JohnH89

I think we knew that . Well , you did and I believed you . Cheers Mon Ami .

A quick update for you who may be interested . Played my Yamaha BB734 through the amp for 2 hours at a rehersal tonight . Sounded great to me and compliments from other band members . Had it up way too loud and made the point it was to stress test the amp . It coped with the above plus 20 minutes or so idling between songs . A couple of quieter tunes to give the ears a rest and finished up with a full on hammering . Now here is the thing ...... No noticeable heat at all . Played with it on its side for a couple of minutes at the end , and no noticeable heat from the upper reflex port . Not even detectable above ambient temperature . I couldn't tell you if the fan even ran as it would be impossible to hear unless cabinet was dismantled . The rehersal space is centrally heated to 21 degrees (70 F) . Very pleased all round , the only possible casualties are the windows which got rattled a bit . Thank you all for your help , assistance and ideas . Any further reports or problems in the future I will post it here .

'My calculations show that with 25 degrees C ambient, a 31cm x 31cm x 31cm wood box with nominal 12mm thickness, the final temperature after "forever" (called the asymptotic limit) will be 33 degrees C with an 8 degrees C total temperature rise. This is about what I would expect worst case, pretty much trivial. Here's one handy enclosure calculator, there are several. These sorts of formulas are also used in the heating and air conditioning industry too, the walls will have a thermal resistance, and if playing in the sun there will also be heat gain due to radiation.' Cheers for that . Way beyond my comprehension but I have confidence in the design . For info , cabinet measures 395mm on each side of the cube (internal measurement ) . 2 x 75mm ports in the lower part of the rear plate . Cabinet is built from 9mm ply , laminated to 18mm across approx 65% of surface area . Baffle and rear panel from 18mm MDF . I will really try and destruction test it tomorrow . If it survives ( it will ) I will buy myself a beer . And those that have helped can have one on me . 😀 #downunderwonder . Just what is your obsession with the sideways thing ? I said I would do it just to please you . Just wait for some empirical evidence . Not long now .......

The BQ250 has a thermal cutout . Let me try a real world scenario later this week and I promise I will get back to you . To please #downunderwonder I will even turn it on its side and check the temperature of the upper port .

Because , my learned friend , I am , maybe optimistically , confident that the original design , all things considered , has a far better than even chance of being absolutely fine . If you can wait until thursday late evening or more likely Friday morning GMT , then we will know for sure . I think you may have misunderstood #agedhorse and his very well informed opinions but I will leave that between the two of you . He has quite a background in design and development of bass amplification . Be assured that I will post the results of a test and will willingly admit if my assumptions/calculations prove inaccurate .

The BQ250 is a lot bigger than the BAM200/Warwick gnome/TE Elf with better heatsinking and considerably more venting and bigger fan .

As pointed out , the case and heatsinking on the BQ250 is a lot larger than the Warwick . I have also come across the following from TC electronics Which is a 750 combo using this head Also vented from the side and a lot less airflow than the BQ250 . My money is still on the little BQ having adequate cooling .

Thanks for your concern . We'll try it out first . Two small ports at the top of the rear panel , ducted to the fan / outlet will take care of that if necessary . I'll have a virtual bet with you to see if I can get it to overheat at rehersal this week . I'll try hard 🤪

I understand your comments and concerns but am very aware of how it all works . I really don't foresee a problem but will give it a hard run at rehersal on Thursday and let you all know how it works out . I have used the head a lot in the past and even when driven hard for a long period , it barely gets warm . At approx 95% efficiency , at full power constantly of 250W (which it is nowhere near with normal playing ) it would have to dissipate a lowly 12.5W . If it turns out that there is a problem , the amp will protect itself and cut out . If it does I will design a forced cooling duct system for it . I'll keep you posted .

We'll see . I am not expecting any problems but can always add forced ducting if necessary . I have driven the amp flat out for 4 hours without the fan coming on for more than a few minutes when it was sat on top of the cab . I like the idea of it on its side as a simple solution if there is a problem .

Amp is mounted to the back board via 4 bolts and a ply pressure plate . The sides of the case are free for air to move . On the BQ250 , the fan and vent are mounted on the side of the case . With the amount of air that moves with the 12in driver , I would be very surprised if I have an overheating problem .

It does deep very well in a well designed cabinet .

A quick backstory behind this project . I use a Markbass 801 for rehersals with small acoustic folk band . I love it for its sound and form factor , a lot easier than schlepping a head , cab , cables etc . For outside performances that need more volume , I have been using a homemade 112 cab and TC electronics BQ250 . I though I would combine both ideas and made myself a bigger , louder combo , like the Markbass on steroids . The Celestion BN12 - 300S 4 ohm speaker was robbed from the cabinet , and a new cabinet made . 16in cube made from 9mm ply that was laying around , laminated in parts for strength but still remarkably lightweight . Rear ported and the TC BQ250 built in . Fitted with a DI XLR socket with a ground lift wired in . The cab was designed to be resonant at 41Hz and plugged it in this afternoon and was blown away by the volume and tone . 17.2kg - 38lb . Heavier than I thought but still lighter than the original cab that was all timber .

Dana Colley on the baritone sax

No you aren't .

All over a few ounces ? Who really gives a **** ?

Just picked up a new BB734a from the chaps at bass direct . Of all the basses I tried out , the set up from the factory and quality of manufacture are beyond compare . Across all musical instruments , Yamaha have been doing it brilliantly for years . If you want a label on your bass to impress people , buy a fender . If you want a bass to play and last for years , buy a Yamaha .

How about picking up the phone and speaking to them ? Always helpful . And its not beyond the wit of man to do the conversion yourself if you are that bothered . Just bought a bass from them and decided to go in person . Without going into details , there were problems with the bass that were nothing to do with the guys at BD . 12 hours from finding the problem to picking up new bass , strings , straploks etc . And they did a great deal for me . It's easy to criticise . They will have my business for a long while . The measure of any company is how they deal with it when things go wrong . Hats of to Mark and the chaps from a happy customer .

This is mine . Hotone nano amp as preamp . Send socket to input of DIY class D power amp . Speaker out to PJB C2 . If more volume needed , I change cab to high sensitivity 112 . Plenty loud enough . All runs from an 18v 2Ah drill battery for at least 2 hours . Probably nearer 4 but not run it out flat yet .

Had a small problem with my out of warranty briefcase a couple of months ago . Selectron were polite on the phone but not interested in anything out of warranty . They put me on to a local amp tech . All sorted but no spares used so can't tell you how easily they are available . Good luck