Can you use a digital multimeter (DMM) to tune a subwoofer in a home theatre system?

[James1294]

I know you can use a DMM to tune your sub in your car stereo system but I was just wondering if I can do the same for my home theatre system. I have a Yamaha RXV661 amplifier, Yamaha RSW300 subwoofer (80 watts. 270 watts RMS) and Yamaha NS-555 speakers (100 watts RMS)

 

[Speedskater]

Would not using a 'cal mic' or even a SPL meter be easier?
How does one tune a car system with a 'DMM' ?
Does that 'DMM' need to be a true RMS 'DMM' ?

 

[James1294]

Don’t want to spend $100+ on a decent SPL meter to give me quality reading. If you don’t know how to use a DMM to tune a car sound system to the RMS then I don’t think you have enough knowledge for this thread.

 

[WaynePflughaupt]

Well, if you think a “quality” SPL reading is required for setting up a sub in a HT system, I’d question your knowledge.

Participating on various home-audio forums for 20 years, I’ve never heard of anyone doing what you’re proposing. Perhaps you’d get better answers at a car audio forum, since I’m sure there’s no shortage of people there who also have home systems.

Or maybe you could blaze a new trail and explain to us ignorant rubes how the process works. It might then be easier for someone to answer your question.

Regards,
Wayne A. Pflughaupt

 

[lovinthehd]

I've never heard of this DMM method of setting up a sub in any system....I'm all ears.

 

[mazersteven]

Yamaha RSW300 subwoofer

Maybe get a Subwoofer worth integrating into a system.

 

[James1294]

That’s what I’m saying, I’ve used a DMM to set up a car audio system which I have lots of knowledge about. But I’m fairly new to home theatre systems so I’m asking the question if you can do the same to tune a subwoofer in a home theatre system. But by the sounds of it, you can’t.

 

[WaynePflughaupt]

We'd be in a better position to make an assessment if you'd enlighten us as to the process, or at least point us to an article.

Regards,
Wayne A. Pflughaupt

 

[lovinthehd]

Might depend what you call "set up" so me too in wanting to know just how that happens.

 

[mazersteven]

How do you do the sub crawl in the trunk of a car?

 

[mtrycrafts]

....I'm all ears.

But, is that digital?

 

[mtrycrafts]

How do you do the sub crawl in the trunk of a car?

Very carefully?

 

[mtrycrafts]

... (80 watts. 270 watts RMS) ...)

What's this? Firstly, power is not measured in RMS.

Secondly, what good is it to measure voltage input to a sub?

 

[NINaudio]

I was into car audio for many years, including doing some IASCA competitions. I've also never heard of using a DMM to "tune" a sub. Am interested in the process as well.

 

[highfigh]

I know you can use a DMM to tune your sub in your car stereo system but I was just wondering if I can do the same for my home theatre system. I have a Yamaha RXV661 amplifier, Yamaha RSW300 subwoofer (80 watts. 270 watts RMS) and Yamaha NS-555 speakers (100 watts RMS)

You can't use a DMM to tune a sub to match the car or room, you use it to tune the cabinet.

 

[highfigh]

How do you do the sub crawl in the trunk of a car?

You don't. The trunk is pressurized by the energy from the sub and then, it mates with the passenger compartment. The tuning frequency matters, but it needs to be tuned so that it works with the vehicle (longer/larger vehicles have a lower resonant frequency than shorter/smaller cars) and the distances to the listener and speakers. Until DSP became available in cars, phase issues were a royal PITA to deal with. The choice was normal or inverted polarity- whatever worked best.

 

[highfigh]

What's this? Firstly, power is not measured in RMS.

Secondly, what good is it to measure voltage input to a sub?

If you don't have the parameters, you can use DMMs to measure the voltage drop at various frequencies and graph it, to make an impedance curve after calculations. This will show the Fs and by determining the Vas & a few other parameters, the basic box calculations can be made. That was the way before box simulators made it easy.

 

[mazersteven]

You don't. The trunk is pressurized by the energy from the sub and then, it mates with the passenger compartment. The tuning frequency matters, but it needs to be tuned so that it works with the vehicle (longer/larger vehicles have a lower resonant frequency than shorter/smaller cars) and the distances to the listener and speakers. Until DSP became available in cars, phase issues were a royal PITA to deal with. The choice was normal or inverted polarity- whatever worked best.

My comment was meant to be Sarcastic. Sorry for the confusion

 

[Speedskater]

OK, so you could use a true RMS voltmeter to measure the impedance curve of a driver, in designing a passive crossover. You could then use that meter to check the crossover design, by measuring at the voltage at each driver.
But that won't tell you much about the acoustic output of the loudspeaker. Or tune a completed system.

 

[highfigh]

OK, so you could use a true RMS voltmeter to measure the impedance curve of a driver, in designing a passive crossover. You could then use that meter to check the crossover design, by measuring at the voltage at each driver.
But that won't tell you much about the acoustic output of the loudspeaker. Or tune a completed system.

Impedance is a calculated value, he voltage drop across the speaker's terminals is measured and an impedance curve is made by connecting the points that correspond to the frequency measurements. Using an oscilloscope would be much easier and more accurate since most affordable DMMs aren't accurate at all frequencies unless specifically designed to be.

It won't tell ANYTHING about the acoustic output of the driver, just the physical characteristics that are used to determine the type & size of box or, if someone wants to spend a ton of time making tedious measurements.

At this point, doing it the hard way would be a good teaching tool, though. Vance Dickason's book 'The Loudspeaker Design Cookbook' shows this procedure and the formulae for the calculations.