A Question about DBL's

Mario, my understanding of the alu pads is that you want the spikes to locate on them (so need to make a sharp impression) but not to pierce right through to the point where they couple to the pad - the aim is to "rigidly decouple" as it were.

If you've never done the gasket and you are having doubts then I would strongly suggest you prepare for a full breakdown and rebuild with new pads and gasket kit.

Thank you Richard, I think you are right, a full breakdown will also give me piece of mind.

If i remove the old pads and repair the timber with Ronseal and make it flat, will I need to staple the new pads down? I don't have the stapler, I could use a very small button head self drill screw on either side of the pad. Thank you again for responding.

Mario.

As an aside.....Another user on here has had great success with adding an additional structural layer to the suspended wooden floor under his speakers. I think he glued down some plywood over the existing boards, then glued new boards on top of that. I'd consider this (or something similar), and also whether you could double up or otherwise reinforce the plasterboard behind the speakers. Both things would be relatively inexpensive and might give some benefits.

Yes, the pads should be stapled.  If you don't have an air stapler or a heavy duty staple gun then you should try to hire or borrow one. Supposedly you can have some success by using heavy duty staples and a hammer, but there's every likelihood you could cock it up and trash the pads.  It's worth getting this bit done right.

These speakers, like SBLs, should never be transported with the bass boxes in place - though how you'd move DBLs with the bass boxes in place is beyond me. 

To test the gaskets are sealed, just push the bass units in - you cannot damage them unless you are totally hamfisted. If they come out slowly the gasket is fine, but if they come out immediately the seal has gone. If you are worried, wear some gloves. 

When I had SBLs I was shown how to set them up by Naim - put the box in place and press down gently so that the spikes just pierce the pads to rest on the wood. They shouldn't just rest on the pads, nor should they bite into the wood. 

Not sure about the impact of the pads, but sealing is key.

What are you using to drive them?  I have active, and they really come alive with a 500 on them (as you would hope!) but a bit lacking with 300s.  Good, but missing that dynamism.

Thank you all, I have them active, 300 on tweeters, and 2 x 250DRs on the mid and bass. Hope to DR the 300 soon. CDS3/555 ps and 552 in front, not DR'ed yet. I transported the large L frame cabinet in its original boxes with cardboard packing in the spaces between it and the bass box. The foam inside the box obviously did not perfectly match the "L" shape of the main cabinet, but there is a lot of room in that main box. No damage to edges or any of the veneer occurred. I wanted to use them active so any 500's are well out of my budget.

Mario.

Maybe not a permanent change, but have you tried the 300 on the bass?  I would be interested to know what you think.  You should get some pretty exiting bass, although you may ultimately decide to keep your current configuration.

I have 500/300/500.  I tried all combinations and this works best.  I love the effect of the 500 on the bass, although I can hear something missing on mid - especially at lower volumes.

Gavin L posted:

Maybe not a permanent change, but have you tried the 300 on the bass?  I would be interested to know what you think.  You should get some pretty exiting bass, although you may ultimately decide to keep your current configuration.

I have 500/300/500.  I tried all combinations and this works best.  I love the effect of the 500 on the bass, although I can hear something missing on mid - especially at lower volumes.

Is your mid boosted by 1dB relative to the others? If not then the something missing could be due to the 300s 1dB lower gain than the 500!

No it is not.  So you may have something there.  Someone else mentioned this too.  Not sure if this is something I could adjust myself with the 362?  It would certainly be a lot cheaper than that upgrade.  Especially as I could benefit a lot by a Supercap DR for my 362 as it is currently powered by an old Olive unit.

I thought a picture is in order.

Gavin L posted:

No it is not.  So you may have something there.  Someone else mentioned this too.  Not sure if this is something I could adjust myself with the 362?  It would certainly be a lot cheaper than that upgrade.  Especially as I could benefit a lot by a Supercap DR for my 362 as it is currently powered by an old Olive unit.

