Suggested sub placement procedure

[Zerock]

Hi

I was wondering what others are doing as a sequence to arrange their subs, running REW as an aid.

I have two home made sealed subwoofers with 10" drivers. Both subs are 4 ohm ran by one channel of an older Yamaha natural sound amp which rating is 115WPC.
Impedence on the amp is for 8 ohm so I am running both subs wired in series. I did a Db comparison with them in series, and output of the two are close.
I assume the drivers are underpowered, but I've been using this arrangement for years without any apparent problems that I'm aware of.
The only EQ I have for the two subs is (a) Bass control on my Onkyo (B) The 60 and 150hz slider EQ controls on the Yamaha driver amp. There is no crossover for the drivers: just straight to the amp.

My HT is approx 20x22x8.

Here is what I've recently done:
1. Installed/setup/read help for REW.
2. Disconnect my main L&R speakers
3. Connect only one sub
4. Moved my listening position 38% off the rear wall (Just over 8')
5. Set bass control on my Onkyo to the half way click, 60hz slider on my Yamaha to zero and 150 control about half way down. "Loudness" control about half.
5. Run REW using that one sub while placing it into various places around the room.

After a couple hours of testing, found two places that gave the best result.

I like to run two subs on opposite sides of the room for a more balanced effect so I connected my 2nd sub.

3 huge nulls appeared. I had a few hours more fun with trial and error placement testing with REW.

I removed my mains L&R speakers from off the front wall, placed them in an equalateral arc to the listening position, about a foot off the floor so the tweeters are about ear height.

I reconnected the mains L&R again, so now I'm testing them along with two subs.

Sure enough I'm getting more response problems and have spent an hour or so trying the subs in different areas before shutting down for the night..

Am I creating more work for myself than neccessary?
Is this the proper way?
I'm really new to this and wouldn't know the difference.

The wife says it all sounds fine and doesn't understand all the maticulous testing.
I do think my room suffers the "One note bass" effect and want it perform the best possible.

Thanks
-Steve

[Wayne A. Pflughaupt]

Hi Steve,

I guess you're starting to see why the "standard protocol" is a single subwoofer, with low pass filtering for the sub and high pass filtering for the mains (i.e., a crossover between them). This allows the sub (or more than one of them) to put in the optimal location for best performance, and you minimize interference from other sources of bass in the room (be it another sub seperately located and/or full-range speakers). That's not to say that other options aren't feasible, but seperated subs, mains running full range, etc. are usually more difficult to properly implement and require much more tweaking - as you know.

Regards,
Wayne

[Zerock]

Thank you so much! Looks like I'll be building some bandpass passive filters.
I assume the low cut-off should be around 200hz, and the mains should pick it up at that figure.

[brucek]

I assume the low cut-off should be around 200hz, and the mains should pick it up at that figure.

Why not 80Hz? That would would be considered typical..... and the THX standard.

Does your ONKYO not have bass management?

brucek

[Zerock]

Thank you for the suggestion, I'll go with 80Hz.

Does your ONKYO not have bass management?

It is model TX-SV727, DOM is approx 1995. A good, strong older amplifier. But no bass management other than the "bass" knob.

[Wayne A. Pflughaupt]

Ouch! Well, what you could do is connect a cheap electronic crossover like the Behringer CX2310 to the sub (in front of the amp). REW could tell you where your mains are rolling out and you could set the crossover around there. Not optimal, but better than what you're dealing with now.

Regards,
Wayne

[Zerock]

One of my "other" hobbies is electronics, and as a die-hard DIY went to the web to look at some passive crossover schematics.

I modeled a couple with Tina Pro http://www.tina.com/ but all that I modeled rolled WAY past 80HZ, some even into the 2Khz range. I toyed with various values with little luck getting even a semi-sharp rolloff. I'm not sure if it's problems with the programs calculations, or if passive filters are just that way.

Given that, I did decide to go with a powered front end LP crossover which should be fairly easy to build. If it all works out I'd put it in a nice case to finish it off.

If the design doesn't test satisfactory I'll probably go with the Behringer

Thanks again for the help.

[brucek]

Have you considered an inexpensive receiver?

[Wayne A. Pflughaupt]

Given that, I did decide to go with a powered front end LP crossover which should be fairly easy to build.

"Powered" as in "active," I hope...

Regards,
Wayne