JBL 708P Review (Professional Monitor)

[jhaider]

What's weird is that JBL specs this speaker as only having 2dB more max output than the 308p. I own the JBL 308p, and I don't get that same sense. The 308 gets uncomfortably loud at spls I know my ears can actually tolerate(very obvious when switching back and forth with JTR 212RT). The 708p though is just like you describe. It gets as loud as I care to listen, and sounds wonderful at that volume. It's like JBL is either overselling the 308p's dynamics, or underselling the 708p's dynamics.

I suspect there is a bandwidth where they are similar. One interesting thing about the compression driver is per S-und-R’s 705P measurements there isn’t an SPL advantage over its bandwidth compared to a good dome. However, 708 has a much more advanced woofer with much more power in (I think) a larger cabinet compared to 308P. So it should be able to play much louder down low.

Note that in S und R’s testing the teeny tiny 705P had more bass output at their distortion thresholds than 308 did. That speaker, at least a well sorted example (sigh) is a real eye opener.

 

[Zzzzz...]

... One interesting thing about the compression driver is per S-und-R’s 705P measurements there isn’t an SPL advantage over its bandwidth compared to a good dome. ...

Then why bother with a compression driver in the first place?

Have a look at this video:

Peter Chaikin from JBL mentions that the reason for the CD is to achieve higher SPLs.

 

[Pearljam5000]

1. I saw some reliability issues over at that other thread, is that a concern?
2. Are they worth the price gap over the 308P MKII other than the SPL being higher?
3. Will there be any B-stock on Amazon?

 

[Robbo99999]

1. I saw some reliability issues over at that other thread, is that a concern?
2. Are they worth the price gap over the 308P MKII other than the SPL being higher?
3. Will there be any B-stock on Amazon?

People are saying the 708p is noticeably more pleasant at higher listening levels, other than that I'm not particularly convinced on a substantial difference. (And on a theoretical level perhaps there will be less unit to unit variance amongst the 708's due to it being a substantially more expensive speaker.)

 

[thewas]

Nothing against KH 310, mind. Had I heard KH 310 before I heard the JBL 7-series, KH 310 would be likely be speakers by which I judge everything in that size/price category.

My words , their fantastic mid dome gives a cleanness that I haven't heard on any 2-way loudspeaker till a similar price range and my guess is that its mainly due to low HD and IMD.

 

[pierre]

Another EQ this time only with peak biquad and only dealing with peaks (and no valley) on the freq curve.
Algorithm try to flatten the LW and the Early Reflections.

The table below gives the impact on the pref score with a growing number of PEQs:

