B.Flat

I have been trying to use the WinISD programme to determine my port. As I have purchased a coupe of telescopic 120mm port tubes I can experiment up to a length of 280mm. By my calculations a port length of the max. 280mm would tune my 33litre (total volume) Deltalite II 2510 cab to around 55hz. Can anyone verify this for me? Also because of the limited box size I will have to rear mount them. As the box is mounted 15mm feet could I mount them underneath ? (or am I loosing my marbles?)

Hi Phil. The drivers are Deltalite 2510 II. Bill is correct on the info I have given so far, but on balance, I would like to go ahead and port the cab. I would be grateful if you could calculate the port for me. I have bought some reflex tubes 110mm internal dia. The chambers in the cab are 33ltr total without deduction for speaker or port. Once again I must thank you for the advice and assistance, I am trying to understand the physics but the old grey matter I finding it hard going !!

Hi Stevie, thank you for your thoughts. I would like to point out that the PB1 has HP & LP filters, both operating at 100hz to 5khz and with level controls, output to a stereo power amp. Does this in anyway modify your advice ?

What op.amp changes could I make to a YAMAHA PB1 to improve its performance ? All suggestions gratefully received !

Thanks again Bill, you are a star!

Thank you ikay and El jimbob for your replies,

Thanks again Bill, but tell me as the volume per chamber appears to be around double the Eminence advised max is this putting the speakers at risk or reducing their efficiency? And finally wlll a port not have any beneficial effect over 100hz? I appreciate the time you, Phil & Dan have taken to help me.

Thank you for your reply Phil. Unfortunately I am the wrong side of 75, have no workshop facilities and little disposable income! I was given the cab to supplement a 1 X15". I have an old YAMAHA pb1 preamp which has bi-amp outputs. I was hoping to use the 2 X 10" as a mid/high box. I thought putting vents in it would improve its performance enough for this. Maybe crossed over at around 85 to100 Hz

Ok Bill, thank you again. As I cannot afford a new cab what is the very best I could do with what I have, with no high expectations?

In the absence of any replies does anyone want to make an educated guess ?

Hi. Thank you Bill, Phil & Dan. Advice taken on board. To answer your question Phil I have a sealed 2 X 10" Deltalite 2510 cab, the drivers are in separate chambers but at 33 ltrs total volume per chamber this is not good. Using some internet info I calculated one 100mm dia port between 116 & 125mm long in each chamber. However I do not trust my own calculations! Since starting the thread I have realised smaller dia ports are not required as I can put them (10mm dia) in the back of the cab.

Hi. Can anyone tell me if I can convert a reflex port 102mm diameter, 242.5mm long to two smaller diameter ports no longer, and hopefully shorter, than the original spec? Would two 50mm ports of the same length be equivalent?

Has anyone experience of using the 2 band S'Ray preamp with a JB pickup, bridge position.? I am interested to know what the comparison would be with an MM pickup. Could 2 JB pickups b wired as a humbucker and used with the S'Ray pre?

Has anyone got an opinion on the boards shown on the links below? I appreciate that I would probably have to add speaker protection of some kind. [url="http://www.ebay.co.uk/itm/500W-65V-Amplifier-Dual-Voltage-PSU-Audio-AMP-Switching-Power-Supply-Board/352146243682?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649"]http://www.ebay.co.uk/itm/500W-65V-Amplifier-Dual-Voltage-PSU-Audio-AMP-Switching-Power-Supply-Board/352146243682?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649[/url] [url="http://www.ebay.co.uk/itm/IRS2092S-500W-Mono-Channel-Digital-Amplifier-Class-D-HIFI-Power-Amp-Board-D4M3/322543229944?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649"]http://www.ebay.co.uk/itm/IRS2092S-500W-Mono-Channel-Digital-Amplifier-Class-D-HIFI-Power-Amp-Board-D4M3/322543229944?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649[/url]

Sorry Deaddogbb, I am not in UK, I think that is a problem, I am in La Belle FRance

OK, all responders, I have been guilty of expecting you all to be mind-reading clairvoyants, apologies ! I thought (stupidly) less parameters would be less confusing. So the over all project is this. I have the 2 x 8" enclosure. There is compartment at the back (at pres. a leads and odds and sods store) approx. 35cms wide, 13cms high &15cms deep. It is into this space I am hoping to fit power amp of around 200-500watts @4 ohms, no eq. but may be a HPF. Why didn't I say that in the first place???? Can it be done ?

To clarify I am wanting a powered cab, not a stand alone amp. I have limited space to put it and using one side of a rackmount stereo amp will not fill the bill. I think the GK 200 MB might do, the Demeter would definitely be OK, but I is out of my price range

Thank you all responders. What I have not made clear by some of the responses is that size is crucial for me. A 19" rackmount will not do the job. The cab is 4 ohms, 2 x Eminence LA8-CNMB neos'. The Labgruppen looks good but I haven't checked out the price yet. Any more suggestions gratefully received. Brian

II have been looking (in vain)) to find a MONO amp of around 200+watts to drive a 2 X 8" mid/high box.I really need it to have a small chassis/footprint , not rackmount. [i]I[/i] know I am probably out of my tree but could power amp intended for in-car use be used or would the power supply be a problem? If not commercially available does anyone know of any kit builds which might do the job?

I have put it between the bass and the amp with the same result. I now have it in the FX loop, powered by psu plugged into the same wall socket as the amp and this works fine in the FX loop. I am mystified !!!

hi again ST. The meter shows 9.4 v. I have reversed the polarity on the DC socket jus to be sure result being the ZOOM will not power up at all. What I cannot understand is that the YAMAHA unit, also neg. centre, works fine and is wired exactly the same way. If I take the YAMAHA out of the circuit the ZOOM will still not work. Do you think the psu could be faulty?

Hi ST, thanks for your reply. I am a bit short of time to put the meter on but I will post what happens when I do. I have tried reversing the AC supply wirers in the psu but the same problem persists. I have mounted the DC female sockets to the chassis. These have three pins, I have used the centre tap and the sprung pin which contacts the body of the male plug. I have left the pins which are connected to the chassis (through the fixing) un-connected. Any comments on that? Thanks for taking the time to reply

Hi all. I have an annoying wiring problem I am hoping someone can explain. OK, I have an amp I use for practice. Because of its limited tonal capabilities I run a YAMAHA FX500 in the send and return loop. The unit is powered by a 12volt power supply, centre negative. All OK so far. I have now added a ZOOM B1on ((battery powered but able to be powered by a 9volt supply, centre negative) between the amp send and the FX5500 input. Still OK. To tidy up the wiring I decided to put the two power supplies into the amp cabinet, running from the amp side of the on/off switch. The polarities have been respected. Result ? The FX 500 works fine, no prob. But the ZOOM unit powers up ok until it is connected to the send/return circuit, when it turns itself off. I have reversed the polarity of the power cable but no go. I have tried all variations of signal path, but still no go. I feel it must be an earthing problem but my limited intelligence is preventing progress! It works fine on batteries but I CANNOT get it to work on the 9volt power supply when connected to the amp or the FX500. There must be some boffin out there who can help explain this to me (I hope!!!!)

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