Hi Forum members,
I am seeking your help on using Beyma 18p1000fev2 subwoofer for home theater. Is it good idea to tune the box lower, say closer to 22hz? It's for home theater. Spec can be found below
https://usspeaker.com/beyma 18P1000feV2-1.htm
I am seeking your help on using Beyma 18p1000fev2 subwoofer for home theater. Is it good idea to tune the box lower, say closer to 22hz? It's for home theater. Spec can be found below
https://usspeaker.com/beyma 18P1000feV2-1.htm
The 18p1000fev2 has plenty of power handling, but little Xmax, it runs out of excursion well below it's power handling.
When box tuning (Fb) is dropped below it's Fs of 33Hz in the same net volume enclosure with an Fb of 22Hz, the (clean) low end potential drops considerably, in the examples below from around 118dB@30Hs to 112dB@20Hz.
And for comparison, a pair of Eminence LAB12 drivers in the same box and Fb:
Note the voltage ("Eg" in the Hornresp simulations) to reach Xmax is far less on the lower impedance LAB12s.
A HP (low-cut) filter below Fb should be used to avoid excessive excursion which potentially could tear up suspension parts.
Art
Might be because your sim has the LABs wired in parallel, which is going to present a low impedance to the amp. What if they're wired in series?
Thank you for your response.
May i know the power signal at which this simulation was done? Also, is the 112db @20hz is without any HPF's. Could we expect a 5 db loss after applying HF filters? Since I do not expect it to output at reference levels at 20hz, will it serve the purpose to the least? I am looking to avoid a disappointment after I realise that this driver may not capable enough for HT use.
Thanks
Greets!
Another (sub) woofer meant for Fb > Fs, so will need a huge extended bass shelf (EBS) or TQWT alignment to tune low with barely enough SPL for THX's 115 dB/20 Hz and even then will need to be at least against a wall (1 pi space) and in a corner (0.5 pi) to shrink it a bit to get it at the listening position (LP) unless it's positioned near it; so at this point can the sub be used as a sofa/whatever riser or high aspect ratio box behind the LP?
The "power signal" is voltage ( voltage is "Eg" in the Hornresp simulations).
Voltage squared divided by the impedance (resistance in Ohms) (divided by the number of drivers) equals power in watts.
The impedance curve of a ported cabinet will always be at minimum at Fb, with higher peaks on either side, so power drawn is maximum at Fb, dropping on either side.
A BW24 HPF filter set around 10% below Fb will keep excursion under control with hardly any loss at Fb, under -3dB at 20Hz with a 19Hz HP and 22Hz Fb.
Whether you will be disappointed with less than "reference level" is subjective, 112dB (2pi, half space) would be a lot (like 15dB..) more than I'd typically use in a usual sized "home theater", while others are not happy without seismic levels.
Art
Thanks for your time and explanation.
I guess had never listened LFE that loud in close proximity (home environment) and probably unaware of what it would be like to experience 100+ db but going by your high confidence level response, it sounds promising to build an enclosure around 10 cu.ft to get a good decent bass.
Regarding cone excursion, I saw it exceeding at 2 places. 1 around 20hz and another between 27 and 46 hz. Now, applying just HP around Fb (22) only alleviates the exceeding excursion little bit but it does not bring under its limits (8mm). Similarly, b/w 27 and 46 hz, it exceeds above 9mm - could you explain how does it work in real time scenario where the driver exceeding 1 or 2 mm above its limits (xmax). Does it depends on which freq range whereit exceeds that decides whether its a risk for the driver, (i.e. able to sustain the excursion violation? like around 20hz high risk and and above 30hz low risk) or Is it fine if it exceeds beyond its limit for 1mm or 2mm and wont cause damage (at half power)? Below image will better explain my query
Also, would you please suggest any enclosure model (material resources) that you think might produce the result (at least closest to what you judged) for this driver?
Thanks
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Thanks GM
It's an open square sized hall (441 sq.ft) with no obstacles for the listeners. The only placement option I have (given the enclosure size it will need), is the corner against the wall. I am worried about few spots where it may sound boomy/unclear bass? Regarding EBS or TQWT, do you know of any resources that depicts a model for a similar driver like this that I can take a look for my build? I have never listened to an 18 inch HT sub woofer and I hope this driver wont let my least expectations down (provided that I give what this driver needs in terms of build)
Xmax isn't typically the hard limit you seem to be implying. It's normally an indicator of the range for which the magnetic system is linear. Some drivers play cleanly beyond Xmax, while others don't. From footnote 4 of Beyma's spec sheet:
"The Xmax is calculated as (Lvc - Hag)/2 + (Hag/3,5), where Lvc is the voice coil length and Hag is the air gap height."
Some drivers have little extra room in the suspension beyond Xmax, but most have a decent amount. Some have a lot. Xmech is often the term used to indicate the mechanical limit of the driver. In this case, Beyma used the term Xdamage, and it is quite large compared to Xmax for this driver (though Xmax is normally a peak measurement, and Xdamage in this case is peak-to-peak).
As mattstat wrote, don't worry about a few mm beyond Xmax, but pay attention to Xmech.
The Hornresp simulation volumes could be used to make an enclosure that would measure very similarly if built in any usual height/width/depth configuration.
Art
You're welcome!
Right at the same size as mine, though it opens into other spaces making my 1st 'room' mode ~1130/2/46 ft = ~12.28 Hz, so no room gain of use whereas yours is ~2x, but still none of use for full THX, hence the need for the sub system to do it all, especially if wanting to do low B pipe organ symphonies (my main reason) and all of the infrasonic BW on many movies.
