POWERED TOWERS, The test (1 Viewer)

[Bob_A]

Ok, I described the "test" earlier. This is a subjective (non-scientific) test using some of my favorite music program material. No DVD's. NO DVD-Audio. No Super-Audio. Just regular CD's.

Each main channel speaker contains a built-in 15 inch powered woofer (as well as two 1 inch tweeter and four 6.5 inch midrange drivers). The crossover is either 80Hz or 90Hz (I am not really sure which) to the powered woofers. There is no external sub. My room is pretty large, with valuted ceilings, and is completely open to the left and open almost entirely to the rear.

I wanted to see how things would sound if I only used one of the powered bass sections.

So I turned the sub volume down on one speaker (my right speaker), and I kept the sub volume at 1 o'clock on my other speaker (the left speaker). So basically, in this setup, both top sections of each speaker should be crossed over at 80Hz or 90Hz, with everything below this sent to the built-in powered woofer in the left speaker.

I played some of my favorite tunes. The first tune I wanted to start off with was from the Gladiator Soundtrack. This soundtrack is great. If you listen to song 3, about 1 minute into the song, there is an awesome bass note which is played. I played this part of the song with my "test" configuration, and...

WOW! What can I say, I was disappointed. It sounded decent, but normally the response is so smooth and I really feel like the bass is all around me. With only one powered woofer playing, the eveness and coherence of soundstage just did not compare to the dual woofer setup IMHO.

I tried some other material. I tried some U2, "With or Without You". The "test" setup just did not compare to the normal setup. I tried some trance-type music, which have a very punchy sound. Same thing. I tried some rap music, the song "Crossroads" by Bone Thugs. Here I did not notice as big a difference, but still the eveness in sound which I normally get just wasn't there. I tried Sting's "Fields of Gold", as well as Dave Matthews "Crash". I still much preferred the normal presentation.

I also tried these songs with the left speakers woofer volume level turned up a bit (to 3 o'clock), in an attempt to compensate for output differences when turning down the powered woofer in the right speaker. This certainly added more shake, but the coherence of soundstage was lacking compared to the normal setup.

Strangely, on some songs, I noticed that my right speaker was brighter than normal. I really did not like that.

On every single song that I played, the dual powered woofer setup sounded much much smoother to my ears. What can I say, the presence of dual woofers (compared to one) truly does seem to significantly change the sound of the loudspeakers, for the better in my case.

Hopefully, people who have nOrh main speakers on top of nOrh subs, or ACI Jaguars on top of ACI subs, AV Reality speakers on top of AV Reality subs, Infinity on top of Infinity subs, Polk on top of Polk subs, etc. can try out this test and let me know how it goes...because I am not sure how valid my "test" really is.

 

[ColinM]

So you cut the subs in half then? I'd notice a diff, too.

Shut one down and re-cal the other up a bit to compensate.

Then switch to the other side and see if that makes a diff.

- C

 

[John Kotches]

Bob,
Wow, the results were exactly as predicted by myself and a number of others at the other forum. You chopped off response by 3dB for the powered woofer sections, didn't compensate in any way for the drop, and then were underwhelmed by the results
Nice work.
Regards,

 

[Bob_A]

"didn't compensate in any way for the drop"

Isn't that what I was doing when I increased the volume level for the woofer in the left speaker? Do you really think that 3db extra output from only the left speaker would totally change things with my tested music program material? I highly doubt it. The differences I noted were really tremendous. And what about those people who say that two subs placed in different locations will inherently lead to cancellations? If you find this test to be so laughable, then maybe you should try the test under your own conditions with a couple speakers which use a sub as a stand...it might actually open your eyes to some potential benefits of having a powered woofer for each main channel with your favorite music program material. Just my humble opinion though.

 

[Bob_A]

Colin, it was a HUGE difference. I was pretty surprised by how much the sound changed. So, when you say "Shut one down and re-cal the other up a bit to compensate", what exactly do you mean? I did try turning up the woofer volume on the left speaker, and things still were not nearly as good as normal.

 

[ColinM]

Bob -

*Respectfully*

I don't think the 1 o'clock and 3 o'clock settings are 'scientific' enough to warrant any conclusion.

If you were the comedian, this would be the "Tough Crowd". Study the material. Get an SPL meter and calibrate and compare L vs R vs L+R and let us know what happens.

Good Luck!

 

[Bob_A]

Colin, I hear ya. Someday I will pick up an spl meter and "calibrate" a bit more scientifically. But I can pretty much assure you that the overall experience will be superior with my normal setup. The coherence and eveness of the sound are truly amazing. People really have to hear it to believe it. Try it out if you can...you might be pleasantly surprised. Thank you for your sincere response. I really appreciate it.

 

[ColinM]

Yeah, I'm sure it would be best running both, it's designed that way.

But I'm a sub/sat dude. I don't have any experience at all with powered towers, never been in the same room with an operating pair. Someday I'll drop by the local hifi hut and listen to a set or 2, with my own music and my SPL meter with a test cd. That'll shut up the pushy sales guy.

