General Forum

Re: Most peculiar Lab5 Vibrations

Peter Jacobs — Thu, 03 Apr 2008 19:46:14 GMT

Ok all, thanks for all your responses and debates especially Dave Moulton.

I went off to our local DIY store and got 4 650 mm square concrete pavers.Two sandwiched together to make a concrete plinth about 5 inches high. Placed the Lab 5s on these. Re calibrated and then used a couple of B&O demo CDs to test any change. I also played the DTS DVD Terminator 3. Not much change at all. Interestingly I did noticed by standing right next to the lab 5s that (when they were on the concrete plinths and without being on them too) that when the calibration sequence started for the bass frequencies I could lliterally feel the floor boards deflecting.

Now Dave Moulton asked a very focussed question. The size of the joists supporting the floor. Well, (don't do this at home) I had to go off to our local pest control, get some "spider dispersal bombs" let them off under the house. Then wait an hour before crawling underneath. The gap is just over 24". The floor joists are solid hardwood, 6" x 8". The floor itself is solid hardwood boards 3/4" thick.

So, I took the lab5s off the plinths, then placed the US "Big Fat Dots" speaker vibration damping pads (note these can be used for speakers up to 90 kilos). Re calibrated, then played the same tracks and DVD.

Result - A HUGE DIFFERENCE, POSITIVE of course. I anticipated that it would be better, as when I started the calibration I stood next to the speakers and did not notice MUCH deflection of the floor boars all though there was a hint of it. I re calibrated again and this time sort of leaned on the larger aluminium disc of the lab 5s. Now no deflection of the floors.

End result, the 5s are back to their best. !!!!!!!

I actually took a day off work today to enjoy them, just to celebrate.

Herbies Audio Lab. They are on the web. $ US 70 + $US 25 postage to Australia. for 10 discs. $ placed in a square and one in the centre.

Hope this helps anyone else with the same problem.

Peter

Re: Most peculiar Lab5 Vibrations

koning — Mon, 17 Mar 2008 09:01:22 GMT

Peterjacobs did you find a solution?

Re: Most peculiar Lab5 Vibrations

soundproof — Fri, 07 Mar 2008 09:53:14 GMT

Dave,

would setting a cross-over with Audyssey or another system above that handled by the BL5s for the rest of the frequency range be advisable?

Re: Most peculiar Lab5 Vibrations

Dave Moulton — Fri, 07 Mar 2008 09:38:09 GMT

In response to Kawo's post about Audissey, my business partner Manny LaCarrubba undertook a study of various room correction systems as part of a project we are currently working on. Audissey was one of the systems - it is a full bandwidth system and Manny's conclusion is that it works OK, and has a nice user interface, but that he prefers the outcomes obtained by some of the other systems under test better.

In this case, the problem is clearly a low-frequency problem and ABC should handle it quite well. The fact that it doesn't appear to be handling it well suggests to me that the entire floor is being excited, resulting in a large vibrating membrane (the floor) whose response cannot be adequately controlled by altering the response of the exciters (the BL5s). Hence my suggestion of floor supports directly under each speaker, to restrict floor motion at the speakers, effectively making them nodes. This should help.

In general, I do not support the idea of overlaying two room correction systems – I can imagine serious interactions and unanticipated consequences. Given Kawo's excellent system, I'm not at all sure that Audissey would yield much if any improvement, while it might actually degrade the performance of the BL 5s.

I hope this helps.

Best regards,

Re: Most peculiar Lab5 Vibrations

dp — Fri, 07 Mar 2008 08:53:44 GMT

not wanting to go too off topic but the bridge scene in Mission Impossible 3 is awesome (volume 70)

much better with lab 5s than beolab 2..

Re: Most peculiar Lab5 Vibrations

kawo — Fri, 07 Mar 2008 05:52:49 GMT

Die Hard 4.0 with the Lab5 is the best! My sofa vibrates...and not only a little bit :-)

Karsten

Re: Most peculiar Lab5 Vibrations

soundproof — Wed, 05 Mar 2008 02:17:20 GMT

The disadvantage with Audyssey is that it processes the signal, and therefore reduces its resolution a little; the advantage would be that it treats the entire frequency range relative to the room, and not just the bass.

I can attest to the BL5s being able to move walls and floors. When we were watching the latest Bruce Willis Die Hard movie, and we got to where it's the truck against the jet fighter on the highway overpass, the entire apartment building seemed to be shaking as the overpass was falling apart.

Stiffening up the floor from underneath is a good idea, with possible a higher WAF than the slabs!

Re: Most peculiar Lab5 Vibrations

kawo — Wed, 05 Mar 2008 00:37:45 GMT

Dave, could you please share some more details of your expirience with the audyssey device? You mentioned that this could not be a promising solution for the problem of the starter of the thread.

