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Old 7th February 2011, 05:48 PM   #371
jbell is offline jbell  United States
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Art:
Since you don't have hornresp up and running on your mac yet.

Here is an A/B with the SS15 vs sealed at 2.83 volt, and also at max input power 9.6mm xmax 40hz on up. (40v sealed, 63v ss15)

(since you said earlier you didn't care ported or sealed....)

Quote:
Originally Posted by weltersys View Post
Frankly, I really don't care exactly how the low end of the 3015LF in a box compares to the SS15, even a sealed box test would show the sensitivity of the driver between around 120 -200 Hz (it should be about 99 dB, as the specs indicate),
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Old 7th February 2011, 07:55 PM   #372
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Quote:
Originally Posted by jbell View Post
Art:
Since you don't have hornresp up and running on your mac yet.

Here is an A/B with the SS15 vs sealed at 2.83 volt, and also at max input power 9.6mm xmax 40hz on up. (40v sealed, 63v ss15)

(since you said earlier you didn't care ported or sealed....)
Appears your and Oliver’s sims show a dB or so difference in midband sensitivity between ported or sealed, so the difference between the SS15 should be 3 or 4 dB between it and a ported or sealed cabinet in the 45-120 Hz passband. A sealed cabinet of course will run out of Xmax before exceeding Pmax, reducing it’s maximum output.

If you measure that same 3 to 4 dB difference in the real world, you will verify that your cabinet performs as well “as built” as the sims predict.

Or you may find, as Tom Danley has, that they don’t always do what they should.

Tom wrote about the Jericho Horn in #586730 on the LAB, Thu, 07 October 2010 12:44:
PSW Sound Reinforcement Forums: LAB: The Classic Live Audio Board => Jehrico horn

“I hate how weight collects and adds up. Yes these are heavier than before.
We have made several revisions to the cabinet which added weight. While I was pleased with the sound of the generation at the Infocom show, it bothered me deep down inside that the woofer section for that enclosure fell short of the computer model in places.
The “missing output”, as much as 6-7 dB in the upper bass, was recovered by greatly stiffing the enclosure. That involved in part more braces and moving to one inch Baltic. “

Having followed Tom’s work (and using it as a benchmark) since the 1980’s, it is always interesting to read his observations.

Since your and Oliver’s sims only predict a 3 or 4 dB difference between a ported cabinet and the SS15, and cabinet build and measurement tools could amount to double that, I continue suggesting an actual comparative measurement to see where things sit in the real world.
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Old 7th February 2011, 09:42 PM   #373
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I agree a face to face showdown would be better. I do have a candidate for a bass reflex:

B&C 18PS100 woofer in 5.2 ft3 tuned to 38hz, 20" sonotube cab, very non resonant, and total weight = 42 lbs. As I approach it's limits, the main speakers are WELL beyond theirs.

I'll have to get around to building a SS15 though.
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Old 7th February 2011, 09:58 PM   #374
tb46 is offline tb46  United States
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Hi ontariomaximus,

The idea would be to build the enclosures with indentical drivers. Ideally you would do measurements, and also listening comparisons.

Regards,
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Oliver
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Old 7th February 2011, 10:32 PM   #375
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I've got some extra ply left over here and another 3015lf waiting for my second ss15 to be finnished. If someone would give me some cab dimensions I will build and test it. side by side with the ss15 that's already done, and end this argument once and for all.
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Old 7th February 2011, 10:32 PM   #376
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Quote:
Originally Posted by jbell View Post
Art:
Since you don't have hornresp up and running on your mac yet.

Here is an A/B with the SS15 vs sealed at 2.83 volt, and also at max input power 9.6mm xmax 40hz on up. (40v sealed, 63v ss15)

(since you said earlier you didn't care ported or sealed....)
Quote:
Originally Posted by ontariomaximus View Post
I agree a face to face showdown would be better. I do have a candidate for a bass reflex:

B&C 18PS100 woofer in 5.2 ft3 tuned to 38hz, 20" sonotube cab, very non resonant, and total weight = 42 lbs. As I approach it's limits, the main speakers are WELL beyond theirs.

