Subwoofer recommendations

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Hi, I am looking for help to build some subwoofer to meet my goals.
I want 2/3 subwoofers for mainly movies but some music. They need to blend with mk speakers which will play down to 80 but ideally I would want a xo of 100/120.
The room is 1500 ft3 and is irregular shaped and does not have a ven response around the room but does give significant room gain from 50 down. There is no one position in the room that gives a flat response even after eq
My limitations are that the subs need to be small. There is one spot where i could maybe go to 80l but the offer placement locations will be far more limited, say 50l.
I have an amplifier with xt32 (for dual subs), and a minidsp 4x2 for eq. I have an inuke 6000 and a couple of minidsp pwr 125 plate amps that are currently surplace and I have a single fi q15 driver. I can sell these if not used in new set up.
I favour tight accurate bass over outright spl.
I would prefer just 2 subs to keep it simple but not sure two 50l subs will be enough. Whilst one of them subs can be bigger im not sure how best to intergrate ie use drivers from the same range but say one 12 inch and one 15/18.
I have heard a bms 1860 in a sealed cabinet and was hugely impressed by the quality of the base but could only have one of these in a slightly undersized cabinet.
I currently have a MK V12 sub and I want to improve over that.
I am in europe so prices for faital/B&C/BMS etc are quite good compared to the price daytons etc will cost.
My woodwork skills are not great but I have made some sealed boxes previously.
Any advise as to where you would start in my situation would be greatly appreciated.
 
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The room is 1500 square meters and is irregular shaped and does not have a ven response around the room but does give significant room gain from 50 down. There is no one position in the room that gives a flat response even after eq
My limitations are that the subs need to be small.
1500 square meters and small subs don't go together well ;).

150 square meters, small sealed subs with EQ will "get 'er done"...
 

GM

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Joined 2003
OK, assuming 8 ft ceilings:

~1500/8 = 187.5 ft^2
~187.5^0.5 = ~13.69 ft square
~1128.6 ft_sec/13.69 = ~41.2 Hz

Considering rooms tend to be somewhat leaky, ~50 Hz-up room gain is pretty good, so multiple small sealed + DSP is doable as Art noted.

The MK V12 sub appears to be ~50 L net with a claimed +/- 2 dB/20 Hz = very low efficiency, so ideally need < ~20 Hz Fs drivers at minimum. If you need them to be <50 L gross, then not sure there's any suitable drivers short of custom made as the MK's likely is.

Anyway, not familiar with what all's available, so leave it to others to help narrow it down.

GM
 
Thanks GM. When I said at least as good as my current mk sub I was talking about sound quality. When I have heard high end systems its the speed of the bass that impresses me along with some higher bass punch. Its them qualities I find missing currently and i think a large part is the room and where we sit and subs can be located.
My vague idea was that more than one sub will make the natural bass in the room far more even before eq. Two subs will also increase headroom so will naturally decrease distortion. If I was to keep the MK sub and build 1 or 2 other subs I would not want them to have a slower response (transient response?) as I would imagine the listening experience will equal the sub with the most overhang. Sorry for my terminology which may be a little wrong.
Driver wise I love the sound of the big BMS I heard but I could only have one of them in a undersized box (80l). They do smaller woofers but they are getting further away the function of a sealed 20-120hz subwoofer. Maybe keeping it simple with 2 Dayton Audio RSS315HO-4 or maybe a mix of the 12 inch and 15 inch version maybe the way to go as that is something that is designed to go in a small box.
 
I have been looking at a few options.
The first is 2 Alpine swr-1522d in 55l boxes for a qtc of .7. They seem to have a pretty flat response and are about the cheapest option. I'm not sure about the sound quality and how they will sound using a crossover higher than 100.
Next are 2 BMS 15n840 in a 40l box for a qtc of .664. There output cant match the Alpines below 40 but are very strong above that and look to have good build quality and think they will crossover nice and high to blend with my inwall MK speakers.
Another option is to have just one BMS 18n862 in about 80l which gives a qtc .8 which is higher than I would want but I have heard a pair of these and it is exactly the sound I am after. If I was to get one of these I think I will still need another subwoofer to get an even response between 60 and a 100 but I would build it first and try it.
The last option is 2 B&C 15ds115 which sounds like it is a quality driver. Unfortunately I cant seem to get the specs to reconcile in winisd. Can anyone help out here?
I would be using a inuke nu6000 to power all of the above
My preference is to get as good as possible now to stop me wanting to upgrade again in 6 months. Any comments appreciated
 

GM

Member
Joined 2003
You're welcome!

