Is it possible to cover the whole spectrum, high SPL, low distortion with a 2-way?

[gedlee]

The spectral decay in a small room at LFs will be dominated by the modal decays. You would not be able to even find the decay of the driver until its Q approached that of a room mode, say 10.

Above the modal region the Q does matter as it is no longer dominated by room modes.

Just in case you don't know this, I go to extremes to dampen my rooms at LFs and I mean extremes. But I don't worry about the source Q at all.

 

[camplo]

The only thing I can think of, is that at nearfield, this intimate listening position might be affected a little more by spectral decay....the way you are describing this situation makes me think of the experience of sound engineers who have dampened their room greatly....I remember people saying something to the effect that after you get the room under control....it starts to reveal the flaws of the speakers.

 

[krivium]

Could you elaborate on what extreme mean to you Earl? Bass traps, dual leaf construction, same techniques as in studio builts, suspended ceilling and decoupling? I'm very interested about this ( your own application, i known about your front wall but not the other parts of your room).

 

[plasnu]

I would say that my speakers can handle this song definitely better than my room with walls and doors making a lot of noise.

Regards

Charles

The best way to check the resonance is disconnect tweeter (and midrange) and listen to the song. We will hear what we do not want to.

 

[gedlee]

Could you elaborate on what extreme mean to you Earl? Bass traps, dual leaf construction, same techniques as in studio builts? I'm very interested about this ( your own application).

The room is a corner in a concrete basement. The floor is floating with damping, and the ceiling is suspended and rigid with damping. The rigid wall behind the speakers has about 3 feet of foam along it. The other concrete wall has faux stone to act as a dispersive reflector. The two installed walls are filled double construction with resilient hangers for two sheets of drywall with constrained layer damping. LF damping requires damped walls as nothing smaller is going to yield enough effect. The whole room is also sound proof.

 

[krivium]

Yeah this is what i thougth ( i edited my previous post while you answered). What i have built for professional studios.
Must be very damped and have a nice low end once multisub implemented. Drywall can make nice basstraps.
You are decoupled at which freq from the floor?
Thank you for answering.

 

[camplo]

I am reminded that enclosure stuffing improves other specs...lol...OK my like isn't exactly turned upside down...I've done good, all is well.

 

[gedlee]

I'd still put as much damping in a closed box as practicable because it makes the box appear larger. Too much and the effects reverse. Just lots of loose material. Foam works great.

Just give up on anything but closed box and you'll be fine. Any decent driver (adequate power handling and excursion, and plenty of amp power, Pro woofers work great here,) at least three and spaced apart. Same recommendations that I have always given and haven't changed. Especially since everyone who has tried this has been pleased. Why change?

EQing can be tedious and tricky, I must admit, but diligence will win out.

 

[camplo]

Thanks for taking the time, once again!

Good convo guys....

 

[camplo]

I've been second guess this PPSL thing

LIke I said...even though I argue...I try to take what you guys tell me seriously... So allow me to go through the motions for the sake of my sanity....

Is this PPSL even worth it for me? The 18H+ has all that useable upper range that gets high passed due to slot resonance/cancellation...

I was thinking I could configure like the pic up top.... with the 15m on top and the 2 18h+ on the bottom..... MTMW...yes I know its not traditional but I think it would work fine I actually like the idea of the 15m and 18h+ working in tandem...I end up with a little lower group delay around 100hz in sim..... The efficiency through most of the bass increased greatly as the bottom woofer can help out much higher being out of the slot.....

The bottom woofer, low passed at 35 with a lr12, at xmax, in half space, 30hz is at 112db with 2db (114db potential total) of help from the other woofers (no other filters but highpasses on the top 2 woofers).....vs the 117db at Xmax in PPSL....

On the other side of the fence....I can create some nice wide polars on the vertical with the 3 way config....excursion is much less in the lower bass....

The more I look at the two sims the less differences I see. The two major differences are the major efficiency in the subbass vs the major efficiency in the rest of the bass....whether helped by another woofer in mtm or highpassed in a 3 way, the 15m never sees much excursion in either setups....

I don't know what to think about that....How much efficiency do I need in the midrange?....the 15m never sees more than 2mm in the 3 way setup....would I even notice the increased 6db of efficiency with the mtm? Seems like a waste...but I also understand that midrange is everything...so maybe you guys know something that I don't regarding this>?

For some reason the 3 way setup retains directivity down lower to somehow...I took that as a plus for the 3 way.

Someone say the wise words please.

 

[norman bates]

Ppsl for what exactly ?

