Bms 4594: Spl - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 14 Old 06-13-2019, 12:42 PM - Thread Starter
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Bms 4594: Spl

I'm not clear on how much output you can expect out of a BMS 4594 coaxial driver. I'm looking for the output @RMS . Specs listed in picture.

This would put the midrange-driver at 139.8 dB (150W AES) and the HF-driver at 137 dB (80W AES), with a total of 141.60 dB (230W AES) and a peak output of 149.2 dB (1350W).

Anyone can confirm my calculations? Seems to be wayyyy higher than other drivers. Or am I wrong to asume AES is the same as RMS (or at least close)?
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post #2 of 14 Old 06-13-2019, 01:11 PM
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The AES/RMS values are realistic for output. Those Peak numbers are not at all realistic, as at those power levels distortion and driver damage is a reality. Keep in mind, and refer to the BMS Limitations, that the RMS power for the Mid driver decreases significantly as crossover point is lowered. I dont recall more than that, but BMS will provide that information.

These are excellent drivers, and I can attest to their capability, sitting 9 feet from them. Doesnt take much at all to hit reference.


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post #3 of 14 Old 06-13-2019, 02:01 PM
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Loud.
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post #4 of 14 Old 06-13-2019, 02:53 PM
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Originally Posted by lukeamdman View Post
Loud.


My last professional hearing exam, I’m not gonna lie, I was a little nervous!

Limiters are your friend with these.


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post #5 of 14 Old 06-13-2019, 04:07 PM - Thread Starter
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Quote:
Originally Posted by FOHTech View Post
The AES/RMS values are realistic for output. Those Peak numbers are not at all realistic, as at those power levels distortion and driver damage is a reality. Keep in mind, and refer to the BMS Limitations, that the RMS power for the Mid driver decreases significantly as crossover point is lowered. I dont recall more than that, but BMS will provide that information.

These are excellent drivers, and I can attest to their capability, sitting 9 feet from them. Doesnt take much at all to hit reference.


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Originally Posted by lukeamdman View Post
Loud.
Quote:
Originally Posted by FOHTech View Post
My last professional hearing exam, I’m not gonna lie, I was a little nervous!

Limiters are your friend with these.


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Haha, I figured my math was correct (I cheated and used online calculators), but wanted to be sure as I cant seem to find a lot of drivers that can get even close to the values.. I would be using them at 500hz, not 300hz, so I think I'm good. The spec sheet specifically says its 150W above 400hz, and 1000W peak above 500h, so I figure you are correct in that statement.

I'll be using them in a large synergy horn, and I am trying to match the HF output of the BMS with my woofers, quite the task (but definitely possible). 4x 15"or 18" woofers will do the trick. And no, that output is not meant for home use. The synergy will be a HiFi speaker, which I will use once in a while for PA stuff. All components will be HiFi prioritised, but where I can I will use high SPL options (more woofers= more SPL = less distortion aka win win for both scenarios). The BMS looks like a driver excellent for both HiFi and PA.

Completely off topic, but how would you match the 100-500hz range vs 500-20 000? 0dB difference? Or would the lower end need more SPL to match the high end (our ears being more sensitive to this range)? Subs would do the sub 100hz range.
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post #6 of 14 Old 06-14-2019, 02:24 AM
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Quote:
Originally Posted by Droogne View Post
Haha, I figured my math was correct (I cheated and used online calculators), but wanted to be sure as I cant seem to find a lot of drivers that can get even close to the values.. I would be using them at 500hz, not 300hz, so I think I'm good. The spec sheet specifically says its 150W above 400hz, and 1000W peak above 500h, so I figure you are correct in that statement.

I'll be using them in a large synergy horn, and I am trying to match the HF output of the BMS with my woofers, quite the task (but definitely possible). 4x 15"or 18" woofers will do the trick. And no, that output is not meant for home use. The synergy will be a HiFi speaker, which I will use once in a while for PA stuff. All components will be HiFi prioritised, but where I can I will use high SPL options (more woofers= more SPL = less distortion aka win win for both scenarios). The BMS looks like a driver excellent for both HiFi and PA.

