Paul S wrote:

I took a couple of pictures, but I can't figure out how to upload them, just yet.

Paul S wrote:

I took out the phase plug, and the gap is truly tiny!

Paul S wrote:

The cone surround is soft foam. I presently high-pass my OB-mounted units 1st order at 400 Hz. Frank lists the Qts as .1048 (!)

Petar, thanks for the pic posting link (which I've read over and over), but my problem posting pictures is my ancient browser, so that's another task. Again, there's really not much of what one would like to see that I can show, short of disassembly, as you will see for yourself, eventually.

I am not sure about the double coil windings. My guess is, "optimized" single winding, since Frank's aim was to keep it as light as possible, and he would be all over mutual inductance and that sort of thing, as part of his intellectual excercise. And, clearly, he did not use the most powerful magnet possible but sought to "optimize" that, too. As a point of interest, Frank refers to the bonding of the former to the cone as "an elaborate interlaced bandline" using "adhesives specifically selected for their low mass and exceptional bond strength". He also says the coil is a "perfect lay" Aluminum on a .003" bobbin, and he cites power handling at 55 W.

I have played around with two different Lowthers, but this is my first experience with the Reps.  None of these drivers move much, at least not the way I've used them. I am aware of conventional wisdom regarding Qts and the usual applications. While I would not choose an OB driver - including this one - because it had soft Qts, neither will I give up on it for that reason, at least not until I get the stupid spike tamed so I can hear what else it can do with my ears rather than my eyes. I suppose I could dope the foam (being careful not to degrade it chemically...), come to that.  But I am not there yet, and anything like this will come as a direct response to listening rather than a preemptive strike based on supposed TS numbers.

Again, unless one of us is siezed with inspiration in the meantime, I will at least try the (damned) notch filter, if only out of curiosity. Any suggestions for [foam] dope? I used to use a mix of good Damar varnish and highly-filtered beeswax that never completly set up; but if I ever settled on an exact recipe, I no longer remember it. In any case, I won't change the mechanics of the driver without having aurally targeted reasons to do so, and I would start with things I could un-do.

Best regards,
Paul S

Paul, the problem could be unsolvable if this peak is due to cone geometry. Flat cones in general behave very good up to a certain frequency, but they have strong standing wave mode (its magnitude depends of the internal damping in the cone) above that frequency which is dependent of the cone size and it’s thickness. If your Reps driver uses the same paper as the original Lowthers – you are in trouble (I wish I was kidding, but I’m not). It is very thin and weak and it can’t resist the fast acceleration of the voice coil above 2-3kHz. The ribs of the cone improve the situation, but not much. I took a photo of a friend’s lowther – is the main cone the same like yours?

Best regards,

Haralanov

Petar, I believe I remember reading somewhere that Reps sources his cones from the German firm, AER, or their OEM, whoever that is.  Perhaps you know of AER's Lowther-alike drivers?   However, the Reps cone is still very similar to the Lowther - different treatment, but similar, with very similar ribs, and also very thin paper; perhaps thinner than the Lowther.  I can't say for sure, but the Reps' "too-soft" surround might make movement easier on the paper than it is for the DX4.  It sounds as if this is the case.  Since my Reps are without whizzers, straight comparisons with my Lowther DX4s are not really possible, but the Reps I have sound generally more "calm" than the DX4s.  Of course, the DX4s also suffer from whizzer cone break-up ("roll" notwithstanding), which the Reps I have (obviously...) do not...

And now that I have had more time to reflect on it, I suppose it is likely that the Reps' voice coil has at least 2 layers - hence the "perfect lay" reference in Reps' flyer.

The thing is, one can't avoid hearing the Reps' spike.  Although I admit I have not actually measured it for myself yet, the very sharp 2.1k Hz notch filter I just put in improved the situation considerably, so I must have gotten close.  I am not sure about problems in the "drum range", but I presently think it has as much to do with the room, etc. as it does with the Reps.

As you know, the problem with all the thin paper drivers is the cone break-up that effectively "converts" the pure tones into mostly higher frequencies.

And the problem with the heavier paper drivers is that they are so slow and "homoginized" by comparison to the  lighter cones.

Based on past experience, I know I prefer a nice 10" driver as the aural pivot for my speakers.  But I have no idea where to turn for a 10" driver today.  I have thought about trying the Supervox 285 GMF (obviously, it's larger than 10"...), but that would force me to x/o in the voice range.  I am not sure if I would change the fundamental pitch much with Supravox's 215.  I also had old Peerless 8" drivers that were "nice", but I always preferred the 10", in context.  I can say from memory that the Lowther is much faster than any "comparable" Peerless!

All I want is wide-range drivers as fast as a Lowther DX4 or Reps R1 with the tone of the old (late 70s/early 80s) 10" Peerless!  Is that asking too much?

