Dayton Audio RS180P-8 - 11l ported enclosure - no bass

[Michael Marmaras]

Hi,

Beginner speaker builder here looking for some help.

My current goals is to build a decent 2-way speaker for my workshop, one that fits the limited space available. The speaker will be almost against the back wall.

The woofer is a new Dayton Audio RS180P-8.

Enclosure: already built so I could have some woodworking exercise. Ported. Internal net volume is 11,2l. Box is tuned to 49Hz. I did an impedance sweep (DATS v3) and the enclosure is pretty much tuned to this frequency. Leaks should be limited, it all fits nicely and is glued together.

Ports: two 1’’ vents, each 7,5’’ long, on the front.

View attachment 1076015

My first problem now is that low frequency response is terrible. Very little low-end bass sound. Even when hooking up the woofer directly and playing frequencies like 60hz, there is definitely missing something.

I recently also built a much smaller cabinet with a DSA135-8 with a rear bass reflex port, and it has a much better low end sound. So it’s not that I’m unrealistically expecting subwoofer-like bass.

One difference I can think of is that in this build I have two plastic bass-reflex tubes, and the DSA135-8 build has a rectangular MDF port, which is more stiff. The plastic tubes in this build aren’t that rigid, I don’t know if that’s important.

So my hope now is that there is a major design flaw with what I built. Thanks for any hints that put me on the right path again. I'm a bit stuck here.

Vincent

Did you use a pipe attached to the vent holes. That is very important to tune the cabinet to design expectations. You might even need to use an elbow 90 if it comes too close to the back. Not too late to add but will definitely improve the low end Michael

 

[Michael Marmaras]

WinISD has a setting that computes the size for two port tubes. Make sure you are using that setting when doing the calculations. If you just use two of the ports that were computed as a single tube, the result will be off. That is an exceptionally good 7" driver and it has distortion nearly as low as the very much more expensive Seas and Scanspeak drivers. I have only used it as a lower midrange paired with a 12" woofer. It operates as a perfect piston up to around 800Hz.

Agree that the driver specs look really good for the price.save $ and great quality too. Love Dayton for overall value! Michael

 

[Vinne81]

Can you post the individual measurements for near field port, near field driver and far field driver in .FRD, please? What are the baffle dimensions and mic distance in these instances?

It would be interesting to sim the baffle and make a simulation of output and see where they differ.

Is there any stuffing in the cabs, by the way?

PS. I agree with Mike, the blue far field measurement does show some consistencies with other measurements.

I have included the original measurements, without changing the dB of any measurement nor compensating for baffle step in the nearfield measurements.

Nearfield woofer is measured as close to the phase plug as possible without the driver touching the microphone. Port is measured just a tiny bit inside the port until where the flaring ends. I used an IR window on the woofer farfield.

Baffle dimensions: 32cm high, 22cm wide. Mic distance is 100cm.

Padding: there is "Sonic Barrier 1/2" Acoustic Damping Foam" on the bottom and on the back panel.

To match the port and woofer nearfield. The woofer is 126.7 cm². The ports are 3.6cm diameter, so 10.18cm². I'm not exactly sure about the formula, but I used this one: 20 * log ( sqrt (10.18/126.7) ). Result is -10,95dB. I have two ports, so +6dB, total adjustment would be -4,96 dB for the port?

Thanks for looking into this!

 

[Vinne81]

Did you use a pipe attached to the vent holes. That is very important to tune the cabinet to design expectations. You might even need to use an elbow 90 if it comes too close to the back. Not too late to add but will definitely improve the low end Michael

Yeah it's a piece of PVC pipe, and I have joints so I can still change the tuning. Imo the vents are too short at this time, I will probably try lower tunings as soon as I understand what's abnormal about the 500-700Hz range. In a new enclosure I would of course just use a longer piece of plastic, but the cabinet is already glued and I can't replace the entire pipe by a longer version. Whoops

I've read some more and I think that maybe it's normal to have a frequency response like I do. My baffle size would indicate a rise in dB around 600Hz and with the gated measurements I lose any wall gain for those lower frequencies.

 

[grahamgraham]

Cheers for these, I'll have a look tonight when I'm back from work. TBH it doesn't seem like there's an awful lot wrong except for the port resonance isn't controlled, the tuning is high and there could be more stuffing to iron out port res an internal reflections? Accurate measurement is the keystone though so let's get a clear picture first.

 

[Vinne81]

Lovely, thanks.

I'm probably thinking about this too much as a science, where if you do everything a certain way and follow a pre defined process, that you will get perfect results. While in reality, nothing is perfect: not the drivers, not my room and not my enclosures. And then there's personal taste

 

[waxx]

You can tune it lower, but the cabinet needs to be double the size for that in a reflex. I did the sim and got into the low 40's like that. The 11L will only work way higher and will need a subwoofer. The bigger cabinet could be without for nearfield listening.

