Upgrade 2.2 system to handle 50 Hz crossover

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ebefspz

Audiophyte
Hello! New member, first post!

I am new to the high end audio world and have been enjoying (?) the steep learning curve. After much frustration and persistence I finally figured out subwoofer and speaker placement to minimize mode activation in my room. My issue now is that to get the bass right (without equalization...a nest I am not ready to burrow into just yet) I need to cross my subwoofer over down at 50Hz. The biggest speakers I own (which I am currently running as fronts) are Polk RTiA3 bookshelves which have a -3db rating of 50Hz.

I was just going to buy the RTiA5 floorstanding speakers in the same Polk line, but they only have a -3db rating of 40Hz. I am sure they would help some (and my receiver does allow me to biamp the front speakers) but my gut tells me they still might not be enough. Much of that line of thinking comes from articles on bass management that I have read here at Audioholics and elsewhere, stating that a speaker should be crossed over ideally at half an octave or at the very least at least 10Hz above its -3db point.

To meet the half octave criterion I would need a speaker with a -3db point at or near 30Hz, and the only one I have come across near the RTiA5 price point is the SVS Prime Tower. I like the 3.5 way crossover with the SVS Primes but they are not biampable. I realize that biamping is a debatable topic but there does seem to be a sense that it can help with low end performance when the woofers are connected directly to their own amp. The RTiA5s, on the other hand, do have dual binding posts.

Other speakers I like are the R55Ti tower from RBH and the Aperion Verus Grand Tower, but both of their -3db points are listed at 45Hz. The Aperion is above the price range I am looking at right now, but I thought I would throw it into the discussion in case I am focusing too much on the -3db point. The Aperion is a speaker I was thinking of upgrading to as a step along my path to potentially getting some Revel F208's.

Here are the details of my audio situation:

Room size: 12.67 feet wide, 12.92 feet long, 8.46 feet high (i.e. small room)
Listening distance: 8 to 8.5 feet (right now exact measurement is about 100 inches)
Front speaker separation: 76 inches from center of front baffle to center of front baffle
Front speaker distances from walls (both are the same): 38.75 inches from center of front baffle to wall behind speaker, 38 inches from center of front baffle to side wall
Front speakers: Polk RTiA3 bookshelf speakers (not biamped)
Receiver: Onkyo TX-NR1009
Subwoofers: dual Polk DSW440Wi

I know that I am asking too much of my bookshelf speakers right now, but I just don't know where to go next. I need a speaker that plays down well past 50Hz so that it has enough headroom at that crossover, but I am not sure how a large speaker would do in my room or how a large number of drivers would be able to integrate over my available listening distance.

As you can probably tell from the length of this post, I have been thinking about this for a while. I am hoping members could give me advice on what is and isn't important in my decisionmaking and any speaker suggestions that might work for me that I haven't listed already. Thank you so much!
 
j_garcia

j_garcia

Audioholic Jedi
You don't need to biamp those speakers anyway :) I actually liked the RTiA3 when I reviewed it a few years back.

Room correction just on the subs might also help, with something like a mini-dsp. Sounds like you have enough "tweaker" knowledge based on what you've said that you'd be able to handle incorporating it easily. How about room treatments to aid the sub situation as well. You also don't need a full half octave below because the sub's slope is usually 12dB or more while the speaker side is 6dB to allow a smoother blend. Your case might be pushing it though, so I understand why you're asking.

My honest recommendation: new subs.

Welcome to AH!
 
lovinthehd

lovinthehd

Audioholic Jedi
Why do you think the 50hz crossover will stay the same with another set of speakers? What sub(s) are you using? Square rooms can be challenging, too.

ps NM, just saw what you have for "subs"....get better subs first.

pps Also agree passive bi-amping is a waste of time/wire/money.
 
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shadyJ

Speaker of the House
Staff member
Bi-amping in your setup is mostly a waste of time and money. None of the woofers of the speakers you listed will become awesome with their own bass driver channel of amplification. They would have to be some pretty impressive woofers for that to happen (they are not). Don't pay attention to -3 dB or -10 dB specs. They mean nothing without the context of extensive measurements. If you want serious bass performance, co-locate the subwoofers next to the speakers and raise the crossover point. Also, get better subs. Another thing, you say this is all a stepping stone to get the Revel F208? Why not just get the F208s? You are just throwing away time and money on incremental upgrades until then. Even the F208s will benefit from a good pair of subs, by the way.
 
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ebefspz

Audiophyte
The 50Hz crossover is all about the subwoofers not exciting my room modes. They are placed halfway down the length of the room which eliminates that dimension's first mode (i.e. around 44Hz). They are also placed one quarter of the room width away from the side walls which cancels out (as far as my ears can tell) the first mode for the room width as well (i.e. which is also around 44Hz...one of the beautiful things about having a nearly-square room). I did extensive trial and error (and frustration) without ever getting any improvement in the bass. I finally came across A Guide To Subwoofers (Part II) posted by Big Daddy on Blu-Ray forum which helped me understand room modes and it wasn't until I applied that knowledge to my subwoofer placement that I made any progress.

