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Sub 35Hz speaker response


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Playing my Yamaha BB415 through my recently acquired Laney B1 (1500 watts into 4 ohms - bridged mode) into a Marshall MBC410 (4x10 + HF compression driver) I was very impressed with the clarity and the punch of the 10's but noticed a big drop-off if I played below a C on my low B.
Putting this down to the lower frequencies being beyond the spec of the 10's, I thought adding a 1x15 would improve matters. In bi-amp mode the amp will put out 750 watts per channel at 2 ohms, 550 watts at 4 ohms and 350 watts at 8 ohms. 2 ohm drivers are pretty rare so I'm looking for a 4 ohm 15" driver that can handle around 750 watts but I'm struggling to find a suitable driver for the job.
Also looking at the specs of the Eminence and Celestion drivers, I notice that the usable ranges don't seem to go below 35Hz, still not low enough for a low B which is about 31Hz. I've no idea how ERB owners get on with their low F#'s
Can anyone help me out?

Cheers
Mark

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[quote name='bassman2790' post='137464' date='Feb 10 2008, 09:08 AM']Playing my Yamaha BB415 through my recently acquired Laney B1 (1500 watts into 4 ohms - bridged mode) into a Marshall MBC410 (4x10 + HF compression driver) I was very impressed with the clarity and the punch of the 10's but noticed a big drop-off if I played below a C on my low B.
Putting this down to the lower frequencies being beyond the spec of the 10's, I thought adding a 1x15 would improve matters. In bi-amp mode the amp will put out 750 watts per channel at 2 ohms, 550 watts at 4 ohms and 350 watts at 8 ohms. 2 ohm drivers are pretty rare so I'm looking for a 4 ohm 15" driver that can handle around 750 watts but I'm struggling to find a suitable driver for the job.
Also looking at the specs of the Eminence and Celestion drivers, I notice that the usable ranges don't seem to go below 35Hz, still not low enough for a low B which is about 31Hz. I've no idea how ERB owners get on with their low F#'s
Can anyone help me out?

Cheers
Mark[/quote]

The problem is not that your cab is poor at reproducing the fundamental of the lowest notes but is that it is also down in response at the 2nd harmonic or these low notes, i.e. in the <70Hz region. With a typical bass the attack phase of the note is roughly equal parts fundamental and 2nd harmonic (1st overtone) and the sustain phase is predominantly 2nd harmonic. The shorter the scale length and the less rigid the neck structure, the less loud the fundamental is, particularly in sustain.

ERB owners get on with low F# because the bulk of the musical content of the note is above 50Hz.

Here's an enlightening measured plot of an Avatar 4x10" neo cab - maybe a cheap 4x10" but it actually contains better speakers than most name brands:



Note how the response is dropping by 100Hz. This is the same for the vast majority of 10" cabs, Acme excepted. 15" loaded cabs are rarely better because they have insufficient internal volume for the speaker to operate efficiently.

The other problem you're coming up against is that even if your cab had good response down to low B fundamental, your speakers would have insufficient travel to move enough air to get loud enough, hence the choked response as they run out of excursion and into excursion related power compression.

Alex

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That's really useful information Alex, thanks. The question is how do I solve the problem? Judging by the information you've kindly supplied, if I had a cab where the roll-off didn't start until about 50-60Hz, I should notice a difference in the 2nd harmonic. Is there anywhere where I can find the specs of mass produced cabs? Or a guide to how I could make a 1x15 cabinet that performed well down to 50Hz?

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[quote name='bassman2790' post='137518' date='Feb 10 2008, 11:35 AM']That's really useful information Alex, thanks. The question is how do I solve the problem? Judging by the information you've kindly supplied, if I had a cab where the roll-off didn't start until about 50-60Hz, I should notice a difference in the 2nd harmonic. Is there anywhere where I can find the specs of mass produced cabs? Or a guide to how I could make a 1x15 cabinet that performed well down to 50Hz?[/quote]
If you think you can make a cab, Bill Fitzmaurice designs will probable have something to suit. I'd recommend you consider the Omni 15 as a simple build which will do what you want.
[url="http://www.billfitzmaurice.com/Omni15.html"]http://www.billfitzmaurice.com/Omni15.html[/url]
I am taking an Omni 12 to the north west bass bash in March if you can wait that long.

Edited by Mottlefeeder
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I had one of these for a while, paired with my Mesa 400+ it had the most immense bottom end - though it required a lot of power and weighed quite a lot.

