Bill Fitzmaurice

[quote name='geoff90guitar' timestamp='1489326528' post='3256031'] It's the Neo speakers I can't get on with - they sound like meat and potatoes WITHOUT the veg. [/quote][size=8]Zombie Thread![/size] [size=8][size=4]BTW, the magnet material has nothing to do with the sound created. [/size][/size]

[quote name='Ghost_Bass' timestamp='1489063603' post='3254053'] I thought it had the other driver pointing at the bottom for sub-lows reinforcement [/quote]That's apparently how it's configured, and that's isobaric. It's a bit different than the usual arrangement, as it makes the plenum chamber connecting the drivers large, with the vented chamber small, but it's isobaric nonetheless. [quote] Isobaric with mixed sized drivers? How well is that likely to work [/quote]It won't work as well as with matched drivers, as one will run out of excursion before the other does. This is another aspect which leads me to believe the designer is lacking in the chops department.

Everything about them says 'isobaric', so while the response to size ratio will be good, the output won't be. Watts don't matter, decibels do. The manufacturer won't reveal any details about them, while their lead spokesman seems to be seriously lacking in the knowledge department. I doubt he can spell 'isobaric', let alone know what it means.

[quote name='cameltoe' timestamp='1488899616' post='3252761'] My current cab is a TC RS212 (8ohm) and I'm wondering if I will gain anything by using a 4ohm cab instead? [/quote]You'll only lose the ability to use more than one cab, unless you have a 2 ohm stable amp.

[quote name='Beer of the Bass' timestamp='1488568206' post='3250189'] a lower impedance or a short will still run the valves outside of the operating point the designer intended and cause them to limit the current passed. [/quote]It's of far less concern than no load. That's why Fender amps used a switched main speaker jack to short the output transformer secondary when there was no speaker plugged into it. As for low impedance loads, when we were young and stupid we'd run Fenders with 1 ohm loads that never bothered them a bit.

[quote name='Chienmortbb' timestamp='1488565142' post='3250134'] If you put an output transformer on an SS amp it would behave in the same way as the thermionic valve /vacuum tube amp. However why put a huge lump of metal in there is you don't need it? [/quote]That's why SS amps stopped using output transformers in the 1960s when direct coupling technology was invented.

[quote name='Beer of the Bass' timestamp='1488559026' post='3250060'] the impedance marked on the outputs or selector is the optimum load impedance for that tap, not a minimum as is common on solid state amps. [/quote]In fact, it's the maximum. The rules with valves are the opposite of SS. Valves aren't even bothered by a short circuit, but they can be toasted when there's no load.

They might also have a very different response as well as output. Play a Jazz Bass and a Gibson EB-O and they hardly seem to be the same instrument.

[quote name='28mistertee' timestamp='1488480309' post='3249361'] So it's not a problem with the cabs then? [/quote]It can be if EQ in the amp and/or an active bass is trying to get out of the speakers what they can't give.

[quote name='Dan Dare' timestamp='1488476614' post='3249315'] aren't most cabs producing mainly harmonics at those frequencies? [/quote]They are, because the bass is producing mainly harmonics at those frequencies.

[quote name='28mistertee' timestamp='1488449924' post='3248995'] Would it be possible that the mixed drivers are the problem? [/quote]The problem is that the specs you need to know are the specs that manufacturers don't reveal. One reason why they don't is that many don't know themselves how their cabs perform, that totally botched chart from Ashdown being a prime example. Manufacturers talk about inches and watts, the two least significant factors where both low frequency extension and output are concerned. Your only options are to try before you buy, or to build your own. The big advantage to building your own is that you're not buying a pig in a poke, you know what drivers are in your cabs and what they're capable of.

[quote name='markstuk' timestamp='1488399103' post='3248682'] There is a frequency plot here [url="http://ashdownmusic.com/files/product/file/datasheet_20150224063841_74985.pdf"]http://ashdownmusic....63841_74985.pdf[/url] - not sure whether it's measured or calculated... But you see the roll off from 50 Hz.. [/quote]I don't know how they arrived at that, but a bass cab with that response would be all but unusable. The black trace looks to be the raw response of a driver, measured mounted in a wall. Not a very good driver at that. The blue and red plots appear to be predicted response charts, but what they predict is a cab with no significant low frequency output. It's almost inconceivable even with a mediocre driver that the predicted response of a ported cab would be that bad, so my guess is that the charts were prepared by Ashdown's pet chimpanzee. OP, what's most important is an accurate measured response chart, at 1 watt and at full rated power. Catch 22: Virtually no one publishes them.

