Dayton Audio ND65-8 Actual vs Advertised

J

joshk03

Audioholic
So my Dayton Audio speakers just came. They sound horrible with no mids/bass.
So I carefully overlaid my REW measurements over the marketing graph (in purple). And WOW. Am I doing something wrong? I am holding the speaker in my hand a few feet from the microphone. The data confirms what I hear, nothing below 1200hz. Perhaps my Kinter K2020A+ amplifier could be to blame? It's just a cheap amp I wanted to use for an outdoor ambiance speaker.

 
lovinthehd

lovinthehd

Audioholic Jedi
So the Dayton graph was also measured the same way, or at least by holding the driver in your hand a few feet from the microphone?
 
S

shadyJ

Speaker of the House
Staff member
You might want to put that driver in en enclosure of some kind before you measure it...
 
lovinthehd

lovinthehd

Audioholic Jedi
I did peek at the Dayton page, doesn't really specify the conditions it was measured but certainly not held in a hand...
 
J

joshk03

Audioholic
Well it's not sold with an enclosure so the advertised data shouldn't be specific to a enclosure. Holding it seemed to be the most pure way to measure. Since it's just a bare driver for sale.
 
lovinthehd

lovinthehd

Audioholic Jedi
Well it's not sold with an enclosure so the advertised data shouldn't be specific to a enclosure. Holding it seemed to be the most pure way to measure. Since it's just a bare driver for sale.
Probably if you dig into the site they specify a measurement basis, but mounted in an open baffle or enclosure can make a big difference....maybe mounting it into an open baffle would be better than your hand, tho. And measuring from "a few feet" is...why?
 
S

shadyJ

Speaker of the House
Staff member
opposite phase sound coming from the back of the woofer is cancelling out the front firing air waves. You need to mount that driver in an enclosure if you want to measure it, or at least some kind of large baffle.
 
KEW

KEW

Audioholic Overlord
It is pretty bad that they provide a response without at least specifying the box volume and whether it is ported or not!

Josh, your measurements are not surprising for a hand held driver in open air (be it extremely high quality or a POS).
 
J

joshk03

Audioholic
And measuring from "a few feet" is...why?
Because I don't know any better :p Actually it's because I figured that's standard listening distance if it were used on a PC. It's not like this tiny thing is meant do much more.

It is pretty bad that they provide a response without at least specifying the box volume and whether it is ported or not!
Ya, I thought the same.
Josh, your measurements are not surprising for a hand held driver in open air (be it extremely high quality or a POS).
Good to know. Can you explain that more?
 
TLS Guy

TLS Guy

Seriously, I have no life.
Well it's not sold with an enclosure so the advertised data shouldn't be specific to a enclosure. Holding it seemed to be the most pure way to measure. Since it's just a bare driver for sale.
Look, when Dayton sell drivers for enthusiasts to use in speaker designs, they can't possibly fathom that some red neck is going to put a driver in his hand and stick a measuring microphone in front of it!

Now a prudent person would do a period of study to understand at least the rudiments of the physics involved and the basic elements of speaker design before purchase.

It has already been explained to you that the reason for your measurements is cancellation by opposite waves of pressure either side of the cone cancelling. The only frequencies you could measure or hear were because the wavelengths were small enough to be obstructed by the physical dimensions of the cone.

If you had done elementary study you would have known the speaker was measured in a sealed box, because roll off below 100Hz is 12db per octave which is second order.

Now Dayton publish the T/S parameters of the driver, so you can be sure the driver was measured in a sealed box of optimal volume determined by the T/S parameters of the driver. This is so obvious to anyone who should be embarking on a project like this to not have to be stated.

So if you want to duplicate Dayton's measurements you need to build the sealed box as determined by the T/S parameters and install the driver. Then you can measure it.

You can not infer that because it was measured in a sealed box that is the optimal loading.

Really your post is just truly jaw dropping.
 
J

joshk03

Audioholic
That's some seriously misplaced attitude for the "beginners" section of a forum. Did some kid stomp across your lawn today?
 
TLS Guy

TLS Guy

Seriously, I have no life.
That's some seriously misplaced attitude for the "beginners" section of a forum. Did some kid stomp across your lawn today?
Josh, even for a beginner we expect you to summon up more than a couple of neurons and half a synapse.

Now if you want to reset and pose some sensibly phrased questions after a little study of the subject matter I will do my best to answer them.
 
KEW

KEW

Audioholic Overlord
Good to know. Can you explain that more?
opposite phase sound coming from the back of the woofer is cancelling out the front firing air waves. You need to mount that driver in an enclosure if you want to measure it, or at least some kind of large baffle.
So the wave coming off of the back of he speaker largely cancels the wave off of the front mostly at lower frequencies (same fundamental principal as used to cancel noise in noise cancelling headsets). A driver needs a decent sized baffle (the board the driver is mounted on) or box to isolate the back wave so it does not readily interfere with the front wave.
 
