stevie

The impression I had when I switched my 450 on for the first time was that it was not as 'full' in the bass as my Trace Elliot 300, but went lower. This is in fact the opposite of what is happening, judging by the test results. My subjective impression was complicated by the fact that there is a bad resonance at 50Hz in many places in my practice room although, interestingly, that is now no longer a problem.

[quote name='paulbass' post='1329366' date='Aug 5 2011, 10:59 PM']Hi Sam, i have taken it to a tech who has a very good reputation and he simply cant find whats causing the fault.He has replaced many parts and it still doesnt work and he still cant understand what has actually gone wrong with it.He has had it for 6 weeks and i'm now at a point where i'm considering writing it off as he has said the repair bill will be very expensive.He too has contacted Trace Elliot and they told him they couldnt help him either.[/quote] I would be tempted to wonder whether your tech really knows what he's doing. Why don't you contact Trace Elliot yourself and explain the situation?

Yes, I liked it too. Carry on!

As long as you realize the LF section of the crossover is seeing a different impedance in each diagram. In figure 1 it's seeing 8 ohms and in figure 2 it's seeing 4 ohms. The simple solution is just to use a crossover on the brightbox and to let the bass end roll off naturally. I assume that's what Trace Elliot did, although I've not seen their x-over circuit for the Bright Box.

I was almost right!

As long as you use a crossover in front of the bright box of tweeter, the impedance shouldn't be a problem.

As long as the cone isn't shredded, a competent repair should last as long as the cone. Google for cone repair techniques using tissue paper and glue. There's nothing wrong with fitting new drivers, but if you are looking for a genuine improvement over the original Trace drivers you need to be looking at something like top of the range Celestions or one of the Italian brands like B&C or 18sound.

He's taken it back and smashed it over the seller's head. That's what I would have done too.

And I was agreeing with you.

I think the issue Alex was referring to, and which was also pointed out by the reviewer, is whether TC should be calling this a 450-watt amp when it isn't. Fit a turbocharger to a 1600cc engine and it's still a 1600cc engine. Just because it performs like everybody else's 3-liter engine doesn't mean you can claim it is one. Not that TC is alone here, as virtually all bass amp manufacturers exaggerate the power output of their products. How TC get this performance out of the amp is certainly interesting and I didn't have time to read the fairly complex technical explanation in the magazine. I'm not sure I would have understood it anyway. My superficial understanding is that it is down to compression. They are also reducing the level of the lowest fundamentals of the bass and compensating with a boost slightly higher, which I would imagine will also help. If people are happy with the amp, as they certainly seem to be, perhaps it is nitpicking to criticize.

[quote name='Musicman20' post='1325526' date='Aug 3 2011, 12:30 PM']Very good online magazine.[/quote] I agree. It's how it should be done IMO.

[quote name='markstuk' post='1325486' date='Aug 3 2011, 12:01 PM']Not seen the article - what was the "specmanship" TC are playing with the RH450?[/quote] From memory, they measured the output for 2.5% distortion at something like 180 watts. There's a bit more to it than that, which I'm sure Alex will be happy to explain.

Yes, I read the TC review this morning. It probably raises more questions than it answers. How many watts? And I wish I hadn't seen what they have done to the low-end frequency response, which explains the difference I heard when I compared mine to my Trace Elliot head. Despite being listed as 10 or 11 ohms or so in the technical specs, the speakers look just like normal 8-ohm ones as far as one can tell from the graphs. Shame they didn't test the amp down to 2 ohms. Nicely done review though.

[quote name='Mr. Foxen' post='1323591' date='Aug 1 2011, 09:48 PM']BFM is qualified as far as In know, even if he doesn't have the paper, he has the knowledge, even if he is a bit 'attitude' about it.[/quote] We all have a soft spot for the gifted amateur, but an ‘acoustical engineer’ is not some honorary engineering title like a British Telecoms engineer or a FOH engineer: it is a recognized job description requiring a BSc or MSc degree or equivalent in physics or engineering plus several years of practical experience. (Look up the job ads). An MEng Acoustical Engineering, which you can study for at Southampton, will get you Chartered Engineer status (Professional Engineer in the US and Canada). In most countries, including the US as far as I can tell, you then need to pass a licensing exam to practice. Which is not surprising, as these guys can act as expert witnesses in court.

[quote name='Bill Fitzmaurice' post='1323280' date='Aug 1 2011, 05:13 PM']If you've got nothing better to do than argue about the audibility of group delay got to DIYaudio and waste a few dozen pages in debate with Earl Geddes.[/quote] Lawrence isn't arguing about group delay: he's describing current thinking on the subject. There certainly are quite a few "real" acoustical engineers who admit they don't have a definitive answer to this one, Linkwitz and O'Tool included. You're the one insisting you have the answer. If you have some information, please share it. It is a rather arrogant to tell another forum member to go elsewhere to discuss a topic. It's the equivalent of telling somebody to shut up. Why don't you go to DIY audio and talk with Dr. Geddes yourself - I believe he has done recent some work on group delay audibility. Oh, I forgot - that's one of the forums you're banned from isn't it? Shame.

Sounds like you're sorted. Now go and enjoy the women! Edit: and the food, of course.

[quote name='DirkThrust' post='1321296' date='Jul 30 2011, 01:45 PM']Ashdown quote an extra 23Hz of lowend for the MAG115 below the 4x10 so in theory the cab will produce 27Hz if the user were so inclined, but all I've found extreme low end to be useful for is creating lots of boom and window rattle and ensuring that I spend half the gig trying to EQ it out.[/quote] I have to agree with Bill: Ashown's figures are pure fantasy. I've tested the driver in that box, measured its Thiel Small parameters and published its low end performance in an Ashdown cabinet on this forum. It has no low end to speak of - by which I mean below 100Hz - and it has a bad peak at around 100Hz, which is no doubt the boom that you were trying to get rid of. The MAG 15 may well be the cheapest 1x15 on the market, and it shows. If you were looking to add low end to a 4x10, it's not surprising you failed.

[quote name='Bill Fitzmaurice' post='1321310' date='Jul 30 2011, 02:09 PM']One of the laws of acoustical engineering is that power demand doubles for each octave of lower frequency extension. That being the case the notion that a single fifteen driven with the same power as four tens can significantly add to the low end just doesn't add up.[/quote] Bill, I just love the way you keep quoting the laws of acoustical engineering and then slipping in a non sequitur. Nobody does it better - really. However, if you add another cabinet to a 4x10 that is more sensitive in the low end (quite easy to engineer with a bass driver like an Eminence 3015LF), you will add considerably to the low end. Plain and simple.

That's a very good point.

[quote name='xgsjx' post='1320986' date='Jul 30 2011, 12:30 AM']In the OPs case, if he likes the sound of his 4x10 & wants more of the same, then an Ashdown 4x10 would be as close to getting that. Adding a 15" to it alters the sound (as you know, with varying results).[/quote] From what the OP has said, I’m not sure he wants more of the same: it sounds like he wants deeper lows. Adding another 4x10 won’t make any difference to the low-end extension. The only way of getting that is adding a cab that goes deep. I've no way of knowing whether the Peavy 15 will do that or whether it will be compatible. But it might, and I wouldn't discount it without trying it out first. Especially as money is tight.

Yes, I missed that particular contre-temps. Still, this forum is remarkable civilized most times given the number of people, and opinions, on here.

Bought a rack from Ben for a very reasonable price. Delivery and communication were first class. A number 1 basschatter.