Question for the Experts - REW - Sub + Mains - Large vs Small Settings?

Medrep1

Active Member
When calibrating with REW, as many of us do, using our main L/R and sub, we are looking for a flat response as much as possible, yes?

Minor adjustments of crossovers and spl levels for speaker and sub play a massive role in the frequency response/graph, to which we can spend hours doing?

But what about the other speakers, such as centre and rears, surely these would affect the 'flat' response we have just been trying to acheive when the film is playing?

According to my Rotel manual regarding speaker settings and sizes, it states that having 'capable' speakers able to reproduce 'the sound recorded for each channel individually' should be set to large. Any LFE effects recorded will be sent to the dedicated subwoofer. Still with me?

So I read into this as basically the film has intentionally recorded specific bass/midrange/high/ frequencies corresponding to each channel, and specific LFE sound for a dedicated sub. Therefore, where does the THX recommended 80hz crossover come in, if the film has more information present than your allowing it to play through each channel?

The purpose for this thread is to establish what exactly is the ideal set up regarding speaker choices and settings.

Now, having all my speakers set to large, and the sub using its own crossover, set at the natural roll off from the main speakers, is giving me a much more cohererent sound, particularly with regards to the bass. I feel the sound is a lot more richer, mostly noticable on dolby pro logic material, where initially at a 80hz crossover it sounded light and weedy.

So before I waffle on and confuse myself more, any thoughts on this, as I have more......!
 

SBanga

Well-known Member
I'm not an expert but if it sounds better to you then why change it? There may be accepted ways of doing things but if you prefer your sound a certain way, stick with it. My crossover is at 80Hz for my center and rears but I have the same problem as you if I set my fronts to 80Hz too. For this reason, they're set at 60Hz, which to my ears, fills in the bass considerably and gives action/music scene a lot more "punch".
 

Medrep1

Active Member
Thanks Sunil. My point being though is why are we busting a gut trying to get our systems crossed over at specific hz to the sub, when films have encoded specific frequencies to each channel.

Would it not be the ideal target (in a perfect world) to have full range speakers all round and suitable amps, with just the sub handling specific LFE effects, say 20-30hz below the speakers?

Are we not defeating the object of trying to reproduce film accurately where crossovers are set so high the channel is not playing the frequency intended?

Am I being stupid?
 

Mackle

Active Member
My point being though is why are we busting a gut trying to get our systems crossed over at specific hz to the sub, when films have encoded specific frequencies to each channel.

Would it not be the ideal target (in a perfect world) to have full range speakers all round and suitable amps, with just the sub handling specific LFE effects, say 20-30hz below the speakers?

Are we not defeating the object of trying to reproduce film accurately where crossovers are set so high the channel is not playing the frequency intended?

This might be one to take to AVSforum, as one of the Audyssey founders is on there so has either answered this one before or can answer it.

In the meantime though, I did find this :-
Audyssey | Blog Archive | Small vs. Large


Not sure if it is a useful starting point?


I am going through the same process of racking my brains trying to figure out what sounds best to me in my living room, a crossover somewhere between 40 and 80 or just setting the speakers to full range - and I've only got a little (albeit reasonably punchy) set of bookshelves for my front channels so must be even harder when you've got big floorstanders! :D
 

kit1cat

Active Member
I set my sub eq , sms-1, in 5.1 mode on the amp to allow for all speakers. It gave a slightly different graph then when in stereo mode.

You are not losing bass by setting all speakers too small, by sending it to the sub your are likely hearing more bass then letting your center/surrounds handle it.

Came across this article a while back

http://www.ultimateavmag.com/howto/805bass/index.html
 
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AngelEyes

Distinguished Member
If you set your speakers to small, any material in that channel recorded below that frequency is not lost, it is simply redirected to the subwoofer. By setting your speakers to large all you are doing is asking them to reproduce frequencies they are probably not designed to do very well which is resulting in more audiable distortion.

Please don't take this as an insult as of course I am only guessing but it is possible the distortion that is now added to the soundtrack is the added 'richness' you are hearing.

I know many people including myself have complained of a los of bass when first purchasing a very clean distortion free subwoofer. it took me a while to realise what I had spent my life in clubs and bars thinking was bass, was actually loads of distortion. Some people really don't like it and will never accept it even if it is technically more accurate.

The best thing to do is choose the sound you like the best regardless of what anyone else thinks. :)

On the other hand rather than jump to conclusions I should ask what steps you have taken to setup your system (SPL Meter, Room EQ Wizard, Audyssey etc.) in case you bass is 'light & weedy' for some other reason that could be rectified?

Adam :)
 

Medrep1

Active Member
Thanks for the replies!

Ive just been spending the last 3 hours with REW, going round in circles:suicide:

Basically, the most 'flattest' response I can get is with the mains (small) passed at 40hz to the sub. I would post the graph ive just done but it didnt save?

If I set anything higher to the sub, say 60hz or 80hz, there is a huge peak at 35hz (approx 15+db's) and then a huge drop at 50-70hz.

Mains at 40hz looks the best, so on instinct I set them to large, and the bass was deeper and more powerful. Set all speakers to large and it sounds perfect. I wont turn it up anywhere near ref level though for fear of damage or clipping.

