Assorted dummy questions by mike c:

[mike c]

Somebody please help me understand how a speaker’s crossover works

suppose a speaker has two pairs of binding posts … one for the highs and one for the lows:

1) if a full range signal was sent to the highs, the built in crossover will filter the lows right?

If yes,

and my purpose is to filter out the lows from a bookshelf speaker, and bi-amp in the process as well:

2) can I do the following but still get the benefit of a signal filtered of <80hz?
Full range going to the subs input, then from the filtered outputs into the LOWS
Full range going to the HIGHS

 

[mike c]

How about PHONO inputs and TAPE inputs:
Can I use PHONO and TAPE inputs for anything else? Like a CD player for example? Is there a disadvantage?

 

[mike c]

Regarding receiver audio inputs:
I see most specs having 100db SNR quoted for “CD” … does that mean the other inputs have crappier SNR’s?
What is the audible threshold for SNR?

 

[mike c]

Regarding THD:
Awhile back, I took this test:

http://www.klippel-listeningtest.de/lt/default.html

i think i did -18db max and -12db average (i think), how does that translate to %THD?

 

[Haoleb]

How about PHONO inputs and TAPE inputs:
Can I use PHONO and TAPE inputs for anything else? Like a CD player for example? Is there a disadvantage?

You can use the tape inputs for anything. The phono input is used to seeing a very small signal that must be equalized according to the RIAA curve, and then amplified. You cannot plug anything other than the output from a turntable's cartridge into this input.

 

[tbewick]

This paper mentions audible noise thresholds for various formats:

http://www.meridian-audio.com/ara/coding2.pdf
'Coding High Quality Digital Audio', by J. Robert Stuart. Meridian Audio Ltd.

 

[skizzerflake]

Regarding receiver audio inputs:
I see most specs having 100db SNR quoted for “CD” … does that mean the other inputs have crappier SNR’s?
What is the audible threshold for SNR?

I think they got on this 100db thing because in the early days CD players bragged about 100 db noise and the receiver manufacturers didn't want to sound like they were going to add noise. Since a CD input isn't really different from a tape or other input (except phono), they all ought to be comparable. As for what's audible, it depends on listening conditions and noise frequency but suffice to say that 100 db is well past audible. 80 is probably as quiet as most people can hear.

 

[Adam]

You can use the tape inputs for anything. The phono input is used to seeing a very small signal that must be equalized according to the RIAA curve, and then amplified. You cannot plug anything other than the output from a turntable's cartridge into this input.

Very true. Loosely translated, if you plug anything but a turntable into the phono input, it will sound extremely loud. I did that once by mistake. Once.

 

[Swerd]

Somebody please help me understand how a speaker’s crossover works. Suppose a speaker has two pairs of binding posts … one for the highs and one for the lows:

1) if a full range signal was sent to the highs, the built in crossover will filter the lows right?

If yes,

and my purpose is to filter out the lows from a bookshelf speaker, and bi-amp in the process as well:

2) can I do the following but still get the benefit of a signal filtered of <80hz?
Full range going to the subs input, then from the filtered outputs into the LOWS
Full range going to the HIGHS

To keep this simple, let's assume we're talking about 2-way speakers, one woofer and one tweeter, with a passive crossover built into the speaker cabinet. And let's also assume the crossover point is at 2,000 Hz, which is typical for many bookshelf 2-way speakers.

The crossover will have two separate sections in it, a low-pass filter that feeds signal below 2,000 Hz to the woofer, and a high-pass filter that feeds signal above 2,000 Hz to the tweeter.

These crossover sections can be built so both are wired to one set of binding posts, or as in your case to two separate sets. If you use jumper wires to connect one set of posts to the other, it is the same as if you had only one set of posts. Without the jumper wires, one set of posts connects only to the woofer low-pass filter, and the other connects only to the tweeter high-pass filter.

If you want to bi-amp, you will need two amps (or amplifier channels) per speaker. Connect one amp to the lower set of posts, and another to the upper set.

Your first question doesn't make sense to me because the tweeter will never get a full range signal. Most tweeters will be damaged by that.

Your second question also confuses me, but I think you are asking if you can filter out the bass below 80 Hz from your bookshelf speakers, and bi-amp them as well. The answer is YES.

With a HT reciever, you have another optional crossover to use between a subwoofer and your other speakers. This crossover is built into your HT receiver and works upstream from the signal your other speakers get. If you set this crossover to 80 Hz, your subwoofer gets signals 80 Hz and below, and your bookself speakers get signal above 80 Hz. If you bi-amp as well, the bookshelf's woofer gets signals from 80-2,000 Hz, and the tweeter gets signals above 2,000 Hz.

Does that answer your question? Or is your set-up different?

