My gentle giant is silent (Heeman might shed a tear...)

[PaulyT]

Replaced. Maybe John will post a pic of the two amps side-by-side. I liked the sound of the two PSAs - as heeman said, once we got the gain adjusted by ear to what seemed a reasonable level. They were very clean and musical. Granted, I don't think they produced quite the level of output that the PB13u did, during movies and "real" LFE. Without knowing the specs (and too damn lazy to look them both up ) I'd guess these particular PSAs don't go down quite as low as a PB13 with two open ports.

 

[Zing]

PSA's website offers product comparison charts but what they don't offer is a comparison between XV15 and the PB13Ultra. And maybe that's because their "PSA Value" would indicate that it may take two or three XV15's to equal one PB13Ultra.

*EDIT*
Added third chart for the big boys.

 

[Deleted member 133]

Zing,

I'm looking at those two tables and some things about them make no sense to me.

First compare the 20Hz-31Hz figures for the dual 15" XS30 and the single 15" XV15: they are identical at 116.6. I find that odd - given the differences between the two. To me that's the "meat" of the range (and below) that I measure subs by - not at higher frequencies. So why pay $350 more for the same performance in that critical range?

Secondly look at the quoted numbers for the $1599 SB13-Ultra versus the $799 PB2000 in that same frequency range: the latter bests the former by 4.1 dB!? Again that raises red flags in my mind.

Then again maybe the numbers are "true" - which only tells me that the performance versus price proposal is all out of whack for some of these subs - including PSA's.

Jeff

 

[Zing]

Keep in mind one thing, Jeff (for both of your concerns): ported vs. sealed. I don't find it odd at all that a single 15" driver in a ported box can equal or best the output of dual 15" drivers in a smaller, sealed box.

To me that's the "meat" of the range (and below) that I measure subs by - not at higher frequencies. So why pay $350 more for the same performance in that critical range?

I'm with you on this one. The lower range is what's most important to me. But to your question about why pay more, just take a look at the output differences in the other ranges and I think you'll find where the value lies. Those are the "musical" ranges and the ones where the most amount of content is. The lower you go, the less often you'll find something there.

 

[CMonster]

Remember, sealed subs count on room gain to boost low-end performance and that doesn't show up in the measurements. Output from ported subs drops like a rock below the port tune (around 18 Hz for PSA subs).

 

[Zing]

Remember, sealed subs count on room gain to boost low-end performance...

Don't all subs count on room gain?

 

[CMonster]

So I've been thinking about switching to sealed subs and Batman's praise of Zing's XS30s this past weekend has increased that desire. Out of the blue today, I get a PM on AVSForum from someone who saw my HT pics and wondering how the dual XV15s do in the front of the room because he's thinking of doing the same thing. We trade some PMs and it turns out he lives about 10 minutes away from me and he's not opposed to buying used. He's coming over Saturday morning for a demo and some advice on building an HT. Since all of my real subwoofers have been designed/built by Tom V., I'm thinking about heading a different direction just for the sake of trying something new. Here's the leading candidate at the moment:

 

[CMonster]

Remember, sealed subs count on room gain to boost low-end performance...

Don't all subs count on room gain?

As I understand it, and I could totally be on crack here, the output from sealed subs isn't dropping off as quickly down low so they're going to benefit more from room gain.

 

[Zing]

You're not on crack (to my knowledge anyway). A sealed design does indeed have a more gradual roll-off but its output is almost always significantly less than a ported design until the lowest of frequencies. Whether or not that means it benefits more from room gain than a ported does is beyond me.

And if you're considering a JTR sub just to be different, I can't stop you. But I'd be remiss in my duties as a friend if I didn't say "At that kind of money, you're a fool for not considering a PSA Triax!"

 

[Botch]

I think that we all agreed that the SVS had a much more accurate sound. It also seemed to pressurize the room much better than the stacked XV-15's.