Not quite sure what you're asking for, though have only been a 'talking head' on the forums as my DIY 'career' abruptly ended in 1990 and active HT design in '96 when I joined the online DIY community, such as it was; more like the Wild, Wild West than worldwide web, so can't point to any builds of mine, much less comparisons or measurements since I could never have justified the $30+k the local Altec distributor had invested in his rolling coat closet size instrument rack.
Regardless, the Acoustic Elegance TD18H w/Apollo Upgrade shows you where my head's at WRT the sort of quality driver, performance I demand for myself.
Looking at Art's EBS, a TQWT of similar size, tuning will be a bit better damped acoustically due to being basically a huge tapered vent with a larger terminus (Ap), but some judicious internal damping audibly evens them out, so looks good to go if its performance potential is sufficient.
A well-designed port will considerably improve output, since the speaker itself is producing little output at these frequencies. Always start with a port area similar to Sd - about 35cm diameter in this case - and compromise down to a size which fits the enclosure. Try to ensure the port is no longer than twice its diameter, and keep flow symmetry as balanced as possible; a piece of drainpipe or two stuck in the baffle is just lazy and not a good option... A properly proportioned flare radius will also pay dividends in terms of increased output and also reduce distortion. The improvements to be had from a decent port are not inconsiderable.
If you want a really great-sounding sub, go Q=0.5 sealed, but be prepared for low efficiency, lots of EQ, and heaps of power. A pair of sealed (60l enclosure) B&C 18PZB100 (700W AES, 8mm Xmax) in parallel and 2kW has proved more than adequate for a small pub PA, producing enough LF output to hear turntable rumble, which required an HPF to remove it. Mounting the driver 'in reverse' like some of our car audio cousins with the magnet outside the enclosure allows for exceptional cooling and reduced power compression.
If you want a really great-sounding sub, go Q=0.5 sealed, but be prepared for low efficiency, lots of EQ, and heaps of power. A pair of sealed (60l enclosure) B&C 18PZB100 (700W AES, 8mm Xmax) in parallel and 2kW has proved more than adequate for a small pub PA, producing enough LF output to hear turntable rumble, which required an HPF to remove it. Mounting the driver 'in reverse' like some of our car audio cousins with the magnet outside the enclosure allows for exceptional cooling and reduced power compression.
True, but Art's modest sized vent is already nearly 30" long, so a moot point short of switching to a pair of PRs or my preferred inverse TQWT.
For sure and wish we all could afford large enough sealed systems, especially when enough drivers can be used to get the acoustic efficiency to mimic at least a truncated compression horn down low, but just a pipe dream for the vast majority of folks.
For sure and wish we all could afford large enough sealed systems, especially when enough drivers can be used to get the acoustic efficiency to mimic at least a truncated compression horn down low, but just a pipe dream for the vast majority of folks.
Apologies everyone for not being active on this thread as I have been busy with office work. Thank you @GM, @MrKlinky for your valuable responses. So the latest development on this is I have not heard any news from the local dealer on the Beyma driver, therefore, I am now inclined to think other alternatives, which is to get 4 x 12 inch subwoofers which are made in India (link below) and build 2 ported enclosures (EBS - slightly bigger) inheriting 2 drivers each to be placed on either side of the room.
Although I would prefer 18 inch sub, availability and selection of right drivers are a major concern where I live.
Although it looks great on winisd, it would be good to have it reviewed by experts here so that I am aware of any limitations that I need to be aware about before planning build. The TS parameters is attached here and can also be found in the link.
http://iwaispeakers.com/product-detail/12-long-throw-subwoofer-4ω-200w/
Although I would prefer 18 inch sub, availability and selection of right drivers are a major concern where I live.
Although it looks great on winisd, it would be good to have it reviewed by experts here so that I am aware of any limitations that I need to be aware about before planning build. The TS parameters is attached here and can also be found in the link.
http://iwaispeakers.com/product-detail/12-long-throw-subwoofer-4ω-200w/
Well, frame size wise looks like you got a 12" * (4)^0.5 = 24" dia.. 
and the various specs line up close enough, so any sim will be as good as the specs actually are, i.e. seen some really far off India made drivers over the decades here, so 'caveat emptor' applies.
Anyway, another one that ideally needs to be tuned > Fs to get much power handling and a single driver T/S max flat alignment is ~142.24 L tuned to ~22.48 Hz, but can only handle ~108 dB/m/100 W to get down to ~20 Hz/2pi plus with the relatively tiny cab it takes a 175 cm^2 x 60.1 cm long vent to do it at an acceptable vent mach.
Of course if up against a wall or better still, in a corner, it will be more and just build two speakers in one box to double again (+6 dB).
In short, no need for a shelved EBS, you're good to go as is as long as the specs are ~accurate.
and the various specs line up close enough, so any sim will be as good as the specs actually are, i.e. seen some really far off India made drivers over the decades here, so 'caveat emptor' applies.Anyway, another one that ideally needs to be tuned > Fs to get much power handling and a single driver T/S max flat alignment is ~142.24 L tuned to ~22.48 Hz, but can only handle ~108 dB/m/100 W to get down to ~20 Hz/2pi plus with the relatively tiny cab it takes a 175 cm^2 x 60.1 cm long vent to do it at an acceptable vent mach.
Of course if up against a wall or better still, in a corner, it will be more and just build two speakers in one box to double again (+6 dB).
In short, no need for a shelved EBS, you're good to go as is as long as the specs are ~accurate.