found them, both needing recones and one with a broken horn. I too love the look of the classic Urei blue horns. But the wood horns also look very nice and I've now cloned every version from the original 604E & 604-8G, the 604-8K A series, the PAS/JBL B series and JBL C series. All of them are quite different.

I'm also going to throw out there that the wood horns probably have better internal damping than the plastic.

I started messing with the Soviet PIO caps at the recommendation of local Amp Wizard Cy Brenneman. They are quite nice. I've got them in my main Cogent system, and I've also just breadboarded out a TAD TN-1 network for some TAD TSM-1 monitors I'm putting together. The Urei 829 networks in those monitors were produced in Feb, 1981 and were rode hard and put away wet in the Hollywood studio for a long time: they were due for recapping and I happened to be sitting on a decent stock of these NOS Soviet PIO caps...

As far as the charge coupling, there's a whole lot of discussion throughout this forum about it. One nice benefit is that it's possible to match your parts to get much closer to the design values with coupling by carefully matching your pairs.

Thanks for looking!

eso

[DerekTheGreat]

Oh, the speakers in the listing are yours? Pretty neat, I post links quite a bit but I've never had the seller drop by. By the way, what did you use to recreate the foam on the edges and inside of the horn? My fiancée wants to (and says she is going to...) redo the foam on the edge of my horns.

Not related to the thread at all, but would you happen to know where I can get those woofer clamps like yours? My 813C's use the same ones, but one doesn't match. It's only just now starting to bug me.

As for the forum not parsing(?) your paragraphs, there's a setting you have to configure within the "settings" tab. I believe Widget made a post covering it. If I was useful and could find it, I'd link it here.

[Ducatista47]

...I've got them in my main Cogent system,...
eso

Now that must be impressive.

[eso]

Now that must be impressive.

I'm pretty happy with it.



eso

[Mr. Widget]

I'm pretty happy with it.

I see you are not really into vinyl... you should give it a try.


Widget

[mmc8180]

That picture distorts my perception of size - at first glance it appears to be a huge room with cathedral size ceiling heights ... until I focus on the LP albums and amps. If those are indeed vinyl albums.

Maybe they are jewel CD cases?

[RMC]

Dave,

Had no intention at all of correcting you, but rather add more info and showing the OP the 4882 idea might not be the nirvana he was expecting. Honestly i feel bad for the guys who purchase drivers, maybe not consulting here ahead of time, then finding out from someone the cruel reality. Sometimes i try to help them "making it work" with a software modeling for example, however cone travel capability i can't add any to this, simply impossible. Then hinted K151 he also had was better on that aspect. Nevertheless he remains the boss of his own project.

Yeah full specs do help, but did mention post #19 i was looking at the Gauss spec sheet, having most of the Gauss stuff.

RE Perhaps in that application, some audible distortion was acceptable or even welcomed, ala "It just worked".

You're right, in fact Eargle mentions this with regards to MI drivers where some "distortion may indeed be sonically beneficial" (p. 25). Obviously he's talking about sound production drivers, not sound reproduction ones.

Richard

[RMC]

RE post # 20

No material discrepancy or shenanigan in my view.

Not unusual for a large driver to have limited excursion capability, specially when its destined to horn loading as indicated on spec sheet attached (e.g. older 2220A/B/C).

Very high sensitivity (102 db) was priviledged here, not very low bass (btw remember Eargle's phrase i posted recently regarding high efficiency vs LF bandwidth being sacrificed).

At .24 Qts of 4882 is low, one may wonder if the driver would effectively make it down to 30 hz and with lots of output, personnaly i doubt.

As shown Xmax is what it is i think. The .165" (4 mm) is identified as Maximum excursion, which i understand as being Xlim, commonly known as the limit before driver damage. So one might think got another 3 mm in stock, great lets go. Not really. At Xmax (1 mm) you're already at 10% driver distortion (see note 1). Turning up the volume distortion increases even more, continuing such sooner than later the user will be "swimming" in distortion even though the driver hasn't given up mecanically yet...

Now put that in parallel with the fact that horn lovers usually appreciate the device's low distortion.....