Best regards,
Paul S

Paul S wrote:

All I want is wide-range drivers as fast as a Lowther DX4

Paul S wrote:

All I want is wide-range drivers as fast as .... with the tone of the .... Is that asking too much?

http://community.webshots.com/photo/fullsize/2554912450048111837MRntIi

Best regards from Europe,

Haralanov

Paul S wrote:

I remembered a host of "old" drivers from my past (not old at the time...) that, if memory serves, sounded rather muffled and slow, with humped response

Paul S wrote:

Where does one find data sheets (response and impedance curves, efficiency ratings, etc.) for this stuff, to at least be able to separate the wheat from the chaff ahead of time?

Paul S wrote:

It seems overwhelming to just round up stuff and install everything if it is not necessary.

Paul S wrote:

I also went back to look at the pictures you posted, and those drivers look rather like some of the old radio speakers, most of which I remember as soft, with a decidedly humped response.

Paul S wrote:

Also, many of these drivers only rate 5 Watts, and/or they are at or under 4 Ohms, and most are closer to 90 dB than 98 dB.

Paul S wrote:

But even the 4" drivers of that time did not really go all that high, or they did not do it well, as I recall, so even with a 4" mid there would remain the need for a real tweeter.

Paul S wrote:

Looking at the "ragged tweeter" you shared, I am curious how you keep the cone/coil centered in the gap.  You say the cone is now 55mm.  What size did it start out?

Paul S wrote:

Now that I have thought about it, I can also recall the noisy frames on many of those drivers.  I guess that's something else to deal with...

The main "technique" I use in "problem solving" involves a sort of Hegelian turning and re-turning of/to the object of attention (or, my perspective...) to get as many "views" of the object as possible.  This sort of reflection has recently brought to mind some potentially useful memories/observations:

For all the problems of the old radio speakers, some of that old paper was very nice tonally and very stable and well-damped at certain frequencies.  Cone shape is also a factor, and the straight-faced "piston" is prone to some avoidable troubles by concept/design. It is all well and good to "control break-up"... in theory; in practice, it may work at least as well to simply avoid break-up by limiting stress, and/or even to"distribute" break-up over the cone and/or operating range.

For all the fact that Alnico tends to pull tone upwards as the demands on it are increased, yet it is quite "calm" (like silver wire...) in a way that might be put to good use.

My objective is not to use a full-range or wide-range driver but to wind up with acceptable performance from the system.  I know what I want, and I am not stuck on how to get it.

Recently, looking at and thinking about what real drivers I am aware of actually do, I have been "modeling"  3 drivers to fill in for my present 8" Lowther or Reps: A 10"; a 4"; a paper tweeter that can meet my ribbon in a good place.  I do not know it yet, but I suspect a "good" 4" will probably not go from, say,  2k to 12k.  If it can, then I am always happy to eliminate a driver/crossover!

If I "remember the response curves" of the old drivers correctly, the "hump" is probably at or close to the optimum portion of the coil/gap stroke.  If so, this would make my "objective" to somehow limit each driver to what it "prefers" to do, in the first place.  Or, a given driver might be refitted and/or "trained" to operate in its optimal range...

But the starting point is tough (impossible...) without some sort of mental "inventory" of available drivers.  Yes, it's too bad that the "market" is controlled by name-worshiping clowns with too much free time and money to spend on their fetishes.  So, to avoid stimulating these Bozos, perhaps you can say in more-or-less generic terms what sort of  * rough *  relationships you have worked out with respect to cone diameter, frequency response, SPL, gap and motor size/force?  In my case, I would not try for less than about 150 - 200 Hz from my 10" "pivot" driver, and I am not stuck on pushing it higher than, say 2 - 3 k; wherever the 4" does better.  The old-ish "theater" speakers mostly have rather large magnet/motors, regardless of cone size; the old "radio" speakers have relatively smaller magnet/motors, and narrower voice coils, regardless of cone size.  I do need over 100 dB SPL in my room with orchestras, that's for sure.  Basically, how does one "proportionally" relate the appearance of the driver to its purpose?

Petar, it has been some time since I have "spoken" of this stuff in this way with someone who basically takes the words out of my mouth and says/shows me things I "already knew", even though it is certainly "new" to me in terms of the rote, practical applications you present.  And so, based on your rather guarded/coded revelations so far, I suppose you re-wind at least some of your coils?

I guess I have to do what I have to do; but, as I have mentioned before, I am a VERY reluctant DIY guy!  I am still after results, not process, itself.

Best regards,
Paul S

Paul S wrote:

Again, I am NOT a collector - at all.  I am only in it for the music

Paul S wrote:

If there is really no "source" for the "completed" drivers I need, I suppose I am ready to go the DIY/mod route with the "selected" drivers, themselves, too, just as I have done with most of the rest of my gear, in order to wind up with sound I find acceptable.

It is one thing to swap caps in a pre-amp, or ICs; it is another thing entirely to swap transducers.  Nothing brings change like a speaker, and it may be that nothing is less understood in terms of the pure sound that is - ultimately - the only thing that defines it.

