Foster / Fostex HF Driver repair (Traynor K4)

Started by Elantric, September 15, 2013, 07:56:28 AM

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Elantric

Many Full Range amps we talk about here employ Foster / Fostex HF Drivers.

The Traynor K4 is one example, but many other amps use these same type drivers, often with a different Horn , but the underlying 1 inch voice coil is the same.

If you play a lot of loud gigs, you might find these HF drivers need frequent servicing, and some folks spend $60 for whole new Foster PHT-406 (Traynor P/N 7286),
http://www.paudiothailand.com/showproduct.cfm?id=576

http://www.paudiothailand.com/pdf/products/PHT-406.pdf

when they could simply replace the diaphragm/ voice coil only for $17 instead

http://www.simplyspeakers.com/?

http://www.simplyspeakers.com/foster-replacement-speaker-diaphragm-d-420-4.html


Foster & Fostex Speaker Diaphragm 4-Pack Part # D-420-4
Includes 4 x D-420 Diaphragms for Foster & Fostex speaker horn drivers
Voice coil: 1" (25mm)
Diameter: 1-3/4" (45mm)
Length: 2-7/8" (72mm)
Impedance: 8 ohm, DCR: 7 ohm
Phenolic dome with copper voice coil on Nomex former.
Our most popular replacement diaphragm!
Fits Foster & Fostex N30, 025H30, H025N30, H025N27, H025N28, FT300H drivers and many others including
PS, Carvin, Yamaha, N30 Foster diaphragm, 1" phenolic for N30, 025H30, 025H27, Ho25N30, FT300H, used in Carvin, PAS, SWR, Peavey, Crate, etc. 8 ohm.
Foster: N-30, N30, N 30, N08, 025H30, H025N30, H025N27, 025N27, H025N28, FT-300H, FT 300H, FT-500H, FT 500H, FT500H, HT 404, HT-405, HT 405, HT-406, HT 406, HT-407, HT 407, HT-408, HT 408, HT-410, HT 410, HT 411, HT-412, HT 413, PHT-404, PHT 404, PHT-405, PHT 405, PHT-406, PHT 406, PHT-408, PHT 408, PHT-408, PHT 408, PHT-410, PHT 410, Fostex: FT300H, HT404, HT-404, HT411, HT-411, HT413, HT-413, Ampeg: 86-515-08, Crate: PE-15H, PE 15H, Carvin: 025N01D, Community, Cerwin Vega: C-8G, C8G, C 8G, X-Tealth, Roland: KC-500, KC 500, KC-550, KC 550, Selenium: RP-DT150, RP DT150, SHS, Sunn, SWR: SWR Goliath, SWR Redhead, SWR Megoliath, Sound Tech, Yorkville, P-Audio: HT-406, HT406, Yamaha: JAY-68625 JAY 68625, Tosh TE 12H, TE12H, Traynor and many more!



In this video, we replace the speaker horn diaphragm on the Fostex horn. Foster H025 and Cerwin Vega H025 models are identical in most cases. Diaphragm part # D-420 is used for this speaker

Elantric

#1
http://www.simplyspeakers.com/foster-replacement-speaker-diaphragm-d-420-4.html

I ordered a 4 pack of replacement Foster/Fostex 1" horn diaphragms (now have 3 spare) from Simply Speakers in Florida and followed the steps in the video above to swap out the defective HF  voicecoil diaphragm and now have a great sounding Traynor K4 again.

Rather easy, and great service from Simply Speakers.




BBach

Elantric, Do you just remove the grill and take the horn out the front, or is a more onerous invasive operation required. I don't think it can be done laparoscopically.

Elantric

#3
I was curious, so I removed the Traynor K4 12" Woofer first, which allowed good visual access to the rear of the Foster Horns in the K4.