Richard

Note 1: John Eargle, Loudspeaker Handbook, 2nd ed, p.64

[grumpy]

Thanks Richard,

Having the actual spec sheet with full info does help!

Still makes me wonder about the Cetec-Gauss 5180 bass guitar cab though.
Looks like a 6ft3, perhaps 55Hz tuned cab (guessing from pics and dimensions), which would be severely displacement limited below 200Hz (vs midband).
Perhaps in that application, some audible distortion was acceptable or even welcomed, ala "It just worked".

Always appreciate good info and learning (sometimes by being corrected)

Best regards,

-dave/grumpy

[RMC]

eso,

RE post # 16

"I've been worried about over excursion. I have a pair of Gauss 4882 driver waiting to be installed which have greater power handling a double the excursion of the K151s."

I don't know where you took the excursion numbers for the JBL K151 and Gauss 4882, but if you compare apples with apples ( i.e. Xmax, linear displacement) then the JBL has 2.5 times the cone travel capability of the Gauss, as per the JBL TS table and Gauss spec sheet.

Gauss 4882: .040" = 1 mm vs JBL K151: 2.54 mm. So your concern might have to be the other way around.

Richard

[grumpy]

Hmm... internet is a funny place... along with old spec copy. JBL had a long published Vas zinger for the 145 woofer.

Also found: 4882A 18" 400W 8 102dB 28Hz 22.0 0.24 0.165" 0

from a different source... .165" is closer to 4mm which makes more sense to me than 1mm for a "400w" 18" driver. Perhaps the .040 was decimeters.
Plug some numbers into a simulation... at 400w (the smaller of the various quoted power handling figures), you'd run out of steam at ~250Hz. reasonably ported OR sealed.
Gauss put these in ~6ft3 ported cabs for bass guitar and even in Karlson enclosures.

So guessing a typo somewhere or something funny like it was -designed- to distort way before Xmech (which seems very unlikely).

An audiomart listing showed the following ... who knows where those numbers came from ... shrug (fwiw... the rest of the TS parameters hung together)

Cetec / Gauss 5181 Bass Guitar Bottom
1 - 4882SX driver
Slot-Loaded
400 Watts RMS
102 db
8 ohms
40-4000 Hz
37 1/4" H x 24" W x 20" D
100 lbs.

Cetec / Gauss 18" Bass Speakers / Woofers / Sub-Woofers / Sound Reinforcement Drivers.
Model #4882SX
8 ohm.
Patent no. 225,069.
Doped suspension surround.
Field-serviceable voice coils.
Develeoped by Bart Bingham and Ed May
Vas [Liters]; Equivalent volume = 430 liters
Qts; Total Q-factor = .2416
Qes; Electrical Q-factor = .27
Qms; Mechanical Q-factor = 2.3
Fs [Hz]; Resonance Frequency = 33 Hz
Approximate minumum power for nominal EQ accuracy = 20 watts rms.
Max Power [W]; Maximum input power = 400 watts rms, 800 watts program, 1600 watts peak.
xmax [mm]; Max excursion from center = 1mm
Moving mass [g]; Weight of moving parts = 107.24 grams
Disp area [m2]; SD, Effective piston area of cone = .119 m^2
Re [ohm]; DC resistance = 6.7 ohms nominal.
Z; Impedence of coil = 8 ohms dynamic, nominal.
L [mH]; Inductance of coil = 1 mH
Bl [Tm]; Magnetic strenth = 23.49 Tm
Weight = 25lbs each.

[eso]

I found a thread discussing the issues with the forum and adjusted my settings but it hasn't helped. I'm trying a different browser right now.

Materials in the wood horns are based on the old Japanese audiophile ideal of all natural materials. The horns are wood, the diffraction buffer on the horn mouth is wool felt, and the sides of the horns are natural chamois. Both the mouth treatment and the sides on the horn really improve clarity and imaging.

The woofer clamps are the last of a quantity that I got from JBL Pro years ago while they were still producing in Northridge.

eso

It looks like switching to Chrome fixes the formatting...