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Proper home amp for large subwoofer (13w7)?

 

Bronze Member
Username: Jodavis

Toronto, Ontario Canada

Post Number: 32
Registered: Apr-09
Hi all,

I'm putting a 13w7 ported in my house and I'm not sure if power amplifiers like crown, qsc etc. are meant to handle low frequencies or if you actually have to go and get a power subwoofer amplifier? My receiver already comes with the sub pre-outs so a subwoofer amp would kind of be a waste seeing as the receiver controls the bass. Can power amps be used with subs?
 

Gold Member
Username: Illuminator

USA

Post Number: 5560
Registered: Apr-05
In other words, home audio amplifiers with car subwoofers?

NO!

Car subwoofers, especially the one you have (dual 1.5ohm if I recall correctly) have a very low impedance so that it doesn't take as much power from a car amplifier to properly power them. However, home amplifiers are meant to be matched up with 8 ohm speakers, sometimes 6ohm at the very minimum.

If you hook up a car audio sub with a low impedance to a home amplifier, you will be drawing way too much current from the home amplifier and it will cause damage. This usually happens in the form of blowing the capacitors in the power supply or ruining the actual output transistors. I've seen this happen.

If you want to hook up a car amplifier to the sub in the home, check out this thread: https://www.ecoustics.com/electronics/forum/home-audio/685111.html
 

Bronze Member
Username: Jodavis

Toronto, Ontario Canada

Post Number: 33
Registered: Apr-09
I'm not talking about the high impendence amps that are used for home speakers. I'm talking about stereo p/a power amps. QSC's and crowns can take a 2 ohm load.
 

Gold Member
Username: Illuminator

USA

Post Number: 5562
Registered: Apr-05
Then it's fine. I wasn't sure what amplifiers you were talking about since most amplifiers, really, are "power amplifiers." Just watch the impedance and you're good. If you're coming from car audio anyway, you're probably already aware of that.

It's just that there are quite a few uninformed individuals who hook up their 2 ohm subwoofer to their 8ohm minimum receiver and end up damaging it, just trying to avoid that from happening.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 16401
Registered: May-04
.

Do you have a Crown, QSC, etc? It would be a waste of money to buy a full range power amplifier just to drive a subwoofer IMO. You're better off buying a plate amp meant for subwoofer use. But most plate amp's designed for home use aren't going to like a 2 Ohm load. Buying an amplifier to suit what is a somewhat silly impedance load in your sub is also a waste of money IMO. Home audio doesn't work the way car audio does, we run off wall current at about 15 amps max. If you want to have really, honestly high current amplifiers in your home system, you'll spend a good deal of cash for a very stout amplifier. Trying to squeeze a square peg into a round hole doesn't make sense just because it will give you something to do.

Why not just spend the money you would invest in a jerry rigged car system in your home system on something that is actually meant for home use and be done with it?

Did you bother to read the linked thread and why a car sub might not sound very good in your house?


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Bronze Member
Username: Jodavis

Toronto, Ontario Canada

Post Number: 34
Registered: Apr-09
I've heard quite a handful of people tell me that car subs are really just "subwoofers" listed under a car audio category. A jl audio 13 w7 has excellent reviews for home theatre. I'll just have to contruct the box differently.
 

Platinum Member
Username: Plymouth

Canada

Post Number: 16471
Registered: Jan-08
Julien

You can use also a Berhinger which cost less than QSC or Crown, you can use both 13w7's in serial to match the impedance of the amp!
 

Bronze Member
Username: Jodavis

Toronto, Ontario Canada

Post Number: 35
Registered: Apr-09
I actually thought of using berhinger as an amp to drive it. There are posts that actually had berhingers hooked up to large subs, even a w7. But it is a cheaper amp so picking a berhinger with an rms rating waaayy over the subs rms would be a wise move.
 

Platinum Member
Username: Plymouth

Canada

Post Number: 16481
Registered: Jan-08
Julien

For which Berhinger model are you looking?
 

New member
Username: Darrindeesmith

Post Number: 1
Registered: Jul-17
I run two jlw13 ae subs from a beringer ep4000 wired at 3 ohm each running 2 channels and it does a pretty good job.
I'm running through an electronic crossover before the amp 100 megahertz and lower.
although I think more power would be better but it's not too bad, still rattles the windows knock stuff off shelving.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18434
Registered: May-04
.

I always hate to disappoint those folks who think power rattles windows and shakes things on shelves. "Power" has little to do with it, you are simply hitting a frequency which creates sympathetic resonances in the objects which rattle.

