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Author Topic: WON THAT CAB!!!  (Read 12136 times)

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EdBass

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Re: WON THAT CAB!!!
« Reply #42 on: March 27, 2007, 08:01:43 pm »

Here's a picture of one of my 200S cabs opened up, next to one of its big brothers. Same depth at 15", but the pic gives you an idea of the difference in size.  Notice that the port on the 200S runs the entire width of the cab, and is ducted on the top and bottom.
Your cab looks to be a modified Sorado cab.
I've never owned one, but I believe the following is accurate;
200s cab has the rear loaded horn, horizontal port. Sorado has two tube ports.
The Sorado was a more affordable option to the 200S introduced to the lineup in 1969. It was loaded with "Sunn Transducer" labeled 15" drivers instead of the JBL D140's.
 

pickinatit

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Re: WON THAT CAB!!!
« Reply #43 on: March 28, 2007, 06:28:13 am »

Ed,

I have to agree,  the two port cut-outs instead of the port the entire width of the cab  sure would make it seem so. (heavy sigh).  I never should have bid on it without pics of the inside.  Another lesson learned the hardway.

And I figured that the top speaker should also be baffled by the evident diagonal paint line on the side panel.

I'll probably end up restoring this with speakers that become part of my rig for the 1200S I recently bought.  The black widows that came in it will probably suffice if I get the one reconed or something.  As I said in an earlier post, one of them sounds fine, the other not so good.  Fixed up and in conjunction with a 2 x 12 and a 2 x 10 that I have it should really rumble.

Meanwhile I now will sit and wait for actual 2000S  cabs to come along.  If nothing else these hard lessons are teaching me patience.

EdBass

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Re: WON THAT CAB!!!
« Reply #44 on: March 28, 2007, 08:55:39 am »

The cab is 42"X24"X15" isn't it? I'll bet you could modify the baffle with a full width port, fabricate top port ducting to match the bottom, (while you're at it, fabricate a duplicate angle board to replace the bottom one that some idiot carved up) and have a "200S" after all.
All you need are the 140's!

basiklybass

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Re: WON THAT CAB!!!
« Reply #45 on: March 28, 2007, 06:55:16 pm »

From the pictures you posted, it looks to me like someone made a new front baffle for the cabinet...one can only wonder why. It looks like the inner pert members are still there...sort of.....Hey...It's still a Sunn...and that ain't all bad.

EdBass

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Re: WON THAT CAB!!!
« Reply #46 on: March 28, 2007, 09:22:36 pm »

I'd say the baffle is original, just carved up a bit. It looks like someone chopped a hole in the bottom duct, probably to fit a ceramic magnet, and decided to just rip out the top port instead of hassling with cutting the hole in that one as well. Interesting port modification in the baffle though.
It might sound great the way it is.
I'm personally not a big believer in exacting cabinet tuning for an instrument cabinet, I don't believe it to be all that important. By nature, the more specifically a bass enclosure is tuned the more frequency specific it becomes, and a bass guitar covers a pretty wide frequency range.
Also, I have it on good authority that in the days before CAD the phrase "that looks about right" was an accepted technical descriptive when designing musical instrument cabinets.

I still think you could run that port the width of the baffle, replace the ducting and have a more or less proper 200S cabinet.

Isaac

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Re: WON THAT CAB!!!
« Reply #47 on: March 29, 2007, 02:32:00 pm »

Ed, I don't understand what you mean by, "By nature, the more specifically a bass enclosure is tuned the more frequency specific it becomes".

