D-MAN
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Posts posted by D-MAN
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Dang! that's a good price! Is that for a pair?!
Ought to bite into the used K-trade. Shipping appears to be a problem, though.
That "Belle" is a good looker, too.
DM
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I don't follow what your purpose is... what are you trying to achieve?
If you become asymetrical on the horn (now this really DEPENDS, but), you will trash the phasing of the waveform, the higher in frequency you go, the worse it will get.
Also, are you modifying or building from scratch?
DM
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I've found that AC power filters definitely compress dynamics. However, they also definitely clean up the "hash".
I do not run my power amp (I have separates) through the filter for this reason.
I do, however filter the pre-amp and especially the cd player.
DM
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Of course, we can still call the terminus the "mouth" as a matter of convenience and we'll all know what we mean.
I just wanted to clarify the mouth size issue for others who might be confused why the numbers don't line up with the formulas.
DM
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I'll throw in my 2 cents on the 1946 Khorn seen above.
The 45 deg. reflectors at the tailboard is a good idea, it certainly won't hurt anything. However, at the time, it was a 12" driver version, and 12" drivers typically have a higher frequency corner than a 15" one naturally would. Therefore, the point of retaining higher frequencies becomes somewhat pointless if you want to stay with a 1rst order (6db slope) crossover.
So I see it as being related to the mass roll off of the driver as to whether the extra work of a 45 deg. reflector on the tailboard is going to be beneficial or not. I take it that PWK decided it was relatively pointless (or "non-ecomonical") for the 15" variety. The crossover and driver/reflector issues and subsequenct decisions were apparently economically based IMO.
The 12" version also used a front-chamber (at the throat) to reduce the upper frequencies (mass reaction) acting as a low-pass filter, and allowing a 6db slope crossover to be used. This is enough to indicate the ability of the 12" driver to put some upper bass frequencies through the horn. The lack of a front chamber on the current 15" version also indicates that the upper frequency rolloff limit of the K33 is low enough to make a front chamber uneccisary.
There is an issue with the intermediate channel structure in the Khorn as it goes from horizontal to vertical to exit at the tailboard. This "twisting" of the waveform is naturally detrimental to upper bass frequencies.
It seems to me that if you WANT to use the wedge reflector at the tailboard, you should also go with a driver with a rising response curve, to compensate for losses and acheive a higher band pass. That way, there MIGHT be some upper bass frequencies to reflect!
I'm sure that there is a finite limit to the frequencies that can be forced through the channel twisting, although I don't know for sure. Seems to me that one could theorectically expect to acheive a 500Hz crossover point, though. I would be willing to bet it could be done, but more than likely, you'd have to change drivers to do it. Also the crossover would have to change, of course. Whether you could stay with a 1rst order crossover would also have to be resolved and that would depend on which 15" driver is used.
It would be a major undertaking, in other words.
DM
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JC, the mouth size is rather up in the air anyway! Don't worry about it - you have an inch of play on either side before you change the flare rate of that section to an appreciable degree. That is a change of 39 sq.inches in a mouth size of over 720 sq. in! Big deal!!! It ain't a precision thing, kids!
It just has to be a certain minimum size. The Khorn is 675 sq. in, so you are easily in the ball park.
BTW, that isn't the mouth, anyway! That is the "terminal exit". In corner horns of this type, the walls and floor form a portion of the horn AFTER the soundwave exits the cabinet, so the expansion continues for a bit. Perhaps not quite as much as the Khorn being that the side-firing variety exhausts directly along the walls, but it will still be there. A larger exit area would aid in 1/4 space placement, but for 1/8th space, it is well within "tolerance".
The total mouth size of a 40Hz 1/8th space (corner) horn is approximately 1138 sq.inches or Keele's optimum mouth size of 1030 sq. in.
See what I mean?
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I'm a die-hard horn fan, but if I HAD to have a direct radiator, I wouldn't hesitate to get a pair of ADS (again).
I had a pair of the small metal ones years ago, and they blew away much larger speakers more than 4 times their size. They were truly outstanding performers.
They would make awesome computer speakers - wish I still had them now!
DM
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Well, Gil painted his back chambers, which I thought was pretty funny! (at first glance).
Actually, I'd use white because its easier to find a fallen wingut, etc., but as Gil pointed out, painting the interior is actually a good idea because it seals any "missed" airleaks.
I've also read of people painting the interior horn channels to reduce viscosity (the tendency of air to "cling" to a surface). In the Jub's the channels get painted black to prevent showing through the grill cloths, I would therefore use a gloss black on that, killing 2 birds with one stone, so to speak.
The Pioneers? Who knows - BigDnFay uses the Pioneers with apparent satisfaction. I wanted to point out I'm sure they will sound different from the Kappa-Pros and probably the stock Klipsch, too. We all dream of finding the "sleeper" drivers, cheap and yet astounding, don't we?
DM
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JC, That DOES look great! You are doing a fine job.
Mark1101, part "K" does not restrict the channel cross-section (although it may look that way), it is a waveform reflector.
The reflected angle equals the incident angle.
You are probably thinking of a radius channel turn - good for low frequencies (i.e., below 200Hz) but not good for maintaining mid-and-upper bass frequencies around bends.
Yes, access hatches are needed both top and bottom in order to get at the drivers.
DM
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Indeed! But that goes without saying.
Where are the excursion limits on either of these drivers?
DM
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If that's what Edgar said, he was wrong - the midrange is the most "sensitive" component in the Khorn.
