Adding subs to a nearfield desktop system

[Jiraya369]

The Neumann KH750DSP 10-inch subwoofer has very good measured performance. Little wonder that the sound is fine. Compared to a pair of REL Tzero MKIII 6.5-inch subwoofers, the OP would see a very big upgrade in performance if switching to using even a single KH750DSP subwoofer.

The 10-inch driver in the KH750DSP has 2.4x the radiating area of the 6.5-inch driver in the TZero MKIII, and it could also be expected to have a large XMAX. In its specifications, the KH750DSP has an F3 = 18 Hz, versus an anticipated F3 = 48 Hz of the Tzero MKIII (indirectly specified by F6 = 37 Hz); that's well over an octave more bass extension! In addition, the KH750DSP shows a textbook step response performance, and it clearly outperforms many other subwoofers on this particular metric. This implies that the overall transient response of the KH750DSP is of a very high standard and is not unduly affected by any internal signal processing choices.

The frequency response and step response plots shown below were taken from https://www.audiosciencereview.com/forum/index.php?threads/i-measured-10-subwoofers.49042/. Here the measured roll-off rate on the KH750DSP is about 17 dB/octave, which is approximately one order higher than the natural 2nd-order roll-off in a sealed enclosure.

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yeah lol one sub is better than 2, sure.

 

[witwald]

Looking for input on sub selection and integration for a nearfield desktop setup.

That's a nice little nearfield desktop setup. Have you tried separating the Q1 Meta loudspeakers a little more? I'm wondering if that could result in a preferred sound quality? If you have tried increased separation, I'd be interested to hear your thoughts on the results.

I currently have a pair of REL Tzero MkIIIs ... I listen to a broad range of music, from classical, opera, and jazz to rock, prog rock, and electronic, including edm.

The REL Tzero MkIII subwoofer doesn't seem to have a lot of bass extension, which isn't surprising considering its compact size and small 6.5-inch woofer.

Room (photos below): third-floor home office, roughly 11ft (3.3m) x 32ft (9.7m), carpeted with wood-paneled walls angled to 8.5ft (2.5m) ceiling. Subs currently sit in unused floor space flanking the desk, though I understand symmetric placement isn't necessarily optimal for modal smoothing and I'm open to measuring alternatives.

The present location of the subwoofers and the listening position is very close to the front wall. As the listening position is so close to all the loudspeakers, I'm not entirely surely whether changing subwoofer locations is going to affect modal smoothing all that much. When sitting so close to the front boundary, the pressure might be quite uniform in that region. A room mode simulation might help to visualise what's going on, but if relying on free room acoustics tools then it will likely be a bit approximate owing to the sloped ceiling in the vicinity of the listening position.

As a simple experiment, you could place your two REL Tzero MkIII subwoofers together, centrally located under the desk. That may help inform you as to whether or not there are going to be any significant "modal smoothing" benefits of at your particular listening position using two subwoofers versus one single centrally placed one.

What I'm considering:
- Pair of Rythmik L12 (sealed, servo) — which seems like the better buy for modal smoothing than one bigger sub

Having seen the results step response measurements of a variety of subwoofers, one would ideally need to have some idea of how a subwoofer measures when responding to a step input signal. There are many subwoofers out there that don't seem to do particularly well on this particular test.

Frequency response-wise, the Rythmik L12 (sealed, servo) 12-inch subwoofer seems to offer a nice improvement over the much more limited bass extension offered by the smaller REL Tzero MkIII subwoofer.

 

[Sokel]

If you want more targeted advice keep your plots at 50dB range with some 1/12 or 1/24 smoothing (as anyone else here, instead of the 400(!) dB you show now) and even better, include the .mdat (zipped) of the measurement.

 

[YouDontHaveEnoughBass]

As said by others here you can get better for the money and probably get away with just one, evidence of stereo bass being perceivably better is hard to find

[taps username] your in-room response is looking very flat, are you listening at very high volumes? If not you'd want more of an upwards shelf at around 100hz, something vaguely resembling this though the size of the shelf will vary by preference and how loud you listen (louder = less bass shelf)

 

[vsch]

When it comes to subwoofers, I’d focus primarily on extension and SPL capability rather than small differences in anechoic response. In practice, the room dominates the in-room response in low frequencies anyway, so DSP and integration (delay, phase, crossover) matter far more. With a miniDSP and REW, you’re already set up to do this properly.

