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KEF LS50 Wireless integration with REL sub

I bought the KEF LS50 wireless back in December and was blown away by the amazing performance of these speakers at their respective price point. Although, I was more than satisfied with the lower frequencies without a sub (the base output and quality was on par with my full range B&W CM10s, believe it or not), when a local seller put out an ad for a barely used REL T9i at a very attractive price, and in matching white, I just could not resist. Integrating the sub with the speakers took about an hour or so. Given the position of the speakers and the general layout, WAF etc, I had very little flexibility in placing the sub. Anyways, to make a long story short, the results were impressive. The sub has blended and disappeared very well. The biggest benefit is that I can listen at a lower volume and still get a very satisfying experience. However, I feel that the imaging has suffered a tad. Without the sub, the imaging was laser-focused. It does become less precise when I turn the sub on.

Now I'm just wondering if it is possible to improve the integration even further. The KEF application provides several settings to tune the sub per your taste. This includes: High-pass mode (I'm not sure what it is supposed to do so right now I have turned it off), Sub-out low-pass frequency (I feel the best setting is 75 hz), Sub gain (I have it at -4.0 dB).

The REL T9i also provides cross over and volume control knobs on the back. The problem is that given that both the KEF app and REL provides a way to tune the sound, what is the appropriate mix of settings? 

If anyone has tried the KEF LS50 wireless (not the passive version) with a REL sub, I would really appreciate it if you can part with some of that wisdom. 
128x128arafiq

Showing 2 responses by willemj

willemj
1,036 posts
 
Congratulations. The purpose of a high pass filter is to cut the low frequencies being reproduced by the main speakers. Since the low frequencies pose the biggest demand on both speakers and power amplifier, you make life rather easier for them if you divert that task to a dedicated low frequency unit. However, it also makes integration more difficult because you have to deal with two filters rather than just one. So unless you want the maximum output from the speaker combination, there is a lot to be said for allowing the main speakers to play full range, and only use the subwoofer to fill in below them.
Without having tried your combination I would have thought that 75 Hz is far too high for the low pass filter of the subwoofer in this combination (assuming the main speakers are playing full range). My hunch is that some 40 Hz is a much better ballpark.
My second piece of advice is to only use a subwoofer with an Antimode 8033 or similar system of room equalization. Room modes play havoc with the in-room sound with huge peaks and dips. And their upper harmonics also mess up response at higher frequencies, particularly in smaller rooms. Room eq significantly reduces such room modes. And if you really want to get the best low frequency sound, use a second sub (in mono, and still with room eq). See here: http://www.acousticfrontiers.com/20101029using-multiple-subwoofers-to-improve-bass-the-welti-devanti...
willemj
1,036 posts
 
Maybe you should have increased the level of the subwoofer when you lowered the low pass frequency (that is what REL usally recommends, and I tend to agree). But it is just a thought.  If you really want to know/see, get a calibrated measurement microphone like the UMIK-1 and do a measurement in REW (but not for the fainthearted in computerland). Your original 75 Hz was certainly too high without high passing (i.e. cutting the low frequencies) of the main speakers.
As for the Antimode. If you do not have a preamplifier output, you can connect the sub at speaker level and then use an attenuation cable (that is what I do). Look carefully at the connection examples at the DSpeaker website. The cheaper Antimode 8033 Cinema model is probably all you need.
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