Perhaps he was alluding to the fact that the output of the bass horn sets the overall efficiency for the speaker system, the other components being attenuated as needed to match it.
DM
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Armando corrected me - the rest of you should be ashamed for letting me get away with the previous version of what I posted! I was an idiot...
Here is the corrected version.
DM
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I don't regard the Pioneer as a T/S match, in other words! We can examine it further, if anyone would like...
DM
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T/S "matches" don't always sound the same. The specs are made up from ratios, and even though the number might be the same, the underlying specs that made up that value can be wildly different, especially total Q!
DM
hmmmmm................
For example, a light cone/suspension/moving mass, etc. and a "mediocre" magnet structure, or a heavier cone/suspension/mm and a very powerful magnet structure could result in the same Qts value, although how it got there is completely different... and so are the sonic results!
In the case of the 12" Pioneer, I would start with the suspension/mm part of the equation...
Anyone figure out the upper and lower frequency corners on that particular driver?
DM
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That would be a waste of a fine horn driver. The LS has too small of a back chamber for that particular driver, and will raise its FS.
So my advice is, go ahead as long as it is a turn-key operation.
If you have to hack, definitely NOT!
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Scaling works if everything is scaled according to wavelength, i.e., you can scale up and down as dictated by the change in wavelength (longer or shorter).
However, the thing to remember is that the MOUTH SIZE doesn't change for changing throat sizes (drivers) unless you change the Fc (wavelength, etc.). So technically, unless scaling for a different Fc, the scale thing doesn't work.
Anyway, the whole thing goes out the window when you change throat or Vb by itself and retain the same Fc and mouth size, because the channel lengths and widths change.
If you want to size competively with the Jubilee, that is a whole other can of worms...
The geometry has a limit as to what the channel widths can be supported, and so does the mouth size. A large throat and/or larger channels cannot fit into the folding geometry.
The whole thing could be made bigger, of course, but who wants that? There is a point of diminishing returns - why not settle for the dual 12" driver Jubilee, if you have to make too many compromises?
Where that point lies, I will leave to you...
My design criteria was to stay in the same footprint as the original Jubilee as closely as possible. It can be done, but's a pain (I won't say exactly where)!
DM
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Sorry to say that there is no way a 15" will fit. Maybe in Gil's "Base of the Earth" cabinets.
The baffle will only fit a driver 12 inch. The drivers are typically 12 1/8. The internal width of this baffle is 12 1/4. Tight quarters huh?
Honestly, this "w" style cabinet can easily be adjusted to fit two 15" or two 18" drivers.
Gosh...if I just had the time....we could try all that out.
jc
I wouldn't say "easily". I've designed 3 different 15" twin horns now, and I'm pretty much sick of it!
It depends on the throat size/Vb (and hence, the drivers) you want to use, so basically one-size does not fit all!
However, I think I've pretty much covered the gamut of available drivers appropriate to the application!
I expect them to be around 108+db or so.
DM
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T/S "matches" don't always sound the same. The specs are made up from ratios, and even though the number might be the same, the underlying specs that made up that value can be wildly different, especially total Q!
DM
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I have the Eminence Kappa pros on hand and the cheapo Pioneer woofers coming.
Anyone want to take a stab at which ones will work best?
I won't get to work on this much this week. October is the month of "gettin er done".
jc
Is this a trick question?! Of course the Kappa-Pros. You should have saved your money with the Pioneers. Or better yet, just send it to me, since you clearly have more than you know what to do with!
But seriously, the power bandwidths will be quite different between the two pairs. It depends on the "sound" you prefer, but I'll bet that you'll end up preferring the Kappas.
DM
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The raw sensitivity of the K33E is approx . 96db (average across a frequency band) but when in the horn AND in the corner, that adds +9 db (or more) to its sensitivity. That is at least a 3-fold increase (ha, pun intended!). That means approx. 105db overall.
DM
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Concerning "time-delay/phase alignment", I was referring to the fact that all bass horns have inherent "time-delay or phase-alignment" issues due to the different pathlengths.
This doesn't necissarily mean that its audible, such as with the LS, being that it has about 2 feet of path length, well below the 3 foot difference limit (3millisecs) that a human can discern (see- it's there, but inaudible). It's just a matter of physics that its there in the strictest technical sense. No, I don't notice any time delay issues with my bass horns, although I know that it is actually there, it has to be! They seem extremely "fast" and "tight" to me, although the difference in path length is about 5 feet, well within audible range. So why can't I tell? I think that the ES network I'm using on the woof/midrange has alot to do with that.
Dana
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Concur. The midrange driver is the most sensitive. It is also 16 Ohms.
The woofer/bass horn (+9db) and tweeter are not attenuated.
DM
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I've wondered about this myself. As you know I'm a fan of the removable motor board.
However, the confinement imposed in the Jubilee back chamber is such that I question whether a board-mounted driver could fit through the access cutout, being that, in the stock version, the access is recessed flush with the top and therefore requires an inside lip.
Hence, I don't know if there's room enough to fit through the available "hole".
I would therefore go with the more-likely approach of a direct-driver mount to the baffle using t-nuts embedded in the baffle in the mounting pattern of the driver.
Correct me if I'm wrong, guys...
DM
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I got news - that ain't a cap that is stinking! Caps typically fail as an open once that much electrolyte leaks out.
The correct answer is the insulation on a transformer winding. Expect smoke next, then fire.
DM
Shinall speakers are on clearance sale!
in Technical/Restorations
Posted
Empty finished cabs at $450 ea? The WOOD costs half that! At least here it does...
DM