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speemike
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Poor Bass with new sub

I currently have a Jolida JD1701 Hybrid amplifier with LSA 0.5 bookshelf speakers hooked up to my Pure I20 ipod doc station playing apple lossless files. I recently added a known good Infinity powered 12" sub using RCA connections. This sub really put out a lot of bass in a much bigger room. Now I can turn the sub volume all the way up along with the sub filter opened up and still the bass is hardley noticible. It is as if the RCA output coming out of the amp is turned all the way down. You can also run the speaker wires into and out of the sub as a means to avoid the RCA's but I would prefer not to do it that way. Any suggestions?

I do have the RCA's connected to the variable output as opposed to the fixed on the amp. I guess I dont know where to start to fix the problem. Could it be the factory china tubes in the amp lacking bass output? This is my first hifi gear, do these systems not put out much bass?  Any suggestions?

Thanks

Mike

 

Demondog
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Does the sub have a gain

Does the sub have a gain control? Sounds like it isn't providing enough gain through the rca input. That's why most subs I'm familiar with have gain (volume) control. I doubt the amp has too low an output, but I guess it's possible.

EDIT: Read it again. Looks like you tried the volume control. I'm kind of stumped  now, though one thing I notice is that the Jolida JD 1701 specification has a lower +/-3 dB limit of 22 hZ. I don't know if that applies to the pre-out, but that's not good number for sub bass.

Kal Rubinson
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Two issues.   First,

Two issues.  

First, subwoofer positioning is critical.  If you put the sub in a site where there is a room null (or a few) in the low bass, it will be impossible to get much out of it.  Try moving it around.  Same applies to the listening position.

Second, the relative gain of the preamp out + sub amp with respect to the Jolida amp is relevant.  Try the sub on the speaker outs just to see if that applies to this situation.

jackfish
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I concur with the placement issue. Could try this...

Use the variable output jacks to connect to the sub. Put the sub in your listening position, play bass heavy program material and crawl around to find where the bass sounds the loudest. Then place your sub at that location.

speemike
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Fix

Ok so I finally got around to hooking up the speaker wires to the sub instead of the RCA cables. Well that seems to have fixed the problem as now I have to turn the sub almost all the way down. I guess the real question now is if the RCA problem is in the 12 year old sub or the new Jolida amp. My guess is its in the sub, but I am not sure how I can verify without another sub.

commsysman
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SUBWOOFER

IMO the amplifier output you are using to feed the subwoofer is probably defective or the wrong one.

Actually, I see no mention of a preout or subwoofer output jack when I look at that amplifier' s information, so I wonder what you WERE using to connect to the subwoofer.

It appears that wiring the sub to the speaker terminals was your only option in the first place.

 

speemike wrote:

Ok so I finally got around to hooking up the speaker wires to the sub instead of the RCA cables. Well that seems to have fixed the problem as now I have to turn the sub almost all the way down. I guess the real question now is if the RCA problem is in the 12 year old sub or the new Jolida amp. My guess is its in the sub, but I am not sure how I can verify without another sub.

jackfish
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The Jolida JD1701 has both fixed and variable

preamp output jacks. The variable output has a maximum voltage of 1.8 volts and is intended for connection of a power amp or powered subwoofer. That output might not be a good match for the input sensitivity of the subwoofer.

speemike
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Sub Input Properties

Thanks Jackfish you are correct. Commsysman the Jolida website is not very good and you are correct it does not list all the outputs on the website.

The sub is an Infinity BU2 which has RCA line level inputs with a sensitivity of 70mV and an impedance of 12K Ohms. Does anyone see a problem with the maximum voltage of 1.8v of the Jolida amp combined with this sub?

The sub is probably 12 years old and the RCA inputs have never been used before now. I am really not all that concerned if they dont work but at some point I would like to upgrade to a newer sub and use the RCA inputs on the new sub. So verifying the amp's RCAs work is really my concern as the amp is new and still under warranty.

Any suggestion on how I can test these to verify?

Demondog
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Up to 1.8 volts into 70mV

Up to 1.8 volts into 70mV sounds fine. I don't think the impedance is a problem either. A higher input impedance lessons the load on the pre-amp I believe. Keep in mind, the Jolida will not put out 1.8V unless its input is getting a high enough signal. But I still don't see a problem with the specs.

All I would do at this point without measuring equipment, is try the sub with a different pre-amp, and the Jolida with a different sub. It may very well be that the thing is broken.

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