Every time I go into one of those places I get job offers. Maybe I'll accept so I can take home some different systems every month.

- C

 

[John Kotches]

Bob,

Let's look at what you've said in this thread, shall we, first it was this:

I also tried these songs with the left speakers woofer volume level turned up a bit (to 3 o'clock), in an attempt to compensate for output differences when turning down the powered woofer in the right speaker. This certainly added more shake, but the coherence of soundstage was lacking compared to the normal setup.

You have not correctly compensated for the absence of the right channel. If you are not 100% certain that identical information is in both channels below the powered subwoofers crossover frequency, then you've done nothing of any value. You don't even know whether the difference in "1 o'clock" and "3 o'clock" correpsonds to the 3dB that is gone from the other subwoofers contribution.

Here's how you would do an actual test, because even subjective experiments / tests have to have some type of rigor to them.

0) Connect both woofers via a line level signal out of the LFE channel. It's the only way to guarantee identical information brought into the subwoofers, short of mono recordings. If you have mono recordings those would be an acceptable substitute.

1) Borrow or buy a Radio Shack SPL meter, your ears are terrible for picking out absolute SPL levels.

2) Define speakers as small.

3) Calibrate system with both woofers activated.

4) Set volume control to known level.

5) Listen

6) Deactivate one subwoofer by disconnecting the LFE input and turning down the volume control.

7) Recalibrate system.

8) Set volume control to known level.

9) Listen

10) Reverse active and inactive subwoofers.

11) Recalibrate system.

12) Set volume control to known level.

13) Listen

This isn't nearly as much fun, but it is a valid approach. I've normalized to remove volume differences from the equation (ie I've forced you to recalibrate at each change and to use a repeatable volume level on all tests).

Regards,

 

[Scott_Sylke]

As a former user of powered towers and a convert to the more widely used "speakers small with sub"......I'd never go back to powered towers. Just my 2 cents worth.

 

[Bob_A]

Colin, I just want to warn you that not all powered towers are created equally, and many stores will do a poor job of setting up the powered towers. If you listen to some bp2000TL's, let me know and I can give you some pointers.
__________________________________________________ __________
Thank you for the information, John.
What I am trying to create is a scenario as follows: two main channel speakers crossed over at 80Hz or 90Hz, with a powered sub for each channel vs. two main channel speakers crossed over at 80Hz or 90Hz, with two powered subs for one channel.
Doesn't this seem like a reasonable scenario.
I admitted that, with my setup, the validity of such a test would be questionable. I am not really sure exactly how my speakers are run, but I have them wired as follows: a y-connector runs from the "full range low level in" input on the speaker to the "main in" and "pre out" on the receiver. and then there is another (standard) wire which runs from the "mid" jumper on the speaker to the main (L/R) inputs on the receiver.
I can tell you one thing...I am able to control the volume for the powered woofers with both the receiver and with the volume knobs on the back of each speaker.
I never turned off the right woofer, I simply turned the volume down.
I think there is some potential here for a good test...especially for those who use external subs as a stand for their main channel loudspeakers.
I am biased, but I think that there is a good chance that powered woofers for each channel can enhance the experience with music program material.
__________________________________________________ ________
Scott, like I have said in the past, not all powered towers are created equally, and not all powered towers will work well in your room. Maybe you should try out the new ACI Jaguar LE/LFM combo or the new Dynaudio Confidence C7...they might change your mind about having powered woofers for both main channels But anyway, our personal opinion of powered towers is not really the issue here. Thanks.

 

[Bob_A]

To simplify a little, let's say we have two nOrh bookshelf-type speakers, along with two nOrh subs (which can be used as stands for the nOrh loudspeakers). Use your favorite music program material. Set the speakers to "small", and cross them at 80Hz or 90Hz (internal to speaker or external from receiver, I do not know what would be better). First listen to music using a sub for each main channel (meaning one sub as a stand for the left speaker, and the other sub as a stand for the right speaker). Then listen to music using two subs for one channel (meaning both subs are together and are either used underneath the left speaker or underneath the right speaker). Heck, you could even compare them with both of the subwoofers placed next to each other in the same corner. Does this seem plausible?

 

[Ned]

Bob-
The Rat Shack analog meter is only 35 bucks!
Why don't you have this already for calibrating your system properly? You've got a significant investment made in equipment but you skimp on this dinky little item?
This test will be interesting *when* you can calibrate the single subwoofer driver to give the same output as when both are running. Without calibration it's pretty hopeless because nobody is gonna trust the settings. Those units on the subs level knob may as well be chicken-scratchings because they don't coincide with real output.
Some other interesting tests you could perform would be turning the DT subs off completely and using an external sub or pair of subs (see if you can tell which is which).
Winging this without the level meter is kinda flamebait

 

[Glen_L]

Bob said:

What I am trying to create is a scenario as follows: two main channel speakers crossed over at 80Hz or 90Hz, with a powered sub for each channel vs. two main channel speakers crossed over at 80Hz or 90Hz, with two powered subs for one channel.

