rel Subwoofer Integration

[davewantsmoore]

1 hour ago, almikel said:

The presumption is that if the feedback circuit caused additional delay, it couldn't help maintain driver control.

It works more like negative feedback in an amplifier, rather than a filter

These sorts of delays are all very short.... much(!) shorter than the sort of delays we're talking about wrt speaker crossovers and time alignment.

[andyr]

1 hour ago, almikel said:

exactly the same as any other filter of the same slope and frequency.

All filters cause delay - it's just that the delay increases with increasing filter slope, and reducing frequency (delay is inversely proportional to frequency), so it makes a bigger difference at sub frequencies.

 

I'm sure there's delay calculators on the googleweb - but some points to note:

• for IIR non-linear phase filters (analog and DSP), the delay is variable (non zero Group Delay) depending on frequency, but the variable delay is typically less than FIR linear phase filters
• for FIR linear phase filters (only possible with DSP), the Group Delay is zero, so the delay across all frequencies is constant, but the delay is more than IIR filters, and requires more compute power (filter "taps") the steeper the filter and the lower the frequency. The propagation delay for the "compute" part is still infinitesimal compared to the inherent filter delay defined by physics

cheers

Mike

 

Thank you for explaining it to AG, Mike. 

 

12 hours ago, AudioGeek said:

Thanks Andy. So how much delay would you expect under 80Hz?

 

Can't tell you for 80Hz ... but the delay introduced by my sub plate amps' 24dB @ 100Hz LP filter was ~5ms.  Combined with the fact that my subs are about 1.3m further away from my ears than my woofers ... means that I have a 9ms delay on the mains.

 

12 hours ago, AudioGeek said:

Never really heard of timing being an issue with these subs

 

The delay - as I think Mike pointed out - has got nothing to do with the 'sub' per se ... simply the LP filter which the sub is using.

 

And the fact that there's so much angst about "integrating subs" on the web ... simply means that those who can hear 'issues' with their system are not implementing delay.

 

Andy

 

[Byron Scholar]

Thanks for all the responses!

 

In response to the people saying you need to EQ a sub with high pass filters on your speakers and so on. Why do no subwoofer brands state this or recommend this? I haven't seen any brands do it anyway. Even in they're instruction manuals for setting up the sub.

 

Even if they did recommend it I probably wouldn't bother anyway. It'll be fiddly enough getting the crossover, level, and position right. Sometimes I think I'm being too fussy! Then I see people go to the lengths like you guys. Ain't got time for dat!

[Byron Scholar]

On 24/08/2018 at 4:33 PM, GroovyGuru said:

I might be putting my pair of Rel s2 up for sale.  Keep an eye on Classifieds.  I got them to work with MG 20.7.

A couple of questions if you don't mind me asking? How much did you originally pay for each of them? And where are you from?

[davewantsmoore]

10 minutes ago, Byron Bae said:

Thanks for all the responses!

In response to the people saying you need to EQ a sub with high pass filters on your speakers and so on. Why do no subwoofer brands state this or recommend this?

 

Various reasons.

 

Home theatre/AVR take care of this for you  (ie. crossing over the bass to the 'other speakers')

 

You don't necessarily need a high pass filter on your main speakers..... If for example, your main speaker has a natural 12dB/octave high pass rolloff below 60Hz .... you could just match the subwoofers lowpass filter to be 12dB/octave above 60Hz.     

 

The don't want to "scare people off" by "explaining stuff" .....   just give your money, and take "awesome subwoofer" home, and get woofing.   They don't much care if you've set it up right - as long as you've paid your money.    Joe on the street, isn't likely to buy a subwoofer if there's <danger: complex stuff>

 

Quote

Even if they did recommend it I probably wouldn't bother anyway. It'll be fiddly enough getting the crossover, level, and position right. Sometimes I think I'm being too fussy! Then I see people go to the lengths like you guys. Ain't got time for dat!

Exactly.   

