Absolutely, especially since you plan on running them as pairs with tops over for your intended use.
Measure a pair @20v each @10m with the cabinets side by side upright, and then again with the cabinets on their side with the mouths touching.
Then measure a single cabinet @28v@10m upright, and on it's side.
Those 4 measurements would be nice to see, and also should give you a great idea on how they will perform in real life, as you'll probably be running these 20m from the audience in pairs.
Andy,
The upper frequency "peaks" will reduce in multiples. They should be well above where you would want to cross over a "sub", anyway.
Your lesser measurements below 50 Hz could be due to several different possibilities:
1) If you are using a dB meter that has only “A “and “C” scale, the “C” scale is better for measuring LF, but is still down about 2 dB at 40 Hz.
2) Microphones have different response, your or Jim’s may have deviations in the LF.
3) You added some corner ramps, which reduce cabinet volume. They did not seem to affect the upper response compared to Jim’s, but the reduction in cabinet volume may have reduced the LF.
Overall, the SPL readings are remarkably consistent between the two builds.
I am curious as to what voltage the 3015LF in the SS15 will sustain without exceeding Xmax (19.2 mm peak to peak).
Looking at your SPL readings I’d guess about 45-48 Hz will be as low as your cabinet can go with full power, 450 watts, 60 volts.
Art Welter
Attachments
Given all the caveats posted by Art Welter, what has the 4pyros' cab gained over Jim's? At first glance, it looks like a lot more of weight and path-length for a slight loss in LF SPL levels and gain at HF at frequencies before which the subs will be crossed over anyway.
Perhaps, we will still find out that Jim has pretty much optimised the 3015LF in his SSTH15!!
Perhaps, we will still find out that Jim has pretty much optimised the 3015LF in his SSTH15!!
I also had some problums with my test waves. I downloaded the the test CD that Jim had suggested and put it on a stick. My player would not play the files so I put them on a CD.
I started testing at 10 to 20Hz and was getting some high numbers. Than when I whent to 20-30Hz the DBs dropped by 10 or so and steady rose again from there. I am not shure what that was about but I will take a look at the CD in Gold Wave and try to convert the files for the stick that can work on the player. Andy
I started testing at 10 to 20Hz and was getting some high numbers. Than when I whent to 20-30Hz the DBs dropped by 10 or so and steady rose again from there. I am not shure what that was about but I will take a look at the CD in Gold Wave and try to convert the files for the stick that can work on the player. Andy
Andy,
Other than a (possible) difference in meters, was there any difference in the way you tested your cabinet than the way Jim tested his?
What "better" way do you have to test it?
By the way, it is no easier to dial in 28.3 volts than it is to dial in 2.83 volts, they are just 20 dB different in level, one watt or 100 watts into an 8 ohm nominal load. It is easier to set the level if you turn down the amp gain in either case.
Get the voltage correct at 60 Hz, don't mess with it at different frequencies, chances are your meter will be most accurate at 60 Hz, and may be "off" at other frequencies.
Set the level without a load to get it close, then trim it out with the load (speaker). Some amps won't change in output voltage at all between no load and loaded, others do change, especially with lower impedance loads.
At 28.3 volts, you will be able to see the speaker move a bit, but it will still have more than six dB of headroom left down to 45 Hz or so.
If your cabinet has a longer path length than the SS15, it may have a slightly lower Fb, or Fc.
Speaker excursion in standard horns just increases as frequency decreases.
Fc (horn cutoff) is the normal term used for the LF corner with horns, but TH actually behave more like BR than regular horns at the low corner, there is a pronounced excursion minima, followed by a very rapid increase in excursion.
A lower Fb with the same box volume reduces LF efficiency.
A lower Fb in a smaller box volume (space taken up by corner ramps, etc.) reduces LF efficiency further.
As long as the speaker does not run out of excursion, you can use EQ to make up for the lesser output down to, and slightly below Fb.
With EQ, you may be able to squeak a few Hz more bottom extension (at a lower maximum SPL level) out of your box than a "standard" SS15.
Art
At 10 or 20 Hz your meter will mostly be reading wind noise, the cabinet response drops at around 24 dB per octave below Fb.
If you don't have a wind screen for your meter, you will often have to wait a long time between gusts. Even with a wind screen, using the Magnitude Response with Smaart, I spend far more time waiting than measuring, but at least I can look at the Coherency trace to see if the measurement has suffered from wind contamination.
If the wind is steady, (never is here in Madrid, NM
) with a dB meter, it is hard to tell how much LF is wind noise, and how much the speaker is putting out.Pyros, you need a detailed drawing from your ‘custom’ SS15 otherwise all this good help is for nothing. That way you can translate your cab back to a corresponding HornResp prediction and find the points in your design that can benefit from a little re-arranging. Also from a corresponding HornResp you can calculate exactly the max power you can use and as long your amplifier doesn’t go over that max you can eq as much as you like at any point in the bandpass!
i finished the building/painting. since this is being used on the beach for a beach radio, i decided to paint the sub to look like a cooler. it kinda looks like one from far away
An externally hosted image should be here but it was not working when we last tested it.
The maximum safe power that can be used can more accurately be ascertained by measuring cone excursion in the actual cabinet rather than relying on a simulation.
True, but give me an example where excursions in a TH was higher then predicted, just one Art?! Which means the calculated excursion is safe. But I would agree with you if you say in reality some TH's can be powered way beyond predicted max safe power.
Nevertheless, it still doesn't matter how much and where you EQ as long you don't feed your cab with more watts then its max safe power (from predictions or real life measurements).
That's probably the case for every alignment simulated by a program that doesn't take BL nonlinearity into consideration. Most assume that the driver behaves at large signal levels the same way it does at small signal levels, which is simply not true.
Dave NonZero -
Well the cabients have a -7 to -10 DB drop at rear to rear off axis. Plus some cancellation. And being 15' off rear wall I wasn't getting any real reflections. IE none of that boom room node going on. BUT if you notice there is also have a pair of 12x1" 2 way's as monitors. So cutting through wasn't a problem.
My ears weren't ringing at all afterward. Though I only went out in front maybe 3 times the whole night. And only in front of the speakers for the last song. To get a quick massage!
Salz - no those arent DIY tops. JFL210's.
Well the cabients have a -7 to -10 DB drop at rear to rear off axis. Plus some cancellation. And being 15' off rear wall I wasn't getting any real reflections. IE none of that boom room node going on. BUT if you notice there is also have a pair of 12x1" 2 way's as monitors. So cutting through wasn't a problem.
My ears weren't ringing at all afterward. Though I only went out in front maybe 3 times the whole night. And only in front of the speakers for the last song. To get a quick massage!
Salz - no those arent DIY tops. JFL210's.