I'll have to get around to building a SS15 though.
The 18" will give you almost 3 dB more level than a 15, even with the extra sensitivity of the TH, the B&C 18PS100 woofer in 5.2 ft3 tuned to 38hz should be very close in level, probably would have a bit more at F3.

Now if you built a TH of similar size and cutoff as your sonotube cabinet for the B&C 18PS100, you would have a valid comparison point.

Tapped horns can be built using nested sonotube, though you would need a big diameter for an 18", somewhere around between 25" and 30" ID as a wild guess.
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Old 7th February 2011, 10:55 PM   #377
jbell is offline jbell  United States
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ONLY when the snow is gone and it's a bit warmer, I can do this: (even though I'm sure art will never accept any of my measurements)

Test a ss15, sine waves only 2.83v and 28v at 1 and 10m. Also show a smaart pink noise measurement with a reference spl at 60hz.
Directivity test. Take a 10' string and walk around in a circle and take measurements on 50,70,90hz sine waves.

Make a plate for the front of a ss15, that I can mount a 3015lf, and either 2 or 4 three inch diameter ports. This will use the EXACT same driver, and I will not touch any of the measuring equipment settings between tests.

Here's what you (and only you) must do art:

You must design the ported box and tell me how many ports and at what length they should be cut. (ss15 is about 215-220liters)

I'll use gasket foam and seal the plate air tight to the front of the ss15. This will assure the exact same cabinet volume, same cabinet flex, same driver, same input, same measurements.

THEN, when I post the measurements, you must accept them. period.... if you do not agree to that, then I won't do this test for you.

Until it gets a bit warmer, here's some measurements to chew on....
ProSpeakers Forum - Fitzmaurice Titan 48 - Wayne Parham, October 21, 2007 at 14:31:26

In particular look at what happens at 40hz from 100 watts to 800 watts.... only 3db. Even though this is a 35hz 1/4 wave FLH horn using the same 3015lf driver, the designer will tell you it's operating in 'direct radiator mode' at that frequency. Hmm... direct radiator.... like a sealed or ported cabinet.

If a particular design is only 3db more efficient at 2.83 volts.... guess what, it's like the difference between 28v and 80v in this particular case.... so 3db is nothing to sneeze at.

From the measurements from ported, front loaded, rear loaded, tapped, etc.. that I have built in the past... It should look like the ported cabinet brought a knife to a gun fight.

The reason is that I don't care what a sub can do in the 'midbass or midrange' area. If I need more 160hz, I'll eq it in. A sub cabinet must provide the most output at the hardest to reproduce frequency -- that's 40hz-70hz. That's what I care about. If it can't do those frequencies, then it won't work in the real world. You mention 3db difference ported or sealed to ss15... at 60hz it's 10db.... If the above example shows you anything about what happens real world with real power, and only gaining 3db going from 28v to 80v.... then that 10db difference the sim shows you at 60hz makes it pretty obvious why I like the ss15.

Last edited by jbell; 7th February 2011 at 11:11 PM.
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Old 8th February 2011, 03:21 AM   #378
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Quote:
Originally Posted by jbell View Post
ONLY when the snow is gone and it's a bit warmer, I can do this: (even though I'm sure art will never accept any of my measurements)

Test a ss15, sine waves only 2.83v and 28v at 1 and 10m. Also show a smaart pink noise measurement with a reference spl at 60hz.
Directivity test. Take a 10' string and walk around in a circle and take measurements on 50,70,90hz sine waves.

Make a plate for the front of a ss15, that I can mount a 3015lf, and either 2 or 4 three inch diameter ports. This will use the EXACT same driver, and I will not touch any of the measuring equipment settings between tests.

Here's what you (and only you) must do art:

You must design the ported box and tell me how many ports and at what length they should be cut. (ss15 is about 215-220liters)

I'll use gasket foam and seal the plate air tight to the front of the ss15. This will assure the exact same cabinet volume, same cabinet flex, same driver, same input, same measurements.