I have treated my room with some acustic elements after consulting an acustical expert and looking now into the last step to imptove the sound.

So the Audyssey is on my list as I heard from owners of very well acustical treated rooms that this device the "cherry on top of the cake" . I have two lab5, lab 7-4 and two lab 3 with a BS3 in my 3,60 by 4m room

Karsten

Re: Most peculiar Lab5 Vibrations

Dave Moulton — Tue, 04 Mar 2008 20:53:30 GMT

I'd like to know more about the joists supporting your floor. The BL5s have enough power to actually cause the floor to move if it isn't stiff enough, and that may be the cause of what you've noticed.

I thought my studio floor was plenty stiff until I installed the BL5s. Then I noticed some severe deflection problems. This past year, as part of studio rehab, I put little lolly colums under each speaker in the crawl space to "ground" them by restricting their motion, and it tightened up the bass considerably. You might consider something similar.

I would warn you off Audissey, not because it doesn't work (it does - we've measured it) but because it doesn't work as well as ABC for this sort of problem.

I hope this helps.

Thanks for listening.

Re: Most peculiar Lab5 Vibrations

soundproof — Tue, 04 Mar 2008 08:03:56 GMT

peterjacobs:
Thanks Beoaus. I shall try them this weekend. Only problem is I understand it is not advisable to have a shiny reflective surface underneath the speakers ??....

Here is my room with speakers positioned. I have now brought them away from the walls by about 1.5 feet.

The image is not coming up on my browser. Try storing it in jpg? Go to Options, next to Compose above. And add the image with the Browse function, if you haven't already done so.

And shiny reflective surfaces can't be much of a problem, as most of the photography by B&O of these speakers goes against that bit of advice. But the marble doesn't have to be smooth polished - and it could look quite beautiful - imagine dark marble slabs underneath? (Damn, I'm going to get curious and be wondering about getting my own, now.)

Re: Most peculiar Lab5 Vibrations

Peter Jacobs — Tue, 04 Mar 2008 07:11:12 GMT

Thanks Beoaus. I shall try them this weekend. Only problem is I understand it is not advisable to have a shiny reflective surface underneath the speakers ??....

Here is my room with speakers positioned. I have now brought them away from the walls by about 1.5 feet.

Re: Most peculiar Lab5 Vibrations

beoaus — Tue, 04 Mar 2008 04:43:10 GMT

There is a place called Peraway Marble (spelling) north of Melbourne. They have very large offcuts available. Could be a little more stylish...

beoaus.

Re: Most peculiar Lab5 Vibrations

Peter Jacobs — Tue, 04 Mar 2008 00:35:13 GMT

15 cm + is going to have to be covered indeed with black silk.... Thanks for your advice. I shall set out this evening to see if I can get 12 paving slabs... I still can't get over the irony...AUD 25,000 worth of speakers now made more effective with a 15 cm slab of concrete worth AUD 25 !!! Still, needs must !!

Peter

Re: Most peculiar Lab5 Vibrations

soundproof — Mon, 03 Mar 2008 20:32:18 GMT

They're hefty, but it's really worth it to move them about a bit, as you're hunting for the best place to have them (that is also realistic as placement!) I got big differences just moving them a foot.

As to thickness of slabs - 15cm+.

And don't get some that ring when you strike them with something, the material they're made of should be quite inert

Re: Most peculiar Lab5 Vibrations

Peter Jacobs — Mon, 03 Mar 2008 20:12:32 GMT

Again, all, thanks for the responses. Last night I thought I'd try the easy bit first. So I moved the lab5s that were in the two corners of the room and about 12 inches from the back wall, a further 1 and a half foot away from the back and side walls, re calibrated and guess what, the base seemed a lot better. (I played a particular track with very low bass frequencies on a before and after scenario).

Now, chaps, as most of you know, I had to weather the initial shock from my wife when I told her I needed GBP 30,000 pounds for my system and then when she saw the Lab 5s she actually said what the hell was I thinking getting some INDUSTRIAL MACHINERY into our home !!!. Can you imagine if I now go to her and say the only way to get the very expensive INDUSTRIAL MACHINERYperforming to their optimum I need to place them on concrete slabs ???

As it stands last Christmas it cost me AUD 55k to get her a new MX5 in "compensation" for "those hideous things"....

Anyway, I can't resist it now. She is away on a long weekend soon, so its off to BUNNINGS (The equivalent of B&Q in the UK, to get some slabs... I can always cover them in the finest black silk .. One question.....how thick do you think these slabs need to be..and can I get away with say 3 - 6 paver slabs on top of each other ?

I wonder what David Moulton or David Lewis might say ??

Peter