I have been researching the Large v Small saga for the last few days, and yes consensus is to set to small to not risk overloading the 5.0 channels with high spl levels of low hz's.

Please don't take this as an insult as of course I am only guessing but it is possible the distortion that is now added to the soundtrack is the added 'richness' you are hearing

None taken at all, you are probably right. But distortion of the bass is not a word I would describe with them all set to large, its tight, low and punchy?

I have been using transformers sd as a test disk since early this year, and know it very well. There is a scene around chapter 19 where one robot rugby tackles another on the highway. As it occurs, there is a wave of bass that just gets deeper and deeper. Anything other than a x over at 40hz or set to large (which sounds best imo) it just doesnt happen? The ironhide flip is also another where set as above, it seems deeper and tighter. X over at 80hz and it feels like distortion, maybe because im turning the sub up too much to compensate???

Im becoming royally confused and fustrated now, as I appreciate and acknowledge that set to small at a higher crossover is percieved as the safest and most beneficial in overall performance, but I just dont get it.

Th 803D's go down to around 35hz, so not that deep, the sub is a sunfire hrs12, which goes to 18hz. Am I wasting the sub set at 40hz, and risk damaging the 803's?

So, is:

my room bad,
the sub not enough for the 803d's,
or both?

Cheers:confused:
 

Nimby

Distinguished Member
REW saves its graphs to your Documents folder by default if you choose to save them. Not to Pictures as one might expect. To post your graphs here you will need to host them online. ImageShack, Photobucket etc are popular for this task. I don't think you even need to register. Uploading individual images without registration saves everybody going right through your entire image collection. When all you wanted them to do was talk about your frequency response. :oops:

It has been said so many times about large and small speaker settings: Small helps the speakers and amplifiers. Large makes them all work very hard and produce lots of distortion with falling frequency. But, if you prefer large to small then enjoy it. There are no rules where personal choice matters more than theory. The ideal situation is a variable crossover which allows fine tuning. It works for me.

You cannot blame room modes for your problems unless you are willing to move the subwoofer to the best point in the room according to REW. Subwoofers are like that. They trigger room modes because they put lots of power into a region the speakers can usually only dream about.
 

Medrep1

Active Member
Large makes them all work very hard and produce lots of distortion with falling frequency

Thanks Nimby. Your point there though raises my second query....

The Rotel manual basically states that having 'capable' speakers able to reproduce 'the sound recorded for each channel individually' should be set to large. Any LFE effects recorded will be sent to the dedicated LFE subwoofer.

So if the mains can handle down to 35hz, and your crossover is at 40hz, then in my mind your asking no more of the main speakers than if you were listening via normal stereo. If the speakers naturally roll off at 35hz, then isnt it percieved that they will not play anything below that?

As a result you are hearing the designated bass from the main speakers, (as the director intended) and LFE effects are ging to the sub, as the director intended.

Im not asking you directly, as you and others have already answered my question..... if it sounds good to you then go for it, which it does. I just dont want to risk damaging anything, but want the best out of my system!

I see B&W and Rotel are in the same room at the Manchester show, so i'll ask them the same questions:D:D
 

AngelEyes

Distinguished Member
Just because your speakers have a -3dB point of 35Hz (even if that is true) doesn't mean the output is clean, just that some noise is coming out of them and it increases in distortion the more you ask of the speakers.

'Capable' speakers that can be compared to a good dedicated subwoofer are likely to cost many thousands of pounds each and are not generally a great idea as multiple bass sources are as likely to cancel each other out as benefit, hence the wisdom in a single bass radiator.

I already answered your question about how the bass is sent to the subwoofer and that no sound is missed from the recording, it is simply sent the most capable sepaker to reproduce it (the sub). Bass being omnidirectional from around 80hz down suffers no ill effects being sent to the sub as it will still 'sound' like it is coming from the direction the director intended, steared by the more audiable upper bass from the relevant speakers.

You mentioned in your first post about the best sound should be with REW showing a flat plot. I completely disagree with this, REW is just a tool and you need to undertand what is happening in your room in order to use it properly.

From what you describe, you have a fair amount of interection between your speakers and your room and you need to determine exactly what is happening. My guess is you have some room modes and different speaker crossovers are causing interaction between speakers and sub that makes the response 'look' better when set at large because it is flatter but you are replacing what could be clean bass from the sub with distorted bass from the speakers.

In order to see what is realy happening you need 3 or more REW plots.

1. Subwoofer only
2. Speakers only (large, small or both)
3. Speakers & Subwoofer (large, small or both)

This should give a clear picture of what is going on and how to cure it. My suspicion is that you have a 35-ish hz mode and have been cancelling it out with the speakers when set to large. However it would be better to try and cure the mode by tweaking your or the subwoofers position and then try and integrate the speakers.

Plotting a waterfall of the above graphs may also help highlight the areas that could most be improved because ringing is just as detrimental as peaks and troughs in the response.

Anyway if you can post those graphs we can probably help a bit.