So, I can place the subwoofers such that they don't excite the first room modes for both length and width but given where they are I cannot raise them off the floor in order to cancel the first room mode for the height of my room (i.e. about 66Hz). When I set the crossover to 50Hz, I don't hear any boom in the bass but when I raise the crossover up to 60Hz I start to hear it again. So I am left with setting the crossover at 50Hz so that the rolloff of the subs do not stimulate my room height's first mode.

The front speakers are also positioned to reduce the length and width room modes, and with either tower speakers or bookshelf speakers on stands the bass drivers would be off the floor a good amount which will help with the height room modes.

Being new to the audiophile game I am trying to make the best with what I have. Given the situation I ended up finding myself in, though, I am not sure that my RTiA3s are up to the task of performing well down to 50Hz. I would like to find a nice pair of towers that will play well down to 50Hz so that I can test my setup for how bass that low sounds from my front speaker positions and how well multiple drivers integrate over my available listening distance.

The F208s are huge and I don't know if they would be too much for my room. They have a -3db point of 31Hz which is what caught my eye. I plan to upgrade everything in my system over time, but right now I am looking for a well performing and reasonable speaker to adequately test my setup.
 
ski2xblack

ski2xblack

Audioholic Field Marshall
That modal response will extend up pretty high in that small room.

I second the motion for measurements, gotta see what's really going on. REW is free, the mics are cheap, do it.

This small room may be a case where passive traps could help smooth things out up to the room's transition frequency.
 
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ebefspz

Audiophyte
Without measurements. I was just trying to get rid of the bass 'boom' I kept hearing, and this setup was the first to do it. I do have Gik Acoustics Tri Traps floor to ceiling in all four corners with bass traps on stands to handle first reflections. I thought it might be worth getting a speaker I know is not being pushed as hard at 50Hz as the RTiA3 before wading into all of that. Never done measurements before and from the outside looking in it just looks intimidating.
 
lovinthehd

lovinthehd

Audioholic Jedi
Without measurements. I was just trying to get rid of the bass 'boom' I kept hearing, and this setup was the first to do it. I do have Gik Acoustics Tri Traps floor to ceiling in all four corners with bass traps on stands to handle first reflections. I thought it might be worth getting a speaker I know is not being pushed as hard at 50Hz as the RTiA3 before wading into all of that. Never done measurements before and from the outside looking in it just looks intimidating.
To an extent I'd suspect your subs for exaggerated response in that range as well. You need to invest in a measurement mic (Dayton UMM-6 or miniDSP Umik-1 are easy) with REW for software.
 
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shadyJ

Speaker of the House
Staff member
Without measurements. I was just trying to get rid of the bass 'boom' I kept hearing, and this setup was the first to do it. I do have Gik Acoustics Tri Traps floor to ceiling in all four corners with bass traps on stands to handle first reflections. I thought it might be worth getting a speaker I know is not being pushed as hard at 50Hz as the RTiA3 before wading into all of that. Never done measurements before and from the outside looking in it just looks intimidating.
You really need to do some measurements. Right now what you are doing is just guestimating, and what you think you are hearing is heavily influenced by what you expect to hear. I would add that you can follow step-by-step tutorials that make measurements pretty simple. Anyway, do some measurements before you do anything else, it may take a little time but it could save you a lot of money. I bet you would have found you didn't need bass traps for starters.
 
tyhjaarpa

tyhjaarpa

Audioholic Field Marshall
Also did you make a sub crawl to find the locations for the subs or did you just place the subs where you think they sound good?
 
E

ebefspz

Audiophyte
I have a laptop with REW and a UMIK-1 on hand, and have done some more reading on how to use REW. One of my hesitations is that I don't know what to start with. I need to measure for speaker placement, listening position and subwoofer placement but from what I have read changing any one of these variables can significantly influence the other. Is there some kind of process flowchart for finding the optimum for all three variables starting from scratch?
 
lovinthehd

lovinthehd

Audioholic Jedi
I have a laptop with REW and a UMIK-1 on hand, and have done some more reading on how to use REW. One of my hesitations is that I don't know what to start with. I need to measure for speaker placement, listening position and subwoofer placement but from what I have read changing any one of these variables can significantly influence the other. Is there some kind of process flowchart for finding the optimum for all three variables starting from scratch?
Have you tried the various home theater setup articles to start with? Like here http://www.audioholics.com/home-theater-setup

Maybe try this guide
 
ski2xblack

ski2xblack

Audioholic Field Marshall
You can augment the "bass crawl" using the mic instead of your ears. Hopefully that will help you identify the best possible sub locations more precisely (far better than what you did previously, although you may find that they measure best right where your first method had them). After that, you'll probably only need to take measurements from the primary listening position (take them from several locations in and around the sweet spot). I'm not sure what your Onkyo has to offer as far as manual tweakability, or if it can import eq files that REW is able to generate, but you can, at the very least, verify appropriate hpf and lpf settings and check phase for the subs (you should achieve flat measured response at the mlp when the phase is adjusted correctly, and will notice narrow drop outs when it's not).

REW can be quite intimidating at first, but stick with it.
 
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