INFO:spinorama:OPTIM JBL 708P START ['Listening Window', 'Early Reflections'] #PEQ 20 Freq #5 Gain #5 +/-[0.2, 12] Q #5 [0.1, 12] Loss 722.43 Score 4.97
INFO:spinorama:Speaker JBL 708P Iter  0 Optim converged loss 10.11 pref score 5.08 biquad PK F:  911Hz Q:6.95 G:-3.24dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  1 Optim converged loss 5.52 pref score 5.61 biquad PK F: 9012Hz Q:0.40 G:-2.15dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  2 Optim converged loss 8.70 pref score 5.69 biquad PK F:14259Hz Q:6.62 G:-2.25dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  3 Optim converged loss 8.84 pref score 5.74 biquad PK F:  669Hz Q:12.00 G:-1.13dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  4 Optim converged loss 8.75 pref score 5.75 biquad PK F:  370Hz Q:12.00 G:-0.67dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  5 Optim converged loss 8.56 pref score 5.84 biquad PK F: 3660Hz Q:12.00 G:-1.03dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  6 Optim converged loss 8.59 pref score 5.88 biquad PK F: 3010Hz Q:12.00 G:-0.75dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  7 Optim converged loss 8.66 pref score 5.92 biquad PK F: 2549Hz Q:12.00 G:-0.71dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  8 Optim converged loss 8.64 pref score 5.96 biquad PK F: 7105Hz Q:12.00 G:-0.59dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  9 Optim converged loss 8.68 pref score 5.97 biquad PK F:  987Hz Q:12.00 G:-0.38dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 10 Optim converged loss 8.65 pref score 5.99 biquad PK F: 5326Hz Q:12.00 G:-0.27dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 11 Optim converged loss 8.78 pref score 5.96 biquad PK F:  527Hz Q:12.00 G:-0.74dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 12 Optim converged loss 8.84 pref score 5.99 biquad PK F:  671Hz Q:12.00 G:-0.71dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 13 Optim converged loss 8.82 pref score 6.00 biquad PK F: 1766Hz Q:12.00 G:-0.44dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 14 Optim converged loss 8.94 pref score 5.97 biquad PK F:  797Hz Q:12.00 G:-0.49dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 15 Optim converged loss 9.03 pref score 5.93 biquad PK F:  510Hz Q:12.00 G:-0.47dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 16 Optim converged loss 9.10 pref score 5.95 biquad PK F:  669Hz Q:12.00 G:-0.46dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 17 Optim converged loss 9.07 pref score 5.96 biquad PK F: 1334Hz Q:12.00 G:-0.25dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 18 Optim converged loss 9.15 pref score 5.93 biquad PK F:  797Hz Q:12.00 G:-0.31dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 19 Optim converged loss 9.22 pref score 5.91 biquad PK F:  533Hz Q:12.00 G:-0.30dB in 500 iterations
INFO:spinorama:OPTIM END JBL 708P: best loss 9.16 final score 5.91 with 20 PEQs

Here is the full EQ. I would keep only the first 3 after that it is mostly sharp filters to remove small oscillations that may or may not be audible.

Preference Score 5.0 with EQ 5.9
Generated from http://github.com/pierreaubert/spinorama/generate_peqs.py v0.5
Dated: 2021-02-07-16:44:53

Preamp: -0.2 dB

Filter  1: ON PK Fc   910 Hz Gain -3.24 dB Q 6.95
Filter  2: ON PK Fc  9012 Hz Gain -2.15 dB Q 0.40
Filter  3: ON PK Fc 14259 Hz Gain -2.25 dB Q 6.62
Filter  4: ON PK Fc   668 Hz Gain -1.13 dB Q 12.00
Filter  5: ON PK Fc   369 Hz Gain -0.67 dB Q 12.00
Filter  6: ON PK Fc  3660 Hz Gain -1.03 dB Q 12.00
Filter  7: ON PK Fc  3010 Hz Gain -0.75 dB Q 12.00
Filter  8: ON PK Fc  2549 Hz Gain -0.71 dB Q 12.00
Filter  9: ON PK Fc  7105 Hz Gain -0.59 dB Q 12.00
Filter 10: ON PK Fc   987 Hz Gain -0.38 dB Q 12.00
Filter 11: ON PK Fc  5326 Hz Gain -0.27 dB Q 12.00
Filter 12: ON PK Fc   527 Hz Gain -0.74 dB Q 12.00
Filter 13: ON PK Fc   670 Hz Gain -0.71 dB Q 12.00
Filter 14: ON PK Fc  1766 Hz Gain -0.44 dB Q 12.00
Filter 15: ON PK Fc   796 Hz Gain -0.49 dB Q 12.00
Filter 16: ON PK Fc   509 Hz Gain -0.47 dB Q 12.00
Filter 17: ON PK Fc   669 Hz Gain -0.46 dB Q 12.00
Filter 18: ON PK Fc  1333 Hz Gain -0.25 dB Q 12.00
Filter 19: ON PK Fc   796 Hz Gain -0.31 dB Q 12.00
Filter 20: ON PK Fc   533 Hz Gain -0.30 dB Q 12.00

You will notice that the complete filter (the sum of all the biquad, picture left, down) doesn't show sharp peak but a relative smooth curve.
The manual filter is from flipflop@.

