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Old 30th November 2011, 07:04 PM   #1
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Default Adding bass to existing system?

Hi,

I would like to add bass and sub-bass to my existing system. I actually use some loudspeakers that sounds uber good to me and I want to keep those. They're Lotus Live-208. They're 25 years old and have been refoamed twice since then.

They sound so good that I absolutely don't want to throw them. They just lack low-end efficiency. They're bass-reflex, using a 8" paper fiber woofer along with a small round horn tweeter. They're rated at 100W RMS each.

I wonder if I could build one cabinet for each channel that would take care of the bass and sub-bass portion of the spectrum.

That cabinet will hold a x-over with a cutover frequency of around 80-120HZ (2nd order?). The Lotus loudspeakers would be connected to the high-pass of that x-over as well to prevent the bass and sub-bass to be sent there.

I have restrictions of width and height, but not for depth of cabinet. The width would probably limit the speaker size to 8", so I was thinking of putting two 8" paper or paper-fiber subs per side. Closed box, vented box, i still don't know yet as I'm only at the level of getting ideas.

My amp can actually handle very tough-to-tame impedances, but I would like to stay above 4ohms per side total (6ohms would be perfect), so putting two 8ohms, 75W drivers in serie per cabinet then parallelling this cabinet with my existing boxes sounds good to me.

I absolutely don't want to add a single self-amplified subwoofer.

Am I totally wrong or can this work out? I cannot find any information on my actual boxes, they're probably too old and have been produced in too small a scale.

I'm joining a small drawing to show what I mean.

Your comments are welcome.

Martin.
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Old 30th November 2011, 08:04 PM   #2
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Quote:
Originally Posted by canonnica View Post
I wonder if I could build one cabinet for each channel that would take care of the bass and sub-bass portion of the spectrum.

I absolutely don't want to add a single self-amplified subwoofer.

Am I totally wrong or can this work out? I cannot find any information on my actual boxes, they're probably too old and have been produced in too small a scale.
Boxes are quite simple compared to making good sounding passive sub crossovers.
What you want to do can be done, but it can be done cheaper, easier and will sound better doing it with self-amplified subwoofer (s).
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Old 30th November 2011, 09:15 PM   #3
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You'll need some way to delay the tops, so running everything off one amp won't work if you want SQ.
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Old 30th November 2011, 10:43 PM   #4
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Originally Posted by revboden View Post
You'll need some way to delay the tops, so running everything off one amp won't work if you want SQ.
I doubt that the OP's top cabinets would be 1/4 wavelength off in time from front loaded subs at 100 Hz.
If the top cabinet's ports were sealed, time would be a non issue.
The components and design for a passive crossover needed to do a 100 Hz crossover are a big sound quality issue.
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Old 30th November 2011, 10:50 PM   #5
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Originally Posted by weltersys View Post
What you want to do can be done, but it can be done cheaper, easier and will sound better doing it with self-amplified subwoofer (s).
i´m doing just that. sealed boxes crossed to active sub at 80hz , jbl e250p.bass is amazingly tight, mids are controlled and clean , couldn´t be happyer.
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Old 30th November 2011, 11:58 PM   #6
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Originally Posted by weltersys View Post
I doubt that the OP's top cabinets would be 1/4 wavelength off in time from front loaded subs at 100 Hz.
If the top cabinet's ports were sealed, time would be a non issue.
The components and design for a passive crossover needed to do a 100 Hz crossover are a big sound quality issue.
Hey Art,
That's true, a perfect fourth order XO would alleviate any time issues if he plugged the ports. I was commenting because the OP said he liked them so much and they were ported.

much respect
rev.


Last edited by revboden; 1st December 2011 at 12:01 AM.
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Old 1st December 2011, 07:11 AM   #7
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Problem with a passive crossover is it has to deal with the impedance peaks of the driver. A ported box has two impedance peaks, one above and one below port tuning.

Take my word for it that this will screw up any passive crossover you care to connect.

In fact, here's some reading for you...
Active Vs. Passive Crossovers
Passive Crossover Network Design

Good luck

Chris (who uses active crossovers)
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Old 1st December 2011, 12:23 PM   #8
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Thanks for the replies... Well, if I want to avoid bi-amping, it seems that I have no choice but to build myself a new enclosure that would fit my needs and throw my existing ones... or move them to another part of the house.

Or I get some good ones from consumer market, but I'm afraid it will cost me 2 grands to get what I need...

Based on some readings and research, the MagnaCumLaude would give me the kind of brutality i'm looking for, but they seem big and I worry about possible lack of finesse.

Martin.
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Old 1st December 2011, 03:50 PM   #9
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Quote:
Originally Posted by canonnica View Post
Thanks for the replies... Well, if I want to avoid bi-amping, it seems that I have no choice but to build myself a new enclosure that would fit my needs and throw my existing ones... or move them to another part of the house.

Or I get some good ones from consumer market, but I'm afraid it will cost me 2 grands to get what I need...

Based on some readings and research, the MagnaCumLaude would give me the kind of brutality i'm looking for, but they seem big and I worry about possible lack of finesse.

Martin.
Could you try experimenting with the length of the port, stuffing/lining the box?
A larger cabinet with a low-tuned port will give an extended bass shelf output, where the severe roll-off below port tuning is preceeded by a much shallower rolloff, due to the large cabinet.
Room gain will, I expect, help to fill in this gentle slope, so you'd get more bass extension at the expense of a larger cabinet.
You'd be able to use your existing crossover and drivers.

Chris
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