[url="http://www.bassonsound.com/b210b.htm"]http://www.bassonsound.com/b210b.htm[/url]

ped

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[quote name='bassman2790' post='137518' date='Feb 10 2008, 11:35 AM']That's really useful information Alex, thanks. The question is how do I solve the problem? Judging by the information you've kindly supplied, if I had a cab where the roll-off didn't start until about 50-60Hz, I should notice a difference in the 2nd harmonic. Is there anywhere where I can find the specs of mass produced cabs? Or a guide to how I could make a 1x15 cabinet that performed well down to 50Hz?[/quote]

The aforementioned Acmes do a fine job of output down to 31Hz at the expense of sensitivity. As you have plenty of power that would be a great route for you - a single Low-B4 would be a righteous rig with 1500W from your Laney into it. Alternatively a pair of Low-B2s for a modular solution.

Alternatively a higher sensitivity route that gives up the frequency extremes but produces good output from 40-6000Hz would be the 3015LF/6ND410 cab I'm building. Once I've done one for me I'm going to work out a passive crossover version but as you can biamp it my existing design would work great with your B1. The trade-off is that as you're biamping into an 8 ohm load instead of bridging into a 4 ohm load your amp produces ~6dB less power so the sensitivity gain by losing the last half octave of response doesn't actually get you any more max SPL. Add a second cab with another woofer and you do gain an advantage. The Dr Bass cabs that Robbie's importing are available with the 3015LF but make sure they have sufficient internal volume - any less than 100 litres once port, bracing and drivers have been subtracted and you're hamstringing yourself.

Personally I'm not keen on the Basson approach, they strike me as designed by the marketing department, not engineers - heavy magnets, low port tuning and stupidly heavy cabinets looks impressive on paper but gives mediocre bass response where you really need it, though extension is certainly deep - lots of rumble but not a lot of fullness - and what is the point of a 2x10" that's as big and heavy as a well designed 4x10"?

Alex

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[quote name='ped' post='137570' date='Feb 10 2008, 08:25 AM']Alex, I got the 210 because it was really cheap. I thought it sounded great - maybe it doesn't on paper, but where it matters it sounded really full and rich. It was supremely heavy though![/quote]
And extremely power hungry. Basson makes a big deal about how large their magnets are and how much power they handle, which makes for good ad copy but not necessarily for a good speaker. Extremely large magnets result in lessened bass response. You end up with a cab that's twice the weight and requires four times the power to drive it than other cabs.
To the OP, the 150 watt ratings of the MBC 410 drivers indicate that they're at the opposite end of the spectrum, probably entry level in quality, and chances are that cab doesn't do much below 70Hz. You don't need a cab that goes below 35Hz, but you do need one that's flat to at least 50 Hz. Unfortunately no manufacturer publishes accurate specs, so the only way to find out what works best is to try some along with your top. If your head has bi-amp capability and a built in crossover try it bi-amped with the crossover set around 125-150 Hz, using a 15" PA subwoofer cab.

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[quote name='alexclaber' post='137562' date='Feb 10 2008, 01:14 PM']The aforementioned Acmes do a fine job of output down to 31Hz at the expense of sensitivity. As you have plenty of power that would be a great route for you - a single Low-B4 would be a righteous rig with 1500W from your Laney into it. Alternatively a pair of Low-B2s for a modular solution.

Alex[/quote]

The Low-B4 or B4W would seem to be just what I'm looking for. Is there a distributor in the UK or would I have to import one?

Mark

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[quote name='bassman2790' post='137631' date='Feb 10 2008, 03:44 PM']The Low-B4 or B4W would seem to be just what I'm looking for. Is there a distributor in the UK or would I have to import one?[/quote]

No UK distributor but very straight forward buying direct, just figure 1.9 USD to GBP and then add about 25% to the cost (including shipping) to account for import duties. The small extra cost of the B4 over the B4W gets you a really nice mid and tweeter with an excellent crossover and protection circuitry and if you want to use it with another cab just to add bottom, simply turn the attenuators down. 99% of the time I suspect that one cab on its own will be enough, they are LOUD!

Alex

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[quote name='ped' post='137570' date='Feb 10 2008, 01:25 PM']Alex, I got the 210 because it was really cheap. I thought it sounded great - maybe it doesn't on paper, but where it matters it sounded really full and rich.[/quote]

Cheap is always good! Regarding the sound it's like using a Lotus Elise vs an AMG CL to achieve a certain lap time - both will probably get round the track in a similar time and both be good fun doing so, but one is an elegant and efficient solution whilst the other is impressive on paper but a messy combination of huge power vs huge weight.

Alex

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