URGENT HELP: Demounting the FST at HTM1D!

[Deaftone]

I did recently buy a 2 yrs old HTM1D to my 800-series setup. It's a great speaker and the sound of it is brilliant!

Yesterday I decided to tighten the diamond tweeter house on top of the Marlan head, this because it was very loose compared to the tweeter house on top of my 802D's. I know other at this forum has been told from B&W Support that it's normal that the Marlan head or tweeter house has various degrees of mounting.

As you know you do have tofirst loosen the FST-driver. I did this by removing the alu phase-plug in front, and carefully screw a 10 mm long M6 screw in the hole the phase-plug was mounted in. This to secure a good grip in front of the FST-driver when it falls out/loosens.

Then I carefully unscrew the screw at the back of the Marlanhead, witch holds the FST-driver in place, while I holded my other hand at the 10mm long M6 screw I had placed in front of the FST-driver. I also did count the number of turns I unscrew the screw at the back of the Marlanhead.

Then I carefully pulled out the FST-driver a bit, I didn't remove it quite, but instead pulled it out approx.10-15 cm so it rested on a soft cloth at the front edge of the Marlanhead. It wasn't necessary to loosen the wires to the driver.

This operation did work out well - I could now get easy access to the nut holding the house of the diamond tweeter. In a controlled way I tighten the nut some turns, so that the tweeter house did feel as tight as on my 802D's.

After been doing this, I did the same operation in reverse by carefully slide the FST-driver back in place by holding at the M6 screw I mouted in front, also maked sure the wool fillings inside of the Marlan head didn't get out of position.

When I then maked sure the edge of the FST-driver was in right place in front, I tighten the screw at the back of the Marlanhead with apporx the samenumbers of turns I counted while unscrewing it. Approx 13 1/2-turns, and by this maked sure it was thight as on the 802D's.

Beside this I did some adjustments to my homecinema later on that evening. I tweaked some of the harsh acoustics in the room by putting up some curtains at each side of the frontspeakers, to make sure the room wasn't that harsh sounded anymore.

After recalibrating my setup I then put on a DVD I just got, it's called. "21", don't know if there's a bad DD 5.1-quality on this but in certain chapters with many noises - the voices of persons sounds a bit wooly compared to before I did this. The open tone in the HTM1D has changed a bit characteristic - it sounds like it's a bit more closed in the upper/midtone.

My question is: Is this due to that I have perhaps put too much curtains in the room OR could I have done something wrong demounting and inserting the FST?? What could actually go wrong during this process?

Feedback wanted, it's very important for me to find out!

[beden1]

The easiest way to find out what changed your open sound is to remove/open the drapes you installed to see if the sound returns to what you had before.

I'm going to say the drapes contributed to your sound now appearing muffled. In my room, I have one wall with drapes, (floor to ceiling is 24') that can open or close. The sound goes from alive (with drapes fully open) to nearly dead sounding (with drapes fully closed). With them closed, I also need to turn up the volume. I adjust my drapes depending on the affect I want to hear at the time.

It appears you were very careful in working with your speakers.

[Deaftone]

The easiest way to find out what changed your open sound is to remove/open the drapes you installed to see if the sound returns to what you had before.

I'm going to say the drapes contributed to your sound now appearing muffled. In my room, I have one wall with drapes, (floor to ceiling is 24') that can open or close. The sound goes from alive (with drapes fully open) to nearly dead sounding (with drapes fully closed). With them closed, I also need to turn up the volume. I adjust my drapes depending on the affect I want to hear at the time.

It appears you were very careful in working with your speakers.

Thank you for your reply!

The same thought has striked my mind as well because the room feels a bit too muffled when having a conversation in there. I know that the first thing you kill with too much "drapes" in a room, will be the tweeter and especially the midrange.

Hopefully this is the reason why the tone in the HTM1D isn't quite open as it used to be. I will try to remove some of the drapes to see if this affects the sound like it used to be.

I've also been thinking about what could possibly go wrong during the demounting I did - it's quite easy to do if your carefull og the only thing in my eyes that could affect the tone in the speaker afterwards, will be how tight you turn the screw in the back of the FST-driver.

There isn't anyone who has tried this themselfes?

