Subwoofer TECHNICAL SPEC questions

[Tom Steele]

Hi,

As you know, I am searching for a sub. I have come across the following resources in my search...

http://www.soundandvisionmag.com/assets/download/818200316533.pdf

and

http://www.soundandvisionmag.com/assets/download/seismicsubslab.pdf

Something I don't understand on these pages are the Output SPL measurements. It appears to me that this would be the ultimate measure of a sub. Assuming equal, and low, Total Harmonic Distortion then the sub making the most dB should be best - theoretically.

I realize there is more to it than that. However, just looking at the specs on the seismic page, the PSB 6i would be a clear winner, closely followed by the Outlaw audio.

The PSB 6i has 225 watts continuous power (RMS I assume) 325 watts dynamic power (what is that?) and 600 watts peak. I am familiar with RMS and PEAK.

The Outlaw has 325 watts RMS, 1,300 watts Peak. I believe CLEAN wattage usually creates the best SOUND.

However, on paper - according to the review, the PSB is making more SOUND.

Looking at the specs, which if these speakers is better?

I'm going crazy!!!

 

[JoeE SP9]

One of the most important things in choosing a sub is the -3db point. A true sub will have a -3db point below 25hz. It will also be able to play a 30hz tone at +102db. There are not a lot of devices out there that fit these requirments. "Subs" with 8" woofers and the like need not apply. Choosing a sub based on amplifier power does not take into account the efficiency of the sub. A ported system is more efficient than acoustic suspension and a horn is more efficient than both. The amps included in most subs are purpose built or have a tailored response. So when looking for a sub I would be concerned about its -3db point and max SPL not about amp wattage. As always, you must listen for yourself. Buying a sub unheard, on specs alone makes no sense.

 

[annunaki]

Be careful when choosing on "max SPL". If you have a frequency response hump at say 50 hz and it is 4 db louder than the rest of the bass bandwidth the subwoofer is capable of it will not sound very good. It will be very boomy. Look for loud flat frequency response here would be a good example: 24hz-80hz @ 112 db +-3 db.

Pay absolutely NO attention to PEAK power ratings. There is no standard to measure peak power. You do not know if that measurement was taken over a second or a nanosecond. You also have no idea of the input voltage on the amplifier, impedance used, distortion at the time of measurement, ect. Amlifier power is definitely not the most important factor here.

I would say that how linear a subwoofer is over its range, and at what SPL, would be the most important factor. Basically in both articles that is what the bandwidth uniformity measurments are taking into account. Look for the widest bandwidth, the most uniformity, with the highest SPL. You may have to make some trade offs. If you are mostly into music the widest bandwidth (that plays the deepest) with the most uniformity would be very important. For movies the widest bandwidth with the highest SPL may work better. The uniformity is not quite as important for movies.

 

[Tom Steele]

Thanks!

One of the most important things in choosing a sub is the -3db point. A true sub will have a -3db point below 25hz. It will also be able to play a 30hz tone at +102db. There are not a lot of devices out there that fit these requirments. "Subs" with 8" woofers and the like need not apply. Choosing a sub based on amplifier power does not take into account the efficiency of the sub. A ported system is more efficient than acoustic suspension and a horn is more efficient than both. The amps included in most subs are purpose built or have a tailored response. So when looking for a sub I would be concerned about its -3db point and max SPL not about amp wattage. As always, you must listen for yourself. Buying a sub unheard, on specs alone makes no sense.

Outstanding replies!

One thing that worries me about ignoring RMS power is that I was treated to a half-hour sales pitch on a Marin Logan Grotto sub at my local Tweeter store. The guy told me how great it was, efficient, crisp, blah blah blah...

He forgot "terribly underpowered." I am always a little afraid of subs without power, that are using "tricks" to get their ratings.

As for buying a sub unheard, it is VERY HARD to audition subs. I have written my story on that elsewhere, but the condensed version included a JBL at Best Buy that when you clicked on it's button to listen to it, you heard ONLY THE SUB. I asked a salesperson to pipe in some full-range speakers with it and they couldn't!!!

So, while you are correct, I don't know what else to do. I'm trying to combine specs with user opinions though, and make a good guess.