Completely off topic, but how would you match the 100-500hz range vs 500-20 000? 0dB difference? Or would the lower end need more SPL to match the high end (our ears being more sensitive to this range)? Subs would do the sub 100hz range.
You would level match the 4594 with the woofer(s), it has so much overhead that limiting the HF spl would be better than to add more voltage to a woofer.
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post #7 of 14 Old 06-14-2019, 12:13 PM
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In my dBx processor I do all my active processing. I first use REW sweep the raw components (High and Low) , I use smooting and then in crossover settings attenuate the High Pass output until they are matched, resweep and repeat. I then double check with pink noise and it should be in the ballpark. Then you can begin the process of active processing for xover and PEQ. Use the amplifiers you will use in their installation. Changing amps will obviously throw off the levels post active processing.


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post #8 of 14 Old 06-14-2019, 01:49 PM - Thread Starter
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Originally Posted by Trimlock View Post
You would level match the 4594 with the woofer(s), it has so much overhead that limiting the HF spl would be better than to add more voltage to a woofer.
As I described on another forum:

'The 145dB is at RMS, so I would never use it at this level for very long stretches of time, but it is a good reference. It's gonna be my home synergies, but its a very large horn (10'8x75x45cm) and I will be making it a very high SPL contender too (something similar to a danley sound synergy like the SH96, but using a coaxial BMS instead of a combination of 4" mids and 1,4" HF driver), as to be able to use it at events we sometimes hold. Those events would never need 145dB ofcourse, but being able to run at 1% and at a distance of 100 meter still way over local SPL limits is a nice goal. Might also open the possibility to be used at bigger gigs. Also I will probably not reach the 145dB, or even be able to confirm that level, but its more about reserve etc.'

Bill Fitz Maurice however contends my calculation of 145dB, more to follow. He thinks it's rather 130-135db, in which case it will be very easy to match as I already have 2 15" woofers which can output this without any horn loading. In that case I would probably reconsider my low end goal for the woofers, and put in some subwoofers too, just to have a coherent source from at least 40-20 000 hz.
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post #9 of 14 Old 06-15-2019, 03:05 AM - Thread Starter
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As Bill Fitz Maurice correctly deduced, if you actually look at the graphs it looks like the middriver has 110dB/1W, not 118db/1W, and HF driver 113db/1W. So that comes down to 135dB tops. In any case, makes it a lot easier to match. 7dB difference means using less than half the woofers
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post #10 of 14 Old 06-15-2019, 03:36 AM
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at these SPL's the ear does flatten out nicely. There is only a few db difference in our ability to hear 50hz @ 120db vs tweeter region.


That said: it should be easy-enough to confirm the max SPL if you are willing to toast the speaker and measure it at a distance of 32meters so as not to max-out a UMIK-1.

Keep in mind that at these distances air starts to absorb highs more aggressively than lows. 50hz will travel 100ft without much attentuation, 1-20khz no so much... so you have to take that into consideration.

As I understand it, that's part of why they float the speakers:
a) because it gets them line-of-sight above all the bags-o-meat / drunk useless-eaters.
b) because then they can use more tweeters without frying the ears off the front row, yet still reaching the back row at the desired HF SPL vs the subwoofers (bass).
c) because it looks cool
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post #11 of 14 Old 06-15-2019, 06:25 AM
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Quote:
Originally Posted by Droogne View Post
As Bill Fitz Maurice correctly deduced, if you actually look at the graphs it looks like the middriver has 110dB/1W, not 118db/1W, and HF driver 113db/1W. So that comes down to 135dB tops. In any case, makes it a lot easier to match. 7dB difference means using less than half the woofers
Most mid woofers in the 100-500hz range won't break 100db at 2.87v, some will and having two will get you in better shape I'd think.