FWIW, I’ve used several subs (Arendal 1961 1S, SVS SB-1000, KEF HTB2), and once they were level-matched, time-aligned, and EQ’d, I couldn't tell them apart—as long as they were operating comfortably within their limits. What made a big subjective difference in my living room, though, going from a single sub setup to dual subs placed diagonally in the room.

So I’d prioritize, bang for the buck in terms of low end extension and spl capability. And going for dual subs is at least not a mistake if you feel comfortable with the slightly more challenging integration (ideally done with something like MSO).

As @YouDontHaveEnoughBass suggests, trying a slight bass shelf—something like +4–6 dB below ~100-150 Hz can sound more natural and fun.

 

[robh36062]

I had a pair of JBL 308 Mk 2 in my office and used a conventional 10" JBL sub and it worked fine. I used an inexpensive analog active 24db L/R crossover set at about 80Hz to balance and set levels.

Rob

 

[davybyrne]

Did you buy the SVS 3000 and are you happy with it?

It’s been about 12 hours since my original post, so I haven’t quite had the chance to acquire another sub

I almost have the same nearfield setup as you but i use only one 12" subwoofer (SVS SB-1000 Pro), if you do not use a high-pass filter higher then 80hz then i see no point of 2 subwoofers in smaller rooms.

Agreed. If I can find a position where the crossover can be at 80Hz or below without a big dip, I'll be happy to have just one.

 

[davybyrne]

I had a pair of JBL 308 Mk 2 in my office and used a conventional 10" JBL sub and it worked fine. I used an inexpensive analog active 24db L/R crossover set at about 80Hz to balance and set levels.

Rob

Could you share the specifics of the crossover you have (brand and where to get it)?

The JBLs—whether the 308s like you have or the 305s—are very good speakers and served me well for several years. I've been enjoying tinkering with a new setup. Subjectively, I'm enjoying the Q1 Metas more. The 305s had a noticeable hiss that drove me nuts. The Q1 Metas with the 3e audio A7 are dead silent, and in their walnut veneer cabinets, much prettier to look at.

 

[davybyrne]

That's a nice little nearfield desktop setup. Have you tried separating the Q1 Meta loudspeakers a little more? I'm wondering if that could result in a preferred sound quality? If you have tried increased separation, I'd be interested to hear your thoughts on the results.

Interesting, I'll give that a try for a bit and see how it goes. I don't recall exactly how I chose the current placement other than intuitively.

As a simple experiment, you could place your two REL Tzero MkIII subwoofers together, centrally located under the desk. That may help inform you as to whether or not there are going to be any significant "modal smoothing" benefits of at your particular listening position using two subwoofers versus one single centrally placed one.

While I haven't placed the RELs in that position, I've auditioned several other individual subs in that position (JBL LSR310S, SVS 3000 Micro, KEF KC62, KEF Kube 8 MIE). The current setup with the RELs flanking the desk has been the best sounding so far, though to be honest I didn't have the UMIK-1 available for all of those other setups so I don't have objective data to compare. A grave sin in this forum, I know .

Having seen the results step response measurements of a variety of subwoofers, one would ideally need to have some idea of how a subwoofer measures when responding to a step input signal. There are many subwoofers out there that don't seem to do particularly well on this particular test.

Frequency response-wise, the Rythmik L12 (sealed, servo) 12-inch subwoofer seems to offer a nice improvement over the much more limited bass extension offered by the smaller REL Tzero MkIII subwoofer.

I have a Rythmik LV12M in my living room 5.1 home theater setup. I'm going to lug it up here and do some testing with it to have another point of comparison. If that performs well, I'll probably give the L12 a shot

 

[davybyrne]

If you want more targeted advice keep your plots at 50dB range with some 1/12 or 1/24 smoothing (as anyone else here, instead of the 400(!) dB you show now) and even better, include the .mdat (zipped) of the measurement.

That make total sense. I'm still getting used to REW and its … let's say "quirky" interface.