I'm narrowed down to a Velodyne CHT-15, Outlaw LFM-1 and PSB Subsonic 6i and longshot on a locally available B&W ASW700. I need to re-audition that one, but it is ~$1,000.00 too.

Thanks,

-Tom Steele

 

[Unregistered]

Be careful when choosing on "max SPL". If you have a frequency response hump at say 50 hz and it is 4 db louder than the rest of the bass bandwidth the subwoofer is capable of it will not sound very good. It will be very boomy. Look for loud flat frequency response here would be a good example: 24hz-80hz @ 112 db +-3 db.

Pay absolutely NO attention to PEAK power ratings. There is no standard to measure peak power. You do not know if that measurement was taken over a second or a nanosecond. You also have no idea of the input voltage on the amplifier, impedance used, distortion at the time of measurement, ect. Amlifier power is definitely not the most important factor here.

I would say that how linear a subwoofer is over its range, and at what SPL, would be the most important factor. Basically in both articles that is what the bandwidth uniformity measurments are taking into account. Look for the widest bandwidth, the most uniformity, with the highest SPL. You may have to make some trade offs. If you are mostly into music the widest bandwidth (that plays the deepest) with the most uniformity would be very important. For movies the widest bandwidth with the highest SPL may work better. The uniformity is not quite as important for movies.

Annunaki,

Thanks for the informative reply.

A couple of things. I'm going to go out of order. I agree with you totally about peak power. CLEAN RMS is the ticket in my humble opinion. You guys are helping me understand where SPL's fit into the scheme of things.

Moving back to the top of your reply though, my budget is limited to "under a thousand bucks" and I'd like to get off on the lowest side possible without sacrificing too much quality.

In a perfect world, price would simply determine which was best and you could choose your upper limit and be done. But reality is that I can probably find some $600 subs that I liked better than some $1,000 subs. I definitely don't want to end up with a $1,000 sub that I don't like!

With that in mind, I don't see ANY of the subs listed on either of those two sheets that appear to remain within 3dB's of flat.

The PSB 6i is close from 32hz up, but none of them can handle flat response down to 25 or 20. The PSB holds up pretty well though, compared to the others. The CHT-15 is poor below 32hz but is loud and fairly flat through the rest of the range, except for a spike at 60hz.

I wish the Yamaha's were reliable. I loved that sub. I wonder if there is an SPL test on the YST-800 to compare to others...

Hmm.

Thanks again for the very helpful replies.

-Tom Steele

 

[annunaki]

Tom,

What I used for specs was simply an example. Only truly excellent systems will have response figures in that neigborhood. Usually the ones over $1000.

One must remember that most subwoofer systems are ported. Ported systems roll off response below their tuning frequency at 24db/oct. A ported system, unless tuned extremely low, will not play linear much below 30 hz (as most are tuned between 28hz-35hz) in most cases. The PSB appears to have excellent characteristics. Also remember that room interaction/placement will play a big role in real, deep, low end response, below 30 hz. Those tests are done in a very large room. Actual in room response (2000 cu.ft. or less) would deeper I am sure (depending upon placement).Try to avoid systems with spikes in response, unless you will be crossing the sub over below that frequency. Even so, a sharp slope of at least 18db/oct. should be used.

If a sub is at +-3.5db or +-3.2db do not be concerned. That is still very good.

The B&W ASW 675, Velodyne CHT-15, M&K V76, Energy S12.3, or Velodyne DPS-12 all have good response #'s as well. The PSB, however, still has an edge in linearity.

 

[Tom Steele]

Annunaki,

Thanks for the response. I guess the scary thing is that ultimately it is hard to get the specs to tell you everything.

I guess this is where the subjective vs objective (or spec only) war comes into play.

I'd personally prefer specs only, but I believe it would take more specs than we get to truly measure a speaker.

I say this based on my listening to the B&W ASW 675. Lot's of bass, but I heard "boom" in there that I didn't like. I don't know you you measure "boom" in specs.

I guess there is no true substitute for auditioning. But unfortunately that is not always possible.

