[medium jim]

This is hopefully a good topic and was prompted by reading the spec's on a sub wherein it had a fixed high pass of 100hz, but an adjustable low pass between 50-180hz and recommended at setting of 80hz.

Wouldn't that create a situation where there was no signal between 80-100hz? 

Jim

[WC]

I guess it wouldn't make using the high pass outputs very useful, unless you crossing over higher than 100Hz. How can a sub have a recommended setting? 

Shouldn't the low pass setting on the sub be more a function of the speakers you are running with it?

Many subs are getting rid of high pass outputs since a majority of subs are purchased for HT, where high pass outputs are not necessary.

[medium jim]

If you plan on running the mains full then you don't need to high pass, but that leads to duplication of frequencies, which can be fine.  I like the idea of being able to set the low pass and high pass where there is no overlap or underlap.  Is it important?

Jim

[medium jim]

Here's an interesting read about using high pass filters from a musicians point of view:

http://www.gollihurmusic.com/faq/38-HIGH_PASS_FILTERS_GETTING_RID_OF_THE_MUD_AND_RUMBLE.html

Jim

[Quiet Earth]

I've done a little bit of amateur mixing at home, and I have been the guy in charge of the mixer at a few gigs. I can empethize with the message in that article. Sometimes the best thing you can do to get some space between tracks, or to get everything to sit nicely in the mix is to cut almost everything below 30Hz.

In other words, high pass filter.

I think that article is actually a good argument for not owning a sub in the first place. Those lowest of low frequencies that we think we should be hearing may not be on the recording anyway. Think about it. They're high passing the low end to clean up the mud in a jam session or a gig. Don't you think they might do the same in a recording studio too? I personally think we own lots of albums with nothing existing below 30 or 40 Hz.

This doesn't mean we don't have great bass or its not worth persuing. It just means that bass needs to be limited and controlled for better balance. A subwoofer might be the least thing you need.

[JerryLove]

I think that article is actually a good argument for not owning a sub in the first place. Those lowest of low frequencies that we think we should be hearing may not be on the recording anyway.

Except when they are. I can name a large number of my audio recordings with significant SPL below 35Hz; and movies with harmonics below 20.

But let's imagine that the useful information did stop at 40Hz on what you were listening to. If you are running a B&W 801 then no problem. You are all set.

But what if you are running, say, as pair of Salk SCST's. Very good speakers. My favorites in my home. And they are flat to 32Hz.

OTOH, when I run them at high volumes, I get mechanical clipping. At those same volumes, with a sub handling below 80Hz, no problems. Same with my Paradigm S2's.

Think about it. They're high passing the low end to clean up the mud in a jam session or a gig. Don't you think they might do the same in a recording studio too? I personally think we own lots of albums with nothing existing below 30 or 40 Hz.

Likely true for some albums; and if you don't mind losing some of the rest you are all set... assuming that you can play the SPL you want at 40Hz.

This doesn't mean we don't have great bass or its not worth persuing. It just means that bass needs to be limited and controlled for better balance. A subwoofer might be the least thing you need.

I think it just needs to be given to a capable component.

[Davey]

This is hopefully a good topic and was prompted by reading the spec's on a sub wherein it had a fixed high pass of 100hz, but an adjustable low pass between 50-180hz and recommended at setting of 80hz.

Wouldn't that create a situation where there was no signal between 80-100hz? 

Jim

I think you're misinterpreting the specs for that subwoofer(amp.)  The fixed 100hz high-pass is no doubt for the feedthrough to the main speakers and not applied to the subwoofer.  The adjustable low-pass is for the subwoofer and not applied to the main speakers.
Some subwoofer amps provide a high-pass for the subwoofer as well......but it would most likely be at a frequency considerably below 100hz.

Cheers,

Dave.

[medium jim]

I think you're misinterpreting the specs for that subwoofer(amp.)  The fixed 100hz high-pass is no doubt for the feedthrough to the main speakers and not applied to the subwoofer.  The adjustable low-pass is for the subwoofer and not applied to the main speakers.
Some subwoofer amps provide a high-pass for the subwoofer as well......but it would most likely be at a frequency considerably below 100hz.

Cheers,

Dave.

Exactly, no confusion.  Except, to have dual high pass filters doesn't make sense. To that end, I run a high pass between the sub and mains to assure that when I have the subs low passed at say 60hz, the high pass to the mains is also @ 60hz.

Jim

[kevin360]

I think Jim is hinting that one could set the sub's low pass at 50Hz, which would leave a gap below what is fed to the mains. I should think that if one's high pass is fixed, then it pretty much suggests where the low pass setting will have to be - if one uses the sub to roll off the bottom end of what the mains get. The variability of the low pass setting comes in handy in other configurations. A fixed high pass could be chosen for one of two reasons - cost or performance (or a combination of both - better performance at a particular price point). The adjustable low pass is pretty much a requirement.

(edit)
Hmm, I think Jim expanded his initial response - making mine somewhat redundant.

[medium jim]

Kevin:

Correct, I was blown away when I read it in the user manual (online).  I think that most subs are still being made for HT and not home audio. Scary is that is was from what would be a respected audio speaker maker, Gallo. 

I have to wonder how many other subs also employ a fixed high pass and this results in a suckout or a peak?

Jim

[Quiet Earth]

I guess I don't understand why you linked that article Jim. I thought you were going somewhere else with the topic.

[medium jim]

QE:

It can in that direction also, I found the article interesting and posted it. The difference between live or studio is that you are trying to capture live performances versus home where you are attempting to replicate them and each has different problems in doing so.

Jim

[ricardojoa]

What does the number on the crossover means? Can it be interpret as the roll of point?

[medium jim]

What does the number on the crossover means? Can it be interpret as the roll of point?

The x/o setting on most subs is the low pass roll off to the subs. Where I got miffed was that some or maybe many employ a fixed high pass filter.

Jim

[ricardojoa]

That depends on the slope for the fixed 100 hz. Shallow roll like 6 db will be down 50hz, consideting room gains, it may not be a big deal where you cross your sub.

[medium jim]

That depends on the slope for the fixed 100 hz. Shallow roll like 6 db will be down 50hz, consideting room gains, it may not be a big deal where you cross your sub.

What happens when you set the x/o point at 120 or higher though? Even with a 6db or even 12db slope, it still is not an exact thing and many find themselves chasing suckouts or peaks.   The issue is cost I suspect and built in compromises. 

Maybe I'm wrong and the science says it is okay, and this is a non sequitur.

Jim

[ricardojoa]

The only thing i can think someone setting that high is becuse they are using sattalites speakers.

[WC]

The x/o setting on most subs is the low pass roll off to the subs. Where I got miffed was that some or maybe many employ a fixed high pass filter.

Jim

Every sub amp that has outputs can have the outputs be high passed at a fixed frequency, passed at a variable frequency, or pass the full range signal. They may exist, but I am not familiar with any subs with a variable high pass frequency. A fixed frequency high pass is most likely just a capacitor inline. Passing the full range signal is the easiest, but if you go through all the trouble of having outputs why not put a cap inline and call it a high pass output.

The sub you were looking at was a Gallo sub, right? They are purchased with the Gallo round sattelite speakers which can barely get below 100 Hz. So a 100 Hz high pass could work if someone wanted a 2 Channel system with sats and a sub.

[medium jim]

WC:

I agree that High Passing post sub is very effective.  The Gallo wasn't necessarily recommended for their sat's and recommended a low pass of 80hz. 

Jim