BK XXLS400 max SPL?

TB Rich

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Just wondering if anyone knows the max SPL? If I used REW and did compression tests (not sure how currently) - is that what I would need to do to work it out myself?

Basically I still can't decide if I want to add another one for the co-lo boost. BK wanted £320 for an empty gloss black cab for me to swap my parts into, to which I think I'd be better off just buying a new one and then selling mine - the question is if I buy 2 at the same time!

My current EQ is:
doh.PNG


It's 'hot' because that was at master vol level of -22dB which is the about the most I ever listen at (usually -25dB). So it's my own form of dynamic volume really as my receiver doesn't have that feature. In actual listening it doesn't sound over-powered in the bass like it looks - though I fully appreciate if I started to up the master vol then it no doubt would!

I'm thinking that if I co-lo'd another BK next for it though, then assuming a 6dB boost then it could look like this black line:
revised.png


The green line being what I could EQ to now currently - however having tried similar prior then I've found that bass level to be slightly lack lustre when in the -20's volume.

The alternative to this is a single SB3000 or 1723 Sub 1S (both being gloss black and solving that problem too) - and hence really the what's the max SPL of an XXLS400? I think that would indicate as to what would be more effective, twin BK's or something else?

Cheers
 
Max spl at what frequency? You can use this online calculator to work out the max spl you can get from sealed boxes, using driver size and excursion. For the XXLS400 this is 12”, 12.5mm XMAX. So for example at 20hz the max spl is 96db, without room gain. Piston Excursion calculator
 
Thanks, I wasnt aware a specific frequency would be attributed to the number - but yeah makes sense.
I’ve just seen a few subs like the KEF Kube 12B for example that quotes 114dB max SPL. That seems quite impressive and I was wondering if the BK had a similar number or not I could compare with, and ultimately work out if adding a second was better than buying another single sub entirely. Guess it‘s not that easy!
 
Lower frequencies require higher amounts of excursion to reach the same spl as higher ones, so subs with limited excursion (all subs) will be able to hit different max spls at different frequencies. The calculator I linked to let’s you see what spls you can hit at what frequencies taking into account driver area and XMAX, these are absolute limits, anything over this isn’t possible unless of course the sub is ported. It’d be interesting to know how Kef arrived at 114db, and at what frequency this was tested at.
 
Depends on port tune of the sub too, I bet you could build a sub that is ported very high (say 100hz) , and test higher frequencies to get really high SPL....but not really a sub
 
You can’t use the calculator linked above for ported subs as it is entirely dependent on the driver box combo. Using the calculator, the Bk XXLS400 will be able to hit 115db at about 58hz.
 
Yep I’ve no idea what the 114dB is at, and also no idea what the excursion of the drive unit is. No doubt it’ll be something quite favourable and won’t be in the lower bass regions.

Are 2 x 400’s likely to be better combined output than a single say 1723 1S or SB3000?
I will need to rotate and measure my BK with the driver pointing out in various directions, at the mo it’s a DF and I think the response is good with no real nulls. So 2 x DF”s is certainly a safe bet compared to others that require the cone to face in a specific direction.
 
2x400s are likely to be able to provide more output than 1 of the other subs across the whole range, however why do you want to co locate? Your response has some fairly big peaks and dips which duals subs may solve, only when spread around the room.
 
I wouldn’t say it has big peaks and dips, it will look worse given the graph being out to 20k. If you take the ‘theoretical’ response being my drawn on black line, there’s a slight peak at 32hz (which I could flatten as is now), and there’s a dip at 40hz of 5-6dB so not really a null or not a bad one anyway. There’s likely again a null ish at 20hz, but it looks accentuated by the fact the sub is rolling off by then anyway, and it’s further accentuated given an obvious peak at 15hz where it would otherwise just be bass roll of to nothing - but that’s free bass ;)
The second sub as I understand it would be giving an extra 6dB, so in that 20hz region (and the 40hz one) means I‘d get it pretty flat there like the black line? At least that is my expectation of adding a second sub, if the reality is different then yeah maybe not such a good idea.

Having been thought a mini lounge re-shuffle, believe me there is no where else a sub could go! This position it’s in now is comprehensively better than were it was before across the entire range! And I’m only mostly thinking about adding another because the sub went into an 85cm wide gap and so there’s literally a tailored made space next to the current one for it!!

Like said I could EQ it to be flat like the green line, but to have the same impact I’d need to either run more master volume (which I don’t want) or start running the sub in the +dB region on the AVR.
I think the second sub if it will indeed sum as I hope, makes sense?
 
