BEYMA 8BR40/N enclosure advice

[pguerin]

Dear all forum members,

I've bought two beyma 10BR40/N on sales.
The link below advice basse reflex cabinet 40l and 30 hz tuning.

Beyma Speakers - Beyma 8BR40 8" speaker - Beyma 8BR40 100 watt 8" woofer for all hi-fi and studio monitor bass speakers. Beyma 8BR40 and other Beyma 8" speakers here.

I've read that recommended sealed Qts is usually 0.4 and above
and WInISD advice closed box 100l by default.

What are your recommendations ?

The idea is to build a two way monitor with an Audax TW034 crossed at 2Khz.

Best regards

 

[DavidL]

I'd go with the 40L ported box. There are no set rules about what type of box to use depending upon the driver's QT. If it works in the ported box, gives you enough low end and the box size is good for you then that's fine. Have you tried altering the port tuning frequency? Perhaps that 30Hz tuning is a good trade off of slightly elevated bass with a port length you can manage for the box.

Remember that if you want to include BSC, that the 8 inch driver will end up being 3 to 6 dB less efficient and the tweeter will have to match that also with attenuation in the tweeter section of the crossover.

Mating a tweeter with an 8 inch driver is not the easiest thing to do. 8 inch drivers tend to have an off axis roll off that starts earlier than say a smaller driver, so crossing over too high will make the sound change more so when you aren't on axis. I don't see any off axis frequency measurements for the Beyma so can't offer any advice about that other than some other 8 inch designs try to cross over at 1.5 kHz. I'm not sure if the Audax can safely be played that low though.

The Madisound Speaker Store

I do see that the Audax has a rising frequency response on axis which may tend to be "too hot" to your liking. Consider the Seas 27TDFC instead.
Less expensive and flatter response. They can be crossed over at 1.5kHz with an appropriate slope of course.

The Madisound Speaker Store

I am taking for granted that you know how to measure and design a complete speaker, including cross over design and using software to accomplish your goal.

Try reading some of the following for better advice on 8 inch two ways http://www.diyaudio.com/forums/multi-way/190129-8-1-two-way-diy-speakers.html

Dayton Reference RS225

 

[pguerin]

David, Thanks for your advices and your detailled response.

I'm going to build a enclosure laround the design used for the quattro from Troels Gravesen : 30x35x66 around 43 liters internal volume.

QUATTRO

I will use the TW034 because i already own this speaker.
This tweeter can be crossed at 2 Khz with an 3rd order electric crossover producing a LR4 accoustic slope. The rising response can be tamed by a 3/4 dB notch filter at around 10,7 khz. This is the crossover of the Pro 21 classic monitor from Hobby Hifi :

18 db/octave : 6.8 mF + 15 mF and 0,33 mH
Serie RLC notch filter : 5,6 ohms + 2,2 khz + 0,1 mH
LPAD attenuator ~5 dB : 4,7 ohms , 15 Ohms

I will use active crossover for the fist design, i've build a Najda DSP during winter 🙂

I've already done few measures with REW and and an UMIK USB micro.
Used them with PCD and SpeakerWorkshop. So I think that with a little help I can manage to design the crossover both active and passive in a second time.

The main question is how high the 8" can be crossed, with 6Khz specified in the datasheet maybe it's possible to cross it at 2 KHz 😉

I will measure on and off axis the 8BR40 and the TW034 !

 

[pguerin]

I've not build yet the box for the 10B40R but today I've done few measures of the Audax TW034.
18 db/octave : 6.8 mF + 15 mF and 0,33 mH
LPAD attenuator ~5 dB : 4,3 ohms , 0 Ohms (should be 15)
RLC série notch filter is 0.1mH, 1.5mF, 5.6 Ohms