Just saw this.......... OK you're like me, got to have heart attack fast transients, especially if mating to horns like I do. 'Fastest' sealed is transient perfect 0.5 Qtc. Odds are your MK is max flat = ~0.7 Qtc, i.e. not good enough for me and of course the room is mucking with it.

Rooms are 3D, so ideally need at least one in each plane and normally at a room odd harmonic and often more to average it all out. Main thing is stay out of nulls [even order] as it will just suck the amp dry doing nothing useful.

Ditto the LP, if setting in a null it's game over.

Anyway, 0.5 Qtc is a naturally large cab relative to typical sealed, so the name of the game now that DSP is so cheap is put the lowest Fs, biggest, most powerful [highest Xmax] subwoofer that will fit in the desired size cab, budget and DSP it to a 0.5 Qtc with the trade off of reduced efficiency. Not many 'free lunches' in audio, got to rob 'Peter to pay Paul', so in speaker design we're always trading eff. for BW.

Hopefully you can DSP the MK since it will likely be the 'slowpoke' once done, otherwise just tune the new ones to match it.

GM
 

GM

Member
Joined 2003
The last option is 2 B&C 15ds115 which sounds like it is a quality driver. Unfortunately I cant seem to get the specs to reconcile in winisd. Can anyone help out here?

Been a long time now, but was proficient with its Pro and Pro 0.7 replacement, so what's the problem? Hornresp
has no problems with it

Regardless, why bother? You want an Fs at/below the lowest you want to reproduce, so with a 33 Hz Fs, a nonstarter.

GM
 
Ideally i would want to aim for a qtc of .5 but size restraints seem to make that a non starter. My issue is I want a lot from one system and need to make compromises but its getting the right balance. I would still want to hit reference levels for peaks (movies), be able to crossover at 100 or above, have sufficient subwoofer headroom to keep distortion low whilst also having a great transient response. All in a tiny cab please!
I think realistically my room is not good and even with 2 ultra damped subwoofers the room would still make them sound bad without plenty of eq but I want to do the best I can.
I have looked at pa subs with higher fs. My thinking was that when modeled they still have output into the 20's that are higher than most traditional subs in the same cab size even thought they have fs in the low 20's. However after 40 they have substantially more output which I though matched the room gain I have from 40 down. Maybe its the wrong approach.
 
OK; high SQ 115 dB/LP for THX, so as many inefficient sealed subs as it takes spread around the room to help with room modes, though most folks are fine with 115 dB/m.

Not normally a good plan, DSP or not, though Bagend's ELF system, which only operates below Fs, maybe what you want, but I'm sticking by my proposed sub system alignment ;): Sub-Woofer Controller


GM
 
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Joined 2008
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Hi GM,

Looking up your mention of Qtc, a few Googled hits make it appear some equate Qtc with Qts, and looking for calculators I couldn't find one that inputs the parameters I have available for the driver I don't have but have questions about (Tad TL-1801).
This brings two questions, 1) Easy way to calculate Qtc from generally available TS Parameters?,

and 2) Is there such a thing as a comprehensive speaker workshop where one can go to listen to comparisons of speakers put together specifically for making clear the differences made by changing a TS parameter? So many speaker builders around, I imagine it could turn a profit, maybe.

I thought this after seeing some forum posts saying they'd opt for Qtc of .9 or 1.0 . Personally I will just never get to build enough to begin to hear what specific changes do unless going to some kind of intensive learning session.
Just thoughts.


Thanks, with Apologies to OP for the diversion.
 
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Thanks !

One more basic question. The graph on the page you linked shows frequency response for different Qtc but I see that others online refer to Qtc as an indicator of damping ( eg. "value for the damping provided for a driver in a sealed enclosure").

Question is: Is that a correct interpretation and if so what's the best way to think of the link between damping and frequency response? I think of damping as a kind of tightness or pressure against oscillatory peaks. Is the idea that Qtc lowers LF amplitude solely by restricting its peaks thus forcing the frequency upward?

Thanks again and more apologies to the OP.
 
You're welcome!

Right, Qtc is a sealed system's quality factor = damping factor or more correctly: Q = ratio of energy stored to energy dissipated per cycle.

Right, you're always trading acoustic efficiency for BW, so the smaller the cab, the higher its Qtc and the more narrow its 'flat' BW.

GM
 
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