DIY Junky

DIY Junky

Full Audioholic
It is pretty bad that they provide a response without at least specifying the box volume and whether it is ported or not!

Josh, your measurements are not surprising for a hand held driver in open air (be it extremely high quality or a POS).
Most Videos I have seen and speaker drivers recommend a air volume for its speaker to preform at it best. And most guys build a quick ugly box to test speaker performance.. never hand held
 
Johnny2Bad

Johnny2Bad

Audioholic Chief
Generally they don't measure in a box, they are measured in an open baffle arrangement ... the speaker is mounted on a baffle of fairly large size, large enough so the backwave doesn't arrive soon enough to affect the direct response with the microphone 1 meter from the driver centreline, and with a fast sweep tone in anechoic conditions.

That's why you see such specifications as "free air resonance" and the like.

Also, mid and high frequencies are not measured the same way as low frequencies, as the wavelength becomes large enough at low frequencies to require a different technique (typically, nearfield measurement instead of 1 meter away) and the two graphs blended. Home speaker builders, not owning anechoic chambers, generally measure outdoors to eliminate room reflection affecting the response.

What happens when you mount it in an enclosure is what those Thiele-Small parameters are for.

If the speaker measured the same while holding it in your hand, with the microphone "some distance" away in a closed room, it would be a miracle.

There is always some unit-to-unit variation in cone drivers, looking at your graphs, the speaker seems to be fine as it tracks pretty closely in the areas where your technique is at least sort-of-correct. You should always break in cone drivers before measurement, they are stiff from the factory in every case.
 
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DIY Junky

DIY Junky

Full Audioholic
Josh, even for a beginner we expect you to summon up more than a couple of neurons and half a synapse.

Now if you want to reset and pose some sensibly phrased questions after a little study of the subject matter I will do my best to answer them.
Josh, You are coming here for knowledge as am I .. When you ask a question take the knowledge and use it to your best ability . There are many here that are willing to share the pebble that you are not ready to grab from the masters hand .. I have learned plenty here and thankful for what has been shared.
 
J

joshk03

Audioholic
Thanks everyone for the info. I thought the rear-ward waves would be constructive, not destructive as long as I made sure to mind the reflections. Clearly that was incorrect. I now understand an open baffle is the assumed configuration Dayton Audio used if they don't clarify.

I started the thread not knowing if my issue was the amp, the speaker itself, my test configuration, or something else. It seems clear now that I just need to fit the enclosure. I built a cement enclosure specifically for these speakers before they arrived, using CAD measurements from the datasheet. However, they didn't fully define the terminal locations... Now the speakers are here and don't fit the enclosure because of it.
Today I will sacrifice a Dremel bit to carve out the cement and make the speaker fit inside. That should improve the mids/bass.
 
KEW

KEW

Audioholic Overlord
Thanks everyone for the info. I thought the rear-ward waves would be constructive, not destructive as long as I made sure to mind the reflections. Clearly that was incorrect. I now understand an open baffle is the assumed configuration Dayton Audio used if they don't clarify.

I started the thread not knowing if my issue was the amp, the speaker itself, my test configuration, or something else. It seems clear now that I just need to fit the enclosure. I built a cement enclosure specifically for these speakers before they arrived, using CAD measurements from the datasheet. However, they didn't fully define the terminal locations... Now the speakers are here and don't fit the enclosure because of it.
Today I will sacrifice a Dremel bit to carve out the cement and make the speaker fit inside. That should improve the mids/bass.
Interesting approach.
That should get rid of any audible cabinet resonance.
I don't know if you did or not, but for optimal result, you would want to size the interior volume to match the speaker parameters (I don't know how that is done). If your slab has a pocket sized just to fit the speaker housing, it would probably restrict motion of the driver (especially low notes) because the small amount of air inside would form too "tight" of a spring (the air has to compress/pull suction for the driver to stroke fully). If Dayton doesn't specify box sizes, ask the guys here and link the data for your speakers and they can sort it out for you!
 
J

joshk03

Audioholic
Interesting approach.
That should get rid of any audible cabinet resonance.
I don't know if you did or not, but for optimal result, you would want to size the interior volume to match the speaker parameters (I don't know how that is done). If your slab has a pocket sized just to fit the speaker housing, it would probably restrict motion of the driver (especially low notes) because the small amount of air inside would form too "tight" of a spring (the air has to compress/pull suction for the driver to stroke fully). If Dayton doesn't specify box sizes, ask the guys here and link the data for your speakers and they can sort it out for you!
The spec sheet does recommend a sealed box of size .02 cu ft. I sized it exact with my Solidworks software. It is a sexy orb like enclosure. The combination of a cement enclosure with quality acoustic insulation should work out nicely. I had my doubts after initial testing, but got the confidence to continue from this thread.
 
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