JBL 705P Studio Monitor Review

[CumSum]

That’s interesting. I tried few subs so far and only one of them - Apart A165 - was fast enough for the music that I’m listening. I have yet to try Rel subs. I heard good about them...

Have you performed measurements and room correction? If not then you'll never know how good a sub actually is.

 

[Sal1950]

Have you performed measurements and room correction? If not then you'll never know how good a sub actually is.

What criteria to you use to determine a subs speed?

 

[Everett T]

That’s interesting. I tried few subs so far and only one of them - Apart A165 - was fast enough for the music that I’m listening. I have yet to try Rel subs. I heard good about them...

I'm not sure you have demoed enough subs and sure of the impact of them in your room. The only chance I'd go with an 8" sub would be in a TL alignment and for music only.

 

[richard12511]

I thought the thx spec was in relation to sealed box mains to integrate the fixed roll off in THX AVRs? I'll have to dig but IIRC there was a correlation.

It might be related to that too. I would really appreciate any thing you can dig up, though. I read it years ago, but haven't been able to find it in 5 years or so, so I'm going purely off memory at this point.

If my memory serves. There was one listener who was able to locate a 160Hz tone, but he was the only one, and no one else succeeded below 210Hz. I believe this was with 1 sub. I'm sure 4 bass sources would be much more difficult to locate.

 

[CumSum]

What criteria to you use to determine a subs speed?

From objective measurements probably the impulse response, distortion and frequency response/bandwidth.

But those things go out the window once you introduce the sub into a room. So appropriate integration to the mains and room is required. Placement, time alignment and room correction to get the sub sounding its best in that room. A properly integrated cheap sub can very well sound better than an improperly setup expensive sub.

 

[Sal1950]

From objective measurements probably the impulse response, distortion and frequency response/bandwidth.

Excellent response. I actually messed up and meant to ask the question of @cany89 as he had made some statements with no supporting evidence.
But in any case, folks will discuss a sub's speed or sounding fast, ect; but haven't read much about it's relationship to any particular objective measurement. The market spin often makes claims of Sealed Box subs having the edge over Ported in that particular area of performance, but I've read others saying different.
I believe good impulse response should have a close relationship but I don't have the tech background to support it.

 

[CumSum]

But in any case, folks will discuss a sub's speed or sounding fast, ect; but haven't read much about it's relationship to any particular objective measurement. The market spin often makes claims of Sealed Box subs having the edge over Ported in that particular area of performance, but I've read others saying different.

Most people don't integrate subs properly, so you get people who hate subs entirely, and then you get people who think subs that are super small, have no output and no depth, sound fast. When in reality, they are just not making much bass at all. Look at REL cultists as an example.

Personally I haven't heard a high end ported sub so I can't speak to their sound quality. All my sealed subs have sounded pretty identical to one another. This is with proper integration, volume matching and an identical target curve when using room correction. Sealed subs are definitely easier to design and get sounding right then a ported sub. With somewhat affordable 18" sealed sub options on the market, I personally don't see much reason to go ported.

 

[Sal1950]

With somewhat affordable 18" sealed sub options on the market, I personally don't see much reason to go ported.

IF the ported design can sound equally good, they offer higher efficiency with all else being equal.
That's a big IF, one of which I have no knowledge.

 

[CumSum]

IF the ported design can sound equally good, they offer higher efficiency with all else being equal.
That's a big IF, one of which I have no knowledge.

I know, but with these 18" or greater sealed subs you can have your cake and eat it to. You have equal to better mid bass output (above 40Hz), so you are only losing out to ported subs below 35Hz. Room gain will help you increase your ULF output. And you can also hit much lower frequencies with sealed subs, unless your ported sub happens to be tuned to 10Hz. 120dB at 20Hz is doable with sealed subs. Easily hit 130dB above 30Hz.

 

[More Dynamics Please]

I thought the thx spec was in relation to sealed box mains to integrate the fixed roll off in THX AVRs? I'll have to dig but IIRC there was a correlation.