A 2017 $199 receiver probably won't manage this "trick" but most any mediocre to decent quality amplifier will, given a speaker/sub that can reach into the low 30-35Hz range. We used to pull this trick with double Advents (which could reproduce well into the low 30Hz range) and a 75 watt Tandberg receiver back in 1975. Made plaques jump off the wall and wallets jumped right out of back pockets before the plaque hit the floor. Worked every time!

If the amp can deliver the power into the load and the speakers/sub can reach beneath 40Hz before they start to peter out (lord knows, you would expect any "subwoofer" to do that much at least), things will shake.

The resonant frequency can be much higher than 40Hz. Actually, it can be any multiple of the bass frequency. It's the "resonance" frequency that matters. If the speaker hits, say, 50Hz and the resonant frequency of the window is 200Hz, it will rattle.

It's more of a carnival trick than anything else. Impressive, if you don't understand the physics of the trick, but a trick none the less.



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Gold Member
Username: Magfan

USA

Post Number: 3459
Registered: Oct-07
While 'sympathetic' vibration is probably the main phenom here, a 2nd type of vibration called 'Forced' is possible, as well.
It takes a LOT of power but can be done. In my room? When listening to Saint Sans Symphony #3 'with organ', the low 16hz tone at higher levels rattles stuff on the walls and you can clearly see the windows 'ripple' with reflection/ distortion. Low-cutting the main speakers at about 50hz/12db-octave probably saves the speakers.
Sometimes when watching an effects-laden movie, you can feel the vibration coming up thru your seat. The dinosaur walking sequence from Jurrasic Park is fine for this.

Experimenting with double Advents was fun. Either side-by-side, toed OUT maybe 20degrees, OR on top of one another, tweeter down or up on the upper speaker. I preferred the tweeters as close as possible so went with tweeter down on the upper speaker, up on the lower.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18447
Registered: May-04
.

"the low 16hz tone at higher levels rattles stuff on the walls and you can clearly see the windows 'ripple' with reflection/ distortion."



The 16Hz tone in your music - if it can even be faithfully reproduced - is not a single, pure sinewave. It, like any acoustic instrument's frequency output is only the fundamental tone which is accompanied out to infinity with harmonic tones related to the fundamental. That would make it very, very difficult to pin point any sympathetic resonance to only the 16Hz fundamental as the cause.

Any harmonic frequency related to your 16Hz, the very strong 2nd, 3rd and so on (keep in mind, many low frequency drivers generate their own high levels of harmonic distortions which can run into the 20% range in the deep bass frequencies and, therefore, make a naturally strong second harmonic even more forceful and substantially less true to the actual frequency contained in the music) going out to infinity can cause sympathetic resonance with, say, a picture on a wall where the wall also begins to vibrate.

Small items sitting on the cavity of a bookshelf may be reacting only to the resonance of the bookshelf as a naturally occurring resonant cavity being set into motion. No telling which fundamental tone might have set the bookshelf into resonance. It might be the pressure waves generated by the loudspeaker or it might be the fundamental flexure, and its harmonic frequencies, being created in the floor which is reacting to the pressure waves pushing against it.

Thinking you can generate ANY tone within the resonant cavity which is the domestic listening room and believing only one frequency will exist within the room is a highly non-educated, not rational approach to solving the many issues of room sound and their significant contribution to the final product we call "our music".

Within the confinements of a domestic listening room, the barriers of the room naturally, and according to the laws of physics, tend to amplify certain frequencies over others (at times, by as much as 10-20dB), making it even more difficult to ascribe "reaction" to any single frequency generated by the audio system. Troughs created by peaks and nulls can be as high as 60dB within the typical domestic listening room.

The "trick" performed by the Double Advents and other low frequency loudspeakers is often related to the fact walls are not solid. If a wall is not solid, then the series of cavities which make up the wall (the resonant cavity created by the studs, foot plate and top plate and covered by non-rigid drywall will all have their own resonant frequencies which are contributing to the output of pressure waves within the room. The wall will, therefore, beat as a series of drums all with their own distinct and individual fundamental frequency and its harmonics.

Each non-solid surface which makes up the boundaries of the room will have a similar reaction to being excited by the pressure waves coming from the loudspeaker and being amplified by each subsequent cavity and barrier dimension. The lower the fundamental frequency which is starting every surface into motion, the more difficult it becomes to say "X" frequency exists with any dominance within the room.

The wall attached to the Advents' shelving had been created specifically to house the receiver and speakers. Alongside the cavity which housed the loudspeakers were other cavities created by the studs and drywall which was then paneled with wood. Each cavity of the inner wall space created yet another resonating enclosure in reaction to being excited into motion by the output of the loudspeakers and the physical contact of the walls/shelving to the cabinets of the Advents.

