Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[George Friedman-Jimenez]

This series has been available for several months now. I am still looking to downsize from my QRX112/75s with PRX618XLF, looking for comparable sound quality at about 3 dB lower SPL with lighter weight and smaller size. My application will be small NYC venues maybe 100-150 people, usually just vocals but sometimes R&B backing tracks with live vocals, sometimes recorded Cuban timba dance music between sets. The QRX112 and PRX618XLF sound great for these applications but are just too heavy for frequent moving in and out of my basement studio.

Has anyone used the PRX710 / PRX715XLF combination yet? Any comments or reviews on this combination?

[George Friedman-Jimenez]

The apparent lack of interest in the PRX710 / PRX715XLF combination on this forum and on the internet in general is very surprising to me. Given that these are in stock in many stores and websites, the very light weight and small size of the PRX715XLF subwoofer and the reasonably good acceptance of the PRX6XX line by members of this forum and elsewhere, I would have expected many people to have tried them out and perhaps purchased and be using them, and to have written reviews. I still plan to go listen to them locally but have been unusually busy with my day job recently. Maybe mine will be the first review or comment.

Hasn't anybody on this forum tried them out yet?

[Samuel Rees]

I think the 'lack of interest' on this thread is perhaps because the question doesn't really need answering. Everyone knows the PRX600 series, and JBL is such a consistent large scale producer that everyone seems pretty comfortable assuming the 700s likely sound a little better, and are maybe a little louder than the PRX600 series but are otherwise not much different. There are no crazy spec differences or design differences to inspire curiosity.

For you, consider just picking up a pair of PRX612s - there are great deals on them all over the place as they are going out. If you really want to spend the money, go ahead and give the 700s a quick listen at guitar center and buy em.

[Tom Burgess]

I just got them set up this week and so far have only listened to tracks through them.  I ran into the 715 sub, out of the sub into the 710, with no EQ.  They sound fantastic, can't wait to try them on a gig.

[George Friedman-Jimenez]

Thanks for that opinion, Tom. I have a technical question about the specs of the PRX715XLF subwoofer. I am having trouble understanding the relation between the "loop out crossover frequency" at 120 Hz and the "Internal crossover frequency" at 90 Hz in the JBL spec sheet. This combination does not make sense to me. If anyone who has used this subwoofer could help clarify, I would appreciate your comments.

The spec sheet is here:
http://www.jblpro.com/catalog/General/Product.aspx?PId=467&MId=3

The manual is here:
http://www.jblpro.com/BackOffice/ProductAttachments/PRX700_UserGuide_071813_final_web.pdf

The manual states that the pass-through button applies a 120 Hz 24 dB/octave high pass filter to the output. The spec sheet and manual state that the "internal crossover" is 90 Hz with 48 dB/octave filter slope. If the internal low-pass filter for the subwoofer stays at 90 Hz with a 48 dB/octave filter slope, but the tops are high-passed at 120 Hz with 24 dB/octave slope, this would leave a big hole from 90-120 Hz.

[Gordon Brinton]

...The manual states that the pass-through button applies a 120 Hz 24 dB/octave high pass filter to the output. The spec sheet and manual state that the "internal crossover" is 90 Hz with 48 dB/octave filter slope. If the internal low-pass filter for the subwoofer stays at 90 Hz with a 48 dB/octave filter slope, but the tops are high-passed at 120 Hz with 24 dB/octave slope, this would leave a big hole from 90-120 Hz.

No, there is hardly a hole. The key word here is "Per Octave." An octave is a doubling of frequency, so you need to do a little sketching to see the reality of it.

The next octave above 90 Hz is 180 Hz. If you draw a sloped line starting at 90 Hz and ending at 180 Hz, it should represent a volume reduction of roughly 48 dB by the time it reached the 180 Hz mark. However, at 120 Hz, the volume may only be reduced by 12 dB or so.

Then conversely, if you draw a slope going the opposite direction to represent the HPF for the tops, (slope one octave from 120 to 60,) this slope should represent -24 dB over at the 60 Hz mark. You might see a drop of only about -12 dB around 90 Hz.

By now your sketch should look like a big X. Where the two slopes cross each other, somewhere around 103 or 104 Hz, (the actual cross-over point in this case,) the volume "dip" that appears is only 5 or 6 dB. This is assuming that all slopes are linear, which they may not be.

Given that the two speaker cabinets will offer some amount of coupling at some distance in front of them, you may gain a physical boost of 3 to 6 dB at the center of the cross-over dip, filling the hole rather nicely.

Those JBL engineers wouldn't leave you hanging with an obvious boo-boo in your system.

If you are still unconvinced, do a bit of testing by playing single tones through the system at say, 10 Hz intervals. Measure the volume of each tone with a dB meter to see if it dips through that range.

[David Morison]

Where the two slopes cross each other, somewhere around 103 or 104 Hz, (the actual cross-over point in this case,) the volume "dip" that appears is only 5 or 6 dB. This is assuming that all slopes are linear, which they may not be.

It will also depend on the alignment of each filter. If they're both Butterworth, the hole will be 7.5dB @ 99Hz, but if they're both Linkwitz-Riley then the hole is 10dB @ 99Hz. Of course if they're using FIR filters they're not limited to the standard alignments, so that calculation may be meaningless anyway.

Those both assume the two passbands are playing at an equal level, but if the bass is turned up louder than the tops then that will also fill in the gap a bit more.

Mutual coupling between the 15 in the sub and a 10" up on a pole might help mitigate it a little, but it definitely wouldn't fill in the worst case scenario of a 10dB hole.

George may well be best checking directly with JBL on this.

FWIW,
David.

Edit - corrected value for LR assumption.

[George Friedman-Jimenez]

Thanks. I have emailed JBL but have not heard back yet. The spec sheet does not specify LR, Butterworth or other configuration but either way, as David has calculated, the hole would be substantial. For LR crossovers, we expect that the -6 dB points (the quoted frequencies) for both the high-pass and low-pass filters occur at the same frequency, not 30 Hz apart as seems to be the case here. In that simpler case, the sounds from the 2 speakers add to give zero dip in SPL at the crossover frequency and the SPL remains approximately flat for all the frequencies around that crossover frequency. In modern live sound alignments, with hyped subwoofers, the frequencies may differ by a few Hz and the frequency response of the combined system may not be completely flat, but 30 Hz is a lot and with 24 and 48 dB/octave slopes, a large hole would occur regardless of crossover type.

[Chuck Simon]

" but if the bass is turned up louder than the tops then that will also fill in the gap a bit more."

Which is almost always the case with modern live music.  Interesting stuff, but what really matters is how they sound together.

[Scott Wagner]

Thanks. I have emailed JBL but have not heard back yet. The spec sheet does not specify LR, Butterworth or other configuration but either way, as David has calculated, the hole would be substantial. For LR crossovers, we expect that the -6 dB points (the quoted frequencies) for both the high-pass and low-pass filters occur at the same frequency, not 30 Hz apart as seems to be the case here. In that simpler case, the sounds from the 2 speakers add to give zero dip in SPL at the crossover frequency and the SPL remains approximately flat for all the frequencies around that crossover frequency. In modern live sound alignments, with hyped subwoofers, the frequencies may differ by a few Hz and the frequency response of the combined system may not be completely flat, but 30 Hz is a lot and with 24 and 48 dB/octave slopes, a large hole would occur regardless of crossover type.

Gordon hit the nail right on the head.  Do yourself a favor and re-read his post.  The PRX series are very well designed, and very nice sounding speaker systems.

[ProSoundWeb Community]