Unstacking

[Zilch]

http://www.lansingheritage.org/html/jbl/specs/home-speakers/1973-l100.htm

There's no disagreement. 4310 was first, but not the subject here, which is why I didn't mention it or L88, it's predecessor, then L100, then 4311, the pro version of that. Reread my original statement, and I believe you'll find nothing inconsistent. That 4311 was initially sold through pro dealers does not imply that it was "first." I linked to substantiation of the fact that it, also, was subsequently sold through consumer outlets to clarify.

If your issue is that 4311 evolved from L100A rather than L100 directly, well, consider that the difference is largely academic in this context, and making the finer distinction serves only to confuse. Thus, I use "L100" here in the generic sense denoting the "family" of speakers well familiar to nearly everyone, not just the original vertical-in-line version.

Would there be some particular point of significance here relating to me trying to help Rick better understand his system? If so, I'm afraid I'm missing it.

 

[70salesguy]

L-100

Zilch, thanks for the clarification!

My point was that as a former salesman, I was "brought up" to believe that the L-100 came to the consumer market as the consumer version of the 4310 (as stated in the L-100 brochure). Then when the L-100 was upgraded to the L-100A, the 4311 followed for the "pro" market.

I guess the point there was that the product lines "cross pollinated" and were very closely linked. I always loved selling the L-100 because of it's heritage, build quality and sound! I never sold a pair of JBL's to a customer that wasn't very pleased with them! :yes:

The build quality of a JBL (at the time) was so impressive. Cast frames versus stamped, flat wound voice coils and other items as covered in a JBL brochure titled "The sum of the parts". I make no secret that I am a fan of the JBL product of the 70's era. I have a pair of grey 4310's, L-100's, 4311's, 4312's,
L-200's and L-26's.

Back to the stacking (or unstacking). I think I agree with the philosophy that lower level listening with one pair and stacked pairs for more intense (translate to high volume) listening.

This is the reason I joined AK. Quality discussion of these issues from people with many points of view. Perhaps others are like me, they often read about other equipment and think "those speakers aren't as good as my XXX 123's"
But listening to others thoughts and opinions is enlightening and often amusing as well!

The fact that I sold stereo for a time makes me no expert or any better qualified that others. It DID however give me a great opportunity to listen to a lot of different equipment for extended periods (especially when traffic in the store was slow) and develop clear opinions on what I liked or didn't.

You know, speakers are so subjective that within certain boundaries, who can say this or that is better? The "sound" of a KLH, Advent and AR are simular, which is best? The sound of a JBL L100 and an AR3a is so different, which is best? Both are quality units and have legions of fans.

To close here, in my new house I will have my basement den to set up my gear as I please with no consideration as to how it looks (like now in living room). I may stack or not, possibly array or who knows! I may mix my JBL's and Pioneers or may segregate them in their own silver enclave!

Thanks for all the thoughtful and insightful discussions folks! :thmbsp:

Looking forward to more posts from you, Zilch!

 

[bigstereo]

Zilch, thanks for the clarification!


This is the reason I joined AK. Quality discussion of these issues from people with many points of view. Perhaps others are like me, they often read about other equipment and think "those speakers aren't as good as my XXX 123's"
But listening to others thoughts and opinions is enlightening and often amusing as well!


Thanks for all the thoughtful and insightful discussions folks! :thmbsp:

Looking forward to more posts from you, Zilch!

Hear hear! I enjoy reading your posts too Zilch, keep em coming.:yes:

Rj

 

[Zilch]

Back to the stacking (or unstacking). I think I agree with the philosophy that lower level listening with one pair and stacked pairs for more intense (translate to high volume) listening.

I'm hoping to ferret out both the advantages and disadvantages of stacking here, and it looks like Rick is willing to play along. His setup is excellent for this.... :thmbsp:

 

[Tapehead47]

Let's ride it till the end, Zilch

Hardware store didn't have 3" plugs. They had 4" and 2". I'm going to try another store. Also will pick up the RS meter (always wanted one). Hope to have it done tomorrow.

How about a pair of old socks? Maybe wrapped in a ziplock.

Meanwhile I'll cue up Hot 'Lanta.

Rick

 

[Zilch]

Hardware store didn't have 3" plugs. They had 4" and 2". I'm going to try another store. Also will pick up the RS meter (always wanted one). Hope to have it done tomorrow.

How about a pair of old socks? Maybe wrapped in a ziplock.

Meanwhile I'll cue up Hot 'Lanta.

Rick

Yeah, we're gonna need the RS meter. Every speaker guy should have one. :thmbsp:

Socks aren't gonna get it. We're making these into closed-box acoustic suspension systems; gotta be sealed absolutely tight.