This is what is going on in virtually any domestic listening room - a series of "drumbeats" generated by the movement of the non-rigid wall surfaces behind which exists a resonating cavity. Even if you could successfully decouple the loudspeaker enclosures from contact with the room barriers, you cannot decouple the room surfaces from each other.

Glass has an extremely low R value which makes it an easy surface to excite into sympathetic motion. Not necessarily from the original tone generated by the audio system, but more likely by the series of drumbeats being generated by the wall cavities surrounding the window or from any large parallel surface which is also being excited into motion.

The issue remains the single most significant contributor to good or bad sound in a typical listening room is the room itself. Unless you have built an underground bunker with absolutely rigid barrier walls lacking any enter/exit openings, the room surfaces are being excited into sympathetic resonance with the multiple and ever changing musical tones. Every surface may be contributing another fundamental frequency and its subsequent harmonics which may - likely will be - broken down into multiple cavity induced resonances. All of this adds to the complexity of determining which specific frequency has created another sympathetic resonance in any object within the space. It is what makes the creation of a true anechoic chamber so expensive and so rare.

Yes, "forcing" an object into reaction requires a fair amount of SPL - however, SPL has little to do with amplifier "power". If the driver can generate 125dB with fewer than ten watts, that is what matters when it comes to the issue of SPL's.

In other words; https://www.youtube.com/watch?v=B2WcBi9mu6A


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Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18448
Registered: May-04
.

Here's the edited version of the above post which does, IMO, include a few pertinent ideas ...

.

"the low 16hz tone at higher levels rattles stuff on the walls and you can clearly see the windows 'ripple' with reflection/ distortion."



The 16Hz tone in your music - if it can even be faithfully reproduced - is not a single, pure sinewave. It, like any acoustic instrument's frequency output is only the fundamental tone which is accompanied out to infinity with harmonic "overtones" which are mathematically related to the fundamental frequency. A 16Hz fundamental will be accompanied by a 32Hz harmonic, which is typically the stronger of the two frequencies in many acoustic instruments. 32 Hz is more easily accomplished by many modern loudspeakers/subwoofers and is more easily perceived by the human hearing mechanism.

As we have discussed on previous occasions, the belief the 16Hz signal is even there in the room is rather stretching the facts. Very few domestic listening rooms could even support an extremely large 16Hz wavelength.
32Hz would probably be within the range of most decent and large loudspeakers/subwoofers and within the support
capacity of many listening rooms dedicated to large loudspeaker systems.

All of that would make it very, very difficult to pin point any sympathetic resonance to only the 16Hz fundamental as the cause of any reaction by, or within, other surfaces and enclosures.

Any harmonic frequency related to your 16Hz, say the very strong 2nd, 3rd and so on going out to infinity, can cause sympathetic resonance with, say, a small rectangular picture frame on a wall where the larger wall also begins to vibrate. Keep in mind, any low frequency driver will generate its own high levels of harmonic distortions (which can run into the 20%+ range in the deep bass frequencies) and, therefore, can make a naturally strong second harmonic even more forceful and substantially less true to the actual frequency contained in the music when we consider real world sound within the room itself.

Small items sitting on or within the cavity of, say, a bookshelf may be reacting only to the resonance of the bookshelf itself which is acting as a naturally occurring resonant cavity being set into motion by pressure waves and/or physical contact with another resonating surface such as the floor. There is no way of telling which specific fundamental tone or harmonic frequency generated by the audio system alone which might have initially set the bookshelf into resonance. It is enough to recognize as a law of physics which is not negotiable that cavities naturally resonate when excited. It might be the pressure waves generated by the loudspeaker or it might be the fundamental flexure frequency, and its harmonic frequencies, being created in the floor which is reacting to the pressure waves pushing against it. A 16Hz input does not equate to a 16Hz output resonance in such cases.

Thinking you can generate ANY tone within the resonant cavity which is the domestic listening room and believing only one frequency will exist within the room is a highly non-rational approach to solving the many issues of "room sound" and their significant contribution to the final product we call "our music".

Within the confinements of a domestic listening room, the barriers of the room naturally, and according to the laws of physics, tend to amplify certain frequencies over others (at times, by as much as 10-30dB), making it even more difficult to ascribe a "reaction" to any single frequency generated by the audio system. Troughs created by peaks and nulls naturally occurring within the enclosure can be as high as 60dB in the typical domestic listening room. Therefore, the SPL generated by the loudspeaker itself at any given frequency may be far less consequential to the sympathetic reactions occurring within the listening room.



The "trick" performed by the Double Advents and other low frequency loudspeakers is often related to the very simple and well established fact that WALLS ARE NOT SOLID. If an object is not solid and therefore non-reactive to pressure waves, then it will also become a secondary resonant cavity with its own set of resonant frequencies contributing to the overall output perceived or measured within the room. Objects, lacking the perceptual nature of human hearing, may, therefore, react to frequencies which the listener is only vaguely aware of.


