REW question about measurements for sub implementation

[subfire91]

Hello everyone,

To the gurus here i have a small guidance regarding incorporating 2 x subs with my speakers.

I have 2 REL subs which are connected to the PREOUT on my amp one one the left and one on the right channels.

Regarding measuring the frequency response, is it better to measure both subs together and both speakers together and then trying to figure the crossover/gain etc or each speaker and sub separately ?

Thank you

 

[levimax]

Hello everyone,

To the gurus here i have a small guidance regarding incorporating 2 x subs with my speakers.

I have 2 REL subs which are connected to the PREOUT on my amp one one the left and one on the right channels.

Regarding measuring the frequency response, is it better to measure both subs together and both speakers together and then trying to figure the crossover/gain etc or each speaker and sub separately ?

Thank you

See link from a member and resident guru @Keith_W for an e-book on how to take measurements and then use them. https://drive.google.com/drive/folders/1VRndkoExTNFBOSqPTiiBmU67HlLUeiza?usp=drive_link This is a great place to start.

 

[janbth]

Regarding measuring the frequency response, is it better to measure both subs together and both speakers together and then trying to figure the crossover/gain etc or each speaker and sub separately ?

Ideally, you should connect the subs in mono to play the summed signal. Measure and tweak as necessary to make them play well together. Then integrate this combination with the L+R signal from your mains.

You will find discussions about «stereo subs» here on ASR, but that is an advanced topic IMO. Learn how to do mono first.

 

[subfire91]

Ideally, you should connect the subs in mono to play the summed signal. Measure and tweak as necessary to make them play well together. Then integrate this combination with the L+R signal from your mains.

You will find discussions about «stereo subs» here on ASR, but that is an advanced topic IMO. Learn how to do mono first.

Actually is the only way i connect them. My amp is Musical Fidelity M6si so no LFE ports

 

[thcdru2k]

Actually is the only way i connect them. My amp is Musical Fidelity M6si so no LFE ports

How are you setting crossover for your subwoofer and speaker ? I believe your integrated amp does not have bass management so you are sending a full range signal to both your speakers and subs? Not a deal breaker, basically you would just have a low pass on your sub whatever the REL allows and run your speakers full range. Placement of the sub would be important because you have no way to delay the sub or main.

 

[subfire91]

How are you setting crossover for your subwoofer and speaker ? I believe your integrated amp does not have bass management so you are sending a full range signal to both your speakers and subs?

Yeap no option to mess with crossover of the mains.

I can mess with crossovers and gain on the subs only. I have 2 REL HT/1205 MKII

 

[thcdru2k]

Yeap no option to mess with crossover of the mains.

I can mess with crossovers and gain on the subs only. I have 2 REL HT/1205 MKII

Yeah not a deal breaker. I think it can still sound excellent you just have to get comfortable with sub crawl since cannot control delay.

 

[subfire91]

Yeah not a deal breaker. I think it can still sound excellent you just have to get comfortable with sub crawl since cannot control delay.

yeah im trying to attempt to get a good result for what i can get. i will try to avoid sub crawling if i can get a good result.

What i couldnt find though by reading through the various sources and youtube is the methodology of it:
Should i treat the mains as one measurement and both subs as another and try to make them work as best as possible?

Should i try measuring the Left Speaker separately and blend with the Left sub and do the same for the other R side ?

Or should i treat both the Speakers as one measurement since i cannot mess with anything regarding them and implement each sub one by one ?

Another question i have that i may need a input from you guys is that when setting the listening volume to 75dB before measuring, is it for each unit separately or speakers combined should be at 75dB and subs combined at 75db ?

i could use any guidelines you can provide.

 

[Keith_W]

I am currently writing a subwoofer integration guide for Acourate. Although it is for Acourate, the general principles apply no matter what DSP software you use. You can view the draft here.

This is a very broad overview of the steps required:

Step 1: Place your subwoofer. DON'T avoid the sub crawl, you want to fix as many problems as possible BEFORE you begin the DSP process. You only have to do the sub crawl once! Don't be lazy! You spent money on this thing, you want to get the best out of it, don't you?
Step 2: Decide on your LPF/HPF config. See the draft eBook for considerations on how to decide.
Step 3: Time and phase alignment. See the draft eBook for the method. Instead of using Acourate's tool, use REW's alignment tool.
Step 4: Do a MMM or multi-point averaged measurement and EQ that to flat.

