My first Dipole Subwoofer!!!

[chops]

Originally posted by Rudolf
Since I didn´t want to hijack this thread any longer, I have started a new one with almost anything about ripoles I could provide:
http://www.diyaudio.com/forums/showt...432#post568432

Hope I can feed your curiosity
And my apologies to chops who started this in the first place.

Rudolf

Hello there Rudolf!

Please, there's no need for apologies.

In fact, I have a confession to make to everyone.

Almost a year ago, I decomissioned those wonderful diploe subs I loved so much and I still miss them to this very day.

The reason I let them go is the simple fact that they were just entirely too large for my room and were totally destroying the imaging and soundstaging of my main loudspeakers.

I now have an SVS PB12-ISD/2 subwoofer which provides excellent bass all the way down to 12Hz in my room (114dB @ 16Hz) which gives me some spectacular earth moving experiences to say the least! That I can say is one thing those dipoles could never do, at least not to this degree.

On the other hand though, the SVS still doesn't provide the ultimate slam, ultra fast attact and complete open detail of those huge and ugly dipoles of mine.

However, thanks to you I am now very interested in these "Ripole" designs. The good news is that I still have those 15" Pyle drivers and they seem to be acceptable in the ripole designs as well.

I look forward to reading your new thread on this design. Who knows, I might be out in the front yard again soon building quad ripoles!! Not to replace my SVS, but just to play around with.

Also from what I have read so far in the last few posts of this thread, am I to understand that with these ripole designs, lower frequencies can be realised with the same drivers?!

Hmmmm......

[JWFokker]

Here's different T/S specs from a spanish site, including xmax and MMS. How significant is MMS anyway?

FS ( Hz ): 34.8
Qms: 10.735
Qes: 0.602
Qts: 0.602
Vas ( litros ): 93.58
Rms ( N.S/m ):1.599
Mms ( g ):78.15
Cms ( m/N): 2.681 x 0.0004
Diam (mm ): 252
BL ( T.m): 9.263.
Xmax ( mm )6.0

[Rudolf]

Originally posted by JWFokker
How significant is MMS anyway?

Highish Ots and low Fs (as you both want for a dipole sub driver) are somewhat contradicting requirements. The cheapiest way to do it is to raise the cone mass which surely will lower Fs. That way you may end with a heavy cone that is only marginally controlled by a weak magnet.
So a reasonably low Mms is just a proof that some level of quality has been maintained.

[Rudolf]

chops,

yes, you will be able to lower the frequency compared to your "airy" older design. The reduced air volume in front and back of the drivers will act as a "radiaton resistance" - the less air, the more lowering.

If you are going to mount two speakers push-push to get impulse compensation, please do NOT mount them as recommended by Linkwitz. Try to keep the design as symmetrical as possible, because the facing speakers will be coupled tighter by the small air volume between them than in your old design. So both speakers should have the same air volume in front of the cone. Same for the back.

As an optimum the back of the cone should "see" about the same air volume as the front (symmetry here again). Remember that the air "inside" the cone adds to the front air volume and has to be subtracted (together with the basket and magnet) from the back air volume.

Don´t let those Pyles collect rust in some corner.

[Arctophile]

O my gawd, where did my Sunday go? This one one monster thread...but v. interesting.

I got inspired to see what kind of driver I could find here in Oz, and my searching turned up the Pyle PLG15 available for AU$70 (I suspect it's a runout).

T/S Parameters from Pyle site look sweet:

Fs: 26.4Hz
Qes: 0.97
Qms: 3.06
Qts: 0.73
Sens: 90dB
Xmax: 24mm (hmm, suppose they mean 12 each way)


Now my question is this: If I can only afford 2 (both in terms of space and money), is my best bet to go for a U-frame design? My only concern is that distortion might be a bit high given the cut-price construction (compared with push-pull H-frame).

I have read about the N-Frames and Ripols but am too dense to determine which would be the best design for me (to cross over to SL PMTM1-like main panels).

Any advice would be much appreciated,

TIA,

//Adam F

[DougL]

If I can only afford 2 (both in terms of space and money), is my best bet to go for a U-frame design?

For Me, it would depend on how high the target crossover was and how loud and how big.
If its a subwoofer that crossover at 100 or less, I might try a W first. A W is compact, the symmetry cancels some second harmonic distortion and it has minimum room interaction.
If I needed a higher crossover, the U or H would be better.

All 3 could share the same baffles, and its possible to make a "convertible" enclosure that can be either u or H, by removing screws and repositioning the baffle.

Those drivers sound like they were designed for OB use, and I am sure they will be a terrific value.

Good luck.

Doug

[Arctophile]

Thanks Doug, but just to clarify - do you mean that with 2 drivers and a 100Hz xo point I might be better off with one W-frame than 2 separate U- or H-frames?


//Adam F

[johninCR]

When using cheap woofers it's always a good idea to pair them in a push/pull alignment to reduce distortion from imperfections from linear operation of the drivers. You could do this in a WBaffle, Ubaffle, or H baffle, but you'd have a single speaker with both drivers.

An H baffle is just a waste of wood. You can cut off all the wood extending in front of the driver baffle and lose zero bass extension. The only difference is a slight loss of pure dipole dispersion, but not enough for the 2 room modes eliminated by dipole to come into play.

If instead of cutting the wood off, you move the baffle to the front, then you have a U baffle and pick up 6db at the bottom. A Wbaffle is a great idea as long as you are staying below 100hz or so, because you cancel the mechanical vibrations as well and the most compact cab. The W gives you the same extension as a similar depth H baffle. Then you can always pick up more extension with the Wbaffle layout by turning it into a U baffle by adding 50% more depth (only at the back) and pick up 6db of max output at the bottom.

If you go with a 2 driver U or H, build it just large enough for the drivers to fit on the baffle. Anything more is a waste of wood and will lower the frequency where resonances can occur due to the parallel surfaces. Also, plan on laying them on their side because you will get more bass that way due to the increased infinite baffle effect of the floor.

[DougL]

do you mean that with 2 drivers and a 100Hz xo point I might be better off with one W-frame than 2 separate U- or H-frames?

Yes. For all the reasons that johninCR stated.

If building the sub in the house is an option, check out this site:
Cult of the Infinitely Baffled

Doug

[Arctophile]

Thanks guys, more reading to do

Does this statement:

"For an IB, the Qtc of the system is approximately the Qts of the driver. If you like very tight bass, chose a lower Qts driver. If you like the "HT" sound, then chose a driver with a higher Qts."

...hold true for dipole woofers? There is another driver I can get for the same price called an MTX RT12-04, with following params:

Fs: 31.3Hz
Xmax: 8.13mm
Qts: 0.502
Sens: 93.5dB

Obviously the output would be greatly reduced, but is it likely to have much better transient response? It also has a nicer spider design:


Given that quality and integration with the main panels is my main concern rather than SPL, which should I choose?

//Adam F