 

[Michael Marmaras]

Yeah it's a piece of PVC pipe, and I have joints so I can still change the tuning. Imo the vents are too short at this time, I will probably try lower tunings as soon as I understand what's abnormal about the 500-700Hz range. In a new enclosure I would of course just use a longer piece of plastic, but the cabinet is already glued and I can't replace the entire pipe by a longer version. Whoops

I've read some more and I think that maybe it's normal to have a frequency response like I do. My baffle size would indicate a rise in dB around 600Hz and with the gated measurements I lose any wall gain for those lower frequencies.

Though you probably did use pipes but the pictures did not look like there was any.. I agree with Waxx that a lot larger cabinet would get !ore out of those drivers. Maybe you can get a thin walled pipe to fit in holes if enough length left on depth.. If not maybe some flexible tube to angle around back of cabinet. Just a thought.. Michael

 

[Michael Marmaras]

Though you probably did use pipes but the pictures did not look like there was any.. I agree with Waxx that a lot larger cabinet would get !ore out of those drivers. Maybe you can get a thin walled pipe to fit in holes if enough length left on depth.. If not maybe some flexible tube to angle around back of cabinet. Just a thought.. Michael

Or lengthen out front since just using in shop.

 

[Vinne81]

One more thing about combining the port and woofer nearfield. I tried different formulas, but it always seemed like the port output was still way too high for the woofer. I now tried combining visually in the low rolloff and the combined response seems more realistic.

Baffle step effects are also first applied before splicing near and farfield.

This response probably looks ok.

 

[Michael Marmaras]

One more thing about combining the port and woofer nearfield. I tried different formulas, but it always seemed like the port output was still way too high for the woofer. I now tried combining visually in the low rolloff and the combined response seems more realistic.

Baffle step effects are also first applied before splicing near and farfield.

This response probably looks ok.

View attachment 1081903

Pretty drastic over 600 but really nice low end. Might consider using an easy to use midrange. Many good ones at decent prices. Would smooth everything out with a fairly simple inexpensive x over. Might not even need a tweeter as good midranges can sound sweet up top unless you are a top end critical listener. Seas are my favorite mid but pricey.

 

[Vinne81]

Pretty drastic over 600 but really nice low end. Might consider using an easy to use midrange. Many good ones at decent prices. Would smooth everything out with a fairly simple inexpensive x over. Might not even need a tweeter as good midranges can sound sweet up top unless you are a top end critical listener. Seas are my favorite mid but pricey.

Yes the 600hz and onwards peak is a problem. I'm hoping that wall gain will fix some of that, and my crossover should do some more. I already have a tweeter but I like the idea of using a midrange without a tweeter! I can always build more boxes.

I'm definitely not a top end critical listener I'm more of a guy that likes woodworking, but doesn't like furniture so building speaker enclosures is what I do. I don't even need new speakers

 

[Michael Marmaras]

Yes the 600hz and onwards peak is a problem. I'm hoping that wall gain will fix some of that, and my crossover should do some more. I already have a tweeter but I like the idea of using a midrange without a tweeter! I can always build more boxes.

I'm definitely not a top end critical listener I'm more of a guy that likes woodworking, but doesn't like furniture so building speaker enclosures is what I do. I don't even need new speakers

You might try selling some of your creations. Your pictures indicate quality work. Since your good at cabinet building consider a more complex build like a transmission line ,horn ,or Voigt designs. Many more. Have fun above all.

 

[grahamgraham]

So, I had a look and merged all the files and got pretty muc the same reponse as you. I used VituixCAD to simulate the effect of the baffle on the near field combined measurements then merged it with the far field.

Anyway, now I look at it in the way I would my suggestion is that the effect of severe peaks in the port resonance combined with possible internal reflections is effecting the driver far field output. I went nuts trying to make the perfect cabinet earlier this year (which owing to me forgetting a golden rule I started out with a flawed geometry and had to put fires out as I went) and went through this.

Below is the vent/port and merged far, near and baffle measurements. Clearly there is great tumultuousness in the vent measurement between 500-1500hz. You need to damp these, one way or another. Vents don't just show what they are doing but can be a good window in to what else may be going on inside a cab. ~600hz and ~1200hz peaks/troughs are specifically a problem.

In my project I had the same issue: https://www.diyaudio.com/community/threads/10-cd-horn-2-way.375829/post-6930305

Here are the two measurements of the vent before and after dealing with the port resonance and poor cabinet geometry:

Here are two measurements of the driver and vents merged. I'll let you guess which of the above correlates to which of the below but here's a hint, they're the same colour

Obviously, your box is too small to get the full extension from this driver but you know that so it hasn't been the focus for me. My advice is to stuff and measure.

