Bill Fitzmaurice

[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.

Put the 2x10 extension vertical atop the combo. The difference between the dispersion of two vertical versus two horizontal drivers is a simple equation, it's doubled.

This is why you take it to a local repairman.

It can be done, but these make more sense: https://www.amazon.com/AP2BS-amPlug-Bass-Guitar-Headphone/dp/B00NAUKJTY

http://www.fullcompass.com/brand/AMP_Ampeg/Replacement-Service-Parts.html

[quote name='Greg.Bassman' timestamp='1487447995' post='3239927'] [size=4][font=arial,helvetica,sans-serif][color=#000000]what happens if they are both the same power?[/color][/font][/size][/quote]The end of civilization as we know it. The actual preferred range for amp to cab power is anywhere between 1:2 and 2:1.

Speaker short circuit failures are rare. When a voice coil gets toasted it usually results in an open circuit. The usual reason for a short circuit is failure of the speaker cable. I'd check the cable and the interior wiring of the speaker.

[quote name='The Shrek' timestamp='1487261647' post='3238472'] The positive here out of this mess, is the experience I have gained on "how not to build a cab" ....... [/quote]We all go through that stage. A surprising percentage of commercial sources still haven't emerged from it.

[quote name='Beer of the Bass' timestamp='1487171301' post='3237744'] I don't know if I'm being spectacularly obtuse here, but would you care to go into your thinking behind that? [/quote]IMO the difference between the two doesn't justify the added complexity of porting. If he had 60L net per driver it would be a different story.

[quote name='Beer of the Bass' timestamp='1487155110' post='3237522'] Just to play devil's advocate here, is the BP102 really such a disaster in this cab? [/quote]It's not what it could be. The reason one would use a driver with the specs of the BP102 is to dig deeper than what the average driver will do, and that would seem to be the OPs intent, but in a box that's way too small it can't deliver on that promise. At this stage I would not port it.

[quote name='Gottastopbuyinggear' timestamp='1487102554' post='3237183'] I've not found a speaker that models anywhere near that in WinISD. Is there some sort of magic involved in the drivers that Ampeg put in these cabinets? [/quote]Model the Eminence Alpha 10, or B810. The cab will also need a fair amount of damping to get the Qtc down. They're not identical to the Ampeg driver, but they're close. They have high Qes, not good for ported, but fine for sealed. And they're cheap, with small magnets. That's why they have high Qes. [quote]I thought this size of cab would be nice and compact and I based in on the size of a previous little Hartke 2x10 I previously owned. [/quote]The driver specs of the Hartke would have been different. The driver size alone doesn't dictate the required cab size.