Jump to content

Fitzmaurice Table Tuba Build - By Mushroom


Recommended Posts

Hi All,

 

I wanted to add a Sub to my audio system, as i was lacking depth & punch down low.

 

This Sub needed to be low cost, best bang for buck......So jumped on-line to search for a new DIY project. Bill Fitzmaurice Table Tuba really got my attention & I knew this project was for me.

 

10" driver & 21" panel height was selected for best performance. Reduced panel height could have been used to save room, but would also reduce performance.

 

I had very basic tools & resources to carry out this build.

 

Material of choice was going to be 2 sheets of 1200 x 2400, 12mm thick Marine Ply, but decided against this & went for 12mm MDF. Bill's Plan says you can use 12mm MDF & also states thicker MDF panels offer no advantage for this design. I also much prefer working with MDF over Ply & i've chosen to overcoat the exterior with a special compound finish coat.

 

Some pics to kick off with then:

 

post-122082-0-12907200-1434609092_thumb.

post-122082-0-89436500-1434609108_thumb.

post-122082-0-17474800-1434609143_thumb.

 

Fitting up the Driver to Panel 3 & check all is OK, before panel installation. I chose to mount the driver to double thickness panel. this ensures extra strength & the extra panel piece has a slightly larger diameter hole to ensure driver edge clearance. With this panel design, i don't need to shape the structural braces to allow for driver/cone extension.

 

post-122082-0-37721700-1434609228_thumb.

post-122082-0-22375800-1434609318_thumb.

post-122082-0-38471800-1434609243_thumb.

post-122082-0-67132900-1434609292_thumb.

post-122082-0-73627500-1434609265_thumb.

 

 

 

Edited by Mushroom01
  • Like 4
Link to post
Share on other sites

Then around & around we go.....panel after panel, brace after brace installation.....

 

post-122082-0-97675100-1434609567_thumb.

post-122082-0-33376500-1434609581_thumb.

post-122082-0-47850300-1434609679_thumb.

post-122082-0-34748800-1434609735_thumb.

post-122082-0-63790100-1434609744_thumb.

post-122082-0-62652700-1434609761_thumb.

post-122082-0-41275500-1434609775_thumb.

 

More to go.....

 

post-122082-0-63754200-1434609873_thumb.

post-122082-0-58279600-1434609906_thumb.

post-122082-0-74785000-1434609927_thumb.

post-122082-0-09607300-1434609985_thumb.

Link to post
Share on other sites

Dizzy yet?

 

post-122082-0-83469100-1434610117_thumb.

post-122082-0-22352400-1434610137_thumb.

post-122082-0-78466800-1434610155_thumb.

post-122082-0-75682500-1434610167_thumb.

post-122082-0-83781400-1434610186_thumb.

post-122082-0-28352200-1434610207_thumb.

post-122082-0-64735300-1434610224_thumb.

post-122082-0-03508400-1434610240_thumb.

 

I've installed small square sections in each corner. This is for extra strength for installing small swivel wheels to the base.

 

post-122082-0-28978800-1434610554_thumb.

post-122082-0-75472300-1434610562_thumb.

post-122082-0-94545000-1434610570_thumb.

  

 

 

 

  • Like 2
Link to post
Share on other sites

Now.... a little trick used to ensure the top side panel is installed with screws correctly.

 

I used a "Temp Marking" paint to leave a detailed "transfer" of the internal panels, to the top side panel. Masking tape was installed to panel ends, before application of Temp paint, to stop contamination & swelling of MDF. The Temp paint was made by myself, as i work for a surface coatings company, developing surface coatings for the construction industry.

 

post-122082-0-61397300-1434611031_thumb.

 

now i have the transfer on the top side, it's now time to drill screw holes.

 

post-122082-0-33978300-1434611403_thumb.

post-122082-0-21998800-1434611415_thumb.

 

Remove the temp paint from both surfaces, then remove masking tape, ready for Glue application.

 

post-122082-0-30131800-1434611572_thumb.

 

Now install top side & screw down.

 

post-122082-0-72261000-1434611629_thumb.

post-122082-0-62919700-1434611658_thumb.

Edited by Mushroom01
  • Like 1
Link to post
Share on other sites


Flat black, water based paint used for internal mouth & base.

 

post-122082-0-90720800-1434612727_thumb.

post-122082-0-02748900-1434612740_thumb.

post-122082-0-19721200-1434612762_thumb.

 

Time to over coat the exterior. 

 

The finish coating system i'm using, consists of 1 primer/sealer coat & 2 coats of finish coat. A special soap is used to protect the surface, like a clear coat.

 

The primer/sealer coat has a "grit/sand" type of particle within it. once dried, it leaves a rough surface, ideal for the finish coat to adhere.