Hope this helps and I'm happy to be told I'm wrong

 

[Michael Marmaras]

So, I had a look and merged all the files and got pretty muc the same reponse as you. I used VituixCAD to simulate the effect of the baffle on the near field combined measurements then merged it with the far field.

Anyway, now I look at it in the way I would my suggestion is that the effect of severe peaks in the port resonance combined with possible internal reflections is effecting the driver far field output. I went nuts trying to make the perfect cabinet earlier this year (which owing to me forgetting a golden rule I started out with a flawed geometry and had to put fires out as I went) and went through this.

Below is the vent/port and merged far, near and baffle measurements. Clearly there is great tumultuousness in the vent measurement between 500-1500hz. You need to damp these, one way or another. Vents don't just show what they are doing but can be a good window in to what else may be going on inside a cab. ~600hz and ~1200hz peaks/troughs are specifically a problem.

View attachment 1082113

In my project I had the same issue: https://www.diyaudio.com/community/threads/10-cd-horn-2-way.375829/post-6930305

Here are the two measurements of the vent before and after dealing with the port resonance and poor cabinet geometry:

View attachment 1082124

Here are two measurements of the driver and vents merged. I'll let you guess which of the above correlates to which of the below but here's a hint, they're the same colour


View attachment 1082125

Obviously, your box is too small to get the full extension from this driver but you know that so it hasn't been the focus for me. My advice is to stuff and measure.

Hope this helps and I'm happy to be told I'm wrong

Last fr graph looking pretty good. Some midbsss boost is. What alot of people like , better than dip there.

 

[Michael Chua]

Can you post the individual measurements for near field port, near field driver and far field driver in .FRD, please? What are the baffle dimensions and mic distance in these instances?

I didn't do a nearfield or a port measurement. However, here's a RS180s-8 with nearfield spliced in.

The RS180p-8 nearfield will look similar.
Baffle width for RS180P-8 is 8.5". Box volume is 13L. Mic at 1 meter.
Stuffing is 2" construction wool.
Here is the FRD.

 

[Michael Chua]

That 5 k might be corrected with a notch filter? Bottom looks funky. Try it in a Voigt design since it's darn good to10 k. Just supplement with the same tweeter. Bass in these designs address resonance and usually have solid and more important natural sounding Michael

I didn't have to use a notch filter for this design. The tweeter is the Morel CAT378.

This is the Summed Response.

Below 500Hz is no longer "gated". It includes the room reflections.
The big chunk missing at 100-150Hz is a notch caused by a floor reflection.
You'll get this with the speaker 1 meter from the floor.
Measurements are in 4pi.

This design is just to listen to the RS180P-8. I did not apply any BSC.
Even if I did, the music will still lack bass.

I've never done any work with the Voigt design. Don't really know how the bass sounds like.
What I did with this RS180P-8 with the CAT378 is to add in a bandpass subwoofer.
So, basically, the RS180P-8 / CAT378 is a satellite.
Used that way, the mids and highs are pretty good.

If I want to really do a 2-way, I will have to tune the port lower to about 50-55Hz, add some BSC and use active Bass EQ to boost the bass.
The bass should sound tight and with great attack. Haven't done it yet though. Too many projects.

Mike

 

[Vinne81]

Here are the two measurements of the vent before and after dealing with the port resonance and poor cabinet geometry:

View attachment 1082124

Here are two measurements of the driver and vents merged. I'll let you guess which of the above correlates to which of the below but here's a hint, they're the same colour


View attachment 1082125

Obviously, your box is too small to get the full extension from this driver but you know that so it hasn't been the focus for me. My advice is to stuff and measure.

Hope this helps and I'm happy to be told I'm wrong

Impressive, you had a similar problem AND solved it Very nice, also nice display of skills on your own speakers.

Farfield for my closed box isn't much better than the bass reflex.

• Bass-reflex enclosure, internal: H284 * W184 * D244. Damping on back and bottom.
• Sealed enclosure, internal: H280 * W172 * D100. No damping material.

So height and width are very similar. Would this suggest that the box dimensions are the culprit? There are no port resonances in my sealed enclosure, but still it looks bad.

I'll start with my sealed enclosure, stuff it and see what the measurements tell us.

 

[grahamgraham]

Stuffing could be the critical factor here. As Mike and I have done, a 2"/50mm lining of insulation material on the back and all sides (excluding back of baffle) will definitely have an impact on response.

Otherwise a heavy stuffing of polyfill will also do something but it can be harder to keep it from interfering with your bass reflex system as it can end up limiting port output.

Stuff-measure-stuff-measure!

 

[grahamgraham]

I did also wonder if the inside of the driver aperture was bevelled/relieved at all? With 18mm mdf I cant imagine it will have a huge impact but its another point of tweaking.