Hi all. I'm looking to replace the 15' drivers of a set of JBL4770 reflex bass boxes and I'm having a few doubts about which set of speakers to use.
Where I'm living I have access to the following speakers:
* Eighteen Sound 15mb700
* Eighteen Sound 15nd830
* B&C 15PS76
Looking at their characteristics, the first driver has a pretty stunning sensibility of 103 dB and a program power of 600 watts.
On the other end of the spectrum, the B&C has 99dB of sensibility and 1100W program power.
Plugging in both into a peak SPL calculator with a dual speaker configuration gives a 1.5 dB advantage to the more efficient speakers.
Now, I wonder whether this would correspond to real-life situations and the Eighteen sounds are the superior choice.
Both drivers are recommended for the application (large ported bass baffles), however the 18 sound more closely resembles the original driver in power consumption, which seems like a concern since the application for this is going to be in a reggae sound system for multi-hour sessions of strong bass, in venues with questionable electric installations and some outdoor usage.
The question that remains, for me, is if these specs have anything of relevance to say on the matter of power compression. I'm slightly concerned about the B&C's higher power requirements (more money in renting amps and less overhead for crappy electric installations), and whether all this is just theoretical or if the first driver's just the superior choice.
Any advice would be appreciated!
Where I'm living I have access to the following speakers:
* Eighteen Sound 15mb700
* Eighteen Sound 15nd830
* B&C 15PS76
Looking at their characteristics, the first driver has a pretty stunning sensibility of 103 dB and a program power of 600 watts.
On the other end of the spectrum, the B&C has 99dB of sensibility and 1100W program power.
Plugging in both into a peak SPL calculator with a dual speaker configuration gives a 1.5 dB advantage to the more efficient speakers.
Now, I wonder whether this would correspond to real-life situations and the Eighteen sounds are the superior choice.
Both drivers are recommended for the application (large ported bass baffles), however the 18 sound more closely resembles the original driver in power consumption, which seems like a concern since the application for this is going to be in a reggae sound system for multi-hour sessions of strong bass, in venues with questionable electric installations and some outdoor usage.
The question that remains, for me, is if these specs have anything of relevance to say on the matter of power compression. I'm slightly concerned about the B&C's higher power requirements (more money in renting amps and less overhead for crappy electric installations), and whether all this is just theoretical or if the first driver's just the superior choice.
Any advice would be appreciated!
Hi
Power & sensitivity are important, but so is Xmax
You need to compare the T/S Thiele/Small parameters between them & see which is closest to what you have.
Power & sensitivity are important, but so is Xmax
You need to compare the T/S Thiele/Small parameters between them & see which is closest to what you have.
Power compression.
Just cause it can take 400 watts doesn't mean it is 6db louder than 100 watts.
Just cause it can take 400 watts doesn't mean it is 6db louder than 100 watts.
Also, keep in mind the listed sensitivities are usually averaged from the actual frequency response chart from the respective manufacturer. Look at the frequency response of the 18 Sound driver. See how it peaks up top? Those peaks are averaged in to get their "rated" sensitivity, so it makes the sensitivity figure look great! . It does not tell you how the driver will response on the low-corner because that is definitively alignment-defined. Basically, take those ratings with a grain of salt until you really dive into the T/S parameters in conjunction with the published Frequency response charts.
I guess it all depends on your definition of the word "usually". I have seen enough discrepancy between these things that I do not necessarily assume the sensitivity is the calculated midband sensitivity calculated from the other parameters.
Case in point: the first 18 Sound driver has a calculated midband sensitivity of 98.9 db 1W/1m, and since it is 8Ω, the 2.83V sensitivity will almost nearly match it, maybe 0.5-1 dB higher or so, because the Re is down to 5Ω. No where near 103 dB @ 1W/1m. Again, it all comes back to how they measure it. Eighteen sounds measures their sensitivity from Fs to 10*Fs, which in this case is 42 Hz to 4.2kHz. If you look at their frequency response graph, there is a huge SPL peak caught within this range, and they average it in, like so many other manufacturers, because they can "claim" it as being part of their rated sensitivity, as an average value over their pre-defined range.
Daishiman, don't just look at the number specs. Look at the manufacturers frequency response chart, while also paying attention to the Re of the driver. Even though many drivers are rated 8Ω nominal, under the same 2.83V input, the ones with lower Re numbers will actually receive more power (P= V²/R), and thus be more sensitive to the input voltage, but this doesn't mean that it is actually more efficient. It just seems that way because getting/consuming more power.
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Information Needed on Enclosure
You need to find the enclosure volume, tuning and port dimensions and plug the thiele small parameters into Win ISD or Hornresp. I can't tell you anything about which driver is best if I have no information on your enclosure.
Higher sensitivity woofers tend to work best in larger cabs. A small cab will "choke" their low bass response. The sensitivity specs tell you nothing outside of an infinite baffle situation which favours as light a cone as possible and maybe a low resonance if you value low sensitivity in this situation. Box volumes can vary vastly even among the same diameter driver. A Kappalite 3015lf requires over 6 cubic feet to play flat to 40 with 99dB efficiency. A Faital Pro HP1030 only 3 cubic feet but loses 3dB efficiency.
This assumes decent motors on each woofer. A subwoofer that isn't sensitive because of high moving mass but has a strong motor will work well in a smaller cab but need more power. A subwoofer that has a weak motor (and high electrical Q) isn't much good in this regard but I'm assuming you are not using Skytec woofers.
As you are not dealing with subwoofer only the midband efficiency is also important, but for the lower frequencies the graph is enclosure dependent.
You need to find the enclosure volume, tuning and port dimensions and plug the thiele small parameters into Win ISD or Hornresp. I can't tell you anything about which driver is best if I have no information on your enclosure.
Higher sensitivity woofers tend to work best in larger cabs. A small cab will "choke" their low bass response. The sensitivity specs tell you nothing outside of an infinite baffle situation which favours as light a cone as possible and maybe a low resonance if you value low sensitivity in this situation. Box volumes can vary vastly even among the same diameter driver. A Kappalite 3015lf requires over 6 cubic feet to play flat to 40 with 99dB efficiency. A Faital Pro HP1030 only 3 cubic feet but loses 3dB efficiency.
This assumes decent motors on each woofer. A subwoofer that isn't sensitive because of high moving mass but has a strong motor will work well in a smaller cab but need more power. A subwoofer that has a weak motor (and high electrical Q) isn't much good in this regard but I'm assuming you are not using Skytec woofers.
As you are not dealing with subwoofer only the midband efficiency is also important, but for the lower frequencies the graph is enclosure dependent.
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I Own the 15MB700 and it sounds good with an ordinary speaker cab.
Mine are working with Beyma FD250 crossovers and Selenium compression drivers. First they were working with Eighteensound ND90 or 91 ? but the Seleniums have more sensitivity and so I could pad them down in the crossover in order to protect them. The coils are also cheaper. They usually play with 500W RMS amps and take some abuse.
I don't know if the JBL's have some sort of EQ or Bass boosting function but it is a good driver.
Mine are working with Beyma FD250 crossovers and Selenium compression drivers. First they were working with Eighteensound ND90 or 91 ? but the Seleniums have more sensitivity and so I could pad them down in the crossover in order to protect them. The coils are also cheaper. They usually play with 500W RMS amps and take some abuse.
I don't know if the JBL's have some sort of EQ or Bass boosting function but it is a good driver.
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