 

[mike c]

To keep this simple, let's assume we're talking about 2-way speakers, one woofer and one tweeter, with a passive crossover built into the speaker cabinet. And let's also assume the crossover point is at 2,000 Hz, which is typical for many bookshelf 2-way speakers.

The crossover will have two separate sections in it, a low-pass filter that feeds signal below 2,000 Hz to the woofer, and a high-pass filter that feeds signal above 2,000 Hz to the tweeter.

These crossover sections can be built so both are wired to one set of binding posts, or as in your case to two separate sets. If you use jumper wires to connect one set of posts to the other, it is the same as if you had only one set of posts. Without the jumper wires, one set of posts connects only to the woofer low-pass filter, and the other connects only to the tweeter high-pass filter.

If you want to bi-amp, you will need two amps (or amplifier channels) per speaker. Connect one amp to the lower set of posts, and another to the upper set.

Your first question doesn't make sense to me because the tweeter will never get a full range signal. Most tweeters will be damaged by that.

Your second question also confuses me, but I think you are asking if you can filter out the bass below 80 Hz from your bookshelf speakers, and bi-amp them as well. The answer is YES.

With a HT reciever, you have another optional crossover to use between a subwoofer and your other speakers. This crossover is built into your HT receiver and works upstream from the signal your other speakers get. If you set this crossover to 80 Hz, your subwoofer gets signals 80 Hz and below, and your bookself speakers get signal above 80 Hz. If you bi-amp as well, the bookshelf's woofer gets signals from 80-2,000 Hz, and the tweeter gets signals above 2,000 Hz.

Does that answer your question? Or is your set-up different?

sorry I was unclear ...

I have a multichannel amp and a 2 channel preamp that has two sets of pre-outs (so there is no need to WYE).

I was wondering if the HIGHs binding posts (tweeter) is fed a full range signal (from the pre-outs), will the built in highpass crossover protect it?

 

[jcPanny]

Crossover

Unless you open the speaker cabinet and bypass the cossover, the crossover is wired between the binding posts and the woofer / tweeter.

 

[Swerd]

I was wondering if the HIGHs binding posts (tweeter) is fed a full range signal (from the pre-outs), will the built in highpass crossover protect it?

Yes, as long as the speaker's built in crossover is there, you should be fine.

 

[mike c]

Unless you open the speaker cabinet and bypass the cossover, the crossover is wired between the binding posts and the woofer / tweeter.

so you are saying, I can send a full range signal to the highs, and the crossover WILL shave off <2000hz ?

Yes, as long as the speaker's built in crossover is there, you should be fine.

ok, I was thinking that instead of WYE-ing the 80hz highpassed signal from the sub, why not feed a full range signal to the tweeter since IF it has a lowpass to protect it anyway ... and only use the 80hz HP sub output to the midwoofer to save it from playing below 80hz.

 

[mike c]

You can use the tape inputs for anything. The phono input is used to seeing a very small signal that must be equalized according to the RIAA curve, and then amplified. You cannot plug anything other than the output from a turntable's cartridge into this input.

thanks, at least that's an extra input, I'm assuming, it also shares the same SNR with the other inputs?

This paper mentions audible noise thresholds for various formats:

http://www.meridian-audio.com/ara/coding2.pdf
'Coding High Quality Digital Audio', by J. Robert Stuart. Meridian Audio Ltd.

thanks, will read that.

I think they got on this 100db thing because in the early days CD players bragged about 100 db noise and the receiver manufacturers didn't want to sound like they were going to add noise. Since a CD input isn't really different from a tape or other input (except phono), they all ought to be comparable. As for what's audible, it depends on listening conditions and noise frequency but suffice to say that 100 db is well past audible. 80 is probably as quiet as most people can hear.

I'll wikipedia why SNR's are better going up in db's rather than down. thanks

 

[WmAx]

suppose a speaker has two pairs of binding posts … one for the highs and one for the lows:

1) if a full range signal was sent to the highs, the built in crossover will filter the lows right?If yes,

The crossover on a 2 way bi-amp posted passive crossover(tied together with a shorting strap or bar for single amp use) has the tweeter and midbass xover circuits isolated from one another. They will always work in this way:

Tweeter: pass all frequencies above X frequency. Protects tweeter from LF.

Midbass: Pass all frequencies below X frequency.

and my purpose is to filter out the lows from a bookshelf speaker, and bi-amp in the process as well:

2) can I do the following but still get the benefit of a signal filtered of <80hz?
Full range going to the subs input, then from the filtered outputs into the LOWS
Full range going to the HIGHS

Yes. You can always filter the LF from the speakers using an active crossover(such as that in your receiver when set to 'small'). This will reduce distortion at moderate to high SPLs. If you mean the built in passive satellite xovers found in some subwoofers where you run your main amplifier speaker leads to it, then connect main speakers to the sub passive output filters, I will recommend against using these. This can not work properly with a random speaker( a speaker it was not intentionally designed to filter) due to the complex unique electrical parameters inherent of different speakers.