 

Meanwhile the reality is that the adjustment trumps just about everything .... but the manufacturers can't sell that (so they'll never say)

Edited September 14, 2018 by davewantsmoore

[andyr]

15 minutes ago, Byron Bae said:

Then I see people go to the lengths like you guys. Ain't got time for dat!

 

So you're a "plug'n'play" guy, BB.  Nothing wrong with that - it simply means that you are happy with good sound with a minimum of effort ... rather than great sound with a lot of effort.  I'm in the latter camp. 

 

Andy

 

[almikel]

8 minutes ago, Byron Bae said:

In response to the people saying you need to EQ a sub with high pass filters on your speakers and so on. Why do no subwoofer brands state this or recommend this?

because sub manufacturers want to sell more subs and proper integration is hard, so they don't include anything "hard to do" in their blurb...

Your thread title is "Subwoofer Integration" - so the community of SNA is providing responses on how to achieve sub integration.

 

17 minutes ago, Byron Bae said:

Even if they did recommend it I probably wouldn't bother anyway. It'll be fiddly enough getting the crossover, level, and position right.

good sub integration is not trivial, but worth it.

 

18 minutes ago, Byron Bae said:

Sometimes I think I'm being too fussy!

depends if you want good sub integration - possibly not fussy enough

 

Mike

[WorkinClassAudio]

20 hours ago, Byron Bae said:

A couple of questions if you don't mind me asking? How much did you originally pay for each of them? And where are you from?

Both RELs were sold within 48 hrs of listing.  No further correspondence will be entered into.

[A9X]

On 14/09/2018 at 9:49 PM, davewantsmoore said:

You don't necessarily need a high pass filter on your main speakers..... If for example, your main speaker has a natural 12dB/octave high pass rolloff below 60Hz .... you could just match the subwoofers lowpass filter to be 12dB/octave above 60Hz.

I really hate nit-picking you Dave, but I still don't agree. There are few speakers with a 12dB roll off, and they would be sealed. Most will have closer to 24dB a la a typical ported and they are still going to need a high pass to prevent over excursion below tune (mains). Unless of course the manufacturer has cheaped out with too small a port and are using it's compression to limit it. Phase matching with a non HPF'd ported mains and a sub can be an issue too and I've heard some really odd sonic effects when this is done.

Even with your hypothetical sealed mains, the excursion will still increase markedly, if less than a ported near roll off, and reducing that with a HPF can lead to decreased distortion in the midbass/midrange and potentially cleaner SPL, especially at higher levels, even just transients.

 

It can be made to work OK, but as per my first post, it's far from properly (optimally). In the end it's up to the punter to decide cost/benefit, and I'm only commenting to put out an alternative view, based upon lots of experience doing it.

[A9X]

On 14/09/2018 at 10:03 PM, almikel said:

because sub manufacturers want to sell more subs and proper integration is hard, so they don't include anything "hard to do" in their blurb...

Bingo.

[davewantsmoore]

1 minute ago, A9X said:

I really hate nit-picking you Dave, but I still don't agree.

<snip>

It can be made to work OK,

That's why I wrote you don't necessarily need to add an extra high pass filter.

 

If your speaker already happens to have a high pass response which is appropriate .... then you don't need to change it.

 

That word "appropriate" is complicated.   Examples:

 

• Is your main speaker high pass response match the low pass you will achieve with you subwoofer?   No?  Then you'll have to change it (by adding some sort of filter, perhaps an extra high pass filter).

• Do you want/need to reduce the excursion of the main speaker?    This might be a good idea, but it is not always necessary.

 

6 minutes ago, A9X said:

Even with your hypothetical sealed mains, the excursion will still increase markedly

No that's incorrect.

 

If the SPL decreases by a (hypothetical) 12dB per octave as the frequency is reduced, the excursion remains constant.

 

Thus more than 12dB/octave high pass response will reduce the excursion as the frequency reduces..... and less than 12dB/octave high pass response means that the excursion increases as the frequency reduces.

 

8 minutes ago, A9X said:

I'm only commenting to put out an alternative view, based upon lots of experience doing it.