You can look at the impact on the spinorama:

and on the PIR:

 

[stunta]

Any thoughts on what would be good crossover point to subs with a HPF so the 708P can sing along at its best? I currently have a pair of 708Ps sitting on top of a pair of Rythmik FM8s (dual 8" woofer design). I am considering adding a 12" sub to the setup.

Thanks

 

[FrantzM]

Another EQ this time only with peak biquad and only dealing with peaks (and no valley) on the freq curve.
Algorithm try to flatten the LW and the Early Reflections.

The table below gives the impact on the pref score with a growing number of PEQs:

INFO:spinorama:OPTIM JBL 708P START ['Listening Window', 'Early Reflections'] #PEQ 20 Freq #5 Gain #5 +/-[0.2, 12] Q #5 [0.1, 12] Loss 722.43 Score 4.97
INFO:spinorama:Speaker JBL 708P Iter  0 Optim converged loss 10.11 pref score 5.08 biquad PK F:  911Hz Q:6.95 G:-3.24dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  1 Optim converged loss 5.52 pref score 5.61 biquad PK F: 9012Hz Q:0.40 G:-2.15dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  2 Optim converged loss 8.70 pref score 5.69 biquad PK F:14259Hz Q:6.62 G:-2.25dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  3 Optim converged loss 8.84 pref score 5.74 biquad PK F:  669Hz Q:12.00 G:-1.13dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  4 Optim converged loss 8.75 pref score 5.75 biquad PK F:  370Hz Q:12.00 G:-0.67dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  5 Optim converged loss 8.56 pref score 5.84 biquad PK F: 3660Hz Q:12.00 G:-1.03dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  6 Optim converged loss 8.59 pref score 5.88 biquad PK F: 3010Hz Q:12.00 G:-0.75dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  7 Optim converged loss 8.66 pref score 5.92 biquad PK F: 2549Hz Q:12.00 G:-0.71dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  8 Optim converged loss 8.64 pref score 5.96 biquad PK F: 7105Hz Q:12.00 G:-0.59dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter  9 Optim converged loss 8.68 pref score 5.97 biquad PK F:  987Hz Q:12.00 G:-0.38dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 10 Optim converged loss 8.65 pref score 5.99 biquad PK F: 5326Hz Q:12.00 G:-0.27dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 11 Optim converged loss 8.78 pref score 5.96 biquad PK F:  527Hz Q:12.00 G:-0.74dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 12 Optim converged loss 8.84 pref score 5.99 biquad PK F:  671Hz Q:12.00 G:-0.71dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 13 Optim converged loss 8.82 pref score 6.00 biquad PK F: 1766Hz Q:12.00 G:-0.44dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 14 Optim converged loss 8.94 pref score 5.97 biquad PK F:  797Hz Q:12.00 G:-0.49dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 15 Optim converged loss 9.03 pref score 5.93 biquad PK F:  510Hz Q:12.00 G:-0.47dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 16 Optim converged loss 9.10 pref score 5.95 biquad PK F:  669Hz Q:12.00 G:-0.46dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 17 Optim converged loss 9.07 pref score 5.96 biquad PK F: 1334Hz Q:12.00 G:-0.25dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 18 Optim converged loss 9.15 pref score 5.93 biquad PK F:  797Hz Q:12.00 G:-0.31dB in 500 iterations
INFO:spinorama:Speaker JBL 708P Iter 19 Optim converged loss 9.22 pref score 5.91 biquad PK F:  533Hz Q:12.00 G:-0.30dB in 500 iterations
INFO:spinorama:OPTIM END JBL 708P: best loss 9.16 final score 5.91 with 20 PEQs

Here is the full EQ. I would keep only the first 3 after that it is mostly sharp filters to remove small oscillations that may or may not be audible.

