Recent PMC & Sub Purchase

[admin_exported]

Hi all,

I posted a couple of times in the recent past, saying I was thinking of adding a sub to my PMC FB1+ speakers. I thought I would drop of a note in the forum as an update and to say thanks to all who previously advised.

The thing arrived on a pallet and it is a beast, a BK Monolith weighing 51kg. I downloaded and burnt a CD of test tones, with a 10 sec burst of every frequency from 11hz to 100hz. When I loaded I was staggered that my PMCs went down to 30hz according to my hearing. I know they specced to 28hz, but I was slightly skeptical until the test. The sub only needed to fill in below 30hz, so I set the crossover to min (40hz) and tested with differing subwoofer volumes.

I attached the sub power to a remote controlled socket, so I can switch on and off from sofa. There was a massive bulge at 40hz, which I think is down to the acoustics of the room. To flatten this bulge I had to turn the woofer down, and now I get very very gentle assistance below 30hz, and small bulge at 40 hz, and the PMCs drive affairs after 50hz.

I am thinking of getting a Behringer ECM8000 omni-directional mic and mic preamp to plug in my PC, and then take measurements of the sound and room response. The only barrier is if I can bring myself to spend £80 on the mic and preamp, I have a gadget wish list.

By switching the sub off and on with the power socket remote, I find the sub is ever needed. This was pointed out to me on this forum before I acquired it, as not many acoustic instruments go below 40hz. I am not sure if I should raise the subwoofer gain and live with the 40hz bulge.

I am astonished how low and powerful the PMCs go down without help. They are astonishing...

 

[Anonymous]

To follow up from post above I have measured my room using a semi pro soundcard, Soundmeter linked to PC and measurement software. I am a bit hesitant ot post as I think the Hi-fi forum concentrate on subjective qualitative testing, where the AV type forums are more into measurments.

As mentioned above, I have PMC speakers and just bought a BK Monolith. I am not sure if is a good upgrade yet, as the PMCs go mighty low. Also, not many instruments lie in the extension the sub give me.

The room really rings on 40hz and 130hz without the sub. The sub extends below 30hz and lifts the 90hz area. I thought about applying EQ to the sub, but discounted this. To apply a Behringer Feedback Destroyer to the sub wouldn't change anything, and I don't want to add anything in the path of the PMCs. I can't move the sub or speakers anywhere else, so it's a case of live with it.

I wonder when speakers are tested, if a real life test should be done as well as laboratory type listening rooms. The AV guys I read or swapped posts with think most rooms ring loudly at 40hz. I know all rooms are different, but a std test lounge would be cool.

I'm posting because some might be interested in the frequency responses of the PMCs. The first graph is what I settled for.

 

[Anonymous]

Nice work TNT!

Very much appreciated to see some proper measurements amongst all those subjective opinions (which I enjoy as well though

), off course audio listening is more than a bunch of measurements but especially with speakers I do believe there is a strong relation between the measurements and the actual performance (must be anyway!).

I am still shocked/ surprised sometimes about how there seems to be a strong almost believe that audio equipment performance can not be measured at all and there is a certain mystical aura about it, with a few generally accepted truths or rules. Even the audio bible (Robert Harley's The complete guide to high-end audio) is full of subjective rules of thumb.

Sorry for my jabbering...

Did you just measure the bass band or also the rest of the spectrum?

 

[Anonymous]

Thanks Mate,

I have to admit I was a bit nervous about posting a quantitative led analysis, rather than a qualitative.

I didn't do a full frequency plot because I was concentrating on the sub and also my measuring equipment isn't great after 4khz. It is pretty good up to 4khz.

I would like to see speaker plots in reviews, but more so for measures in a 15ft by 13ft test lounge. I know all rooms are different, but a mock living room with a three seater and two seater, a coffee table and some souvenirs tat bought when judgment was down.

The other motivation was to demonstrate that these PMCs are great deep down. I could have got away with not adding a sub. I don't regret, as I will build an AV system eventually.

I like my BK sub. They build cases and cables for other makers like Rel and PMC. I have the rosewood, to match my PMCs, and it looks great. When I have a party I might give it the bass!