Phil Starr

It's always interesting to look at specs but I don't thnk you can reliably compare between brands. Firstly the power ratings are for the amps not the speakers. You can put a 2,000W amp into a speaker but if the power is then managed by DSP then the speaker is protected from that power ever reaching the speaker. There really aren't many 15" speakers that can handle anything like that sort of power. To do that over long periods you need plenty of coil area to dissipate the heat so bigger voice coils are needed. Reckon 4-600W for a 3" voice coil and 600-1,000 for a 4" voice coil. Typically sensitivity of a mid priced 15" speaker with a 4" voice coil will be arond 96db /W so at 1,000w that is 126db maximum output. Looking at the RCF drivers they are over quoting by 6db at least, I know this because they also sell the speakers as bare drive units. At one point Yamaha were over quoting by 9db. I wouldn't even like to say from your pdf which of those speakers would be the loudest in practice. Be careful about basing your decision upon specs. It would be great if you could try those 12" EV's. It's so hard to get to listen to any of this gear even in London. it might be worth trying some of the DJ dealers but borrowing gear is always better as you can set it up the way you want. As to reviews: most people are in love with the kit they just bought, will highly recommend it but mysteriously upgrade a year later . It's all a bit of a leap in the dark. Having said that none of these brands are making bad kit, RCF and Yamaha are at the top of their game I've probably been looking at the same on line reviews of the lates offerings from EV and they are looking good. I just haven't heard their latest stuff live yet so I've no opinion. I wasn't really recommending the RCF 905 btw. I was just trying to answer your two 12's or one 15 question. I have the 905, its a good sub but i have no idea if something else would be better/as good.

I can't answer that it all depends upon where you are going to use them and how they are used. There's no reason why they shouldn't sound the same at low sound levels. However making loud bass is af everything else is equal question of shifting lots of air and a big piston will outperform a little one if everything else is equal. Thats about cone area so you can work it out . Roughly thats 250cm^2 for an 8, 530 for a 12 and 850 for a 15. That's comparing like with like. The rcf 702 gives 129db, the 705 gives 131db and the 905 133db in their spec sheets. You'd have to decide for yourself whether the extra 2db or 4db would be needed. Remembering also that 2x 12" 702's are £1470 and 1x 905 is £1150. The 12's weigh in at 42kg and the 905 at 31kg so tht is a factor too. I doubt that in practice a single 12" sub would outperform the 12" speakers in your ART 932's, so I think only a pair of 12's make sense

So Santa brought me one of these little mixers. I've a little Alesis mixer that sits on my desk to drive my studio monitors and practice headphones. It has USB and I've used it as an interface but the quality is just not great, it's noisy and the mic pre's are really quite poor. Some of the pots need a clean too. So initial impressions: It is nicely made, solid case and all the pots are smooth with a nice feel, everything works as it should. Set up took a time, the handbook isn't much help and the only video's I found on YouTube weren't much help either. In the end once you've downloaded the drivers and the Flow app it starts to work. My iPhone worked out of the box but the IPad didn't recognise the mixer for a while and the windows desktop needed extra downloads. The bluetooth conections were problemmatic as most people have reported. It took me a couple of hours to get everything working as it should. The Alesis just kicked itself into action years ago but it's mainly analogue. The mic pre's are nice, at tleast on the two dedicated mic channels. It does have high impedance inputs ( I should have read the manual before asking Santa) on channels 6 and 8 so may do as a backup for my duo. The bluetooth is a problem, it took a while to pair the control app (the playback connection was better behaved) but playing bluetooth through the Flow 8 shows just how poor the sound is, very lacking in bass and over bright at the top. Playing music through the USB port though is great. Hopefully the D/A works well in both directions. The app control is pretty crude compared with my band mixer. Workflow is simple enough but the options limited and I've spent a lot of time pressing odd bits of the screen to find out how to unlock the next screen, there isn't a lot of consistency when switching screens. It's an odd little beast really, you can only access basic operations from the controls on the mixer and the fx are really modest compared with a 'proper' digital mixer. However there are physical sliders, Channel eq is better than most analogue mixers, you do have at least two decent mic pre's and all the basic functions I need are available to me including recording multiple channels onto a DAW rather than just the two I had available previously. All this in a tiny footprint and at a pretty tiny price. I'll do a proper review once I've used this for a couple of months

