need help with subwoofer setup. crossover related

Hi all

I need some help with the crossover setup for my subwoofer. My neat mf5 speakers goes down to 29hz -3db while my subwoofer crossover is only to 40hz at the lowest. So i have a overlapping of frequency.

My amp and preamp have no subwoofer management and my subwoofer do not have eq. My squbwoofer ia the genesis g928 with dual 12inch woofers.

My room is acoustically treated with bass traps and diffusers. I am very satisfied with my 2 channel and was trying to achieve to the low 20hz ffrequency for pipe organ music and to increase soundstage.

I know many will recommend getting a external dsp like mini dsp or velodyne sms1...but there will be an extra cable to connect these devices to my main system. And therefore will effect the performance of my main system indirectly.

What i desire is just to crossover the subwoofer to 30hz lowpass to blend well with my speakers. Or to crossover my speakers high pass to 40hz to blend well with my subwoofwrs.

So is there any way i can externally or internally crossover my sub to 30hz without affecting the main performance of my current speakers?

Or ia there any way i can crossover my speakers to 40hz without an external device? (Without the involving another set orlf ultra expensive interconnects)

Thank you all for the help and sorry for the long post.

 

You could try using a foam or fabric 'plug' on the rear port which would raise the low freq response and steepen the rolloff a bit to get you some more 'overlap' with your sub.

 

Does your sub have speaker level inputs and outputs? If so, you can use those and the x-over control on your sub.

 

Yes it does have speaker level inputs and outputs..however the subwoofer only crosses over at 40hz at most. Which is overlapping the frequency from the main speakers.

At the moment in connecting the sub from the preout of the densen b200 preamp. Still can use the xover from the sub.

 

You can just start with the sub crossover set at 40hz.

Even if you could......I highly doubt you would need to go lower due to any audible "overlap"

You may actually even have to set it a bit higher.


As you say....... your MF5's are rated 3dB down at 29hz.

For all you know in your room they may be MORE than 3dB down at 29hz......or even 40hz.

You need to find what crossover AND volume sub settings sound best to you in your room.

It's not like Neat used your room when they obtained their speaker frequency response measurements anyway!!!

No need to be so precise with matching the numbers up exactly...........just use your ears.

If you really want to know what your mains ARE doing then try using REW or other measuring tool.

I be willing to wager that they turn out NOT being 3dB down at 29hz.


Cheers

 

But if you hook up the speaker-level ins and outs, the signal sent to your speakers will be x-overed, so there won't be any overlap.

 

Oops sorry my subwoofer do not have speaker out

ive measured my speakers with a dspeaker antimode dual core before i add basstraps and treatments. The neats do go super low!

 

Hi,

Well going by the pic you posted they are WAY off -3dB at 29hZ!!!

DEFINITELY no need to cross over the sub any lower than 40hz at least.......... so problem solved.

Cheers.

 

If you mean the speakers, then you have this backwards. Plugging the port would soften the rolloff considerably. It would begin to rolloff at a higher frequency, but then at a more gentle slope and extend deeper. Left unplugged, the port will help the speaker extend the bass a little bit deeper with out rolling off yet, and then roll off much faster. Basically: unplugged= more bass up higher, then falls off precipitously to nothing. Plugged= less bass up higher, but much lower extension with gentler rolloff.

 

I think I worded my post poorly - agree with that the plug would mean 'less bass up higher'. I thought that was what the OP wanted to do so he could use the sub's xover.

I had read on some B&W forums that the plug also 'steepened' the rolloff not 'gentle'. I use B&W bookshelves and used the plugs to get better integration with my own sub, so was going on the info passed on.

 

I always tune with some overlab as the speaker output a 29Hz will likely have dropped off substantially, more than the claimed -3db one should think.

 

Im iliterate when it comes to auduo graphs...by seeing that
frequency chart, what is the approximate rolloff? That frequency chart probaby sucks as its before any treatments is done.
However i dont reckon the treatment will lower the extension, maybe just smoothen things up.

By seeing that bass response i poated. What is thebestimated frequency that you would crossover at?

 

Without having a lot more info on your room, system, sub output etc it's hard to make even an approximate guess, but, I should think somewhere in the neighborhood of 40 to 56Hz.
To get in the ballpark, start by playing a fairly bass heavy song at a fairly high level but not louder than you would normally listen. Then start at the lowest crossover point possible and slowly increase till you start hearing a bit of overlap, it will begin to sound slightly bloated and boomy, then go a whisker back ( lower ). You need to do the listening from your normal sitting position so if there is no sub remote have a friend rotate the control and try to match volume levels as you go. The more times you repeat this and the bigger diversity of music the better.

 

Is the red line before adjustments and the black line after adjustment?

Assuming the answer is yes, it does look to me like the black line is fairly smooth response down to about 28hz. There is about 6db missing at 30hz then it pops back up.
I would bet that the large valley (-10db) at 25hz is probably phase related. You will need a really big corner trap to deal with it. Bigger than you can find online, think home made pink fluffy stuff.
It looks like the sub's phase is not variable so the only way to try adjusting the phase is to move the sub and remeasure. There is another valley at 45hz that is close enough to the sub's 40hz crossover to be worth trying to adjust the phase through placement. If you are lucky, moving the phase may smooth both the 25hz and the 45hz.

As for reading the chart, each horizontal line is 6db. I would eyeball the linear reference at -18db with variances being +/- the -18db line.

As suggested, REW is more helpful, especially if you can get graphs of the response with and without sub. The simplest graph that I have found most helpful with dialing in a sub is frequency with phase. Waterfalls can be helpful but I find them more helpful when placing treatements.

Out of curiousity, what created the chart?

 

The measurement is actually without subwoofers and there is 4 big bass traps around the room already.

The chart is created from a borrowed antimode dual core used before treatments

My system is mac mini - gustard u12 - nad m51 - densen b200 - densen b330 - neat mf5. Room is 4x6 meters.

This is old pic but speaker positikn and bass trap remains the same.

 

Hi,

I know you said it's an old pic but where exactly is/are the sub (s) ?

That's not it/them in the middle under the screen is it?

If it's not.......then where were you planning to (or already have) put it/them?

Cheers

 

What are the two lines on the chart then?
The antimode is not in the system anymore?

I guess without any measuring and charting ability, you are going to have to make do with what you have and cross them over where it lets you, then set volume and placement by ear.

 

The sub is exactly where the amp is now. While the amp is further back to the screen. After the sub crawl, there is the smoothest response.

That 2 lines is before and after the antimode. Now the antinode is not being used and treatments are added. I tried to cross at 40hz...yet still some overlap unless i set the volume at 0.5/10 lol.

So is there no way i can crossover the sub externally without the changing anything about the main channel?

The fmod looks interesting bjt i cant seem to find one that crosses at 30hZ..just 50hz.

 

An overlap is actually desirable as the lowest frequencies will get reinforcement you prolly didn't know they needed to sound even more natural. If I were you I'd set the sub's volume halfways and start at 80 hz. If you don't like what you hear keep going down toward the minimum 40 hz setting. Bet you'll stop way before it.

You don't adjust a sub by maths, but by ear.