Re: RBR discussion thread

[Bob in Tucson]

Jed, thanks for taking time to respond. Much appreciated.

The crossover really influences frequencies above the bass range. It is there to provide the right amount of baffle step compensation and sum the drivers to a flat response on and off axis. That part is done for you. Keep the baffle width and driver orientation relative to the top edge the same to maintain the same diffraction properties that were measured.

That said, if you want to try a different box, keep the box volume the same and port out the bottom or use an elbow for the port tube so that the entry is about 2.5" away from any wall.

[Clearwave]

Jed, thanks for taking time to respond. Much appreciated.

You're welcome and enjoy the kit!

Jed

[psound]

Hi, I think a closer match is the PE cabinet with 8X20" baffle. There you wouldn't really have to change much at all with the current design.

Hi Jed,

Thanks for the quick answer, and the great plans and work with Madisound to provide such a nice kit! I personally love the sound of the scanspeak revelator line, but am somewhat limited on space and/or budget so this really fits the bill. Now, with the PE cabinets, I can have my cake and eat it too regarding WAF.

The baffle you mentioned fits the 0.75" PE cabinets (they claim 0.788 cu. ft. net internal volume, ~22.3 litres). I recalculated the volume of the enclosure you designed taking the bracing into account and it is just a shade over 22 litres, so this seems to be an amazing coincidence. In a separate thread, I saw that you suggest reinforcing a the braces and/or a few other points and using vinyl and/or sonic barrier with these cabinets. Being that I'm not situated in a place where I can build my own cabinets, these may be an ideal solution for me.

[Clearwave]

Hi, I think a closer match is the PE cabinet with 8X20" baffle. There you wouldn't really have to change much at all with the current design.

Hi Jed,

Thanks for the quick answer, and the great plans and work with Madisound to provide such a nice kit! I personally love the sound of the scanspeak revelator line, but am somewhat limited on space and/or budget so this really fits the bill. Now, with the PE cabinets, I can have my cake and eat it too regarding WAF.

The baffle you mentioned fits the 0.75" PE cabinets (they claim 0.788 cu. ft. net internal volume, ~22.3 litres). I recalculated the volume of the enclosure you designed taking the bracing into account and it is just a shade over 22 litres, so this seems to be an amazing coincidence. In a separate thread, I saw that you suggest reinforcing a the braces and/or a few other points and using vinyl and/or sonic barrier with these cabinets. Being that I'm not situated in a place where I can build my own cabinets, these may be an ideal solution for me.

Regarding the PE cabinet-- you can get away with some sonic barrier dampening materials to make it pretty dead. They have since improved the cabinet since I last posted that comment. It used to have a very big dado around the perimeter of the baffle to accommodate the mounting for the removable baffle. If you get a pair with that dado cut, just fill it with hot glue or epoxy. The rest of the cabinet is pretty strong, but a little extra glue where the bracing is can help as well.

Thank you for the kind words. Good luck with your build as well. I doubt the tiny bit more diffraction you get with the PE cabinet will be a problem (there is only a half inch difference).

Regards,

Jed

[Scudfly]

My hats off to ya,Jed
That ScanSpeak system is off the hook.I've built several systems over the years and i got to tell you this one is the best to date.When i heard madisound was offering this for 399.00 with you as a designer i could'nt pass it up.I've only read good things about these ScanSpeak drivers over the years and i have to say they live up to everything i heard.Thanks Again for all you do. Now to build the sealed system for the studio.

[Clearwave]

My hats off to ya,Jed
That ScanSpeak system is off the hook.I've built several systems over the years and i got to tell you this one is the best to date.When i heard madisound was offering this for 399.00 with you as a designer i could'nt pass it up.I've only read good things about these ScanSpeak drivers over the years and i have to say they live up to everything i heard.Thanks Again for all you do. Now to build the sealed system for the studio.

Wow... thank you so very much for the kind words!

[Scudfly]

In the process of making the stands for these speakers i will be putting the tweeter at around 41".Would this be an acceptable height?

[Clearwave]

In the process of making the stands for these speakers i will be putting the tweeter at around 41".Would this be an acceptable height?

When you sit at your listening chair, the optimum location is a tweeter level with the ear. If it is a couple inches off I wouldn't worry about it too much.

Jed

[juanito]

Hi,
I've just got the kit from madisound for 377 USD. Hopefully, I'll get it next wednesday as my brother will bring it from US. I was lloking for DIY kit 2 way useing 15 cm woofers, in a compact box. At that price for the woofers it's more than worth here in Europe. Just the 4 drivers here cosst about 500 Euros, wich for you would be more than 700$. I will eventually upgrade the crossover, but for now I want to play with it a bit, and see later the diferences. Also I can compare with my actual DIY speakers useing SS 2905/9700 and SS 18W/4531. The woofers should sound similar in quality??

Apart from all this, and being very happy with my new audio "adquisicion", I would like to ask about the cabinet construction. My ideal cabinet would be something between the two designs from clearwave. Something compact, but ported with bass extension. The ported cabinet looks great, but the dimensions that it's configured, will make it a bit dificult to place in an average "spanish" room. A floor stand speaker would be more handy for my needs, and getting full bass.
I read something about it in this same thread, but I can't understand it clearly. So, by remaining the same volume and front wall baffle width would be okay?
Do you suggest any other cabinet enclousures for this kit, like double bass reflex, diferent dimensions with same volume, or something between the two "official" designs??