I believe the Snaxo can be adjusted

Gavin - Yes, the SNAXO has three tiny internal pots for HF/MF/LF level adjustment.  There should be a pair of tiny dots to show the initial factory calibration for nominal settings.  This is your reference should all go pear-shaped. Be careful though as they wear off ever so easily so if faint or missing remake them with a sharpie so you have a base-line reference. I would very much suggest you ask your dealer over to help out here as it's a lot easier with two.

Mario posted:

Hello all, I have owned a pair of cherry DBL's for about 5 months or so and have been quite happy with them. I previously had NBL's and they are definitely a big step up. The thing is, that the best part of them for me is their mid range and treble purity, naturalness and true to life sound. When you look at DBL's, the first thing that you would expect to be raving about is the bass response. Bass is good, but I just feel there is much more to come. I have just recently purchased new DBL spikes (old ones were a little blunt) and used fraim chips (upside down) and levelled the speakers too perfection.

The thing I have never done is the gasket. Now my DBL's have been well looked after and the gasket seems to be very done, but both speakers have been transported more than once with the bass box still in place. The seal still seems perfect, looked with a torch and they both look in tact. I'm not willing to push the driver in to check the seal as it seems very stiff and rigid. I have no problems pushing in the SBL mid/bass as it is much smaller but don't really want to put much force on the big 15 inch driver. Any way, my main question is about the aluminium pads.

The DBL manual instructs to push the bass box down gently on a dry run to create an IMPRESSION on the aluminium pads. I am guessing that my spikes have probably punctured through the pads, but if you read the SBL manual, it actually says to push the bass cabinet gently until you actually puncture through the pads and allow the spikes to come into contact with the wood. I just can't see if my pads have been punctured, the gap and angle of sight is just not good enough. Also, the DBL manual does not mention the soap on the gasket for easy removal, and I don't think mine have had soap on them as they don't seemed to have moved during transit. 

 

My question is simply  are the spikes on the main cabinet supposed to punch through the aluminium pads on the DBL's bass box, or is only an impression supposed to be made?

I have read people refer to the aluminium pads being changed because they are perforated, so I guess that means only an impression on the pads must be present, but not sure.

I actually have new gaskets but I don't  think soap or dish washing liquid has been used on my gaskets prior to the silicone being applied so it will be a bit of work. It's really the SBL manual that has placed doubt in my head as it says to push the spike through the pad. Don't really want to destroy the gasket if the spike through the pad is ok.

 

Floors are suspended wood type and rear wall is only a stud and plasterboard wall, although, this did not seem to bother NBL's too much when they were in the same space!

 

Best regards

 

Mario.

 

p.s. Jon Honeyball, Ron Toolsie, Peter Swain, Officer DBL and all other resident DBL experts, I'm hoping you can help with this one! Thanks.

You might want to find out what silicone is used. When I did mine a year ago it had to be a special type.

Regarding your comment on bass response I'd actually say that DBL's don't give you that 'trouser flapping' bass you'd expect from the size of the bass driver. It's more about the accuracy of the bass. Kind of like that saying "less is more!". I came from Isobariks, which sound really slow and lethargic in comparison to the DBL's. However, with a bit of fine tuning and careful set-up you can often extract another octave bass from those huge drivers. You just need to do everything that you are doing now!

I think you're gonna have to redo the seal, if only for peace of mind. It's not too difficult if you just take your time. You don't need special silicon, just the standard clear stuff is fine. Once you've gotten the units apart (which should be fun if they haven't been subject to the washing-up liquid trick) clean up the surfaces, then apply a thin layer of Fairy Liquid (other makes are available) to both surfaces and leave it to dry before applying an even, unbroken bead of silicon sealant, 4 or 5 mm thick (cut the end of the applicator tube to size) to the bottom box. To make things easy, you really need a couple of spacers to hold the upper box either side just above the silicon bead when you lower it in place, then you can carefully remove them and allow the box to settle down on the sealant. I made a couple of these up myself, 33cm x 12cm x 5.5cm thick, covered in slippery parcel tape so they slide out of the way easily. Don't worry about the pads, there's no need to press down at all, the weight of the upper box being more than sufficient to ensure it settles in the correct position. It's the silicon that's important. Leave it so set overnight before giving it any music to play!

