compact OB sub - suitable 8-10" drivers?

[Bill poster]

I want to make a pair of small Infinite baffle subs to complement a full range design, therefore they don't need to be that powerful/loud, I just want to add clean bass extension at moderate listening levels.

I was thinking to mount each driver in a short fat tube/circular section about 25 cms long, firing sideways ( or firing downwards?).

What are suitable-for-IB, 8 or 10" woofers/subwoofers? I don't want to spend much. I live in the UK so I'm looking at brands such as Peerless, Monacor, Visaton, Seas etc.

[djn]

Sounds like you are talking about OB (open baffle) vs IB (infinate baffle) The IB would be mounted in the floor, ceiling, or wall and totally blocked from your listening room on the back side.

If you want good OBs, look at Martin Kings paper on OB, "U" frames, or "H" frames. I had a pair of the "H" frames and they rock and DO NOT break the bank.

[chris661]

Sounds like he means a sealed cabinet. There's some people calling sealed cabinets infinite baffle (some speaker manufacturers), when the two are only similar in that they stop the rear wave interfering with the output.
It is a pet niggle of mine, when people say IB meaning sealed.

For a sealed design, you're looking for a Qts of >0.5, but less than ~0.8. The former will give a smaller cabinet, but not as much bass extension. A higher Q needs a larger cabinet, but will give some more extension.

I'd consider being more flexible by adding the option of eq (in the form of a Linkwitz Transform): that way, you have control over how much extension (and excursion) you use, rather than it being governed by the driver and cabinet choice.

Chris

[Bill poster]

Yes, sorry I've got that completely wrong, I mean open baffle - I guess I'm making a circular form of H frame.

So far I found these drivers might be suitable

Visaton GF200 8" (wired up in 4ohms) very good performance but expensive.
Dayton SD270-88 10" high sensitivity might be an advantage when matching
Monacor SPH-250KE 10" good performance but small xmax..
Monacor SPW -226/8 8" ok performance and V cheap! £19 in uk!

[djn]

I did not know that Chris. I does make sense though.

[djn]

Originally Posted by Bill poster

Yes, sorry I've got that completely wrong, I mean open baffle - I guess I'm making a circular form of H frame.

So far I found these drivers might be suitable

Visaton GF200 8" (wired up in 4ohms) very good performance but expensive.
Dayton SD270-88 10" high sensitivity might be an advantage when matching
Monacor SPH-250KE 10" good performance but small xmax..
Monacor SPW -226/8 8" ok performance and V cheap! £19 in uk!

You might want to read through this article. I had the Emenence Alpha 15a in the "H" frame and they just amazed me.....and the drivers and boxes cost just over $100 for all. I had the woofer amps already.

http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf

.

[Bill poster]

Originally Posted by djn

You might want to read through this article. I had the Emenence Alpha 15a in the "H" frame and they just amazed me.....and the drivers and boxes cost just over $100 for all. I had the woofer amps already.

http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf

.

The drivers have to be 8 or 10".Thanks for the tip, I starting reading through

quote from Martin King

"A search of the Internet will reveal that there are a number of commercially
available open baffle, hence forth abbreviated as OB, dipole speaker systems available
in the audio marketplace. Offerings such as Seigfried Linkwitz’s Orion(1), John Kreskovsky’s NAO(2), and Paul Hilgeman’s Ronin(3)can all be characterized as floor standing narrow baffle dipole speaker systems. Each features active crossovers and EQ filters requiring at least two amplifiers. These are all very sophisticated well engineered designs that allow the use of a narrow baffle while still producing satisfying bass output. The key to these designs is the use of active crossovers and EQ filters to produce sufficient low frequency output. "

Well this is interesting; I'm using 2 full range drivers which will be around 87 db each.
Yesterday I was looking at the cheap Monacor and Dayton which have high sensitivity 91/92 dB. I thought if I use a suitable low pass, I can 'manipulate' a flatter bass frequency response overall. Then late last night I read a review of the Jamo 909's and they have done exactly this.

[tinitus]

Originally Posted by Bill poster

Yes, sorry I've got that completely wrong, I mean open baffle - I guess I'm making a circular form of H frame.

thread title corrected


moderation

[tinitus]

Originally Posted by Bill poster

So far I found these drivers might be suitable

Visaton GF200 8" (wired up in 4ohms) very good performance but expensive.
Dayton SD270-88 10" high sensitivity might be an advantage when matching
Monacor SPH-250KE 10" good performance but small xmax..
Monacor SPW -226/8 8" ok performance and V cheap! £19 in uk!

SPH-10M
new 10" Monacor
not really cheap, or impressive specs

Impedance (Z) 8Ω
Resonant frequency (fs) 29Hz
Max. frequency range f3-2,000Hz
Music power 200WMAX
Power rating (P) 120WRMS
SPL (1W/1m) 89dB
Suspension compl. (Cms) 0.41mm/N
Moving mass (Mms) 69g
Mech. Q factor (Qms) 2.62
Electr. Q factor (Qes) 0.60
Total Q factor (Qts) 0.49
Equivalent volume (Vas) 73.5 l
DC resistance (Re) 6.5Ω
Force factor (BxL) 11.5Tm
Voice coil induct. (Le) 1.1mH
Voice coil diameter Ø 50mm
Voice coil former aluminium
Linear excursion (XMAX) ± 6.25mm
Eff. cone area (Sd) 363cm2
Magnet weight 1.1kg
Weight 3.85kg

[Bill poster]

Thanks Tinitus, sparing my blushes. That driver does look good on the graph.. will compare with the visaton.