P12-300SB vs PR results

jonjames

Active Member
I received my new P12-300 PR last week and set it up the other day. Ran Audyssey and then used REW to check results. I was hoping to get a bit closer to 20hz but I am getting what looks like the exact same response from the SB version. Tom said the PR version is tuned to 15hz, I know that's not what is likely to be achieved but to get no improvement seems a little odd?

I will continue to play familiar content to see if it sounds any different, and after a few hours will check with REW again, I may send the results to Tom too for his thoughts.

It is in the exact same spot as my SB was. Last year I borrowed an SVS pb-1000, in the same spot you can see from the pic that I was able to achieve a lower response, I didn't like the look/size of it so didn't buy one.

So yeah a bit miffed it is no different, another reason for buying it was for the mahogany finish so I will keep it although I'm a little disappointed there is no improvement, unless I am missing something?
p12 sb vs pr.jpg
PB1000.jpg
 
Last edited:

fatboy frank

Distinguished Member
You'll probably see better results once it's had a good few hours on it, they do generally improve after 50+ hours.
 

MI55ION

Distinguished Member
There appears to be a modal issue at 27hz causing a null at around the same region both the subs rely on room gain for that extra extension hence the steep roll off. Both the sealed and PR versions display a similar roll off rate kinda backs this up. The SVS seemed to overcome the effect by brute force/power at the lower end so it lifts it back up and drops off closer to 20hz.

Either that or some sort of high pass filter / room gain compensation is being applied somewhere in the signal chain.
 

Gasp3621

Distinguished Member
I received my new P12-300 PR last week and set it up the other day. Ran Audyssey and then used REW to check results. I was hoping to get a bit closer to 20hz but I am getting what looks like the exact same response from the SB version. Tom said the PR version is tuned to 15hz, I know that's not what is likely to be achieved but to get no improvement seems a little odd?

I will continue to play familiar content to see if it sounds any different, and after a few hours will check with REW again, I may send the results to Tom too for his thoughts.

It is in the exact same spot as my SB was. Last year I borrowed an SVS pb-1000, in the same spot you can see from the pic that I was able to achieve a lower response, I didn't like the look/size of it so didn't buy one.

So yeah a bit miffed it is no different, another reason for buying it was for the mahogany finish so I will keep it although I'm a little disappointed there is no improvement, unless I am missing something?

Can you take very close measurements for each, i mean mic close to driver. Perhaps we see some differences there, room affecting less. Here is one with P12-300SB, 20cm from driver and almost touching it.

5f80cb88-5913-40de-a960-39e7023a3286-jpeg.1155876


And in-room response from MLP:

cecb9a07-42d0-4815-b32a-c8e628dcdee3-jpeg.1156496
 

MI55ION

Distinguished Member
Can you take very close measurements for each, i mean mic close to driver. Perhaps we see some differences there, room affecting less. Here is one with P12-300SB, 20cm from driver and almost touching it.

5f80cb88-5913-40de-a960-39e7023a3286-jpeg.1155876


And in-room response from MLP:

cecb9a07-42d0-4815-b32a-c8e628dcdee3-jpeg.1156496


The vnf measurement shows a standard 12db/octave roll off that you typically get from a sealed design. This means under ideal conditions with room gain OP should get a flat(ish) response approaching 22hz. However I suspect that null at around 27hz is sucking out all the energy and since the sub/amp doesn’t have enough grunt below 30hz the response is tragically disappearing into the abyss.
 

jonjames

Active Member
I'll do a close up measurement if I get chance over the weekend to see what I get.

The sub does sound good and hopefully it may open up a bit after a few hours, my first BK sub definitely did.

That null at 27 ish hz I presume is down to placement? It is about half a meter from the corner of the room, I would have thought that should help with room gain. Maybe I should try it even closer.
 

MI55ION

Distinguished Member
With sub bass frequencies you'll get room gain pretty much anywhere. The downside to it is that whilst some frequencies get boosted others get cancelled in relation to your MLP. So you have three options to try which can help or hinder the bass response:

1) Change the location of the sub - experiment with different places even if impractical - to get an idea of whats possible
2) Change your MLP - easier said than done but as above a good way to gauge what's possible.
3) Add an additional sub (different location) of similar/same spec and design. The preferred method for most as it has multiple advantages.
 

jonjames

Active Member
I can certainly try moving it to the otherside of the TV. The sofa cannot move really. Once I get a new AVR, I do want to try and get another sub, just waiting for prices to come down.
 

Gasp3621

Distinguished Member
I'll do a close up measurement if I get chance over the weekend to see what I get.

The sub does sound good and hopefully it may open up a bit after a few hours, my first BK sub definitely did.

That null at 27 ish hz I presume is down to placement? It is about half a meter from the corner of the room, I would have thought that should help with room gain. Maybe I should try it even closer.

Great. Why not also try tucked tightly in corner and the other side if that is possible..
 

Gasp3621

Distinguished Member
The vnf measurement shows a standard 12db/octave roll off that you typically get from a sealed design. This means under ideal conditions with room gain OP should get a flat(ish) response approaching 22hz. However I suspect that null at around 27hz is sucking out all the energy and since the sub/amp doesn’t have enough grunt below 30hz the response is tragically disappearing into the abyss.

Yes, would be just intresting to see the "natural response" of the PR compared to P12 (sealed). I believe closer to 36db/octave roll perhaps.
 

