My turn to build JC's DBB

[Rudy81]

Thanks Mike. The DBB's are very nice and I am still very pleased with the bass. The biggest surprise for me was the HUGE improvement on two channel soundstage. Those P. Audio horns and drivers are exceptional. I have been listening to the new setup and have not once missed the Khorns, no disrespect to the venerable Khorn, I just seem to like this sound much more. The soundstage is just blowing me away and that was an unexpected improvement in the overall sound.

The DBB bass is very powerful and well defined. I have yet to have time to do some more measurements on the setup. I want to spend some more time measuring the bass response of the cabinets in the room.

[kg4guy]

Good price on woofers for this DBB build . http://www.crispdeals.com/EMINENCE_KAPPALITE3015LF_p/kappalite3015lf.htm

[Ironsave]

Rudy,

I just spent 30 minutes reading this thread from beginning to end......

WOW!!!!!

That is a beautiful set of speakers you have built. I am stunned by the media room pic.

Thanks for a great thread; Congrats on the build; I am most envious......

-Iron-

[Rudy81]

Rudy,

I just spent 30 minutes reading this thread from beginning to end......

WOW!!!!!

That is a beautiful set of speakers you have built. I am stunned by the media room pic.

Thanks for a great thread; Congrats on the build; I am most envious......

-Iron-

Iron, you are very kind, thank you. The credit really goes to all the folks who helped me along the way in terms of the active setup, wood working tips, top section selection and of course, JC for allowing me to use his plans. He also had to put up with many questions during the build since it was my first attempt at building anything like this. I am very happy with the result. The sound is extremely good and is a very good fit to my Klipsch side and rear effects speakers.

As I have mentioned many times before, I am still blown away by the sound of the top section. These DBBs pump out some bass. I have yet to have enough free time to run some tests on the bass bin, but plan to do so in the near future.

This was a very worthwhile project and I loved the process as much as the final product.

[SkyDover]

Very Nice!!

The horn does sound very good and goes down to 400hz. I'm using the same horn in my cornscala (super c walls) that I built from this website, copied design from Catbo. I cross mine at 400hz.

I'm using the Goldwood GM-450PB horn which is identicle to the P.Audio PH-4525 horn. It's really made by Goldwood and

relabled as P.Audio. If you get it in the Goldwood it's half the cost P.Audio charges.

Goldwood:

http://www.parts-express.com/pe/pshowdetl.cfm?&DID=7&Partnumber=270-204&ctab=1#Tabs

P.Audio:

http://www.usspeaker.com/paudio%20ph-4525-1.htm

[Rudy81]

SkyDover, are you saying Goldwood makes the horns for P. Audio?

[SkyDover]

Yes, it's an OEM product, much of the industry is such these days. You never know who really makes what anymore! Goldwood makes that particular horn, P Audio doesn't make all their products, comes from different vendors of what they want to offer/carry.

[psg]

Here's the whole enchilada. All in all, it turned out well for my first cabinet build. This picture doesn't do the HT justice. That screen is 10' diagonal and the room is 20' wide.

Simply amazing! That's what I want!

[Rudy81]

SkyDover, wow, I paid at least double for the P. Audio stuff. The driver is the retail version of the Klipsch OEM K69....very nice driver. I love it.

Live and learn.

[Rudy81]

psg, I've done most of it myself in order to save money where I could. It has been several years in the making, but it is pretty nice right now. That was my third screen and the best to date. Some things like the projector are now 1/10th the price I paid for mine. The price of early adoption.

[KdAgain]

Yes, it's an OEM product, much of the industry is such these days. You never know who really makes what anymore! Goldwood makes that particular horn, P Audio doesn't make all their products, comes from different vendors of what they want to offer/carry.

SkyDover,

Do you know of a cheaper version of the 2" driver that Rudy used, the P Audio BM-D750?

Sorry Rudy for taking this OT - perhaps I should start a new thread.

Thanks,

Rod

[Rudy81]

Rod, no worries. This is as good a thread as any.

[DrWho]

Do you know of a cheaper version of the 2" driver that Rudy used, the P Audio BM-D750?

I'm not SkyDover, but what's the application? There are plenty of other cheaper drivers that should yield similar bandwidth at the expensive of a little extra distortion.

Also, does it need to be a 2" driver?

[KdAgain]

Do you know of a cheaper version of the 2" driver that Rudy used, the P Audio BM-D750?

I'm not SkyDover, but what's the application? There are plenty of other cheaper drivers that should yield similar bandwidth at the expensive of a little extra distortion.