As Mr Geko notes, DBLs initially sound surprisingly gentle and subtle, not the PA sound you imagine from looking at them, but feed them a suitable bit of music with real low frequencies, turn the volume up, & you'll hear proper, undistorted, bass in oodles.

Richard Dane posted:

Gavin - Yes, the SNAXO has three tiny internal pots for HF/MF/LF level adjustment.  There should be a pair of tiny dots to show the initial factory calibration for nominal settings.  This is your reference should all go pear-shaped. Be careful though as they wear off ever so easily so if faint or missing remake them with a sharpie so you have a base-line reference. I would very much suggest you ask your dealer over to help out here as it's a lot easier with two.

Richard, apart from the factory calibration, are they marked (to show 1db)?  I am not sure how much of an adjustment it would be and if it would need to be trial and error.

Another option might be a trip to the factory.  My left and right SNAXO channels are actually reversed which has been a mild irritation for a long time, but I have never wanted to part with it!

(Sorry for borrowing the thread)

Your DBLs need a rebuild... new gaskets and pads.  Proper torque settings are key to DBL performance.  When I owned them I would torque my drivers once a year.  Highly recommended.  

Gavin, the pots are tiny and not marked except to show the initial factory setting.  A good dealer should be able to set them up by ear.  You shouldn't need to make large alterations to the initial setup.  It's tempting to try to use them like a tone control but this is not their purpose.  The factory should be able to set up nominal settings for whichever amp combination you have.  While it's there the channels can be investigated.

Years ago, I had one forum member (Onthlam) fly across to country to help me rebuild my DBLs. The first thing he did was the aluminum pads. After removing the old ones, it was quite obvious that had multiple dimples AND had been perforated. Removing them I recall was no easy task and more than a drop of blood was spilt. Once removed the pits due to the spike perforation were filled with some form of wood putty and sanded smooth. The new pads, instead of being stapled, were carefully drilled and then affixed to the undersurfaces of the appropriate cabinets with wood screws. This made it much easier for future changes. 

The gaskets were also replaced. The seal requires JUST the right amount of a silicone bead. The temptation is to use to much....DON'T. Use just enough. 

Checking the integrity of the seal by pushing in the 15" driver is a simple and totally non-destructive way....no likely to cause any more harm than putting a 9V PP3 battery on across the terminals to gauge polarity. 

Dressing the speaker leads JUST right was another tweak. 

The last step of the DBL rebuild involved bracing the joists beneath the speakers with some extended floor jacks. If you use suspended flooring and have an accessible crawl space beneath, this is STRONGLY recommended. 

The end result was a much more dynamic, swinging and extended presentation-and this was with full blown active electronics. All in all it took about 15 hours, spread out over 2 days. But very well worth it. 

EDIT...crap!, the images don't seem to be uploading

Ron,

Hope you get your pictures showing. I'm dying to see the floor jack shot - seriously.

Thank you all for responding, I think a rebuild is the only way forward. I'll see if my dealer has the staple gun otherwise the drill and screw option may be what I do. I have to say that they actually do sound pretty good as they are, but their abilities are legendary, as is their tweakability. The main point that really got me thinking is that they were moved with the bass box in place so a high chance of alu pad perforation or silicon leak. Ron, those pics look very worth while, I do hope you can get them to be displayed.

Mario.

http://i1376.photobucket.com/a...9508_zpsyptlbtot.jpg

Ron, you need to enter the direct URL of the image.  I've edited one for you.  If you can't do it your end then after I'm back from a Christening lunch I'll do the others for you.

Edit:  OK, had a few minutes to spare, so all done for you.

Many thanks RD for patching my clumsy attempts. 

With regard to speaker cable dressing, having a non interacting pathway for six cables can be a bit of a challenge. Unless Ohthlam is in your corner...

t

Also, when the mechanics of the room are sorted, having a nice clean balanced electrical supply also was revelatory...

And housing your gear remote from the listening area can also be of some benefit...