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If I punch the height it will have lower peak/dome in the response, it would be more close to 70Hz. I can blow up velocity some and lower the tune to say in the form factor. Efficiency really picks up once you are a little above the Fs of the sub, in this case 30Hz. The extension would be worth it if you plan on running just the MBMs for music purposes. If you area always running the 24"s you will probably be crossing over between subs somewhere between 40Hz and 50Hz.
This will be exclusively HT use. I only use the back 24s for music. I'll differ to your judgement on this. These will be crossed with my 24s, probably in the 50-60Hz range. As for cabinet complexity, I'm not worried about it. I'm sure I can figure a way to build whatever you come up with.
 
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Also, the 21s are a done deal. I'm trading some work for @chadsmith013 LaVoce.
 
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Discussion Starter #603
The 20Hz to 30Hz range is just an awkward place. You can a little efficiency with a high 20s tune, but not much of anything. Once you get north of 30Hz the efficiency becomes much more apparent. I would run the short Mini horn in a box and then tune the back to 17 or 18Hz so it runs full range or just go for a true PA/MBM tune. 60x25.5x24 using most of that for low end should work well. The port might reach the hatch sooner than ideal. What kind of power do you plan on running?
 

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The 20Hz to 30Hz range is just an awkward place. You can a little efficiency with a high 20s tune, but not much of anything. Once you get north of 30Hz the efficiency becomes much more apparent. I would run the short Mini horn in a box and then tune the back to 17 or 18Hz so it runs full range or just go for a true PA/MBM tune. 60x25.5x24 using most of that for low end should work well. The port might reach the hatch sooner than ideal. What kind of power do you plan on running?
They will be on a bridged XLS2502
 

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Discussion Starter #605
They will be on a bridged XLS2502

Based on the spec sheet it looks like the XLS2502 runs out of voltage around 111 volts and current at 24.5amps. The SAN is 5.2 Ohms so the amp at 111 volts should be pushing 21.35 amps in to the sub or 2370 in watts. I am assuming one amp per sub on this.



Back to cabinets, I would A: doing something full range, what is the tune on the 24" cabinets? B: go with a Mini MBM tuned to the mid to upper 30s. If you look at the Mini MBM notice it only gains 2db in efficiency with a 28Hz tune vs a 20Hz tune. Go under 20Hz or go over 30Hz would be my suggestion. Running subs with much different tunes in the same frequency domain can be done, but it is a lot of measuring tweaking and back and forth.
 

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When it comes to sustained versus power ratings and SPL, what kind of numbers usually apply in actual use? I know this is a matter of personal preference, but should I be planning/modeling around power required for sustained 120dB output when I'm going to be listening at 80dB with ~100dB peaks?
 

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Discussion Starter #607
When it comes to sustained versus power ratings and SPL, what kind of numbers usually apply in actual use? I know this is a matter of personal preference, but should I be planning/modeling around power required for sustained 120dB output when I'm going to be listening at 80dB with ~100dB peaks?

Content is for the most part very dynamic, unlike sinewaves that will push a power forever. Most of the time the subs might only be running at 10s of watts if that. Music can push things more consistently than movie content. The dynamics in movies can require a good amount of firepower, but a lot of that is based on how the room is working for or against you. Space considerations should be taken into account. A couple TBW100s in Mini V3s should be more than enough for most people... If you are a core bass head just go straight to LFEs or V4s.
 

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Based on the spec sheet it looks like the XLS2502 runs out of voltage around 111 volts and current at 24.5amps. The SAN is 5.2 Ohms so the amp at 111 volts should be pushing 21.35 amps in to the sub or 2370 in watts. I am assuming one amp per sub on this.



Back to cabinets, I would A: doing something full range, what is the tune on the 24" cabinets? B: go with a Mini MBM tuned to the mid to upper 30s. If you look at the Mini MBM notice it only gains 2db in efficiency with a 28Hz tune vs a 20Hz tune. Go under 20Hz or go over 30Hz would be my suggestion. Running subs with much different tunes in the same frequency domain can be done, but it is a lot of measuring tweaking and back and forth.
I only have one XLS2502. I'll cross that bridge later.