It's been a long time since I thought I could just buy a better speaker system, and I did not start out thinking I would be "done" in 6 months, or anything like that.  Still, now that I have gotten into this "natural sound" thing, it is just as well that I held my expectations in check, because it looks like the months will be piling up while I develop the truly useful working knowledge I will need to continue, based on my current level of sonic and musical "expectations".  Sure, everyone else already gets it, but I never stop being surprised by how profoundly ignorant I am about the recurring relationships between what I will call for now "the various interactive elements" of the speaker system.  No matter what we hear about these things, the actual hearing and systematizing of sonic results for ones self is another matter, entirely.

To state the obvious: If to truly begin to understand them, just like any other component, each driver must be singled out, analyzed and developed on its own and then re-evaluated in the context of a system that is, per force, changing.  I have already gone through a pile of candidates that I have heard about, and I have kept some stuff for further development.  "Development" might mean exact placement with or near other drivers, or it might mean keeping only one part of the driver to build another one with.  If I were't married, I'm afraid my house might be full of speakers and speaker PARTS, since there are plenty enough lying around, as it is.

One thing I have learned so far is that while there is some truth to some rumors about some drivers, none I have heard so far is anything like a ready-to-go, stand-alone unit.  If I can be objective about this, ALL the drivers I have heard so far want some sort of special "consideration" in order for me to get what I want from them and, more importantly, no single "treatment" will certainly "fix" any particular driver, according to what I have heard so far.  I can say at this point that there are certain markers that rule certain drivers out entirely, at least for my purposes.

I remember writing the "It Takes Balls to Shop" thread, thinking about obtaining "parts" in general.  And so far it looks like it is possible to learn from the various speaker and driver cults... as long as one keeps it all in the context of personal experience.

Paul S

By the time I got seriously involved in hi-fi, in the early 60s, speakers and their drivers were already undergoing significant changes from which they would never "recover".  Basically, for reasons that are no longer clear to me now, drivers and speakers alike - in general - began to be built to absorb and withstand more and more power from amps that seemed to double in power, annually at first, and then, monthly.  One thing that my friends and I took for granted at that time was "Tone", that any and every speaker would have more or less of it, and, if necessary, we could either restore or imbue a speaker with Tone by various means.  Whether "dope", cabinet "tuning" or X/Os, I don't remember ever doubting my own ability to find a driver and make a speaker to sound the way I wanted it to.  But as power came to the front, Tone dropped to the rear and, finally, it was gone, and somehow Tone became less important than "transients" and "detail", and "clarity", until it became pretty much a non-issue, as though it either did not matter, or it was there all along (although it was not), or it was just a minor sacrifice for better "detail" and more aggressive "transients".

Fast forward to 2011.  "Tone" is definitely a lost art, tossed in at the last minute like a handful of salt or pepper when it is considered at all.  And, annoyingly, nothing seems to sound like it used to, back in the day, anyway, according to my experience.  The crux for me now is to find and nurture Tone, then to push it beyond GWB (girl with balalaika), into the realm of Serious Music.  Of course, part of the "problem" is expectations, that we can somehow make new the best of what is now - in fact -  quite old.  Also, as I described in the previous post, there is the "problem" that tuning too "true to life" requires true-to-life SPLs to finally bring it home.

This is, I think, another good reason to take it slow: to take in and process the "paradoxical" information in a way that will yield actual (as opposed to idealized) results.  Yes, I insist that a violin is not a viola, etc., etc. But in my own case I think I can back off sustained 120 dB in order to have Tone, if this becomes necessary.  OTOH, I am not going through all this merely to re-create an idea whose time has already come and gone.


Paul S

Again, not to make a "formula", but I was thinking about the possible roles of the speaker in "offsetting" the typical upward-tending tone/harmonics of hi-fi.  Sure, there are lots of strategies to "deal with" the upward tendency.  These ideas might range from using tubes, to plate loading, or electronically adjusting gain according to frequency.  But what about the speaker's - or driver's - rote role in this?

Something that has slowly dawned on me is that if I can somehow "naturally" control/limit "large driver" "issues", then "bigger" paper cones tend to "sound better'..  "Too big" means, larger than what is typically chosen by "high-end" designers or DIY copycats.  Again, OTHER FACTORS BEING EQUAL.  I put that in caps because there are WAY too many other factors at work to simply derive from this a working "large cone" axiom.  Rather, it is more of a "reflective" observation, and one that I think is worth making, or I wouldn't have made it.  Some typical "big cone" "issues" to chew on are response spikes, falling-off and/or suddenly-disappearing upper harmonics and/or tone, image bloat, muffling...

Any sort of cause and effect "reasoning" on this is vague speculation, but this does not bother me.  I would speculate in any case that the "bigger cone" can either "offset typical hi-fi frequency imbalance" or that it simply "presents it better", at least in terms of tone and harmonics, GIVEN that the particular "too big' cone in question can none the less go "as high as it needs to" to "do its job", etc.  And, believe me, this last is no "gimmie".  In fact, dealing with these issues is what healing the drivers is all about.

Paul S