If its your first time, know there is a factory installed rubberized tape gasket sandwiched between the speaker baffle board and the rear of all the transducers : (2) Foster HF Horns. (2)  5" Midrange  and (1) 12" Woofer.
This can present a bit of a hurdle to remove the HF horns without resorting to a failed attempt using a small pry bar which results in damage to the wood Speaker baffle board in the K4's Wood Cab.
I highly advise remove the 12" Woofer first when troubleshooting or working on ANY of the K4 Speakers or HF horns or Passive Crossover network.

Read the K4 Service Manual
http://traynoramps.com/downloads/servman/smk4.pdf


(I wish all Service manuals were as accessible and detailed as the Traynor K4 Service Manual )

BBach

#4
Thanks for the advice. There will be considerably less cursing the dark due to your lighting a candle. Your generosity is astounding.
Do you order news gaskets from Traynor or reuse the old ones?

Elantric

I was careful, worked slowly and reused the original speaker baffle board gaskets  - all works and sounds smooth with no distortion and gets very loud.

BBach

#6
After taking out the woofer and compression drivers I am confused. The k4 Finishing wiring diagram as shown from the perspective of looking at the back of the speakers out toward the front of the amp, has the crossover and MF and HF on opposite sides of the way my amp is made/wired. The woofer in the diagram is wired the same as my amp. If you were to  (in the diagram) leave everything wired as it is and moved the MF and HF speakers (as well as the crossover) to opposite sides, it would represent the way my amp is wired. In other words, Brown and orange leads closest to the woofer, they would be toward the (back facing) outer left side and conversely, the yellow and white leads would be would be on the inside closer to the woofer. So the woofer, to my thinking, is out of phase with the other speakers. Maybe it doesn't make any difference since the woofer is summed to mono. I'm not quite sure. I'm not sure if the left and right jacks will be reversed or not (not that that matters much. It's easy enough to switch the cords) Was this the way your amp was ? Am I ok just wiring up as it was?
After thinkIng about it, Nothing is changed electrically. Just the pan is reversed.

Elantric

If your amp was purchased new, I would vote to keep original wiring and signal flow. (You took photos right?)
The big issue is maintaining the same polarity and not getting wires crossed on the (+) and (-) lugs on each speaker.

BBach

I bought it on eBay, but there is no evidence of the speakers ever being removed and certainly no one would or could have moved the crossover to the opposite side. Like I said in my edited post, After thinking about it, the amp really isn't wired any differently, The right and left MF and HF speakers are just located on opposite sides of the woofer. I'm going to put it back the way it was after I replace the HF diaphragm/voicecoils. Thanks for your help.

imerkat

(Needed help pertaining to advice on this thread so decided to resurrected from the grave  ;D)

One of the HF Drivers in my Traynor K4 started sounding as if the Cab simulator was off. I isolated to make sure it was that one driver (panning using a high pass filter, then flipping the HF Drivers around so it wasn't the amp's crossover) and it was distorting as suspected. So I bought the diaphragms and installed it on both drivers as per the video and it work great but after two gigs at high volume, it was back! Same driver so I know it wasn't the install job.

My question is; do I need to buy a new driver? I mean its just three parts, I can't imagine that the magnet or the horn can be the culprit. Any advice please?

Elantric

#10
Could be
* Bad batch of replacement drivers

* Installations was slightly out of alignment

* Playing too loud for the amp

There are HF DRIVER   Protection BULBS that can be inserted in series with the driver  - to aid in  preventing DC transients blowing the voice coil of the HF driver/

http://www.parts-express.com/eminence-px-bulb-replacement-tweeter-protection-lamp-for-crossover--290-659

imerkat

Thanks Elantric!
I think it's a combination of the last two points. I re-installed the diaphragm and made sure to keep it in alignment while tightening the screws and Vualá! Distortion is gone but I fear it isn't permanent and will revert after the a loud gig. Thank you for the link to the protection bulbs but I see there back ordered now.

Always appreciated!