I think most people will probably benefit from adding some sort of filter to their main speakers, in order to match the response of the subwoofer.     *we agree*

 

Filtering the main speakers isn't always necessary though .... but as the natural main speaker response won't be perfectly *anything*  (eg. 12, or 24dB per octave) .... then the simple low pass filters built into most subwoofers won't be ideal in producing a response which matches the main speaker.

 

 

[A9X]

33 minutes ago, davewantsmoore said:

No that's incorrect.

 

If the SPL decreases by a (hypothetical) 12dB per octave as the frequency is reduced, the excursion remains constant.

Badly worded on my part, but in the octave before roll off excursion will increase (as it needs to to maintain SPL) and depending upon where you add the HPF, much of that excursion may be reduced, for reduced distortion etc. Just because a speaker naturally rolls off at 12dB / 60Hz doesn't mean that's where I'd actually cross it.

 

37 minutes ago, davewantsmoore said:

*we agree*

I know. It was added for other less technical readers to have an understanding of the whys and wherefores so they can make a more informed decision.

[davewantsmoore]

2 hours ago, A9X said:

Badly worded on my part, but in the octave before roll off excursion will increase (as it needs to to maintain SPL) and depending upon where you add the HPF, much of that excursion may be reduced, for reduced distortion etc. Just because a speaker naturally rolls off at 12dB / 60Hz doesn't mean that's where I'd actually cross it.

Definitely....  but it all just depends on how capable the speakers are and how hard we push them.    

 

2 hours ago, A9X said:

I know.  It was added for ....

I know you do   

 

The *we agree* was also added for everyone else.    To often bystanders conclude that "nobody agrees, therefore audio is all powered by stuff nobody understands".

 

[almikel]

all of the above by @A9X and @davewantsmoore demonstrates the complexity of good sub/mains integration.

 

In my case my main speakers (TD18s) naturally roll off around 90-100Hz in their small boxes, so I add gobs of EQ to push them lower. Even when pushed down to 20Hz at "reasonable" SPL the TD18s stay below Xmax, and their amp never clips, but the cooling fan certainly operates much more.

 

My sub has a resonance around 90 Hz (tapped horn) so I low pass the sub around 50Hz with an LR24 crossover.

 

I've tried having both a big overlap for more bass sources (TD18's pushed well below 50Hz), and crossing the TD18's at 50Hz.

After EQ of the overall room response, both options sounded great - I couldn't say which was "better".

 

Different integration approaches can work, but it's about putting the effort into the chosen integration path to make it work.

 

cheers,

Mike

[zeus]

so if a sub has a high pass and low pass filters would it be better to have them set the same or the high pass set higher ?

[A9X]

2 hours ago, zeus said:

so if a sub has a high pass and low pass filters would it be better to have them set the same

Generally, I would say always, the same.

[almikel]

6 hours ago, zeus said:

so if a sub has a high pass and low pass filters would it be better to have them set the same or the high pass set higher ?

 

4 hours ago, A9X said:

Generally, I would say always, the same.

Agreed - keep them the same.

 

The approach of having mains overlap with the sub so that you have additional bass sources in the room is valid but is more complicated requiring integration of 3 bass sources (stereo main speakers + sub) to be managed.

 

Overlapping mains and sub can easily lead to muddy bass. If you have 2 or more subs it's not required, and overlapping is only useful when you only have a single sub, and your mains can cope with low bass (ie can hit the SPL target at the required frequency with low distortion).

Then you need a measurement rig and DSP to time align and EQ the room response.

 

Much easier to cross mains to sub at the same frequency...

 

...but IMO you still need a measurement rig and DSP to time align and EQ the room response to achieve good mains/sub integration.

 

6 hours ago, zeus said:

would it be better to have them set the same or the high pass set higher ?

presumably a typo? setting the high pass on the mains higher than the low pass on the sub will produce a dip - a guaranteed poor integration result.

 

cheers

Mike

Edited September 20, 2018 by almikel

[zeus]

you are correct it should say low pass set higher thanks for the advice guys

Mike