The likely scenario is that the peaks you see will rise by 6db and so will the nulls, so you could EQ to the black line and get it fairly flat. Hard to say really. What is the volume dial on the sub set at? Why can’t you EQ flat and just turn the sub gain dial up to compensate?
 
Yep if it pans out that way then great, that would give me a very flat bass response and at a decent level of ~90dB, whilst the mains are playing at ~75dB being my listening level.

If I EQ it flat now (i.e the green line) then its more like bass at ~82dB, which is why it’s lack lustre at my listening level. If I up’d my master volume to say -15dB then that would pick the bass up to a more substantial level again, but, I really don’t want my other 5 speakers playing at 80+!

I’m sure there’s probably a better argument for buying a modern AVR with dynamic volume....but, that’s not as fun as buying a second sub! And when I can use the miniDSP etc to engineer my own dynamic volume, it’s also not directly needed.
I’ll find budget for an AVR come Black Friday is the plan, but for now nothing appeals at current prices.

Also the sub is at 12 o’clock currently, so don’t really want to go higher, and in fact if I get a second I’d be able to likely trim them both back to around 11. There‘s a very slight hum when going to 12, which isn’t present below this.

I think you can use REW to simulate a total response based on 2 measurements, so if I ran 2 sweeps then I think that’d work? Something to look in to tomorrow anyway.
 
If it's all about excursion, then a cheap sub with lower wattage that can do 20mm of excrusion vs an expensive sub with a MASSIVE magnet and HUGE wattage can also do 20mm excursion, it's not actually going to give much difference is it?

Mono Plus for example can actually get away with 2.2cm excursion from what I can tell.
 
If it's all about excursion, then a cheap sub with lower wattage that can do 20mm of excrusion vs an expensive sub with a MASSIVE magnet and HUGE wattage can also do 20mm excursion, it's not actually going to give much difference is it?

Mono Plus for example can actually get away with 2.2cm excursion from what I can tell.
It’s all about displacement, which is a product of excursion and driver area. Excursion is distortion though, so it’s better to have more driver area than more excursion for the same spl, as this will result in lower distortion. The eminence lab 12 used in the mono plus had 13mm XMAX, so best not to push it more than this, XMAX is the point at which the driver becomes very non linear, so it’s mostly distortion after that.
 
Yep if it pans out that way then great, that would give me a very flat bass response and at a decent level of ~90dB, whilst the mains are playing at ~75dB being my listening level.

If I EQ it flat now (i.e the green line) then its more like bass at ~82dB, which is why it’s lack lustre at my listening level. If I up’d my master volume to say -15dB then that would pick the bass up to a more substantial level again, but, I really don’t want my other 5 speakers playing at 80+!

I’m sure there’s probably a better argument for buying a modern AVR with dynamic volume....but, that’s not as fun as buying a second sub! And when I can use the miniDSP etc to engineer my own dynamic volume, it’s also not directly needed.
I’ll find budget for an AVR come Black Friday is the plan, but for now nothing appeals at current prices.

Also the sub is at 12 o’clock currently, so don’t really want to go higher, and in fact if I get a second I’d be able to likely trim them both back to around 11. There‘s a very slight hum when going to 12, which isn’t present below this.


I think you mean dynamic EQ, rather than dynamic volume. Dynamic EQ increases the sub level relative to the other speakers as the volume drops. At reference (or close to) the levels would be even. If you only listen at one volume then a hot sub works and does what DEQ does, as you say. You don't need a minidsp for that though.

I think you can use REW to simulate a total response based on 2 measurements, so if I ran 2 sweeps then I think that’d work? Something to look in to tomorrow anyway.

You can do this. Task as many measurements as you like, with a timing reference, and you can use the alignment tool to see what the result would be with subs in each of those places. You can then affect the timing and level of each to see how that changes the response also.

If you're going to colocate you can do that now, just open the alignment tool and choose the same measurement in both boxes. It'll just give you a 6dB increase across the range though.

Also, I'm sure you're aware but it's worth bearing in mind that applying a filter to the 32Hz peak will also push down those nulls either side. Unless you're very lucky and the peak is the inverse of the filter shape (which it's not, the peak isn't symmetrical) you'll affect the response either side. You can definitely get close, but you won't be ruler flat in one filter. You can boost, but only up to a limited amount.
 
I think you mean dynamic EQ, rather than dynamic volume

Thanks, yes I just used the wrong term.

which it's not, the peak isn't symmetrical

As long as it works out better, it'll be flat enough. I'm already lightly manipulating some dB out of the 32hz area and adding some dB to the 40hz.