Every ported cabinet is tuned to a specific frequency. Sometimes the frequency is a good choice for the driver and cabinet, sometimes not. Often, when the system is tuned to a poor frequency, the result is a very boomy, peaky response, which can give what is known as "one-note" bass. This can also result from a sealed cabinet that is too small. But a driver that is designed to be in a ported cabinet, in a cabinet that is well made and tuned to a good frequency (I'd say 'the proper frequency', but that implies that there is only one best choice) will have the widest frequency range possible for that driver. The reason that Thiele-Small parameters are used is that "that looks about right" very often wasn't even close.
Isaac

JoeArthur

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Re: WON THAT CAB!!!
« Reply #48 on: March 29, 2007, 03:41:49 pm »

Ed, I don't understand what you mean by, "By nature, the more specifically a bass enclosure is tuned the more frequency specific it becomes".

Every ported cabinet is tuned to a specific frequency. Sometimes the frequency is a good choice for the driver and cabinet, sometimes not. Often, when the system is tuned to a poor frequency, the result is a very boomy, peaky response, which can give what is known as "one-note" bass. This can also result from a sealed cabinet that is too small. But a driver that is designed to be in a ported cabinet, in a cabinet that is well made and tuned to a good frequency (I'd say 'the proper frequency', but that implies that there is only one best choice) will have the widest frequency range possible for that driver. The reason that Thiele-Small parameters are used is that "that looks about right" very often wasn't even close.

Um... No.

Sure, it is possible to tune a cab to a specific frequency. Yes, it may be somewhat based on the driver you will use. But this is "hi-fi" stuff - where a tuned cab usually means a "bass-reflex" design, and this is the only area where Thiele-Small parameters really mean anything.

Even though it is technically NOT a horn design - the "reverse loaded folded horn" of the 200s (et al) cabs - is not a "tuned" design. It is "untuned".

Tuning a cab, like a bass reflex, does cause a "peak" in the frequency response at the low end. This helps to extend the low end response of a driver. The "Q" determines how peaky this peak actually is, but the tradeoff for a sharper peak is reduced effeciency overall - you can't get something for nothing.

I have a 2x12" closed cab. It is 8 ohms with two 16 ohm drivers wired in paralled. The two drivers are only rated for 40 watts.

I switched out the 2x12" for a single 8 ohm 12" rated for 100 watts and left the other "hole" open. It sounds much better this way, but yeah, I'm only using it for guitar.

Isaac

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Re: WON THAT CAB!!!
« Reply #49 on: March 29, 2007, 04:30:29 pm »

I can't agree, Joe. The 200S cabinet was designed before the advent of T-S theory, true - came to Mr Sundholm in a dream, if reports are true - but it still has all of the design features of a ported, tuned cabinet. When you say that a port creates a peak in the response, I'm not sure what you mean. A properly tuned ported system does not have a peak in the response, unless the designed wanted one there. It is simply not true that every ported design has a response peak. If you like, I'll measure the 200S and tell you what the Fb, the box tuning frequency, is. Conversely, you could try to explain what an "untuned" cabinet design consists of. At least we agree that the so-called "folded horn" design is not a horn.

If your 2x12 sounds better with one 12" removed, great. I'm a firm believer that instrument cabinets are for producing sound, not reproducing sound, and whatever sounds best to the musician using it is what sounds best. I might not agree, but it's not my cabinet or my sound.
Isaac

EdBass

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Re: WON THAT CAB!!!
« Reply #50 on: March 29, 2007, 09:27:40 pm »