 

post-122082-0-83756600-1434612585_thumb.

post-122082-0-98541000-1434612818_thumb.

 

First coat of Finish coat is trowelled on as a thick paste, then i leave a slightly raised pattern, using the trowel. This pattern is very important, as it must show through the second/finish coat.

 

post-122082-0-65040600-1434612873_thumb.

post-122082-0-47758900-1434612897_thumb.

post-122082-0-75880900-1434612918_thumb.

post-122082-0-41819400-1434612939_thumb.

 

Stay tuned.....more to come.

  • Like 4
Link to post
Share on other sites

Finish coat time.... 

 

Now the first coat of finish coat has dried, application of the final finish coat can commence.

 

This takes quite a bit of work, because you actually polish smooth the final coat with the trowel, as the coating starts to dry. Patience pants on? Check.

 

post-122082-0-37396300-1434613712_thumb.

post-122082-0-80900300-1434613730_thumb.

post-122082-0-20838000-1434613760_thumb.

 

Then i apply the special protective soap coating & polish further with a cloth.

 

post-122082-0-15708700-1434613860_thumb.

post-122082-0-56948600-1434613902_thumb.

 

Now install the driver. 

 

post-122082-0-62576500-1434614062_thumb.

post-122082-0-39316800-1434614023_thumb.

 

Then the wheels..... 2" in height then sink into carpet to just over 1.5", negating the need for a sealed chamber door.

 

post-122082-0-27832700-1434614190_thumb.

post-122082-0-22376400-1434614206_thumb.

 

Don't go away.....a few more pics to come & feed back on how it sounds.  :thumb:  

 

 

  • Like 4
Link to post
Share on other sites
Guest atilsley

Very cool watching another build like this...will be interesting to hear your feedback on response, as this build is 80mm wider than mine, plus uses 10 inch driver vs my 8 inch.

 

What driver are you using and what amp?

 

Any eq'ing?

 

Andrew

Link to post
Share on other sites


Very cool watching another build like this...will be interesting to hear your feedback on response, as this build is 80mm wider than mine, plus uses 10 inch driver vs my 8 inch.

 

What driver are you using and what amp?

 

Any eq'ing?

 

Andrew

Driver & Amp are the following:

 

http://www.daytonaudio.com/index.php/loudspeaker-components/loudspeaker-drivers-by-series/reference-series/rss265hf-4-10-reference-hf-subwoofer-4-ohm.html

 

http://www.daytonaudio.com/index.php/loudspeaker-components/subwoofer-plate-amps/spa250-250-watt-subwoofer-amplifier.html

 

Will add some more pics & stuff tomorrow........ never enough time ay! ;)

  • Like 1
Link to post
Share on other sites
Guest atilsley

Nice...your sub should go lower and louder than mine.

 

My driver is this Tang Band 8 inch, Fs 28Hz, dB 84....amp is my 6 channel Holton Precision Audio

Link to post
Share on other sites

Looks great.

 

Could be a bit late, but sealing the back chamber will make a big difference.

Never too late...... might give it a try sometime. I always believe ya never know unless ya give it a go :)  

Link to post
Share on other sites


Ok......time to whip up a simple box for my plate amp & speaker wire terminal.

 

post-122082-0-05111300-1434689135_thumb.

post-122082-0-56441100-1434689208_thumb.

post-122082-0-70738200-1434689247_thumb.

 

Now get my Son to help me carry in the heavy beast.

 

Ta daaaaaaaaaa  :D

 

post-122082-0-92834800-1434689606_thumb.

 

ok...bad joke...

 

Ta daaaaaaaaaa  :thumb:

 

post-122082-0-39208400-1434689540_thumb.

post-122082-0-07805800-1434689477_thumb.

post-122082-0-21857100-1434689579_thumb.

post-122082-0-16208300-1434689509_thumb.

post-122082-0-03508000-1434689437_thumb.

 

Back soon with some details......

  • Like 9
Link to post
Share on other sites

Never too late...... might give it a try sometime. I always believe ya never know unless ya give it a go :)  

 

Hey, I finally found some logic to go with the no back chamber recommendation.

 

 

 

With extremely long horns, 10 feet or more, the acoustic impedance of the horn can be so high that the best results are had with no rear chamber at all.

 

I'd still seal it though.... to flatten the electrical impedance if anything else.

Link to post
Share on other sites

Hey, I finally found some logic to go with the no back chamber recommendation.

 

 

I'd still seal it though.... to flatten the electrical impedance if anything else.

This info is straight from the Build Plan. This is why i didn't install the cover.