[mjb]

You do need to "tune it" after replacement (due to the gasket, which does not have to be replaced everytime). I think the way to do it is to knock the cone carefully with a finger while turning the big outer ring on the back by hand - turn the ring either direction until the taping sound is at its most damped (neutral). Then tighten the middle screw (with a coin) to secure the assembly. I've just been through the same thing with my 802D, a B&W man performed the procedure and I watched, so this is not strictly first hand information but close to it.

[Deaftone]

How is the outer ring at the back actually connected to the Marlan head? Is it just fastened by the end screw witch holds the FST-driver?

When knocking carefully at the Marlan head there is different sounds depending where you knock - the sound it produces is also pretty similar to when I knock at the 802D's.

[mjb]

I'm not sure, but there is a big rubber assembly in there suspending the middle ring where the rod from the driver slides through. I think its pressed in, but don't hold me to it. If you finger tap the the yellow driver cone and it sounds about the same as your 802's you're probably OK, but it should definitely not resonate or ring, it should be a dull thud. This thud changes depending how taught the assembly is.

[Deaftone]

OK, thank you very much for all the info about this!!

I'll try to first remove some of the curtains I've hang up in the room, then re-calibrate the setup and try listening again.

[RobP]

You do need to "tune it" after replacement (due to the gasket, which does not have to be replaced everytime). I think the way to do it is to knock the cone carefully with a finger while turning the big outer ring on the back by hand - turn the ring either direction until the taping sound is at its most damped (neutral). Then tighten the middle screw (with a coin) to secure the assembly. I've just been through the same thing with my 802D, a B&W man performed the procedure and I watched, so this is not strictly first hand information but close to it.

I think the guy who "tuned" your FST driver was just putting on a show, I went through this awhile back and had a lengthy discussion with my dealer, I was told that there is no specific torque range or tuning specs that they are given from the factory when replacing the driver.

[Deaftone]

There's a possibility that you may stretch the kevlar in the FST-driver when tuning at the screw in the end - or at least close the Marlan head completly so it will sound neutral...

Interresting though that your B&W dealer told that there were no measurements about the torque for the FST.
Wonder how they know at the B&W factory how hard they should tighten the FST-driver? Do they run tests and then eventually tighten or loosen the screw? In that case, what will the local delar du when replacing it, don't think they have the measurement equipment for this tuning process.

It's possible for me to move the FST-driver a little bit up by lifting the alu phase plug in it, also for the 802D's I can do this. So completly tight isn't it supposed to be I guess.

[RobP]

There is a torque spec from the factory, but it is used for QA purposes in shipping. This info came from B&W directly, it does seem odd that there would not be a specific spec for it though.

[mjb]

I think the guy who "tuned" your FST driver was just putting on a show, I went through this awhile back and had a lengthy discussion with my dealer, I was told that there is no specific torque range or tuning specs that they are given from the factory when replacing the driver.

Show or not, the Marlan head needs to be air tight, and if the driver isn't pulled firmly back into the head (so that the gasket properly seats) it won't be. Tapping the cone will give an indication of air-tightness by its tone. A neutral thud = an air tight fit. Hence there being no torque settings: tighten it up whilst tapping the cone, when the tone goes dull (because the assembly is airtight), its enough. No need to over tighten (pulling the driver too deep into the head).

[Deaftone]

Is there any chance of that the sound in the FST-driver will be different if the acoustic material in the head that the rod is surrouded by has minor changes? I'm thinking of when you're pulling the rod back in return through the same hole in the material to the back of the speaker. I did remember that it's a bit stiff to pull the rod back again, so there might be minor changes of how the acoustic material is sitting in the Marlan head.

I do think that if you measure the FST-driver, the tuning of it after a process like this might be different - but is it possibel to hear such minor changes??

[Ash]

Hi Deaftone,

Interresting though that your B&W dealer told that there were no measurements about the torque for the FST. Wonder how they know at the B&W factory how hard they should tighten the FST-driver? Do they run tests and then eventually tighten or loosen the screw? In that case, what will the local delar du when replacing it, don't think they have the measurement equipment for this tuning process.

I'm planning to open the marlan enclosure and change a few parts as well, and have asked for some clarifications from B&W tech support regarding screw tightening.

