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Hi All,

Thanks to the many intro posts on this forum, I've just started to learn about REW and trying to make the best of my current equipment and room. Added several GIK treatments a while back which improved bass, and now learning about REW. Bpape from the Acoustics forum has helped greatly with both processes and suggested some good improvements.

Now looking at my first REW attempt below, big dips at around 100, 135, and 155. I've experimented with L/R speaker (tower) placement bringing out from the front wall as much as possible and reduced these dips some.

The room is about 20 x 12 x 8, speakers on long wall, listening position opposite. Sub is on front wall to right of the right speaker, but not in the corner.

I'd appreciate any suggestions or comments.

Thank you!
 

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Wow, your REW graph look just like mine did a year ago! I had home made 12 inch ported subs tuned to 48 hertz, anything below 45 just rolled off into never never land. I moved them everywhere and tried a variety of things with them. In the end the only answer was to move up to a more serious sub. I bought two Rhythmik 15 inch sealed subs and I was glad I was able to do so.
For the high end I also experianced drastic 'dips' in the graph. I have alot of speakers, so I simply replaced my front mains with a variety of speakers and found that the location of the room was my only enemy. So once I got my new subs built I placed my front mains onto a used 12 channel eq and that helped alot. Once thing I did not do is place bass traps / sound absorbing materials / etc (as I don't have them and they are typically a little pricey). But maybe if you have some of those items you can help with the response curve.
I must say that since location seemed to have the biggest effect, I also noticed that placing the speakers closer to the center of the room lowered those dips, but they had to be so close that it was no good.
Now that I have substantial subs (I built two 15 inchers) I no longer seem to care about the dips in the higher ranges, they are there, but they don't stand out as much anymore to the ear.
You did not mention what type of sub you have? My speaker mains are 25 dollar garage specials that are about 27 years old. 12 inch cones, ported, from Technics and stand about 3 feet tall, I ended up suspending them from the ceiling in order to get better sound (less dippage in the air).
 

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You can go to this Shack link and scroll to the bottom, there is a picture of my home theater there. Don't be fooled, it is a completly unfinished basement, I just went to a material store and spent about 50 bucks on some cheap black material and hung it on the walls and ceiling.
"Rythmik 15 sealed sub build - two of them"
(Sorry, I don't know how to make it an active link)
 

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Discussion Starter #6
You can go to this Shack link and scroll to the bottom, there is a picture of my home theater there. Don't be fooled, it is a completly unfinished basement, I just went to a material store and spent about 50 bucks on some cheap black material and hung it on the walls and ceiling.
"Rythmik 15 sealed sub build - two of them"
(Sorry, I don't know how to make it an active link)
Dan, very impressive construction effort, and I'm sure the detailed pictures have helped folks who want to build their own. I imagine you have some substantial bass. You have a great looking home theater on a very small budget. I am also considering a Rythmik upgrade, perhaps the D15 sealed.

If I understand correctly, you used some equalization. I didn't see that you published REW graphs before/after?
 

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Well, to start (and perhaps finish) the graph looks like there is no sub at all. Might try corner loading it, if that's an option - a 10" sub typically needs all the help it can get...

Regards,
Wayne
Thanks, Wayne.

Yes, under 50 it just tails off, there is not much oomph there. Boosting the sub level just brings everything up. I will try moving it more to the corner see if this will boost a bit. Have been considering an upgrade to Rythmik.
 

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Guilty as charged, I never posted any REW charts. I accidentally deleted the files and moving my computer to the basement (again) and setting it all up is a bit unweildly. I will try to make it a priority in the next few weeks.
I tried to bump up the bass with my old subs and it just brought up everything as well. It took me 6 months to get the money together to buy the Rhythmiks. I think that just one would do the trick for most situations though. Especially if you got the ported version (they give a bump at the tuned frequency). I only bought two as I don't like when I can 'localize' the bass. It is distracting to me when watching movies. But I'm no purist or anything :)
 

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It's difficult to evaluate a sub when it's shown on a plot with the mains added.

It may indeed have weak bottom end extension as the present plot shows, but it may also have a large peak between 40-70Hz that could be reduced to reveal a better extension. Hard to tell until we see a sub only plot.

brucek
 

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It's difficult to evaluate a sub when it's shown on a plot with the mains added.

It may indeed have weak bottom end extension as the present plot shows, but it may also have a large peak between 40-70Hz that could be reduced to reveal a better extension. Hard to tell until we see a sub only plot.

brucek
Bruce, here is the sub only plot. I increased the sub channel level in the receiver to bring the overall levels up, but kept the sub volume control the same. This gained some. How would I "flatten" the 30 - 70 Hz hump?

Thanks,
Mark
 

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Yeah, I agree with Wayne. I guess there's a little to be gained by reducing the high peak, but the sub just doesn't have a lot of extension.

brucek
 

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My take on the Rhythmik is that it is best suited for someone who places value on accuracy as much as volume (and price, of course!! This does weigh in here!!). Rhythmik may not be as loud as other subs in DB, but the accuracy is what I wanted. Part of my concern was that I have Transducers under my couch and I wanted the subs to play into that, not just provide a 'thumpy' bass sound. I have never owned nice subs (read: expensive), but I have owned many from the used market and in general I found the sealed to be more accurate. Now anyone reading this can say 'well the such and such brand is very accurate, even for a ported' but I am talking strictly about garage sale or Craigs list specials.
Anyway, my point is that I think Ikka (of Shack fame) said it best in his review of the Rhythmik: they had a 'dry' sound. To me that means that they follow the sound wave very accurately, to the point that you could hear every sine wave. I can attest to that, and that is what I wanted, they do play into the transducers well.
Actually I originally wanted 4-12 inch, but sadly, Rythmik stopped making those (plans, anyway). So I went with 2-15 inch and I am very happy with them. I paid roughly 600 or so per sub and spent probly 5 days total building the two of them.
My room is about 21 * 16 * 9, and depending on how many decibals your mains put out and whether or not you care about localization I would think that one 15 inch might work for you. Please keep in mind that I am not a veteran as many contributors are on this site, just my opinion from the measurements.
Don't forget that for a fee, you can have the box built for you as mentioned on the Rhythmik site.
 
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