Is there a way to make this kind of port?:
http://www.hifisound.de/oxid/oxid.php/sid/dfa9117aab73af996eeed8d2fb9fc7e6/cl/details/cnid/c8f412f04c883fb39.21504575/anid/c8f412f122918d340.17568302/ETON-ETONA-IV-SPEAKER-KIT/
This is how my actual speakers are, but with the other drivers and in 24 litre box.

Another issue will be the amplifier to mach the speakers, but that will come later (much later). I'll try them first with my actual diy solid state amplifier, and see what.

Thanks for the help.

bye,

[Clearwave]

Hi,

The RBR was designed the optimize the bass response and make it as flat as possible given its TS parameters. So, the sealed box results in a Qtc around .7, which is nice for integrating with a sub, and should have a nice full sound with a gradual roll off into the low frequencies. It is also a nice compact enclosure.

So, to answer your question, if you wanted a smaller ported box, the nature of this particular driver would result in a boomier bass because of the relatively high Qes of the driver. I don't recommend it but you could certainly model the TS parameters and experiment with a smaller ported box. Do a quick search for "unibox." It's a good program that accurately will calculate the bass response and how different port lengths can be used to adjust the response.

I just want to emphasize though that the ported box I used extracts the best bass performance. A smaller box won't go as low either. It may make the sound muddy in the lower mid/bass.

Jed

[juanito]

Hi jed, thanks for response.
May be i didn't express clearly the point. Sorry.
It's the external measurements of the box what i would like to change, not the volume.
So, if box is 7,5 x 20,5 x 14,5 inches, and I maintain 7,5 width, but change to 28/ 29 inches high and 10,5 deep, would it be critical? Or would affect much the whole system? I take these measurements after converting from cm and litres, but is more or less equivalent and states the issue. It maintains the same volume of ~ 35 litres.
This would do a floor standing speaker look. The port tube then, could be the same length but with an elvo/ corner.

I'm not an expert or enginier, i take this as a hobby and also enjoy music. At the mean time its impossible to understand programs to calculate ports, boxes etc. But still, i put interest as much i can inside my limitations. I'll apprecite much your help. Thans in advance for the whole kit, design, forum, web... And all efort you and madisound do to make thid diy world more and more accesible to every one.

Bye

[Clearwave]

It's the external measurements of the box what i would like to change, not the volume.
So, if box is 7,5 x 20,5 x 14,5 inches, and I maintain 7,5 width, but change to 28/ 29 inches high and 10,5 deep, would it be critical?

That's fine, just put a partition in the box to make the same volume that the woofer would see (about 22liters). Make sure the tweeter and woofer is the same distance to the top edge.

[Chrismoris]

I was wondering if it is advisable to use the RBR in a ported version as a near field studio monitor? I have recently started making my own music on the computer and being a DIY enthusiast was wondering if these speakers would serve me well for this application. I really don't want something that makes the music sound better or worse than it is, just trying to get a good clear sound, nice stereo image, and reveal possible issues in the track. I do not listen to music loud at all, but at times it might need to get moderately loud, would 82dB/W be sufficient, I am assuming so in a near field studio monitor setup - just wanted to get a confirmation (I currently listen through 100dB/W 1970's Sansui SP-3500's so I don't really have a good grasp on how loud or not 82dB/W is).

Additionally, I am interested in using the parts express boxes as well. Am I correct in stating that these are the ones suggested?

http://www.parts-express.com/pe/pshowdetl.cfm?&DID=7&Partnumber=302-736&ctab=1#Tabs

If so, I started to lay out in CAD the dimensions for the components to make sure that they would fit the box. I came to the conclusion that if a 5.5" distance between bottom of box and center line of flare is maintained that it will hit the back of the woofer. As depicted here:



Would it be an acceptable solution to reduce the distance to 3.5" as pictured here:



Sonically would this create problems? Should other dimensions be modified or a larger diameter flare tube used? The distance betweene nd of flare and front of box would only be ~1.78-2" is that sufficient room for the air to flow as desired? Lastly, is there any particular place the sound absorption material should be placed in this new box?

Thank you immensely for the help!!! I cannot stress enough how much I appreciate your work as a DIY enthusiast. =]

-Chris

[Clearwave]

Hi Chris,

Thank you for the kind words.

It's the MTM .75ft3 box that I recommended because it is close to the same size as the cabinet I used for running the tests. I recommend listening at 1+ meters for the best driver integration. The RBR gets plenty loud enough for most rooms.

Jed

[Chrismoris]

Ahh okay, thanks for the reply. So you do not advise using the .75cuft box I linked in the configuration above (or is there really no way of knowing, besides testing, how such a change would effect the sound quality)? Do you recommend this kit as a studio monitor or do you suggest that I buy something else such as a Mackie, Alesis, etc. brand name monitor.

Thanks!

-Chris