Ultrasonic

Well-known Member
If nearfield measurements are tried, make one with the microphone close to the main driver and another with it very close to the passive radiator. The lowest frequency output will be dominated by the PR, just like a port on a ported sub.
 

jonjames

Active Member
I have done 3 measurements, one at MLP, one just in front of the speaker, and one underneath the passive radiator, I measured from 15hz to 200hz, this time with the x/o on my amp set to 250hz.

I've put a few hours of demo worthy films through it, including A Quiet Place, that film has incredible LFE!

So from these measurements what does this tell us? To me it looks like the sub is capable going from the close ups?
P12 PR 3 measurements.jpg
 

jonjames

Active Member
@Gasp3621 @MI55ION @Ultrasonic

Not sure if I needed to tag you to see my update. I've not managed to move it to the corner but done the close ups for now on the post above. Any thoughts please?
 

Ultrasonic

Well-known Member
I'll be honest I'm confused by the peak just below 90 Hz close to the PR that is higher than the low frequency peak. Below is an equivalent set of measurements I made for a BK Monolith, with the port contribution in blue and the main driver in red. Maybe I got a cleaner result as I was able to place the microphone right at the exit of the port whereas you maybe had ore of a distance from microphone to PR?

Remind be what you're trying to find out/achieve here?


Monolith port and main driver contribtuions.jpg
 

jonjames

Active Member
The main reason I started the thread was due to getting the almost exact frequency response from a sealed sub and a PR sub.

I was asked to do some close up measurements, I guess to see that the sub can output frequencies below 30hz which it looks like it does? It just seems they don't make it to the MLP due to position and or power of the sub? I really was hoping to get closer to 20hz.
 

Ultrasonic

Well-known Member
The main reason I started the thread was due to getting the almost exact frequency response from a sealed sub and a PR sub.

I was asked to do some close up measurements, I guess to see that the sub can output frequencies below 30hz which it looks like it does? It just seems they don't make it to the MLP due to position and or power of the sub? I really was hoping to get closer to 20hz.

Yes, the measurement near the PR confirms the ~15 Hz resonance that Tom from BK said it was tuned to.

You'd need a huge room for there to be an interference minima complicating the picture around 20 Hz, although room size will also affect the level via 'room gain'. How big is your room?

I expect you'll see the same result but I vaguely wonder if there is any point you making measurements at a higher volume just in case it affects the relative contribution of the PR. With the microphone at your MLP could you make a measurement at your previous volume and then at one to two higher volumes and share the graph?
 

Ultrasonic

Well-known Member
Oh, and there isn't any possible of a high-pass filter applied anywhere in your system that would limit output at very low frequencies is there?
 

jonjames

Active Member
I don't believe there are any filters no, LPF for LFE is at 120hz, and on the back of the sub it is set to LFE. Not sure there are any others?

I'll get some measurements at different volumes and see what the results look like.

My room is 5.8m x 3.8m. Below is a plan of room layout and I have added in speakers, tv and sofa.
Floorplan.jpg
 

Gasp3621

Distinguished Member
It just seems they don't make it to the MLP due to position and or power of the sub? I really was hoping to get closer to 20hz.

If you can do the measurements in those couple other spots you mentioned were possible, tucked in front corner etc. Not sure would nearfield placement be ok by the couch and how that would look like then. Bit disappointing atm.
 

MI55ION

Distinguished Member
I'll be honest I'm confused by the peak just below 90 Hz close to the PR that is higher than the low frequency peak.

Just wondering if the measurements were taken with L/R speakers engaged or sub only, perhaps OP could clarify? Otherwise the NF measurements seem consistent with what one might expect from the sub.

@jonjames, the doors open/closed can also have an impact on your measured results at MLP.

I have a suspicion it's a combination of the sub being too small for the room/not enough power and MLP in a wide 20-30hz null region.

I've taken some liberties here but room sim seem to support this:

room sim snapshot.jpg



Try the sub in following two positions and put up some measurements if you can. On the right side of the TV unit:


room sim snapshot 2.jpg



And bottom right corner:


room sim snapshot 3.jpg
 

Ultrasonic

Well-known Member
Just wondering if the measurements were taken with L/R speakers engaged or sub only, perhaps OP could clarify? Otherwise the NF measurements seem consistent with what one might expect from the sub.
My point was that close to the PR you'd expect its own signal to dominate and you certainly wouldn't want it to be providing most output at 90 Hz.
 

jonjames

Active Member
My second lot of measurements in post #12 were with x/o on mains at 250hz . Post #1 was mains with an 80hz x/o as forgot to change it.

I always run Audyssey and do my measurements with all doors shut.

Don't get me wrong the bass it produces is seriously good, sofa shakingly good in fact. These subs never fail to amaze me. When watching a Quiet Place the other day, the LFE was unreal. I can't imagine what something more capable would be like.

When I get chance I'll try different locations as per the sim. Appreciate everyone's help so far.
 

Ultrasonic

Well-known Member
If you do any more measurements please make sure that its only the sub generating any sound. Not other speakers as well.
 

jonjames

Active Member
I got chance to do one measurement with the sub on the left hand side of the TV with Audyssey turned off, this is even worse, I doubt Audyssey could do much with this, especially my version (XT). Am I just sitting in a massive null?

p12 pr left of tv.jpg
 

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