THEN, when I post the measurements, you must accept them. period.... if you do not agree to that, then I won't do this test for you.

Until it gets a bit warmer, here's some measurements to chew on....
ProSpeakers Forum - Fitzmaurice Titan 48 - Wayne Parham, October 21, 2007 at 14:31:26
.
Jim,

I can accept your measurements, no need to go to great lengths to do a front load test, any old box you have sitting around is fine to get the relative difference. Just looking for the same speaker in the same place.

Directivity tests- if you measure in proximity to a building it would be more appropriate to rotate the cabinet, rather than moving the microphone.

I can do the same with my small tapped horns, it will be interesting if they show directivity in singles, as I have not noticed any to speak of.

Your observation about small horn cabinets folding up like a cheap suit is something I have measured extensively.

PSW Sound Reinforcement Forums: LAB Lounge => JBL SRX718 - Basic Distortion Measurements

As you said August 2008:

“If 40hz is your low frequency that you need for your PA, that efficiency at that freq sets the overall response you can achieve, as it's the hardest to reproduce and most power intensive frequency in the PA power band. (which we obviously know) A sub that's 13db more efficient at 100hz vs 40hz, helps little. If I need more 100hz out of a sub, I'll eq it in. However, If I need more 40hz... there's only one way to get that, big power and big excursion, and that limits the overall spl you can get out of your cabinet.”

Several years before that I had abandoned my Chorn design for Lab 12” in ported cabinets, like you I was willing to sacrifice the upper response for a gain in the lower response. The Chorn behaves like BFM’s and Jeff Permian's offerings.

I have found in an outdoor side by side test on adjacent stages that four ported 2 x Lab12” had 2 dB more output at 40 Hz than eight Meyers 650P 2x18 cabinets, using a small fraction of the power, space and weight.

The Lab 2x12” work so well and allow a flat to 32 Hz response, it appears to me even with the SS15 I’d be leaving a behind a little LF.

I am about to pull the trigger on a pair of B&C BC-18SW115 , the speaker used in the DSL TH-118.
In the same size cabinet as a TH-115, and very possibly the same path length (phase plots overlay) it goes way deeper, is more sensitive, and due to the larger, higher Xmax driver, has a lot more output.

I have a little bit more volume to play with than the TH-118, my cabinet will be 22.5 depth x 26.5 width x 45” height.

I’ll be sharing my results and hoping for some design help.
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Last edited by weltersys; 8th February 2011 at 03:43 AM.
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Old 8th February 2011, 03:42 AM   #379
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Welter, It would be innaresting to see how my B&C 18PS100 ported design would have fared.
FWIW, it is 6.5 ft3 externally, and 42 lbs. I don't think it would be outdone by any system that doesn't exceed those 2 parameters.
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Old 8th February 2011, 02:56 PM   #380
jbell is offline jbell  United States
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Quote:
Originally Posted by weltersys View Post
Jim,
I can accept your measurements, no need to go to great lengths to do a front load test, any old box you have sitting around is fine to get the relative difference. Just looking for the same speaker in the same place.
ahh, but it doesn't... as olivers posts on ported vs ss15 show. I could just set the port tuning to 20hz... then what?

You tell me the ports, and I'll do the plate on the front of the ss15.

Quote:
Originally Posted by weltersys View Post
Directivity tests- if you measure in proximity to a building it would be more appropriate to rotate the cabinet, rather than moving the microphone.
I have Acres of land... with one house and one barn... no need to go very far to be very far away from buildings.

Quote:
Originally Posted by weltersys View Post
The Lab 2x12” work so well and allow a flat to 32 Hz response, it appears to me even with the SS15 I’d be leaving a behind a little LF..
The lab2x12 posted on soundforums.net...

Yes the ss15 is leaving a bit of 40hz behind in single cabinets. I always tell anyone building, run pairs or quads. It's flat to 40 in quads, and pretty respectable in pairs. If there were anything I could change in this design, it'd be to get it flat to 40 in pairs.
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