The 24s are sealed, 11ft^3 net on an NU12000
 

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Discussion Starter #609
I only have one XLS2502. I'll cross that bridge later.

The 24s are sealed, 11ft^3 net on an NU12000

That is a tough call, to get the 24"s to work with vented subs a 10Hz 8th order filter might be required if running them in a shared range. That would be a shame with those 24"s cutting off that hard and quick. If you can look at Chris's adventure with his HT18s sealed trying to get them to play nice with the vented Mini Devs. If you are running crossovers at 50 or 60Hz smaller boxes optimized for the range look good. On that sim with 2000 watts they were only pushing 10.6mm of excursion, there is a lot more left in the tank.
 

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That is a tough call, to get the 24"s to work with vented subs a 10Hz 8th order filter might be required if running them in a shared range. That would be a shame with those 24"s cutting off that hard and quick. If you can look at Chris's adventure with his HT18s sealed trying to get them to play nice with the vented Mini Devs. If you are running crossovers at 50 or 60Hz smaller boxes optimized for the range look good. On that sim with 2000 watts they were only pushing 10.6mm of excursion, there is a lot more left in the tank.


He might be able to cross the 21’s 10hz or so over port tune as well. In my case, I was trying to maximize use of the dev’s as they were far more powerful than the sealed.
His case looks opposite.
@tarponater, have you integrated sealed and ported designs before?

Chris
 

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That is a tough call, to get the 24"s to work with vented subs a 10Hz 8th order filter might be required if running them in a shared range. That would be a shame with those 24"s cutting off that hard and quick. If you can look at Chris's adventure with his HT18s sealed trying to get them to play nice with the vented Mini Devs. If you are running crossovers at 50 or 60Hz smaller boxes optimized for the range look good. On that sim with 2000 watts they were only pushing 10.6mm of excursion, there is a lot more left in the tank.
I do not plan on running them in a shared range. The plan is roll the 24s off around 60Hz or lower, then let the Devastators take over from there. However, ported 24s is not an option in my theater, so if something like that wouldn't result in a good response then I'll just stick with the three 24s. As much as I want those Devastators, I'm definitely not going to take a step back doing this.
 

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Discussion Starter #612 (Edited)
I do not plan on running them in a shared range. The plan is roll the 24s off around 60Hz or lower, then let the Devastators take over from there. However, ported 24s is not an option in my theater, so if something like that wouldn't result in a good response then I'll just stick with the three 24s. As much as I want those Devastators, I'm definitely not going to take a step back doing this.

If you have been to a concert where your body is just getting beat into submission the frequencies at play are a lot higher than you think. I know it seems like a waste using 21"s for mid bass, but that is really what they are designed to do. They will add a lot more than you might suspect. @Jk7.2 has first hand experience here and a great thread - https://www.avsforum.com/forum/155-diy-speakers-subs/3100010-dual-devastator-micro-build.html


Edit: you also have to factor in particles being pushed around the room. The QW on the MBM will add a lot in that department, especially if the BR chamber vent is resonating near the crossover point.
 

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Discussion Starter #613

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He might be able to cross the 21’s 10hz or so over port tune as well. In my case, I was trying to maximize use of the dev’s as they were far more powerful than the sealed.
His case looks opposite.
@tarponater, have you integrated sealed and ported designs before?

Chris
I have mixed ported and sealed before and really haven't had much problem with integration. I have a nasty mountain range around 80-120Hz that is always there, no matter what kind of subs I have. So far, the smoothest response has been with five UM18 Full Marties tuned to 15 Hz.
 