Sensitivity can be compensated for with EQ. The point of four drivers is low frequency capacity. Above 500Hz or so even a single ten can cover a good sized room.

Line in is for something like a CD deck. It may be OK with the keys as well, depending how much output it has.

[quote name='xgsjx' timestamp='1488205761' post='3246750'] In a 4x10, if you were to put a low pass filter on the 2 drivers at one side [/quote]It would work very well. 300Hz is lower than you'd need to go, and it would require a high cost inductor. I'd put the filter knee at 800Hz. Use a 12dB/octave filter, 6dB wouldn't be effective enough to be worthwhile. This is something the manufacturers should have been doing for the last thirty years at least, why they haven't is a head scratcher. It would be an even more useful mod with guitar cabs, but they're all stuck back in 1968.

It will probably work best on an active bass input, it it has one.

[quote name='Lozz196' timestamp='1488137677' post='3246238'] Not understanding the science that well Bill - for that read, not at all - is this why when with a horizontally arrayed cab you get a great on-stage sound that`s perfectly balanced between highs and lows, yet when you walk out into the crowd, all you hear is boomy mush? [/quote]The acoustics of the room aren't as evident close to the cab. I always set my tone and volume standing out in the crowd, if it doesn't sound good on stage I live with it. I'm there to sound good to the crowd, not to myself. [quote]I wonder if eight 6" drivers shift as much air as two 15's ? [/quote]Eight 6.5" have a total of perhaps 1,000 sq cm cone area, two 15" about 1,600 sq cm. 6.5" will likely have less excursion as well, so they're going to be well shy of a 2x15, much closer to a 2x12.

The physics are the same with any driver size. Vertically arrayed good, horizontally arrayed bad, at least as far as midrange and high frequencies are concerned.

[quote name='DanOwens' timestamp='1488134609' post='3246192'] If i can't find the specs on the speaker, what happens if I replace it with any old 10", 100w, 8Ω speaker? [/quote]Impossible to say. It may sound like utter crap, but that's pretty much a property of no-name Asian products anyway.

You've got a blown voice coil. An expert can re-cone the driver. Replacing the driver is an option, but the T/S specs and response must be the same as the original.

[quote name='Phil Adams' timestamp='1488025758' post='3245120'] Ahhh, so what they really mean is that in its current form it should deliver 250-300 watts, but it's capable of 500 if brought down to 4 ohms [/quote]That's what they mean, but it's of no consequence anyway. Output is limited by voltage swing, which is the same irrespective of the load, while sound levels are measured in decibels, and there's no direct correlation between power and decibels.

[quote name='Hippytone' timestamp='1487943727' post='3244405'] This was the reason behind the initial question regarding the "real-world" frequency point at which I'm going to start losing equal definition across the room due to comb filtering. [/quote]Comb filtering doesn't reduce dispersion. It causes uneven response across the sound field in the frequencies where the center to center distance of the drivers is more than one wavelength. With two tens that's from about 1kHz. The main issue with side by side drivers is that horizontal dispersion is inversely proportional to the width of the source, even when they are spaced close enough together to act as one larger source rather than two smaller sources. A pair of tens side by side will have horizontal dispersion similar to a twenty-one inch driver, and will be noticeable down to at least 600Hz.

Get another identical 4x10. A 1x15 won't go any lower, and it doesn't have as much output as a 4x10.

[quote name='Phil Adams' timestamp='1487845763' post='3243425'] Ive been using the 2x10 on the floor pointing forward beside the Ashdown, [/quote]That's the source of your problem: your ears aren't located behind your knees. Either get the necessary corrective surgery or stack the 2x10 vertically above the Ashdown.

IMO, get a matching 2x10, stack them vertically. Getting the upper cab close to your ears will make it easier to hear yourself, and if you don't have PA to cover the room then you probably need more than one 2x10 anyway. I can't picture where the Ashdown fits into your setup.