RF-7, Tilt for Lower Mids

[Erik Mandaville]

Leo:

If you see this: I've got the back panels off, and poly sections cut to fit rear and top, bottom, and side panels (minus area of crossover and input terminals). I bought 2" rolled batting, which I tore in half for a 1" thickness, and so the surface exposed surface would be irregular as opposed to completely flat. This may be all that's needed, but I was wondering if you used loose batting or long fiber wool, and if you also treated the side panels. This sealed cabinet is just a little different, but I was curious about what you found worked best.

Years ago, wall damping materials for my speaker projects included foam-backed carpet, roofing felt, and so forth, and then I would just lightly fill with Acousta-Stuff of cheaper batting material.

I'm just going to staple the pieces with a couple of very shallow staples to see how it sounds.

Erik

[leok]

I used "AcoustaStuff" which is a plastic, long fiber material. I simply filled spaces with the material. It is light and maintains its volume well.

Leo

[colterphoto1]

uh, for time alighment, wouldn't you have to tilt a LS FORWARD? the length of the bass horn is longer than the mid horn, unless of course you were trying to line up the mid and tweeter, in case it'd have to be tilted very faaarrrrr back.....

[Erik Mandaville]

Leo:

Thanks.

Erik

[NOSValves]

The difference this made last year at AK fest was not subtle at all.

[mike stehr]

"If you see this: I've got the back panels off, and poly sections cut to fit rear and top, bottom, and side panels (minus area of crossover and input terminals). I bought 2" rolled batting, which I tore in half for a 1" thickness, and so the surface exposed surface would be irregular as opposed to completely flat. This may be all that's needed, but I was wondering if you used loose batting or long fiber wool, and if you also treated the side panels. This sealed cabinet is just a little different, but I was curious about what you found worked best."

Erik,

I think to cure reflections in the sides and back of a cabinet, wool or a heavy foam, carpet pad, or dynamat would be the best thing to use over polyfil.

To use polyfil to fake the cabinet into thinking it's a larger size, you just stuff the cabinet with loose polyfil. I guess the polyfil batting wadded up a bit would work as well. I used to know the ratio of the amount of polyfil per cubic foot. I want to say one pound of polyfil per foot, but I don't think that is right.

One way to do it is hook a small battery (D or C cell) to the woofer.

Hook the woofer up to the battery, listen to the thump. Throw in some polyfil, hook up the battery and listen to the thump again. When the thump works it's way down to a mild thud from adding the polyfil, you know things are well damped. I think the stuff works in a resistive manner. With a ported enclosure, you don't want the polyfil to block the ports.

You never know, it may gives the Heresey's a little more depth on the bottom end, or maybe tame a peak at around 60, 70 Hz. (If the Heresey suffers from that issue...) It may make things worse, but all you have to do is pull the polyfil back out.

I use around 2 pounds of polyfil in my homemade 3.5 foot enclosures, which are tuned to 35 Hz with two ports. I use a cheap Japanese 10" woofer with a fs of 55-60 Hz.

Strong bass all the way down to 35 Hz, some lower frequencies almost seem noticed as well. Strange as it may seem, the bass is as strong as a Cornwall's 15" woofer. But they just won't handle as much power.

I've pondered about throwing some polyfil in a Cornwall, I'm curious to see how that would fare. But I haven't really wanted to pony up for the polyfil.... ; )

It's worth a try.......

[maxg]

"You never know, it may gives the Heresey's a little more depth on the bottom end, or maybe tame a peak at around 60, 70 Hz. (If the Heresey suffers from that issue...) It may make things worse, but all you have to do is pull the polyfil back out. "

IME Heresy's do suffer such a peak - but I think it is actually deliberate. Having a peak there gives the illusion of having more (as in deeper) bass than reality and I have seen it in many smaller speakers.

Frankly it works rather well - until such time as you compare it with real bass and then the difference is obvious.

As for the whole time-alignment thing I guess it is going to be much dependent on the height of the listener's ear.

I do think you can get quite carried away with this. We are talking about fairly small differences and I would guess the impact of the average listening room would be greater than any change imparted by exact alignment of similar drivers to reach the ear simultaneously.

Further, making such changes will also impact the interactions of the output of the speaker drivers with the room itself - changing the reflection times for sound waves coming from the floor, for example. I would suspect that these are actually a greater source of perceived impact on the sound than the measured equidistant woofers.

