Electrovoice e-v two speakers

Hey Doc.

Have you seen any of the discussions on other boards cautioning about using UltraTouch in speaker cabinets with critical internal dimensions? The discussions have been so few so far that I can't quickly find them for reference, but in short it seems that, unlike FiberFill, rayon, or fiberglass materials, UltraTouch is not air-permeable. And the problem with this, it seems, is that rather than offering the apparent expansion of cabinet volume realized with permeable materials (up to 10% if I remember correctly), UltraTouch actually occupies space, and makes the cabinet volume smaller.

Of course, this supposition does not ignore the superior sound absorption characteristics of UltraTouch, and in situations where absorption is desired, UT is the way to go. But in most cases, when it comes to loudspeaker construction, the purpose of insulation (stuffing, etc.) is not to absorb sound waves (wherein the energy is lost), but to break up their movement within a cabinet, and especially as a deterrent to standing waves.

Or, at least that's the way I understand it. Maybe the really smart folks can chime in here.

GeeDeeEmm

Hey man,

Good catch Hondo! Thank you for stopping by and calling me on that. Why the !@@##$ did I write that ?????? I'm one of the ones that opposes UltraTouch for acoustic and home insulation uses. I've done extensive A/B testing using UltraTouch in 3 Bozak systems. Bozaks are exceptionally touchy when it comes to internal batting, even more than exceptionally touchy. Yes, UltraTouch is dense and simply makes your cabinet that much smaller. It causes your bass response to go flat and dull. I bought 3 or 4 cases of UltraTouch and it eventually all got tossed into the trash. 100% cotton upholstery batting is absolutely wonderful acoustical batting. It's what Bozak finally went to. I've also found it in early Electro-Voice Regency cabinets.

Thank you again for calling me out. It's not cool to have other members read through that and think that Biggles give the UltraTouch a thumbs up.

Biggles
 
Have you seen any of the discussions on other boards cautioning about using UltraTouch in speaker cabinets with critical internal dimensions? The discussions have been so few so far that I can't quickly find them for reference, but in short it seems that, unlike FiberFill, rayon, or fiberglass materials, UltraTouch is not air-permeable. And the problem with this, it seems, is that rather than offering the apparent expansion of cabinet volume realized with permeable materials (up to 10% if I remember correctly), UltraTouch actually occupies space, and makes the cabinet volume smaller.

Not only that, it has no loft, so no absorption and the hard, dense nature reflects sound.

Those attempting to use UltraTouch in a Bozak—infinite baffle cabinet, so absorption is crucial—have experienced a severe loss of bass and poor sound from internal reflections. Removing it and going back to cotton batting restored the bass.

Biggles had a nightmare experience with his Bozak, and he's not the only one.

Of course, this supposition does not ignore the superior sound absorption characteristics of UltraTouch, and in situations where absorption is desired, UT is the way to go.

Those characteristics are a fabrication based upon wishful thinking (recycled denim has a nice appeal to it) that is endlessly recirculated without analysis. Here are the facts. UltraTouch has no absorption. It should NEVER be used in a loudspeaker. Insulation installers don't like it, either. I've seen not one chart showing any benefit to using it, but I have heard numerous anecdotal stories about poor sound.

Cotton batting is the superior absorber, which is why it is used in Bozaks. Everyone who has ripped out the UltraTouch and gone back to the original stuffing has undone the sonic damage.

But in most cases, when it comes to loudspeaker construction, the purpose of insulation (stuffing, etc.) is not to absorb sound waves (wherein the energy is lost), but to break up their movement within a cabinet, and especially as a deterrent to standing waves.

Not exactly. Here's a summary.

The stuffing acts as friction to the backwave. Think of trying to blow through filter material. The tighter the material, the greater the resistance encountered. Most loudspeakers have two resonance peaks: driver and cabinet. The cabinet cannot be neglected. Damping certain portions of the backwave can reduce cabinet resonance which can suck neighboring frequencies into a peak. Hence the "one note" bass phenomenon.

In an acoustic suspension, the backwave compresses air in the cabinet and serves as a restoring force to return the cone to its rest position. The cone is quite floppy. Villchur hand-made his prototype surround to get that floppy behavior. The stuffing in AS disproportionately absorbs the higher frequencies, while leaving the lower ones unmolested, which helps to damp cabinet resonance, while not overly affecting the restoring force and not reducing the bass response.

In an infinite baffle (sealed cabinet) like the Bozak the goal is to absorb the entirety of the backwave, damping out the energy so it cannot put pressure on the cone. This also has the effect of reducing cabinet resonance, since the energy to excite the cabinet is no longer present. The cotton batting not only lines the sides, but forms a curtain dual-chambering the box, much like a muffler, so the backwave passes around the curtain and is then lost.

In a ported or T/L cabinet the goal is absorption as well as to slow certain waves through the pipe. This is why the pipe is stuffed with material like lambswool to add friction.

Jordan's ARU is an aperiodic port which adds acoustic friction.
 
Yes, UltraTouch is dense and simply makes your cabinet that much smaller. It causes your bass response to go flat and dull. I bought 3 or 4 cases of UltraTouch and it eventually all got tossed into the trash. 100% cotton upholstery batting is absolutely wonderful acoustical batting. It's what Bozak finally went to. I've also found it in early Electro-Voice Regency cabinets.

Cotton batting is also natural, non-toxic, inexpensive, easily installed, and carbon capturing. What's not to like?
 
Not to be flippant, but polyester is a synthetic fiber made from petroleum, sometimes other hydrocarbons like coal, in chemical facilities, cotton is a natural fiber made by plants using carbon-dioxide, water, and sunlight. Totally different properties.