Ed, I don't understand what you mean by, "By nature, the more specifically a bass enclosure is tuned the more frequency specific it becomes".
To attempt a clarification of my statement; what I mean is the porting in any particular enclosure exists to support the directly radiated sound pressure of its driver(s). Generally ports are used to supplement the sound pressure levels at the lower end of a drivers useful range in a theoretical infinite baffle; i.e. a bass reflex design.
The sage JoeArthur nails it again;
Sure, it is possible to tune a cab to a specific frequency. Yes, it may be somewhat based on the driver you will use. But this is "hi-fi" stuff - where a tuned cab usually means a "bass-reflex" design, and this is the only area where Thiele-Small parameters really mean anything.
In Hi-Fi gear, very specific (to the response characteristics of the driver) cabinet tuning can be utilized to maximize the efficiency of the enclosure to a sometimes very specific range, and it’s my opinion that this overly specific tuning is not conducive to natural sounding musical instrument reproduction.
Hi-Fi normally (don’t tell Dr. Bose) requires a mixture of drivers, each with a specific purpose, or frequency range as its responsibility, 2, 3 even 4 way systems are the norm. I won’t even touch multi-amping, which specifies driver frequency responsibility even more precisely utilizing individual amplifier characteristics as well.
As far as instrument reproduction, I wholeheartedly agree with this Isaacism;
If your 2x12 sounds better with one 12" removed, great. I'm a firm believer that instrument cabinets are for producing sound, not reproducing sound, and whatever sounds best to the musician using it is what sounds best. I might not agree, but it's not my cabinet or my sound.

However I don’t understand the relevance of;
The reason that Thiele-Small parameters are used is that "that looks about right" very often wasn't even close.
Lots of wasted plywood no doubt, I know I’ve wasted my share over the years.
However, as you acknowledge, TS parameters weren’t even recognized by the audio design mainstream until the mid/late 70’s, Richard Small didn’t even publish his series of articles until ’73 or so. What parameters did the designers of early MI or Hi-Fi cabinets use?
I suspect that with designers such as Mr. Lansing "that looks about right" was in fact very often very close.
According to my ears, it also worked for Mr. Sundholm.
Of course you can measure the “Fb” of a 200S cab. You could measure the “Fb” of an empty beer can; ask Mr Sundholm how much influence the “Fb” had on his 200S cabinet design, that would be a discussion relevant to the turn this thread has taken.

I guess the question would be the definition of “tuned”. If “tuned” means “on purpose” this won’t hold water, but I think if you want a definition of an untuned cabinet, try any sealed cab. Generally the goal there is to emulate an infinite baffle. The only real influence the cabinet has over its driver(s) other than sound pressure resonation from the cabinet itself is the vacuum/compression damping of the cones excursion.
For bass guitar the directly radiated response of most drivers is subjectively considered to sound better with a little bottom end assist, hence the limited usage of sealed enclosures in a full range application. (I know, I know, the reigning standard is the SVT 8x10) An overly specific tuned reflex port sounds a little too peaky, even boomy to most ears.
In the case of the 200S, there seemed to be a lot more “that looks about right” than actual tuning going on. I think if you cut it in half, you would be closer to an actual tuned reflex cab than with the 2x15 configuration. You definitely get a kick in the bottom end, but I think mainly because not much of the back pressure above 100hz or so can make that turn to get out.

If you pop a 12 out of the closed 2x12, well, it’s tuned (see above) to some resonant frequency. Actually, this missing speaker method is currently in vogue in some boutique circles, and is generally referred to as an “untuned cabinet”. In fact, an amp manufacturer recently recorded demo tracks with one of these “untuned” was a 2x12, uh…now a 112 cabs.

Isaac

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Re: WON THAT CAB!!!
« Reply #51 on: March 30, 2007, 09:15:24 am »

Reminiscent of the original bass reflex cabinets. Many folks assumed that the proper size of the bass reflex port was the same as the effective radiating area of the driver. That can work in some cases, but usually, it does not. That's the kind of thing I meant when I said that "looks about right" often wasn't even close. Note that I didn't say it wasn't ever right. The 200S cabinet is obviously a good design, however it was arrived at. Lots of designs fit that mold, and they're the ones that last. Bad designs tend to go the way of the dodo.