[jbsl]

I made 6 inch risers for my La Scalas and to me it sounds much better.

[Erik Mandaville]

Mike:

All of that is helpful information -- thanks. The panel sections I cut were just a starting point to get a feel for the direction the resulting sound might take, as well as to provide a surface with greater surface tension than smooth flat wood to hopefully prevent the light fill I'll put in afterwards from settling. If I like the result, I will probably remove the drivers and do the entire process more thoroughly, including some damping of the cabinet panels. Except for our rear-loaded horns, which are left intentionally very smooth and fill-free inside, all of the speakers I've made, both sealed and ported, used both side wall dampening treatment as well as either long fiber natural wool of Acoustistuff for the rest.

There is a peak that occasonally jumps out which, by design or not, can be distracting.

Max: Time alignment of drivers is a fairly common aspect of speaker design, and an area that can actually become significant. It does not have so much to do with the height of the drivers (such as having a tweeter relatively on axis with the ear at the listening position) as it does with equalizing the distance of the voice coils of the drivers from the listening position. Some companies will accomplish this by sloping the baffle backward (as seen in the first picture I posted of some old speakers I made), or by moving the woofer forward - which, depending on how it's done, can possibly cause some other concerns, such as diffraction.

And sure, one can get carried away with any aspect of this hobby; however, in the grand scheme of things, I would submit there are worse things with which one might get carried away. As I've mentioned in this past, I'm curious about how things work and experimenting with new approaches that, subtle or not, may ultimately make for a sonic character that best fits our listening preferences. Surely this isn't too different from exploring different capacitors types and brands to find what sounds best (?). Fortunately, since I am the one conducting the experiment, I will know what to do to put things back to how they were if I don't like what I hear. If I don't try it, I will never know, right?

Mike: I like that battery-thump-test idea. I've never done that before, only used the same setup to test for proper woofer polarity. Good information there.

Erik

[Erik Mandaville]

Re: Time alignment -- this is not really what Leo was referring to with his tilting of the cabinets; it was my incorrect interpretation, and compared it to the sloping front baffle of some speakers I once made.

Erik

[leok]

I guess putting some angle back on most speakers, even if the object isn't to time align identical drivers, helps project the sound into the listening space and not directly into a piece of furniture.

Time alignment of different drivers is way too complex for me. I would expect the phases of adjacent drivers would want to match in the crossover region where they are both most likely to be at some time delay or advance offset from what they are at midband. How does one get them to crossover in phase and stay that way at midband? Then there's the lengths of the horns adding different delays.

I have to settle for getting the two identical RF-7 cones lined up, maybe project the Chorus-II up a bit and let Klipsch or Al K. time align the different sections.

Leo

[Erik Mandaville]

"...helps project the sound into the listening space and not directly into a piece of furniture."

I've found that. We got some aftermarket 8" risers with our Heresies that tilt the cabinets backward. Where I have to place the left channel speaker, the extra height (as JBL mentioned) and tilt (in the picture Craig provided) help open things up. If some mechanical time alignment is taking place at the same time as a result, I suppose that's a positive added benefit.

It's great fun to experiment, and if the result is better sound (even if it's an imagined improvement -- psychology plays into this, IMO) than that's okay.

We all tend to tweak, whether with new cartridges, capacitors, fill vs no fill in cabinets, cable and wire, new amps-or-preamps-or-sources. Whether or not that effort or change is valid or otherwise seems to me to be rather up to the person doing the tweaking....

Erik

[maxg]

Erik,

I think we are on the same page. I am not knocking the tilting of a speaker in any direction - merely questioning what is the actual cause of any perceived benefit.

My limited experience to date indicates that the interaction of the speaker and room is pretty much key to the whole listening experience. Changes in the orientation of a speaker will certainly be expected to affect that interaction.

Just as a matter of reference I used to run my own speakers tilted upwards. Later I put the speakers on legs, raising them significantly, and kept them flat. The latter is the better sound to my ears and just about everyone else who heard the speakers both ways.

Now I could angle them back as well - frankly I just havent got around to trying it out. As the speaker drivers are now well away from floors / furniture W.H.Y. any sonic difference should be due, in the main, to time alignment.