If / when i build my next sub, it will be ppsl.

I've made 3 so far.
Search djk and ppsl.

Here is a push pull 12" review, ex m&k maker, from 2012
KEN KREISEL DXD-12012 Dual 12" Push-Pull Subwoofer - HomeTheaterHifi.com

 

[camplo]

The build has stereo PushPushSlotLoaded 18h+'s sitting under a 15m as it stands now.

 

[norman bates]

Many words to sift through.......

Can you simplify your question ?

 

[camplo]

Basically

Trying to weigh

My drivers in a 3 vs mtmw

1 - 15m
2 - 18h+

The three way has more surface area dedicated to sub bass (18H+ ppsl slot loaded, 15mid)
The mtmw was more surface dedicated to midbass (15mid on top of horn, 2 18H below... bottom woofer low passed, top two woofers lowpassed to horn)

 

[norman bates]

I'd go for more midbass.

I've been contemplating adding more woofers to what i have, i miss the midbass slam i had in my big 2-way (double 15's crossing at 750hz).

Mids and tweet horn much better now, just missing pounding bass, not rumble.
Crossing over 80-200hz seems to mess with the slam.
Slam has to do with integration.

That's why I've been carrying the big 2-way banner for years.

 

[GM]

I don't know what to think about that....How much efficiency do I need in the midrange?....

Well, if you have some recordings that closely replicate a live event, especially large orchestras, drum kits, etc., then the ~125-500 Hz BW will have the highest power requirements, though obviously there's [modern] music that extends it down lower [don't know about higher]: http://www.wghwoodworking.com/audio/multsubs.pdf

As always, 'there's no replacement for displacement' when it's time to go live.

 

[camplo]

I agree but the 15m never reaches past 2mm in the 3 way set up...does that mean anything?

As always, 'there's no replacement for displacement' when it's time to go live

Thats the tricky part for me right now...where to I want to put the displacement as both configurations have the same drivers.....Bass takes more displacement period....the mid only hits 2mm at max volume...so think about how low the excursion is elsewise.... Does that even make sense what I am saying?

 

[camplo]

I'd go for more midbass.

I've been contemplating adding more woofers to what i have, i miss the midbass slam i had in my big 2-way (double 15's crossing at 750hz).

Mids and tweet horn much better now, just missing pounding bass, not rumble.
Crossing over 80-200hz seems to mess with the slam.
Slam has to do with integration.

That's why I've been carrying the big 2-way banner for years.

Interesting..,...the PPSL is down 20db at 200hz.....how do you analyze this, as far as its ability to "slam" - Its coupling with the 15m at this points

At 150hz its down 10db from the 15m... What do you think?

Crossing over 80-200hz seems to mess with the slam.

- lol guess that answers that.

ONe thing I think about is that in the MTMW configuration...the woofer under tweeter (18H+), I could take that and eq some bass help for the W portion. How that would sound not sure...

Norman you said you missed your TMM....what are you listening to now that would make you feel this way?

As always, 'there's no replacement for displacement' when it's time to go live

Looking at this....for home levels....do we not reach a level where "more displacement" is null?

 

[norman bates]

Jbl 12" 2-way using 2206 and 2431 with older pt 100 x 100 waveguide, 3" deep and 12" x 12", minimal reflections in my opinion. Even cross at 1.2khz, where a 12 should. Foam around mouth, added some acustuf also.

The pic in my avatar.

I never though to much woof was possible........

 

[fluid]

Being as relating perception to math has been my life's work, I'll comment, although many won't like what I have to say.

For a sub, in practice, there is going to be little to no relationship between perception and metrics (T/S etc.)

First there is the fact that our ears are not very sensitive at LFs, i.e. there "resolution" is very low.

Next there is the fact that in practice the room will totally dominate all perceptions at LFs and the T/S values will have little to no relationship to preference - at least in the linear domain. This means that linear volume displacement is just about the only real value that matters. This can be achieved by one driver or many, it makes no difference linearity wise. With many however we can distribute them and yield a much smoother in room response - which is highly audible - than a single sub placement can yield.

Hence, to me, all this talk of T/S etc. when related to a sub just doesn't matter because it is the end result in the room that matters and this can be achieved with virtually any T/S parameters. The end result will be more dependent on the number and location of the subs than any T/S parameter, driver size, cone mass, box, size, alignment or whatever.

camplo, this from Earl was the most useful piece of information in the last 50 pages and got zero response, get your head around this as it will benefit you much more than the latest endless debate.