Plumber's supply will have the plugs if the hardware doesn't. These are made by Oatey, #33422:

 

[Tapehead47]

Yes, Zilch, that's the ones in the attachment. Will gather everything asap. This will be a cool experiment.

Rick

 

[Zilch]

Don't forget the silicone or teflon dry lube.

These are buggers to tighten without it.

I use silicone O-ring oil on mine, if you happen to have some of that instead.

["Slicker'n snot...." ]

 

[Tapehead47]

I have silicone grease for my pool o-rings.
I think the plumber hardware will give the JBL's a macho look.

Rick

 

[Tapehead47]

Zilch: Got the RS Sound Level Meter today. Our new plumbers supply didn't have the plugs...I'll try another place tomorrow.

Can we get started with the "Before"? Regardless, I'm going to enjoy messing around with this meter tonight.

Rick

 

[Tapehead47]

RS Sound Level Meter, Zilch

I took some photos of the meter.

Rick

 

[Zilch]

Rick, Audio Technician

Can we get started with the "Before"? Regardless, I'm going to enjoy messing around with this meter tonight.

Yup, that's the one!

Familiarize yourself with the operation of the device, then look at "Making an Integrated Average Measurement" (P. 16 in my manual.) That's the method we'll be using.

I'm getting repeatable measurements with that at 30 seconds using the beginning of just about any song on the Allman Brothers "Live" album. You pick the one we'll use, and I'll confirm that one.

You'll measure from your normal listening position (the Commander's chair, ) with the device aimed midway between the speaker stacks. Pick a target, so you're always aiming at the same place, a lamp or someting over there.

This is gonna seem silly, but it's important the measurement location be constant, so, soon as I start the sampling, I stick the back (heel) of the meter on my forehead, resting on the bridge of my nose, the mic pointing outward (not up.) It's then "listening" just about the height where my ears are, and I can easily aim at the target.

We'll be taking measurement with both dBA and dBC scale weighting. Once you find you can get reliable results, report your findings using both scales, at your normal listening level and adjustments, for top only, both, and bottom only speakers running. That'll be six averaged readings total, comprising your "Baseline." Restart the song for each, so the sample is the same.


Background: The genesis of this is your statement in Post #23:

I can play A-set, or B-set, or both sets. Each configuration gives a different sound.

The only known (to me) benefit of stacking is they'll play louder with less distortion. Period. That's it. (Well, not entirely -- I've already mentioned "Mutual coupling," which differentially increases the output somewhat.) So, you can either play them at the same level with less distortion, or at a higher level with equivalent distortion. However, the difference in actual loudness is relatively small before you're back where you started, distortion-wise. Take two speakers and deliver the same power to both of them, and they'll play louder than one of them alone, yup.

BUT, you say they sound different, not just louder. Does that make any sense? I mean, they're the same speakers, no? Individually, they each sound the same. There must be something else going on, some kind of "interaction."

The RS SPL meter will take readings on both dBA and dBC-weighted scales. The "Setting the Weighting" section of the manual explains the difference: when reading dBA, the meter doesn't "listen to" the bass. Measuring each playback configuration on BOTH scales will tell us something about what is happening to the sonic balance, and part of why you perceive them as "different."


Home Depot or your local equivalent has the plumbers' plugs, maybe....

[Hmmm. Rick has a POOL, folks! :thmbsp: ]

 

[Tapehead47]

Zilch: the meter has a tripod connection. I'm going to use the tripod to set the meter in the exact location my ears would be located.

This will be "pre plug" level results.

I might not be able to finish this until tomorrow.

Playing around with the meter I so far prefer a dB range of 100 to 110.

Rick

 

[gonzomeep]

Mutual coupling

I wonder what JBL did to overcome this in their 4435/4355/4350/DD66000-etc-etc. In the case of other TOTL speakers such as the Westlake BBSM-15, HR1 and SM1. All of these models use a double 15" woofer compliment. They share a common chamber too. Maybe you can tell us why it is not a problem with those models? I believe the biggest Westlake tower might even use dual 18" drivers. Any input on this is greatly appreciated.

 

[Zilch]

What's the difference between 4430 and 4435?

Maybe you can tell us why it is not a problem with those models? I believe the biggest Westlake tower might even use dual 18" drivers. Any input on this is greatly appreciated.

Well, we haven't determined that anything's a "problem," actually, other than, in theory, 4311's artificially boosted bass response contour in this particular application. Dual-woofer designs take advantage of some of these very behavioral chacteristics for better performance. I'm hoping Rick'll be able to do some of the same here, once we figure out what's actually going on and what's desired.

