My Three Sons - two front & one down - sealed - Page 6 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #51 of 66 Old 11-28-07, 09:31 PM
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Re: My Three Sons - two front & one down

Have you measured with an SPL meter instead of just by ear? If you're running the subs by themselves, you may be getting more output than you think, especially if it's flatter and less distorted than the AR you're using for comparison.

If I'm understanding that spec sheet correctly, you only need 1.5ish volts to drive the Yamaha to full output. Every modern receiver I've seen measured by S&V was capable of at least 6ish volts on the sub out so I doubt drive level is the culprit.

How are the subs wired to present their load to the amp? Have you double checked polarity at the terminals with a battery? Are the attenuators on the 2500 maxed? What's the sub out on the receiver?

-Brent
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post #52 of 66 Old 11-28-07, 10:10 PM Thread Starter
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Re: My Three Sons - two front & one down

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If I'm understanding that spec sheet correctly, you only need 1.5ish volts to drive the Yamaha to full output. Every modern receiver I've seen measured by S&V was capable of at least 6ish volts on the sub out so I doubt drive level is the culprit.
Brent, where did you get 1.5ish volts. I'm looking for it and just noticed that near the bottom it say 0 DBu = 0.775 Vrms. Further up it says the P2500 wants a signal of +3 DBu. That is 2.325 volts, right? My Yamaha receiver will not go any higher than 0 DB on the LFE advanced setup - ie, no plus settings, just neg....

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post #53 of 66 Old 11-29-07, 06:48 AM
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Re: My Three Sons - two front & one down

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A single sub thumps big time - three less so because they are each getting approx 70 watts max.
I don't know, to me it still sounds like you might be getting some cancellation if each sub plays well on its own, but then dies off a lot when you add the others. Have you tried playing them in pairs? That should let you know for sure if one is off from the others... eg: run A + B, B + C, and A + C. If one is causing cancellation due to reversed polarity, it should be pretty easy to pick out, plus running 2 at once should still give you more power and some reasonable volume.

Other thoughts... does your amp have a voltage switch on the back somewhere? Have you double checked your wiring to make absolutely sure you aren't giving the amp a 16 Ohm load or something?

- OJ -

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post #54 of 66 Old 11-29-07, 09:09 AM
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Re: My Three Sons - two front & one down

Warmon,
You should double check your wiring and polarity, because that sounds like the culprit, especially if the 3 subs together are less loud than 1.

How exactly are you wiring the three? All three in series and then bridge your amp into it?
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post #55 of 66 Old 11-29-07, 09:29 AM
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Re: My Three Sons - two front & one down

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Brent, where did you get 1.5ish volts. I'm looking for it and just noticed that near the bottom it say 0 DBu = 0.775 Vrms. Further up it says the P2500 wants a signal of +3 DBu. That is 2.325 volts, right? My Yamaha receiver will not go any higher than 0 DB on the LFE advanced setup - ie, no plus settings, just neg....
Yes, it says 0 dBu = .775 V for half power. Assuming it's linear math, you'd double the power to get +3dB... .775 * 2. I may be wrong assuming the input to output relationship would be linear. However, my 1.5V math is actually higher than Behringer/Nady list for +3.4 dBU...both spec 1.15V.

Which receiver do you have? I was referring to the channel trim levels where you specify the relative output for l/r/c/sb/sl/sub, usually it's a +/- 10 or more range. Your LFE advanced setup sounds like something designed to reduce the LFE signal if the source is adding additional boost since the receiver is supposed to add +10dB to the LFE stream per Dolby Digital spec.

Owen, Ricci and I are trying to say the same thing different ways. Using a battery connected to each sub's posts individually, you can check each driver's polarity. If you connect battery(+) to driver(+) and battery(-) to driver(-), the cone should move away from the magnet. If one of your drivers is wired in reverse, it will play exactly out of phase with the other subs, creating destructive interference and no or reduced output from that pair. Played individually, a reverse polarity driver will have identical output to a normal polarity driver.

-Brent
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post #56 of 66 Old 11-29-07, 02:46 PM Thread Starter
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Re: My Three Sons - two front & one down

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Owen, Ricci and I are trying to say the same thing different ways. Using a battery connected to each sub's posts individually, you can check each driver's polarity. If you connect battery(+) to driver(+) and battery(-) to driver(-), the cone should move away from the magnet. If one of your drivers is wired in reverse, it will play exactly out of phase with the other subs, creating destructive interference and no or reduced output from that pair. Played individually, a reverse polarity driver will have identical output to a normal polarity driver.
Okay guys. Understand...and thanks for helping. I think I'm finally starting to get somewhere. I took everything down today and started from scratch. The polarity / battery test checked out okay - cones move away with polarity and in with reverse polarity. I was very careful in wiring, so I was pretty sure this wasn't it. Each sub has 1.89 ohms of resistance with both coils wired parallel. The three subs are wired in series to give a 5.7 ohm load to the amp in bridged config...which is rated for 8, but will go as low as 2 with more distortion. I think I'm fine there. Wiring is as option #2 - this link:

http://www.the12volt.com/caraudio/wo...s.asp?Q=3&I=42

I think y'all might of missed part of the original post where I said I get good results with one sub powered by a 2ohm stable plate amp. It thumps hard...and is fairly loud. With all three hooked to this plate amp, I get okay results - by then I'm trying to pump too many ohms with this little thing and each one is probably getting maybe 50-60 watts. I could not remember if I tried just two subs off the plate amp for a 4 ohm load, so I did that and results are pretty good too - not as good as one, but pretty good.