My theory right now is:

1. Specs;
2. Reputation;
3. Experience;
4. Auditioning if you can;
5. Subjective opinions.

I have a Velodyne SPL-1200 II based on the above.

1. Specs are outstanding;
2. Reputation is outstanding;
3. I have experience with the CHT-12 and like it plus my brother has a CHT-15 that we both like;
4. Can't audition;
5. Subjective opinions are based on reviews and comments on the web, and generally they all indicate that this sub is powerful, but also tight, crisp and musical.

Thanks!

-Tom Steele

 

[Tom Steele]

Typo Fix

That should read:

"I have a Velodyne SPL-1200 II ORDERED..."

-Tom Steele

 

[mtrycrafts]

I guess there is no true substitute for auditioning.

-Tom Steele

That has its own problems, human bias. You cannot control it. You have no idea when it is influencing your perception in a way that is not real. The only reliable way is a bias controlled condition, DBT.
You have a pretty good plan of action you included. Don't abandon it.

In discussing your links with the author,

"Bandwidth Uniformity describes how uniform the linear dynamic capability of a subwoofer is. Do not mistake it for a frequency response curve but by and large they often tend to track. But its also common to have a product that appears to have deep bass but can't produce same at any reasonable output level. "

94+ uniformity is a good

 

[Tom Steele]

That has its own problems, human bias. You cannot control it. You have no idea when it is influencing your perception in a way that is not real. The only reliable way is a bias controlled condition, DBT.
You have a pretty good plan of action you included. Don't abandon it.

In discussing your links with the author,

"Bandwidth Uniformity describes how uniform the linear dynamic capability of a subwoofer is. Do not mistake it for a frequency response curve but by and large they often tend to track. But its also common to have a product that appears to have deep bass but can't produce same at any reasonable output level. "

94+ uniformity is a good

Another thing I notice is an emphasis on 25hz and 20hz. Elsewhere though, I've read that very few DVD's have any material in this spectrum. That would explain why a CHT-15 sounds very good to me, yet doesn't score well in the lower frequencies.

It appears that a flat curve from 32hz to 80hz is the most important thing.

-Tom Steele

 

[mtrycrafts]

Another thing I notice is an emphasis on 25hz and 20hz. Elsewhere though, I've read that very few DVD's have any material in this spectrum. That would explain why a CHT-15 sounds very good to me, yet doesn't score well in the lower frequencies.

It appears that a flat curve from 32hz to 80hz is the most important thing.

-Tom Steele

Here is a link to CDs containing low frequencies:

http://www.lymanfamily.org/lyman/randy/audio/low_hz.html

As you will see, some go as low as 5 Hz

And, SVS Sub offers these waterfall of low freq content in movies, just click on the movies:

http://www.svsubwoofers.com/faq.htm#moviedemos

 

[av_phile]

Is the sub more for movies or for music?

For mostly music, I'd personally get a sealed-sub enclosure type. Not the most efficient, but they often provide the deepest, flattest, most controlled and most musical low frequencies. Admittedly, they can be picky and difficult to place in a room, depending on your room accoustics and dimensions. They also require more amp power for the same SPL that a ported one can deliver. (a by-product of inefficiency.) But well integrated with your main spakers, sealed subs can be the most musically satisfying. Anything else would be good for movies. But that's just me.

 

[3db]

Maybe I'm misreading the results out of this test

But I think, PSB had the best sub in that review because it was nearly flat across its operating range and played the loudest across its entire range . It wasn't as spikey as the other subs. Most people get caught up on SPL at a gven frequency but if its response is up and down across its curves, it must be a real bear to integrate with the mains

 

[annunaki]

I think that the SPL-1200 II will be a very good sub for you Tom. I have seen a few reveiws on them and they have been quite favorable.

3db I agree with you there.

Av_phile, I also agree that sealed enclosures tend to work better for music. They have a smoother roll off (12db/oct.) as opposed to ported enclosures (24db/oct.) and tend to play deeper. The overall output difference (using the same subwoofer) between ported and sealed enclosures is usually about 3db. Which as most of us know is not a huge difference. However, from the amplifier's standpoint it is a fairly large efficency difference.