CHEAP SUB -£500 2.1 SETUP? LOW HZ QUESTION.

malcolm mccaw

malcolm mccaw

malcolm mccaw

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18 Oct 2014
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Hello all, i noticed a sub phono conection on the back of my little denon m39 and was thinking of adding a sub to go with the two moniter audio bx2's that ive got hooked up (via optical) to my 47" 3d sony tv & blu ray set up. BUT am i right in thinking that unless i can go lower on a subwoofer than the bx2's 42-30,000 hz freq, then im not going to gain much from doing this? Room size is 3.5 by 4.5m. Looking around the net i found the bk 10" gemini 2, is the ideal sml size cabinet for where it would go, but the low hz level 40, is similar to the speakers? Does this matter? Please help. thanks m
 
I got the impression that adding a sub would allow your other speakers to kinda focus on the mids and above which would improve the overall quality of the sound. Ive got a Gemini 2 and it seems to pack plenty of punch right now for the size of it. Also seems very well finished. Only thing I find it lacks is a auto on/off.
 
Manufacturer claims sometimes need to be taken with a pinch of salt. I haven't seen a response curve for the BX2 speakers, but here's one for PSB Image B6 which are a similar sized bookshelf speaker. The manufacturer claims 45Hz at -3dB. There's every chance the speakers might do that with a bit of boundary reinforcement, but they wouldn't measure the same in an anechoic chamber. Same speakers - different environments - different results.

speakerresponseplot.png


BK Gemini II is a very popular sub. The performance for the money is extremely good. However, BK don't publish a frequency response curve, so it's difficult to say exactly how low the sub will go. One thing is for sure though, it will get down to 20Hz and probably a bit lower. The lower bit is academic with the D-M39 though because it's working on the Hi-Fi frequency response range. That starts at 20Hz and goes up. The Denon doesn't output anything lower than 20Hz.

Back to the BK; the 40-120Hz figure you've seen isn't the frequency response; it's the roll off point. That's where you decide to set the upper limit of the frequency response to tail off when blending with the other speakers.

Combining the above points then, the Denon outputs 20Hz to 20,000Hz. The BK will operate from 20Hz up to some blend point that matches where the BX2s naturally roll off. This will give you frequency coverage from 20Hz to 20kHz
 
I have the Gemini II and it's powerful enough to shake the room even at moderate volumes. When the tripod emerges from the ground in War of the Worlds for example, it feels like an earthquake. :cool:
 
.:SAmSuNG:. said:
Whats the best way to figure out where to set your speakers and sub blend point? Also should there be 10hz overlap?
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That's a "How long is a piece of string" question. The answer depends on the gear you're running and whether you can be absolutely sure of the main speaker frequency response in your listening room.

If you followed the gist of the post with the graph in it, then you'll appreciate that some published specs should be treated with caution. So trying to be too prescriptive about crossover frequencies will probably backfire. The best you can do is use them as a rough guide.

I'll presume you're talking about Hi-Fi since most AV receivers now include a set-up mic and wizard for the process. Start with phase first on 0 degrees and the crossover at maximum. The sub's volume needs to be roughly in line with the front speakers. Play some music with a decent bass beat. Alter the phase until the strongest bass kick is heard.

Next, listen to the system playing music with the sub crossover set very low, then repeat with the crossover set high. You're listening for the hole when set low, and bass that's too pronounced when the crossover is set too high. Just experiment and adjust by ear.
 
Those bookshelf speakers won't get anywhere near 45hz, at least not cleanly and not with any meaningful output. Have a listen and see what sounds better, but I would try starting at 100hz crossover.

Oh and if you can stretch to it, the XLS200 is a much more capable sub. The Gemini isn't really capable of pressurising a room of the size that you have (an XLS200 barely is, but it will be a noticeable step up).;
 
kinetic747 said:
I have the Gemini II and it's powerful enough to shake the room even at moderate volumes. When the tripod emerges from the ground in War of the Worlds for example, it feels like an earthquake. :cool:
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If this is right then its sounds ok to me, as i live in a flat with people below and on either side, so i dont want to go to loud loud if u k.w.i.mean. However i maybe able to fit the xls200 (as suggested above) sideways in the same space (up against the wall), but is it THAT much better than the gemini?? also are these subs easy to set up with my denon m39 & bx2's? lucid? anyone? MANY thanks m
 
There's no technical reason to stop the sub and the main speakers integrating. I am working off a phone at the mo so can't easily check on the d-m39 outputs for a dedicated sub socket. But eben if it has one it's reckoned that the high level socket (speaker connections) sound better for music.
 
lucid said:
There's no technical reason to stop the sub and the main speakers integrating. I am working off a phone at the mo so can't easily check on the d-m39 outputs for a dedicated sub socket. But eben if it has one it's reckoned that the high level socket (speaker connections) sound better for music.
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yes the m-39 does have a single sub socket
 
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