My receiver is a Yamaha HTR-5950. I also have an older JVC RX-8010V...which I think was one or two models down from top of the line 4-5 years ago. I know it has something to do with signal, because I get more output with the JVC than I do with the Yamaha.

So back to the HTR-5950: It's new and I don't know it very well. If fact, I never plugged it in until yesterday. In going thru all the menu settings today, I find Volume Trim, however, this doesn't work on the speaker level like you'd think, it works at the component level. This allowed me to boost the signal coming from the DVD - settings range from -6 to +6 DB. Raising this setting did make quite a bit of difference, but not enough to cause clipping.

Up next, I am gonna try some different DVD players to see what happens, but I think I can live with a +3-4 on the component level volume trim setting...if not, I'll probably get a line level shifter or some other gear that will boost the signal and convert unbalanced to balanced...

Oh yeah, Brent is probably right about running the subs alone and I might be getting more output than I think I am.

Warmon - "know what I mean Vern"
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post #57 of 66 Old 11-29-07, 05:05 PM
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Re: My Three Sons - two front & one down

For the 5950, the "Speaker Level Menu" is covered on page 80 of your manual, or 84 if you download the PDF. Adjustment range is +/-10 for all speakers. You need to do this anyway for getting the balance right when watching movies. Default is 0dB, so you've got the potential for 10dB of extra gain right there. From the spec section, the 5950's sub out is capable of 4V, so there shouldn't be any problem with enougy voltage to drive the P2500 once you get the setting configured correctly.

"LFE level" is what I thought it was...just leave it at 0, it only works on DD anyway.

The +/-6 setting you described is "volume trim" which is used to balance the input signal between sources.

You have a choice of crossover frequencies..also on page 80 of the manual. Default is 80hz. If the Yamaha and JVC are using different crossover frequencies or even bass management settings, you could hear different results.

Interesting and almost incredulous. In the default setting, the 5950 routes redirected bass and LFE information to both the sub and l/r mains, regardless of the small/large setting on the mains. Page 79 paper/83 pdf. Suggest changing this to subwoofer only, depending on your mains and how much bass you really want. However, very few mains are capable of keeping up with a sub, let alone 3.

Based on your last posting and reading the manual, I think you just need to do a little more fiddling with the 5950...and show us some objective measurements with an SPL meter and REQW if you're setup for it.

Good luck!

-Brent
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post #58 of 66 Old 11-29-07, 05:11 PM
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Re: My Three Sons - two front & one down

Quote:
I think y'all might of missed part of the original post where I said I get good results with one sub powered by a 2ohm stable plate amp. It thumps hard...and is fairly loud. With all three hooked to this plate amp, I get okay results - by then I'm trying to pump too many ohms with this little thing and each one is probably getting maybe 50-60 watts. I could not remember if I tried just two subs off the plate amp for a 4 ohm load, so I did that and results are pretty good too - not as good as one, but pretty good.
If I'm correctly remembering the differences, I can explain this. The plate amp has a gain knob...meaning the more you twist it, the more it boosts the incoming signal. The P2500 "volume" controls are actually attenuators so anything less than wide open is actually reducing the drive signal...something I asked about in my first post.

So, with the plate amp, you were able to get more power to the subs via increasing the gain at the plate amp, regardless of the receiver's drive level. With the P2500, you can't really do anything to boost the input signal or the output to the subs.

I'm sure someone will quickly correct me if I got this wrong.

-Brent
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post #59 of 66 Old 11-29-07, 06:47 PM Thread Starter
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Re: My Three Sons - two front & one down

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For the 5950, the "Speaker Level Menu" is covered on page 80 of your manual, or 84 if you download the PDF. Adjustment range is +/-10 for all speakers.
Brent, thanks for hanging in there buddy! I went thru this part earlier and here's where I was thrown for a loop. When setting the SWFR level it goes into some low waffling mode and moving it up or down doesn't do anything until you save / exit out. I thought it wasn't doing anything, so I kept moving it back to 0. if only I had saved / exited setup... Boy, do I feel soooo stupid!!!

So guess what?...everything now works as it should with a little boost..

There is only one phrase to sum up what these things sound like now: ...this is some serious bass.

Warmon - "know what I mean Vern"
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post #60 of 66 Old 11-29-07, 07:04 PM
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Re: My Three Sons - two front & one down

Glad to hear you got it all working. Just in time for the weekend. Enjoy!
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