The plan would be, to not have any cuts once the 2nd sub is added. Whilst it might not work out to the black line I drew, it'll be hopefully fairly close and at any rate I can probably do cuts only. Along with pulling the gain to 11ish, I'm hoping I can have a lot of headroom. I think 2 x 400's in a 3.5x5.5m room should do that! And it'll be flat down to about 15hz thanks to that mode there :D
 
Also, I'm sure you're aware but it's worth bearing in mind that applying a filter to the 32Hz peak will also push down those nulls either side

Hi Conrad, my cables arrived today so I now have my miniDSP hooked into both my AVR and 2ch amp - so have had a revisit to my EQ results.

When doing the EQ for Movie use I think I am experiencing the issue you said (quoted above). I can't seem to EQ either side of the null, without, pulling the null down by a roughly similar amount.

Every time I tried I ended up with something like this, being the best of several attempts:
(no EQ red / flat-EQ attempt green)
eq-flat.png


No doubt that's probably a fair result for a single XXLS400? But I think a 2nd sub co-lo'd might actually just be a waste of money if it won't allow me to fill that ~40hz null afterall?

I've ended up configuring 2 configs on the DSP for movie use as below, the flat one which will work if I ever decided to listen near reference. And then the one I actually use in Purple.
I'd hazard a guess that the yellow markings I've added are about all a 2nd co-lo sub at best will probably allow for? - if that's the case probably seems a waste of money?
movies.png



For music use too, I've got one Config that's just providing some >30hz extension. - Most music this is not relevant to but it just fleshes out the bottom end slightly in listening. - I'm surprised I actually like it more than without (generally being a 'purest' for music!).

And the 2nd config I've done to really fill out from >150hz and down. This one does sound slightly excessive in listening, but it's more as a hooligan mode for certain music types! :D

But again based on below (given of course no EQ or cross over on mains etc for 2ch, so limited scope to flattening the whole thing out), I now don't see a need for a 2nd sub with music use either?!

Config 1 vs no sub:
music1.png


Config 2 vs no sub:
music2.png


Sorry, turned into a long post! - I've underlined the questions/my thoughts that a 2nd sub (co-lo'd) would be a waste of money - sound rational to you?!

Cheers
 
Well after the long post above convincing myself I didn't need a 2nd, I crumbled this evening and bought another XXLS400-DF in Gloss Black that they listed as 'grade-b' on eBay - it was the right colour (and a nice saving over the web price) so I can always sell my oak one pending what improvements I do or don't see after EQ.

I may see if I can move my speakers forward slightly and put one in the right corner for stereo bass to potentially fill that 40hz dip - I've never tried one in that corner so don't know if it will. But then I'll need that to be Gloss Black too.... and before long it'll be 3 🥴!
 
New receiver and you are done! One member got RX-A2080 for 750£ open box from RS. PT has few refurb units but the pricing is too high cause they don´t have any new Yamahas to compete with the prices so can keep them high. :(

Edit. I forgot those are too large for you! :facepalm:
 
New receiver and you are done! One member got RX-A2080 for 750£ open box from RS. PT has few refurb units but the pricing is too high cause they don´t have any new Yamahas to compete with the prices so can keep them high. :(

Edit. I forgot those are too large for you! :facepalm:

Yeah I really can't make a decision on that one. I've been looking and RS in my local branch have a refurb RX-V685 for £335 - seems a damn good deal and I guess does literally everything I need, if it was silver I think I'd bite.
At the back of my mind with that one I'm not sure it's 'high-end' enough to warrant replacing my old but to my ears very decent Marantz. I think if Covid hadn't affected supply then I'd be looking to get an SR6014, so with that said perhaps wait til an SR6015 is in the £8-900 region next year and strike then. I guess in case there's any issue with the HDMI 2.1 boards waiting wouldn't hurt either.

Yep I saw the RX-A2080 on RS - in Silver too! Got the tape measure out, however no chance! My unit is only 390mm deep and even if say subtract 60mm off the A2080 depth allowing for the volume knob and terminal depths, it's still going to be deeper than the unit itself :(
 
If you have or take measurements in each location you can place a sub (with a timing reference) I'll take a look at the file and see what you can do with alignment in the minidsp, if that would be useful.
 
If you have or take measurements in each location you can place a sub (with a timing reference) I'll take a look at the file and see what you can do with alignment in the minidsp, if that would be useful.

