Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems Running 2 D1500's

In the event that I get hold of another D1500 am I correct in thinking that my best option is running them off the DSP33's and getting the 568 to treat the set up as 5.0 for movies? There was a similar thread about a 7.1 system last year but it didn't seem to be resolved.
Unless there is a very good sonic reason for not doing it I plan on the subs being directly below the DSP33's, which would be around 8' apart.

No, chain them on the subwoofer out and put every speaker as small and start with a 80Hz Xover.

As for placement try both in corners or near the front two speakers as you proposed.

Nick, I've been thinking about this a lot recently.

Although crion has a lot more experience with multiple subwoofers than I do, I'm going to disagree with him about chaining the subs together on the grounds that Meridian feels that a stereo bass image is important, even for subs. The 568.2MM can handle a "discrete" 5.2 setup (as opposed to a 5.1 with a double sub).

As you say, you have two options:

You can use each D1500 to turn your main L/R DSP33s into "full-range" speakers in a 5.0 setup, but there is a problem here which isn't obvious. The D1500 crossover switch in the "FILTER2" position selects a 56Hz low-pass filter "optimized for use with DSP33s". The issue I have with this is that there is no corresponding "56Hz" high-pass filter on the DSP33s:

a) I'm sure that Meridian chose 56Hz on the D1500 to match the bass response of the DSP33s as accurately as possible. However, I doubt that the 2nd order Butterworth filter in the D1500 is a exact match for the bass drop-off in the DSP33s. Assuming you correctly set the sub volume to integrate with its corresponding DSP33, it's not the most controlled crossover.

b) Worse, remember that DSP33 bass extension is extended at low and moderate volumes? At which volume does the 56Hz D1500 crossover work best with the DSP33s? Without a corresponding high-pass crossover in the DSP33s, the implications of melding a static crossover in the sub with volume-varying bass response in the DSP33s can only be volume-dependent bumps in the bass response around 40-60Hz. I discussed this with Des Ford several years ago and asked him if Meridian had a graph showing how the DSP33 bass extension changed with volume. However, such a graph ever existed, it got lost in the mists of time and would only have been of use for satisfying my curiosity.

Having discounting option one, I think you should use the stereo subwoofer outputs and crossover in your 568.2. This will yield a far more accurate, precise and coherent crossover between the DSP33s and subs. For what it's worth, I have a single REL sub to which I crossover bass from my 5x DSP33s at 56Hz with my G68. It sounds good at the moment, though 56Hz may be a bit too low. To do better, I need to investigate what is going on in the crossover region with an RTA analysis tool. This is something that I plan to do later this year.

So rather than connecting them all on the same SPDIF line and using the built in matched crossovers on the D1500, you suggest connecting them to the 568.2MM so that you can use the bass management in the 568, correct? Can the 568 be set to provide exactly the same crossover as the built in D33 crossover on the D1500?

Correct.

Yep. There is a single crossover in the 568 per bass management layout. Remember that in using the 568, you are using a single crossover (unlike trying to meld together two speakers using multiple crossovers) and the 568 will ensure that that the bass is split correctly at the crossover to the DSP33s and sub(s), with no missing bass or bass bumps and with the correct phase. As long as you have set up the correct relative volumes of DSP33s and sub(s) of course. The 568 almost certainly has a higher quality digital crossover and may have a higher order crossover too.

So actually this solution is technically superior to the D1500 filter switch?

VK, the important thing is to use the 568.2mm Xover function. stereo vs. mono bass is a more academic question. But the Xover of the preamp is where he will have most control of the result as well as easing the load on the DSP33's which will help their midrange.

The reasoning behind mono bass radiated from several sources is that you will not have nulls and will even the peaks. You will not "miss" a single bass frequency from your material. You will get a sound <80Hz from all mono subwoofers and from the midrange/top speaker that is playing the channel with the specific <80Hz sound. Meridian uses 2nd order Xover if I'm not mistaken which corresponds to 24dB/octave. That means 40Hz is played 24dB lower from the DSP33 speaker if Xover is 80Hz (1 octave difference is always half or double the frequency in Hz).

With stereobass you have the notion that you will pick up <80Hz directionality and therefore you want the channels separate for music. If there is a specific <80Hz sound from one channel you will only get that sound from one subwoofer and from the midrange/top speaker that it is Xover to. This gives the possibility of missing a sound because of one null point (placement) with only a single subwoofer reproducing the sound. Ofcourse we could stack/chain the stereo channels as well with 2 + 2 subwoofers to reduce this possibility even more.

Now, with the same number of subwoofers 2*n I think this practically will not be much of a difference because the bass frequencies are often coming from both channels in a 2 channels music mix. And for movies you only get mono sound from the LFE anyway (which stands for most bass cues).

The important thing here is to use the Xover in the pre/pro to reach the best integration, control and added headroom from DSP33 speakers (needs to produce less bass thus easing the load on cone giving clearer midrange).

Yes.

Agreed, but surely this is no different to a single pair of 8ks in a pure stereo environment?

Edit: Now here's a thought. I wonder if hitting a bass null from one channel in a stereo pair is actually important psycho-acoustically? i.e. The brain uses the missing information in its mapping out of the room?

Thanks for the information. Now all I need is a second D1500..................

Did you just bag the one on eBay?

No, but patience is a virtue.

Yep. That one went for a a bit too much for my liking given the cosmetic condition. I guess the buyer just really wanted it.