TABAQ TL for Tangband

I encountered a problem with my TABAQ's that I hadn't encountered before. For a couple of weeks I have been going nuts trying to source a sort of scratching sound (weird and difficult to describe) coming from the speakers. Recently I had the same problem with a pair of PSB B15's hooked to a Marantz 1060 amp, though the sound was more "electrical sounding" and it happened with the amp on or off or playing at any volume level. Turned out it was the transistors of the amp, and it was repaired. So, I figured I had the same problem with my MX113 Pre, or maybe a problem with the CJ MV75 amp.

My TABAQ's were hooked to a Dayton Audio DTA-1, and I was using digital sources. They were working fine. A couple of weeks ago I moved them to be used with my main system, until I finish my new DIY speakers. As mentioned the pre is a Mc MX113, the amp is a tube CJ MV75 with KT90, and the sources are IPod (direct), Jolida JD602A CDP, and Rega P2 with Grado Gold Cartridge. Maybe too much for the TABAQ. The drivers are 3" TB W3-881SI. I never did the BSC for them, never felt they needed it and crude measurements I took with pink noise and the JL Audio software on my IPhone 5S was pretty flat, very nice. Soundwise I never felt they need the BSC.

Having said that, I noticed that at certain frequencies or resonance, I get the scratching sound I was talking about, and it is not the pre nor amp. I believe that at certain frequency lots of resonance is being created and I get the scratching sound, it goes away and if I turn the volume down or use my wimpy DTA-1 it doesn't happen. When I put my ear close to the each speaker the scratchy sound is not direct, it sounds like it is being spread omnidirectionally.

What do you think the problem might be? Can it be a consequence of not having the BSC and frequency being augmented at certain low Hz?

Build material is 1/2" MDF, polyfill weighed and in the top third of the enclosure as recommended (sounds great), cabinet well sealed, with front firing vent.
 
TABAC MICRO

Hi

Just finished the speaker for Tang Band 2 inch driver. Price and size taken into consideration this is very nice - as long as you keep the volume at moderate level. Increasing the bass a little on the PC EQ makes this speaker a really good solution - e.g. like a PC speaker.

Admitet - this is more Fun Fi than Hi Fi, but anyway :)

The front is black acrylic and the top is black glass.

Take a look at the instructions and more pictures here.

Hi from
Bjørn
 

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Could anyone tell what type of stuffing is used by Björn in the original turorial (http://coolcat.dk/bjoern/TABAQ_TL_for_TB.pdf)?

It looks like something that would stay in place, does not interfere with the cone and should be relatively inexpensive (considering that was what Björn was aiming for) so that would tick all the boxes for my Tabaq speaker that I will be building in a few weeks. (so far only a pair of W3-871's on the way).