Preference Score 5.0 with EQ 5.9
Generated from http://github.com/pierreaubert/spinorama/generate_peqs.py v0.5
Dated: 2021-02-07-16:44:53

Preamp: -0.2 dB

Filter  1: ON PK Fc   910 Hz Gain -3.24 dB Q 6.95
Filter  2: ON PK Fc  9012 Hz Gain -2.15 dB Q 0.40
Filter  3: ON PK Fc 14259 Hz Gain -2.25 dB Q 6.62
Filter  4: ON PK Fc   668 Hz Gain -1.13 dB Q 12.00
Filter  5: ON PK Fc   369 Hz Gain -0.67 dB Q 12.00
Filter  6: ON PK Fc  3660 Hz Gain -1.03 dB Q 12.00
Filter  7: ON PK Fc  3010 Hz Gain -0.75 dB Q 12.00
Filter  8: ON PK Fc  2549 Hz Gain -0.71 dB Q 12.00
Filter  9: ON PK Fc  7105 Hz Gain -0.59 dB Q 12.00
Filter 10: ON PK Fc   987 Hz Gain -0.38 dB Q 12.00
Filter 11: ON PK Fc  5326 Hz Gain -0.27 dB Q 12.00
Filter 12: ON PK Fc   527 Hz Gain -0.74 dB Q 12.00
Filter 13: ON PK Fc   670 Hz Gain -0.71 dB Q 12.00
Filter 14: ON PK Fc  1766 Hz Gain -0.44 dB Q 12.00
Filter 15: ON PK Fc   796 Hz Gain -0.49 dB Q 12.00
Filter 16: ON PK Fc   509 Hz Gain -0.47 dB Q 12.00
Filter 17: ON PK Fc   669 Hz Gain -0.46 dB Q 12.00
Filter 18: ON PK Fc  1333 Hz Gain -0.25 dB Q 12.00
Filter 19: ON PK Fc   796 Hz Gain -0.31 dB Q 12.00
Filter 20: ON PK Fc   533 Hz Gain -0.30 dB Q 12.00

You will notice that the complete filter (the sum of all the biquad, picture left, down) doesn't show sharp peak but a relative smooth curve.
The manual filter is from flipflop@.

View attachment 111061

You can look at the impact on the spinorama:
View attachment 111062

and on the PIR:

View attachment 111063

OK

it’s one thing hat we may have forgotten about this speaker: it’s powerful onboard DSP. Those are illustrations of what this very DSP can provide. Judicious use of the onboard DSP transforms what is, based on Amir’s review, a very good speaker in a superlative speaker. One wonders why JBL did not tuned the speaker out the box in that fashion.
This is one hell of a speaker. Top flight.

 

[jhaider]

Any thoughts on what would be good crossover point to subs with a HPF so the 708P can sing along at its best? I currently have a pair of 708Ps sitting on top of a pair of Rythmik FM8s (dual 8" woofer design). I am considering adding a 12" sub to the setup.

IMO they have enough headroom that the room rather than the speaker determines xover point. With multiple distributed subs I like to start at 120Hz and adjust based on measurements from there. I target minimizing variance and don’t care too much about FR - automated “room correction” handles that nicely.
I’ve been playing with Dirac Live Bass Control recently (still subs on single cluster, because I’ve not had time to rewire) and everyone in our house preferred 120Hz to the default 70Hz in this room.

 

[BDWoody]

OK

it’s one thing hat we may have forgotten about this speaker: it’s powerful onboard DSP. Those are illustrations of what this very DSP can provide. Judicious use of the onboard DSP transforms what is, based on Amir’s review, a very good speaker in a superlative speaker. One wonders why JBL did not tuned the speaker out the box in that fashion.
This is one hell of a speaker. Top flight.

In the spirit of what the hell...

I just plugged the top three directly into mine through the back panel. There is one more PEQ slot available under the User EQ menu option, and 9 under the Room EQ option. There really is a lot of functionality in these things.

 

[jhaider]

Judicious use of the onboard DSP transforms what is, based on Amir’s review, a very good speaker in a superlative speaker. One wonders why JBL did not tuned the speaker out the box in that fashion.