How about PHONO inputs and TAPE inputs:
Can I use PHONO and TAPE inputs for anything else? Like a CD player for example? Is there a disadvantage?

The TAPE input will usually be the same as the CD input, and other normal LINE inputs. Of course, any manufacturer is free to deviate a circuit on different INPUTS, but it makes no sense to do so, so I can not imagine it being done(except maybe in the rarest of occasions).

The PHONO input can not be used for normal LINE INPUT purposes. It (1) has a very high voltage sensitivity -- it will clip/distort with normal line level input [and] (2) It has an equalization curve commonly referred to as a RIAA curve(a required curve to help compensate for ideal mastering process of LPs) applied to all signals input through it.

Regarding receiver audio inputs:
I see most specs having 100db SNR quoted for “CD” … does that mean the other inputs have crappier SNR’s?What is the audible threshold for SNR?

The SNR is only valid in a controlled scenario. It will vary(always in the direction of poorer performance) in actual use, when you consider the complex interaction of different components cascaded. As for relevance: in controlled study, it is found by preliminary study[1] that about 80dB SNR is transparent in ideal laboratory conditions. Normal home environments(with inherently higher noise floors) will normally decrease this requirement. It is interesting to note that it is difficult to find recordings with actual SNR of even 60db unless aggressive digital noise reduction techniques are used in production.

Regarding THD:
Awhile back, I took this test:

http://www.klippel-listeningtest.de/lt/default.html

i think i did -18db max and -12db average (i think), how does that translate to %THD?

The test at that link simulates a speaker, and the various high harmonic nasty non-linear behaviour(s) that result when driving that speaker out of it's linear motor range. It should probably not be compared directly with the standard THD spectrum distribution created by a driver operating within it's linear range. As you increase the level of upper harmonics(as in the Klippel test), you increase audibility of harmonic distortion.

A -12dB ratio to 0 db is approximately 25%. A -18 dB ratio to 0 dB is approximately 12.5%. If you repeat/practice this test on high quality transducers, you will likely be able to get down to -36(1.6%) or lower, if listening critically and at high volume(to help hear the distortion better). The real lesson here is to simply not drive a loudspeaker to the point where it becomes highly non-linear.

-Chris

Footnotes

[1] Signal-to-Noise Ratio Requirement for Digital Transmission Systems
Spikofski, Gerhard
AES Preprint: 2196

 

[WmAx]

I'll wikipedia why SNR's are better going up in db's rather than down. thanks

SNR = Signal To Noise Ratio

Signal is always assumed to be 0 dB. There for, noise is expressed as a relative level below the 0 dB signal. So, a 100dB SNR actually means noise is -100dB in RMS power when compared to the 0dB signal.

-Chris

 

[mike c]

Yes. You can always filter the LF from the speakers using an active crossover(such as that in your receiver when set to 'small'). This will reduce distortion at moderate to high SPLs. If you mean the built in passive satellite xovers found in some subwoofers where you run your main amplifier speaker leads to it, then connect main speakers to the sub passive output filters, I will recommend against using these. This can not work properly with a random speaker( a speaker it was not intentionally designed to filter) due to the complex unique electrical parameters inherent of different speakers.

what about the low-level inputs? (RCA inputs and outputs on the back of the subwoofer with an 80hz highpass)

since this is a 2 channel setup, I won't have the benefits of a receiver's crossover or an external crossover

 

[WmAx]

what about the low-level inputs? (RCA inputs and outputs on the back of the subwoofer with an 80hz highpass)

since this is a 2 channel setup, I won't have the benefits of a receiver's crossover or an external crossover

The LINE level input/output filters will do a sufficient job(if present), at least so far as properly separating the frequency bands using a theoretical transfer function(other variables may need to be addressed for a particular application).

-Chris

 

[ski2xblack]

...this is a 2 channel setup, I won't have the benefits of a receiver's crossover or an external crossover...

I too have a 2.1 stereo setup, and an active crossover is well worth it: better dynamics, higher spl if needed, better protection for your mains, easier on your main channel amp. You may be able to find one used that is inexpensive. Look for the Outlaw ICBM, M&K BMC Mini, or NHT X2 on the used market, should be affordable. There are probably others I am unfamiliar with. With one of these you can bi-amp properly. Your ears will thank you.

 

[mike c]

for a stereo setup - with stereo subs:
my amps are behind me and i want to add stereo subs.

can I do the following, instead of wiring a new set of speaker wires running from the amp to the subs?

speaker wire from amps - to main speaker - to speaker level inputs on the subwoofer (CHT15R)

any cons on doing this?