Every pro sound guy knows how to manipulate mutual coupling of multiple subwoofers for optimum performance. See the discussion beginning on Page 7-6 here:

http://www.jblpro.com/pub/manuals/pssdm_2.pdf

Gordon can likely tell us the mutual coupling frequencies (and requisite distance to achieve it) of each of the 4311 drivers, which varies with cone diameter. He's helped out with this in some previous "stacking" discussions, as I recall....

*****

Anybody have observations on Rick's now-documented preference for 100 - 110 dB (C, presumably) SPL listening levels to offer here? Or shall we wait for the dBA results?

 

[Tapehead47]

Plumber plugs vs. plastic tumblers....

After further experimentation I like the 100 dB thru 110 dB range with some 117 dB spikes. I would probably like to listen at louder volumes. I would say this is my minimum "being there" level.

Zilch: couldn't find the plumbers test plugs at Lowes today. Last night I plugged some plastic tumblers into the vents. I twisted one in and it was a tight fit. Any reason not to use them?

Sending pix.

Rick

 

[JimJ[VT]]

Built-in cupholders...

 

[Zilch]

Zilch: couldn't find the plumbers test plugs at Lowes today. Last night I plugged some plastic tumblers into the vents. I twisted one in and it was a tight fit. Any reason not to use them?

With the plumbers' plugs, we recover the volume inside the duct into the box, and need every bit of that. That's a "too small" box to begin with, and the tumblers consume volume.

Also, I'm not confident about the seal. You can tell by lightly depressing the woofer cones about 1/4". If they return to "neutral" at a snail's pace, the seal is good.

I'd say call the hardware store that had the 2" and 4" ones and ask them to get you the 3"s. Shouldn't take more than a couple of days; these are very common. If they normally stock them, they may even have them by now.

Do you have the baseline readings to report yet? Which song are we using?

I'm not gonna get all upset about your listening levels 'til I see the A-weighted measurements. That may be all bass you've got, though there's not much of it on the "Live" recording.

I see one of your tweeter domes is "pooched," and the diffraction-damping foam is gone. What's the condition of the other three?

Also, where do you have the controls set on the speakers?

This setup is in a 12' square accessory building room, right?

And finally, what's the distance from each stack centerline to the mic (+/- 1")?

 

[Tapehead47]

Zilch: The tumblers don't quite make the seal...the woofers are damped, but they return too fast. Will get "the plugs" this weekend.

I'm learning how to use the meter. I've got some measurements, but I wouldn't rely on them at this point. Will take measurements tomorrow nite when my scientist friend comes over for dinner. He loves this kind of stuff.
I would send you the data I have, but it's probably incorrect.

For the music source I'm going to record about 30 seconds from Hot 'Lanta beginning after the drum and bass lead in, starting just when all the guitars and organ chime in simultaneously. Daaaa.....Da..da..da..da..da..daaaaaaa....(get it?).

Yeah, my tweets are dimpled. the foam surrounds have been gone for many moons. I can live with it.

The room is 12' x 12'. Insulated, air conditioned, with 5/8" sheetrock.

Brilliance and Presence are all set to 5. Amp is set flat. Balance is centered. I have a Pioneer SX-D7000. All measurements will be taken with volume "straight up" at noon. That gives me about 106-108 dB in the sweet spot. I'll change the level if you advise me to.

Set 'A' is centered at 103" to the meter's mic.

The speaker sets sound different because they are stacked. Set B is on the bottom, and the bass is a bit louder than set A. Both stacks are spaced about 6" from the corners. I've moved them around a lot to try to get the best sound, and this seems to be the best position. Any suggestions?

I'm familiarizing myself with the meter. Just got to the "Data Hold" page. It will be very useful!

This is getting better now. You can show me all the charts and graphs in JBL's tech library, but I prefer this method of learning.

Also, I have an ADC Mark III equalizer, and a Pioneer RG-2 processor hooked into the "Adaptor" switch. I won't use them while making the sound measurements. Have you any recommendations?

So far, things are panning out. At least I think so. Will the pooched tweets make much difference?

Well, that's all I can think of for now.

Thanks!
Rick in Lutz, Fl.

 

[Zilch]

Will the pooched tweets make much difference?

Contrary to eBay seller's unanimous opinion, pooched tweeters DO affect the sound. Once we get everything aligned and working perfectly, you'll want to put some effort into fixing those, though for our present purposes, it won't much matter. The foams are also available from JBL inexpensively. I'll check my local source.

Set B is on the bottom, and the bass is a bit louder than set A.

Yup, good observation, Rick, and the RS meter will tell us by how much. The floor is a third boundary, so they should be playing 3 dB louder in the bass than the top set. The corners are giving 6 dB of boost to both pairs, over and above what they were designed to produce, balanced, as nearfield monitors. So, you are indeed on track of some of what we are out to discover already. :thmbsp: