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post #1 of 6 Old 01-11-2020, 11:45 AM - Thread Starter
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Newbie : What Speakers to match new Amp

Hello
I am a total newbie here with little understanding of matching speakers and amps. I have recently bought a cheap amp which has the following listed as part of its specs. I am not able to understand the rating of the passive speakers that I should be looking to match with this amp. I am considering to buy not so expensive but surely decent quality of speakers online (2 channels, so two speakers) and then make house them in a DIY wooden box.

Here are the specs from the amp:


Description:

Item name: Amplifier

Vocal tract: 2.0 vocal tract

Signal-to-noise ratio: 75 dB

Interface type: RCA

Model: lepyA7 Bluetooth

Receiving mode: infrared and FM Bluetooth

Applicable crowd: the public

Supporting APP: Not Supporting

Size: 15.90 x 11.00 x 4.60 cm

Input voltage: DC12V 5A

Amplifier type: amplifier

Material: Aluminum alloy

Appearance material: aluminium alloy

Distortion rate: 0.01%

Rated frequency: 20-20 khz

Impedance: 4-8

Signal-to-noise ratio: 85dB

High control: 12dB + 10KHz

Bass control: 12dB + 100Hz

FM: 87.5MHz-108.0MHz

Signal level: 220MV 47K

Output power: RMS 20W + 20W 1KHz

Harmonic distortion: <0.05%1KHz

Support: USB/TF/SD/card and AUX input

Jacket input: standard stereo jack

Card reader/U disk format: MP3 FM

Stage or not: HiFi

Weight: 0.3kg

Packing list:

Amplifier*1

Instructions*1

Remote controller *1

Thank you!!!!
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post #2 of 6 Old 01-11-2020, 12:55 PM
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Quote:
Originally Posted by karan23 View Post
Impedance: 4-8
Thank you!!!!
Find speakers that advertise to be in between the 4ohm and 8 ohm.
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post #3 of 6 Old 01-11-2020, 10:07 PM - Thread Starter
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Thank you @Trimlock !!

What about the wattage listed. I get that the impedance is more important but I also read that in some cases the speakers burn out or the amp circuitry. So, would you reckon a pair of these speakers fit for purpose?




Type (Inches) : 4" Coaxial Speaker Type (mm) : 100mm
Power Handling, RMS : 22W (RMS) Power Handling, Peak : 140W Frequency Response : 80 Hz - 15k Hz
Nominal Impedence : 4 ohms Sensitivity ([email protected]) : 85dB Crossover : None Controls/Adjustments : None
External Diameter : 4" (102.5mm) Mounting Cutout Diameter : 3-3/4" (94.6mm) Mounting Depth : 1-9/16" (39mm) Grill : no


You rock!
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post #4 of 6 Old 01-11-2020, 10:09 PM - Thread Starter
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Thank you @Trimlock !!

What about the wattage listed. I get that the impedance is more important but I also read that in some cases the speakers burn out or the amp circuitry. So, would you reckon a pair of these speakers fit for purpose?




Type (Inches) : 4" Coaxial Speaker Type (mm) : 100mm
Power Handling, RMS : 22W (RMS) Power Handling, Peak : 140W Frequency Response : 80 Hz - 15k Hz
Nominal Impedence : 4 ohms Sensitivity ([email protected]) : 85dB Crossover : None Controls/Adjustments : None
External Diameter : 4" (102.5mm) Mounting Cutout Diameter : 3-3/4" (94.6mm) Mounting Depth : 1-9/16" (39mm) Grill : no

The RMS is 22W but the peak is 140W which has me confused if this is adequate or may burn out.

You rock!
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post #5 of 6 Old 01-11-2020, 11:26 PM
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The Lepy / Lepai LP-A7 is basically this amp with extra input/output crap thrown on it. It will put out 8-10 wpc max, with rather crud S/N numbers.

Karan, the project you describe sounds like a Sprite or similar boombox / bluetooth speaker. I would not expect much out of this amp and using two fullrange drivers will keep the cost reasonable. You could do a C-note or Overnight Sensations kit but the speakers will be capable of much better sound than the amp can provide. The Parts Express website / forum will have other options.
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post #6 of 6 Old 01-13-2020, 11:59 AM
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Quote:
Originally Posted by karan23 View Post
Thank you @Trimlock !!

What about the wattage listed. I get that the impedance is more important but I also read that in some cases the speakers burn out or the amp circuitry. So, would you reckon a pair of these speakers fit for purpose?




Type (Inches) : 4" Coaxial Speaker Type (mm) : 100mm
Power Handling, RMS : 22W (RMS) Power Handling, Peak : 140W Frequency Response : 80 Hz - 15k Hz
Nominal Impedence : 4 ohms Sensitivity ([email protected]) : 85dB Crossover : None Controls/Adjustments : None
External Diameter : 4" (102.5mm) Mounting Cutout Diameter : 3-3/4" (94.6mm) Mounting Depth : 1-9/16" (39mm) Grill : no

The RMS is 22W but the peak is 140W which has me confused if this is adequate or may burn out.

You rock!



Ignore "peak" ratings on audio gear. This sounds like car audio gear, which is VERY typically advertised with peak power, though some low-end home audio stuff is advertised that way too. Using car audio speakers in the home is generally OK as long as you have a box that works for the speaker. Speakers for car doors tend to be designed with a specific Qts, Vas, Fs, and may not be ideal to put into a box for home audio usage. But you would still be able to make them work and if your box design is decent, they might even sound OK.

Speakers have limits on how much electrical power they can take before the coil burns. They have limits on how much the cone can move before it hits a mechanical limit. And they have a certain sensitivity rating, which means they put out a certain amount of volume for a given input. This depends on the box they are in also.


You actually don't need to match power ratings directly, but you do need to make sure that both the amp and the speakers are up to the task of what you want to do with them, which mostly means how much bass you want and how much overall volume you want. You do need to make sure your amp can deliver the power your speakers need to get to a given volume. You do need to make sure your speakers can handle that much power and that they can physically move enough air (without hitting the frame of the speaker) to get the volume you want. There is no replacement for displacement.


If you want 90dB of output at 1 meter and your speaker system (meaning your speakers IN THEIR BOXES) is rated for 80dB at 1 watt at 1 meter away, you would need about 10 watts to get 90dB of output. Your speakers thus must be rated to handle that 10 watts, and they must also have enough excursion to reproduce the sound. How much excursion they need also depends on what box they are in, and what frequencies you send. Lower frequency needs more extension.


You could have a 1000w amplifier, but you could have 50w speakers, and as long as you keep the volume control of your amplifier such that it is sending your speakers less than 50 watts, and you aren't sending small speakers a lot of bass, you shouldn't blow anything.


Some people well caution against "underpowering" a speaker - this means if you had a 100w speaker, and a 10w amp, and you really wanted a lot of output but the amp just isn't cutting it... You crank that amp to maximum, it starts clipping (a type of distortion)... ultimately that type of distortion redistributes the power, sends more of it to your tweeter, and makes it likely to blow. This is not a problem with "underpowering" the speaker at all. It's user error where the user was too stupid to know that making their amplifier distort is bad for their speakers (as well as the amplifier itself).




So, just to end with - those speakers are definitely 22 watt speakers, and are definitely not 140 watts. Let's be clear on this. DO NOT send 140 watts OR ANYWHERE NEAR IT to these speakers.


Also do not send a lot of bass to these speakers (even if you're keeping your total power at or under 22w) because they are small and they probably have a very low Xmax (excursion).




Edit: The best thing to do when you have a small amp is to get the most sensitive and efficient* speakers you can. (* Sensitivity and efficiency are not the same thing but they are directly correlated.) Believe it or not, larger speakers tend to be more sensitive, meaning they tend to put out more volume with the same input power. Many people seem to think that larger speakers need larger amps. It is often the case that larger speakers can take more power than smaller speakers. But what many people don't know is that larger speakers are likely to not need as much power as small speakers.

Last edited by DonoMan; 01-13-2020 at 12:21 PM.
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