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-   -   JBL LSR305 tweaking (https://www.diyaudio.com/forums/multi-way/320206-jbl-lsr305-tweaking.html)

Juhazi 16th March 2018 08:02 PM

JBL LSR305 tweaking
 
1 Attachment(s)
I have just purchased a pair of modern legendary active monitors JBL LSR305. They were on sale at thomann.de obviously because a MkII model has been released recently.

This little gem has been reviewed eg. here JBL LSR305 Studio Monitors

I ran some measurements and listened to a single speaker today. Measurements line up with noaudiophile well. Sound is very impressive but there is a strong coloration making them sound boxy, also knucle test result is poor. I put the mic almost in contact with panel and every measurement showed strong distortion around 240Hz. It is obviously a 1/1 wall resonance based on height of the cabinet. --> http://semimac.org/wp-content/upload...-Enclosure.pdf

Internal cross-bracing should kill that well, I'll try that during next days and report my findings!

6L6 16th March 2018 08:19 PM

Looking forward to seeing what you come up with! I have a pair of LSR305 with the subwoofer for my computer rig, I think very highly of them, but like anything built to a budget, there is room for improvement.

Rokytheman 16th March 2018 10:59 PM

Interesting !
Which mic are you using- And how close to the cabinet?

Wondering if for instance MiniDSP umik1 can be used to test for distortion.

xrk971 17th March 2018 04:19 AM

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I got these a few years ago to try them out. The polar dispersion is very nice measurement - but the mid bass was very weak and distorted. Just lacked midrange power and presence. I had to return them because could not sound anywhere near as good as my FAST with 10F/RS225. But what bothered me was that despite being internally DSP’d - the response was not flat.

http://www.diyaudio.com/forums/full-...ml#post4347377

It’s the red curve:
Attachment 674785

Juhazi 17th March 2018 08:22 AM

Quote:

Originally Posted by Rokytheman (https://www.diyaudio.com/forums/multi-way/320206-jbl-lsr305-tweaking-post5374444.html#post5374444)
Interesting !
Which mic are you using- And how close to the cabinet?

Wondering if for instance MiniDSP umik1 can be used to test for distortion.

I use UMIK-1 and REW. For this resonance test I held the mic's foam-covered head in contact with the panel. The metal body didn't touch panel. I played a normal sweep at same spl level as in other measurements (roughly 85-90dB/1m)

The amps are not terribly effective and like XRK said, bass gets stressed easily. Normal mesurements show remarkable distortion below 400Hz. Some of it may be resonance-based, but it is not as peaky as the panel measurement.

I have been thinking of cutting off the waveguide to be used in a semiactive 3-way that I am planning now. We will see... Other option is to make copy molds to clone the waveguide shape...

manninen 17th March 2018 09:18 AM

Hi man, you´re going the wrong way! Those drivers are way too small for your Man cave :)

But amazed for the 105€/pc prize

Bitumihuopa 4 kpl - Aanenvaimennus Bitumihuopa - Biltema

I have some biltema bitum band-aid left if any help taking down those resonances

1audiohack 17th March 2018 04:26 PM

Quote:

Originally Posted by Juhazi (https://www.diyaudio.com/forums/multi-way/320206-jbl-lsr305-tweaking-post5374291.html#post5374291)
I have just purchased a pair of modern legendary active monitors JBL LSR305....

“Legendary”?!? That right there is hilarious to me.

They are a $90. internally amplified speaker and yes they perform pretty well for the price but c’mon, what did you really expect?

Wrap them in a towel around them and ratchet strap a couple of bricks to the sides of them and see what they sound like.

The 708’s might acheive legendary status as the M2 is moving toward.

Barry.

Brinkman 17th March 2018 04:48 PM

I have a pair of white LSR305s for my garage and a single LSR308 for my Etherwave theremin. Very interested in watching this thread.

I have considered removing the baffle and filling the backside with sikaflex sealant (self-leveling?) to deaden it a bit. An internal cross-brace is not a bad idea either.

Juhazi 17th March 2018 06:52 PM

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Legendary humour? But they really are extraordinary for the price!

An internal cross-brace made -25dB reduction in resonant sound, measured with backplate opened and knockin the side panel. Distortion peak measured at 60m (2') was reduced too. Me happy for solid 1 hour "work" on these. I hope that my daughter willl be happy too for her new desktop speakers!

1audiohack 17th March 2018 07:28 PM

Good work! That’s real improvement.

Barry.


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