 

"As for the lack of a cover over the access, most bass horns seal the rear chamber

to tune the cabinet response and apply restorative force to limit the excursion of the
driver. The Table Tuba horn is long enough so that the air mass of the horn alone will
tune the driver response and limit excursion. Excursion above 15Hz is unaffected by
the lack of a cover. Moreover, the open chamber is a second sound source at very low
frequencies, similar to the port of a bass reflex cab. To preserve the tuning of the
cabinet the side with the access hole should be 1½ to 2 inches away from the
boundary, be it a wall or floor. If you lay the cab on the floor use legs to lift it 1½ to 2
inches. If for some reason you cannot have the access cover side within 2 inches of a
boundary you must add a cover, or there will be a response dip around 90Hz."
 
Impedance
 
"The recommended drivers are rated at 4 ohms, but the horn loading increases
the nominal impedance to 6 ohms throughout the subwoofer pass band. The same
applies to a pair of 8 ohm drivers parallel wired. A pair of 4 ohm drivers parallel wired
gives 4 ohms nominal impedance. A pair of 4 ohm drivers series wired will give 10
ohms impedance. Dual drivers must be wired with correct polarity or they will cancel
each other out."
Link to post
Share on other sites

Nice!   That's not in my plans I purchased from him (but they were for for the Tuba HT)

 

I actually found his comment on an old forum doing a search for back chamber tuning on some upperbass horns I'm tweaking right now.

Link to post
Share on other sites


Well now......after 2 sheets of 12mm MDF, no less than 250 screws, half a bottle of Poly glue & decorative finish coat, she's ready to be fired up.

 

I hooked up the banana plugs, set the gain to zero, then slowly upped the gain control to about 1/4 - 1/3 to match my system. Sub sounded slightly out of sync, so i flicked the phase switch over to reverse....Bingo! sounds perfect. I set the crossover to around 70 - 80 hz.

 

post-122082-0-32214500-1434765931_thumb.

 

My listening chair is closest to the Sub. Now, I know having this Sub sit right next to me, is far from being an ideal position, but this is the only location i can place it & double-up its use as a coffee table. 

 

I wanted to listen to bass guitar, so..... Joe Bonamassa - Blues Deluxe album, is first off the rack.

 

post-122082-0-23291600-1434768339_thumb.

post-122082-0-99206800-1434768364_thumb.

 

Firstly i fired the horn mouth straight at the wall, beside the CD rack near the window. Sounded good, but predictably you can hear it mostly to the left side. Right then.... change the direction of fire to the rear corner behind the chair, near the door.

 

WOW...... massive difference, sounds fantastic & bass loading off the rear wall is outstanding. It's a pity i can't get it closer to the rear wall for improved loading.

 

The most impressive thing with this horn mouth direction, is that the bass just completely surrounds the listening chair, with no hint of the sound coming from my left side, very surprising & rewarding.  :eek:  :D When you put your hand on the Table Tuba, there's bugger all vibration felt with your hand, but touch the wall & door & it's a totally different story.

 

IMO, I notice straight away how accurate, tight & punchy it sounds. Bass guitar sounded so realistic & drums sound amazing. :party

 

I put on Hans Zimmer - Superman soundtrack, deluxe album & picked a few choice tracks with deep bass. The depth of bass is just wonderful & exciting, with so much attack.

 

Next up is, Yello - Touch album & again, just wonderful powerful extension of bass. Goose bump smiles all round :love  

 

I couldn't help myself and put on a Freq sweep from 100 - 10 hz, at  mid - high volume. With only my ears to measure, it certainly loads up hard at 50 - 30 hz & digs down to 25 hz very well, then at 20 hz you can't really hear much, but my door in the corner is flapping & vibrating with the air movement. Must fix this. ;)

 

This Table Tuba seems so efficient at producing effortless bass. My 250 watt amp is hardly heating up, even when i run hard at high listening levels. I put the Tuba on its side to view the sub working & was quite surprised to see the cone movement to be an estimated 4-5mm total. the driver is rated at 12.7mm extension.

 

Overall, i'm very very pleased with the outcome of the Table Tuba. It certainly has exceeded my expectations & is a wonderful addition to my system. Music sounds so warm & powerful, but most importantly for me, is the way it has surrounded my chair with accurate, rich, deep & attacking bass. :cool:

 

Cheers 

Mushroom

  • Like 1
Link to post
Share on other sites

My listening chair is closest to the Sub. Now, I know having this Sub sit right next to me, is far from being an ideal position

 

Won't matter at all.... as long as you set the levels and delay right.

Link to post
Share on other sites
Guest atilsley

Congrats...great to see another TT out there.

 

What sort of EQ are you using?

 

I have added about 7dB around 45Hz with a gentle q

 

Xover is 90Hz with 24dB slope...and I put 20Hz on bottom end with 48dB slope.

Link to post
Share on other sites
  • Recently Browsing   0 members

    No registered users viewing this page.




×
×
  • Create New...