The answer was to tighten the back screw until its finger tight i.e. tighten it using your finger until you cannot turn it with your finger anymore, at this point make a 1.5 turns with the screw driver (or whatever tool you are using).

I believe head mounted midranges, do not need a specific tension when screwing the back screw as they are decoupled and mounted with drawbar. However with lower 800 series models (without marlan head), the FST driver is cabinet monted (not decoupled) and requires a specific tension on the back screw which needs to be measured.

How is the outer ring at the back actually connected to the Marlan head? Is it just fastened by the end screw witch holds the FST-driver?

As for the gasket (rubber part behind the FST) I believe that it is not connected to anything, it is simply placed between the marlan head and the FST driver which is placed on it.

The tip that B&W support gave me regarding installing the gasket was to make sure that it doesn’t bubble out from the Marlan head. Not very clear but I think they meant to ensure that the rubber surrounds the FST drive entirely and uniformly, without any bends in the rubber (look at the rubber part on your 802Ds for guidance on how it should look in the end). Placing the FST driver properly on the rubber and tightening the back screw as per the above description should give you an air tight enclosure, and everything should be okay.

Hope this helps

[Deaftone]

Hi Deaftone,



I'm planning to open the marlan enclosure and change a few parts as well, and have asked for some clarifications from B&W tech support regarding screw tightening.

The answer was to tighten the back screw until its finger tight i.e. tighten it using your finger until you cannot turn it with your finger anymore, at this point make a 1.5 turns with the screw driver (or whatever tool you are using).

I believe head mounted midranges, do not need a specific tension when screwing the back screw as they are decoupled and mounted with drawbar. However with lower 800 series models (without marlan head), the FST driver is cabinet monted (not decoupled) and requires a specific tension on the back screw which needs to be measured.




As for the gasket (rubber part behind the FST) I believe that it is not connected to anything, it is simply placed between the marlan head and the FST driver which is placed on it.

The tip that B&W support gave me regarding installing the gasket was to make sure that it doesn’t bubble out from the Marlan head. Not very clear but I think they meant to ensure that the rubber surrounds the FST drive entirely and uniformly, without any bends in the rubber (look at the rubber part on your 802Ds for guidance on how it should look in the end). Placing the FST driver properly on the rubber and tightening the back screw as per the above description should give you an air tight enclosure, and everything should be okay.

Hope this helps

Hi,


I did found out some few interesting points yesterday. First of all the amp I'm using to drive the HTM1D (Midgard Oberon 6.1 - 1 channel 600W ICE power) isn't working properly or is just too different from the amp I use for the 802D's (Classe CA-2200). I did send a stereo signal to the Classe amp - using the HTM1D as speaker "L" and one of the 802D's as speaker "R". Then I listened to the tweeter and the FST-driver at both speakers in a very close range. I discovered that the sound is almost equal to both - I do perhaps feel that the HTM1D sounds a bit more tight and shaper/harsh at the top? It feels like the 802D has a minor touch of more body and deatils in the tweeter/midrange area. Could there be a minor damage in the damping resistor causing this - or is it just my ears or the different position of the speakers in the room?

I did also discover a difference between how the tweeter was connected inside the HTM1D and the 802D's tweeter house. At both the 802D's the + connector sits at the LEFT side when pulling the tweeter straight out.
At the HTM1D's tweeter, the + connector sits at the RIGHT side of the dome. The + and - cabels has also been crossed inside the housing, like if someone has changed their natural position comming up from the hole in it. First I thought the tweeter had been connected wrong, but there was a red mark at the connector at the dome where the red cabel was connected. Does this indicate that the tweeter has been replaced/changed by the owner before me? Or else the cables wouldn't be crossed? This is easy checking by unscrewing the blank pipe at the back - and slowely press the tweeter out at the front of the housing using the pipe in the back.

Off-topic: What parts are you planning to change btw?

[misterdoggy]

Problem is, when we start fooling around with the speaker, and we are unsure of what we are doing, we always are afraid that we did something wrong.

You can never really be reassured that everything is 100%. Although it probably is

[wettou]

Hi Deaftone, I'm planning to open the marlan enclosure and change a few parts as well, and have asked for some clarifications from B&W tech support regarding screw tightening.

WHY would you want to do that??