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Content is for the most part very dynamic, unlike sinewaves that will push a power forever. Most of the time the subs might only be running at 10s of watts if that. Music can push things more consistently than movie content. The dynamics in movies can require a good amount of firepower, but a lot of that is based on how the room is working for or against you. Space considerations should be taken into account. A couple TBW100s in Mini V3s should be more than enough for most people... If you are a core bass head just go straight to LFEs or V4s.
My question was less about the choice of sub design, and more about how much amplification is needed to support one in my use case. I'm talking about changing the SPL variable instead of the wattage in order to match my listening level. But to switch back to modelling based on amplification power, what's the output look like when you halve the power from 2000 W to 1000 W? 3 dB drop?
 

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Discussion Starter #616
My question was less about the choice of sub design, and more about how much amplification is needed to support one in my use case. I'm talking about changing the SPL variable instead of the wattage in order to match my listening level. But to switch back to modelling based on amplification power, what's the output look like when you halve the power from 2000 W to 1000 W? 3 dB drop?
Yep, keep dropping 3db for each time power is cut in half.
 

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He might be able to cross the 21’s 10hz or so over port tune as well. In my case, I was trying to maximize use of the dev’s as they were far more powerful than the sealed.
His case looks opposite.
@tarponater, have you integrated sealed and ported designs before?

Chris
If I can't figure out a way to make ported 24s, then it looks like there is another option. Like you said, the 24s will be handling ULF leaving mid and upper bass to the Devastators. @Red Five said to either tune the Devastators to under 20Hz or over 30Hz. Your suggestion was to cut the Devastators off about 10Hz over tune. What if I did an 18-19Hz tune and cut them off at 30Hz? Then cut the 24s off around 40Hz. Or I could do a 30Hz tune, cut them off at 40Hz and cut the 24s off around 50Hz.
 

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If I can't figure out a way to make ported 24s, then it looks like there is another option. Like you said, the 24s will be handling ULF leaving mid and upper bass to the Devastators. @Red Five said to either tune the Devastators to under 20Hz or over 30Hz. Your suggestion was to cut the Devastators off about 10Hz over tune. What if I did an 18-19Hz tune and cut them off at 30Hz? Then cut the 24s off around 40Hz. Or I could do a 30Hz tune, cut them off at 40Hz and cut the 24s off around 50Hz.


Making ported 24’s will take some space, lol. I don’t know that its necessary, though COULD make integration easier. I’d base that more on whether they have enough output sealed, or you want more. A LLT hs24 is going to be a massive box though.

Imo, either the 18-20hz tune or the mbm will work. The mbm will be a much smaller, simpler enclosure.
The 18-20hz will probably need to be the hybrid box John and I were talking about earlier.

Since you don’t plan to run both full-range, the mbm will be a much simpler solution. You will end up with a bigger version of what jared, @Jk7.2 was running. In his case, he was using 15” dev mbm’s with ported hst18’s.

The only two reasons to go with the 18-20hz tune would be to add output from 30hz up, or to or to make the dev’s more useful as a stand-alone sub, expecting future system changes.

The mbm config will have higher output near crossover frequency due to the port tune, upper end will be the same on both with the same length QW.

Chris
 

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Making ported 24’s will take some space, lol. I don’t know that its necessary, though COULD make integration easier. I’d base that more on whether they have enough output sealed, or you want more. A LLT hs24 is going to be a massive box though.

Imo, either the 18-20hz tune or the mbm will work. The mbm will be a much smaller, simpler enclosure.
The 18-20hz will probably need to be the hybrid box John and I were talking about earlier.

Since you don’t plan to run both full-range, the mbm will be a much simpler solution. You will end up with a bigger version of what jared, @Jk7.2 was running. In his case, he was using 15” dev mbm’s with ported hst18’s.

The only two reasons to go with the 18-20hz tune would be to add output from 30hz up, or to or to make the dev’s more useful as a stand-alone sub, expecting future system changes.

The mbm config will have higher output near crossover frequency due to the port tune, upper end will be the same on both with the same length QW.

Chris
It sounds like the MBM is the right option for what I'm looking to achieve. Although the 24s are excellent in the mid bass range, I know they can't compare to the PA21s. Is post 595 the MBM design you are referring to?
 
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