That’s a great offer thank you, would be great to have another pair of eyes.

I think I’ll need to buy a cheap usb soundcard with optical out if memory serves me right to be able to do a timing ref to a rear channel? (no HDMI on the AVR).
In all likely hood to save lounge upheaval I’ll co-locate it, run some PEQ to flattern it, and then do compression tests with 1 and 2 subs to see what the real world improvement is.

I have the current sub on 0deg phase, no timing adjust in the miniDSP and only a distance configured in the AVR - but in all the sweeps I’ve done with and without mains, it’s always been a wholesale improvment to total response so I don‘t think I have any timing errors?? (If that’s how you base it, as I assume timing errors so up has an induced null from the main to sub interaction?)
 
Yeah I really can't make a decision on that one. I've been looking and RS in my local branch have a refurb RX-V685 for £335 - seems a damn good deal and I guess does literally everything I need, if it was silver I think I'd bite.
At the back of my mind with that one I'm not sure it's 'high-end' enough to warrant replacing my old but to my ears very decent Marantz. I think if Covid hadn't affected supply then I'd be looking to get an SR6014, so with that said perhaps wait til an SR6015 is in the £8-900 region next year and strike then. I guess in case there's any issue with the HDMI 2.1 boards waiting wouldn't hurt either.

Yep I saw the RX-A2080 on RS - in Silver too! Got the tape measure out, however no chance! My unit is only 390mm deep and even if say subtract 60mm off the A2080 depth allowing for the volume knob and terminal depths, it's still going to be deeper than the unit itself :(

Damn! If it would been typical year this would have cost 800-850£ by now. There was some air in the Denon prices when they were on sale, so i assume the same thing with this but likely still too expensive for you. Just a tad deeper than 6015.
 
Damn! If it would been typical year this would have cost 800-850£ by now. There was some air in the Denon prices when they were on sale, so i assume the same thing with this but likely still too expensive for you. Just a tad deeper than 6015.

Yeah don’t want to spend that much really. I’m only driving a centre and rears from the AVR so I reckon it’d probably be mostly wasted on me. Assuming most of the difference is going to be the extra channels and power over a SR601x series (they look on the face of it to share a lot of features and have the same XT32 version).

To be honest I’d be happy enough with an SR501x series, enough power, decent size with all the features I want, and although XT isn’t as good with subs - I’ve got the miniDSP which will stay inline in front of them for when I use them in Hifi duties.
I’ve not once seen an SR5014 though that was a decent price, they actually seemed very hard to find in the UK too - maybe the SR5015 will be easier to source.

I did speak to PT about theIr part-ex Denon 4300H they had for most of this week, told me lowest price they’d take for it was £579 and they wouldn‘t entertain extending the warranty any longer either. Which I thought was a high and risky price for a 3-4 year old AVR with 30 days warranty!
 
@Conrad.
Thanks for the offer on the other thread, let me know what you need in the mdat thanks.

I assume:
Sub 1
Sub 2
Sub 1+2
Left
Right
Left+Right
Left+Right+both subs
?

I have after a long time arrived at configs I’m happy with for music, but weirdly the 2nd one needed the subs phase inverting, whereas the first one didn’t?

I’ve not got any broadband at the mo (Thanks BT FTTP for crapping out in 72 hours!) so have to make do with photos on my phone!

First config, I wanted this one to be purely a bottom end extension config. Which I think I’ve done and the final result suggests no ill effects higher up.
3B14EB10-6E25-4E0F-90B9-524991218C53.jpeg

In listening it does as expected, mostly imperceptible but when called for.

For the second config I want a slightly artificial bass boost. Took ages of messing with EQ and crossover settings on the MiniDSP, eventually flipped the phase and to be honest it’s not a millions miles now from where I’d like it.
A170E2DD-E363-4EC0-B2E1-D46292E481EE.jpeg



I haven’t done a config for the AVR yet for movie use. That should be easier given the mains will roll off and should avoid any phase problems!
 
For an MDAT, the measurements that are useful are:

Each sub on the LFE channel
Each sub on a mains channel, with no main (so the crossover is engaged but it shows the effect of the crossover)
Each of the LCR individually with the crossover engaged but no sub

All with a consistent timing reference.

The steps are usually:
- time align the subs to get the smoothest response on the LFE channel
- apply that alignment to the subs on the crossed over channel and create an aligned sum
- align that with each main separately, looking for a common distance that results in a good response across all three.

Where's your crossover set? It looks like you're getting meaningful output from the mains at ~35Hz.
 

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