Mark IVb modified for front speaker mounting

[bandit2013]

Since I have been using my Mark IV as a test bed for speakers (not intended), I have a speaker that sounds killer but does not quite fit with the rear mounting method (Magnet is too large). I already had all of the 8 typical mounting holes drilled into the baffle. My favorite speaker so far is the Fane Studio. More recently I installed WGS Black Hawk HP 100 which fit well as rear mounted speaker but it lacked the power handling of the Mark IV at higher volume settings (started to smell like it overheated when volume set to 3). Awesome speaker in all respects except for power handling. I wanted to reinstall the Fane Speaker but also wanted more room for tube replacement. Went to the hardware store and got a 1.5 inch drum sanding kit for use on a power drill. Since I have air tools and compressor, I made use of them for better control to prevent removing too much material. Worked like a charm. Installed the T-nuts on the back side and popped the speaker in. The next issue, clearance for the grill. I removed the 4 screws used as stand-offs and insterted 4 thin nuts onto the screws in reinstalled them. Also had a rubber foam matt that was 1/4 inch thick, cut in thin strips for grill support, attached with double sided tape. Used 2 inch stainless star head self drilling deck screws along with decorative washer. Looks great. Grill is easily removed without having to take the chassis apart. Since I have converted to front mounting of the speaker, I was able to get rid of the chassis rattle I was getting with the rear mounted speaker. This rattle has been there since I bought the amp. I always thought it was tube rattle, nope. The Fane speaker never sounded better when mounted this way. Many have claimed that front mounted speakers sound better than rear mounted speakers, since I have had the same speaker mounted both ways, I would agree.

 

[bandit2013]

Unfortunately I did not care much for the grill sticking out. The staples holding the grill cloth on the grill frame did not look so great. I was hoping to avoid any more work such as milling out the interference areas where the speaker frame would hit the grill frame. I used a Craftsman multi tool that is similar to a Dremel that can convert into a small scale router or circular jig saw. That worked really well. Marked the areas to be removed and set the drill depth accordingly. Worked like a charm. Grill fit all the way in against the baffle board. However, the buzz returned since I removed all of the rubber matting material. I went out and found some self adhesive weather stripping material. Has a softer durometer than the floor mat I cut up. Perfect fit, no buzzing. Now I can play clean with deep bass and not have that sound like the amp is going to fall apart. Since that worked so well. I had another project: fix the 412 cab that has a similar issue with the low frequencies.

412 rework, I had a similar buzz in the lower right corner of the cab. When I rebuilt the cab with different speakers it was difficult to reinstall the grill. I even added extra screws to secure the grill in place. Vibration was caused by the plastic stand offs and frame and due to the relatively short screws the frame remained loose. Had plenty of the foam rubber weather strip and placed it in a few locations (12 short strips in the areas where I planned to front screw the frame in place.) I almost considered remounting the EV from rear mounting to front mounting but that would not be wise since the paper gasket used on the EV speaker will separate once the speaker is removed. I had to repair the speakers when I changed all of the screws to secure the speakers a while back and did not want to repeat that again. 9 Screws with the decorative washers secured the grill in place. Did not turn out too shabby either. Best of all, no more low frequency buzz. The only noise I hear in the room other than the sound from the speakers would be the duct work under the floor. Cabinet never sounded better. Used the same method on the oversized 1x12 cab. Perhaps this is overkill but it worked out just fine.

 

[bandit2013]

I did like the WGS Black Hawk HP 100, but after break in, it became too bright with the Mark IV.

The FANE Studio speaker on the other hand, never sounded better. I have an oversized Lopoline 1x12 cabinet that nothing sounded good in, too much bass. So I cut the back out and mounted one of the old V30's. WOW, the FANE in the combo and the V30 in the extension cab and it sounds full. Almost equivalent to the 412 with EVM12L black label speakers. Currently I am using the Reflektor made Svetlana 6L6GC. I had the TAD6L6GC in the amp but decided to put them in the Mark V since my EL34 were beginning to loose gain. Currently I have 4 Tung Sol (v1-v4) and a Mullard re-issue in the PI spot.

What a difference the two speakers made with the Mark IV. Clean channel never sounded better, very natural tones almost acoustic guitar sounding but better with nice piano like bass. Lead is just out of this world.

I did momentarily move the FANE to the extension cab and reinstalled the WGS speaker. It did not stay that way for long. FANE in the Combo and V30 in the extension cab sounded the best.