Elantric

#12
http://www.fullcompass.com/product/312808.html?utm_source=googleps&utm_medium=shopping&utm_campaign=googleps&gclid=CLrG1ai6kMACFcI7MgodIwUAcA







This is a clip of a JBL control 28 speaker's crossover being driven at high volume. Note the protection bulbs glow with the dynamic peaks, demonstrating how the non-linear resistance of an incandescent bulb is used for protection.

Elantric

http://peavey.com/support/technotes/soundsystems/top10damage.cfm

Top 10 Ways To "TOAST" Speakers and Diaphragms

1.FREQUENT OCCURRENCES OF HARD FEEDBACK
If you go "ouch" after that last squeal, chances are so did your speakers! This one is compounded by proceeding to use the speakers after they have probably been damaged.

2.IMPROPER BIAMPLIFICATION: CROSSOVER TOO LOW OR TWEETER AMP TOO HIGH
Always check your speaker specs for the best crossover points.

3.NOT ENOUGH SPEAKER SYSTEMS FOR SPL REQUIREMENTS OR PROPER COVERAGE
Most folks throw "extra watts" at the same speaker complement: add extra channels of amplification in concert with additional speakers.

4.TRYING TO COVER AN OUTDOOR GIG WITH YOUR INDOOR SYSTEM
Outdoor gigs require at least 12 dB (16X power) more sound output than indoors, and as much as 20 dB (100X power!) to really do it right.

5.EXCESSIVE EQ
The classic "smile" EQ curve is actually smiling at your speakers imminent demise! Keep in mind that EQs are best used for cutting, not boosting the signal. Need more highs? Reduce the bass...Need more lows? Reduce the highs.

6.INCORRECT USE OF COMPRESSORS/LIMITERS
Excessive compression squeezes the life out of your music AND your speakers!

7.NOT ENOUGH AMPLIFIER HEADROOM
Too little power, and amplifier clipping becomes the norm.

8.SUDDEN TRANSIENTS WHILE THE SPEAKERS ARE HOT
Turn-off thumps, plugging/unplugging mics, etc.

9.CLIPPING THE SIGNAL BEFORE IT GETS TO THE POWER AMP
Improper mixer gain distribution, line signal too hot, etc.

10.KEEP USING YOUR SPEAKERS AFTER DAMAGING THEM...
And failing to have the crossover parts checked for damage after abusing the speaker system that way! Let your ears be your guide. If you hear distortion from any clean inputs, damage has likely occurred. Note: Any time you suspect a problem, be sure and check with your local Peavey dealer/service center.

gumtown

Quote

7.NOT ENOUGH AMPLIFIER HEADROOM
Too little power, and amplifier clipping becomes the norm.
I can't recall how many times (on other forums) I have suggested under powering speakers can damage them, only to be 'put in my place' by others (censured) that say you can't.
Certain amplifier designs, when pushed past clipping can loose their zero crossing symmetry, and end up pushing one supply rail harder than the other, effectively having more of one DC rail past 50% duty cycle, which cooks voice coils.
Even if it's a 100 watt amp driving a 300 watt speaker.
My belief is to have your amp rated higher than the speaker, and drive you speakers with a much cleaner signal.

or am I wrong to think that??
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

Elantric

QuoteI can't recall how many times (on other forums) I have suggested under powering speakers can damage them, only to be 'put in my place' by others (censured) that say you can't.
Certain amplifier designs, when pushed past clipping can loose their zero crossing symmetry, and end up pushing one supply rail harder than the other, effectively having more of one DC rail past 50% duty cycle, which cooks voice coils.
Even if it's a 100 watt amp driving a 300 watt speaker.
My belief is to have your amp rated higher than the speaker, and drive you speakers with a much cleaner signal.

A low wattage 30 watt solid-state bass amp driven too hard delivers long duty cycle square waves to the speaker and the speaker voice coil (that was rated for 100 watts) spends too much time interpreting the square wave  signal as a DC voltage and overheats and burns out.

Ive seen this many times  -