I think.....[:^)]

[Erik Mandaville]

Leo:

I didn't intend for this thread to take on a different direction, but.....

"Let me know how the fill works out. I would expect it to have a significant impact (good or bad). "

I'm listening to one of my reference CDs as I write this, and the impact IS significant. Without a doubt something I prefer to no fill at all. I picked out some music that is both really well recorded (IMO), and has some decent bass and good drumming. This is Bill Bruford's 'Earth Works' album called A part and yet apart. Highly energized modern acoustic jazz, and what struck me immeidiately was a much improved and greater sense of overall presence (music seems louder than what I remember with the same input level-- whether that's actually the case I'm not sure). Next up, and the genre where the bulk of my listening lies, is Georg Phillip Telemann.

This is just with the really cheap poly fill I mentioned before. In any event, what I particularly like is the impression of many more upright string bass notes. They were there before, but seemingly not nearly as distinct and clear. I'm using words like 'seemingly' because I can't say for sure -- my acoustic memory is probably not so great -- but this really struck me! I've made changes to designs in the past that sounded really dull, lifeless, but this is one I absolutely want to keep, and possibly improve on with fill designed for the purpose, such as Acoustistuff or natural long fiber wool. I have a little wool leftover from another project, but not nearly enough. This cheap fill is leaving lots of little fibers inside, but that can be vacuumed out.

Anyway, it was when you posted what you did about your own experiment that planted the seed here, and I'm glad you mentioned it.

Max: I have spent sleepless nights wondering about possible circuit ideas, changes, modifications, and I would say that might be an example of the hobby taking up too much of one's thinking, particularly when the next day is a workday! For a small two channel only system, though, this Heresy/modded Moondog/6SN7 preamp/now antique Denon CDP arrangement is sounding pretty amazing. I had been using the Moth amp, but for whatever reason (possibly different gain characteristics) the Moondogs and Heresies are very happy together. The Moth 2A3 amp (I know, all 3 or 4 watts of it[]) is on the other hand doing very well with the Klipschorns in our surround music/HT system. What I think might be even better is another little Teac combined with a good tube linestage. That's something I was also thinking about last night with my eyes wide open, but I'm at home all week, so I didn't mind losing some sleep over a really fun hobby.

Erik

[mike stehr]

"This cheap fill is leaving lots of little fibers inside, but that can be vacuumed out."

I've played with quite a bit of the polyfil (the ex-girlfriend used to use it for sewing projects), and I've never seen or had the stuff break down like you mention in my cabinets. Or with her projects.

Even after the stuff been sitting in a cabinet for a significant amount of time, like years). I'd invest in some better quality polyfil, or material suited for the task like you mention. I'd hate to think of broken-down fill in a voice coil gap.

Try a heresy stuffed with the fill, and one without. Listen and swap back and forth on the fly. Or run both with polyfil for a week or so, then pull it and listen.

IMHO, the Heresy has 12" woofer jammed in too small of a sealed box. I maybe thought the polyfil would help some.

[Erik Mandaville]

There were tiny pieces of fiber all over the woofer cone until I vacuumed them out. Maybe it was from adjusting the material, or something. In any case, not a problem that can't be solved easily enough.

This is an excellent modification as far as I'm concerned, and I am surprised at how loud (clean loud) Heresies can actually get with a low power amplifier.

Erik

[Jay481985]

hey guys, I didn't read all the last 2-3 pages but question, the cone is closer to your ear because the horn is not on the same verticle plane so wouldn't that have compensated?

[wuzzzer]

I tried this a couple nights ago with my Forte IIs. I put 3 magazines of equal thickness under the front of each speaker. I haven't had a chance to listen to them without my wife here so they've been pretty quiet so far. It will be interesting to see if there is a noticeable difference in sound.

[doctorcilantro]

I'm wondering if the perceived combination of positive effects could be due, in part, to the decoupling of the speaker from the floor.

Whenever I used to make my kick drum nice and high on its legs, away from the floor, it would resonate much more and sound more "efficient" and tonally pure, as opposed to the deading effect when coupled to the floor. Of course, then you may add a touch of packing just like with a speaker to give it a little sumpthin.

I may check this out with my RF-7s this winter by simply removing the rear spikes and leaving the front ones on.

DC
Craig - those VRDs are looking spicy....that cherry finish.....