Adam :)
 

kit1cat

Active Member
Don't forget that by setting your speakers to large you are losing any bass below your speakers cut off point, if set to small this would be sent to the sub.
 

Medrep1

Active Member
1) Just sub, cal to 75db via processor(volume level 77), sub dial at approx 1/4.

2) Just mains xover at 80hz, set to small, cal to 75db via processor (volume level 87:eek:)

3) Mains and sub together.

Okay, so the mains and sub together is laughable, but this is where trying to turn one down to compenate leads to going round in circles or a significant loss in spl.

Pretty much anywhere I place the sub in the room leads to a big 35hz peak, or to lower it results in a big sub 20-25hz loss.

Thanks for taking a look!
 

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AngelEyes

Distinguished Member
In REW there is a tab that displays all the sweeps you have taken and some tick boxes at the bottom so you can display the 3 you have posted here.

If you can display that it will make it even more obvious where the sub and speakers are interecting.

The main thing you need to fix is that huge peak. Try running the sub only and moving the sub to different positions in the room to reduce the size of that peak. If you can move the sub remember you can rotate it to provide around a foot of movement to the cone, or move the listening position.

See if you can find an acceptable position and post again. Once that is a bit better we can move on to the speaker integration, crossover and phase.

Adam
 

Medrep1

Active Member
Okay, and here's mains and sub calibrated to 75db via processor, set as small as before.

Next one is mains and sub x over at 40hz. With this set up, with some fiddling and positioning, I can get reasonably flat, bar a 10db peak around 35hz again, and a very small dip at 50-60hz.
 

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Medrep1

Active Member
See if you can find an acceptable position and post again. Once that is a bit better we can move on to the speaker integration, crossover and phase.

Will do, cheers Adam!
 

Medrep1

Active Member
There is nothing I can do to get rid of that peak. Ive moved the sub into every corner, turned it different directions, allsorts. The best I have had is this.

I think im going to give up now, as im becoming really fustrated.

So its either x over at 80hz and its all over the shop, or 40hz with tweaking and a get a supposedly on screen graph showing a flatter response, but with distortion and risk of amp strain/speaker damage?

Would I be right in thinking that bigger subs would yeild the same problem but more of it? I havent really considered EQ devices, but was told they can suck the life out of the music/movie?

Sigh:rolleyes:
 

Medrep1

Active Member
:oops:
 

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AngelEyes

Distinguished Member
I think EQ is your only option to cure the big peak but you may be able to improve the crossover area with the speakers set to small with phase adjustments.

I am not familiar with the sub, does it have a variable Phase or just a switch 0-180 ?

Try running sweeps at different phase settings, I usually try every 90 degrees and if it looks better around one setting, try refining the increments around it until I find the best spot on the dial.

If you prefer an easy fix then the AS-EQ1 will probably solve all your problems. It all depends what your own time is worth to you.

Adam :)
 

Medrep1

Active Member
It has a variable phase from 0 to 180, and also a variable crossover. Setting the processor to have no sub crossover and using the subs own has strangely given its own positive/negative results?

If im going to invest in eq then I may plump for a higher end sub with its own built in or like what you have? Its a shame as I really like this sub, and have demo'd it against quite a few big uns'!

Thank you for your time though, at least I now have an idea what direction I need to travel in.

BTW though, ive just put on transformers again with the last set up, (no large settings or low crossovers this time:D) and there is less 'obvious' bass but it does seem cleaner and less flabby. Oh I give up................................:suicide:

Cheers

David
 

pws

Well-known Member
Hi Mate

Ok...here's the deal.

I'll pop over yours with my antimode and you can give it a go.

What will this cost ya?

A cuppa and answer a few questions on REW so we both can learn.

How does this sound?

Cheers

Paul

Swansea
 

kit1cat

Active Member
I think EQ is your best option, if you don't want the expense of the AS-EQ1 perhaps a secondhand sms-1 or the Anti-Mode 8033.

I had a similar peak running from about 25 to 35 hz, using the sms-1 I was able to reduce the peak with no problem, and now have a fairly flat response from 20 to 200 hz.
 

Medrep1

Active Member
What will this cost ya?

A cuppa and answer a few questions on REW so we both can learn.

As long as you dont expect chocolate caramel digstives too:rotfl:

Sounds like a plan, thanks! I'll PM to arrange a date.

Not my experience with the EQ1. Music and movies sound a lot, lot better for it.

This is becoming more of an attraction, although whether it is the most financially justifiable move I dont know.

As my processor will not allow sub via analogue bypass, which is the best option for stereo listening, (and now I dont need it with the 803D's), an EQ device now will be just for the movies. The sunfire was bought intially with my older set up, due to its music performance over the big subs like the Ultra's, but if its just purely for movie use now, then the Ultra is clearly the better option for its low down capabilities.:confused:

PWS to the rescue!!:D
 

Medrep1

Active Member
After countless hours, speakers set to small, x over at 60hz, sub positioned almost midway on the righthand side wall, phase adjusted and sub set at correct distance, here is the best I can acheive in this room, and trust me ive tried!

A fellow forum member is kindly coming to mine this weekend to try the antimode, lets see what that thing can do with that peak, fingers crossed!
 

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