Hi Al, I wouldn't worry about this, though as ever real world experience counts for a lot so I'd always respect anyone who has tried both. I think in your position you need to be looking for quality and practicality, you have great tops so don't cut corners with your sub(s). From the looks of your videos your band should make decent money so cost shouldn't be too much of an issue. I have a pair of Wharfedale EVP 15" subs. Old, heavy and reliable but they onle get used once a year on average. In smaller venues they are a liability, sonically and space wise. Last year I picked up a nearly new RCF 905 AS Mk3 and its rated output matches that of the pair of Wharfedales. I've done small outdoor festivals with those so that's as capable as I'll ever want to be. Indoors I don't think I'll ever need more. A mates soul/funk function band are going round with a pair of 2x8 FBT subs and they sound great so size isn't everything especially with that sort of music, which is close to that which you and I play. I'll add a second 905 probably if I see one going cheap but that will be for the look and the odd outdoor gig. I don't think I'll ever need it but is would give me the opportunity to run cardioid subs, if I ever get the space to set that up. I don't think you'll ever need it but you could run with a single decent 15" sub for quite a while and then judge if you need a second. Your tops are rated 133db and the AS905's are rated the same you could go to the RCF8003's which are rated 135db to match both your tops with a single cab but at the expense of a 43kg lift and an extra £500. That's the same as my Wharfedales and they are quite a carry, one of the main reasons I upgraded. So the only reason for going for 2x12's is to get the 'look' of a sub each side and a lighter carry. The look is important to a function band though. A pair of 12's is going to give you plenty of output but so is a 15 of the same quality. It's going to cost you more and may or may not be more convenient to transport. Basically I'm saying don't base your choice on speaker size. Look at the spec's but be very sceptical of them, the specs are advertising not technical measurements in most cases but they help within a brand for comparisons. Each brand exaggerates but by a fixed amount. Look at functionality, quality gear from the likes of RCF, FBT and Yamaha aren't going to let you down.

It's probably worth knowing that Celestion measure their Xmax differently to most other manufacturers so the 'true' level of excursion for comparison with other brands will be something comfortably above the 4mm they quote. Xmax isn't a hard limit, the speaker will go on producing an output without endangering itself beyond Xmax. The magnetic field extends beyond the magnet but weakens as you get further from the magnet. For the speaker this mens that the speaker begins to struggle to follow the signal accurately and it starts to distort. Xmax is an attempt to put a number on the linear part of the speaker's output. At the frequencies we are talking about, below 100Hz, you probably wouldn't notice 10% distortion. The old fashioned and harshest way of measuring Xmax is just to measure the voice coil and magnet gap; 16mm and 8mm in the case of this Celestion. That leaves 8mm of movement with the coil inside the complete 8mm gap and Xmax of 4mm each way. The other ways of quoting Xmax are to measure it at a specified distortion (often 10%) or to do a 'predicted' Xmax based upon the speaker's geometry, adding a bit of extra Xmax to allow for the extra bit of magnetic field beyond the gap. Both these figures will add excursion and to be fair will reflect real world behaviour. You can guess that marketing prefer a bigger figure. 18-Sound don't have details of how their Xmax is measured on the data sheet but I supect it is calculated with a bit extra and more generously rated than Celestions.

Well Santa brought me the set of ‘Holmer’ nut files. I’ll practice on some suitable material before risking my real nuts😅

Welcome to BassChat

happy christmas to you too Rob

I'm really sorry to hear that too. I hope she recovers quickly.

We will have to agree to differ on this Bill. You can see the frequency irregularities around the crossover point in pretty much any frequency plot I've ever seen or measured and the irregularities are audible as well as measurable. Without wanting to get into a philosophical debate about the nature of reality IMO if something is measurable and audible it is real. There's no doubt the software is getting better and will get better still but again IMO it isn't there yet. The measured plots still don't exactly match the computer's modelled responses and most of the big designers are going to use the software to get in the ball park and still use iterative measurements to check and hone their designs. Again I suppose it depends upon what you mean by "an exact result" it may be good enough but I'm a scientist not an engineer so exact is a very big statement.