Explained as part of a 2006 story from the Home Theater & Audio Review Vault:

The THX crossover consists of an 80 Hz, 4th order Linkwitz/Riley filter alignment, and it was not chosen lightly or without serious consideration. As the crossover frequency increases, it becomes harder to blend the subwoofer with a satellite, and the subwoofer becomes more difficult to audibly "hide". At the same time, as the crossover frequency increases, distortion from the satellite decreases, the total dynamic range increases, and loading the room for the flattest response becomes much easier. The logic of the 80 Hz crossover point is that it's high enough to ease demands on the speakers and amplifier, but low enough to make the whole setup work without a tremendous headache. The 4th order (24dB/octave roll-off, 6dB/octave/pole) Linkwitz/Riley alignment not only offers a steep slope, but one that immediately transitions to that slope, maximizing the benefits of that slope near the crossover point. The high-pass side minimizes excursion and power requirements, while the low-pass minimizes more localizable content at higher frequencies.

To correctly achieve this, THX satellite speakers are sealed systems with an 80 Hz –3 dB low frequency cutoff (preferably with a Qtc of 0.71). The electronic high-pass filter applied to them is an 80 Hz, 2nd order (12dB/octave) Butterworth alignment. The speaker and the filter sum to a 4th order Linkwitz/Riley roll-off which matches the electronic filter applied to the subwoofer, and an excellent crossover is achieved.

https://hometheaterhifi.com/volume_13_1/feature-article-thx-1-2006-part-3.html

 

[Everett T]

Explained as part of a 2006 story from the Home Theater & Audio Review Vault:

The THX crossover consists of an 80 Hz, 4th order Linkwitz/Riley filter alignment, and it was not chosen lightly or without serious consideration. As the crossover frequency increases, it becomes harder to blend the subwoofer with a satellite, and the subwoofer becomes more difficult to audibly "hide". At the same time, as the crossover frequency increases, distortion from the satellite decreases, the total dynamic range increases, and loading the room for the flattest response becomes much easier. The logic of the 80 Hz crossover point is that it's high enough to ease demands on the speakers and amplifier, but low enough to make the whole setup work without a tremendous headache. The 4th order (24dB/octave roll-off, 6dB/octave/pole) Linkwitz/Riley alignment not only offers a steep slope, but one that immediately transitions to that slope, maximizing the benefits of that slope near the crossover point. The high-pass side minimizes excursion and power requirements, while the low-pass minimizes more localizable content at higher frequencies.

To correctly achieve this, THX satellite speakers are sealed systems with an 80 Hz –3 dB low frequency cutoff (preferably with a Qtc of 0.71). The electronic high-pass filter applied to them is an 80 Hz, 2nd order (12dB/octave) Butterworth alignment. The speaker and the filter sum to a 4th order Linkwitz/Riley roll-off which matches the electronic filter applied to the subwoofer, and an excellent crossover is achieved.

https://hometheaterhifi.com/volume_13_1/feature-article-thx-1-2006-part-3.html

Thanks for the info! There was some additional info that applied to the crossover slopes, I just can't find it.

 

[Sal1950]

I know, but with these 18" or greater sealed subs you can have your cake and eat it to. You have equal to better mid bass output (above 40Hz), so you are only losing out to ported subs below 35Hz. Room gain will help you increase your ULF output. And you can also hit much lower frequencies with sealed subs, unless your ported sub happens to be tuned to 10Hz. 120dB at 20Hz is doable with sealed subs. Easily hit 130dB above 30Hz.

I've got a pair of SVS SB2000 (12") sealed subs in a relatively small listening space and a pair of HSU 10" ported subs on the sideline. One day when I get ambitious I might even try integrating all 4 into the system. But then the current pair of SVS's sound incredible as it is.

 

[beefkabob]

I have a large, single, ported sub front and center, to go with my 708p. The SVS 16-PB. I think it sounds fantastic. It is annoyingly huge, but it fills in the base for movies, rock, and hip-hop. The integrated crossovers on the sub and speakers are certainly useful, but the system truly shines with a MiniDSP handling the crossover and adding in Dirac. Eyes open, I perceived directional bass with a 120hz crossover and the sub off to one side. I don't perceive that at 80hz. The sub is now centered, but I haven't played with it at different crossover frequencies. There might be a subtle impact on imagery with some music. As it is, the PB16 is capable of far more volume than the 708p can provide, let alone the 705p. If I could do it all over, I'd grab a couple sealed, smaller-footprint Rhythmik subs and use them as speaker stands. Maybe a couple E15HP2. It might be possible to go smaller and still get the full effect.

 

[beefkabob]

One other thing: SVS engineers stated that there's really no reason to go sealed other than for space considerations. You just get a lot more bass out of a ported sub, and measurements of the PB16, at least, have proven that they can go seriously loud with miniscule distortion.

 

[Sal1950]

One other thing: SVS engineers stated that there's really no reason to go sealed other than for space considerations. You just get a lot more bass out of a ported sub, and measurements of the PB16, at least, have proven that they can go seriously loud with miniscule distortion.

Yes I've read that, not sure I agree with it but I don't have any solid evidence to support or dispute it. LOL

 

[jhaider]

We need to drop those notions of small subs being “fast” and larger subs “slow”. It is a matter of proper integration...

That is mostly true. I have however heard some subs that simply could not be integrated with mains. These are fortunately not common today - drivers with very long overhung voice coils and simple motors lacking inductance control. EQ is not the answer, because the inductance - swings greatly with excursion. In one case, a multi-way subwoofer was the answer, with a better sub playing 40-120 Hz or something like that and the bad sub just pumping bottom octave air.

Also, generally a sub is more likely to integrate well when it has smooth and extended response beyond its nominally passband IME. One can go overboard there - I had to put an electronic 4th order lowpass at 500Hz to get Dirac Live Bass Control sympatico with our Aurasound driver based subs, because they can play so much higher than the subwoofer passband.

One other thing: SVS engineers stated that there's really no reason to go sealed other than for space considerations.

Space considerations are a Big Deal. Especially since one should be using multiples. The other advantages of closed boxes are no ugly port resonances to deal with, and more output below cutoff. All of our living room subs are closed boxes, for those reasons. I never considered vented cabinets.

 

[Sal1950]

Many years back when the sub market was only a small fraction of the size today I had a hell of a time integrating a sub into my Klipsch La Scala mains. The KLS system was so efficient (104db) with very low distortion inside it's normal bandwidth that finding a sub that could "keep up" was difficult.
Around 1990 Dr Hsu just started HSU Research and one of his first products was a 7' tall cylindrical sub with a long throw 12" driver in a ported design. Long story short I ended up with 2 of these monster subs and a pair of NAD amps run in bridged mono configuration that could supply some ridiculous amount of power on short term peaks. These ended up one hell of a sub system that could hang with the KLS's up to some incredible SPL's.
The neighbors hated me, back in my wilder days. LOL

 

[beefkabob]

Space considerations are a Big Deal. Especially since one should be using multiples. The other advantages of closed boxes are no ugly port resonances to deal with, and more output below cutoff. All of our living room subs are closed boxes, for those reasons. I never considered vented cabinets.

Ported or not, it's the overall effect that matters. It's like choosing a speaker by the type of tweeter: a ribbon can be done well or poorly, the same as any other technology. But yes, size is a big deal in many situations.

 

[jhaider]

Ported or not, it's the overall effect that matters. It's like choosing a speaker by the type of tweeter: a ribbon can be done well or poorly, the same as any other technology.

Not a great analogy. A ribbon or whatever tweeter has a lot of variables. And besides, we know a ring radiator with genius phase plug mounted to a brilliant waveguide is the answer there.

A vented bass cabinet, however, has a fixed set of 4 qualities compared to a closed box:
1) higher efficiency in a region above port tuning
2) much faster loss of extension below tuning
3) vent resonances
4) generally, larger cabinet for a given driver

IMO, the vented cabinet’s advantage (#1) is negated by use of multiple subs. The drawbacks remain. That said, if one wants the highest possible output in a given passband and is less concerned with infrasonics (which are generally overrated anyway) the vented cabinet is a great option.

 

[Sal1950]

IMO, the vented cabinet’s advantage (#1) is negated by use of multiple subs. The drawbacks remain. That said, if one wants the highest possible output in a given passband and is less concerned with infrasonics (which are generally overrated anyway) the vented cabinet is a great option.

But which one "sounds" faster ???