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Speakers and Subs - FR or XO?

GDK

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#1
The received wisdom on ASR seems to be that you should always have some form of a cross-over between your mains and your subs. However, is this really always true? Does it matter, for example, on whether you have a pair of 2-way bookshelves versus large 3-way floor standers? Is it more relevant for active systems versus passive systems? Does it make a different whether or not you are using DRC?

I have an RME DAC feeding my integrated amp. My passive speakers are connected in the normal way and I use the pre-outs on my amp to feed my subs. I have tried putting a MiniDSP 2x4 (not HD) in between the DAC and the amp, but I took it out as it introduced a buzz into the system. When I removed it, I did not notice any degradation in the sound quality, but I have fairly indiscriminate ears.

One of the main benefits of high passing your mains is that it will result in lower LF distortion. However, Erin’s recent review of the Dutch * Dutch 8Cs showed that they have significant LF distortion and yet it did not seem to be an issue for his (or anyone else’s) listening test. Therefore, is LF distortion really an issue that we should be concerned about?

https://www.audiosciencereview.com/forum/index.php?threads/dutch-dutch-8c-review.21016/post-696724

1618615573251.png

The other stated advantage is that it will relieve your amp from having to deliver the significant power that your mains require to deliver LF content. However, if your amp is sufficiently powered, again, to what extent is this a real problem?

On the other side, if you are running your mains full range then you will have multiple bass sources that could (should?) help with room correction. It also means, in the case of a passive system at least, avoiding the introduction of another component with the potential of adding distortion, ground loops, etc.

Anyway, I am curious as to the views of the community here. I assume that I am missing something important when I think about this.
 

RPG

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#2
Google "Earl Geddes, subwoofers" for one point of view on this. There are a number of other experts that subscribe to the crossover at "xxhz", too. Seems to be kind of a "pick whichever one suits you and your gear, and give it a try" area....not one where there is definitive and uniform agreement. At least that's what I've concluded in my various readings.

Geddes' approach suits my situation to a "T", but I have some fairly unique circumstances. Two new SVS subs arriving next week, so I'll definitely be giving the Geddes method a try, shortly, and will see what results I get.
 
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GDK

GDK

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Thread Starter #4
Google "Earl Geddes, subwoofers" for one point of view on this.
I have seen Geddes’ commentary on the benefit of multiple subs (no controversy there I think) and optimal placement, but I have not seen anything specific to high passing your mains at the XO point. However, it is possible that I missed it in my search.
 

Pdxwayne

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#5
I like it loud.

Full range sounds good. But I prefer high pass my speakers with minidsp and then match it with a sub (match using REW).

Since I like it loud, when playing bass heavy music with speakers playing full range, I always sense a little of muddiness. High pass helps remove that muddiness.
 

waynel

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On the other side, if you are running your mains full range then you will have multiple bass sources that could (should?) help with room correction
this would appear to be an advantage but is not. there is no guarantee that your main woofers and the subs will be in phase at all frequencies at which they overlap. In fact it’s almost a certainty that they won’t and will cause interference patterns and less even response. This can’t be corrected by a simple phase adjustment as the phase difference varies with frequency.
 
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GDK

GDK

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this would appear to be an advantage but is not. there is no guarantee that your main woofers and the subs will be in phase at all frequencies at which they overlap. In fact it’s almost a certainty that they won’t and will cause interference patterns and less even response. This can’t be corrected by a simple phase adjustment as the phase difference varies with frequency.
Interesting. Would this issue be apparent in the FR measurement?
 

waynel

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Interesting. Would this issue be apparent in the FR measurement?
Yep, the impact will be in uneven frequency response. Also your main speakers will start to distort at a lower level than the subs limiting your headroom too.
 
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GDK

GDK

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Yep, the impact will be in uneven frequency response. Also your main speakers will start to distort at a lower level than the subs limiting your headroom too.
Thanks. I haven’t had that issue, but perhaps it is dumb luck, or perhaps Audiolense is doing something to address it. However, I am still not convinced that LF distortion is a major concern, given the results of Erin’s 8C tests that I noted above.
 

waynel

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Thanks. I haven’t had that issue, but perhaps it is dumb luck, or perhaps Audiolense is doing something to address it. However, I am still not convinced that LF distortion is a major concern, given the results of Erin’s 8C tests that I noted above.
Keep turning the volume up with bass heavy material and your speakers should reach 100% + distortion while your subs are coasting at 5% . I’m not talking about reaching 10-20% distortion , I’m talking distortion bigger than the signal and I guarantee it’s audible.
 
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RPG

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I have seen Geddes’ commentary on the benefit of multiple subs (no controversy there I think) and optimal placement, but I have not seen anything specific to high passing your mains at the XO point. However, it is possible that I missed it in my search.
Quoting Geddes [In all of this, he's talking about integrating multiple subs.]: " Overlap with the mains is unusual in my approach. Most people would suggest a crossover, but for a number of reason, this doesn't work very well (crossover all the subs at the same point?). How will this add up at various places around the room? Basically it doesn't work.

I suggest that the mains and the subs overlap, in other words they are all playing at the same time at some frequencies......the overlap concept is mostly between the mains and the first sub."

