JBL 705P Studio Monitor Review

[QMuse]

The port is tapered/flared, and one would need to add end effect corrections (usually about 1/3 the diameter if the port was circular). Estimating the port resonance of a flared square port isn't going to be easy, but 750Hz isn't unreasonable. The Q must be quite high to get the effect seen, and that would tend to point towards the port.

A simple circular diameter pipe of say 5cm diameter would be about 19cm long to have a resonance at 750Hz. Tapering it could cause all sorts of interesting changes.

Sure, tapering could do it, but in this little space.. Have you seen this post and pihotos shown there?

EDIT: @TimVG found better photo!

 

[Francis Vaughan]

Yeah. I would be happy to bet on that port having a nice resonance at the offending frequency.

 

[QMuse]

Yeah. I would be happy to bet on that port having a nice resonance at the offending frequency.

Well, as it is shaped like a french horn it must play on some freq!

 

[Wombat]

Big cabs. and large CSA/short ports/vents is how it was meant to be.

It was never intended to be a plumbing exercise in shoe-boxes.

 

[ctrl]

Yeah. I would be happy to bet on that port having a nice resonance at the offending frequency.

From the picture of @TimVG I have to agree with you.

Have a look at the Spinorama of the JBL 708P/LSR708i. Since a bass reflex tube with the same design is used there, there should be a similar problem - only at slightly lower frequencies (if a slightly longer tube is used there).

From the diagram, the resonance around 600Hz would be appropriate, corresponding to an effective tube length of 0.29m.
Let's see what Amir's measurements show for the 708P.

 

[thewas]

One cn be sure this design was subjected to lots of unsighted listening tests using the swapping robot, comparing with competing options for the design. It almost certainly doesn't make the sort of difference the nasty looking graphs suggest.

I don't think Harman does such thorough unsighted listening tests with every of their hundreds loudspeaker shuffler for such minor issues, the shuffler is more used for their generalised and important research like the one from Toole.

 

[jhaider]

3. If only JBL and a lot of other companies knew those physics, and how to design ports so that this wouldn't be a conversation.

The physics are what they are. What you are really saying is they could have:
1) Built a larger cabinet
2) Used a smaller diameter port
3) Tuned the speaker higher
4) Used passive radiators

1 and 3 presumptively conflicted with their design brief.
2 would substantially lower SPL due to port compression.
4 would have added a lot of cost and reduced durability in a speaker intended for, among other applications, being tossed around in control vans.

From listening, it is clear to me that JBL engineered the port to be as inoffensive as possible. If using with a subwoofer, one can stuff the mouth with denim insulation and the "problem" (for the eyes) goes away.

That's a "refreshing" logic, because in the past recordings were mixed on crappy loudspeakers, in the present you should use loudspeakers with obvious faults as a tool for professional recordings too... yeah!

Most monitors currently sold are considerably more flawed than these speakers. Maybe a handful from the likes of Genelec or Neumann have smoother and flatter response.

... and will you share your knowledge with us "ignorants"?

Ports have out of band resonances. These resonances are more pronounced in big, long ports in small cabinets. There you go

By closing the bass reflex port the standing wave inside the cabinet does not disappear, only the part of the wave that is transmitted through the bass reflex port disappears.

You mean the part that interacts with the driver output, leading to the null? That is correct. Close the port, lose the null.

PS: the 708P comparison is not apples to apples. The 708 port tuning is not much lower, but the cabinet is significantly larger. I’m sure there’s a cutaway of 705 on the internet. If you find one you will see the port takes up a substantial portion of the cabinet. So the physics dictate the effect of port resonance will be much lower in 708 than 705.

 

[bobbooo]

I don't think Harman does such thorough unsighted listening tests with every of their hundreds loudspeaker shuffler for such minor issues, the shuffler is more used for their generalised and important research like the one from Toole.

If this video for their Infinity brand is anything to go by, it looks like they do in fact do such blind listening tests for each model using the shuffler:

 

[thewas]

If this video for their Infinity brand is anything to go by, it looks like they do in fact do such blind listening tests for each model using the shuffler:

That video is more than 10 years old when Harman used to still make more Hifi loudspeakers under the brand infinity and is also marketing in the end. Now Harman belongs to Samsung and JBL Pro has current almost 3 digit number of speakers series(!) for monitoring, PA, cinema and installation, https://jblpro.com/en/product_families , each one should guess the chances for himself that everything gets blind tested in that shuffler...
By the way, just looking at the JBL Pro website I just discovered a seemingly new monitor series with VU instruments on their front baffle https://jblpro.com/zh/product_families/nano-k-series

 

[617]

Is it cynical of me to think that the point of the listener preference scores is that it eliminates or diminishes the need for careful listening tests?

 

[QMuse]

Is it cynical of me to think that the point of the listener preference scores is that it eliminates or diminishes the need for careful listening tests?

I wouldn't say it's cycnical, but IMO preference score is more about speakers who you don't want to shortlist for listening before buying than about choosing which speaker to buy based on the score.

 

[amadeuswus]

By the way, just looking at the JBL Pro website I just discovered a seemingly new monitor series with VU instruments on their front baffle https://jblpro.com/zh/product_families/nano-k-series

VU meters on a speaker! Where do I buy?? Seriously though, is the nano K series available in the US?

 

[QMuse]

By the way, just looking at the JBL Pro website I just discovered a seemingly new monitor series with VU instruments on their front baffle https://jblpro.com/zh/product_families/nano-k-series

LOL

Those are looking so nice they should become part of scoring system to punish every speaker that doesn't have them!

 

[TimVG]

Does the K stand for K-pop?

 

[Kyle / MrHeeHo]

That video is more than 10 years old when Harman used to still make more Hifi loudspeakers under the brand infinity and is also marketing in the end. Now Harman belongs to Samsung and JBL Pro has current almost 3 digit number of speakers series(!) for monitoring, PA, cinema and installation, https://jblpro.com/en/product_families , each one should guess the chances for himself that everything gets blind tested in that shuffler...
By the way, just looking at the JBL Pro website I just discovered a seemingly new monitor series with VU instruments on their front baffle https://jblpro.com/zh/product_families/nano-k-series

Those are apparently speakers targeting the DJ crowd in Asia
https://pro.harman.com/news/harman-...ntroller-for-the-china-apac-and-india-markets

 

[Dj7675]

Got 3 B-Stock 705P’s yesterday and set them up in my HT. Powered them up and started to do Audyssey setup. I heard a little crackling in the right speaker and kept getting worse. Turned it off, back on, checked connections, and started hissing/crackling very loud, so shut it off. Completed Audyssey with just L/R speakers and have been listening to music and some movies. Couple of random observations:
The good
-I have the 708P’s in our living room and really like them. I knew the 705p was going to obviously be much smaller, but it is really small.
-Crossed at 80hz with two Rythmilk L12 subs, it is pretty amazing how good they sound in such a compact package.
-At my seating distance of around 12 feet or so they appear to get plenty loud for my use. Generally listen around -10db.
The not so good
Of the 3, 1 was in very good condition in like new condition, with white bag etc. The other 2 were both very dusty/dirty with no white bag, or enclosed in any bag. One had what I thought was a crack but looks like may just be a scratch. Then of course there was the one that will need to be replaced. I really like them a lot but am concerned the longer term durability. I’m thinking of sending all 3 back and getting 3 passive speakers instead despite really liking the two working ones!

 

[Doodski]

Got 3 B-Stock 705P’s yesterday and set them up in my HT. Powered them up and started to do Audyssey setup. I heard a little crackling in the right speaker and kept getting worse. Turned it off, back on, checked connections, and started hissing/crackling very loud, so shut it off. Completed Audyssey with just L/R speakers and have been listening to music and some movies. Couple of random observations:
The good
-I have the 708P’s in our living room and really like them. I knew the 705p was going to obviously be much smaller, but it is really small.
-Crossed at 80hz with two Rythmilk L12 subs, it is pretty amazing how good they sound in such a compact package.
-At my seating distance of around 12 feet or so they appear to get plenty loud for my use. Generally listen around -10db.
The not so good
Of the 3, 1 was in very good condition in like new condition, with white bag etc. The other 2 were both very dusty/dirty with no white bag, or enclosed in any bag. One had what I thought was a crack but looks like may just be a scratch. Then of course there was the one that will need to be replaced. I really like them a lot but am concerned the longer term durability. I’m thinking of sending all 3 back and getting 3 passive speakers instead despite really liking the two working ones!

That is simply unacceptable. B-stock does not mean, "Scratch and dent sale." I would return them fast. The QC on the test and repack was obviously not there. Any self respecting sale rep you contact about this would be miffed at this.

 

[Shazb0t]

That is simply unacceptable. B-stock does not mean, "Scratch and dent sale." I would return them fast. The QC on the test and repack was obviously not there. Any self respecting sale rep you contact about this would be miffed at this.

Isn't that exactly what it means?

 

[Doodski]

Isn't that exactly what it means?

Not in my experience. I would anticipate possibly some small scratches maybe and a repack. The inoperative speaker with hissing and crackling is due to it not being tested properly before being put out for resale. Dust and muck is more of the same. If I was having a warehouse sale which I have had and inviting customers over to see the stuff I would offer scratched and dented but calling it B-stock doesn't mean the customer gets either lucky or very unlucky. There is a high degree of reputation involved here and the integrity of JBL is just not present in this situation.

 

[Dj7675]

That is simply unacceptable. B-stock does not mean, "Scratch and dent sale." I would return them fast. The QC on the test and repack was obviously not there. Any self respecting sale rep you contact about this would be miffed at this.

Most likely what I will do. I wasn’t concerned much about the. Scratch, but not being clean and sealed in a bag was unexpected. I also understand that things fail and that is what the warranty is for. But just thought they would have been better inspected before they went back out.