[misterdoggy]

If it aint broke dont fix it (famous last words)

[Ash]

Off-topic: What parts are you planning to change btw?

WHY would you want to do that??

If it aint broke dont fix it (famous last words)

Okay, here is the story.

I bought a pair of pre-owned N800s. Beautiful speakers, but had some flaws in them, as follows:

1- Problem was finding that in one speaker, an area of the rubber gasket that surrounds the FST driver was actually tucked behind the driver, on the top side of the driver. This does not guarantee an air tight enclosure in the Marlan head, effecting the sound. I complained to the shop, and made them contact B&W support. They sent me a new gasket and answered all questions I have about the replacement process.

2-Looking more closely to the same area with the gasket problem I noticed markings on the plastic area of the FST and the Kevlar, I think it has been hit by something, but this is only visible on close inspection (thank god the Marlan head was not scratched!).

3- Other than that, the Kevlar was slightly stained, like many people touched it or something. I noticed this, and on another occation a friend pointed it out, so I wasn't crazy hahaha. The staining was on both speakers in different ways, but worse on the one with gasket problems.

4- Last problem, was with one tweeter, again on the speaker with gasket problems. Before buying the speaker, the shop told me that one tweeter was damaged during transit and had to be replaced. Now, when I first got the speaker, I opened the box and this tweeter enclosure was open slightly (I guess from shipping) I twisted the front part of the tweeter back on, however, it was slightly loose now, which means that if you hold the front part of the tweeter and move your finger, the front part moves slightly (annoying but I would say not a significant issue). Then when I tried to remove the tweeter grill it would not come off, even when applying slight force. Inspecting closely, it seemed as if the tweeter grill was pressed against the tweeter enclosure and thus went back more than it should and as a result some how is now stuck, wierd!!

Now putting all that together and the fact most of the issues above are close to each other, my suspision is that the tweeter damage story had something to do with the suspected hit on the FST drive and kevlar, and also why the gaskets has moved.

Given that at a minimum, I would have to replace the gasket (as it is effecting sound), I'm forced to open the Marlan enclosure. Since, I will have to take this risk now, I decide to relpace everything that was annoying me which are both FST drivers, front gaskets on both speakers and the entire tweeter enclosure on one speaker. Then the speaker will be in a very good condition, unless I mess the speaker up during the process and commit suicide hahaha.

BTW 800s are amazing even with all these issues I had; while writing this I was listening to Pink Floyd "the wall", man! those speakers sound awsome.

[Deaftone]

Yesterday I watched the movie "The Others" with Nicole Kidman, there's some scenes in the movie (approx 1h 10min+) where she's screaming pretty loud. I then felt that the HTM1D was clipping some of the signal at the top. I didn't have the volume at any higher level then I usually do. Could there be a minor damage in the damping resistor causing this, cause the tweeter produces good sound at normal levels? Is there usually like either the damping resistors work or it doesn't at all?

Ash: If you do also tend to open the tweeter during the change of parts, please give me a feedback witch side the + and - connectors sits at your tweeter/dome.

[Ash]

Ash: If you do also tend to open the tweeter during the change of parts, please give me a feedback witch side the + and - connectors sits at your tweeter/dome.

Will do

[beden1]

Yesterday I watched the movie "The Others" with Nicole Kidman, there's some scenes in the movie (approx 1h 10min+) where she's screaming pretty loud. I then felt that the HTM1D was clipping some of the signal at the top. .

Did you try connecting the HTM1D to your CA-2200 to see if something is happening from the amp currently driving the HTM1D, as opposed to something wrong with the speaker itself?

[Deaftone]

Did you try connecting the HTM1D to your CA-2200 to see if something is happening from the amp currently driving the HTM1D, as opposed to something wrong with the speaker itself?

Yes, I did the test yesterday with both combinations, also just sending the signal to the center channel by disconnecting all the other channels. I must say I didn't notice any particular differences this time... I also sent a sweep tone at 16Khz to the HTM1D and compared this to one of my 802D's. It sounded pretty equal - so then the tweeter and resistor damping is working propperly?

I'm also starting to think of that it may happen to be the room itselfes causing the different tone in the HTM1D versus the 802D's...

Will try to tweak a bit more on this part.