Please tell me you guys didn't leave the XV's stacked during the listening tests.... :|

 

[Zing]

I think that we all agreed that the SVS had a much more accurate sound. It also seemed to pressurize the room much better than the stacked XV-15's.

Please tell me you guys didn't leave the XV's stacked during the listening tests.... :|

Why wouldn't they? That's called "co-located" and arguably one of the better and easier-to-set-up configurations.

 

[PaulyT]

Yeah, we wanted it to be kinda symmetric with the PB13, and didn't have the cables (or inclination ) to move them all around the room.

 

[CMonster]

And if you're considering a JTR sub just to be different, I can't stop you. But I'd be remiss in my duties as a friend if I didn't say "At that kind of money, you're a fool for not considering a PSA Triax!"

The best location for a sub in my room is the back corner on the riser next to the rear seats. The Triax is a bit wide to fit there.

 

[CMonster]

I think that we all agreed that the SVS had a much more accurate sound. It also seemed to pressurize the room much better than the stacked XV-15's.

Please tell me you guys didn't leave the XV's stacked during the listening tests.... :|

Why wouldn't they? That's called "co-located" and arguably one of the better and easier-to-set-up configurations.

By arranging the PSAs like that, they act as one bigger sub and that was needed in order for them to have a shot at hanging with the SVS. As Pauly said we didn't have the cabling necessary to put them in different locations which could smooth out the frequency response but wouldn't offer as much headroom.

 

[Botch]

Well, I'm gonna say that any sub is designed to interact with the floor. and up in the air like that, one's not coupling, at all, with the room like it was designed to. Not having the cabling? Bah! Chris should've taken Chuck shopping to go buy some! :teasing-neener:

 

[Flint]

Below 50Hz you could place a sub on the floor or up to 2.8 feet above the floor and the "coupling" with the floor will be identical. However, above 50Hz if you et more than 2.8 feet above the floor, stuff might happen - like bats flying out of your ass.

 

[Deleted member 133]

Keep in mind one thing, Jeff (for both of your concerns): ported vs. sealed. I don't find it odd at all that a single 15" driver in a ported box can equal or best the output of dual 15" drivers in a smaller, sealed box.

To me that's the "meat" of the range (and below) that I measure subs by - not at higher frequencies. So why pay $350 more for the same performance in that critical range?

I'm with you on this one. The lower range is what's most important to me. But to your question about why pay more, just take a look at the output differences in the other ranges and I think you'll find where the value lies. Those are the "musical" ranges and the ones where the most amount of content is. The lower you go, the less often you'll find something there.

Ok. I see your point(s). Thanks.

If I were using smaller speakers crossed-over at something like 80 Hz, then I would be concerned about the "other" ranges for sure.

Jeff

 

[Deleted member 133]

Below 50Hz you could place a sub on the floor or up to 2.8 feet above the floor and the "coupling" with the floor will be identical. However, above 50Hz if you et more than 2.8 feet above the floor, stuff might happen - like bats flying out of your ass.

First time I've ever heard anyone accuse Bats of being up someone's ass.

You gonna take that from him Bats?

 

[Flint]

And while I am at it... no discussion about bass can be had on any forum I am member of unless I get to mention the equal loudness curve. Remember, if the acoustic SPL at 15 - 30Hz is not more than 75dB, then you can't hear it.

 

[Flint]

So... when it comes to low end roll-off... once the effective output drops to about 10dB less than the average, that is below the subs effective operating range.

A sealed sub will start rolling off sooner but at a more gradual rate.

A vented sub will extend deeper before rolling off but then roll off at double the rage (per octave).

When comparing two subs, one sealed and one vented, what you need to look at is the -10dB point which is 13dB lower than the RMS high output level in the primary operating range.

So, if the sealed sub crossed the vented sub at a frequency where the level of both is more than 13dB lower than the RMS peak level, then it is pointless to discuss the output below that frequency below that point.