If a wall is not solid, then the series of cavities which make up the wall (seen as the group of individual resonant cavities created by the multiple series of studs, foot plate and top plate and covered by non-rigid drywall and any breaks in the absolute uniformity of these cavities) will all have their own fundamental and resonant frequencies which are contributing to the output of pressure waves within the room. The wall will, therefore, beat as a series of "drumheads", all with their own distinct and individual fundamental frequency and its harmonics.

You might say the wall itself has a single fundamental output but that would only be true if the barrier surface was actually solid enough to be considered absolutely non-resonant, which is almost impossible in reality. What you can say more easily would be that the dimensions of the barrier surface, in conjunction with other barrier surfaces' dimensions, will favor certain frequencies over others, which must also then be taken into consideration when we are discussing dominant and subdominant resonant frequencies within the room itself.

Each non-solid surface which makes up the boundaries of the room will have a similar, though possibly unique, reaction to being excited by the pressure waves coming from the loudspeaker and being amplified or nullified by each subsequent cavity and barrier dimension which makes up the total enclosure volume. Smaller rooms are more easily excited into higher levels of resonance than are larger rooms and smaller rooms have different resonance signatures than large rooms. Squared dimensions have different signatures than do rectangles and peaked or curved ceilings give yet another signature resonance. Openings and doorways along a wall, or windows with their low resistance to passing through pressure waves, also give different resonant signatures due to their leakage of pressure waves into adjacent areas.

The lower the fundamental frequency which is starting every surface into motion, the more difficult it becomes to say "X" frequency exists with any dominance within the room.



The wall attached to the Double Advents' shelving had been created specifically to house the source player, the receiver and the speakers. Alongside the cavity which housed the loudspeakers were other cavities created by the studs and drywall which was then paneled with wood. Each cavity of the inner wall space created yet another resonating enclosure in reaction to being excited into motion by the output of the loudspeakers AND the physical contact of the walls/shelving to the cabinets of the Advents. Anyone who remembers the Advents should know the cabinet was anything but silent when the system was reproducing extremely low frequencies. So we might surmise it was the combined resonant frequencies of the Advent enclosures in contact with the resonant cavity of the wall which actually caused the reaction of the plaque. It doesn't really matter today since the effect was the same then, a sale was closed.

This is though what is going on in virtually any domestic listening room - a series of "drumbeats" generated by the movement of the non-rigid wall surfaces behind which exists a resonating cavity. Even if you could successfully decouple the loudspeaker enclosures from contact with the room barriers, you cannot decouple the room surfaces from each other nor can you eliminate the effect of the enclosure's dimensions.



Glass has an extremely low R value which makes it an easy surface to excite into sympathetic motion. Not necessarily from the original tone generated by the audio system, but more likely by the series of drumbeats being generated by the wall cavities surrounding the window or from any large parallel surface which is also being excited into motion.

The issue remains the single most significant contributor to good or bad sound in a typical listening room is the room itself.

Unless you have built an underground bunker with absolutely rigid barrier walls lacking any entry/exit openings, the room surfaces are being excited into sympathetic resonance with each of the multiple and ever changing musical tones. Every surface may be contributing another fundamental frequency of its own AND its subsequent harmonics which may - likely will - be broken down into multiple cavity induced resonances. All of this adds to the complexity of determining which specific frequency has created another sympathetic resonance in any object within the enclosed space. It is what makes the creation of a true anechoic chamber so expensive and so rare.

Though, as far as the end result is concerned, shaking objects with bass is really no different than shattering a wine glass with higher frequencies. Both reactions come down to locating the resonant frequency/frequencies of the object being affected.



Yes, "forcing" an object into reaction requires a substantially large amount of SPL's - however, SPL has little to do with amplifier "power". Which is, after all, my basic argument here.

If the driver can generate 125dB with fewer than ten watts input, that is all that matters when it comes to the issue of SPL's and amplifier "power".

In other words; https://www.youtube.com/watch?v=B2WcBi9mu6A

I can't tell you how many times an audio sales staff member had to explain to customers the commercial wasn't a real world event and they weren't going to get the same reaction if they bought JBL L100's. And that their cassette deck wasn't really the cause of any such reaction within the system.

But, as they say, every woman wanted Bond, every man wanted to be Bond and every home audio buyer thought they wanted JBL's when they came in the store.


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Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18449
Registered: May-04
.

https://www.youtube.com/watch?v=17tqXgvCN0E

Here's one to consider; https://www.youtube.com/watch?v=THUMdTohWkI

If your window panes where flexing, did the resonance pattern of the glass look more like the lowest frequency's water movement or the higher frequency's?

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