But I still don't understand what you mean by "the more specifically a bass enclosure is tuned the more frequency specific it becomes". Every bass reflex, ported, or ducted port cabinet is tuned to a specific frequency, whether that frequency was chosen in advance or arrived at by chance. So no such cabinet is more specifically tuned than any other. There are techniques to lower the Q of the tuning frequency. Is this what you're talking about?
Isaac

JoeArthur

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Re: WON THAT CAB!!!
« Reply #52 on: March 30, 2007, 11:39:04 am »

Reminiscent of the original bass reflex cabinets. Many folks assumed that the proper size of the bass reflex port was the same as the effective radiating area of the driver. That can work in some cases, but usually, it does not. That's the kind of thing I meant when I said that "looks about right" often wasn't even close. Note that I didn't say it wasn't ever right. The 200S cabinet is obviously a good design, however it was arrived at. Lots of designs fit that mold, and they're the ones that last. Bad designs tend to go the way of the dodo.

Yes, assuming the size of the port in a bass reflex to be the radiating area of the driver would be a mistake. In the case of a bass reflex design, the port tunes the air inside the enclosure to a particular frequency - usually the resonant frequency of the driver.

IIRC, the smaller the port area the shorter the duct length and the larger the port area the longer the duct length - to maintain the same tuning frequency.

But I still don't understand what you mean by "the more specifically a bass enclosure is tuned the more frequency specific it becomes". Every bass reflex, ported, or ducted port cabinet is tuned to a specific frequency, whether that frequency was chosen in advance or arrived at by chance. So no such cabinet is more specifically tuned than any other. There are techniques to lower the Q of the tuning frequency. Is this what you're talking about?

Every cabinet may have a resonant frequency, but I don't think that implies that a cabinet can't be more specifically tuned. I think I see it more like tuning your guitar to pitch as opposed to just slapping on a set of new strings and randomly turning the pegs. Both will make sound (I know, I've done it!!)

The higher the "Q" the greater the chances are of that resonant air mass producing unwanted sounds - either by continuing to "ring" afterwards or producing a "peak" in the frequency response.

Reducing the "Q" decreases efficiency but extends the frequency response and increasing the "Q" increases efficiency but reduces the frequency response. Just can't get something for nothin'.

EdBass

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Re: WON THAT CAB!!!
« Reply #53 on: March 31, 2007, 09:05:38 am »

Actually, I thought that statement was pretty much self explanatory.
Well, here goes…
Keeping in mind I have never, or could even see a reason to take a 200S cabinet into an anechoic chamber; I would imagine (“that looks about right") that gaping shelved ports’ response peak to be soft, a more gradual response curve peak, enhancing a broader range of frequency, maybe +/- 1 db 20 – 110 hz? than say a more specifically tuned cabinet, such as a down firing sub used in a multi amped Hi-Fi application, with a response curve peaking hard between 50 and 70 hz. Theoretically, you should be able to pinpoint a port response spike to within a few hz, +/- 3 db whereas an MI cabinet will optimally have a softer more generalized bass enhancement.
The resonant frequency of the box doesn’t determine the port tuning; it’s no doubt a factor, sometimes an obstacle for a specific application, but not the determining factor. Everything has a resonant frequency, when I crank up at home I find the “Fb” of all kinds of regular household items, occasionally with less than favorable results.
If I get motivated, I’ll find links to response curve graphs to illustrate this concept.

JoeArthur

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Re: WON THAT CAB!!!
« Reply #54 on: March 31, 2007, 10:11:37 am »


Maybe something like this:

Isaac

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Re: WON THAT CAB!!!
« Reply #55 on: March 31, 2007, 10:18:30 am »

Okay, what you describe is a low-Q resonance. I can live with that.

The box doesn't have a particular frequency, resonant or other wise*. The Fb, or box tuning frequency, is a result of the interaction of the box and the port, which form a Helmholtz resonator.

*True, everything has a resonance frequency. At least one. Each panel of the box will have one, and, if it's braced, each sub-panel will, too. There are resonant peakes determined by the distances between parallel panels, and so on. But those weren't what we were talking about. A sealed box has no particular resonance frequency. That doesn't happen until we add a port, ducted or otherwise.

And Joe, you have the relationships correct as far as port area and length v tuning frequency. The graph is actually of sealed cabinets.
Isaac