Advice Needed - Is this a good driver selection?

[Myleso]

Hello!

I want to build my first multi-way speaker (a large portable, ported blutooth speaker) and I would like some advice to make sure im not missing something crucial in my driver selection.

I have been going through the available drivers on PE, looking at frequency response graphs, etc and have come up with this woofer;

Dayton Audio RS125P-4 5" Reference Paper Woofer 4 Ohm
Dayton Audio RS125P-4 5" Reference Paper Woofer 4 Ohm

and this tweeter;

Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter
Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter

I chose these because they have a similar sensitivity and it looks like they can be crossed over nicely. Do you think these will work well together in a portable speaker? Someting like this; DIY Elder Bluetooth Speaker | Build Plans — Kirby Meets Audio

I have attatched thier frequency response graphs

Also, is it much of an issue that the woofer is 4ohm and the tweeter is 8ohm?

Edit: I have just noticed that the sensitivites for the woofer are given differently, one is db2.83V/1m and the other is 1W/1m. Is that a problem?

Thank you!

 

[wintermute]

With an 8 ohm driver, 1W/1M and 2.83V/1M are pretty much interchangeable so the sensitivity comparison between the two drivers should be comparible (since the 1W/1M measurement is on the 8 ohm tweeter).

However the FR graphs don't seem to match up with the sensitivity numbers in the specs with the woofer looking more like 85db sensitivity in the range it would be being used.

One 8 ohm and one 4 ohm driver is not an issue provided the crossover is designed with the individual drivers impedances in mind.

I've no experience with either driver, but just on paper they look like they would work ok together, though there may be a bit of a hole around 3Khz, as both drivers seem to be a bit down around there. Not sure whether the bump in the woofer at around 1.5Khz will need some attention, it may be exacerbated depending on your baffle geometry.

Tony.

 

[Myleso]

Thanks heaps for the quick reply

I just found the 8ohm version of the same woofer so that might simplify some stuff Dayton Audio RS125P-8 5" Reference Paper Woofer 8 Ohm .Looks like it might have a better FR around that 1.5K mark too. You're right about the FR graphs not matching up with the sensitivity specs, I guess I would need to bring the tweeter down a few notches in the crossover to bring it more in line with the woofer?

Cheers!

 

[wintermute]

I'm wondering if the slightly cheaper Dayton RS125-4 might be a slightly better choice for easy of integration for a first crossover design.

Dayton Audio RS125-4 5" Reference Woofer 4 Ohm

See what others chime in with 🙂

edit: yes if sensitivity mismatch is constant then can be dealt with by padding down the tweeter a bit 🙂 If you end up needing baffle step compensation then tweeter padding usually ends up being necssary anywaay even with relatively closely matched sensitivity of drivers.

Tony.

 

[Myleso]

Okay, great 🙂 that one looks like exactly what I am after. Thanks a lot!


How will I know if I need baffel step compensation?

Here is what I got when I put that driver inot a box volume calculator, considering I want this to speaker system to be one unit, should I separete each woofer into its own compartment or are 2 fine in the same enclosure?

Thanks again!

 

[wintermute]

I just realised that this is a mono configuration. Two woofers and one tweeter. In that case you need to decide whether to wire the woofers in parallel or in series. If in parallel you will want to go for the 8 ohm drivers, if in series you will want to go for the 4 ohm drivers.

Provided both drivers are being driven by the same signal then a single box should be fine, but note that you must double the volume for two drivers.

Baffle step is one of those things that depends. It depends on a number of things. The baffle dimensions and speaker position on it, and the distance the speaker is from the wall behind it are the main ones (although distance off the floor can be another). Often around 2 - 3db of baffle step compensation is a good target, but it really depends on how the speaker will be used and the room it is in.

Here is a good article about bafflestep. Baffle Step Compensation note that it takes a line level approach to bafflestep compensation, you can also do it with passive components in your crossover, or even just optimising your normal crossover, sometimes with a bigger low pass inductor.

Tony.

 

[system7]

This is a very similar project in about 12L.

CT MAIN 100

The 4 ohm W 100 S - 4 Ohm looks very similar if a bit less sensitive.

I would think your Dayton DC28F can keep up with the series MTM configuration. By one of those convenient quirks, series wired drivers are exactly the same loudness as a single one.

You can import the FRD frequency response and ZMA impedance into Boxsim: Downloads

Level is adjusted in the simulator to get it right. The 8.2R and 15uF is impedance correction which you might adjust. The LCR on the tweeter is specific to that tweeter and actually doesn't do much. You might just omit it.

 

[eriksquires]

Nice selection. In the same price and highly regarded is the FaitalPRO 5FE120:

FaitalPRO 5FE120 5" Professional Midbass Midrange Woofer 8 Ohm

Pay attention to the sensitivity and maximum power of each. 🙂

Best,

E

 

[adason]

I have used RS125 in my Nola like project, four per side, open baffle, and it turned out to be the best sounding speaker I built so far...

 

[Myleso]

Sweet, Thanks heaps for the help everyone.

I have been thinking of trying to incorporate 2 tweeters in the design. Would this widen the angle of optimal listening? and with the drivers reletively close together, would there be much benefit from running them as stareo?

Those mid/woofer suggestions look tempting, but I am already well over my budget so I don't know if I can justify it. Ill definitely consder them though.

Tell me if I am wrong but in series the 4ohm drivers would become a 8ohm load and this could increase power handling. In the parallel the load would be reduced to 2ohm and the sensitivoty of the drivers would increase. Then the 8hm versonwould be better in parallel to get 4ohm? What would you guys recomend? I like to be able to crank my music right up (Though I know a portable bluetooth speaker may not be great for that). Is better power handleing or more sensitivty better?

I am planning on using either this amp or the 2x30W version Dayton Audio KAB-250A 2x50W Class D Audio Amplifier Board with Bluetooth 4.0


Thanks agian!

Edit: I might just go for mono configuration for simplicity sake

 

[adason]

Two tweeters per box sounds like trouble, unless you know what you are doing. I am not sure I follow what are you doing. If you want mono, just sum the left and right channel electronically, and use one channel of stereo amp and one speaker...but one complete well implemented speaker. Otherwise just do two speakers like normal people do.

 

[Myleso]

Here is a link to a similar sort of project DIY Elder Bluetooth Speaker | Build Plans — Kirby Meets Audio

I am bit confused. Do you mean this sort of thing would be better off as just one woofer and one tweeter? Wouldn't I get far less ouput and power handling?

 

[adason]

One woofer and one tweeter per channel.
So if you want to build something similar to the link you provided, use two tweeters per box, and two woofers of course.
Ideally place the tweeters as far as possible from each other.
Somehow i thought you are building mono system, my misunderstanding.
Btw, in that link you provided, that one tweeter in the middle...that makes no sense.

 

[Myleso]

Okay sweet 🙂 thats the conclusion I came to too.

Yes, one tweeter in the middle seems odd. For some reason he decided to have the woofers in stareo and one tweeter in mono...

Thanks for the advice!

 

[adason]

like this...

 

[Myleso]

Yeah nice 🙂 mine is pretty muchan upscaled version of this