 

[davybyrne]

As said by others here you can get better for the money

Yeah, that's what I was thinking in posting this thread. In hindsight, the pair of RELs for $1,100 just didn’t make sense.

[taps username] your in-room response is looking very flat, are you listening at very high volumes? If not you'd want more of an upwards shelf at around 100hz

I'm looking for peaks of 85 – 90 dB at 1m (at least I think that's the right way to characterize it).

If not you'd want more of an upwards shelf at around 100hz, something vaguely resembling this though the size of the shelf will vary by preference and how loud you listen (louder = less bass shelf)

What's the best way to implement that shelf? For the miniDSP's PEQ I saved the filter coefficients from REW and loaded them into the miniDSP console. That seems to have taken up the 10 available biquad filters on the miniDSP inputs. Would I add that shelf onto the miniDSP outputs? Or adjust the PEQ somehow before exporting it from REW? Any guidance appreciated as I'm new to these tools.

 

[robh36062]

Could you share the specifics of the crossover you have (brand and where to get it)?

Sure I have a old JBL M552 that I got off E Bay years ago. A current alternative could be the DBX 223xs. It has all the functionality you would need, Polarity, Level and Frequency adjustment. You can do Mono summed or Stereo bass depending on settings. There is a review here on the site. It's not SOTA but it does the job. I have the DBX 234xs in my active set-up and it works fine even with a 98 dB sensitive system. Worth a look as a low cost active alternative too bass management if not available.

Rob

dbx 223xs Crossover Review

This is a review and detailed measurements of the dbx 223xs active analog balanced crossover. It is on kind loan from a member and costs US $245. I must say this is a nice and sturdy package for such a bargain price. Controls feel nice as well. Functionality though is confusing given the...

www.audiosciencereview.com

 

[levimax]

OP, as mentioned in his first post, has a Mini-DSP, he has no need of any other DSP.

 

[robh36062]

OP, as mentioned in his first post, has a Mini-DSP, he has no need of any other DSP.

Ok but he asked me what I was using' Also not DSP active analog. Clearly not the same.

Could you share the specifics of the crossover you have (brand and where to get it)?

Rob

 

[levimax]

Ok but he asked me what I was using' Also not DSP active analog. Clearly not the same.

Ooops missed that, sorry.

 

[LTig]

If one is using 2x REL Tzero MkIII subwoofers in their setup, then the cost of one KH750DSP is only 2549/(2*949) = 1.34 times higher (34%), not triple the price.

Oops - I paid less than € 1500 a few years ago, and the current price at Thomann is below € 1600. But here is not the US ...

 

[Krit]

While I haven't placed the RELs in that position, I've auditioned several other individual subs in that position (JBL LSR310S, SVS 3000 Micro, KEF KC62, KEF Kube 8 MIE). The current setup with the RELs flanking the desk has been the best sounding so far

Are you using LFE or High Level Input ? Does it sounds more musical than other subs less mechanical noises/quieter operation. Also looking at rel for nearfield listening.

 

[davybyrne]

Are you using LFE or High Level Input ? Does it sounds more musical than other subs less mechanical noises/quieter operation. Also looking at rel for nearfield listening.

I was using the line-level input.* Aside from a problem I had with a KEF KC62, which I believe was a defective unit and therefore returned, I've not seen any subs with mechanical noise or other operational issues.

With appropriate room correction, cross-over, and delay, I can't discern a difference that I would subjectively describe as "more musical."

*I don't buy into REL's marketing about high-level inputs. Giving a full-range signal to a sub that is then going to be low-pass filtered doesn't make sense to me. Their line about capturing "the sonic signature of your main system" doesn't pass the sniff test.

 

[Krit]

*I don't buy into REL's marketing about high-level inputs. Giving a full-range signal to a sub that is then going to be low-pass filtered doesn't make sense to me. Their line about capturing "the sonic signature of your main system" doesn't pass the sniff test.

In theory yes but did you tried it in practice?

 

[Redacted]

Do the subs being discussed not have internal DSP filers with cross-over point control knobs?
If so, is there any value in concatenating a miniDSP with the sub's own DSP? That could be ADC->DSP->DAC->ADC->DSP->DAC, depending on how these things can connect....