Doesn't this seem like a reasonable scenario.

No, this isn't a reasonable scenario for a stereo recording. Consider the fact that bass information may not be dispersed equally across both channels. For example, if a bass drum is recorded in the right channel, and you use the left channel to feed your two powered subs (in your example above) you'll get no bass from either of them. Pretty obvious.

That's why step 0 of John K's experiment is necessary.

 

[Steve Zimmerman]

Forgive the length of this post, Bob, but I think you'll find that I'm trying to build on your proposed test. Actually, there are two separate tests.
TEST #1: Can you localize sounds beneath the 80Hz crossover? If you can then running full-range speakers as Large would be preferrable to a sub/sat combination. This test would be performed as follows:
(1) Using full-range powered towers, set speakers to Large and calibrate
(2) Listen and record SPL at 1/3 octave intervals
(3) Set speakers to small, xover at 80Hz, and pipe the mono LFE output into the powered drivers of BOTH speakers and recalibrate
(4) Listen and record SPL at 1/3 octave intervals
For best results, this would be done without knowing which configuration is which, but it's EXTREMELY doubtful you would be able to tell the difference between (2) and (4) because no bass information would be lost--it would simply be mono versus stereo at unlocalizeable frequencies. If you've calibrated correctly, the SPL results in (2) and (4) should be identical, so it's a personal preference issue, i.e. can you tell whether the frequencies below 80 Hz are being played in stereo or not.
TEST #2: What is the affect of moving the bass sources around the room?
(1) Using two bookshelf speakers and two subwoofers, place subwoofers beneath bookshelf speakers and set speakers to small; pipe LFE channel to both subwoofers and calibrate
(2) Listen and record SPL at 1/3 octave intervals
(3) Place both subwoofers beneath left channel bookshelf speaker; recalibrate
(4) Listen and record SPL at 1/3 octave intervals
(5) Place both subwoofers beneath right channel bookshelf speaker; recalibrate
(6) Listen and record SPL at 1/3 octave intervals
(7) Place both subwoofers in a corner; recalibrate
(8) Listen and record SPL at 1/3 octave intervals
Do these tests sound like what you're trying to approximate, Bob? If so, congratulations!! It's a FABULOUS test. In fact, I think everyone who has a 2sat/2sub combination should be required to perform Test #2 as part of their initial setup
Unfortunately, with powered towers you can't really perform Test #2 because you can't separate the subwoofer from the satellites. If you found that optimal placement of the subwoofers was not directly beneath the satellites then you would be faced with the realization that you were stuck with suboptimal bass response.
--Steve

 

[John Kotches]

Steve,
What's wrong with you? You want him to calibrate?
Good god man, that's almost scientific!
For shame, for shame
Regards,

 

[Brian Bunge]

Bob,
Here's your morning mantra: "Calibration is NOT a dirty word!" repeated 10 times each morning as soon as you get up. Despite what your mother told you, you will not go blind!
Brian

 

[Bob_A]

"Why don't you have this already for calibrating your system properly?"

With built-in subs and no external sub, what would you recommend doing as far as calibration? The blending of highs/mids/lows is already a given, and I just set them as "large" with sub to "no", and adjust the bass volume levels to a comfortable level for me. Sorry, I can't run an external sub right now in the family room. I've never objected to adding an external sub to my system to increase the performance.

Ok, I think I understand the issue about losing material from the right speaker below the crossover (since the crossover is not a fixed point and since this information is not routed anywhere). But one thing I am still wondering about is bass information below 90Hz which is sent to the left and right main channels. Is it true that some information below 90Hz is sent to the left channel, and some sent to the right channel? If so, why would we cross over at 90Hz? Because these frequencies are supposedly nondirectional?

Now...what about this scenario: turning down the volume of the right powered woofer by, say, 50% and turning up the volume of the left powered woofer by, say, 50%. Now both powered woofers would be playing, but at different levels. Is this also unreasonable?

As for mono recordings...does anyone know how I can determine if it is a mono recording? Does anyone know about any decent mono recordings? I have some discs from the 1980's like Candlebox...would these be mono recordings?

As laughable as my initial "test" was, I think there is potential for a great test. I think regardless of what I do, a lot of people will question my credibility, even though I have no reason to be deceitful. Hopefully some other people can also try out such a test and let me know how it goes. Thanks.

 

[Drew Bethel]

Bob, congrats on at least starting to think of "testing" the performance of your powered towers. Having said that, how can you offer setup advice to others when you don't even have an SPL meter??? Surely, you can't expect to be taken seriously at an HT forum when you're missing one of the most basic calibration tools!
Anyone in Bob's neighbourhood? Please loan him a meter so that we can get some more objective data.

 

[Bob_A]

The setup advice I offer is with regards to placement and wiring of these bipolar powered tower speakers. That's about it. Yes, I guess it wouldn't hurt to run down to radio shack one day and pick up one of those meters But with my normal setup (testing aside) how should I go about calibrating with a spl meter?