Also, does it need to be a 2" driver?

Dr. Who,

Thanks for your interest. I'm putting my response in Rudy81s thread on the "P. Audio PH-4525 horn and BM-D750 (aka. K69). http://forums.klipsch.com/forums/p/134856/1402666.aspx#1402666 It seems the appropriate thread for this discussion.

Rod

[Rudy81]

BTW, I finally had a chance to take some better pictures and rework my web site to reflect all the latest changes.

If you are interested in the final product, or any of the mods I had made to my khorns, you can find it here: http://www.prontoweb.com/klipsch_HT.htm

[SkyDover]

KdAgain,

There are cheaper versions out their with different power ratings, etc. in the 2" drivers, quite a few selections coming from China. The trick is to find out who carries them! Ningbo Dowell, ASM, Shunda Electronics, etc. offers compression drivers that are purchased in lots from companies like Pyle, P.Audio, Klipsch, Cerwin Vega, Pyramid, Marathon, and so many of the designs are very simular and most of these companies do not make their own products, they turn to these China/Asian manufacturers for supplying them their goods. There are alot of offerings that some of these American companies don't carry. Sometimes you can find these compression drivers as a "no name" in house brand from PA Suppliers. I'm not quite sure which Asian manufacturer is making the P.Audio BM-D750/K-69 driver. Sorry I can't be of more help!

To get an idea of the many compression driver offerings from Asia countries you can browse here:

http://www.alibaba.com/trade/search?SearchText=compression+driver&Country=&IndexArea=product_en&fsb=y

[KdAgain]

SkyDover,

Thanks very much for your reply. I took a look at the drivers on the link - boggling the choices. Trouble is it's tough to predict the SQ. So for now, unless someone comes up with a better idea, I'll probably go with Rudy's BM-D750 selection.

Thanks for trying!

Rod

[Rudy81]

I have been living with the DBBs for some time and am really enjoying the result. I finally had a chance to take some more measurements of the finished bass bin and definitely needed to update this thread with the results since they are specific to the bin's performance. A little background is in order before I post the results.

During the last Hope Pilgrimage, I spoke to Dr. Who concerning the bin design and he had noticed in my outdoor plot that there is a prominent dip around 300 Hz. He suggested I play around with stuffing and the geometry of the bin's interior to see if that was an anomaly due to my measurements or a problem due to a standing wave.

My problem was that my speakers are now in my second floor media room and bringing them back down is not going to happen any time soon. Purely by happenstance I was discussing the idea of anechoic measurements with 'nola' at the Pilgrimage as well. He pointed me in the direction of the following paper, which discusses using nearfield measurements as a valid way of approaching true anechoic conditions. The paper is here: http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(1974-04%20AES%20Published)%20-%20Nearfield%20Paper.pdf

I decided to try this type of "nearfield" measurement and I am very impressed with the results. Following are several graphs showing my results. I am attaching my original plot, taken outside for reference.

I would really appreciate Dr. Who and JWC chiming in with their opinions, or anyone else with knowledge of ported enclosures.

[jwc]

My outside curve shows no dip at 300Hz. It was at 150Hz. I was hoping the new port arrangement might rid of that dip.....hmm

http://forums.klipsch.com/forums/storage/6/959349/dbb%2011.jpg

jc

[Rudy81]

This plot is composed of two runs of one of the woofers using the nearfield technique mentioned in the paper. The blue line is the first nearfield run. As you can see, the same dip is present in this run, so it was not caused by any issue with my measurement outside. It seems to me that there is a standing wave or some issue causing that dip. The green line was separated form the blue line so it is easier to see. As you can see in that run, the dip is gone.

I first tried placing a flat board (15"x20"x3/4") behind the woofer toward the back of the cabinet. I tried placing it parallel to the motorboard as well as angled in various directions. Those runs showed that moving the board only moved the dip around. Same dip, different frequencies. I then decided to try Dr. Who's idea and stuck a pillow in the cabinet. The green line is the result of that run. The dip is gone and I show a much better response out to about 900Hz.

I do note that above 1kHz, the response drops off much more precipitously than with nothing in the chamber.

I am currently crossing under 700Hz, so no need to go much higher. So, a few questions.

1) Are there any detrimental effects in sticking a pillow in the bass bins to get rid of the dip at the 300Hz level?

2) Do these plots show what you would expect by adding more fill?

3) Any other suggestions that would handle this issue better?