FP 15HF1010 is is about 97db
BC 15NDL88 is closer to 96db
18 sound 15MB700 is 97-100'ish (rising response)
Beyma actually has a couple that hovers around 100db 100-500hz


If you are going active this really isn't an issue, all the above woofers will get you great sound at ear piecing levels before heat becomes an issue and the BMS probably still won't see a full watt.
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post #12 of 14 Old 06-15-2019, 03:40 PM - Thread Starter
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Quote:
Originally Posted by Trimlock View Post
You would level match the 4594 with the woofer(s), it has so much overhead that limiting the HF spl would be better than to add more voltage to a woofer.
Quote:
Originally Posted by Trimlock View Post
Most mid woofers in the 100-500hz range won't break 100db at 2.87v, some will and having two will get you in better shape I'd think.


FP 15HF1010 is is about 97db
BC 15NDL88 is closer to 96db
18 sound 15MB700 is 97-100'ish (rising response)
Beyma actually has a couple that hovers around 100db 100-500hz


If you are going active this really isn't an issue, all the above woofers will get you great sound at ear piecing levels before heat becomes an issue and the BMS probably still won't see a full watt.
Yes, active crossovers so no issue there. The matching part is more about not having a weak link in the system. I also got the woofer part down Those are some great drivers you mention, but as I'm going for active crossovers I'm looking at output at RMS rather than sensitivity alone. Ofcourse sensitivity is extremely important for me as I dont want to buy expensive power amps to be able to get there. At the moment I have x2 Eminence Kappa 15A drivers (450W, 100,5dB/1W) I will use. In the future I'll upgrade probably. I looked at all available drivers on shop that sells almost all brands I know. As it looks I'll be able to easily match the HF, I might focus on extending the frequency response lower. Problem is I dont have hornloading down very low so I will always need subs. I can also keep the center-to-center distance between this synergy and a big horn sub (something like an Othorn) between 1/4th wavelength, so when the synergy is placed on the Othorn (with mouths next to each other) I can achieve a 20-20 000hz point source with incredible SPL and I would only need to use the synergy down to 120hz. Matching the compression driver and getting down to 120hz is no feat (I easily achieve this with my Eminence woofers).

Ofcourse I would never need this much output, but occasionally I will also be using them on several outside gigs where the extra SPL is welcome.
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post #13 of 14 Old 06-15-2019, 04:15 PM - Thread Starter
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Also, I think I might try to get the woofers to achieve an output 6-9dB higher than the HF due to the differential sensitivity of our hearing system.
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post #14 of 14 Old 06-16-2019, 01:03 AM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
at these SPL's the ear does flatten out nicely. There is only a few db difference in our ability to hear 50hz @ 120db vs tweeter region.


That said: it should be easy-enough to confirm the max SPL if you are willing to toast the speaker and measure it at a distance of 32meters so as not to max-out a UMIK-1.

good idea! Was already thinking about the max SPL of the UMIK-1, and didnt know what it was.

Keep in mind that at these distances air starts to absorb highs more aggressively than lows. 50hz will travel 100ft without much attentuation, 1-20khz no so much... so you have to take that into consideration.

Probably formulas for right?

As I understand it, that's part of why they float the speakers:
a) because it gets them line-of-sight above all the bags-o-meat / drunk useless-eaters.
b) because then they can use more tweeters without frying the ears off the front row, yet still reaching the back row at the desired HF SPL vs the subwoofers (bass).
c) because it looks cool
One of the great parts of this speaker is that it's a full range 1 box solution without a lot of compromises. Being 1 box it can easily be mounted if I want to.

Using the phon curve you included, how would I best match the woofers (100-500hz) with the HF range (500-20k)? 6-9dB?

Last edited by Droogne; 06-16-2019 at 01:07 AM.
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