Polyester is a solid, i.e. no internal voids, polymer emitted from an orifice in a die, and the shape and diameter of the orifice determines the fiber's diameter, shape, and properties. It can be spun as very thin, highly flexible, and delicate fibers or thick, inflexible, and strong fibers. The former is stuffing for pillows, the latter monofilament for fishing line. The material is highly uniform.

Cotton is grown in fields, combed, and sometimes bleached, and it is thus not a uniform material. The fibers strength depends upon the type of cotton and its growing conditions. This is why Egyptian (aka Pima often tradenamed "Supima", but Pima can be grown in the USA) cotton is superior to American cotton because of differences in the growing season, heat, light, etc.

Polyester fill is a collection of aligned fibers, light and airy, typically used to stuff pillows or insulate winter jackets. It tends to be springy and not compressible.

Cotton batting is a mat comprised of a tangle of fibers. It is far denser than fill, to the point it can be used, as I describe, to make a vertical curtain acting as a muffler. Cotton batting is commonly used in furniture to make shapes and fill out a frame. Unlike the alternative of urethane foam it does not degrade with time and it won't kill you if it burns. (An unlikely event for non-smokers, but the reason why cigarette manufacturers forced fire retardants on Americans by lying about foam furniture which spontaneously combusted.)

So the two materials are very different and are not interchangeable.
 
Adding cotton batting prevents internal reflections. It is a very nice material with which to line a cabinet.

If you're interested, I'd refer you to my discussion about using a flower pot as a midrange bell. Lined inside and outside, it has sloped sides which do not reflect between waves them as do the parallel sides of a speaker cabinet.

The bell prevents cross-modulation of the midrange and woofer, more the woofer to the midrange than the reverse, which greatly cleans up the sound. This is not, of course, not possible in a two-way coaxial driver since the midrange and woofer use the same cone with an internal surround to separate the frequencies. A three-way with a separate cone would pose a number of issues to enclose the midrange portion.

But that's far afield from this discussion.

I'll just say that lining the cabinet reduces reflections which reduces distortion, because a delayed wave is not interfering with the cone which spawned it, or with other cones.
 
Recapped mine. Screwed up the cap order so one didn't get replaced but still tests fine. I'll replace it later. I bought cotton batting to install as well.

Pictures for reference. The boards are the same size, the angle makes one look larger:

IMG_0954.jpg IMG_0956.jpg IMG_0942.jpg
 
The re-cap work looks good, but it's a surprise to see that 5.7uF cap based on the schematic shown on E-V literature. :dunno:


EV-2 schematic.jpg
 
I was surprised to see those.

I replaced them with what is called for it in EV document.

It would be interesting to know if this was a one-off mistake or common practice.
 
I replaced them with what is called for it in EV document.

Yeah, I never know what to do in those instances - - replace with what I find inside or replace with what the schematic shows. So is that third (non-replaced) cap a .5uF?
 
Anyone know how those old caps are constructed? I'm guessing a film cap but they could be NPE. They don't look like oil caps. I've just never seen caps exactly like those.
 
No capacitor expert here, but it would surprise me if the caps in these old E-V speakers were film caps. With the low voltage rating and simple build quality of the caps of this vintage, I suspect they must be electrolytics.
 
Not electrolytics, but early film capacitors from the 1950s. Hence the size.

Shortly after WWII concluded kraft paper was replaced with the German process (confiscated war spoil) of using varnished kraft paper, but film soon made that process obsolete.
 
They're quite nice with my Pilot 245A. Recapping really made a difference.

I feel like I've I'm running a speaker repair shop right now. Recapping these, University RRL-12s, KLH 6s, KLH 20s x 2, open baffle experiment with MarkAudios..just trying to clean up the project line.
 
Very nice speakers. Mine are long gone, but quite memorable.

I do recall most of the connections (to speakers, crossover, Switch on back etc) to need cleaning and so on, but looks like you re-did the crossover so no worries there!
The slide switch always seemed to be a weak point, but cleaning alone may take care of that.

I loved the woofers, they were truly able to do some really deep bass and had that vintage acoustic suspension sound to them.
Only weak point, seemed that high level strong bass would almost overload them, as if they had a really low resonant frequency, but not an issue at normal levels at all.
I loved the sound of the mid/tweeter horn.
Very clear and clean, and somehow made most music and vocals seem more alive.
 
Man I love me some AudioKarma. I picked these up on my way up through rural Mississippi today. Just got to a hotel in TN and wanted to see what they are all about and boom here it all is. The cabs are so nicely done on these speakers, like furniture. I got these cheap thinking I could use the pretty cabs for a Diatone 610 build given I need around 1.6cu ft. Looks like pretty nice speakers to recap, add some dampening and have a listen.
After I get in these I’ll post regarding the 5.7 cap that is labeled on the schematic as a 4.0. Thanks!!
30AC6B3C-5178-44BF-B51C-518690474883.jpeg 503FB785-649B-4FCC-BCA0-68FC9F1CC3AD.jpeg
 
Consider the crossover points for the 16 Ω T-35 family of drivers:
4 µF = 2,487 Hz
5.7 µF = 1,745 Hz

So that's essentially a difference of 2,500 Hz vs 1,800 Hz.

The Electro-Voice compression horns, and I"m specifically thinking of the T-35, experience a nasty resonance peak not much below about 3,500 Hz, so that was generally the minimum crossover point with a first-order crossover. Surprising to see it crossed so much lower. Is a different tweeter/midrange horn being used?

But the schematic shows the woofer crossover is 0.56 mH which doesn't add up, as at 8 Ω that would be 2,274 Hz which matches the 4 µF crossover point, more or less.

I may have made a miscalculation in the math, but don't think so.
 
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