If you want to read the full article on his suggestions for setting up multiple subs, you can find it here:

Earl Geddes, Setting Up Multiple Subs, 2011.pdf - Google Drive
 
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GDK

GDK

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Quoting Geddes [In all of this, he's talking about integrating multiple subs.]: " Overlap with the mains is unusual in my approach. Most people would suggest a crossover, but for a number of reason, this doesn't work very well (crossover all the subs at the same point?). How will this add up at various places around the room? Basically it doesn't work.

I suggest that the mains and the subs overlap, in other words they are all playing at the same time at some frequencies......the overlap concept is mostly between the mains and the first sub."

If you want to read the full article on his suggestions for setting up multiple subs, you can find it here:

Earl Geddes, Setting Up Multiple Subs, 2011.pdf - Google Drive
That’s interesting. I will have a read. Thanks for that!
 

Duke

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#13
@Duke would have insight I would think.
Imo it depends on the specific situation.

If the woofers in the mains risk being driven beyond their linear excursion limits, and/or if the amplifier for the mains would risk being pushed into clipping, and/or if distortion becomes objectionable without a protective highpass filter, then imo using one would be a very good idea. Earl Geddes uses prosound woofers in his main speakers which are unlikely to be pushed into distress by loud fullrange signals in a home audio application (and so do I), in which case a protective highpass filter is not necessary.

Speaking only for myself here (as I'm not sure of Earl's thinking on this subject), one of the reasons I prefer to make main speakers with enough excursion headroom that a protective highpass filter isn't necessary, is because some people would rather not have the additional circuitry in their main signal path.

The subwoofer system I manufacture uses an amplifier with a built-in 80 Hz second-order line-level highpass filter, which can be inserted into the signal path or bypassed, depending on the situation.
 
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wgb113

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#14
Check out the latest installment around getting good bass from Audioholics. The series Gene’s been doing with Anthony Grimani’s been very thorough and the latest installment covers crossover settings, both HP and LP.

 

q3cpma

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Imo it depends on the specific situation.

If the woofers in the mains risk being driven beyond their linear excursion limits, and/or if the amplifier for the mains would risk being pushed into clipping, and/or if distortion becomes objectionable without a protective highpass filter, then imo using one would be a very good idea. Earl Geddes uses prosound woofers in his main speakers which are unlikely to be pushed into distress by loud fullrange signals in a home audio application (and so do I), in which case a protective highpass filter is not necessary.

Speaking only for myself here (as I'm not sure of Earl's thinking on this subject), one of the reasons I prefer to make main speakers with enough excursion headroom that a protective highpass filter isn't necessary, is because some people would rather not have the additional circuitry in their main signal path.

The subwoofer system I manufacture uses an amplifier with a built-in 80 Hz second-order line-level highpass filter, which can be inserted into the signal path or bypassed, depending on the situation.
Why do you think protection is the only goal? Unless you have a 4-way or special 3-way speaker, reducing IMD (and THD, but less important) seems like a better goal.
 

sigbergaudio

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#16
I wouldn't base my choices here on the DD 8C measurements. They've done a number of very well thought out compromises that's not automatically applicable or relevant for what you are discussing here. It's also hard to know the true distortion here as opposed to effects of the bass having to travel from the back of the cabinet.

The only true way to find out for your particular situation is to measure and experiment. But in general terms high passing your mains will indeed do all the things mentioned: Reduce low-end distortion, increase headroom and likely also give a more even frequency response.
 

Jim Matthews

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I run a Highpass filter at 100 Hz to my mains to tame port resonance.
This has reduced coloration of acoustic guitars and baritone vocals.

I'm similarly confident that amplifiers can support bass response, even with small(er) drivers such as a 6.5"/165mm woofer. At the lowest extreme I suspect it's more about placement near boundaries than straight output.

In my opinion, it's more important to get subwoofers integrated in a room.
Exaggerated bass is intrusive and distracting.
 

Duke

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If you want to read the full article on his suggestions for setting up multiple subs, you can find it here:

Earl Geddes, Setting Up Multiple Subs, 2011.pdf - Google Drive
I have tinkered quite a bit this last year and the Geddes approach defiantly gave me the best and smoothest integration of the subs to the main.
Here is what I did:
- Run the mains full range (you may need to plug the port on ported speakers to protect the low end / max excursion)
- Run the sub full range with your desired low pass filter based on their location (they become more localizable the higher the frequency, so one sub front and center is at 180hz and is not notable, the one in the rear I have at 60hz as it digs down the lowest and I don't want it localizable).
- Get the crossover region optimized with changing the sub (and / or speaker distance).
- EQ as needed
- Enjoy!
 

q3cpma

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#20
Mais je n'ai pas dit que "protection is the only goal".
Sorry, maybe my misunderstanding, but pro woofers won't have necessarily less distortion, but higher power handling (i.e. more headroom before falling apart). So even then, unless you have basically an integrated subwoofer (e.g. Salon 2), it would make sense to high-pass them; and possibly to turn a ported system into a "ported with an unexcited port" one.
 

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