Here I would not speculate on sonic improvements based on measurements. There may be room for improvement but we’re at a level of performance that improvements need to be validated by listening rather than graphs.

As I believe @thewas stated earlier in the thread, obviously JBL had the processing headroom to do more signal shaping but choose not to.

 

[mhardy6647]

In the spirit of what the hell...

I just plugged the top three directly into mine through the back panel. There is one more PEQ slot available under the User EQ menu option, and 9 under the Room EQ option. There really is a lot of functionality in these things.

View attachment 111074

Now, I am just sayin': Those two three pieces of cellophane tape look like an audiophile tweak to me...

 

[Robbo99999]

Now, I am just sayin': Those two three pieces of cellophane tape look like an audiophile tweak to me...

View attachment 111084

Damn that is strange!

 

[BDWoody]

Now, I am just sayin': Those two three pieces of cellophane tape look like an audiophile tweak to me...

View attachment 111084

Ha! I had a buzz that I was tracking down. I didn't even see the ones at the top...
I tightened up the plate but never took out the little tape shims. Good luck ya know.

I will have to do more tape mods, as the front green lights are now on, indicating EQ of some sort is active. All these mods are exhausting.

 

[pierre]

Here I would not speculate on sonic improvements based on measurements. There may be room for improvement but we’re at a level of performance that improvements need to be validated by listening rather than graphs.

As I believe @thewas stated earlier in the thread, obviously JBL had the processing headroom to do more signal shaping but choose not to.

the most likely reason is that you want to keep all the peqs for correcting the speaker+room.

 

[Zzzzz...]

https://twitter.com/i/web/status/1356702182884708360

 

[richard12511]

1. I saw some reliability issues over at that other thread, is that a concern?
2. Are they worth the price gap over the 308P MKII other than the SPL being higher?
3. Will there be any B-stock on Amazon?

The 308p is definitely the better value, imo, but that's almost always the case when comparing good cheap speakers to good expensive speakers.

 

[infinitesymphony]

What's weird is that JBL specs this speaker as only having 2dB more max output than the 308p. I own the JBL 308p, and I don't get that same sense. The 308 gets uncomfortably loud at spls I know my ears can actually tolerate(very obvious when switching back and forth with JTR 212RT). The 708p though is just like you describe. It gets as loud as I care to listen, and sounds wonderful at that volume. It's like JBL is either overselling the 308p's dynamics, or underselling the 708p's dynamics.

There are a couple of reasons for that:

1. While the 708P and 308P are close in peak output, continuous output is 6 dB higher for the 708P (double the amplitude).

2. The SPL ratings for the 308P were achieved with the system distortion criteria of "<10% THD at maximum output with full compressor / limiter engagement." That sounds like an unhappy speaker playing a signal that is already squashed.

 

[stunta]

IMO they have enough headroom that the room rather than the speaker determines xover point. With multiple distributed subs I like to start at 120Hz and adjust based on measurements from there. I target minimizing variance and don’t care too much about FR - automated “room correction” handles that nicely.
I’ve been playing with Dirac Live Bass Control recently (still subs on single cluster, because I’ve not had time to rewire) and everyone in our house preferred 120Hz to the default 70Hz in this room.

Thanks. I too am using DLBC and it defaults to 70Hz. Have it crossed over at 100Hz but hard to tell the difference one way or the other. Once I get the 12" sub, I am thinking i will set the FM8s to mid-bass (50-200Hz; physical switch at the back), the 12" sub at 50 Hz and see what DLBC comes up with. I hope it won't get confused.

 

[Frank Dernie]

The 308p is definitely the better value, imo, but that's almost always the case when comparing good cheap speakers to good expensive speakers.

I won't get the chance to do it myself but the 308 - 708 direct compare would be an interesting way to hear similar speakers but one with superb quality drivers in a good cabinet to one with inexpensive but good drivers in an inexpensive cabinet.
I would try to do this if I lived in the US.