It's looking really good Rob, don't do yourself down. There are two issues with the grille. You need to keep it flat and not let it rattle and then it needs to be removable for any maintenance. If the back is stuck on then the speaker hole is the only way back in. It's fairly conventional to use either velcro or the little neo magnets to hold something to the speaker. I'm not sure how well the magnets would work to just hold the grille rigidly in place. If you drop the speakr or somebody kicks it then it will get pushed towards the speaker it is meant to be protecting. I cerainly don't think just magnets in the corners would be enough, and would it rattle at higher sound levels. I'd probably want the grille screwed to a frame which supports the grille along the whole length. Use the magnets to fix the frame to the baffle. Or you could print some sort of peg system to lock the frame to the baffle.

You cut up the car! 🤣 Try using a bit of timber or hard plastic to concentrate the forces. You can then concentrate on the actually bent bits.

That's a great question and what your measurements have uncovered is one of the problems that have cursed speaker design generally and crossover design in particular since they were invented. If not really a secret it is something buried inside any speaker with different speakers handling different parts of the frequency spectrum. It's approaching impossible to have the two speakers in phase at the crossover point and it is practically extremely difficult with a passive crossover to get the roll off of each speaker to be symmetrical. Inductors and capacitors induce their own phase shifts too so time alignment of two speakers at crossover is still really difficult. https://www.learnabout-electronics.org/ac_theory/ac_ccts_51.php Bill has pointed you to the Altec "Voice Of The Theatre" A7 which is a really interesting design. Large installed systems of the time frequently had horns mounted on a sled. Active crossovers and DSP allow delay to be brought into the crossovers hence the rash of 'Firphase' into PA speakers, this is the problem it is addressing. Practically then you can pretty much always see a frequency anomoly at crossover. the designer has the choice of a blip or a dip and crossover distortion is audible in critical listening tests. Usually it shows up quite clearly and affects female voices in particular. We are really sensitive to any change in voices and the frequency of crssover is usually well within the range of female voices. Practically a dip at crossover is usually less obtrusive than a blip. Try reversing the wiring and you should see a change in your measurements and hear differences in voices and instruments in that area. Acoustic guitar often changes too but I use classical music for testing this sort of thing. Even tiny changes in a crossover can make an instrument pop out in a recording. You can choose your distortion mostly I prefer the dip. @stevie is the expert in this and the detail he goes into with his crossovers is extraordinary. It's really worth getting hold of a copy of the Loudspeaker Design Cookbook by Vance Dickason if you want to read up on all this, and much more.

Not very helpfully it took around 15mins, so I'm not sure what is going wrong. I've bashed a lot of metal in the past when I welded my own car bodywork amnd I've dressed a lot of lead when working on the roof so I'm probably fairly efficient. You kind of settle into a nice steady rhythm keeping the work moving. I'm trying hard to picture what you might be doing. I look not for the high spots but the bits where the metal is most bent. Are you perhaps going for the middle. The bent bit is around the cicumference around 2-3cm in from the edge (roughly, I dont have it in front of me). Knock these flat and the centre will start to lay flat. Push the middle down without taking out the edges will just mean it springs back.

Sorry I should probably have offered a bit more advice. If you aren't used to metal bashing steel is really forgiving but you can stretch it and even bruise it if you are too rough. use a soft faced hammer in this instance and keep the hammer square to the work. Swinging in an arc will mean you are beating with the edge of the hammer concentrating the force on the edge instead of spreading it. Find a flat rigid surface supported so it wont move or bend. The idea is to 'push' the metal down onto this surface. I found that I could simply push the sheet flat with my hands to start with. That takes out the convex curve but leaves the edges which have a more distinct fold in them. Turn the grille upside down and start to adress that. Use gentle blows with a soft hammer and remember you are trying to push it into shape so you can go gently and use repeated blows rather than trying to knock the hell out of it. Work steadily around the piece. You'll now find bits that were up are now down so you'll need to flip the grille again and try from the other side and it will gradually get flatter. The other thing to note is that beating the metal heats it slightly so lots of repeated blows will soften it, slowly working your way around means you'll find the metal starts doing what you want. I find it quite therapeutic That makes it all sound a bit complicated, it isn't. Just work steadily and it's a job of a few minutes