Re: 75dB measurement volume. Don't bother, just measure at your normal listening volume. Loudspeakers and subs are nonlinear devices, if you measure at a different volume you may get a different frequency response. You only need a 75dB measurement if you are doing formal testing.

 

[subfire91]

Hey @Keith_W,

Thank you for your time in answering.

Regarding Step 1:

I will most probably avoid this despite understanding your point of view. The issue i dont have the cable infrastructure to do this and also is the living room so i do take into account the aesthetics of it also.

Step 2:

Yeap i need to take the measurements correctly first.

Step 3:

I cannot do time alignment. No option for it on my equipement. I will avoid also byuing something a mini-dsp at least for now. Phase alignment. Only 0 and 180 degrees setting on the subs. no more customization on that part.

Regarding the listening volume a have read your answer but i apologize... i did not get the meaning of it. Which one of the scenarios i posted above your suggestion leans towards to?

 

[Keith_W]

You do not have to be too precise when adjusting volume for this type of measurement. Simply play REW's sweep. If it sounds too loud to you, it IS too loud. If it sounds too soft, it IS too soft. It only needs to be "ballpark" volume. If you are worried about poor signal-noise ratio, choose a longer sweep (about 1M). You are not doing formal testing here, all you are doing is trying to integrate your sub to your main speakers. Without DSP, your only controls are subwoofer loudness and polarity inversion. This is nowhere near enough control. For now, I suggest a quick sweep, adjust the volume until it blends as well as it can, then flip the polarity to see if it's better or worse.

Remember that subs co-located with the speaker will excite the same room modes. So whatever problems you had before will become twice as bad.

 

[levimax]

Remember that subs co-located with the speaker will excite the same room modes. So whatever problems you had before will become twice as bad.

I used to believe this but a recent experience has changed my perspective. Playing around with stacked colocated subs and mains I found the height of the sub can make a huge difference in the way it affects room modes and other room issues. How it works out in general I can't say but in my case the height difference between sub and mains woofer resulted in a much smoother response.

 

[john61ct]

Would that mean that we should consider raising subs up off the floor?

 

[NTK]

The vertical position of a sub affects how it couples to the vertical (reflections between the floor and ceiling) room modes.

 

[john61ct]

so, yes?

 

[NTK]

so, yes?

Yes.

 

[levimax]

Would that mean that we should consider raising subs up off the floor?

You need to measure in your room to see if it makes any difference but if you have some flexibility I would try it and see. To me the most important thing is getting the tweeters at ear level at the LP, next I want the woofer within 1/4th wavelength of the sub which creates a point source wave front and possibly allows the use of linear phase crossovers. In my case I had to turn my subs on their sides and raise the subs off the floor and put the mains on top in order to satisfy these 2 requirements. Much to my pleasant surprize when I took my measurements to apply DSP room correction this combination had a much smoother response than either the subs or mains by themselves and smoother to start than any previous arrangement I had tried including distributed subs. Sometimes you get lucky. I did do some more measurements to confirm and found height can make a big difference in LF FR in some cases.

 

[john61ct]

> height can make a big difference in LF FR in some cases

good to know!

I want the woofer within 1/4th wavelength of the sub

At the LPF right?

...

I am planning on a front wall mostly filled with stacked IKEA KALLAX shelving, so all enclosures can get slotted into those background cubes at any height for storage and transport.

I will ofc need to experiment whether it is necessary (and how) to bring the speakers forward when optimising SQ.

Drawer slides would be preferred over having to deploy tripods.

 

[Keith_W]

Would that mean that we should consider raising subs up off the floor?

Look at it this way: moving subs up/down has the same effect on vertical modes as moving the sub left/right and front/back on horizontal modes. It's just another axis in x, y, z. There is nothing special about the vertical axis. If a dip in the response is caused by a front-to-back mode, elevating the sub will not do very much.

 

[levimax]

> height can make a big difference in LF FR in some cases

good to know!

At the LPF right?

...

I am planning on a front wall mostly filled with stacked IKEA KALLAX shelving, so all enclosures can get slotted into those background cubes at any height for storage and transport.

I will ofc need to experiment whether it is necessary (and how) to bring the speakers forward when optimising SQ.

Drawer slides would be preferred over having to deploy tripods.

Yes at LPF. Note, this is not a universally accepted requirement for subs to mains integration. I come at it from a DIY speaker building perspective where the colocated subs and mains become a "full range speaker". The more common ASR wisdom is splitting the subs and mains up results in better frequency response which is more important than time domain behavior which is sacrificed when you split the subs and mains . I try my best to get both FR and time domain accuracy.